CN101951161B - Control system for suppressing current oscillation and distortion of three phase-single phase matrix converter - Google Patents

Abstract

The invention discloses a control system for suppressing current oscillation and distortion of a three-phase-single-phase matrix converter. The main circuit of the three-phase-single-phase matrix converter is composed of six bidirectional switches; The control system of matrix converter includes input voltage sampling unit, input and output overcurrent fault detection unit, TMS320LF2812 main controller, EPM1270 auxiliary controller and driving circuit. The present invention aims at the problems of input current oscillation and output current distortion when the three-phase-single-phase matrix converter based on the dual-voltage synthesis modulation strategy switches over the input sector, and adopts an improved dual-voltage synthesis modulation method that redistributes the trigger pulses, While ensuring that the output voltage is the expected voltage value, the input current oscillation and output current distortion are reduced.

Description

Control System for Suppressing Current Oscillation and Distortion of Three-phase-Single-phase Matrix Converter

technical field

The invention relates to a three-phase-single-phase matrix converter, especially for the occasion where the three-phase-single-phase matrix converter adopts a dual voltage synthesis modulation strategy to realize frequency conversion.

Background technique

Matrix Converter (Matrix Converter) was first proposed by Venturini and Alesina in 1980, followed by continuous research and improvement. However, due to the complexity of the matrix converter itself and the complexity of its control, it has not been widely used so far. With the continuous progress of technology, especially in recent years, due to the emergence of new power devices such as NIGBT, RB-IGBT, and the emergence of high-performance DSP control chips, the research of matrix converters has entered a new stage. Including bidirectional switch design, EMI issues and filter design, protection issues, etc. Among them, the commutation of two bidirectional switches is the most important problem, which is mostly solved by multi-step commutation at present. These advances will eventually make the matrix converter enter the field of practice.

With the increasing demand for single-phase variable frequency power supplies, three-phase-single-phase matrix converters have received attention, such as Y.Miura, s.Kokubo, D.Maekawa et al. in 2008 in the paper "Power Modulation Control of a Three- phase to Single-phaseMatrix Converter for a Gas Engine Cogeneration System.PESC, 2008" proposed to apply three-phase-single-phase matrix converter to small synchronous generator control system to improve system efficiency; and Somnida Ratanapanachote, Han JU Cha, PrasadN In the paper "A Digitally Controlled Switch Mode Power Supply Based on MatrixConverter.IEEE Transactions on Power Electronics, 2006", Enjeti et al. proposed to apply it to switching power supply to convert three-phase power frequency AC into single-phase high frequency Alternating current; also Mei Yang, Sun Kai, Zhou Daning and others proposed to apply it to the electric railway auxiliary system in the paper "Application of Matrix Converter in Auxiliary Drive System for Diesel Locomotives. Industry Application Conference, 2005" in 2005.

At present, the research on the three-phase-single-phase matrix converter mainly focuses on the topology and control strategy, and the three-phase-single-phase converter based on the dual-voltage synthesis modulation strategy has the ability to automatically suppress the unbalanced disturbance of the input voltage and the maximum linear voltage Transmission ratio and other advantages have received more attention. However, in the three-phase-single-phase matrix converter based on the dual-voltage synthesis modulation strategy, due to the fixed trigger pulse distribution method, the position of the input current pulse changes when the input sector is switched, and the phenomenon of input current oscillation occurs, reducing the This reduces the stability of the system, and causes distortion of the output side current, reducing the quality of the system output.

Contents of the invention

The present invention provides a control system for suppressing input current oscillation and output current distortion of a three-phase-single-phase matrix converter in order to avoid the disadvantages of the above-mentioned prior art. Input current oscillation and output current distortion of phase-to-single-phase matrix converter.

The present invention solves technical problem and adopts following technical scheme:

The present invention is used to suppress the control system of three-phase-single-phase matrix converter current oscillation and distortion, the main circuit of its three-phase-single-phase matrix converter is composed of six bidirectional switches; The control system of single-phase matrix converter includes input voltage sampling unit, input and output overcurrent fault detection unit, TMS320LF2812 main controller, EPM1270 auxiliary controller and driving circuit;

The input voltage sampling unit samples any two input line voltages and sends them to the TMS320LF2812 main controller to determine the sector to which the input voltage belongs;

The input and output overcurrent fault detection unit detects the overcurrent information of the instantaneous grid-side power supply and load, and sends it to the EPM1270 auxiliary controller, and at the same time sends it to the TMS320LF2812 main controller;

The TMS320LF2812 main controller sends the sector information of the input line voltage to the EPM1270 auxiliary controller in real time to judge the sector state of the input voltage; the three-phase-single-phase matrix is given in the TMS320LF2812 main controller The output voltage information of the converter, the sector to which the output voltage belongs is judged by the output voltage information, the duty ratio is obtained in real time by using the dual voltage synthesis method from the input voltage and the output voltage, and the duty ratio is determined according to the trigger pulse distribution method Make adjustments, output the adjusted duty cycle to the EPM1270 auxiliary controller, and send the output voltage sector and synchronization signal to the EPM1270 auxiliary controller at the same time;

The EPM1270 auxiliary controller decodes the input voltage sector, output voltage sector, duty cycle and synchronization signal output by the TMS320LF2812 main controller according to the trigger pulse distribution mode, so as to reduce the input current pulse position switching between sectors changes in the process;

The driving circuit is used for driving a bidirectional switch of a three-phase-single-phase matrix converter.

