Voltage feed-forward control method and device for improving PFC weak power grid adaptability

Abstract

The invention discloses a voltage feed-forward control method and device for improving PFC weak power grid adaptability. The method comprises the steps that power grid sampling voltage of a power grid connected to a PFC control circuit and output voltage of the PFC control circuit are acquired; performing harmonic decomposition on the power grid sampling voltage to obtain fundamental waves and low-order harmonics; performing voltage reconstruction on the fundamental wave and the low-order harmonic wave based on a preset voltage reconstruction strategy to obtain a reconstructed power grid voltage; and determining a current voltage feed-forward control coefficient based on a difference value between the power grid sampling voltage and the reconstructed power grid voltage, and taking the current voltage feed-forward control coefficient as a feed-forward quantity of a duty ratio output by a target control loop. According to the embodiment of the invention, feedforward control is carried out on the power grid voltage in a mode of reconstructing the input voltage accessed to the power grid, so that the adaptability of PFC to a weak power grid is improved, and the background harmonic suppression effect is maintained.

Description

Technical Field

[0001] The present invention relates to the field of PFC control technology, and in particular to a voltage feedforward control method and device for improving the adaptability of PFC to weak power grids. Background Art

[0002] In order to improve the dynamic performance of PFC (i.e. power factor correction) and reduce the impact of grid fluctuations and background harmonics, grid voltage feedforward control is often added to PFC control. The addition of grid voltage feedforward reduces the system stability margin, and positive feedback oscillation problems may occur in weak grid environments, reducing the system's ability to adapt to weak grids. Conventional solutions generally use grid voltage filtering or loop bandwidth optimization, but measures such as adding filtering and reducing loop bandwidth also reduce the system's dynamic performance and the effect of suppressing background harmonics. Summary of the invention

[0003] The embodiments of the present invention provide a voltage feedforward control method and device for improving the adaptability of PFC weak power grid, aiming to solve the problem that in the prior art, in order to reduce the influence of power grid fluctuations and background harmonics, power grid voltage feedforward control is added, and the power grid voltage is filtered or the loop bandwidth is reduced for optimization, but this also leads to reduced system dynamic performance and background harmonic suppression effect.

[0004] In a first aspect, an embodiment of the present invention provides a voltage feedforward control method for improving the adaptability of a PFC weak grid, which includes: Obtaining a grid sampling voltage of a grid to which the PFC control circuit is connected, and an output voltage of the PFC control circuit; Performing harmonic decomposition on the grid sampling voltage to obtain a fundamental wave and low-order harmonics; Reconstructing the voltage of the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage; Based on the difference between the output voltage and the reconstructed grid voltage, a current voltage feedforward control coefficient is determined, and the current voltage feedforward control coefficient is used as a feedforward amount of a duty cycle output by a target control loop.

[0005] In a second aspect, an embodiment of the present invention further provides a voltage feedforward control device for improving the adaptability of a PFC weak power grid, which includes: A grid voltage sampling unit, used to obtain a grid sampling voltage of the grid to which the PFC control circuit is connected, and an output voltage of the PFC control circuit; A harmonic decomposition unit, used for performing harmonic decomposition on the grid sampling voltage to obtain a fundamental wave and low-order harmonics; A voltage reconstruction unit, configured to perform voltage reconstruction on the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage; A feedforward control coefficient acquisition unit is used to determine a current voltage feedforward control coefficient based on a difference between the output voltage and the reconstructed grid voltage, and use the current voltage feedforward control coefficient as a feedforward amount of a duty cycle output by a target control loop.

[0006] In a third aspect, an embodiment of the present invention further provides a computer device, which includes a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the method described in the first aspect is implemented.

[0007] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, wherein the computer storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the method described in the first aspect above can be implemented.

