CN105680714A - Control method and device for output voltage of inverter - Google Patents

Abstract

The invention discloses a control method and device for an output voltage of an inverter. The method comprises the following steps: carrying out coordinate transformation on three-phase output voltages which are output to a load by the inverter and obtaining a first voltage feedback value Ud and a second voltage feedback value Uq under a dq coordinate system; calculating the first voltage feedback value Ud and a preset first load voltage value Ud* by a first adder, outputting a first calculation result, carrying out PIR control on the first calculation result and outputting a first compensation AC quantity; calculating the second voltage feedback value Uq and a preset second load voltage value Uq* by a second adder, outputting a second calculation result, carrying out PIR control on the second calculation result and outputting a second compensation AC quantity; carrying out inverse coordinate transformation on the first compensation AC quantity and the second compensation AC quantity to obtain three-phase compensation voltages, carrying out sine pulse width modulation on the three-phase compensation voltages to obtain pulse signals; and transmitting the pulse signals to the inverter as compensation quantities.

Description

Method and device for controlling output voltage of inverter

technical field

The invention relates to the technical field of inverter control, in particular to a method and device for controlling the output voltage of an inverter.

Background technique

The inverter is to convert the low-quality AC power obtained from the grid side or the power generated by DC batteries and other renewable energy sources (such as wind energy and solar energy) into high-quality AC power to meet the load requirements. , so as to supply power to sensitive electronic equipment, so the inverter is one of the important components of the power electronic device. At present, the requirements for the power quality of power supply in the application field are constantly improving. At the same time, with the rapid development of distributed power generation systems, the importance of inverters has become more and more obvious. One of the key technologies of the new distributed power generation system is to develop power electronic equipment that reliably connects the power grid with various power generation devices, and the inverter is the core device of this power electronic device.

At present, the research and development of traditional inverters based on linear loads has been relatively complete and mature, but there are few studies on the characteristics and performance of new inverters based on nonlinear loads. This is out of step with the widespread application of a large number of power electronic devices working on nonlinear loads. Therefore, it is of great significance to study the characteristics and performance of the inverter based on the nonlinear load.

The development trend of distributed power generation is the application of micro-grids composed of multiple inverters. In most cases, the loads in the actual system should contain nonlinear loads. In addition to completing the conversion of electric energy to AC and DC, the inverter should also be able to provide stable and high-quality electric energy under linear and nonlinear loads. Two existing inverter control methods are described below:

(1) Power-voltage-current three-loop control method

This method uses the droop characteristic to design the power outer loop controller of the inverter. The power outer loop controller of this inverter not only uses the voltage closed-loop controller to improve the control ability of the inverter output voltage, but also uses the current The closed-loop controller improves the response speed of the system, and most importantly, it realizes the automatic power distribution function of the inverter based on local information. It is more practical for traditional power grids where the impedance of high-voltage transmission and transmission lines is mainly inductive, but for the system of medium and low-voltage distribution networks where the impedance of the line is mainly resistive, the impedance of the line impedance is mainly resistive. The control performance of the method is adversely affected. In this method, the inverter can make the equivalent output impedance of the inverter inductive in the base frequency band by adjusting its voltage and current closed-loop control parameters, so as to realize the adjustment effect on the line resistance-inductance ratio and improve the performance of the inverter. power distribution performance.

The disadvantages of this method are as follows: Since the voltage and current closed-loop control parameters in the power-voltage-current three-loop control method need to take into account the stability requirements of the inverter, this method has no effect on the inverter through Thevenin or Norton equivalent The output impedance adjustment range is relatively small, and the improvement effect on the output voltage control performance of the inverter is limited under nonlinear load conditions.

(2) Virtual impedance control method

In order to overcome the negative influence of the resistive line impedance under the "power-voltage-current" three-loop droop control performance and improve the power control performance of the inverter, a virtual impedance control method is proposed. In this method, the voltage drop of the inverter output current on the virtual impedance is subtracted from the voltage closed-loop command, and the adjustment of the virtual impedance is used to realize the adjustment of the equivalent output impedance of the inverter, and then the line impedance ratio is realized. Compared with the above-mentioned three-loop control method, this method can effectively suppress the adverse effect of the main resistive line impedance on the output power control performance of the inverter.

The disadvantages of this method are as follows: the virtual impedance control method mainly adjusts the impedance ratio of the fundamental frequency, and cannot realize the adjustment of the harmonic impedance of the inverter, and thus cannot adjust the output voltage of the inverter under nonlinear load conditions.

Therefore, for the problem of improving the output voltage of the inverter under nonlinear load conditions, no effective solution has been proposed so far.

Contents of the invention

The invention provides a method and device for controlling the output voltage of an inverter to at least solve the problem of how to effectively improve the output voltage of the inverter under nonlinear load conditions.

