CN100428621C - A brushless DC motor frequency conversion control device - Google Patents

Abstract

The invention discloses a frequency conversion control device for a brushless DC motor, comprising: a detection resistor connected in series on a DC bus; an intelligent frequency conversion module; and a control unit for receiving a bus current detection signal output by the detection resistor, and according to the bus current The detection signal and the switching logic state of the high-power electronic switching device in the intelligent frequency conversion module are calculated to obtain the three-phase input current of the brushless DC motor, and the rotor position is obtained according to the calculation of the three-phase input current of the brushless DC motor, and according to The rotor position and the expected motor speed generate and output switching signals for controlling the high-power electronic switching devices of the intelligent frequency conversion module; the control unit includes a current detection and analysis unit and a calculation control unit. This control method can make the motor obtain better speed regulation performance.

Description

A brushless DC motor frequency conversion control device

technical field

The invention relates to the technical field of frequency conversion, in particular to a frequency conversion control device for a brushless DC motor.

Background technique

About 50% of the world's electricity consumption is used for driving electric motors. Therefore, improving the efficiency of electric motor driving has become an important method of saving energy and is of great significance for building an energy-saving society.

In the motor drive technology, the common squirrel-cage AC motor has been widely used due to its simple structure. However, the control performance of this motor is poor, and it is difficult to obtain the required speed and torque. For example, the compressors of air conditioners and refrigerators driven by ordinary squirrel-cage alternating current cannot control the speed and torque of the motor, so the cooling capacity of the compressors is the same when they are working, and the cooling of the compressors cannot be adjusted according to the needs. Therefore, this kind of compressor adopts the method of motor interval work to obtain a suitable control temperature. The motor stops and starts repeatedly, causing problems such as large power consumption and unstable temperature, and the effect is not ideal.

Due to the above problems, the frequency conversion speed regulation technology for squirrel cage motors has been greatly developed. According to the characteristics of ordinary squirrel-cage AC motors, this technology adopts the method of changing the driving current frequency while maintaining a constant V/F to achieve speed control. However, because the armature current and the excitation current of the squirrel-cage AC motor are coupled, it is still impossible to achieve precise control. The vector control method is the most mature in the frequency conversion speed regulation technology used for frequency conversion speed regulation of squirrel cage motors at present. This method uses modern control theory to decouple the coupled armature current and excitation current in the AC motor through vector conversion to realize the speed control of the motor. However, this control method still cannot make the AC motor achieve the speed regulation performance of the DC motor, let alone accurately control the motor torque. In addition, this control method also has defects such as a narrow speed range. Moreover, the frequency conversion air conditioner using this technology cannot realize real stepless speed change at present, but can only realize variable speed regulation. To change the above-mentioned defects, only the AC motor with fundamental defects in control performance is no longer used, and the DC motor with good control characteristics is used instead.

Compared with AC motors, the armature current and excitation current of DC motors can be controlled independently of each other, and it is easy to obtain good speed regulation performance and torque control characteristics.

Due to the above reasons, the use of DC frequency conversion technology has gradually become popular in the fields of air conditioners and refrigerators. In Japan, by 2003, more than 95% of Japanese households used inverter air conditioners, and more than 95% of them were DC inverter air conditioners. In Europe, inverter air conditioners have been introduced since 1998, and DC inverters account for a considerable proportion. With the continuous improvement of European energy-saving standards for air conditioners in recent years, in 2004, the market share of inverter air conditioners in Europe reached more than 50%, of which 90% were DC inverter air conditioners. At present, China's inverter air conditioner market has fully entered the era of inverter air conditioner replacement. DC frequency conversion has quickly become the primary factor for Chinese consumers to choose air conditioners, and the market sales have shown multiple growth.

DC motors are divided into brushed DC motors and brushless DC motors. Brushed DC motors have problems such as difficult maintenance and short trouble-free time because the brushes are susceptible to wear. Therefore, brushless DC motors have been widely used.

