CN105207486B - A kind of two-way resonance DC converter and its control method - Google Patents

Abstract

The invention discloses a kind of two-way resonance DC converter and its control method, the two-way resonance converter is made up of low-side power, high side power, the switching tube of low-pressure side first to fourth, the switching tube of high-pressure side first to fourth, the first and second resonant inductances, resonant capacitance, the first and second electric capacity and transformer；When energy is transmitted by the lateral high-pressure side of low pressure, the two-way resonance DC converter realizes Power Control by the phase shifting control of both sides switching tube；When energy is transmitted by high side to low side, the two-way resonance DC converter realizes Power Control by the VFC of switching tube；Two-way resonance DC converter of the present invention can not only realize transmitted in both directions and the control of both sides energy, and the Sofe Switch of all switching devices can be realized in full-load range, be particularly suitable for high frequency, efficient, high power density bi-directional power conversion applications.

Description

A bidirectional resonant DC converter and its control method

technical field

The invention relates to a bidirectional resonant DC converter and a control method thereof, belonging to the technical field of power electronic converters, in particular to the technical field of bidirectional isolated DC-DC power conversion.

Background technique

Bidirectional DC converters can realize power transmission and control in two directions, and have the functions of two unidirectional DC converters. It has broad application prospects in power systems including energy storage links such as renewable energy power generation, electric vehicles, aerospace power supply, and smart grids.

In various energy storage systems, the voltage of the energy storage battery is usually very low, while the voltage on the other side (such as the DC bus side) is usually high. How to achieve high-efficiency bidirectional power conversion in the case of a large voltage difference between the two sides is Important issues of domestic and foreign industry and academia. Using an isolated bidirectional DC converter is a better solution. By adjusting the turn ratio of the high-frequency transformer, it is very easy to achieve voltage matching between the high-voltage side and the low-voltage side. However, due to problems such as hard switching, high voltage stress, and large switching loss, the existing isolated bidirectional DC converters cannot meet the application requirements well.

Generally speaking, a corresponding type of isolated bidirectional DC converter can be obtained by replacing the rectifier diode in the isolated unidirectional DC converter with a current bidirectional switching device. For example, the corresponding bidirectional push-pull, half-bridge, and full-bridge converters can be obtained by using isolated unidirectional push-pull, half-bridge, and full-bridge converters. However, this type of bidirectional converter is rarely used in practical systems. The main problem is that when the energy is transmitted in the reverse direction, the switching devices will generate very high voltage spikes due to the influence of transformer leakage inductance, which seriously affects system performance. In order to overcome these shortcomings, it is usually necessary to introduce a complex voltage clamping circuit or use a very complex control algorithm, which not only increases the system cost, but also reduces the system reliability. Dual active bridge bidirectional DC converter is an isolated bidirectional DC converter that has received extensive attention and research in recent years. It has overcome the problem of high voltage stress of traditional bidirectional DC converters, and all switch tubes have Soft switching capability. However, the shortcomings of the dual active bridge bidirectional DC converter itself, such as large turn-off loss and small soft switching range, have not been effectively resolved so far.

The isolated resonant DC converter is a type of circuit structure that has been developed rapidly in recent years. It has outstanding advantages such as low turn-off loss, excellent soft switching performance, suitable for high-frequency operation, and easy for integrated design. However, existing resonant DC converters are usually only suitable for unidirectional power transfer applications, and it is difficult to achieve bidirectional power transfer. Taking the bidirectional LLC resonant converter as an example, since its resonant cavity can only be placed on one side of the circuit, when the energy is transmitted from the side of the resonant cavity to the side that does not contain the resonant cavity, the working principle and process of the circuit are the same as those of the unidirectional The LLC resonant converter is the same and can achieve high-efficiency energy transfer; however, when the energy is transferred from the side that does not contain the resonant cavity to the side that contains the resonant cavity, the circuit structure will behave as a traditional series resonant converter. At this time, the circuit It can only work with step-down and there is a large turn-off loss and circulation loss, and the circuit performance will be greatly affected.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a new high-performance bidirectional resonant DC converter and a control method for it that can realize soft switching of all switching devices in the full load range

A bidirectional resonant DC converter provided by the present invention includes a low-voltage side power supply U _L , a high-voltage side power supply U _H , a first switch tube S _L1 on a low-voltage side, a second switch tube S _L2 on a low-voltage side, and a third switch tube S on a low-voltage side. _L3 , the fourth switch tube S _L4 on the low-voltage side, the transformer T, the first switch tube _{SH1 on the high-voltage side, the second switch tube S H2 on} the high-voltage side, the third switch tube S _H3 on the high-voltage side, the fourth switch tube S _H4 on the high-voltage side, The first resonant inductor L _r1 , the second resonant inductor L _r2 , the resonant capacitor C _r , the first capacitor C ₁ and the second capacitor (C ₂ ), wherein the transformer T includes a first winding N ₁ and a second winding N ₂ ;

The positive pole of the low-voltage side power supply U _L is connected to the drain of the first low-voltage side switching tube S _L1 and the drain of the low-voltage side second switching tube S _L2 , and the negative pole of the low-voltage side power supply U _L is connected to the third low-voltage side switching tube The source of S _L3 and the source of the fourth switching tube S _L4 on the low-voltage side, the source of the first switching tube S _L1 on the low-voltage side is connected to the drain of the second switching tube S _L2 on the low-voltage side and the _first winding N1 of the transformer T The terminal with the same name, the source of the third switching tube S _L3 on the low-voltage side is connected to the drain of the fourth switching tube S _L4 on the low-voltage side and the non-identical terminal of the _first winding N1 of the transformer T;