According to one aspect of the present invention, a method for controlling the output voltage of an inverter is provided, including: performing coordinate transformation on the three-phase output voltage output by the inverter to the load to obtain the first voltage feedback value U in the dq coordinate system _d and the second voltage feedback value U _q ; use the first adder to calculate the first voltage feedback value U _d and the preset first load voltage value U _d ^* , output the first calculation result, and calculate the first load voltage value U d *. A calculation result is subjected to proportional integral resonance (Proportion Integral Resonant, referred to as PIR) control, and the first compensation AC value is output; the second adder is used to compare the second voltage feedback value U _q and the preset second load voltage value U _q ^* performing calculations, outputting a second calculation result, performing PIR control on the second calculation result, and outputting a second compensation exchange amount; performing an inverse coordinate transformation on the first compensation exchange amount and the second compensation exchange amount to obtain three phase compensation voltage, performing sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmitting the pulse signal to the inverter as a compensation amount.

In one embodiment, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

According to another aspect of the present invention, a method for controlling the output voltage of an inverter is provided, including: performing coordinate transformation on the three-phase output voltage output by the inverter to the load, to obtain the first voltage feedback value in the dq coordinate system U _d and the second voltage feedback value U _q ; use the first adder to calculate the first voltage feedback value U _d and the preset first load voltage value U _d ^* , and output the first calculation result, and the Proportional-integral resonance PIR control is performed on the first calculation result, and its output is used as the first current given value I _d ^* ; the second adder is used to compare the second voltage feedback value U _q and the preset second load voltage value U _q ^* is calculated, and the second calculation result is output, and the PIR control is performed on the second calculation result, and its output is used as the second current given value I _q ^* ; coordinate transformation is performed on the three-phase output current of the inverter , to obtain the first current feedback value I _d and the second current feedback value I _q in the dq coordinate system; use the third adder to calculate the first current feedback value I _d and the first current given value I _d ^* performing calculations, outputting a third calculation result, performing _PIR control on the third calculation result, and outputting the first compensation exchange amount; Calculate the value I _q ^* , output the fourth calculation result, perform PIR control on the fourth calculation result, and output the second compensation exchange amount; perform inverse coordinates on the first compensation exchange amount and the second compensation exchange amount Transform to obtain a three-phase compensation voltage, perform sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmit the pulse signal to the inverter as a compensation amount.

In one embodiment, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

According to one aspect of the present invention, a control device for the output voltage of an inverter is provided, including: a coordinate transformation unit for performing coordinate transformation on the three-phase output voltage output by the inverter to the load to obtain the The first voltage feedback value _Ud and the second voltage feedback value _Uq ; the first adder is used to calculate the first voltage feedback value _Ud and the preset first load voltage value _Ud ^* , and output the first A calculation result; the first PIR controller is used to perform PIR control on the first calculation result, and output the first compensation AC value; the second adder is used to calculate the second voltage feedback value U _q and preset The second load voltage value U _q ^* is calculated, and the second calculation result is output; the second PIR controller is used to perform PIR control on the second calculation result, and output the second compensation AC amount; the inverse coordinate transformation unit uses Performing an inverse coordinate transformation on the first compensated AC quantity and the second compensated AC quantity to obtain a three-phase compensation voltage; a sinusoidal pulse width modulation unit configured to perform sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmit the pulse signal to the inverter as a compensation amount.

In one embodiment, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

In one embodiment, the transfer functions of the first PIR controller and the second PIR controller are: Among them, s represents the time domain, K _P is the proportional coefficient, K _I is the integral coefficient, K _R is the resonance coefficient, ω _c is the resonance cut-off frequency, and 6ω ₀ is the resonance frequency.

According to another aspect of the present invention, there is provided a control device for inverter output voltage, including: a first coordinate transformation unit, used to perform coordinate transformation on the three-phase output voltage output by the inverter to the load, to obtain dq coordinates The first voltage feedback value U _d and the second voltage feedback value U _q under the system; the first adder is used to calculate the first voltage feedback value U _d and the preset first load voltage value U _d ^* , output the first calculation result; the first PIR controller is used to perform PIR control on the first calculation result, and output it as the first current given value I _d ^* ; the second adder is used for the said The second voltage feedback value U _q is calculated with the preset second load voltage value U _q ^* , and a second calculation result is output; the second PIR controller is used to perform PIR control on the second calculation result, and output it As the second current given value I _q ^* ; the second coordinate transformation unit is used to perform coordinate transformation on the three-phase output current of the inverter to obtain the first current feedback value I _d and the second current feedback value I d in the dq coordinate system a current feedback value I _q ; a third adder, configured to calculate the first current feedback value I _d and the first current given value I _d ^* , and output a third calculation result; a third PIR controller, It is used to perform PIR control on the third calculation result, and output the first compensation AC value; the fourth adder is used to perform PIR control on the second current feedback value I _q and the second current given value I _q ^* Calculate and output the fourth calculation result; the fourth PIR controller is used to perform PIR control on the fourth calculation result, and output the second compensation exchange amount; the inverse coordinate transformation unit is used to calculate the first compensation exchange amount and performing an inverse coordinate transformation on the second compensation AC quantity to obtain a three-phase compensation voltage; a sinusoidal pulse width modulation unit for performing sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and using the pulse signal as a compensation amount is transmitted to the inverter.

