A control method for harmonic compensation circuit

Abstract

The present invention discloses a control method for a harmonic compensation circuit, which is divided into a power circuit part and a control method part. The power circuit part is a Boost type power factor correction circuit, which is composed of a rectifier bridge, a Π type filter circuit, a Boost circuit, and an output filter link; the control method part is composed of a voltage and current double closed-loop control loop and a reference current generation module containing a harmonic compensation signal, wherein the current controller is designed to be a combination of an embedded repetitive controller and a single zero-point single-pole compensator, and the reference current generation module includes a bandpass filter with a center frequency of 50Hz and a repetitive controller. Under the premise of not adding an additional sampling circuit, the present invention samples the input voltage, and while the converter realizes the power factor correction function, it compensates for the harmonic current flowing into the power grid from the common coupling point, and in the face of different power grid impedances, it can adaptively generate a reference current signal to reduce the harmonic current flowing into the power grid.

Description

Technical Field

[0001] The invention belongs to the technical field of power converters, and in particular relates to a control method for a harmonic compensation circuit. Background Art

[0002] With the extensive application of power electronic devices, harmonic pollution caused by nonlinear loads in commercial or residential distribution networks is characterized by wide-area and decentralized nature. Harmonics with complex and variable components threaten the safe and stable operation of the power grid, causing heating of power transformers and cables, increased power grid line losses, unstable operation of sensitive loads, and a series of other hazards.

[0003] In order to achieve harmonic control in local distribution networks, various harmonic control methods have been proposed. As the main harmonic control method, the parallel active power filter has been extensively studied in terms of control strategy and topology. Figure 1 As shown, S 1~ S 6 is the switch tube of each bridge arm. C o is the DC side stabilizing capacitor, L a , L b , L c is the input inductance. The active power filter collects the input current of the nonlinear load. i na , i nb , i nc The harmonic information in the output is collected, and the corresponding harmonic compensation current is output through the collected harmonic information i ca , i cb , i cc , reduce the grid current i ga , i gb , i gc total harmonic distortion to achieve the purpose of harmonic compensation.

[0004] However, the addition of parallel active power filters to the distribution network requires additional equipment costs, and parallel active power filters mostly use a centralized harmonic control method, which has limited control effects on the dispersed harmonic sources in the power grid. Now, in order to reduce the cost of equipment access, people try to give the existing equipment in the distribution network the function of harmonic compensation. With the development of new energy technologies, the number of distributed power generation systems such as photovoltaics and wind power in the distribution network has increased year by year. Many scholars at home and abroad have proposed using distributed power generation systems to control dispersed harmonic sources. However, in actual applications, the compensation capacity and installation location of these applications are greatly affected by natural factors such as light, wind speed, and geographical location.

[0005] Nowadays, PFC converters are widely used in variable frequency air conditioners, car charging piles, LED lighting and other fields. In recent years, my country has advocated the development strategy of safe, high-quality and sustainable electricity, and the proportion of PFC loads in the power grid has also increased year by year. At present, the research on PFC converters only considers that the converter itself is a resistive load for the power grid, and cannot reduce the harmonic current flowing into the power grid from the common coupling point. Because PFC converters are widely distributed in the power grid, the output power changes relatively stably over time, and the input current of the PFC converter is controllable, and the harmonic compensation current can be added to the input current to compensate for the harmonic current flowing into the power grid at the common coupling point. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a control method for a harmonic compensation circuit.

[0007] A control method for a harmonic compensation circuit of the present invention consists of a power circuit part and a control method part.

[0008] The power circuit is a Boost type power factor correction circuit, which consists of a rectifier bridge, a π type filter circuit, a Boost circuit, and an output filter. D 1~ D 4 is composed of a rectifier bridge to convert the input AC voltage into DC voltage. The filter network adopts a Π-type filter network, which consists of a filter inductor L f , filter capacitor C f1 , C f2 Composition, can significantly reduce the input current i in ripple in the input voltage and reduce v in The boost circuit consists of a boost inductor L m , MOS tube Q 1. Freewheeling diode D5, to achieve the boost function. The output filter consists of 2 electrolytic capacitors C o1 , C o2 structure to ensure the output voltage v o stability and reduce the output voltage v o of ripple.

