阅读说明：本技术 基于pi和重复控制的单相逆变器控制方法、系统及逆变器 (Single-phase inverter control method and system based on PI and repetitive control and inverter ) 是由 曾勇杰 龚伟 罗宪禄 于 2021-07-09 设计创作，主要内容包括：本发明提供一种基于PI和重复控制的单相逆变器控制方法、系统及逆变器,该方法包括：采集单相逆变器的输出电流与输出电压；利用二阶广义积分对输出电流、输出电压进行重构,生成正交虚拟量；将正交虚拟量进行旋转坐标变换,得到矢量信号,将矢量信号经旋转坐标变化解耦成直流信号；调整直流信号与参考电压之间的第一误差电压,对第一误差电压与直流信号叠加后进行坐标反变换得到第一控制信号；基于第二误差电压利用重复控制器得到误差校准信号；对误差校准信号与第一控制信号进行第叠加,得到第二控制信号,利用电流负载前馈补偿控制输出的控制信号与第二控制信号再次叠加生成第三控制信号；调制第三控制信号产生控制单相逆变器输出电压的SPWM脉冲。(The invention provides a single-phase inverter control method, a system and an inverter based on PI and repetitive control, wherein the method comprises the following steps: collecting output current and output voltage of a single-phase inverter; reconstructing output current and output voltage by using second-order generalized integral to generate orthogonal virtual quantity; performing rotation coordinate transformation on the orthogonal virtual quantity to obtain a vector signal, and decoupling the vector signal into a direct current signal through rotation coordinate transformation; adjusting a first error voltage between the direct current signal and a reference voltage, superposing the first error voltage and the direct current signal, and then performing coordinate inverse transformation to obtain a first control signal; obtaining an error calibration signal by using a repetitive controller based on the second error voltage; performing first superposition on the error calibration signal and the first control signal to obtain a second control signal, and performing second superposition on the control signal output by current load feedforward compensation control to generate a third control signal; modulating the third control signal generates SPWM pulses that control the output voltage of the single-phase inverter.)

1. A single-phase inverter control method based on PI and repetitive control is characterized by comprising the following steps:

collecting output current and output voltage of a single-phase inverter;

reconstructing the output current and the output voltage by using second-order generalized integral to generate orthogonal virtual quantity which has a phase difference of 90 degrees with the output current and the output voltage;

performing rotation coordinate transformation on the orthogonal virtual quantity to obtain a vector signal of a virtual axis, and decoupling the vector signal into a direct current signal through rotation coordinate change;

adjusting a first error voltage between the direct current signal and a reference voltage by using a voltage closed-loop PI controller, and generating a first control signal which is a sinusoidal signal by performing coordinate inverse transformation after the first error voltage and the direct current signal are superposed;

obtaining a corresponding error calibration signal by using a repetitive controller based on the second error voltage;

performing second superposition on the error calibration signal and the first control signal to obtain a second control signal, and performing second superposition on the control signal output by current load feedforward compensation control to generate a third control signal;

and modulating the third control signal by using an SPWM algorithm to generate SPWM pulses for controlling the output voltage of the single-phase inverter.

2. The PI and repetitive control based single phase inverter control method according to claim 1, further comprising: reconstructing the output current and the output voltage respectively through a generalized second-order integrator to generate a virtual axis lagging by a phase of 90 degrees, wherein the corresponding transfer function is as follows:

in the formula of U_α(s) is an alpha-axis orthogonal voltage component in an alpha-beta coordinate system, U_βAnd(s) is a beta axis orthogonal voltage component in an alpha beta coordinate system, and omega is a resonance angular frequency.

3. The PI and repetitive control based single phase inverter control method of claim 1 wherein the control signals output by the current load feed forward compensation control comprise a load feed forward current signal and a feedback inductor current signal.

4. The PI and repetitive control based single phase inverter control method according to claim 1 or 2, further comprising: in voltage outer loop control, a periodic signal of any waveform is constructed by using a repetitive control algorithm to carry out harmonic non-static tracking, so that the output impedance of each harmonic frequency is reduced to correct and optimize the harmonic waveform.

5. The PI and repetitive control based single phase inverter control method of claim 4 further comprising: and determining a periodic rule of a harmonic generation dead zone by using a repetitive control algorithm, and feeding back in advance according to the periodic rule to relieve the dead zone effect.