The anode of the high-voltage side power supply _UH is connected to one end of the first capacitor _C1 and the drain of the first switch tube _SH1 on the high-voltage side, and the source of the first switch tube _SH1 on the high-voltage side is connected to the second switch tube on the high-voltage side. The drain of S _H2 , the drain of the third switch tube S _H3 on the high voltage side, one end of the second resonant inductance L _r2 and the same-named end of the second winding _N2 of the transformer T, and the non-identical end of the second winding _N2 of the transformer T are connected The other end of the second resonant inductance L _r2 and one end of the first resonant inductance L _r1 , the other end of the first resonant inductance L _r1 is connected to one end of the resonant capacitor C _r and the drain of the fourth switching tube _SH4 on the high voltage side, The source of the fourth switching tube _SH4 on the high-voltage side is connected to the source of the third switching tube _SH3 on the high-voltage side, and the other end of the resonant inductance C _r is connected to the other end of the first capacitor _C1 and one end of the _second capacitor C2 , the other end of the _second capacitor C2 is connected to the source of the second switching transistor _SH2 on the high-voltage side and the negative electrode of the power supply _UH on the high-voltage side.

Further, the first resonant inductance L _r1 is replaced by the magnetizing inductance of the transformer T.

Further, part or all of the second resonant inductance L _r2 is replaced by the leakage inductance of the transformer T.

A bidirectional resonant DC converter control method, the method is divided into two cases based on the bidirectional transmission of energy:

When energy is transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H , the first switching tube _SH1 on the high-voltage side and the second switching tube _SH2 on the high-voltage side are kept turned off, and the first to fourth switching tubes S _L1 on the low-voltage side S _L4 , the third switching tube _SH3 on the high-voltage side, and the fourth switching tube _SH4 on the high-voltage side work in the high-frequency switching state. All the switching tubes in the high-frequency switching state have the same switching frequency and the duty cycle is equal to 0.5. The first switching tube S _L1 on the low-voltage side is complementary to the second switching tube S _L2 on the low-voltage side, the third switching tube S _L3 on the low-voltage side is complementary to the fourth switching tube S _L4 on the low-voltage side, and the third switching tube S _H3 on the high-voltage side and The fourth switch tube S _H4 on the high-voltage side is complementary to conduction; by adjusting the phase shift angle between the first switch tube S _L1 on the low-voltage side and the third switch tube S _L3 on the low-voltage side, and the third switch tube S _L3 on the low-voltage side and The phase shift angle between the conduction moments of the third switching tube S _H3 on the high-voltage side realizes the control of the energy transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H and the voltage of the high-voltage side power supply U _H ;

When energy is transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L , the first switch tube S _L1 on the low-voltage side, the second switch tube S _L2 on the low-voltage side, the third switch tube S _L3 on the low-voltage side, and the fourth switch tube on the low-voltage side S _L4 , the third switching tube _SH3 on the high-voltage side, and the fourth switching tube _SH4 on the high-voltage side are all kept off, and only the first switching tube _SH1 on the high-voltage side and the second switching tube _SH2 on the high-voltage side are working in the switching state. The first switch tube S _H1 on the high-voltage side and the second switch tube S _H2 on the high-voltage side are complementary conduction and the duty cycle is equal to 0.5. By changing the switching frequency of the first switch tube S _H1 on the high-voltage side and the second switch tube S _H2 on the high-voltage side The method is used to control the power transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L or to control the voltage of the low-voltage side power supply U _L.

More specifically, when energy is transferred from the low-voltage side power supply U _L to the high-voltage side power supply U _H , the specific steps are as follows:

(1) When the transmission energy or the voltage of the high-voltage side power source U _H starts to increase from zero, first keep the third switch tube S _L3 on the low-voltage side and the third switch tube S _H3 on the high-voltage side to be turned on and off at the same time, by increasing the first The switching tube S _L1 lags behind the phase shift angle between the turn-off moments of the third switching tube S _L3 on the low-voltage side to increase the power transmitted to the high-voltage side power supply U _H or increase the voltage of the high-voltage side power supply U _H ;

(2) When the phase shift angle between the first switching tube S _L1 on the low-voltage side and the third switching tube S _L3 on the low-voltage side reaches a maximum of 180°, if it is still necessary to increase the power transmitted to the high-voltage side U _H or Increase the voltage of the high-voltage side power supply U _H , then keep the phase shift angle between the turn-off moment of the first switch tube S _L1 on the low-voltage side and the third switch tube S _L3 on the low-voltage side at a maximum of 180°, by increasing the third switch tube on the high-voltage side The conduction time of S _H3 lags behind the phase shift angle between the conduction times of the third switch tube S _L3 on the low-voltage side to increase the power transmitted to the high-voltage side U _H or increase the voltage of the high-voltage side power supply U _H ;

(3) When it is necessary to reduce the power transmitted to the high-voltage side power supply U _H or reduce the voltage of the high-voltage side power supply U _H , if the third switch tube S _L3 on the low-voltage side and the third switch tube S _H3 on the high-voltage side are turned on at the moment If the phase shift angle between them is greater than zero, first reduce the phase shift angle between the conduction moment of the third switch tube S _L3 and the third switch tube _SH3 on the high-voltage side and keep the first switch tube S _L1 on the low-voltage side and the low-voltage side The phase shift angle between the turn-off moments of the third switch S _L3 is a maximum of 180°, if the phase shift angle between the turn-on moments of the third switch S _L3 on the low-voltage side and the turn-on time of the third switch S _H3 on the high-voltage side has been reduced is zero, then the third switch tube S _L3 on the low-voltage side and the third switch tube _{S H3} on the high-voltage side are kept on and off at the same time _. The phase shift angle between the off moments can be used to reduce the power transmitted to the high voltage side U _H or reduce the voltage of the high voltage side power supply U _H.