The brushless DC motor adopts the permanent magnet rotor, which has no rotor current consumption in the three-phase AC asynchronous motor, has higher energy conversion efficiency, and has the remarkable characteristics of stable rotation, low noise and small size of the motor. It is currently the most energy-saving effect. good motor.

Unlike brushed DC motors, brushless DC motors have no brushes, and rely on detecting rotor position information to select the correct commutation sequence so that the stator of the motor always drives the rotor to rotate.

In general, sensors such as Hall elements are installed on the motor to detect the rotor position. However, for sealed brushless DC motors such as compressors, it is difficult to install position sensors. In this case, sensorless control of brushless DC motors is widely used.

In the currently used sensorless DC frequency conversion speed regulation technology, the zero-crossing detection method is used to judge the position of the rotor. This method selects the best commutation sequence by detecting the zero-crossing information of the non-conducting opposite potential and the commutation logic. Since the zero-crossing detection method can only detect some specific points, and as the motor speed changes in a wide range, the variable frequency of the back EMF will also change, and the filter device in the detection circuit will bring a certain phase shift, which will affect the detection process. The accuracy of the zero point; at the same time, the reverse current effect of the freewheeling diode on the power device will also have a certain impact on the detection of the zero point in the case of high current; more importantly, this detection method needs to be detected. conduction, so it can only be used in 120-degree frequency conversion mode, but not in 180-degree sine wave frequency conversion mode. Since the torque characteristic of the compressor changes sinusoidally, applying force to it according to the sinusoidal characteristic can make the added force fully used to drive the compressor, achieving the best efficiency of energy conversion. To achieve this requirement, 180-degree sine wave frequency conversion mode must be used. Therefore, the above-mentioned method of judging the position of the rotor by using zero-crossing detection can only be used in the 120-degree frequency conversion mode, and its application range is greatly hindered.

Contents of the invention

In view of the above-mentioned defects, the technical problem to be solved by the present invention is to provide a brushless DC motor frequency conversion control device, which does not require the motor to have a non-conducting phase for the detection of the rotor position, so that it can meet the 180-degree sinusoidal phase of the brushless DC motor. Wave frequency conversion needs.

The frequency conversion control device of the brushless DC motor provided by the present invention includes:

A detection resistor, which is connected in series with the DC bus, is used to obtain and output the bus current detection signal;

An intelligent frequency conversion module, the intelligent frequency conversion module includes an inverter composed of high-power electronic switching devices, the switching control pole of the high-power electronic switching device receives the control of the switching signal, and under the control of the switching signal, changes the switch Logical state, inverting the DC bus voltage into a three-phase drive current to drive the brushless DC motor to rotate;

The control unit is configured to receive the bus current detection signal output by the detection resistor, and calculate and obtain the three-phase input of the brushless DC motor according to the bus current detection signal and the switching logic state of the high-power electronic switching device in the intelligent frequency conversion module Current, calculate the rotor position according to the three-phase input current of the brushless DC motor, and generate and output the switching signal for controlling the high-power electronic switching device of the intelligent frequency conversion module according to the rotor position and the expected motor speed;

The control unit includes:

The current detection and analysis unit is used to receive the bus current detection signal output by the detection resistor, and calculate and obtain the three-phase current of the brushless DC motor according to the bus current detection signal and the switching logic state of the high-power electronic switching device in the intelligent frequency conversion module. Phase input current and output;

The calculation control unit is used to receive the three-phase input current of the brushless DC motor output by the current detection and analysis unit, and the expected speed of the brushless DC motor, and calculate the motor rotor according to the current value and the parameters of the brushless DC motor Combined with the desired rotational speed, a switching signal for controlling the high-power electronic switching device of the intelligent frequency conversion module is generated and output.

Preferably, the bus current detection signal output by the detection resistor is a voltage drop across the resistor, and the bus current is obtained through calculation based on the voltage drop and the resistance value of the detection resistor.