In one embodiment, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

In one embodiment, the transfer functions of the first PIR controller, the second PIR controller, the third PIR controller and the fourth PIR controller are: Among them, s represents the time domain, K _P is the proportional coefficient, K _I is the integral coefficient, K _R is the resonance coefficient, ω _c is the resonance cut-off frequency, and 6ω ₀ is the resonance frequency.

Through the control method and device of the inverter output voltage of the present invention, the equivalent impedance of the specific order of the inverter is reduced by using PIR control, and the harmonic content of the inverter output voltage caused by the nonlinear load is reduced, and the control of the inverter output voltage is realized. Compensation of the output harmonic voltage, thereby improving the output voltage of inverters feeding non-linear loads. At the same time, only one set of resonance control links needs to be added, compared with the prior art, the control links are reduced, and the implementation is simple. In addition, the control method of the voltage outer loop and the current inner loop can not only improve the voltage, but also stabilize the current.

Description of drawings

The accompanying drawings described here are used to provide a further understanding of the present invention, and constitute a part of the application. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute a limitation to the present invention. In the attached picture:

Fig. 1 is the topological structure diagram of the inverter of the embodiment of the present invention;

Fig. 2a is an equivalent schematic diagram of the fundamental wave of the inverter under a nonlinear load according to an embodiment of the present invention;

Fig. 2b is an equivalent schematic diagram of the 5th harmonic of the inverter under a nonlinear load according to an embodiment of the present invention;

Fig. 2c is an equivalent schematic diagram of the 7th harmonic of the inverter under a nonlinear load according to an embodiment of the present invention;

3 is a schematic diagram of a synchronous rotating coordinate system including harmonics according to an embodiment of the present invention;

FIG. 4 is a flow chart of a method for controlling an output voltage of an inverter according to Embodiment 1 of the present invention;

5 is a flow chart of a method for controlling the output voltage of an inverter according to Embodiment 2 of the present invention;

Fig. 6 is a structural block diagram of an inverter output voltage control device according to Embodiment 3 of the present invention;

Fig. 7 is a structural block diagram of an inverter output voltage control device according to Embodiment 4 of the present invention;

Fig. 8 is a schematic diagram of controlling the output voltage of the inverter according to Embodiment 5 of the present invention;

Fig. 9 is a schematic diagram of controlling the output voltage of the inverter according to the sixth embodiment of the present invention.

detailed description

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In distributed power generation units except wind power generation and diesel engine power generation, most of them need to control the output power through inverters. The topology of the inverter is shown in Figure 1. The front-end DC part (U _dc and capacitor C ₁ ) can be DC sources such as photovoltaic cells, batteries, and super capacitors. Transistors T ₁ to T ₆ and diodes D ₁ to D ₆ An inverter is formed, and its output is supplied to the load and the power grid after being filtered by LC. In the independent operation mode, the control target of the inverter is to output three-phase symmetrical sine wave voltage.

When the load in Figure 1 is a nonlinear load, such as switching power supply of PC, various frequency conversion air conditioners, voltage inverter, energy-saving lamps, etc., these nonlinear loads will generate 5th and 7th harmonic currents during use , These 5th and 7th harmonic currents react on the equivalent output internal resistance of the inverter, which will cause the output voltage of the inverter to contain 5th and 7th harmonics, thereby affecting the quality of power supply to other loads.

Fig. 2a is an equivalent schematic diagram of the fundamental wave of the inverter according to the embodiment of the present invention. As shown in Fig. 2a, V _ref is the equivalent voltage source of the inverter; V _out is the fundamental wave output voltage of the inverter; Z _nei is the inverse Transformer equivalent internal resistance, including filter and control parameters; Z _line is the line impedance; I _load is the equivalent current source of the fundamental load. Fig. 2b is the 5th harmonic equivalent schematic diagram of the inverter of the embodiment of the present invention, and Fig. 2c is the 7th harmonic equivalent schematic diagram of the inverter of the embodiment of the present invention, as shown in Fig. 2b and 2c, I _5rd and I _7rd are the 5th harmonic current source and the 7th harmonic current source caused by the nonlinear load, Z _line is the line impedance, Z _5rd is the harmonic impedance corresponding to the 5th harmonic current, and Z _7rd is the 7th harmonic The harmonic impedance corresponding to the wave current, V _{out_5rd} is the 5th harmonic voltage output by the inverter, and V _{out_7rd} is the 7th harmonic voltage output by the inverter.

According to the superposition theorem, it can be seen that the final output voltage of the inverter is V _out +V _{out_5rd} +V _{out_7rd} , where V _{out_5rd} =I _5rd ×Z _5rd , V _{out_7rd} =I _7rd ×Z _7rd . The harmonic voltages V _{out_5rd} and V _{out_7rd} output by the inverter can be reduced by reducing the harmonic impedances Z _5rd and Z _7rd corresponding to the respective harmonic currents. The output voltage of the inverter can be improved by reducing the equivalent impedance of a specific harmonic.