6. The PI and repetitive control based single phase inverter control method of claim 4 further comprising: filtering a high-frequency signal in a repetitive control algorithm by using a low-pass filter compensator to ensure the stability of harmonic output by the repetitive control algorithm, wherein the transfer function of the low-pass filter compensator is;

in the formula，ω₀For the cut-off frequency of the LC filter system, epsilon is a constant, g(s) is a second order system of the low pass filter, and s is the laplace transform time domain.

7. The PI and repetitive control based single phase inverter control method according to claim 1, further comprising:

a periodic signal with any waveform is constructed by using a repetitive control algorithm to carry out harmonic non-static tracking, and the output impedance of each harmonic frequency is reduced;

suppressing current mutation caused by load conversion by using a load current compensation controller, reducing the relative impedance output by the inverter, and obtaining the impedance transfer function output by the current inverter;

in the formula, K_mAs a modulation model of the inverter, G_IF(s) is the transfer function of the load current feedback controller, G₁(s) is

G₂(s) is

8. The PI and repetitive control based single phase inverter control method according to claim 1, further comprising:

and selecting corresponding parameters by using the RCD rectification type load to test the inverter to obtain the output harmonic waveform.

9. A single-phase inverter control system based on PI and repetitive control, comprising:

the acquisition module is used for acquiring the output current and the output voltage of the single-phase inverter;

the reconstruction module is used for reconstructing the output current and the output voltage by using second-order generalized integral to generate orthogonal virtual quantity with the phase difference of 90 degrees between the output current and the output voltage;

the coordinate transformation module is used for performing rotary coordinate transformation on the orthogonal virtual quantity to obtain a vector signal of a virtual axis, and decoupling the vector signal into a direct current signal through rotary coordinate change;

the voltage outer ring PI vector controller is used for adjusting a first error voltage between the direct current signal and a reference voltage, and generating a first control signal which is a sinusoidal signal by performing coordinate inverse transformation after the first error voltage and the direct current signal are superposed;

the error calibration module is used for obtaining a corresponding error calibration signal by utilizing the repetitive controller based on the second error voltage;

the repeated control module is used for carrying out second superposition on the error calibration signal and the first control signal to obtain a second control signal;

the current inner loop controller is used for generating a third control signal by superposing the control signal output by current load feedforward compensation control and the second control signal again;

and the pulse signal generation module is used for modulating the third control signal by using an SPWM algorithm to generate an SPWM pulse for controlling the output voltage of the single-phase inverter.

10. An inverter, characterized in that it comprises a single-phase inverter control system based on PI and repetitive control according to claim 9.

Technical Field

The invention relates to the technical field of power control, in particular to a control method and a control system of a single-phase full-bridge inverter based on PI and repetitive control and the inverter.

Background

With the rapid development of modern science and technology, various electric equipment puts higher and higher requirements on the power supply quality, the system capacity and the power supply reliability of a power supply system, and the use of an inverter to meet the requirements of the power supply system is a conventional means, wherein a single-phase inverter has relatively strong adaptability to resistive load equipment, and most of electric equipment in life and industry is nonlinear load equipment.

However, the conventional inverter control system usually selects a PI controller, and uses a sinusoidal signal as a reference of output voltage to automatically adjust and output the sinusoidal signal through the PI controller, and according to the internal model principle, the conventional PI controller cannot track an alternating current signal without static error; meanwhile, the control algorithm of the inverter is not good enough, so that the harmonic content of the output voltage of the inverter is high, electricity waste, equipment heating and equipment service life reduction are caused easily, and even more serious safety accidents can be caused.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide a method, a system and an inverter for controlling a single-phase full-bridge inverter based on PI and repetitive control, which are used to solve the problem that no static error tracking of an ac signal cannot be performed during the control of the single-phase full-bridge inverter in the prior art.