Preferably, the bus current detection signal obtained by the detection resistor is provided to the intelligent frequency conversion module for realizing overcurrent protection.

Preferably, the inverter of the intelligent frequency conversion module includes six high-power electronic switching devices, namely UP, UN, VP, VN, WP, and WN; wherein the anodes of UP, VP, and WP are connected to the positive pole of the DC bus , the cathodes are respectively connected to the brushless DC motor power lines U, V, W; the cathodes of UN), VN, WN are connected to the negative pole of the DC bus, and the anodes are respectively connected to the brushless DC motor power lines U, V, W.

Preferably, a diode is connected in reverse parallel between the anode and the cathode of the high-power electronic switching device.

Preferably, the bus current detection signal received by the current detection and analysis unit is the voltage drop across the detection resistor, and the bus current is calculated according to the voltage drop and the resistance value of the detection resistor; according to the bus current and the detected When the bus current is the switching logic state of each bridge of the inverter, the three-phase input current of the DC motor is calculated.

Preferably, the calculation control unit includes:

The 3/2 conversion module is used to receive the three-phase input current Iu, Iv, Iw of the brushless DC motor, and the rotor angle θ. The current in the three-phase coordinate system is transformed into the current values I γ and I δ in the two-phase stationary coordinate system of _γ and _δ , and output;

The speed position calculation module is used to obtain the angle error value Δθ of the rotor from the angle error calculation module, and calculate and output the rotor angle θ and the rotor feedback angular velocity ω according to the angle error value Δθ;

The angle error calculation module is used to receive the magnetic flux error Δλ output by the sensorless speed error calculation module, and the γ, δ coordinate system current I _γ and I _δ output by the 3/2 conversion module and the output of the speed position calculation module Rotor feedback angular velocity ω, calculate and obtain angle error value Δθ;

The sensorless speed error calculation module receives the d and q coordinate system voltages Vd and Vq output by the current calculation module, and the current I _γ and I _δ of the γ and δ coordinate systems output by the 3/2 conversion module and the speed position The rotor feedback angular velocity ω output by the calculation module is calculated to obtain the magnetic flux error Δλ output;

The speed control module is used to receive the feedback angular velocity ω output by the speed and position calculation module, and calculate the angular velocity ω ^* for the expected rotational speed of the motor, and obtain the calculated torque T ^* output through calculation;

The torque limiting module is used to receive the calculated torque T ^* output by the speed control module, and the feedback angular velocity ω output by the speed position calculation module, and obtain the current Id and Iq output in the d and q coordinate system through calculation;

The current calculation module is used to receive the d, q coordinate system current Id and Iq output by the torque limiting module, and the γ, δ coordinate system current I _γ and I _δ output by the 3/2 conversion module, and the speed The rotor feedback angular velocity ω output by the position calculation module outputs d, q coordinate system voltages Vd, Vq;

The 2/3 conversion module is used to receive the d, q coordinate system voltage output by the current calculation module, and the rotor angle θ output by the speed position calculation module, and generate a switch in the u, v, w three-phase coordinate system A control signal, the switch control signal is the switch signal for controlling the high-power electronic switch device of the intelligent frequency conversion module.

Preferably, the high-power electronic switching device is an insulated gate bipolar transistor (IGBT).

The DC motor frequency conversion control device provided by the present invention utilizes the inductance characteristics of the DC motor, uses a detection resistor to detect the DC side bus voltage, and calculates the brushless The three-phase input current of the DC motor. According to the three-phase current, the rotor position of the DC motor can be obtained by calculation. According to the rotor position, the switching logic state of the inverter of the intelligent frequency conversion module can be changed at an appropriate time, and the switching state of each bridge of the inverter can be changed to obtain a suitable The rotating magnetic field drives the rotation of the DC motor.

Compared with the prior art, the control method provided by the present invention does not need to detect the non-conducting phase to obtain rotor position information. Therefore, the 180-degree frequency conversion mode can be realized by adopting the control method, and the frequency conversion device can enable the motor to obtain better speed regulation performance and torque control characteristics.