[0009] The power circuit is specifically: diode D 1 positive electrode and D 3's negative pole is connected, D 2 positive electrode and D 4 is connected to the negative pole, D 1 negative electrode and D 2's negative pole is connected, D 3 positive electrode and D The positive poles of 4 are connected to form a rectifier bridge; the filter capacitor C f1 One end and the filter inductor L f Connected, L f The other end of the filter capacitor C f2 One end of the MOSFET is connected to form a Π-type filter circuit, which is connected to the output end of the rectifier bridge; the Π-type filter circuit is connected to the MOSFET Q 1. Excitation inductance L m , freewheeling diode D 5 is connected to the Boost circuit; the capacitors of the two output filter links C o1 , C o2 connected in parallel with the Boost circuit; output load and output capacitor C o1 , C o2 Phase parallel.

[0010] The control method consists of two parts: a voltage-current dual closed-loop control loop and a reference current generation module containing a harmonic compensation signal.

[0011] The voltage and current dual closed-loop control loop controls the converter to work in average current mode, specifically: the reference voltage v ref With output voltage v o After comparison, the voltage error signal is obtained v err As a voltage controller G v( s ) input, the output voltage is controlled by the voltage controller v o When the converter realizes the harmonic compensation function, the voltage after the sampling bridge | v in |, remove the absolute value through zero-crossing detection and restore the input voltage v in , and then extracted by the harmonic detection unit v in The harmonic components in v in-h , generating a harmonic compensation signal v z The command voltage signal v c . Voltage Controller G v ( s ) V e With voltage v c Multiply, the result is the reference current i ref , and the inductor current i Lm Compared with the current error signal i err As a current controller G c ( s ) input, the inductor current is controlled by the current controller i Lm Under average current mode control, due to the filter capacitor C f and filter inductor L f The presence of input current i in is the inductor current i Lm The average value during the switching cycle, so the current controller G c ( s ) can indirectly control the input current i in ,make i in Including harmonic compensation current i in-h , thereby realizing the harmonic compensation function.

[0012] The reference current generation module includes a bandpass filter with a center frequency of 50Hz and a repetitive controller. Under different grid impedance conditions, the reference current is adaptively generated. Specifically:G a ( s ) as a controller, which only contains the internal model link and gain link of the repetitive controller K h , G b ( s ) is a bandpass filter with a center frequency of 50Hz; the input voltage v in By sampling the voltage after the bridge | v in |The absolute value is removed by the program; input voltage v in After passing through the bandpass filter G b ( s ), the input voltage is obtained v in The harmonic components in v in-h , the harmonic components v in_h As the input of the repetitive controller, its output v RC and v in_h Add and multiply by the gain K h , and obtain the harmonic compensation signal v z , v z Then with the fundamental component v in_f After adding, take the absolute value and compare it with the voltage loop output v e Multiply to get the reference current i ref The purpose of this design is to reduce the harmonic components v in_h As the error signal, the input voltage v in and its fundamental component v in_f As the controlled object and reference signal respectively, and combined with the controller G a ( s ) to realize the controlled object v in Follow the upper reference signal v in_f Without knowing the grid impedance and phase, the controller G a ( s ) to reduce v in_h For the purpose, according to vin_h The harmonic compensation signal is adaptively generated according to the changes in v z .

[0013] To ensure the output voltage v o The stability of the voltage controller G v ( s ) is designed as a traditional proportional-integral controller. To ensure that the control object of the current loop i Lm Can quickly and accurately track the upper reference current i ref , current controller G c ( s ) structure requires special design. Current controller G c ( s ) is composed of an embedded repetitive controller and a single-zero-single-pole compensator, specifically:

[0014] Through the inductor current i Lm Sampling and comparing the current reference signal i ref Compare and get the current error signal i err , and as an embedded repetitive controller G RC ( s ) input; the embedded repetitive controller consists of an internal model link and a compensation link, where Q ( s ) is a low-pass filter, G f ( s ) is the leading link, N= f s / f n , f s is the sampling frequency, f n is the grid frequency, T s is the sampling period, k f is a constant; the output and error signal of the repeating controller i err After adding, it acts as a single zero-single pole compensator G i ( s ) input, and finally the duty cycle signal is output by the single zero-single pole compensator d; This ensures that the inductor current i Lm Able to quickly and accurately track the reference current containing fundamental wave and harmonics i ref , so that the current loop of the converter has good dynamic characteristics and sufficiently small steady-state error.