To achieve the above and other related objects, the present invention provides in a first aspect a method for controlling a single-phase inverter based on PI and repetitive control, comprising:

collecting output current and output voltage of a single-phase inverter;

reconstructing the output current and the output voltage by using second-order generalized integral to generate orthogonal virtual quantity which has a phase difference of 90 degrees with the output current and the output voltage;

performing rotation coordinate transformation on the orthogonal virtual quantity to obtain a vector signal of a virtual axis, and decoupling the vector signal into a direct current signal through rotation coordinate change;

adjusting a first error voltage between the direct current signal and a reference voltage by using a voltage closed-loop PI controller, and generating a first control signal which is a sinusoidal signal by performing coordinate inverse transformation after the first error voltage and the direct current signal are superposed;

obtaining a corresponding error calibration signal by using a repetitive controller based on the second error voltage;

performing second superposition on the error calibration signal and the first control signal to obtain a second control signal, and performing second superposition on the control signal output by current load feedforward compensation control to generate a third control signal;

and modulating the third control signal by using an SPWM algorithm to generate SPWM pulses for controlling the output voltage of the single-phase inverter.

The present invention provides in a second aspect a PI and repetitive control based single phase inverter control system comprising:

the acquisition module is used for acquiring the output current and the output voltage of the single-phase inverter;

the reconstruction module is used for reconstructing the output current and the output voltage by using second-order generalized integral to generate orthogonal virtual quantity with the phase difference of 90 degrees between the output current and the output voltage;

the coordinate transformation module is used for performing rotary coordinate transformation on the orthogonal virtual quantity to obtain a vector signal of a virtual axis, and decoupling the vector signal into a direct current signal through rotary coordinate change;

the voltage outer ring PI vector controller is used for adjusting a first error voltage between the direct current signal and a reference voltage, and generating a first control signal which is a sinusoidal signal by performing coordinate inverse transformation after the first error voltage and the direct current signal are superposed;

the error calibration module is used for obtaining a corresponding error calibration signal by utilizing the repetitive controller based on the second error voltage;

the repeated control module is used for carrying out second superposition on the error calibration signal and the first control signal to obtain a second control signal;

the current inner loop controller is used for generating a third control signal by superposing the control signal output by current load feedforward compensation control and the second control signal again;

and the pulse signal generation module is used for modulating the third control signal by using an SPWM algorithm to generate an SPWM pulse for controlling the output voltage of the single-phase inverter.

The present invention provides in a third aspect an inverter comprising the above PI and repetitive control based single phase inverter control system.

As described above, the control method, the control system and the inverter of the single-phase full-bridge inverter based on PI and repetitive control according to the present invention have the following advantages:

the method is based on the vector control idea of coordinate transformation and combines a generalized second-order integral algorithm to construct a single-phase inverter voltage and current virtual axis, and utilizes coordinate transformation to decouple feedback alternating current signals through a control strategy of combining voltage and current double closed-loop PI control with a repetitive control principle, so that the phase amplitude of the alternating current signals is separated, the frequency modulation and amplitude modulation functions can be realized, and the amplitude can be used as a constant reference signal which is fixed and unchanged, thereby realizing the non-static tracking of a PI control mode.

Drawings

FIG. 1 shows a flow chart of a control method of a single-phase full-bridge inverter based on PI and repetitive control provided by the invention;

FIG. 2 is a diagram illustrating an inverter output model according to the present invention;

FIG. 3 is a graph showing the variation of the output impedance of an inverter according to the present invention;

FIG. 4 is a diagram illustrating an outer loop control structure of the inverter voltage according to the present invention;

FIG. 5 is a diagram illustrating the effect of a generalized second-order integral provided by the present invention;

FIG. 6 is a diagram illustrating the effect of coordinate transformation provided by the present invention;

FIG. 7 shows a graph of a repetitive control algorithm provided for the present invention;

FIG. 8 is a schematic diagram of an inverter control system according to the present invention;

fig. 9 shows a structure diagram of an RCD rectifying type load provided by the present invention;

fig. 10 is a graph showing a comparison of simulation effects of PI + repetitive control and PI control for an inverter according to the present invention;

fig. 11 shows a block diagram of a control system of a single-phase full-bridge inverter based on PI and repetitive control according to the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.

It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.

Referring to fig. 1, a single-phase inverter control method based on PI and repetitive control is provided for the present invention, including:

step S1, collecting the output current and output voltage of the single-phase inverter;

the output voltage of the single-phase inverter can be collected by the voltage sampling circuit, and the output current of the single-phase inverter can be collected by the current sampling circuit, for example, the output current of the single-phase inverter is collected by the current sensor, and the output voltage of the single-phase inverter is collected by the voltage sensor.