More specifically, when energy is transferred from the high-voltage side power supply U _H to the low-voltage side power supply U _L , the specific steps are as follows: (1) When it is necessary to reduce the power transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L or When reducing the voltage of the low-voltage side power supply U _L , increase the switching frequency of the high-voltage side first switch tube _{SH1 and the high-voltage side second switch tube S H2 ;} (2) when it is necessary to increase the high-voltage side power supply U _H to the low-voltage side power supply U _L When the transmitted power is increased or the voltage of the low-voltage side power supply U _L is increased, the switching frequency of the first switching tube _SH1 on the high-voltage side and the second switching tube _SH2 on the high-voltage side is reduced.

Compared with the prior art, the present invention adopts the above technical scheme and has the following technical effects:

(1) It can realize bidirectional power transmission and control between the low-voltage side power supply and the high-voltage side power supply, and realize the functions of two unidirectional isolation converters through only one circuit;

(2) No matter in which direction the energy is transmitted, all switching devices can realize soft switching within the full load range, and the conversion efficiency is high;

(3) No matter which direction the energy is transmitted to, the bidirectional resonant DC converter of the present invention can realize the control of transmission power under any power supply voltage condition, that is, the bidirectional resonant DC converter of the present invention can adapt to the wide voltage range of the high-voltage side power supply and the low-voltage side power supply Application requirements with varying scope;

(4) The control is simple and easy to implement;

(5) The voltage of all switching tubes can be clamped naturally and the voltage stress is low.

Description of drawings

The present invention will be further described below in conjunction with accompanying drawing:

Accompanying drawing 1 is the circuit schematic diagram of bidirectional resonant DC converter of the present invention;

Accompanying drawing 2 is the equivalent circuit diagram when the energy of the bidirectional resonant DC converter of the present invention is transmitted from the low-voltage side power supply to the high-voltage side power supply;

Accompanying drawing 3 is the equivalent circuit diagram simplified when the energy of the bidirectional resonant DC converter of the present invention is transmitted from the low-voltage side power supply to the high-voltage side power supply;

Accompanying drawing 4 is the equivalent circuit diagram when energy is transmitted from the high-voltage side power supply to the low-voltage side power supply of the bidirectional resonant DC converter of the present invention;

Accompanying drawing 5 is the key waveform diagram of the bidirectional resonant DC converter of the present invention when the energy is transmitted from the low-voltage side power supply to the high-voltage side power supply and works in working condition 1;

Accompanying drawing 6～accompanying drawing 10 are the equivalent circuit diagrams of each switching mode when the bidirectional resonant DC converter of the present invention transmits energy from the low-voltage side power supply to the high-voltage side power supply and works in working condition 1;

Accompanying drawing 11 is the key waveform diagram when the bidirectional resonant DC converter of the present invention transmits energy from the low-voltage side power supply to the high-voltage side power supply and works in working condition 2;

Accompanying drawing 12～accompanying drawing 15 are the equivalent circuit diagrams of each switch mode when the bidirectional resonant DC converter of the present invention transmits energy from the low-voltage side power supply to the high-voltage side power supply and works in working condition 2;

The symbol names in the above drawings: U _L is the low-voltage side power supply; U _H is the high-voltage side power supply; S _L1 , S _L2 , S _L3 and S _L4 are the first, second, third and fourth switching tubes on the low-voltage side respectively ; S _H1 , S _H2 , S _H3 and S _H4 are the first, second, third and fourth switch tubes on the high voltage side respectively; L _r1 and L _r2 are the first and second resonant inductance respectively; T is the transformer; N ₁ and N ₂ are the first and second windings of the transformer (T) respectively; C _r is the resonant capacitor; C ₁ and C ₂ are the first and second capacitors respectively; u _N1 is the first winding (N) of the transformer (T) ₁ ) The voltage between the end with the same name and the end with the same name; i _Lr1 and i _Lr2 are the currents of the first and second resonant inductors respectively; u _Cr is the voltage at both ends of the resonant capacitor; t, t ₀ , t ₁ , t ₂ , t ₃ , t ₄ and t ₅ are times.

Detailed ways

The present invention provides a bidirectional resonant DC converter and its control method. In order to make the object, technical solution and effect of the present invention clearer and clearer, the present invention is further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific implementations described here are only used to explain the present invention, not to limit the present invention.

