CN108322076B - Voltage-sharing control system and method for parallel H-bridge type converter of alternating current system - Google Patents

Abstract

The invention discloses a voltage equalization control method of an AC system paralleled H-bridge type converter. By introducing a reactive component command value into an AC voltage controller, and at the same time in the DC voltage equalization controller, the DC side voltage deviation of each module is adjusted. The reactive current deviation is generated, so as to realize the real power redistribution among the modules without affecting the total active power of the entire converter, and then realize the balanced control of the DC side voltage of each module. The power component voltage command value is designed to adjust the active power deviation between the modules, thus ensuring that the DC voltage balance of each module is achieved within the full range of the system current range. Improve system efficiency and have good application prospects.

Description

A voltage equalization control system and method for parallel H-bridge converters in an AC system

technical field

The invention belongs to the technical field of power electronic converter control, and in particular relates to a voltage equalization control system and method of an AC system paralleling H-bridge type converters.

Background technique

With the access of more and more power electronic components in the AC power system, the interaction between them is easy to cause the problem of small signal stability of the system, and this problem can be solved by examining the relationship between the impedances of each port on the system bus. Therefore, the measurement of port impedance in actual engineering is very important to analyze the stability of the system. The basic principle of AC system port impedance measurement is: first inject a current or voltage disturbance with a certain frequency and a certain amplitude into the system port, then extract the voltage or current response of the port at this frequency, and then calculate the port impedance at this frequency. Since the disturbance needs to be injected into the power port and needs to withstand the high voltage or high current of the system, the disturbance injection is the most critical link in the entire impedance measurement.

Disturbance injection is divided into parallel injection and series injection. Parallel injection is used to accurately measure the low impedance port on the bus, and series injection is used to accurately measure the high impedance port. There are two main ways to realize series disturbance injection at present, namely bridge converter based on coupling transformer and parallel H-bridge converter. The latter can realize low-frequency disturbance injection because of avoiding coupling transformer. significant.

Figure 1 shows the basic structure of a parallel H-bridge converter by taking the number of H-bridge modules N equal to 3 as an example. Since the DC-side capacitance of the parallel-connected H-bridge converter is suspended, its voltage needs to be controlled; at the same time, in order to In order to divide the system current evenly among the modules, it is necessary to control the AC side current of each module. Figure 2 shows the overall structure of the parallel H-bridge converter control system. It first receives the disturbance voltage command from the upper controller, and then collects the DC side voltage of each module, the AC side current of each module, the output AC voltage and the system current by collecting After being processed by the control system, the control signal is output to control the on-off of the fully-controlled power semiconductor devices inside each H-bridge module, and finally the output voltage of the AC output port contains a disturbance voltage component.

In the existing parallel H-bridge converter control system, when the current amplitude of the system is small, the balanced control of the DC side voltages of each module can be achieved, and the voltages are equal at this time; when the system current amplitude is greater than a certain value (and the specific When the value is much smaller than the rated value), the DC side voltage of each module cannot be realized, and there is a large difference between the voltages at this time, which can trigger the overvoltage protection and cause shutdown, which seriously restricts the operating range of the parallel H-bridge converter. . In addition, in the prior art, additional resistors are connected in parallel on the DC side of each module to realize the voltage balance control of each DC side when the system current amplitude is large. This solution can improve the operating range of the system current amplitude to a certain extent. However, the introduction of additional resistors It will lead to an increase in the size of the device and an increase in system loss.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a voltage equalization control system and method of parallel H-bridge type converters in an AC system, so as to overcome the deficiencies of the prior art.

In order to achieve the above objects, the present invention adopts the following technical solutions.

A voltage equalization control method for an AC system paralleled H-bridge type converter, comprising the following steps:

Step 1), obtain the AC voltage active component amplitude command value v _Cpm ^* through the average DC voltage controller;

Step 2), obtain the cosine value and the sine value of the fundamental component phase θ of the system current i _S by the phase-locked loop;

Step 3), through the AC voltage controller according to the AC voltage active component amplitude command value obtained in step 1) and the cosine value and sine value of the fundamental wave component phase θ obtained in step 2) to obtain each H-bridge module AC current unified command value i _L ^* ;

Step 4), obtain each H-bridge module AC current deviation command value i _Ldk ^* through the DC voltage equalization controller;

Step 5), add the AC current unified command value i _L ^* output by the AC voltage controller and the AC current deviation command value i _Ldk ^* output by the DC voltage equalization controller to obtain the corresponding H bridge module AC current command value i _Lk ^* ; Then the difference between i _Lk ^* and the actual AC current i _Lk of the corresponding H-bridge module is used as the input of the AC current regulator, and its output is the duty cycle d _k of the corresponding H-bridge module, which is input to the pulse width connected to each H-bridge module The modulator can realize the voltage equalization control of the H-bridge converter.