Step S2, reconstructing the output current and the output voltage by using second-order generalized integral to generate orthogonal virtual quantity with the phase difference of 90 degrees between the output current and the output voltage;

for example, the output current and the output voltage are reconstructed by a generalized second-order integrator to generate a virtual axis with a phase lag of 90 degrees, and the corresponding transfer function is:

in the formula of U_α(s) is an alpha-axis orthogonal voltage component in an alpha-beta coordinate system, U_βAnd(s) is a beta axis orthogonal voltage component in an alpha beta coordinate system, and omega is a resonance angular frequency.

For another example, the second-order generalized integral phase-locked loop decomposition method can be used for performing second-order generalized integral phase-locked loop decomposition on the acquired output current to obtain two paths of orthogonal currents, and performing second-order generalized integral phase-locked loop decomposition on the output voltage to obtain two paths of orthogonal voltages.

The second-order generalized integrator is adopted to reconstruct the output voltage and the output current, so that the orthogonal component with the phase delay of 90 degrees is virtualized, and the problems of poor filtering delay and dynamic response capability and the like in the construction of orthogonal virtual signals in the traditional method are solved. The second-order generalized integrator reconstruction method is adopted to construct the orthogonal virtual quantity and simultaneously carry out adaptive filtering on the acquired quantity, so that the anti-interference capability of the system is improved. The constructed orthogonal virtual quantity can realize dq axis decoupling control, provides a foundation for a subsequent phase-locked loop and eliminates the influence of adverse factors such as direct current components on phase-locked precision. In addition, the second-order generalized integrator or the second-order generalized integral phase-locked loop comprises 2 cascaded integrators to form a loop, so that a frequency-adjustable oscillator is formed, signals can be quickly and accurately tracked, and input signal noise and distortion are well inhibited.

Step S3, performing rotation coordinate transformation on the orthogonal virtual quantity to obtain a vector signal of a virtual axis, and decoupling the vector signal into a direct current signal through rotation coordinate transformation;

the orthogonal virtual quantity comprises two paths of orthogonal currents or/and two paths of orthogonal voltages, the two paths of orthogonal currents are subjected to rotation coordinate transformation to obtain d-axis currents and q-axis currents, and the two paths of orthogonal voltages are subjected to rotation coordinate transformation to obtain d-axis voltages and q-axis voltages.

For example, the two orthogonal currents are subjected to rotation coordinate transformation to obtain d-axis current and q-axis current of the DQ axis. And performing rotation coordinate transformation on the two paths of orthogonal voltages to obtain d-axis voltage and q-axis voltage of a DQ axis. Namely, the variables Va and Vb in the stationary coordinate system are converted into the variables DQ in the rotating coordinate system by using coordinate transformation, wherein in order to meet the condition of coordinate transformation, the supplementary 0 variable participates in the coordinate transformation.

For another example, a state equation of the system under a d-q coordinate system is listed (a single-phase inverter d-q model is based on a d-q rotating coordinate system), output voltage and load current of the single-phase inverter are subjected to feedforward decoupling, an inverter controller (voltage current) double-loop PI control model is established, for example, a voltage outer loop respectively performs PI control on the voltage, and output reference current values Id and Iq provide control quantity required by a current inner loop; the inner ring performs PI control on the current on the alternating current side according to the value given by the outer ring, decoupling of voltage and current is achieved, alternating current voltage signals (vector signals) are decoupled into direct current quantity in a vector control mode, and the decoupled quantity can achieve static error-free tracking of the PI control on the signals.

Step S4, adjusting a first error voltage between the direct current signal and a reference voltage by using a voltage closed loop PI controller, and generating a first control signal which is a sine signal by performing coordinate inverse transformation after the first error voltage and the direct current signal are superposed;

specifically, as shown in fig. 4, in the voltage closed-loop control, the dc signal is the d-axis voltage U_dAnd q-axis voltage U_qThe reference voltages corresponding to the d-axis voltage and the q-axis voltage are respectivelyWherein, two voltage closed-loop PI controllers are adopted, the first voltage closed-loop PI controller is used for adjusting the direct current voltage U_dAnd a reference voltageA first error voltage between, a second voltage closed loop PI controller for regulating the DC voltage U_qAnd a reference voltageBetweenThe two first error voltages are respectively superposed with the corresponding direct current signals, and then coordinate inverse transformation is carried out to obtain a first control signal which is a sinusoidal signal.