[0015] The beneficial technical effects of the present invention are:

[0016] 1. The present invention designs a new harmonic compensation circuit. Without adding an additional sampling circuit, the common coupling point voltage, i.e., the input voltage, is sampled, and a corresponding reference signal containing a harmonic compensation signal is generated according to the harmonic component information therein, so that the input current contains a harmonic compensation current to compensate for the harmonic current flowing into the power grid from the common coupling point.

[0017] 2. The present invention improves the voltage and current dual closed-loop control based on the Boost power factor correction converter topology, and designs the current controller therein as a combination of an embedded repetitive controller and a single zero-single pole compensator, which can ensure that the inductor current can quickly and accurately track the reference current containing the fundamental wave and each harmonic, so that the current loop of the converter has good dynamic characteristics and a sufficiently small steady-state error.

[0018] 3. The present invention designs a reference current generating module, adds a repetitive controller and a bandpass filter to the module, and uses the input voltage harmonic component as the error signal, and uses the input voltage and its fundamental component as the controlled object and the reference signal respectively. Without knowing the size and phase of the grid impedance, the reference current generating module can adaptively generate a harmonic compensation signal according to the change of the harmonic component with the purpose of reducing the harmonic component. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the topology of three-phase active power filter.

[0020] Figure 2 It is a Boost type power factor correction circuit.

[0021] Figure 3 It is a voltage and current dual closed-loop control loop.

[0022] Figure 4 It is a reference current generation module containing harmonic compensation signals.

[0023] Figure 5 This is the control block diagram of the current controller.

[0024] Figure 6 Control block diagram generated for the reference current.

[0025] Figure 7 It is a flow chart of the control program.

[0026] Figure 8 Schematic diagram of the principle of harmonic compensation implementation.

[0027] Fig. 9 This is the main current and voltage waveform diagram of the present invention.

[0028] Fig.10 It is an uncontrolled rectifier circuit.

[0029] Fig.11 This is the experimental waveform diagram under the traditional power factor correction mode.

[0030] Fig.12 This is the experimental waveform diagram under harmonic compensation mode.

[0031] Fig.13 It is the key waveform diagram of the power factor correction converter.

[0032] Fig.14 It is a histogram of each harmonic of the grid current.

[0033] Fig.15 This is the experimental waveform diagram when the grid impedance is composed of a 3.3Ω resistor and a 1mH inductor in series.

[0034] Fig.16 This is the experimental waveform diagram when the grid impedance is composed of a 5Ω resistor.

[0035] Fig.17 This is the experimental waveform diagram when the grid impedance is a 5Ω resistor and a 2mH inductor in series. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0037] A control method for a harmonic compensation circuit of the present invention consists of a power circuit part and a control method part.

[0038] The power circuit is a Boost type power factor correction circuit, which consists of a rectifier bridge, a π type filter circuit, a Boost circuit, and an output filter. D 1~ D 4 is composed of a rectifier bridge to convert the input AC voltage into DC voltage. The filter network adopts a Π-type filter network, which consists of a filter inductor L f , filter capacitor C f1 , C f2 Composition, can significantly reduce the input current iin ripple in the input voltage and reduce v in The boost circuit consists of a boost inductor L m , MOS tube Q 1. Freewheeling diode D 5, to achieve the boost function. The output filter consists of 2 electrolytic capacitors C o1 , C o2 To ensure the output voltage v o stability and reduce the output voltage v o of ripple.

[0039] The power circuit part is as follows Figure 2 As shown, specifically: diode D 1 positive electrode and D 3's negative pole is connected, D 2 positive electrode and D 4 is connected to the negative pole, D 1 negative electrode and D 2's negative pole is connected, D 3 positive electrode and D The positive poles of 4 are connected to form a rectifier bridge; the filter capacitor C f1 One end and the filter inductor L f Connected, L f The other end of the filter capacitor C f2 One end of the MOSFET is connected to form a Π-type filter circuit, which is connected to the output end of the rectifier bridge; the Π-type filter circuit is connected to the MOSFET Q 1. Excitation inductance L m , freewheeling diode D 5 is connected to the Boost circuit; the capacitors of the two output filter links C o1 , C o2 connected in parallel with the Boost circuit; output load and output capacitor C o1 , C o2 Phase parallel.