Description of drawings

Fig. 1 is the schematic circuit diagram of the first embodiment of the present invention;

FIG. 2 is a timing schematic diagram of current detection in the first embodiment of the present invention;

FIG. 3 is a block diagram of the calculation control unit 22 according to the first embodiment of the present invention.

Detailed ways

Please refer to FIG. 1 , which is a schematic circuit diagram of the first embodiment of the present invention.

The circuit includes an intelligent frequency conversion unit (IPM) 1; a control unit 2; a brushless DC motor 3; a detection resistor 4.

The intelligent frequency conversion module 1 mainly includes an inverter composed of six high-power electronic switching devices, and the six high-power electronic switching devices include UP, UN, VP, VN, WP, and WN. Among them, the anodes of UP, VP, and WP are connected to the positive pole of the DC bus, and the cathodes are connected to the three-phase power input lines U, V, and W of the brushless DC motor; the cathodes of UN, VN, and WN are connected to the negative pole of the DC bus, and the anodes are respectively Connect the motor power lines U, V, W. Diodes are respectively connected in antiparallel between the anode and the cathode of the above-mentioned high-power electronic switching device, and the function of the diode is to provide a bypass for the reverse current and prevent the high-power electronic switching device from being broken down. The control electrode of the high-power electronic switching device receives a switching signal, and the switching state of the high-power electronic switching device can be changed by controlling the level of the switching signal to be high or low. The function of the intelligent frequency conversion module 1 is to convert the DC bus current into a drive current and provide it to the DC motor. The intelligent frequency conversion module 1 also includes a current protection sub-unit 11 for realizing over-current protection according to the result of current detection. The voltage of the direct current bus can be obtained by rectifying the alternating current. The high-power electronic device may be an insulated gate bipolar transistor IGBT.

The key to controlling a DC motor is that the commutation of the driving current must be performed in a timely manner, so that the motor can obtain an appropriate driving current at every moment and realize normal rotation. The appropriate driving current is obtained by controlling the switching state of the high-power electronic switching device by adding high and low level control signals to the control pole.

During the rotation of the motor, the switching states of the above-mentioned groups of high-power electronic devices need to be switched regularly, and the state of each high-power electronic switching device at each moment is called a switching logic state. The control of the brushless DC motor is actually to obtain a series of switching logic states that are switched in time.

The function of the control unit 2 is to control the switching state of the high-power electronic switching device in the intelligent frequency conversion module. It includes a current detection analysis unit 21 and a calculation control unit 22 . The control unit 2 outputs switching signals to the intelligent frequency conversion module 1 for controlling the switching states of high-power electronic devices in the intelligent frequency conversion module 1 .

Wherein, the function of the current detection analysis unit 21 is to receive the detection signal output by the detection resistor 4, and calculate the input current Iu, Iv, Iw of the three-phase input current Iu, Iv, Iw of the DC brushless motor U, V, W according to the detection signal and output. The principle and method of using the detection signal to calculate the three-phase input current are described later.

The calculation and control unit 22 receives the calculated values of the three-phase input currents Iu, Iv, and Iw output by the current detection and analysis unit 21, and calculates the angular velocity ω ^* . Among them, the calculated angular velocity ω ^* is the expected value of the rotational speed of the DC motor. The position of the motor rotor is calculated according to the calculated value of the three-phase input current and the parameters of the motor, and combined with the calculated angular velocity ω ^* to generate a switch signal, which is output to the intelligent frequency conversion module 1 .

The detection resistor 4 is connected in series in the DC bus to detect the current of the bus and transmit the detection signal to the current protection sub-unit 11 and the current detection and analysis unit 21 in the control unit 2 . The detection signal is the voltage drop across the detection resistor, and the current of the DC bus can be obtained according to the voltage drop and the resistance value of the detection resistor 4 . The detection resistor 4 can be integrated in the intelligent frequency conversion module 1 .