Step S5, obtaining a corresponding error calibration signal by using a repetitive controller based on the second error voltage;

wherein, as shown in fig. 4, the second error voltage is an ac voltage U output by the inverter₀The voltage signal which is corrected and output by taking commercial power (220V, 50HZ) as reference is subjected to harmonic non-static tracking by taking second error voltage as input and constructing a periodic signal with any waveform by using a repetitive control algorithm in voltage outer loop control, so that the output impedance of each harmonic frequency is reduced to correct and optimize the harmonic waveform, and the harmonic compensation function is realized; meanwhile, a periodic rule of harmonic generation dead zones is determined by using a repetitive control algorithm, and feedback is made in advance according to the periodic rule to relieve the dead zone effect, for example, the condition that the dead zone effect exists in dead zone time can cause a large amount of harmonic components introduced into output to change periodically.

Step S6, performing a second superposition on the error calibration signal and the first control signal to obtain a second control signal, and generating a third control signal by superposing the control signal output by current load feedforward compensation control and the second control signal again;

it should be noted that the control signal output by the current load feedforward compensation control includes a load feedforward current signal and a feedback inductor current signal i_L(obtained by sampling with a current sensor); superposing an error calibration signal with a harmonic compensation function on the basis of the first control signal to obtain a second control signal, and feeding back an inductive current signal i through a current load feedforward compensation controller (namely, a current inner loop control PI)_LAnd the second control signal and the third control signal are mutually superposed to obtain a third control signal.

By the mode, voltage and current double-loop PI control is realized, and a control strategy of a repetitive control principle is combined, so that the problem that static error-free tracking cannot be carried out on an alternating current signal by the PI control mode is solved.

And step S7, modulating the third control signal by using an SPWM algorithm to generate SPWM pulses for controlling the output voltage of the single-phase inverter.

And obtaining an optimized driving signal of the inverter full-bridge IGBT through an SPWM algorithm.

Specifically, a waveform control strategy algorithm aiming at improving the adaptability of a single-phase full-bridge inverter to a nonlinear load is provided, a coordinate transformation principle, a generalized second-order integral principle, a voltage-current double closed-loop PI control theory and a repetitive control theory are used, and a filter output characteristic of the inverter and a design scheme of a load current feedforward compensation controller are combined.

For example, a PI controller is usually selected for a conventional inverter control system, and a sinusoidal signal is used as a reference of an output voltage and is automatically adjusted and output by the PI controller, but according to an internal model principle, the conventional PI controller cannot complete tracking of an alternating current signal without a static error, as frequency increases, gain gradually decreases to 0, and 50HZ gain is very small, so that the PI controller can only complete tracking of a constant without a static error, and tracking of the sinusoidal alternating current signal has a certain phase difference, and thus a conventional PI control method using the alternating current signal as a reference cannot be applied to the field of high-precision inverter control.

Aiming at the problem that the traditional PI control mode cannot track alternating current signals without static error, in the embodiment, a single-phase inverter voltage and current virtual axis is constructed by combining a vector control idea based on coordinate transformation with a generalized second-order integration algorithm, a control strategy of combining voltage and current double closed-loop PI control with a repetitive control principle is adopted, feedback alternating current signals are decoupled through coordinate transformation, and then phase amplitude values of the alternating current signals are separated, so that the frequency modulation and amplitude modulation functions can be achieved, and the amplitude values can be used as constant reference signals which are fixed and unchangeable, so that the static error-free tracking of the PI control mode is achieved.

In another embodiment, the inverter has an LC filter circuit, as shown in the inverter output model of fig. 2, and the inverter output transfer function is:

wherein L is inductance, r is resistance, C is capacitance, U₀Is a voltage, i₀For the load current, the output presents an output impedance that varies with the system frequency, as shown by the inverter output impedance in fig. 3, i₀When it is equal to 0, the no-load transfer function is represented by G_Z(s) is expressed as:

for example, when dealing with inrush currents, a high voltage difference is generated at the resonant frequency due to the output impedance, resulting in distortion of the output voltage waveform. In addition, the switching device has an unavoidable dead-zone effect in the switching process, so that a large amount of harmonic waves are introduced, the aim of introducing repetitive control is to design for suppressing periodic interference such as nonlinear load and the dead-zone effect, and the adaptive capacity of the inverter power supply to the nonlinear load is improved.