[0040] The control method consists of two parts: voltage and current double closed-loop control loop and reference current generation module containing harmonic compensation signal, as shown in Figure 3 , Figure 4As shown. The voltage and current double closed-loop control loop is controlled by a voltage controller G v ( s ), current controller G c ( s ), adder and multiplier. The reference current generation module containing the harmonic compensation signal consists of a zero-crossing detection module, a harmonic detection module, a repetitive controller G a ( s ), adder and absolute value operation.

[0041] The control method is as follows:

[0042] according to Figure 7 As shown in the control program flow chart, when the control program starts to execute, it needs to be initialized first. After initialization, the voltage after the bridge will be sampled once in each sampling cycle. v in | until | v in | is not equal to 0, the harmonic compensation control program starts to be executed. Each sampling cycle will be used to calculate the voltage after the bridge| v in |、Inductor current i Lm and output voltage v o The protection program will trigger the protection program when the sampling value is not within the normal operating range. The protection program will force the duty cycle signal to be set to 0, making the MOS tube Q 1 Normally closed, manual reset and re-initialization are required to exit the protection program. When the sampling value is within the normal operating range, the preset reference voltage v ref Subtract the sampled output voltage v o , and get the error voltage v err , through the voltage controller G v ( s ), that is, after the proportional integral link, the output value of the voltage loop can be obtained V e ,like Figure 3 shown.

[0043] Then execute the program of the reference current generation module containing the harmonic compensation signal, and its control block diagram is as follows Figure 6 As shown. First, the voltage after removing the bridge | v in |The absolute value of | is detected by using the zero-crossing detection procedure. vin |'s zero point can be removed by flipping the waveform within half the power frequency cycle every half the power frequency cycle. v in The absolute value of | is used to obtain the input voltage v in .Will v in As the input of the second-order bandpass filter, the bandpass filter output v in The fundamental component in v in-f ,use v in Subtract the fundamental component v in-f Get the harmonic components v in-h The bandpass filter has the following form:

[0044] (1)

[0045] In the formula, Q b is the quality factor, ω o is the center frequency angular frequency, take 2π×50Hz. v in-h As input to the repetitive controller, the repetitive controller outputs a signal v RC , v RC and harmonic components v in-h After adding, multiply by the gain factor K h , and obtain the harmonic compensation signal v z , and then v z With fundamental component v in-f After adding, multiply by the voltage loop output V e Then get the current reference signal i ref From the above, we can know G a ( s ) is as follows:

[0046] (2)

[0047] In the formula, Q (s) is a second-order low-pass filter. To ensure the effect of harmonic compensation, the cut-off frequency is set to 4kHz. Kh is the gain coefficient, which is a constant with the dimension of admittance.

[0048] When the input voltage v in When there are harmonics in the input voltage, it is assumed that the input voltage can be accurately obtained after filtering by a bandpass filter. v in fundamental component of v in_f and harmonic components v in_h , the harmonic components can be v in_h As the error signal, v in and v in_f As the controlled object and reference signal respectively, and combined with the controller G a ( s ) to realize the controlled object v in Follow the upper reference signal v in_f Without knowing the grid impedance and phase, the controller G a ( s ) to reduce harmonic components v in_h For the purpose, according to v in_h The harmonic compensation signal is adaptively generated according to the changes in v z . And because the controller G a ( s ) contains a repeating controller, when v in_h When it finally decreases to close to 0, the output of the controller is repeated v RC It will be a periodic signal and will no longer change. At the same time, the repetitive controller can achieve a good tracking effect on the periodic signal.

[0049] according to Figure 7 As shown, the current reference signal is obtained i ref After that, the current loop operation program will be executed, and the control block diagram of the current loop is as follows: Figure 5 shown. i ref Subtract the inductor current i Lm , and get the error current i err , i errAs a repeating controller G RC ( s ) input, after the internal model link and advance compensation link of the repeated controller, the output of the repeated controller is i err Added together, as a single zero-single pole compensator G i ( s ) input, and finally by G i ( s ) Output duty cycle signal d . The repeating controller G RC ( s ) is as follows:

[0050] (3)

[0051] In the formula, Q ( s ) is a low-pass filter, k r is the repetitive controller gain, G f ( s ) = is the advance compensation link, m is the number of beats ahead, T s is the sampling period, N= f s / f n , f s is the sampling frequency, f n is the grid frequency.