[0008] The embodiment of the present invention provides a voltage feedforward control method and device for improving the adaptability of PFC to weak power grids. The method includes: obtaining the grid sampling voltage of the power grid to which the PFC control circuit is connected, and the output voltage of the PFC control circuit; performing harmonic decomposition on the grid sampling voltage to obtain the fundamental wave and low-order harmonics; performing voltage reconstruction on the fundamental wave and low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage; determining the current voltage feedforward control coefficient based on the difference between the grid sampling voltage and the reconstructed grid voltage, and using the current voltage feedforward control coefficient as the feedforward amount of the duty cycle output by the target control loop. The embodiment of the present invention controls the grid voltage feedforward by reconstructing the input voltage of the connected grid, which not only improves the adaptability of PFC to weak power grids, but also maintains the background harmonic suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative work.

[0010] Figure 1 A flow chart of a voltage feedforward control method for improving the adaptability of a PFC weak power grid provided by an embodiment of the present invention; Figure 2 A circuit diagram of a PFC control circuit applied to a voltage feedforward control method for improving the adaptability of a PFC weak power grid provided in an embodiment of the present invention; Figure 3 A schematic diagram of a sub-process of a voltage feedforward control method for improving the adaptability of a PFC weak power grid provided by an embodiment of the present invention; Figure 4A schematic diagram of a sub-process of a voltage feedforward control method for improving the adaptability of a PFC weak power grid provided by an embodiment of the present invention; Figure 5 A schematic block diagram of a voltage feedforward control device for improving the adaptability of a PFC weak power grid provided by an embodiment of the present invention; Figure 6 A schematic block diagram of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0011] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0012] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0013] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0014] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0015] See also Figure 1 , which is a flow chart of a voltage feedforward control method for improving the adaptability of PFC weak grid provided by an embodiment of the present invention. Figure 1 As shown, the voltage feedforward control method for improving the adaptability of PFC weak power grid includes steps S110 to S140.

[0016] S110 , obtaining a grid sampling voltage of a grid to which the PFC control circuit is connected, and an output voltage of the PFC control circuit.

[0017] In this embodiment, the voltage feedforward control method for improving the adaptability of PFC to weak power grid is applied to the PFC control circuit, and the specific circuit of the PFC control circuit is as follows: Figure 2As shown. The PFC control circuit specifically includes an inductor L1, a switch tube Q1, a diode (specifically including 5 diodes, and respectively recorded as a first diode D1, a second diode D2, a third diode D3, a fourth diode D4 and a fifth diode D5) arranged in a preset connection mode, a capacitor C1 and a load resistor RL. More specifically, the cathode of the second diode D2 is connected to the anode of the first diode D1, and is also connected to a power source (for example, the power source is a power grid, and its input voltage is u g ) is connected to the positive electrode of the first diode D1; the negative electrode of the first diode D1 is connected to the first end of the inductor L1; the negative electrode of the fourth diode D4 is connected to the positive electrode of the third diode D3, and is also connected to the negative electrode of the power supply; the negative electrode of the third diode D3 is connected to the first end of the inductor L1; the second end of the inductor L1 is connected to the drain of the switch tube Q1 (specifically a metal-oxide-semiconductor field effect transistor or an insulated gate bipolar transistor), and is also connected to the positive electrode of the fifth diode D5; the source of the switch tube Q1 is connected to the positive electrode of the second diode D2 and the positive electrode of the fourth diode D4; the negative electrode of the fifth diode D5 is connected to the first end of the capacitor C1, and is also connected to the first end of the load resistor RL; the second end of the capacitor C1 is connected to the source of the switch tube Q1; the second end of the load resistor RL is connected to the source of the switch tube Q1.

[0018] The grid sampling voltage of the grid to which the PFC control circuit is connected is the input voltage u in the above example. g , and the output voltage of the PFC control circuit is the output voltage u across the load resistor RL o The input voltage u obtained g And the output voltage u o , which can be used for subsequent voltage feedforward control.

[0019] Of course, in specific implementation, a preset sampling period for obtaining the grid sampling voltage of the grid to which the PFC control circuit is connected can be set, and step S110 is restarted after each interval corresponding to the length of the sampling period, and voltage feedforward control within this sampling period is performed.