The trigger pulse distribution method is as follows: during the switching process of the input voltage sector, based on the principle that the change of the input current pulse position is the smallest, in different input voltage sectors, the maximum phase or the minimum phase of the input phase voltage is located in the middle of the switching cycle. The trigger pulse distribution method ensures that the position of the input current pulse remains unchanged during the sector switching process, thereby suppressing the oscillation of the input current and the distortion of the output current during the sector switching process.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. The present invention adopts a dual-voltage synthesis modulation method that adjusts the duty cycle in a trigger pulse distribution mode, which can reduce the input current of the three-phase-single-phase matrix converter in the sector while ensuring that the output voltage is the expected voltage value. Oscillation during switching increases system stability.

2. The present invention effectively reduces the output current distortion. Simulation and experiment results show that the output current THD can be reduced by 7.5% under the same load condition.

Description of drawings

Fig. 1 is the main circuit structural diagram of three-phase-single-phase matrix converter of the present invention;

Fig. 2 is the control system block diagram of three-phase-single-phase matrix converter of the present invention;

Fig. 3 is the sector division diagram of the input voltage of the present invention;

Fig. 4 is a trigger pulse distribution diagram of a three-phase-single-phase matrix converter in the prior art;

FIG. 5 is a distribution diagram of trigger pulses of a three-phase-single-phase matrix converter in the technology of the present invention.

The present invention will be further described below in conjunction with the accompanying drawings by way of specific embodiments:

Detailed ways

Referring to Fig. 1, in this embodiment, the main circuit of the three-phase-single-phase matrix converter is composed of six bidirectional switches (s _ap -s _cn );

Referring to Figure 2, the control system of the three-phase-single-phase matrix converter includes an input voltage sampling unit, an input and output overcurrent fault detection unit, a TMS320LF2812 main controller, an EPM1270 auxiliary controller and a driving circuit;

Use the input voltage sampling unit to sample any two input line voltages and send them to the TMS320LF2812 main controller to determine the sector to which the input voltage belongs;

Use the input and output overcurrent fault detection unit to detect the overcurrent information of the instantaneous grid-side power supply and load, and send it to the EPM1270 auxiliary controller, and at the same time send it to the TMS320LF2812 main controller;

The TMS320LF2812 main controller sends the sector information of the input line voltage to the EPM1270 auxiliary controller in real time to judge the sector status of the input voltage; the output of the three-phase-single-phase matrix converter is given in the TMS320LF2812 main controller Voltage information, the output voltage information is used to judge the sector to which the output voltage belongs, and the duty cycle is obtained in real time from the input voltage and output voltage using the dual voltage synthesis method, and the duty cycle is adjusted according to the trigger pulse distribution method, and the adjusted duty cycle Output to the EPM1270 auxiliary controller, and send the output voltage sector and synchronization signal to the EPM1270 auxiliary controller at the same time;

Use the EPM1270 auxiliary controller to decode the input voltage sector, output voltage sector, duty cycle and synchronization signal output by the TMS320LF2812 main controller according to the trigger pulse distribution method, so as to reduce the input current pulse position during the sector switching process. changes in

The three-phase-single-phase matrix converter bidirectional switch is driven by the driving circuit.

In this embodiment, the trigger pulse distribution method is as follows: during the switching process of the input voltage sector, based on the principle that the position of the input current pulse has the smallest change, in different input voltage sectors, the maximum phase or the minimum phase of the input phase voltage is located at the switch. The trigger pulse distribution mode in the middle of the cycle ensures that the position of the input current pulse remains unchanged during the sector switching process, thereby suppressing the oscillation of the input current and the distortion of the output current during the sector switching process.

The two-way input line voltage information sampled by the input voltage sampling unit is converted through the line-to-phase voltage to obtain the three-phase phase voltage (u _a , u _b , u _c ), and judge the maximum u _max and the middle of the three-phase input phase voltage u _mid and the minimum phase u _min are respectively:

$\left\{\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; max</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; middle</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; middle</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span>\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; min</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}}<span\; class="notranslate">\; )</span>\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

The reference voltage u _base is defined as the phase voltage with the largest absolute value in the input voltage, so the input voltage can be divided into 12 sectors. Figure 3 shows the division of the input voltage sectors.

Define output voltage expectation value u _o >0 as output sector 1, u _o <0 as sector 2.