[0052] Combination Figure 8 The principle of harmonic compensation achieved by the present invention is described. Figure 8 As shown, the converter input voltage v in This is the voltage at the common coupling point. Z g The existence of grid current i g Flow through Z g There will be a pressure drop, which can be calculated as v in for:

[0053] (4)

[0054] in vg is the grid voltage, which is assumed to be a sinusoidal voltage containing only the fundamental wave. The harmonics generated by all nonlinear loads in the distribution network are equivalent to a harmonic current. i h , then the grid current i g Include i h and PFC converter input current i in , i in Can be decomposed into fundamental components i in-f and harmonic components i in-h . v in The harmonic components in v in-h Mainly by i h and i in-h Flow through the grid impedance Z g The voltage drop generated is the harmonic voltage. i in-f A certain voltage drop will also be generated on the fundamental wave component. v in The fundamental component in v in-f and harmonic components v in-h They are as follows:

[0055] (5)

[0056] (6)

[0057] From formula (6), we can see that when i in-h right i h When there is a compensatory effect, v in-h will decrease, and v in-h and i h The phases of are opposite. Therefore, we can extract v in The harmonic components in v in-h , through the controller G a ( s ) amplifies it in a certain proportion to generate a harmonic compensation signal vz To ensure that the PFC converter still has a high power factor, v z and v in-f Add and take the absolute value to get the command voltage signal v c . v c and V e After multiplication, we get i ref , so the input current of the converter is i in Contains i h Harmonic compensation current i in-h , to compensate for the harmonics flowing into the distribution network. The main current and voltage waveforms are as follows Fig. 9 As shown, i in Contains i h Harmonic compensation current with opposite phase, i in for i Lm The average value during the switching cycle.

[0058] The power circuit parameters of the embodiment of the present invention are shown in Table 1.

[0059] Table 1 Power circuit parameters

[0060]

[0061] Fig.10 This is the uncontrolled rectifier circuit used in the experiment, in which the capacitor C r =220μF and resistor R r =1200Ω, and contains a rectifier bridge D b .according to Figure 3 The connection mode shown in the figure is used for the experiment, in which the grid impedance is composed of a 5Ω resistor and a 1mH inductor in series. Fig.11 This is the experimental waveform of the converter working in the traditional power factor correction mode. Due to the access of nonlinear load, the grid current i g There is a large distortion, at this time its THD=12.453%, when i g Flow through the grid impedance Z g Whenv in Distortion also occurs. v in THD = 1.104%. Fig.12 This is the experimental waveform diagram of the converter working in the harmonic compensation mode. As the PFC converter starts to perform the harmonic compensation function, i in The harmonic compensation current is included in i g The distortion has been significantly reduced, and its THD has been reduced to 1.886%. v in The THD is also reduced to 0.147%. At this time, the PF of the converter is 0.976, and the converter still has a relatively high PF value. Fig.13 is the key waveform diagram of the power factor correction converter, where i ref The DA chip is scaled down and then output. i Lm Better tracking of the reference current i ref , and when operating in harmonic compensation mode, the output voltage of the PFC v o The average value is 402V, with no obvious distortion. After measurement, the ripple size is 20V and the output voltage ripple rate is 4.975%. Therefore, when the converter works in harmonic compensation mode, the energy supply to the load is not affected. Fig.14 is the grid current i g It can be seen that the reference current generation method based on repeated control proposed in the present invention can reduce i g The harmonic content of .

[0062] Fig.15 , Fig.16 , Fig.17 The experimental waveforms under different grid impedances are shown in Figure 2. A 3.3Ω resistor and a 1mH inductor are connected in series as Fig.15 The grid impedance is Fig.16 , 17) are composed of a 5Ω resistor, a 5Ω resistor and a 2mH inductor in series. The grid currents under these three grid impedance conditions are measured. i g The THD of the PFC converters are 1.987%, 1.913%, and 2.075%, respectively, and the PF of the PFC converters are 0.976, 0.976, and 0.977, respectively. Fig.12Compared with the experimental results shown in FIG. 1 , it can be shown that the control method proposed by the present invention can adapt to the change of the grid impedance and improve the THD value of the current flowing into the grid from the common coupling point.