将直流电压指令值v_dc ^*与平均值

作差后作为直流电压调节器G_VDC的输入，进而得到交流电压有功分量幅度指令值v_Cpm ^*。Further, in step 1), first collect the DC side voltage v _dck of each H bridge module through the average DC voltage controller, and then calculate the average DC side voltage v _dck of each H bridge module through the AVE module in the average DC voltage controller. value

Compare the DC voltage command value v _dc ^* with the average value

After the difference, it is used as the input of the DC voltage regulator G _VDC , and then the command value v _Cpm ^* of the amplitude of the active component of the AC voltage is obtained.

Further, in step 2), the phase-locked loop collects the system current, filters out the noise, and outputs the phase θ of the fundamental component of the system current:

i _S1 =I _Sm cosθ

Among them, i _S1 is the instantaneous value of the fundamental wave component of the system current, and I _Sm is the amplitude of the fundamental wave current.

Further, in step 3), the cosine value of the fundamental wave component phase θ obtained according to step 2) is multiplied by the command value v _Cpm ^* of the active component amplitude of the AC voltage output by the average DC voltage controller in step 1), and at the same time according to step 2 ) The sine value of the fundamental wave component phase θ obtained is multiplied by the given AC voltage reactive component amplitude command value v _Cqm ^* , and after adding the two products, superimpose the AC voltage upper layer command value v _p ^* to obtain the AC voltage command value v _C ^* ; Subtract the AC voltage command value v _C ^* from the sampled actual AC voltage value v _C to obtain the value as the input of the AC voltage regulator G _VC , and then the unified command value i _L ^* of the AC current of each H-bridge module can be obtained .

然后将平均值

分别于各H桥模块直流电压v_dck作差，得到各H桥模块直流电压与它们平均值之间偏差，并将这些偏差分别作为各H桥模块直流电压均衡调节器G_ILT的输入，然后根据步骤2)得到的基波分量相位θ的正弦值与各H桥模块直流电压均衡调节器的输出相乘，即得到各H桥模块交流电流偏差指令值i_Ldk ^*。Further, in step 4), the DC voltage of each H-bridge module is collected by the DC voltage equalization controller and their average value is calculated.

then average

Differentiate the DC voltage v _dck of each H-bridge module to obtain the deviation between the DC voltage of each H-bridge module and their average value, and use these deviations as the input of the DC voltage equalization regulator G _ILT of each H-bridge module, and then according to Step 2) Multiply the obtained sine value of the phase θ of the fundamental wave component by the output of each H-bridge module DC voltage equalizer to obtain the AC current deviation command value i _Ldk ^* of each H-bridge module.

A voltage equalization control system for an AC system paralleled H-bridge type converters, comprising an average DC voltage controller, a phase-locked loop, an AC voltage controller, a DC voltage balance controller, an AC current controller and a pulse width modulator. The output end of the DC voltage controller is connected to the input end of the AC voltage controller, the output end of the phase-locked loop is connected to the input end of the AC voltage controller and the input end of the DC voltage balance controller, the output end of the AC voltage controller and the The output terminals of the DC voltage equalization controller are all connected to the input terminals of the AC current controller, and the AC current controller is connected to the pulse width modulator;

The average DC voltage controller is used to obtain the command value v _Cpm ^* of the active component amplitude of the AC voltage,

The phase-locked loop is used to obtain the phase θ of the fundamental component of the system current i _S ,

The AC voltage controller is used to obtain the unified command value i _L ^* of the AC current of each H-bridge module,

The DC voltage equalization controller is used to obtain the AC current deviation command value i _Ldk ^* of each H-bridge module;

The pulse width modulator is used to convert the control duty ratio of each H-bridge module into an on-off control signal of the power semiconductor device inside the corresponding H-bridge module.

Further, the AC current controller and the pulse width modulator are connected with the H bridge module in one-to-one correspondence.