In order to reduce the equivalent impedance of a specific time, it is necessary to add 5 or 7 times of voltage compensation in the control link. If the 5th and 7th harmonics are extracted through a band-pass filter, it is necessary to give the same frequency, amplitude and initial phase angle to eliminate the harmonics, which is difficult in actual implementation, where the initial phase angle is determined is the hardest part. In addition, there is also a proposal to control and compensate the 5th and 7th harmonics after rotating coordinate transformation, but it needs to add two sets of control links, which makes the system control complicated.

The synchronous rotating coordinate system including harmonic voltage is shown in Figure 3. In Figure 3, d and q represent the fundamental wave rotating coordinate system, d ^-5 and q ^-5 represent the -5 harmonic rotating coordinate system, and d ⁺⁷ , q ⁺⁷ means the +7th harmonic rotating coordinate system, ω means the angular velocity, θ=ωt means the rotation angle, -5ω means the negative sequence rotation at the angular velocity of 5ω, and 7ω means the positive sequence rotation at the angular velocity of 7ω. The -5th and +7th harmonic voltages appear as DC quantities in their corresponding rotating coordinate systems, but after coordinate transformation, they appear as 6th harmonics in the fundamental wave rotating coordinate system d, q, and the fundamental wave is still a DC component , at this time, the d, q coordinate system contains the fundamental DC component and the 6th harmonic component that needs to be compensated. The solution of the present invention is to suppress and adjust the 6th harmonic component.

Embodiment one

This embodiment provides a method for controlling the output voltage of an inverter. Fig. 4 is a flowchart of a method for controlling the output voltage of an inverter according to Embodiment 1 of the present invention. As shown in Fig. 4, the method includes the following steps:

In step S401, coordinate transformation is performed on the three-phase output voltage output from the inverter to the load to obtain a first voltage feedback value U _d and a second voltage feedback value U _q in the dq coordinate system.

If the load is a nonlinear load, the three-phase output voltage includes: fundamental wave, -5th harmonic and 7th harmonic. After coordinate transformation, -5th harmonic and 7th harmonic appear as 6th in the dq coordinate system Harmonics, U _d and U _q both contain the fundamental wave dc amount and the 6th harmonic ac amount. Here, using the voltage outer loop control, the coordinate transformation is the voltage at the input end of the load.

Step S402, use the first adder to calculate the first voltage feedback value _Ud and the preset first load voltage value _Ud ^* , output the first calculation result, perform PIR control on the first calculation result, and output the first compensation AC quantity; use the second adder to calculate the second voltage feedback value U _q and the preset second load voltage value U _q ^* , output the second calculation result, perform PIR control on the second calculation result, and output the second compensation volume of communication.

The steps of obtaining the first compensation exchange quantity and the second compensation exchange quantity may be performed simultaneously. The calculation performed by the adder can be the load voltage value (given value) minus the voltage feedback value, and the obtained voltage value (including DC and AC) to be compensated is obtained. After PIR control, output the AC value that needs to be compensated (under the dq coordinate system).

Step S403, perform inverse coordinate transformation on the first compensated AC quantity and the second compensated AC quantity to obtain a three-phase compensation voltage, perform sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmit the pulse signal as a compensation quantity to the inverter Transformer. Among them, the inverse coordinate transformation is performed on the AC quantity to be compensated to obtain the abc three-phase voltage to be compensated, and the corresponding pulse signal is obtained after sinusoidal pulse width modulation, and the pulse signal can be used as the input of the inverter.

Through the control method of the inverter output voltage in this embodiment, the equivalent impedance of the specific order of the inverter is reduced by using PIR control, the harmonic content of the inverter output voltage caused by the nonlinear load is reduced, and the output Compensation of harmonic voltages, thereby improving the output voltage of inverters feeding non-linear loads. At the same time, only one set of resonance control links needs to be added, compared with the prior art, the control links are reduced, and the implementation is simple.

The traditional harmonic suppression method is mainly based on the PI regulator in the positive sequence synchronous rotating coordinate system, but the control bandwidth of the PI regulator is limited, and the PIR control method combining the traditional PI regulator and the resonant regulator is introduced into the control strategy , through the resonance controller of a specific order, the loop gain is increased, the specific harmonic is eliminated, and the harmonic impedance is reduced. The added resonance link is to compensate the network voltage harmonics and reduce the harmonic internal resistance.

Preferably, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities. _Ud ^* and _Uq ^* can be target load voltages, which can be given by voltage command. U _d ^* and U _q ^* are given as DC flow, which is equivalent to zero harmonic content command. When connected to a balanced load (that is, a linear load), it does not contain -5 and +7 harmonics, and the voltage is -5 and +7 The secondary feedback values U _d and U _q are both equal to 0, that is to say, when the load is balanced, the -5 and +7 secondary voltage loops do not work, and it can also run smoothly when the load is balanced.

Embodiment two

This embodiment provides another method for controlling the output voltage of the inverter. The difference between this embodiment and Embodiment 1 is that Embodiment 1 adopts a single voltage outer loop control, and this embodiment adopts a double-loop control method of voltage outer loop and current inner loop. For control, refer to the following steps S503 and S504 for current inner loop control. As shown in Figure 5, the method includes the following steps:

In step S501, coordinate transformation is performed on the three-phase output voltage output from the inverter to the load to obtain a first voltage feedback value U _d and a second voltage feedback value U _q in the dq coordinate system.