The key to realizing the control of the DC brushless motor is to obtain the rotor position information of the DC brushless motor, and perform commutation control according to the rotor position information. Obtaining the rotor position information in this embodiment includes the following steps:

Step 1. Obtain the DC bus current Idc according to the detection information output by the detection resistor 4 .

As shown in FIG. 1 , the detection resistor 4 is connected in series in the DC bus, and the current passing through the detection resistor 4 is the DC bus current Idc. The bus current Idc passes through the detection resistor 4 to generate a voltage drop Udc, and the detection information refers to the voltage drop Udc.

The current detection and analysis unit 21 digitizes the voltage Udc after receiving the detection information, that is, the voltage drop Udc across the detection resistor 4 , and calculates the DC bus current Idc according to the resistance value of the detection resistor 4 .

Step 2. Calculate and obtain the three-phase input currents Iu, Iv, and Iw of the brushless DC motor according to the DC bus current Idc.

Please refer to Figure 2. Fig. 2 shows the timing principle of current detection in the present invention.

In Fig. 2, the upper part is the switching status of the high-power electronic switching devices related to the three phases U, V and W, the middle part is the DC bus current value (Idc), and the lower part is the three-phase input current Iu, Iv, Iw.

Since the carrier frequency of pulse width modulation PWM is very high (8K Hz) in this invention scheme, and the load DC brushless motor has inductive characteristics, the current waveform on the AC side of the inverter is generally a sine wave, and within one carrier period Little change occurs. The waveform of Idc is obtained by switching the current on the AC side through the inverter composed of the high-power electronic switching devices of the intelligent frequency conversion module 1, and the switching logic states formed by the switching states of each high-power electronic switching device of the inverter In the method, the input current of each phase of the brushless finger current motor can be obtained according to the basic circuit step-by-step method. Take time ① and ② in Figure 2 as examples to illustrate the calculation method.

① interval (UP, VP, WN: conduction), so: □Idc①=-Iw

② interval (UP, VN, WN: conduction), so: □Idc②=Iu

Since the motor is inductive, the current cannot change suddenly. The time interval between interval ① and interval ② is very short, which can be regarded as the current value at the same time. Since the vector sum of Iu, Iv, and Iw is zero, that is: Iu+Iv+Iw=0

Therefore, Iu, Iv, and Iw can be simply calculated according to the following relationship:

Iu=Idc②, Iv=Idc①-Idc②, Iw=-Idc①

It should be emphasized that the above-mentioned assumption that the current values of interval 1 and interval 2 are the current values at the same time is the key to the calculation of the three-phase input current value of the brushless DC motor by using a detection resistor in the present invention. This assumption will cause There is a certain error, but in most cases the control requirements can be met. The above assumptions apply to all adjacent switch logic states.

According to the three-phase input current of the brushless DC motor obtained above, the rotor position information of the motor can be obtained. The principle is to use the following formula:

$\mathrm{<span\; class="notranslate">\; \&Delta;\&theta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; Im</span>}<span\; class="notranslate">\; \{</span>\frac{\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;\&lambda;</span>}<span\; class="notranslate">\; \}</span>$

ω＝-K _p Δθ-K _I Δθdt θ＝∫ωdt

In the above formula, θ is the rotor angle, that is, the rotor position information. The meaning and application of each symbol in the above formula will be explained in detail in Step 3 below.

Step 3. According to the three-phase input currents Iu, Iv, and Iw of the DC brushless motor, and in combination with the parameters of the motor and the logic state of the switching circuit of the high-power electronic switching device, output a control signal to control the power of the high-power electronic switching device. switch status. This process is completed in the computing control unit 22 in FIG. 1 .

Please refer to FIG. 3 , which shows a block diagram of the calculation control unit 22 .

Figure 3 shows that the calculation and control unit 22 receives the three-phase input currents Iu, Iv, Iw obtained through detection and calculation, and outputs switching signals Vup, Vvp, Vwp for controlling the high-power electronic switching devices of the intelligent control module , Vun, Vvn, Vwn.