Compared with the prior art, the present invention has the following beneficial technical effects:

The invention provides a voltage equalization control method of an AC system paralleled H-bridge type converters. By introducing a reactive component command value into an AC voltage controller, and at the same time, in the DC voltage equalization controller, the DC side of each H-bridge module is connected. The voltage deviation generates reactive current deviation, so that the active power redistribution between the H-bridge modules can be realized without affecting the total active power of the entire converter, and the balanced control of the DC side voltage of each H-bridge module is realized. The method can design the voltage command value of the AC voltage reactive power component to adjust the size of the active power deviation between the modules, thus ensuring that the DC voltage balance of each module can be achieved within the full range of the system current range, and the present invention does not require additional resistance on the DC side, Therefore, the volume of the device can be reduced and the system efficiency can be improved, which has a good application prospect.

Description of drawings

Fig. 1 is the main circuit diagram of the parallel H-bridge type converter.

Fig. 2 is the overall structure of the control system of the present invention.

FIG. 3 is the internal structure of the average DC voltage controller of the present invention.

FIG. 4 is the internal structure of the AC voltage controller of the present invention.

FIG. 5 is the internal structure of the DC voltage equalization controller of the present invention.

FIG. 6 is the internal structure of the AC current controller of the present invention.

FIG. 7 is an experimental waveform diagram of the voltage equalization control method proposed by the present invention.

FIG. 8 is an experimental waveform diagram using the existing control method.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in further detail:

As shown in Figure 1, the parallel H-bridge converter includes N parallel H-bridge modules, N is not less than 2, and each H-bridge module is composed of four fully-controlled power semiconductor devices with anti-parallel diodes connected inside. , the DC side of each H-bridge module is connected to its own DC capacitor C _k , the AC side is connected to the output port in parallel through the inductor L _k , and the AC capacitor C _p is connected in parallel at the output port; the parallel H-bridge converter is connected in series in the AC system , the system current flows in from one of its output terminals and flows out from the other.

As shown in Figures 2 to 6, a parallel H-bridge converter control system includes an average DC voltage controller, a phase-locked loop, an AC voltage controller, a DC voltage balance controller, an AC current controller and a pulse width controller. A modulator, the output terminal of the average DC voltage controller is connected to the input terminal of the AC voltage controller, the output terminal of the phase-locked loop is connected to the input terminal of the AC voltage controller and the input terminal of the DC voltage balance controller, the AC voltage controller The output terminal of the DC voltage equalization controller and the output terminal of the DC voltage equalization controller are both connected to the input terminal of the AC current controller, and the AC current controller is connected to the pulse width modulator. The pulse width modulator is used to convert the control duty ratio of each H-bridge module into Corresponding on-off control signals of power semiconductor devices inside the H-bridge module, AC current controller and pulse width modulator are all connected one-to-one with the H-bridge module;

The average DC voltage controller is used to obtain the command value v _Cpm ^* of the active component amplitude of the AC voltage,

The phase-locked loop is used to obtain the phase θ of the fundamental component of the system current i _S ,

The AC voltage controller is used to obtain the unified command value i _L ^* of the AC current of each H-bridge module,

The DC voltage balance controller is used to obtain the AC current deviation command value i _Ldk ^* of each H-bridge module,

The pulse width modulator is used to convert the control duty ratio of each H-bridge module into an on-off control signal of the power semiconductor device inside the corresponding H-bridge module.

A voltage equalization control method for an AC system paralleled H-bridge type converter, comprising the following steps:

Step 1), obtain the AC voltage active component amplitude command value v _Cpm ^* through the average DC voltage controller;

Step 2), obtain the cosine value and the sine value of the fundamental component phase θ of the system current i _S by the phase-locked loop;

Step 3), through the AC voltage controller according to the AC voltage active component amplitude command value obtained in step 1) and the cosine value and sine value of the fundamental wave component phase θ obtained in step 2) to obtain each H-bridge module AC current unified command value i _L ^* ;

Step 4), obtain each H-bridge module AC current deviation command value i _Ldk ^* through the DC voltage equalization controller;

Step 5), adding the AC current unified command value i _L ^* output by the AC voltage controller and the AC current deviation command value i _Ldk ^* output by the DC voltage equalization controller to obtain the corresponding H bridge module AC current command value i _Lk ^* ; Then the difference between i _Lk ^* and the actual AC current i _Lk of the corresponding H-bridge module is used as the input of the AC current regulator, and its output is the duty cycle d _k of the corresponding H-bridge module, which is input to the pulse width connected to each H-bridge module The modulator can realize the voltage equalization control of the H-bridge converter.