Step S502, use the first adder to calculate the first voltage feedback value _Ud and the preset first load voltage value _Ud ^* , output the first calculation result, and perform proportional-integral resonance PIR control on the first calculation result, and the Its output is used as the first given current value I _d ^* ; the second adder is used to calculate the second voltage feedback value U _q and the preset second load voltage value U _q ^* , and output the second calculation result, for the second The calculation result is subjected to PIR control, and its output is used as the second current given value I _q ^* .

Step S503, performing coordinate transformation on the three-phase output current of the inverter to obtain a first current feedback value I _d and a second current feedback value I _q in the dq coordinate system. If the load is a nonlinear load, the three-phase output current includes: fundamental wave, -5th harmonic and 7th harmonic. After coordinate transformation, -5th harmonic and 7th harmonic appear as 6th in the dq coordinate system Harmonics, I _d and I _q both contain fundamental wave direct current and 6th harmonic alternating current.

Step S504, use the third adder to calculate the first current feedback value I _d and the first current given value I _d ^* , output the third calculation result, perform PIR control on the third calculation result, and output the first compensation AC value ; Use the fourth adder to calculate the second current feedback value I _q and the second current given value I _q ^* , output the fourth calculation result, perform PIR control on the fourth calculation result, and output the second compensation AC amount.

The steps of obtaining the first compensation exchange quantity and the second compensation exchange quantity may be performed simultaneously. The operation performed by the adder can be the current given value minus the current feedback value, and the obtained current value (including DC and AC) to be compensated is obtained. After PIR control, output the AC value that needs to be compensated (under the dq coordinate system).

Step S505, perform inverse coordinate transformation on the first compensated AC quantity and the second compensated AC quantity to obtain a three-phase compensation voltage, perform sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmit the pulse signal as a compensation quantity to the inverter Transformer.

Through the control method of the inverter output voltage in this embodiment, the equivalent impedance of the specific order of the inverter is reduced by using PIR control, the harmonic content of the inverter output voltage caused by the nonlinear load is reduced, and the output Compensation of harmonic voltages, thereby improving the output voltage of inverters feeding non-linear loads. At the same time, only one set of resonance control links needs to be added, compared with the prior art, the control links are reduced, and the implementation is simple. Moreover, using the control method of the voltage outer loop and the current inner loop can not only improve the voltage, but also stabilize the current.

Preferably, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

Embodiment Three

Based on the same inventive concept, this embodiment provides a device for controlling the output voltage of an inverter, which can be used to implement the method described in Embodiment 1 above. Since the problem-solving principle of the inverter output voltage control device is similar to the inverter output voltage control method, the implementation of the inverter output voltage control device can refer to the implementation of the inverter output voltage control method, and repeat I won't repeat them here.

Fig. 6 is a structural block diagram of an inverter output voltage control device according to Embodiment 3 of the present invention. As shown in Fig. 6, the inverter output voltage control device 100 includes: a coordinate transformation unit 101, a first adder 102, a second A PIR controller 103 , a second adder 104 , a second PIR controller 105 , an inverse coordinate transformation unit 106 and a sinusoidal pulse width modulation unit 107 . This structure will be specifically described below.

The coordinate transformation unit 101 is connected to the input terminal of the load 10, and is used to perform coordinate transformation on the three-phase output voltage output from the inverter 20 to the load 10, to obtain the first voltage feedback value _Ud and the second voltage in the dq coordinate system Feedback value U _q .

The first adder 102 is connected to the coordinate transformation unit 101, and is used for calculating the first voltage feedback value _Ud and the preset first load voltage value _Ud ^* , and outputting a first calculation result.

The first PIR controller 103 is connected to the first adder 102, and is used for performing PIR control on the first calculation result and outputting a first compensation AC amount.

The second adder 104 is connected to the coordinate transformation unit 101 and is used for calculating the second voltage feedback value U _q and the preset second load voltage value U _q ^* , and outputting a second calculation result.

The second PIR controller 105 is connected to the second adder 104, and is used for performing PIR control on the second calculation result, and outputting a second compensation AC amount.

The inverse coordinate transformation unit 106 is connected to the first PIR controller 103 and the second PIR controller 105, and is used for performing inverse coordinate transformation on the first compensation AC quantity and the second compensation AC quantity to obtain a three-phase compensation voltage.

The sinusoidal pulse width modulation unit 107 is connected to the inverse coordinate transformation unit 106 , and is used to perform sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmit the pulse signal to the inverter 20 as a compensation amount.

Through the control device of the inverter output voltage in this embodiment, the equivalent impedance of the specific order of the inverter is reduced by using the PIR control, and the harmonic content of the inverter output voltage caused by the nonlinear load is reduced, and the output Compensation of harmonic voltages, thereby improving the output voltage of inverters feeding non-linear loads. At the same time, only one set of resonance control links needs to be added, compared with the prior art, the control links are reduced, and the implementation is simple.