Referring to fig. 4, a structure diagram of an outer ring control structure of an inverter voltage according to the present invention is detailed as follows:

and vector control is combined with a PI control and repetitive control algorithm to carry out correction control on the output voltage waveform of the inverter, and a load current feedforward controller is arranged for reducing output impedance.

The inverter generates optimized IGBT full-bridge PWM driving signals through a control algorithm after transmitting voltage and current signals of output alternating current sampled by a voltage sensor and a current sensor into the MCU for correction processing, obtains pulse alternating current voltage after full-bridge inversion, and obtains smooth sine alternating current voltage through a filter circuit.

In the whole control algorithm, the corrected voltage and current data are divided into two processes for algorithm processing, in the first part, a virtual axis with lag pi/2 phase is generated in a generalized second-order integration mode, and the transfer function is as follows:

in the formula of U_α(s) is an alpha-axis orthogonal voltage component in an alpha-beta coordinate system, U_βAnd(s) is a beta axis orthogonal voltage component in an alpha beta coordinate system, and omega is a resonance angular frequency. Firstly, generalized second-order integration realizes real-time virtual axis generation by outputting an alternating current signal with frequency omega in a lagging pi/2 phase, the simulation effect is shown as the generalized second-order integration effect in fig. 5, and secondly, a corresponding rotation vector signal is generated through coordinate transformation, and the change matrix isThe AC signal is shown in the coordinate transformation effect diagram of FIG. 6Decoupled through rotation coordinate changeThe direct current signal enters a double closed loop PI controller for calculation, and then a corresponding control voltage signal is obtained through coordinate inverse transformation; and in the second part, corresponding error calibration signals are directly obtained through a discrete repetitive controller, real-time control quantity to be output at the next moment is obtained through superposition with control signals of PI, and finally, optimized driving signals of the inverter full-bridge IGBT are obtained through an SPWM algorithm. The PI can not complete the static error-free tracking of the alternating current signal, so that the alternating current voltage signal is decoupled into direct current quantity in a vector control mode, and the decoupled quantity can realize the static error-free tracking of the PI control on the signal.

In other embodiments, please refer to fig. 9, it should be noted that other non-linear loads may also be used for testing, for example, in this embodiment, the RCD rectifying load is a load accompanied by a periodic current surge characteristic, and the surge strength is also increased as the electrolytic capacitor behind the rectifier bridge is increased. In fig. 9, the resistor R is connected to a load for simulating line voltage drop, and the output terminal of the inverter is connected to the RCD rectifierU of load_inAnd selecting proper system parameters to test the inverter, wherein the parameters of the output voltage waveform harmonic index THD can be checked by using a power quality analyzer according to the test standard.

In other embodiments, discrete control is selected as the second part, on one hand, PI control under a rotating coordinate system is considered to attenuate a feedback signal at a high frequency and cannot reflect a real output voltage, so that repetitive control is introduced as harmonic compensation of the feedback voltage, and the second reason is that an inevitable output impedance occurs at an output end of an inverter due to a filter circuit, and when the inverter carries a nonlinear load, a harmonic current generated by the nonlinear load generates a harmonic voltage drop on the output impedance of the inverter. The repetitive control algorithm can construct an internal model of a periodic signal with any waveform, reduce the output impedance at each harmonic frequency, and further realize the correction of the waveform, in addition, the existence of dead time can cause the output to introduce a large amount of harmonic components and present periodic variation, and the influence of the dead time effect can be effectively relieved by using the repetitive control algorithm. The block diagram of the repetitive control algorithm is shown in fig. 7, where N poles on the unit circle of the internal model make the system in a critical stable state, Q value is usually slightly smaller than a constant of 1 in order to enhance system stability, Kr is system gain adjusted according to an actual state, K is a compensation for phase lag generated by g(s) filter, and a low-pass filter compensator g(s) is introduced to enhance the suppression capability of the high-frequency signal so as to keep the system stable, for example, the low-pass filter compensator is used to increase the suppression capability of the repetitive control algorithm on the high-frequency signal so as to ensure inverter system stability, where the transfer function of the low-pass filter compensator is;