[0063] The present invention proposes a control method for a harmonic compensation circuit, which utilizes the controllable input current of a power factor correction converter to enable the power factor correction converter to generate a harmonic compensation current to compensate for the harmonic current flowing into the power grid from the common coupling point. In order to realize the compensation of the harmonic current by the Boost type power factor correction converter, the present invention designs an input current controller containing an embedded repetitive control link and a single zero-single pole compensation to ensure that the input current of the converter accurately tracks the reference current, and adds a repetitive controller to the reference current signal generation link to reduce the input impedance of the converter at each harmonic frequency, thereby ensuring that it has a good compensation effect on the harmonic current.

Claims

1. A control method for a harmonic compensation circuit, characterized in that: It consists of a power circuit part and a control method part; The power circuit is a Boost type power factor correction circuit, which consists of a rectifier bridge, a Π type filter circuit, a Boost circuit, and an output filter link, specifically: diode D 1 positive electrode and D 3's negative pole is connected, D 2 positive electrode and D 4 is connected to the negative pole, D 1 negative electrode and D 2's negative pole is connected, D 3 positive electrode and D The positive poles of 4 are connected to form a rectifier bridge; the filter capacitor C f1 One end and the filter inductor L f Connected, L f The other end of the filter capacitor C f2 One end of the MOSFET is connected to form a Π-type filter circuit, which is connected to the output end of the rectifier bridge; the Π-type filter circuit is connected to the MOSFET Q 1. Excitation inductance L m , freewheeling diode D 5 is connected to the Boost circuit; the capacitors of the two output filter links C o1 , C o2 connected in parallel with the Boost circuit; output load and output capacitor C o1 , C o2 Phase parallel connection; The control method part consists of two parts: voltage and current double closed-loop control loop and reference current generation module containing harmonic compensation signal; The voltage and current dual closed-loop control loop controls the converter to work in average current mode, specifically: the reference voltage v ref With output voltage v o After comparison, the voltage error signal is obtained v err As a voltage controller G v ( s ) input; When the converter realizes the harmonic compensation function, the voltage after sampling bridge | v in |, remove the absolute value through zero-crossing detection and restore the input voltage v in , and then extracted by the harmonic detection unit v in The harmonic components in v in-h , generating a harmonic compensation signal v z The command voltage signal v c ; Voltage controller G v ( s ) V e With voltage v c Multiply, the result is the reference current i ref , and the inductor current i Lm Compared with the current error signal i err As a current controller G c ( s ) input, the inductor current is controlled by the current controller i Lm Waveform; Under average current mode control, due to the filter capacitor C f and filter inductor L f The presence of input current i in is the inductor current i Lm The average value during the switching cycle, so the current controller G c ( s ) can indirectly control the input current i in ,make i in Including harmonic compensation current i in-h , thereby realizing the harmonic compensation function; The reference current generation module includes a bandpass filter with a center frequency of 50Hz and a repetitive controller. Under different grid impedance conditions, the reference current is adaptively generated. Specifically: G a ( s ) as a controller, which only contains the internal model link and gain link of the repetitive controller K h , G b ( s ) is a bandpass filter with a center frequency of 50Hz; the input voltage v in By sampling the voltage after the bridge | v in |The absolute value is removed by the program; input voltage v in After passing through the bandpass filter G b ( s ), the input voltage is obtained v in The harmonic components in v in-h , the harmonic components v in_h As the input of the repetitive controller, its output v RC and v in_h Add and multiply by the gain K h , and obtain the harmonic compensation signal v z , v z Then with the fundamental component v in_f After adding, take the absolute value and compare it with the voltage loop output v e Multiply to get the reference current i ref .

2. The control method of a harmonic compensation circuit according to claim 1, characterized in that: The inductor current of the converter i Lm It is controlled by a current controller, which is a combination of an embedded repetitive controller and a single zero-single pole compensator, specifically: Through the inductor current i Lm Sampling and comparing the current reference signal i ref Compare and get the current error signal i err , and as an embedded repetitive controller G RC ( s ) input; Embedded The repetitive controller consists of an internal model link and a compensation link. Q ( s ) is a low-pass filter, G f ( s ) is the leading link, N= f s / f n , f s is the sampling frequency, f n is the grid frequency, T s is the sampling period, k f is a constant; the output and error signal of the repeating controller i err After adding, it acts as a single zero-single pole compensator G i ( s ) input, and finally the duty cycle signal is output by the single zero-single pole compensator d ; This ensures that the inductor current i Lm Able to quickly and accurately track the reference current containing the fundamental wave and each harmonic i ref .

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