As shown in Figure 1, the bidirectional resonant DC converter consists of a low-voltage side power supply U _L , a high-voltage side power supply U _H , a first switch tube S _L1 on the low-voltage side, a second switch tube S _L2 on the low-voltage side, and a third switch tube on the low-voltage side. Tube S _L3 , the fourth switch tube S _L4 on the low-voltage side, the transformer T, the first switch tube S _H1 on the high-voltage side, the second switch tube S _H2 on the high-voltage side, the third switch tube S _H3 on the high-voltage side, and the fourth switch tube S on the high-voltage side _H4 , the first resonant inductor L _r1 , the second resonant inductor L _r2 , the resonant capacitor C _r , the first capacitor C ₁ and the second capacitor C ₂ , wherein the transformer T includes the first winding N ₁ and the second winding N ₂ . Wherein: the positive pole of the low-voltage side power supply U _L is connected to the drain of the first switching tube S _L1 on the low-voltage side and the drain of the second switching tube S _L2 on the low-voltage side, and the negative pole of the low-voltage side power supply U _L is connected to the third switching tube on the low-voltage side. The source of the switching tube S _L3 and the source of the fourth switching tube S _L4 on the low-voltage side, the source of the first switching tube S _L1 on the low-voltage side is connected to the drain of the second switching tube S _L2 on the low-voltage side and the first winding of the transformer T _The terminal with the same name of N1, the source of the third switching tube S _L3 on the low-voltage side is connected to the drain of the fourth switching tube S _L4 on the low-voltage side and the non-identical terminal of the _first winding N1 of the transformer T, the high-voltage side power supply U _H The anode of the first capacitor C1 is connected to _one end of the first capacitor C1 and the drain of the first switching tube _SH1 on the high-voltage side, and the source of the first switching tube _SH1 on the high-voltage side is connected to the drain of the second switching tube _SH2 on the high-voltage side. The drain of the third switching tube _SH3 on the side, one end of the second resonant inductance L _r2 and the same-named end of the second winding _N2 of the transformer T, and the non-identical end of the second winding _N2 of the transformer T are connected to the second resonant inductance L _r2 The other end of the first resonant inductor L _r1 and the other end of the first resonant inductor L _r1 are connected to one end of the resonant capacitor C _r and the drain of the fourth switching tube _SH4 on the high voltage side, and the fourth switching tube S on the high voltage side The source of _H4 is connected to the source of the third switching tube _SH3 on the high-voltage side, the other end of the resonant inductance C _r is connected to the other end of the first capacitor _C1 and one end of the _second capacitor C2, and the _second capacitor C2 The other end is connected to the source of the second switching tube _SH2 on the high-voltage side and the negative pole of the power supply _UH on the high-voltage side.

When the energy is transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H , in order to realize the control of the transmitted energy, the following control method is adopted: the first switch tube S _H1 on the high-voltage side and the second switch tube S _H2 on the high-voltage side are kept off, The first to fourth switch tubes S _L1 to S _L4 on the low-voltage side, the third switch tube _{SH3 on the high-voltage side, and the fourth switch tube S H4 on} the high-voltage side work in the high-frequency switching state, and all the switching tubes in the high-frequency switching state have the same The switching frequency and the duty cycle are both equal to 0.5, the first switching tube S _L1 on the low-voltage side and the second switching tube S _L2 on the low-voltage side are complementary to conduction, and the third switching tube S _L3 on the low-voltage side is complementary to the fourth switching tube S _L4 on the low-voltage side. conduction, the third switch tube _SH3 on the high-voltage _side and the fourth switch _{tube SH4} on the high-voltage side are complementary to conduction. The phase angle and the phase shift angle between the conduction moments of the third switch tube S _L3 on the low-voltage side and the third switch tube S _H3 on the high-voltage side realize the energy transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H and the high-voltage side power supply U _H voltage control. At this time, the equivalent circuit of the bidirectional resonant DC converter of the present invention is shown in FIG. 2 . It can be seen from FIG. 2 that at this time, the body diodes of the first high-voltage side switch _SH1 and the high-voltage side second switch _SH2 are used to realize rectification.

When the energy is transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H , in order to realize the control of the transmitted energy, there are two situations when implementing a specific control method.

Working situation 1: When the voltage of the high-voltage side power supply U _H and the voltage of the low-voltage side power supply U _L satisfy the relationship "N ₁ U _H ≤ N ₂ U _L ", the following control method is adopted: keep the third switching tube S _L3 on the low-voltage side and the high-voltage side The third switch tube S _H3 is turned on and off at the same time, and the phase shift angle between the time when the first switch tube S _L1 lags behind the turn-off time of the third switch tube S _L3 on the low-voltage side is increased to increase the input to the high-voltage side power supply U _H The transmitted power or the voltage of the high-voltage side power supply U _H is increased, and the phase shift angle between the time when the first switch S _L1 lags behind the turn-off time of the third switch S _L3 on the low-voltage side is reduced to reduce the input to the high-voltage side U _H The transmitted power may reduce the voltage of the high-voltage side power supply (U _H ), that is, at this time, the control of the transmitted power is realized by adjusting the phase shift angle between the bridge arms of the low-voltage side switch. In fact, at this time, although the third switch tube _SH3 on the high voltage side and the fourth switch tube _SH4 on the high voltage side are both in the switching state, no current flows through these two switch tubes. Therefore, the equivalent circuit in this working situation can be further simplified as shown in FIG. 3 .

Working situation 2: When the voltages of the high-voltage side power supply U _H and the low-voltage side power supply U _L meet the relationship "N ₁ U _H > N ₂ U _L ", the following control method is adopted: keep the first switching tube S _L1 on the low-voltage side and the second switching tube on the low-voltage side The phase shift angle between the turn-off moments of the three switch tubes S _L3 is a maximum of 180°, and the phase shift between the turn-on moments of the third switch tube S _L3 on the low-voltage side is delayed by increasing the turn-on time of the third switch tube S _H3 on the high-voltage side Increase the power transmitted to the high-voltage side U _H or increase the voltage of the high-voltage side power supply U _H by reducing the phase shift between the conduction time of the third switching tube S _L3 and the third switching tube _SH3 on the high-voltage side angle to reduce the power transmitted to the high-voltage side U _H or reduce the voltage of the high-voltage side power supply U _H , that is, at this time, by adjusting the conduction of the third switch tube S _H3 on the high-voltage side and the conduction of the third switch tube S _L3 on the low-voltage side The control of the transmission power is realized by means of the phase shift angle between times.