in the formula, ω₀The cut-off frequency of the LC filtering system is shown, epsilon is a constant, G(s) is a second-order system of a low-pass filter, and s is a Laplace transform time domain; the epsilon may be 0.707, which is selected to take the filtering effect and the dynamic characteristics into consideration. To avoid outputIf the output is too large, a limiting process is performed before the output. In the embodiment, an incremental error correction signal is obtained by taking the voltage error as an input through a repetitive control algorithm, and considering that the repetitive control is slow in dynamic response and the PI control is poor in steady-state performance, so that the inverter waveform control technology can realize good and bad complementation by a hybrid control mode combining the repetitive control and the PI control, and the robustness of the system is enhanced.

In other embodiments, the control method of the conventional inverter mainly selects PI control, although the PI control has good dynamic regulation performance, the steady-state performance of the PI is poor, and the output impedance of each frequency point cannot be eliminated, so that the PI controlled inverter has poor load carrying capacity for nonlinear load, the output impedance of the inverter at each subharmonic frequency point is reduced to the maximum extent, and the method is a direct and effective method for relieving the distortion of the output voltage of the inverter caused by the nonlinear load. To solve this problem, the present embodiment uses the first way of reducing the output impedance, for example, using a repetitive controller to enhance the steady-state characteristic of the system, the repetitive controller can construct an internal model of the periodic signal of any waveform, and can reduce the output impedance at each harmonic frequency. The method can realize the complementation of advantages and disadvantages by combining PI with repetitive control, when the load works stably, because the steady-state error ratio is smaller at the moment, the repetitive controller can also have the output of control quantity under the condition that the error is zero, and for the condition of load mutation, the control of the repetitive controller can be reflected only after one fundamental wave period, so the dynamic performance of the repetitive control is not good, and the PI control just makes up the defects of the repetitive control. The voltage outer ring can stabilize output voltage, the error between load output voltage and given voltage is reduced to zero, the output of single inverter voltage is essentially reflected in the control of current, and the current inner ring can expand the bandwidth of an inverter control system, so that the dynamic response of the inverter is accelerated, and the harmonic content of the output voltage is reduced. Therefore, the double closed-loop system is largely used in the field of inverter control, but the traditional current closed-loop control directly uses inductive current feedback or load current feedback, and does not have too great influence on the output impedance of the whole system, so that the embodiment uses a second mode of reducing the output impedance and uses a load current feedback compensation controller, the output quantity of the controller can be quickly reflected into the control system, and the voltage waveform distortion caused by the current mutation caused by the load change is restrained. The two ways of reducing the output impedance of the inverter are combined to obtain the design scheme of the inverter controller system.

See in detail FIG. 9, wherein G_RC(s) transfer function of repetitive controller, G_PI(s) represents the transfer function of the PI controller, G_IF(s) represents the transfer function of the load current feedback controller,K_mrepresenting a modulation model of the inverter. Since PI control and repetitive control a number of papers have been described in greater detail, an important explanation of G is provided here_IF(s) design of load current feedback controller.

The load current compensation controller is used for inhibiting the voltage waveform from being distorted due to current mutation caused by load conversion, and the impedance transfer function of the current inverter is obtained:

to minimize Z, let G₂(s)-G₁(s)G₂(s)G_IF(s)K_m0, to satisfy G_IF(s) is a rational expression, and a low-pass filter is connected in series with a path.

In the above formula, tau can be adjusted according to actual conditions, omega₀For the resonant frequency of the LC filter system, the transfer function of the load current feedforward compensation controller can be obtained by combining the above formula:

therefore, the control design scheme of the minimum output impedance of the inverter is obtained, so that the relative impedance of the inverter is greatly reduced.

In other embodiments, please refer to fig. 10-a and fig. 10-b, which are graphs for comparing simulation effects formed by PI + repetitive control and PI control, respectively, the load carrying capacity of the built simulation inverter is compared with that of the RCD load, a (upper part) continuous wave curve in fig. 10 represents a voltage change condition of an input port of the RCD load and is also a voltage change curve of an output end of the inverter, and a (lower part) peak waveform in fig. 10 represents a current of the output end of the inverter, so that the RCD load is a surge current accompanied by a period, and if an inverter control algorithm is not good enough, a waveform distortion rate is very high.