The calculation and control unit 22 provides switching signals Vup, Vvp, Vwp, Vun, Vvn, Vwn to the intelligent frequency conversion module in the form of real-time feedback according to the current detection of the brushless DC motor. The switching signals Vup, Vvp, Vwp, Vun, Vvn, and Vwn change the energization and current flow direction of each phase of the motor stator according to the position of the motor rotor, and provide the rotor with a magnetic field that always drives it to move in a specified direction, so that the motor continues to rotate.

As shown in Figure 3, the calculation control unit 22 includes a 3/2 conversion module 221, a speed control module 222, a torque limit module 223, a current calculation module 224, a 2/3 conversion unit 225, a sensorless speed error calculation module 226, an angle Error calculation module 227, speed position calculation module 228.

The calculation control unit 22 uses the three-phase input currents Iu, Iv, and Iw to realize the control through three coordinate transformations.

The three-time coordinate transformation includes converting a three-phase coordinate system (u, v, w) into a two-phase stationary coordinate system (γ, δ), and converting from a two-phase stationary coordinate system (γ, δ) into a two-phase rotating coordinate system (d , q), from the two-phase rotating coordinate system (d, q) to the three-phase coordinate system (u, v, w), after the above-mentioned coordinate transformation, it is generated in the three-phase coordinate system (u, v, w) Switch control signals Vup, Vvp, Vwp, Vun, Vvn, Vwn are provided to the intelligent frequency conversion unit 1 .

The 3/2 conversion module 221 is used to receive the three-phase input current Iu, Iv, Iw of the brushless DC motor, and the rotor angle θ. The current in the system (u, v, w) is transformed into the current values I γ and I _δ of the two-phase stationary coordinate system ( _γ , δ) and output. The rotor angle θ has a certain value at startup, so that the 3/2 conversion module 221 can perform coordinate conversion calculation. After the motor starts to rotate, the value is calculated according to the rotation of the brushless DC motor, specifically from the speed and position calculation module 228. For the calculation method, see the description of the speed and position calculation module 228 later.

The speed position calculation module 228 obtains the rotor angle error value Δθ from the angle error calculation module 227 , and calculates the rotor angle θ and the rotor feedback angular velocity ω according to the angle error value Δθ. Its calculation formula is as follows:

ω＝-K _p Δθ-K _I Δθdt θ＝∫ωdt

In the formula: K _p and K _I are constants.

The rotor angle θ obtained by the above calculation, that is, the rotor position information, can decide when to commutate the inverter in the intelligent frequency conversion module 1, so as to obtain a suitable rotating magnetic field, so that the motor rotor can be stabilized RPM rotation.

The angle error calculation module 227 receives the magnetic flux error Δλ output by the sensorless speed error calculation module 226, and the current I _γ and I _δ of the (γ, δ) coordinate system output by the 3/2 conversion module and the The rotor feedback angular velocity ω output by the speed position calculation module 228 is the angular error value Δθ. This angular error value Δθ is set to zero when the motor is started. After the motor starts, it is calculated according to the detected value, and the calculation formula is as follows:

$\mathrm{<span\; class="notranslate">\; \&Delta;\&theta;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; q</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; i</span>}}_{\mathrm{<span\; class="notranslate">\; \&gamma;</span>}}<span\; class="notranslate">\; )</span>}\mathrm{<span\; class="notranslate">\; Im</span>}<span\; class="notranslate">\; \{</span>\frac{\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}{\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j\&omega;</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;\&lambda;</span>}<span\; class="notranslate">\; \}</span>$

The meaning of each symbol in this formula: φ _m : rotor magnetic flux; i _γ : γ-axis current; L _q : Q-axis inductance; L _d : D-axis inductance; p: differential operator; α: constant.