将直流电压指令值v_dc ^*与平均值

作差后作为直流电压调节器G_VDC的输入，进而得到交流电压有功分量幅度指令值v_Cpm ^*；In step 1), first collect the DC side voltage v _dck of each H bridge module through the average DC voltage controller, and then calculate the average value of the DC side voltage v _dck of each H bridge module through the AVE module in the average DC voltage controller.

Compare the DC voltage command value v _dc ^* with the average value

After the difference, it is used as the input of the DC voltage regulator G _VDC , and then obtains the command value v _Cpm ^* of the amplitude of the active component of the AC voltage;

DC voltage regulator G _VDC adopts proportional integral regulator;

In step 2), the phase-locked loop collects the system current, filters out the noise, and outputs the phase θ of the fundamental wave component of the system current;

i _S1 =I _Sm cosθ

Among them, i _S1 is the instantaneous value of the fundamental wave component of the system current, and I _Sm is the amplitude of the fundamental wave current.

In step 2), the fundamental wave component phase θ of the system current i _S is obtained by the phase-locked loop, and the cosine value and the sine value of the fundamental wave component phase θ are calculated;

In step 3), the cosine value of the fundamental wave component phase θ obtained according to step 2) is multiplied by the command value v _Cpm ^* of the active component amplitude of the AC voltage outputted by the average DC voltage controller in step 1), and at the same time according to step 2) The sine value of the fundamental wave component phase θ is multiplied by the given AC voltage reactive component amplitude command value v _Cqm ^* , and after adding the two products, the AC voltage upper layer command value v _p ^* is superimposed to obtain the AC voltage command value v _C ^* ; After subtracting the AC voltage command value v _C ^* from the sampled actual AC voltage value v _C , the value obtained is the input of the AC voltage regulator G _VC , and the unified command value i _L ^* of the AC current of each H-bridge module can be obtained;

然后将平均值

分别于各H桥模块直流电压v_dck作差，得到各H桥模块直流电压与它们平均值之间偏差，并将这些偏差分别作为各H桥模块直流电压均衡调节器G_ILT的输入，然后根据步骤2)得到的基波分量相位θ的正弦值与各H桥模块直流电压均衡调节器的输出相乘，即得到各H桥模块交流电流偏差指令值i_Ldk ^*；In step 4), the DC voltage of each H-bridge module is collected by the DC voltage equalization controller and their average value is calculated

then average

Differentiate the DC voltage v _dck of each H-bridge module to obtain the deviation between the DC voltage of each H-bridge module and their average value, and use these deviations as the input of the DC voltage equalization regulator G _ILT of each H-bridge module, and then according to Step 2) Multiplying the sine value of the obtained fundamental wave component phase θ with the output of each H-bridge module DC voltage equalization regulator to obtain each H-bridge module AC current deviation command value i _Ldk ^* ;

As shown in Figures 7 and 8, the control method proposed by the present invention and the traditional control method were tested experimentally under the same system current conditions. During the test, the system current fundamental wave amplitude was 24A, the system fundamental wave frequency was 60Hz, and the DC voltage command was The value v _dc ^* is 130V, and a four-channel oscilloscope is used to measure the time-domain waveform diagram. Figure 7 is the waveform diagram of the control method proposed by the present invention, and Figure 8 is the waveform diagram of the traditional control method. Channel 1 in the figure is #1H The bridge module DC voltage v _dc1 , the channel 2 is the #2H bridge module DC voltage v _dc2 , the channel 3 is the AC voltage v _C , and the channel 4 is the system current i _S ;

It can be seen from the experimental test waveforms that under the traditional control method, the DC voltage of the modules is obviously unbalanced, and the deviation between the DC voltages exceeds 10V. With the control method of the present invention, the deviation between the DC voltages can be ignored, and the DC voltage is well realized. balanced.

Claims (7)

1. A voltage-sharing control method for an alternating current system parallel H-bridge type converter is characterized by comprising the following steps;

step 1), obtaining an alternating current voltage active component amplitude instruction value v through an average direct current voltage controller_Cpm ^*；

Step 2), obtaining system current i through a phase-locked loop_SCosine and sine values of the fundamental component phase theta;

step 3), obtaining an alternating voltage active component amplitude instruction value v according to the step 1) through an alternating voltage controller_Cpm ^*And step 2) obtaining cosine values and sine values of fundamental component phase theta to obtain unified command values i of alternating currents of all H-bridge modules_L ^*；

Step 4), obtaining alternating current deviation instruction values i of all H-bridge modules through the direct current voltage balance controller_Ldk ^*；

Step 5) unifying the alternating current unified command value i output by the alternating voltage controller_L ^*And an alternating current deviation instruction value i output by the direct current voltage balance controller_Ldk ^*After the addition, the corresponding H-bridge module alternating current instruction value i is obtained_Lk ^*(ii) a Then i is_Lk ^*Actual alternating current i of corresponding H-bridge module_LkAfter difference is made, the difference is used as the input of an alternating current regulator, and the output of the alternating current regulator is the corresponding duty ratio d of the H-bridge module_kAnd the voltage-sharing control of the H-bridge type converter can be realized by inputting the voltage-sharing control signal to the pulse width modulator connected with each H-bridge module.