[0020] S120: performing harmonic decomposition on the grid sampling voltage to obtain a fundamental wave and low-order harmonics.

[0021] In this embodiment, the grid sampling voltage is subjected to harmonic decomposition to understand the power quality of the grid and possible problems. Among them, the fundamental wave refers to the sinusoidal wave component equal to the longest period of the oscillation in a complex periodic oscillation, and the frequency corresponding to this period is called the fundamental frequency, and the fundamental frequency represents the standard frequency of the grid, such as 50Hz. Harmonics refer to the components greater than the integer multiples of the fundamental frequency obtained by Fourier series decomposition of the periodic non-sinusoidal alternating current corresponding to the grid sampling voltage, that is, harmonics are formed by increasing the frequency of the fundamental wave on the basis of the fundamental wave. For example, if the fundamental frequency of the fundamental wave is 50Hz, the second harmonic is 100Hz (i.e., twice the fundamental frequency), the third harmonic is 150Hz (i.e., three times the fundamental frequency), and so on. It can be seen that by performing harmonic decomposition on the grid sampling voltage, the fundamental wave and low-order harmonics can be accurately obtained.

[0022] In one embodiment, if Figure 3 As shown, step S120 includes: S121, inputting the grid sampling voltage into a phase-locked loop to obtain a phase-locked loop output signal; S122, performing Fourier transform on the phase-locked loop output signal to obtain a fundamental wave and each harmonic; S123. Based on preset low-order harmonic frequency data, obtain the low-order harmonic from each harmonic.

[0023] In this embodiment, when obtaining the grid sampling voltage, fundamental wave and each harmonic, it is necessary to process it through a phase-locked loop and perform Fourier transform in sequence to obtain the fundamental wave and each harmonic. Among them, the phase-locked loop (PLL, full name is PhaseLocked Loop) is a negative feedback control system that uses the voltage generated by phase synchronization to tune the voltage-controlled oscillator to generate the target frequency. g After processing, a phase-locked loop output signal that can be easily extracted can be obtained.

[0024] When Fourier transform is performed on the phase-locked loop output signal, the phase-locked loop output signal of the time domain signal type can be converted to the frequency domain signal type, and the fundamental wave and each harmonic can be accurately obtained in the frequency domain. Since not too many harmonics are needed for subsequent voltage reconstruction, it is also necessary to obtain the low-order harmonics from each harmonic based on the low-order harmonic frequency data, so as to retain the required low-order harmonics.

[0025] In one embodiment, step S121 includes: The grid sampling voltage is input into a phase-locked loop for phase detection, low-pass filtering and voltage-controlled oscillator control processing in sequence to obtain the phase-locked loop output signal whose output signal frequency is an integer multiple of the frequency of the grid sampling voltage.

[0026] In this embodiment, when the grid sampling voltage is processed by the phase-locked loop, the following process is mainly performed: 1) Phase detection, that is, the grid voltage is compared with the standard reference signal generated by the voltage-controlled oscillator inside the phase-locked loop through the phase detector to obtain the phase difference comparison result; the phase difference comparison result is a positive error voltage or a negative error voltage; 2) Low-pass filtering, that is, filtering out the high-frequency noise and clutter in the phase difference comparison result (which can also be understood as the error voltage) output after phase detection through a low-pass filter, so that the low-frequency or DC component in the phase difference comparison result passes through, and the phase-locked loop improves the stability and anti-interference ability of the system and reduces signal distortion; 3) Voltage-controlled oscillator control processing, that is, the low-frequency component and DC component output by the low-pass filter are input to the voltage-controlled oscillator for processing. For example, taking the processing of the DC component as an example, when the DC component is output to the voltage-controlled oscillator, the output frequency of the voltage-controlled oscillator will change with the change of the DC component. Specifically, the larger the DC component, the higher the output frequency of the voltage-controlled oscillator, and vice versa, the smaller the DC component, the lower the output frequency of the voltage-controlled oscillator. Through this adjustment, the output frequency of the voltage-controlled oscillator is related to the phase difference of the output signal of the low-pass filter; moreover, part of the output signal of the voltage-controlled oscillator will be fed back to the phase detector, and continuously compared and adjusted with the grid sampling voltage input to the phase detector until the phase difference reaches a stable value (such as zero or a minimum value infinitely close to zero).