The sensorless speed error calculation module (ACFO Observer) 226 receives the (d, q) coordinate system voltages Vd, Vq output by the current calculation module 224, and the (γ, δ) coordinates output by the 3/2 conversion module 221 The current I _γ and I _δ of the system and the rotor feedback angular velocity ω output by the speed and position calculation module 228 are calculated to obtain the output of the magnetic flux error Δλ.

The speed control module 222 receives the feedback angular velocity ω output by the speed position calculation module 228 and the input calculated angular velocity ω ^* , and obtains the calculated torque T ^* output through calculation. The calculated angular velocity is the rotational speed at which the motor is expected to rotate, and the rotational speed is provided to the calculation control unit 22 as required. In a specific application, other units may provide the calculated angular velocity ω ^* to the calculation control unit 22 as required, or Artificial setting. This calculated angular velocity ω ^* is the desired rotational velocity of the motor.

The torque limiting module 223 receives the calculated torque T ^* output by the speed control module 222 and the feedback angular velocity ω output by the speed position calculation module 228, and obtains (d, q) coordinate system current Id, Iq output through calculation .

The current calculation module 224 receives the (d, q) coordinate system current Id, Iq output by the torque limiting module 223, and the (γ, δ) coordinate system current I _γ , I _δ , and the rotor feedback angular velocity ω output by the velocity position calculation module 228 , the output quantities are (d, q) coordinate system voltages (Vd, Vq).

The 2/3 conversion module 225 receives the (d, q) coordinate system voltage output by the current calculation module 224, and the rotor angle θ output by the speed position calculation module 228, which is generated in the three-phase coordinate system (u, q v, w) switch control signals Vup, Vvp, Vwp, Vun, Vvn, Vwn. The above-mentioned switch control signal is applied to the switch control terminal of the high-power electronic device in the intelligent frequency conversion module 1 to control the on-off of the high-power electronic device. The change of the switching state of the high-power electronic device forms the transition of the switching logic state of the inverter. The bus current is added to the three-phase power line of the DC motor through the above-mentioned inverter, and a rotating magnetic field suitable for the motor speed is generated on the stator to drive the rotor to rotate.

Each module of the above calculation control unit 22 forms a closed-loop feedback. According to the calculated value of the received three-phase input current Iu, Iv, Iw of the DC motor, combined with the expected rotational speed of the DC motor, that is, the calculated angular velocity ω ^* , the high-power electronic switch for the inverter of the intelligent frequency conversion unit 1 is obtained through calculation The switching signals Vup, Vvp, Vwp, Vun, Vvn, Vwn of the device finally control the motor to obtain the required speed. The calculation formulas involved in each of the above modules can be obtained under the existing known technology.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (8)

1, a kind of frequency-converting control device of brushless DC motor is characterized in that, comprising:

Detect resistance, this resistance string is associated on the dc bus, is used to obtain bus current detection signal and output;

Intelligent transducer module, this intelligent transducer module comprises the inverter of being made up of the high-power electronic switch device, the control of the switch control utmost point receiving key signal of described high-power electronic switch device, and under the control of described switching signal, changing the switching logic state, is the rotation of three-phase drive current drives brushless DC motor with the DC bus-bar voltage inversion;

Control unit, be used to receive the bus current detection signal of described detection resistance output, switching logic state according to high-power electronic switch device in this bus current detection signal and the described intelligent transducer module, calculate the three-phase input current that obtains brushless DC motor, calculate its rotor-position of acquisition according to the three-phase input current of this brushless DC motor, and produce the switching signal and the output of the high-power electronic switch device of control intelligent transducer module according to the motor speed of this rotor-position and expectation;

Described control unit comprises:

The current detecting analytic unit, be used to receive the bus current detection signal of described detection resistance output, according to the switching logic state of high-power electronic switch device in this bus current detection signal and the described intelligent transducer module, calculate the three-phase input current and the output that obtain brushless DC motor;

Calculation control unit, be used to receive the three-phase input current of the brushless DC motor of described current detecting analytic unit output, and to the expectation rotating speed of brushless DC motor, position according to the calculation of parameter motor rotor of described current value and brushless DC motor, and, produce the switching signal and the output of the high-power electronic switch device of control intelligent transducer module in conjunction with described expectation rotating speed.