2. The parallel H-bridge of claim 1 for AC systemThe voltage-sharing control method of the type converter is characterized in that in the step 1), the voltage v at the direct current side of each H-bridge module is collected by an average direct current voltage controller_dckThen, the voltage v at the DC side of each H-bridge module is calculated by an AVE module in an average DC voltage controller_dckAverage value of (2)

The direct current voltage command value v_dc ^*And the average value

After differencing, the voltage is used as a DC voltage regulator G_VDCTo obtain the amplitude command value v of the active component of the alternating voltage_Cpm ^*。

3. The voltage-sharing control method for the parallel H-bridge type converter of the alternating current system according to claim 1, wherein in the step 2), the phase-locked loop collects the system current, filters noise in the system current, and outputs a phase θ of a fundamental component of the system current:

i_S1＝I_Smcosθ

wherein i_S1For instantaneous value of fundamental component of system current, I_SmIs the fundamental current amplitude.

4. The voltage-sharing control method for the parallel H-bridge type converter of the alternating current system according to claim 1, wherein in the step 3), the cosine value of the phase θ of the fundamental component obtained in the step 2) and the amplitude command value v of the active component of the alternating current voltage output by the average direct current voltage controller in the step 1) are obtained_Cpm ^*Multiplying, and simultaneously obtaining the sine value of the phase theta of the fundamental component and a given amplitude command value v of the reactive component of the alternating voltage according to the step 2)_Cqm ^*Multiplying, adding the two products and superposing the upper-level command value v of the AC voltage_p ^*Obtaining an alternating voltage command value v_C ^*(ii) a The command value v of the alternating voltage_C ^*Subtracting the sampled actual value v of the AC voltage_CThe obtained value is an AC voltage regulator G_VCInputting to obtain the unified command value i of the alternating current of each H-bridge module_L ^*。

5. The voltage-sharing control method for the parallel H-bridge type converter of the alternating current system according to claim 1, wherein in the step 4), the direct current voltage of each H-bridge module is collected by the direct current voltage-sharing controller and the average value of the direct current voltages is calculated

Then average value

Respectively at each H-bridge module DC voltage v_dckTaking difference to obtain the deviation between the DC voltage of each H-bridge module and the average value thereof, and taking the deviation as the DC voltage balance regulator G of each H-bridge module_ILTThen multiplying the sine value of the fundamental component phase theta obtained in the step 2) with the output of each H-bridge module direct-current voltage balance regulator to obtain the alternating-current deviation instruction value i of each H-bridge module_Ldk ^*。

6. A control system based on the voltage-sharing control method of the AC system parallel H-bridge type converter is characterized by comprising an average DC voltage controller, a phase-locked loop, an AC voltage controller, a DC voltage balancing controller, an AC current controller and a pulse width modulator, wherein the output end of the average DC voltage controller is connected to the input end of the AC voltage controller, the output end of the phase-locked loop is connected to the input end of the AC voltage controller and the input end of the DC voltage balancing controller, the output end of the AC voltage controller and the output end of the DC voltage balancing controller are both connected to the input end of the AC current controller, and the AC current controller is connected with the pulse width modulator;

the average DC voltage controller is used for acquiring an AC voltage active component amplitude command value v_Cpm ^*，

The phase-locked loop is used for acquiring system current i_SThe phase of the fundamental component of (a) theta,

the alternating voltage controller is used for acquiring the uniform alternating current instruction value i of each H-bridge module_L ^*，

The DC voltage balance controller is used for acquiring an AC current deviation instruction value i of each H-bridge module_Ldk ^*，

The pulse width modulator is used for converting the control duty ratio of each H-bridge module into an on-off control signal of the power semiconductor device in the corresponding H-bridge module.

7. The control system of the voltage-sharing control method of the alternating current system parallel H-bridge type converter according to claim 6, wherein the alternating current controllers and the pulse width modulators are connected with the H-bridge modules in a one-to-one correspondence manner.

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