When the energy is transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L , in order to realize the control of the transmitted energy, the following control methods are adopted:

The first switch tube S _L1 on the low-voltage side, the second switch tube S _L2 on the low-voltage side, the third switch tube S _L3 on the low-voltage side, the fourth switch tube S _L4 on the low-voltage side, the third switch tube S _H3 on the high-voltage side, and the fourth switch tube on the high-voltage side Both tubes _SH4 are kept off, and only the first switching tube _SH1 on the high-voltage side and the second switching tube _SH2 on the high-voltage side work in the switching state. At this time, the first switching tube _SH1 on the high-voltage side and the second switching tube _SH2 on the high-voltage side Complementary conduction and the duty cycle are equal to 0.5, by changing the switching frequency of the first switch tube S _H1 on the high-voltage side and the second switch tube S _H2 on the high-voltage side to control the transmission from the high-voltage side power supply U _H to the low-voltage side power supply U _L The specific steps are as follows: (1 ₎ When it is necessary to reduce the power transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L or reduce the voltage of the low-voltage side power supply U _L , Increase the switching frequency of the first switching tube S _H1 on the high-voltage side and the second switching tube S _H2 on the high-voltage side; (2) When it is necessary to increase the power transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L or increase the low-voltage side power supply U _L When the voltage is lower than 1, the switching frequency of the first switching tube _SH1 on the high-voltage side and the second switching tube _SH2 on the high-voltage side is reduced. In this working mode, the equivalent circuit of the bidirectional resonant DC converter is shown in Fig. 4 . It can be seen from FIG. 4 that at this time, the body diodes of the first to fourth switching transistors S _L1 to S _L4 on the low voltage side are used to realize rectification. As can be seen from accompanying drawing 4 and above-mentioned description, when energy is transmitted from high-voltage side power supply U _H to low-voltage side power supply U _L , the equivalent circuit, working principle and process of bidirectional resonant converter of the present invention are the same as half-bridge type LLC resonant DC converter exactly the same. Therefore, it is very easy to realize the soft switching operation of all switching tubes and all body diodes, and theoretically, the transmission power control can be realized under any voltage of the low voltage side power supply U _L and the high voltage side power supply U _H.

In actual implementation, except for the third switching tube _SH3 on the high-voltage side and the fourth switching tube _SH4 on the high-voltage side, a reasonable dead time needs to be set between all other switching tubes that work complementary to realize soft switching of each switching tube.

In actual implementation, all switching tubes should be semiconductor switching devices with parasitic body diodes, such as metal oxide semiconductor field effect transistors. If the selected switching tube does not have a parasitic body diode, antiparallel diodes should be connected across its drain and source.

Because when the energy is transmitted from the high-voltage side power supply U _H to the low-voltage side power supply U _L , the equivalent circuit, working principle and process of the bidirectional resonant converter of the present invention are exactly the same as those of the half-bridge LLC resonant DC converter, and will not be expanded here illustrate. In the following, only the working principle when the energy is transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H will be described. There are two working situations: "N ₁ U _H ≤ N ₂ U _L " and "N ₁ U _H ≥ N ₂ U _L ".

Hereinafter, the bidirectional resonant DC converter of the present invention is simply referred to as "converter".

When the energy is transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H and the converter works in working condition 1 of “N ₁ U _H ≤ N ₂ U _L ”, its main working waveform is shown in Fig. 5 . The converter has ten operating modes in each switching cycle. Since the working process of the positive and negative half cycles is similar, only the working process of half of the working cycle is analyzed.

Switching mode 1, [t ₀ -t ₁ ], the equivalent circuit is shown in Figure 6: before time t ₀ , the first switching tube S _L1 on the low-voltage side and the third switching tube S _L3 on the low-voltage side are turned on at the same time, and the second switching tube S L3 is turned on at the same time. The current of the first resonant inductor L _r1 is zero, the current i _Lr2 of the second resonant inductor L _r2 is negative, and i _Lr2 freewheels through the first winding N ₁ of the transformer T; at time t ₀ , the third switching tube S _L3 on the low-voltage side is turned off is turned off, and under the action of the second resonant inductor current i _L2 , the body diode of the fourth switching transistor S _L4 on the low voltage side is turned on.

Switching mode 2, [t ₁ -t ₂ ], the equivalent circuit is shown in Figure 7: at time t ₁ , the fourth switching tube S _L4 on the low voltage side is turned on with zero voltage, and in this mode, the second resonant inductance L _r1 Under the action of the low-voltage side power supply U _L , the current increases linearly from a negative value, and at the same time the first resonant inductance L _r1 resonates with the resonant capacitor C _r , the body diode of the first switch tube S _H1 on the high-voltage side is turned on, and the energy is supplied by the low-voltage side power supply U _L transmits to the high-voltage side power supply U _H.

Switching mode 3, [t ₂ -t ₃ ], the equivalent circuit is shown in Figure 8: at time t ₂ , the first switching tube S _L1 on the low-voltage side is turned off, and the volume of the second switching tube (S _L2 ) on the low-voltage side The diode conducts.