Take the output voltage in sector 1 as an example to illustrate the calculation method of the duty cycle. In order to simplify the calculation formula, the following intermediate variables are defined:

Δu _max =u _max -u _min

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; middle</span>}}<span\; class="notranslate">\; =</span>\left\{\begin{array}{cc}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; middle</span>}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; base</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; middle</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}& {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; base</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; min</span>}}\end{array}\right.<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In each switching cycle, the average output voltage can be obtained as:

In the formula, T _s is the switching cycle, T ₁ , T ₂ , T ₃ are time variables, and T _S =T ₁ +T ₂ +T ₃ , by selecting the time variables T ₁ , T ₂ , T ₃ the required output voltage.

Define the input current distribution factor α as

In formula (4), i _in(max) , i _in(mid) and i _in(min) represent the input three-phase current respectively.

From formula (3) and formula (4) can get

In order to reduce harmonic content, a symmetrical switching mode is adopted, that is, each duty cycle is distributed symmetrically around the midpoint of the switching cycle.

Taking the switching from input sector 1 (Figure 4(a)) to sector 2 (Figure 4(b)) as shown in Figure 4 as an example to illustrate the distribution of conventional trigger pulses and the current that occurs during input sector switching Pulse distribution position changes: In sector 1, the input phase a current pulse is distributed in the second and fourth parts of the switching cycle; in sector 2, the input phase a current pulse is distributed in the middle part of the switching cycle. It can be seen that during the switching process of the sector, the position of the current pulse of phase a changes, that is, the distance of the current pulse changes, resulting in a sudden change of the current pulse of phase a. Side voltage fluctuations reduce system stability and eventually lead to output current distortion.

In order to suppress the oscillation of the input current and reduce the distortion of the output current, it is necessary to adjust the position of the trigger pulse in the switching cycle of the sector to ensure that the position of the input current pulse remains unchanged during the sector switching process, thereby suppressing the fluctuation of the input current during the sector switching process. Oscillation and distortion of output current.

Taking the switching from input sector 1 to sector 2 as shown in FIG. 5 as an example to illustrate the trigger pulse distribution method in the present invention. In the input sector 1, the original switching mode is maintained, and the position allocation in the sector 2 is shown in Figure 5, so as to ensure that the input phase a current pulse is always in the process of switching from input sector 1 to sector 2 Located in the second and fourth parts of the switching cycle, the c-phase current pulse is always in the middle of the switching cycle.

The switching process between other sectors can be analogized in turn, and the trigger pulse distribution in each sector can be obtained to ensure that the input current pulse position changes minimally during the input sector switching process, thereby reducing current oscillation and output current distortion during the sector switching process. The calculation method of the duty ratio of the trigger pulse distribution method is the same as that of the conventional dual voltage synthesis modulation strategy. After the duty ratio is calculated, it is redistributed to reduce the change of the input current pulse position, and at the same time ensure that the output voltage is a given output voltage value .

Claims (1)

1. be used to suppress three-phase-single-phase matrix convertor current oscillation and Distortion Control system, its three-phase-single-phase matrix convertor main circuit is to be made up of six bidirectional switchs; Its design feature is in the control system of said three-phase-single-phase matrix convertor, to include input voltage sampling unit, input and output over current fault detecting unit, TMS320LF2812 master controller, EPM1270 assistant controller and drive circuit;

Said input voltage sampling unit, any two-way input line voltage of sampling, and send into the TMS320LF2812 master controller, be used for confirming the affiliated sector of input voltage;

Said input and output over current fault detecting unit detects the overcurrent information of instantaneous net side power supply and load, and sends into the EPM1270 assistant controller, delivers to the TMS320LF2812 master controller simultaneously;

Said TMS320LF2812 master controller is sector auxiliary information under said EPM1270 assistant controller sends input voltage in real time, in order to judge the sector state of input voltage; The output voltage information of given three-phase-single-phase matrix convertor in said TMS320LF2812 master controller; With sector under the said output voltage information judgement output voltage; Adopt two voltage synthetic methods to obtain duty ratio in real time by said input voltage and output voltage; According to the trigger impulse distribution mode duty ratio is adjusted, adjusted duty ratio is outputed to the EPM1270 assistant controller, send output voltage sector information and synchronizing signal simultaneously to the EPM1270 assistant controller;

Said EPM1270 assistant controller; Input voltage sector auxiliary information, output voltage sector information, duty ratio and synchronizing signal to the output of TMS320LF2812 master controller are decoded according to said trigger impulse distribution mode, to reduce the variation of input current pulse position in the handoff procedure of sector;

Said drive circuit is used for the bidirectional switch of three-phase-single-phase matrix convertor is driven;

Said trigger impulse distribution mode is: in the handoff procedure of input voltage sector; Changing minimum with the input current pulse position is principle; In the different input voltages sector, adopt input phase voltage maximal phase or minimum phase in the trigger impulse distribution mode of the centre of switch periods respectively; So that the input current pulse position is constant in the handoff procedure of input voltage sector, suppress concussion and the distortion of output current of input current in the handoff procedure of input voltage sector.

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