Preferably, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

Preferably, the transfer functions of the first PIR controller 103 and the second PIR controller 105 are: Among them, s represents the time domain, K _P is the proportional coefficient, K _I is the integral coefficient, K _R is the resonance coefficient, ω _c is the resonance cut-off frequency, and 6ω ₀ is the resonance frequency. The value of the parameter is combined with the stability of the system to reduce the equivalent impedance (or internal resistance) of a specific harmonic as much as possible.

Embodiment Four

Based on the same inventive concept, this embodiment provides another device for controlling the output voltage of an inverter, which can be used to implement the method described in Embodiment 2 above, and the repetition will not be repeated here. The difference between the present embodiment and the third embodiment is that the third embodiment adopts a single voltage outer loop control, and this embodiment adopts a double-loop control of the voltage outer loop and the current inner loop.

As shown in FIG. 7, the control device 200 of the inverter output voltage includes: a first coordinate transformation unit 201, a first adder 202, a first PIR controller 203, a second adder 204, a second PIR controller 205, The second coordinate transformation unit 206 , the third adder 207 , the third PIR controller 208 , the fourth adder 209 , the fourth PIR controller 210 , the inverse coordinate transformation unit 211 , and the sinusoidal pulse width modulation unit 212 . Its structure is described in detail below.

The first coordinate transformation unit 201 is connected to the input terminal of the load 10, and is used for coordinate transformation of the three-phase output voltage output from the inverter 20 to the load 10, to obtain the first voltage feedback value _Ud and the second voltage feedback value Ud in the dq coordinate system Two voltage feedback value U _q .

The first adder 202 is connected to the first coordinate transformation unit 201, and is used for calculating the first voltage feedback value _Ud and the preset first load voltage value _Ud ^* , and outputting a first calculation result.

The first PIR controller 203, connected to the first adder 202, is used to perform PIR control on the first calculation result, and output it as a first given current value _Id ^* .

The second adder 204 is connected to the first coordinate transformation unit 201 and is used for calculating the second voltage feedback value U _q and the preset second load voltage value U _q ^* , and outputting a second calculation result.

The second PIR controller 205 is connected to the second adder 204, and is used for performing PIR control on the second calculation result, and outputting it as a second given current value I _q ^* .

The second coordinate transformation unit 206 is connected to the output terminal of the inverter 20, and is used for carrying out coordinate transformation on the three-phase output current of the inverter 20 to obtain the first current feedback value _Id and the second current in the dq coordinate system Feedback value I _q .

The third adder 207, connected to the second coordinate transformation unit 206, is used for calculating the first current feedback value I _d and the first current given value I _d ^* , and outputs a third calculation result.

The third PIR controller 208 is connected to the third adder 207, and is used for performing PIR control on the third calculation result, and outputting the first compensation AC amount.

The fourth adder 209 is connected to the second coordinate transformation unit 206, and is used for calculating the second current feedback value I _q and the second current given value I _q ^* , and outputs a fourth calculation result.

The fourth PIR controller 210 is connected to the fourth adder 209, and is used for performing PIR control on the fourth calculation result and outputting the second compensation AC amount.

The inverse coordinate transformation unit 211 is connected to the third PIR controller 208 and the fourth PIR controller 210, and is used for performing inverse coordinate transformation on the first compensation AC quantity and the second compensation AC quantity to obtain the three-phase compensation voltage.

The sinusoidal pulse width modulation unit 212 is connected to the inverse coordinate transformation unit 211 , and is used to perform sinusoidal pulse width modulation on the three-phase compensation voltage to obtain a pulse signal, and transmit the pulse signal to the inverter 20 as a compensation amount.

Through the control device of the inverter output voltage in this embodiment, the equivalent impedance of the specific order of the inverter is reduced by using the PIR control, and the harmonic content of the inverter output voltage caused by the nonlinear load is reduced, and the output Compensation of harmonic voltages, thereby improving the output voltage of inverters feeding non-linear loads. At the same time, only one set of resonance control links needs to be added, compared with the prior art, the control links are reduced, and the implementation is simple. Moreover, using the control method of the voltage outer loop and the current inner loop can not only improve the voltage, but also stabilize the current.

Preferably, both the first load voltage value U _d ^* and the first load voltage value U _q ^* are DC quantities.

Preferably, the transfer functions of the first PIR controller 203, the second PIR controller 205, the third PIR controller 208 and the fourth PIR controller 210 are: Among them, s represents the time domain, K _P is the proportional coefficient, K _I is the integral coefficient, K _R is the resonance coefficient, ω _c is the resonance cut-off frequency, and 6ω ₀ is the resonance frequency.

As used above, the term "unit" may be a combination of software and/or hardware that realizes a predetermined function. Although the systems described in the following embodiments are preferably implemented in software, implementations in hardware, or a combination of software and hardware are also possible and contemplated.

Embodiment five

In this embodiment, on the basis of the three-loop control of the fundamental wave, a six-order resonance control link is added, and a voltage outer loop control method is adopted to realize harmonic compensation based on PIR control. The traditional harmonic suppression method is mainly based on the PI regulator in the positive sequence synchronous rotating coordinate system, but the control bandwidth of the PI regulator is limited, and the PIR control method combining the traditional PI regulator and the resonant regulator is introduced into the control strategy , through the resonance controller of a specific order, the loop gain is increased, the specific harmonic is eliminated, and the harmonic impedance is reduced. Not only can the output harmonic voltage be compensated, but only one set of resonance control links needs to be added. Compared with the prior art, the control links are reduced and the implementation is simple.