Switching mode 4, [t ₃ -t ₄ ], the equivalent circuit is shown in Figure 9: at time t ₃ , the second switching tube S _L2 on the low voltage side is turned on with zero voltage. In this mode, the energy stored in the first resonant inductor L _r1 continues to be transmitted to the high-voltage side power supply U _H until the current i _Lr1 of the first resonant inductor decreases to zero.

Switching mode 5, [t ₅ -t ₆ ], the equivalent circuit is shown in Figure 10: at time t ₅ , the current i _Lr1 of the first resonant inductor decreases to zero, and the volume of the first switching tube _SH1 on the high-voltage side The diode is turned off with zero current. At this time, the current i _Lr2 of the second resonant inductor L _r2 remains unchanged, and is carried out through the first winding N ₁ of the transformer T, the second switching tube S _L2 on the low-voltage side, and the fourth switching tube S _L4 on the low-voltage side. freewheeling. _At time t6, the fourth switching tube S _L4 on the low-voltage side is turned off, and the second half of the switching cycle begins.

Through the analysis of the above working process, it can be seen that all the switching tubes and diodes can realize soft switching. At the same time, the power transmission from the low-voltage side power supply U _L to the high-voltage side power supply U _H mainly occurs in the switching mode 2, that is, the amount of transmitted energy can be controlled by changing the duration of the switching mode 2.

When the energy is transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H and the converter works in the second working condition of "N ₁ U _H > N ₂ U _L ", its main working waveform is shown in Figure 11. There are four switching modes in one switching cycle.

Switching mode 1[t ₀ ,t ₁ ], the equivalent circuit is shown in Figure 12: before time t ₀ , the second switch tube S _L2 on the low-voltage side, the third switch tube S _L3 on the low-voltage side, and the third switch tube on the high-voltage side The tube _SH3 is turned on, but the current in the third switch tube _{SH3 on the high-voltage side is zero, the current of the first resonant inductor L r1 is} also zero, the body diodes of each switch tube are all turned off, and the current of the second resonant inductor L _r2 The current i _Lr2 is negative and increases linearly under the action of the low-voltage side power supply; at time t ₀ , the second switching tube S _L2 on the low-voltage side and the third switching tube S _L3 on the low-voltage side are turned off, and the current i of the second resonant inductor L _{r2 Lr2} commutates to the body diodes of the first switch tube S _L1 on the low-voltage side and the fourth switch tube S _L4 on the low-voltage side, and the drain-source voltage drop of the first switch tube S _L1 on the low-voltage side and the fourth switch tube S _L4 on the low-voltage side is 0 , so the first switching tube S _L1 on the low-voltage side and the fourth switching tube S _L4 on the low-voltage side have the conditions for zero-voltage turn-on, and at the same time, the current i _Lr2 of the second resonant inductor L _r2 reverses under the action of the voltage of the low-voltage side power supply U _L decreases, the current i _Lr1 of the first resonant inductor L _r1 also increases linearly under the action of the input voltage.

Switching mode 2[t ₁ , t ₂ ], the equivalent circuit is shown in Figure 13: At time t ₁ , the first switching tube S _L1 on the low-voltage side and the fourth switching tube S _L4 on the low-voltage side are turned on at zero voltage, and the first resonance The currents of both the inductor L _r1 and the second resonant inductor L _r2 continue to increase, since the current flows through the body diode of the fourth switching tube _SH4 on the high-voltage side at this time, the drain-source voltage of the fourth switching tube _SH4 on the high-voltage side is zero, namely The fourth switching tube _SH4 on the high-voltage side meets the zero-voltage turn-on condition. It is worth noting that the longer the mode lasts, the greater the current of the first resonant inductor L _r1 , which directly determines the initial moment of resonance between the first resonant inductor L _r1 and the resonant capacitor C _r . The initial value of the inductor L _r1 current, which further determines the amount of energy transmitted from the low-voltage side power supply U _L to the high-voltage side power supply U _H during the resonance process, so by adjusting the time of the switching mode, the high-voltage side power supply U can be realized Adjustment of the _H voltage and the magnitude of the transmitted power.

Switching mode 3[t ₂ , t ₃ ], the equivalent circuit is shown in Figure 14: at time t ₂ , the third switch tube _SH3 on the high-voltage side is turned off, and the fourth switch tube _SH4 on the high-voltage side is turned on, but due to the high-voltage The third switching tube _SH3 on the high-voltage side is in the off state, no current flows through the fourth switching tube _SH4 on the high-voltage side, and the current of the resonant inductor is naturally commutated to the body diode of the first switching tube _SH1 on the high-voltage side, and the first resonance The inductor L _r1 starts to resonate with the resonant capacitor C _r , and the low-voltage side power supply U _L transmits energy to the load through the first resonant inductor L _r1 and the resonant capacitor C _r , until the moment _t3 , the current of the first resonant inductor (L _r1 ) naturally resonates to zero.

Switching mode 4[t ₃ , t ₄ ], the equivalent circuit is shown in Figure 15: at time t ₃ , the current of the first resonant inductor L _r1 naturally resonates to zero, and the diode of the first switching tube _SH1 on the high-voltage side naturally off, there is no reverse recovery loss. In this mode, the low-voltage side power supply U _L does not transmit energy to the high-voltage side power supply U _H , and only the second resonant inductor L _r2 increases linearly under the action of the voltage of the low-voltage side power supply U _L , which is the second switching tube S _L2 of the low-voltage side and the zero-voltage turn-on of the third switching tube S _L3 on the low-voltage side to create conditions.