2, frequency-converting control device according to claim 1 is characterized in that, the bus current detection signal of described detection resistance output is the voltage drop at these resistance two ends, calculates according to the resistance of this voltage drop and detection resistance and obtains bus current.

3, frequency-converting control device according to claim 1 is characterized in that, the bus current detection signal that described detection resistance obtains offers described intelligent transducer module, is used to realize overcurrent protection.

4, frequency-converting control device according to claim 1 is characterized in that, the inverter of described intelligent transducer module comprises six high-power electronic switch devices, is respectively UP, UN, VP, VN, WP, WN; Wherein the anode of UP, VP, WP connects the positive pole of described dc bus, and negative electrode connects brushless DC motor power line U, V, W respectively; The negative electrode of UN, VN, WN connects the negative pole of dc bus, and anode connects brushless DC motor power line U, V, W respectively.

5, frequency-converting control device according to claim 4 is characterized in that, reverse parallel connection diode between the anode of described high-power electronic switch device and the negative electrode.

6, frequency-converting control device according to claim 1, it is characterized in that, the described bus current detection signal that described current detecting analytic unit receives is the voltage drop at described detection resistance two ends, and the resistance according to this voltage drop and detection resistance calculates bus current; The switching logic state of each bridge of inverter calculates the three-phase input current that obtains DC motor according to bus current and when detecting this bus current.

7, frequency-converting control device according to claim 1 is characterized in that, described calculation control unit comprises:

3/2 modular converter, be used to receive described brushless DC motor three-phase input current Iu, Iv, Iw, and rotor angle, according to above-mentioned numerical value, by the conversion of three-phase, realize the electric current under u, v, w three phase coordinate systems is converted into the current value I of γ, δ two-phase rest frame to two-phase _γ, I _δ, and output;

The velocity location computing module is used for from the angular error value Δ θ of angular error computing module acquisition rotor, and calculates rotor angle and rotor feedback angular velocity omega and output according to this angular error value Δ θ;

The angular error computing module is used to receive the magnetic flux error delta λ of no transducer velocity error computing module output and γ, the δ coordinate system electric current I of described 3/2 modular converter output _γ, I _δWith the rotor feedback angular velocity omega of described velocity location computing module output, calculate and obtain angular error value Δ θ;

No transducer velocity error computing module, d, q coordinate system voltage Vd, the Vq of received current computing module output, and the γ of described 3/2 modular converter output, the electric current I of δ coordinate system _γ, I _δRotor feedback angular velocity omega with described velocity location computing module output obtains magnetic flux error delta λ output as calculated;

Rate control module is used to receive the feedback angular velocity omega of described velocity location computing module output, and to the expectation revolution speed calculating angular velocity omega of motor ^*, obtain factored moment T as calculated ^*Output;

The moment limiting module is used to receive the factored moment T that described rate control module is exported ^*, and the feedback angular velocity omega of described velocity location computing module output, obtain d, q coordinate system electric current I d, Iq output as calculated;

The electric current computing module is used to receive d, q coordinate system electric current I d, the Iq that described moment limiting module is exported, and the γ of described 3/2 modular converter output, δ coordinate system electric current I _γ, I _δAnd the rotor feedback angular velocity omega of described velocity location computing module output, output d, q coordinate system voltage Vd, Vq;

2/3 modular converter, be used to receive d, the q coordinate system voltage of described electric current computing module output, and the rotor angle of described velocity location computing module output, be created in the switch controlling signal under u, v, w three phase coordinate systems, this switch controlling signal is exactly the switching signal of the high-power electronic switch device of described control intelligent transducer module.

According to each described frequency-converting control device of claim 1 to 7, it is characterized in that 8, described high-power electronic switch device is an insulated gate bipolar transistor IGBT.

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