Fig. 8 is a schematic diagram of controlling the output voltage of the inverter according to Embodiment 5 of the present invention. As shown in Fig. 8, the relevant structure of the inverter is the same as that in Fig. 1, U _a , U _b , and U _c are the output voltages of the inverter, For the fundamental wave link, the voltage outer loop control is adopted, U _d ^* and U _q ^* are the given values of the load voltage outer loop in the dq rotating coordinate system, U _d and U _q are the corresponding voltage feedback values, which are calculated by the adder and After the PIR controller, the 6th harmonic AC quantity that needs to be compensated is output, and after inverse coordinate transformation and sinusoidal pulse width modulation, it is used as the inverter pulse input. ωt represents the rotation angle. In this embodiment, the output voltage of the inverter can be improved through single-voltage outer-loop control.

Embodiment six

In this embodiment, on the basis of fundamental three-loop control, six resonance control links are added, and a double-loop control method of voltage outer loop and current inner loop is adopted to realize harmonic compensation based on PIR control.

_Fig . 9 is _{a schematic diagram} of controlling the output _voltage of the _inverter according to the sixth embodiment of the present invention. The output voltage of the device, for the fundamental link, the double-loop control of the voltage outer loop and the current inner loop is adopted. U _d ^* and U _q ^* are the given values of the load voltage outer loop in the dq rotating coordinate system, and U _d and U _q are the corresponding The voltage feedback value is calculated by the adder and the given value I _d ^* and I _q ^* of the current loop after being calculated by the adder and the PIR controller. After the inverter side current is sampled, it is transformed into the rotating coordinate system, and I _d and I _q are obtained as the current The feedback value of the loop is also calculated by the adder and the PIR proportional integral resonant controller to output the 6th harmonic AC value that needs to be compensated. After inverse coordinate transformation and sinusoidal pulse width modulation, it is used as the inverter pulse input. ωt represents the rotation angle. In this embodiment, the output voltage of the inverter can be improved and the current can be stabilized at the same time through the double-loop control of the voltage outer loop and the current inner loop.

It can be known from Embodiment 5 and Embodiment 6 that the loop gain is increased through the resonance controller of a specific order, the specific harmonic is eliminated, and the harmonic impedance is reduced. Only one set of resonance control links needs to be added, which reduces the number of control links compared with the prior art, and simply and effectively realizes the compensation for the harmonic output voltage of the inverter caused by the nonlinear load.

Any process or method descriptions described in flowcharts or otherwise herein may be understood as representing a module, segment or portion of code comprising one or more executable instructions for implementing specific logical functions or steps of the process , and the scope of preferred embodiments of the invention includes alternative implementations in which functions may be performed out of the order shown or discussed, including in substantially simultaneous fashion or in reverse order depending on the functions involved, which shall It is understood by those skilled in the art to which the embodiments of the present invention pertain.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. the control method of an inverter output voltage, it is characterised in that including:

Inverter is exported and carries out coordinate transform to the three-phase output voltage of load, obtain the first voltage feedback value U under dq coordinate system_dWith the second voltage feedback value U_q;

Utilize first adder to described first voltage feedback value U_dWith the first default load voltage values U_d ^*It is calculated, exports the first result of calculation, described first result of calculation is carried out proportional integral resonance PIR and controls, output the first compensation of ac;

Utilize second adder to described second voltage feedback value U_qWith the second default load voltage values U_q ^*It is calculated, exports the second result of calculation, described second result of calculation is carried out PIR control, output the second compensation of ac;

Compensate of ac to described first and described second compensation of ac carries out anti-coordinate transform, obtain three-phase compensation voltages, described three-phase compensation voltages is carried out sinusoidal pulse width modulation, obtains pulse signal, described pulse signal is transferred to described inverter as compensation dosage.

2. method according to claim 1, it is characterised in that described first load voltage values U_d ^*With described first load voltage values U_q ^*It is DC quantity.

3. the control method of an inverter output voltage, it is characterised in that including:

Inverter is exported and carries out coordinate transform to the three-phase output voltage of load, obtain the first voltage feedback value U under dq coordinate system_dWith the second voltage feedback value U_q;

Utilize first adder to described first voltage feedback value U_dWith the first default load voltage values U_d ^*It is calculated, exports the first result of calculation, described first result of calculation is carried out proportional integral resonance PIR and controls, output it as the first given value of current value I_d ^*;

Utilize second adder to described second voltage feedback value U_qWith the second default load voltage values U_q ^*It is calculated, exports the second result of calculation, described second result of calculation is carried out PIR control, output it as the second given value of current value I_q ^*;

The three-phase output electric current of described inverter is carried out coordinate transform, obtains the first current feedback values I under dq coordinate system_dWith the second current feedback values I_q;

Utilize the 3rd adder to described first current feedback values I_dWith described first given value of current value I_d ^*It is calculated, exports the 3rd result of calculation, described 3rd result of calculation is carried out PIR control, output the first compensation of ac;

Utilize the 4th adder to described second current feedback values I_qWith described second given value of current value I_q ^*It is calculated, exports the 4th result of calculation, described 4th result of calculation is carried out PIR control, output the second compensation of ac;

Compensate of ac to described first and described second compensation of ac carries out anti-coordinate transform, obtain three-phase compensation voltages, described three-phase compensation voltages is carried out sinusoidal pulse width modulation, obtains pulse signal, described pulse signal is transferred to described inverter as compensation dosage.