Summarizing the above working process, we can see that all the switching tubes of the converter can realize zero-voltage turn-on, and the current of all diodes naturally decreases to 0 and increases naturally from 0, so there is no diode reverse recovery problem, that is, all The switching devices are all in the soft switching state, which can realize high-efficiency energy transmission.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (6)

1. A bidirectional resonant DC converter, characterized in that: The DC converter includes a low-voltage side power supply ( U _L ), a high-voltage side power supply ( U _H ), a first switch tube on the low-voltage side ( S _{L 1} ), a second switch tube on the low-voltage side ( S _{L 2} ), and a third switch tube on the low-voltage side. tube ( S _{L 3} ), the fourth switching tube ( S _{L 4} ) on the low-voltage side, the transformer ( T ), the first switching tube on the high-voltage side ( S _{H 1} ), the second switching tube on the high-voltage side ( S _{H 2} ), the high-voltage side The third switching tube ( SH ₃ ), the fourth switching tube ( SH ₄ ) on the high voltage side, the first resonant inductance ( L _{r 1} ), the second resonant inductance ( L _{r 2} ), the resonant capacitor ( C _r ), the first a capacitor ( C ₁ ) and a second capacitor ( C ₂ ), wherein the transformer ( T ) includes a first winding ( N ₁ ) and a second winding ( N ₂ ); The anode of the low-voltage side power supply (UL) is connected to the drain of the first switching tube ( S _{L 1} ) on the low-voltage side and the drain of the third switching tube ( S _{L 3} ) on the low-voltage side, and the low - voltage side power supply ( U _{L )} The cathode of the low-voltage side is connected to the source of the second switching tube ( S _{L 2} ) and the source of the fourth switching tube ( S _{L 4} ) on the low-voltage side, and the source of the first switching tube ( S _{L 1} ) on the low-voltage side is connected to The drain of the second switching tube ( S _{L 2} ) on the low-voltage side and the terminal with the same name of the first winding ( N ₁ ) of the transformer ( T ), the source of the third switching tube ( S _{L 3} ) on the low-voltage side is connected to the fourth switching tube ( S L 3 ) on the low-voltage side. The drain of the switch tube ( S _{L 4} ) and the non-identical terminal of the first winding ( N ₁ ) of the transformer ( T ); The anode of the high-voltage side power supply ( U _H ) is connected to one end of the first capacitor ( C ₁ ) and the drain of the first switch tube ( SH 1 ) on the high-voltage side, and the first switch tube ( S _{H 1 )} on the high-voltage side The source is connected to the drain of the second switching tube ( SH ₂ ) on the high voltage side, the drain of the third switching tube ( SH ₃ ) on the high voltage side, one end of the second resonant inductor ( L _{r 2} ) and the transformer ( T ) The same-named end of the second winding ( N ₂ ), the non-identical end of the second winding ( N ₂ ) of the transformer ( T ) is connected to the other end of the second resonant inductance ( L _{r 2} ) and the first resonant inductance ( L _{r 1} ) One end of the first resonant inductor ( L _{r 1} ) is connected to one end of the resonant capacitor ( C _r ) and the drain of the fourth switching tube ( SH ₄ ) on the high voltage side, and the fourth switching tube ( S _{H 4} ) The source is connected to the source of the third switching tube ( SH ₃ ) on the high voltage side, and the other end of the resonant inductor ( C _r ) is connected to the other end of the first capacitor ( C ₁ ) and the second capacitor ( C ₂ ), and the other end of the second capacitor ( C ₂ ) is connected to the source of the second switching tube ( SH ₂ ) on the high-voltage side and the negative pole of the power supply ( U _H ) on the high-voltage side. 2. A bidirectional resonant DC converter according to claim 1, characterized in that: the first resonant inductance ( L _{r 1} ) is replaced by the magnetizing inductance of the transformer ( T ). 3. A bidirectional resonant DC converter according to claim 1, characterized in that: part or all of the second resonant inductance ( L _{r 2} ) is replaced by the leakage inductance of the transformer ( T ). 4. A bidirectional resonant DC converter control method, characterized in that: When the energy is transferred from the low-voltage side power supply ( U _L ) to the high-voltage side power supply ( U _H ), the high-voltage side first switch tube ( S _{H 1} ) and the high-voltage side second switch tube ( S _{H 2} ) are kept off, and the low-voltage side The first to fourth switch tubes ( S _{L 1} ~ S _{L 4} ), the third switch tube ( S _{H 3} ) on the high-voltage side and the fourth switch tube ( S _{H 4} ) on the high-voltage side work in a high-frequency switching state, and are in high-frequency All the switching tubes in the switching state have the same switching frequency and the duty cycle is equal to 0.5, the first switching tube ( S _{L 1} ) on the low-voltage side and the second switching tube ( S _{L 2} ) on the low-voltage side are complementary conduction, and the third switching tube ( S L 2 ) on the low-voltage side The switching tube ( S _{L 3} ) and the fourth switching tube ( S _{L 4} ) on the low-voltage side are turned on in a complementary manner, and the third switching tube ( S _{H 3} ) on the high-voltage side and the fourth switching tube ( S _{H 4} ) on the high-voltage side are turned on in a complementary manner; By adjusting the phase shift angle between the first switching tube ( S _{L 1} ) on the low-voltage side and the third switching tube ( S _{L 3} ) on the low-voltage side, and the third switching tube ( S L ₃ ) on the low-voltage side and the third switching tube on the high-voltage side The phase shift angle between