For example, in fig. 10-a, the inverter is controlled by PI + repeatedly, the power quality analyzer is used to check the output voltage waveform harmonic index THD parameter, and the THD of the inverter corresponding to the figure is 2.52%; in fig. 10-b, the inverter is controlled by PI, and the power quality analyzer is used to check the output voltage waveform harmonic index THD parameter, and the THD of the inverter corresponding to the figure is 7.52%.

Referring to fig. 11, a block diagram of a control system of a single-phase full-bridge inverter based on PI and repetitive control according to the present invention includes:

the acquisition module 1 is used for acquiring the output current and the output voltage of the single-phase inverter;

the reconstruction module 2 is used for reconstructing the output current and the output voltage by using second-order generalized integral to generate orthogonal virtual quantity with the phase difference of 90 degrees between the output current and the output voltage;

the coordinate transformation module 3 is used for performing rotary coordinate transformation on the orthogonal virtual quantity to obtain a vector signal of a virtual axis, and decoupling the vector signal into a direct current signal through rotary coordinate change;

the voltage outer ring PI vector controller 4 is used for adjusting a first error voltage between the direct current signal and a reference voltage, and generating a first control signal which is a sinusoidal signal by performing coordinate inverse transformation after the first error voltage and the direct current signal are superposed;

the error calibration module 5 is used for obtaining a corresponding error calibration signal by utilizing the repetitive controller based on the second error voltage;

the repetitive control module 6 is configured to perform second superposition on the error calibration signal and the first control signal to obtain a second control signal;

the current inner loop controller 7 is used for generating a third control signal by superposing the control signal output by current load feedforward compensation control and the second control signal again;

and the pulse signal generation module 8 modulates the third control signal by using an SPWM algorithm to generate an SPWM pulse for controlling the output voltage of the single-phase inverter.

It should be noted that the control system of the single-phase full-bridge inverter based on PI and repetitive control and the control method of the single-phase full-bridge inverter based on PI and repetitive control are in a one-to-one correspondence, and please refer to the above control method for the technical details, technical solutions and technical effects of the control system of the single-phase full-bridge inverter based on PI and repetitive control, which is not described herein.

In other embodiments, an inverter is also provided, and the inverter comprises the single-phase inverter control system based on PI and repetitive control.

Specifically, the inverter is at least one processor; and a memory communicatively connected to the processor, the memory storing instructions executable by the processor, the instructions being executable by the processor to enable the processor to perform the method of controlling the single-phase inverter, the processor and the memory being connectable by a bus or other means.

The memory, which is a non-volatile computer-readable storage medium, may be used to store a non-volatile software program, a non-volatile computer-executable program, and modules, such as program instructions/modules corresponding to the control method of the single-phase inverter in the embodiments of the present application, for example, the processor executes various functional applications and data processing of the server by running the non-volatile software program, instructions, and modules stored in the memory, so as to implement the control method of the single-phase inverter in the above-described method embodiments.

The memory may include a storage program area and a storage data area, wherein the storage program area may store an operating system, an application program required for at least one function; the storage data area may store data created according to the use of the program distribution apparatus, and the like. Further, the memory may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some embodiments, the memory optionally includes memory remotely located from the processor, and these remote memories may be connected to the program distribution apparatus via a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

The one or more modules are stored in the memory and when executed by the one or more processors, perform the control method of the single-phase inverter in any of the method embodiments described above, e.g., perform the method steps in fig. 1 described above, implementing the functions of the modules and units in fig. 11.

In summary, the invention constructs a single-phase inverter voltage and current virtual axis based on a vector control idea of coordinate transformation in combination with a generalized second-order integral algorithm, decouples feedback alternating current signals by utilizing the coordinate transformation through a control strategy of combining voltage and current double-closed-loop PI control with a repetitive control principle, separates the phase amplitude of the alternating current signals, and can also realize the frequency modulation and amplitude modulation functions, and the amplitude can be used as a constant reference signal which is fixed and unchangeable, thereby realizing the non-static tracking of a PI control mode. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.