4. method according to claim 3, it is characterised in that described first load voltage values U_d ^*With described first load voltage values U_q ^*It is DC quantity.

5. the control device of an inverter output voltage, it is characterised in that including:

Coordinate transformation unit, carries out coordinate transform for inverter is exported to the three-phase output voltage of load, obtains the first voltage feedback value U under dq coordinate system_dWith the second voltage feedback value U_q;

First adder, for described first voltage feedback value U_dWith the first default load voltage values U_d ^*It is calculated, exports the first result of calculation;

First PIR controller, for described first result of calculation being carried out PIR control, output the first compensation of ac;

Second adder, for described second voltage feedback value U_qWith the second default load voltage values U_q ^*It is calculated, exports the second result of calculation;

Second PIR controller, for described second result of calculation being carried out PIR control, output the second compensation of ac;

Anti-coordinate transformation unit, carries out anti-coordinate transform for compensating of ac and described second compensation of ac to described first, obtains three-phase compensation voltages;

Sinusoidal pulse width modulation unit, for described three-phase compensation voltages is carried out sinusoidal pulse width modulation, obtains pulse signal, as compensation dosage, described pulse signal is transferred to described inverter.

6. device according to claim 5, it is characterised in that described first load voltage values U_d ^*With described first load voltage values U_q ^*It is DC quantity.

7. device according to claim 5, it is characterised in that the transmission function of described first PIR controller and described second PIR controller is: $G_C\left(s\right)=G_{\mathrm{PIR}}\left(s\right)=K_P+\frac{K_1}{s}+\frac{{2K}_R{\mathrm{\ω}}_{c}s}{s^2+{2\mathrm{\ω}}_{c}s+{\left({6\mathrm{\ω}}_0\right)}^2},$ Wherein, s represents time domain, K_PFor proportionality coefficient, K_IFor integral coefficient, K_RFor resonance coefficient, ω_cFor resonance cut-off frequency, 6 ω₀For resonant frequency.

8. the control device of an inverter output voltage, it is characterised in that including:

First coordinate transformation unit, carries out coordinate transform for inverter is exported to the three-phase output voltage of load, obtains the first voltage feedback value U under dq coordinate system_dWith the second voltage feedback value U_q;

First adder, for described first voltage feedback value U_dWith the first default load voltage values U_d ^*It is calculated, exports the first result of calculation;

First PIR controller, for described first result of calculation is carried out PIR control, outputs it as the first given value of current value I_d ^*;

Second adder, for described second voltage feedback value U_qWith the second default load voltage values U_q ^*It is calculated, exports the second result of calculation;

Second PIR controller, for described second result of calculation is carried out PIR control, outputs it as the second given value of current value I_q ^*;

Second coordinate transformation unit, carries out coordinate transform for the three-phase of described inverter is exported electric current, obtains the first current feedback values I under dq coordinate system_dWith the second current feedback values I_q;

3rd adder, for described first current feedback values I_dWith described first given value of current value I_d ^*It is calculated, exports the 3rd result of calculation;

3rd PIR controller, for described 3rd result of calculation being carried out PIR control, output the first compensation of ac;

4th adder, for described second current feedback values I_qWith described second given value of current value I_q ^*It is calculated, exports the 4th result of calculation;

4th PIR controller, for described 4th result of calculation being carried out PIR control, output the second compensation of ac;

Anti-coordinate transformation unit, carries out anti-coordinate transform for compensating of ac and described second compensation of ac to described first, obtains three-phase compensation voltages;

Sinusoidal pulse width modulation unit, for described three-phase compensation voltages is carried out sinusoidal pulse width modulation, obtains pulse signal, as compensation dosage, described pulse signal is transferred to described inverter.

9. device according to claim 8, it is characterised in that described first load voltage values U_d ^*With described first load voltage values U_q ^*It is DC quantity.

10. device according to claim 8, it is characterised in that the transmission function of described first PIR controller, described second PIR controller, described 3rd PIR controller and described 4th PIR controller is: $G_C\left(s\right)=G_{\mathrm{PIR}}\left(s\right)=K_P+\frac{K_1}{s}+\frac{{2K}_R{\mathrm{\ω}}_{c}s}{s^2+{2\mathrm{\ω}}_{c}s+{\left({6\mathrm{\ω}}_0\right)}^2},$ Wherein, s represents time domain, K_PFor proportionality coefficient, K_IFor integral coefficient, K_RFor resonance coefficient, ω_cFor resonance cut-off frequency, 6 ω₀For resonant frequency.