the conduction moments of the three switch tubes ( SH ₃ ) realizes the control of the energy transmitted from the low-voltage side power supply ( U _L ) to the high-voltage side power supply ( U _H ) and the voltage of the high-voltage side power supply ( U _H ); When the energy is transmitted from the high-voltage side power supply ( U _H ) to the low-voltage side power supply ( U _L ), the first switch tube ( S _{L 1} ) on the low-voltage side, the second switch tube ( S _{L 2} ) on the low-voltage side, and the third switch tube on the low-voltage side tube ( S _{L 3} ), the fourth switch tube ( S _{L 4} ) on the low-voltage side, the third switch tube ( S _{H 3} ) on the high-voltage side and the fourth switch tube ( S _{H 4} ) on the high-voltage side are kept off, and only the high-voltage side The first switching tube ( S _{H 1} ) and the second switching tube ( S _{H 2} ) on the high-voltage side work in the switching state. At this time, the first switching tube ( S _{H 1} ) on the high-voltage side and the second switching tube ( S _{H 2} ) on the high-voltage side ) complementary conduction and the duty cycle is equal to 0.5, by changing the switching frequency of the first high-voltage side switch tube ( S _{H 1} ) and the high-voltage side second switch tube ( S _{H 2} ) to control the high-voltage side power supply ( U _H ) to transmit power to the low-voltage side power supply ( UL ₎ or to control the voltage of the low-voltage side power supply ( UL ₎ . 5. A bidirectional resonant DC converter control method according to claim 4, characterized in that: When the energy is transferred from the low-voltage side power supply ( U _L ) to the high-voltage side power supply ( U _H ), the specific steps are as follows: 1) When transmitting energy or the voltage of the high-voltage side power supply ( U _H ) increases from zero, first keep the third switch tube ( S _{L 3} ) on the low-voltage side and the third switch tube ( S _{H 3} ) on the high-voltage side turned on at the same time, and at the same time Turn off, increase the power transmitted to the high-voltage side power supply ( U _H ) by increasing the phase shift angle between the time when the first switch tube ( S _{L 1} ) lags behind the turn-off time of the third switch tube ( S _{L 3} ) on the low-voltage side Or increase the voltage of the high-voltage side power supply ( U _H ); 2) When the phase shift angle between the first switching tube ( S _{L 1} ) on the low-voltage side and the third switching tube ( S _{L 3} ) on the low-voltage side reaches a maximum of 180°, if it is still necessary to increase the phase shift angle to the high-voltage side ( U _H ) or increase the voltage of the high-voltage side power supply ( U _H ), then keep the shift between the turn-off time of the first switch tube ( S _{L 1} ) on the low-voltage side and the third switch tube ( S _{L 3} ) on the low-voltage side The phase angle is a maximum of 180°, and the phase shift angle between the conduction time of the third switch tube ( SH 3 ) on the high-voltage side lagging behind the conduction time of the third switch tube (S _L 3 ₎ on the low-voltage side is increased to increase the phase angle. The power transmitted by the high-voltage side ( U _H ) or the voltage of the high-voltage side power supply ( U _H ) increased; 3) When it is necessary to reduce the power transmitted to the high-voltage side power supply ( U _H ) or reduce the voltage of the high-voltage side power supply ( U _H ), if the third switch tube ( S _{L 3} ) on the low-voltage side and the third switch tube on the high-voltage side If the phase shift angle between the conduction moments of the third switch ( SH ₃ ) is greater than zero, firstly reduce the shift between the conduction moments of the third switch ( S _{L 3} ) and the third switch on the high-voltage side ( SH ₃ ). phase angle and keep the phase shift angle between the first switching tube ( S _{L 1} ) on the low-voltage side and the third switching tube ( S _{L 3} ) on the low-voltage side at a maximum of 180°, if the third switching tube ( S L 3 ) on the low-voltage side The phase shift angle between _{L 3} ) and the conduction moment of the third switching tube ( SH 3 ) on the high-voltage side has been reduced to zero, then the third switching tube (S _L 3 ₎ on the low-voltage side and the third switching tube on the high-voltage side are kept ( SH ₃ ) are turned on and off at the same time, and the phase shift angle between the first switch tube ( S _{L 1} ) lagging behind the turn-off time of the third switch tube ( S _{L 3} ) on the low-voltage side is reduced to reduce The power transmitted to the high-voltage side ( U _H ) or the voltage of the high-voltage side power supply ( U _H ) is reduced. 6. A bidirectional resonant DC converter control method according to claim 4, characterized in that: When the energy is transferred from the high-voltage side power supply ( U _H ) to the low-voltage side power supply ( U _L ), the specific steps are as follows: 1) When it is necessary to reduce the energy transmitted from the high-voltage side power supply ( U _H ) to the low-voltage side power supply ( U _L ) When increasing the power or reducing the voltage of the low-voltage side power supply ( UL ₎ , increase the switching frequency of the first switching tube ( SH ₁ ) on the high-voltage side and the second switching tube ( SH ₂ ) on the high-voltage side; 2) When it is necessary to increase the switching frequency of the high-voltage side When the power transmitted from the power supply ( U _H ) to the low-voltage side power supply ( U _L ) or the voltage of the low-voltage side power supply ( U _L ) is increased, the first switching tube ( S _{H 1} ) and the second switching tube on the high-voltage side are reduced ( S _{H 2} ) switching frequency.