[0027] Through the above processing method, the phase-locked loop realizes locking of the input signal, that is, the grid sampling voltage, and when the output reaches a stable state, the output signal has a fixed phase relationship with the input signal.

[0028] In one embodiment, step S123 includes: Obtaining the frequency multiple included in the low-order harmonic frequency data; wherein the frequency multiple is an odd number, and 1≤frequency multiple≤13; The low-order harmonics are obtained from the respective harmonics based on the frequency multiples included in the low-order harmonic frequency data.

[0029] In this embodiment, when obtaining low-order harmonics in each harmonic, the low-order harmonic frequency data can be pre-specified, and a number of odd frequency multiples (this frequency multiple represents the frequency of the harmonic / multiple of the fundamental frequency) can be included therein, and its value range can also be specifically limited. After the frequency multiples included in the low-order harmonic frequency data are known, the harmonics of the corresponding frequency multiples can be extracted from the various harmonics based on the frequency multiples included in the low-order harmonic frequency data, so as to quickly obtain the low-order harmonics.

[0030] In one embodiment, the frequency multiples included in the low-order harmonic frequency data include 3, 5, 7, 9, 11 and 13.

[0031] In this embodiment, if the low-order harmonics include more harmonics with higher frequency multiples, the impact on the subsequent voltage reconstruction will be greater. At this time, the frequency multiples included in the low-order harmonic frequency data can be set to include 3, 5, 7, 9, 11 and 13. The low-order harmonics are composed of the above 6 harmonics and participate in the subsequent signal synthesis.

[0032] Specifically, if the fundamental frequency of the fundamental wave is 50Hz, the low-order harmonics include the third harmonic of 150Hz (i.e. three times the fundamental frequency), the fifth harmonic of 250Hz (i.e. five times the fundamental frequency), the seventh harmonic of 450Hz (i.e. seven times the fundamental frequency), the ninth harmonic of 450Hz (i.e. nine times the fundamental frequency), the eleventh harmonic of 550Hz (i.e. eleven times the fundamental frequency), and the thirteenth harmonic of 650Hz (i.e. thirteen times the fundamental frequency).

[0033] S130. Reconstruct the voltage of the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage.

[0034] In this embodiment, after determining the fundamental wave and low-order harmonics corresponding to the grid sampling voltage, the fundamental wave and low-order harmonics can be voltage reconstructed to obtain the reconstructed grid voltage. For example, the preset voltage reconstruction strategy is to superimpose and sum the fundamental wave and low-order harmonics, so that the reconstructed grid voltage can be quickly obtained for subsequent voltage feedforward control, and because the high-order harmonics are filtered out, the adaptability of PFC to weak grids is improved, and the background harmonic suppression effect is maintained.

[0035] In one embodiment, step S130 includes: A signal synthesis model corresponding to the voltage reconstruction strategy is obtained, and the fundamental wave and the low-order harmonics are subjected to signal synthesis based on the signal synthesis model to obtain the reconstructed grid voltage.

[0036] In this embodiment, the signal synthesis model corresponding to the voltage reconstruction strategy can be obtained first. The fundamental wave and the low-order harmonics can be superimposed and summed through the signal synthesis model. For example, the voltage of the fundamental wave is recorded as u1, the voltage of the third harmonic is recorded as u3, the voltage of the fifth harmonic is recorded as u5, the voltage of the seventh harmonic is recorded as u7, the voltage of the ninth harmonic is recorded as u9, and the voltage of the eleventh harmonic is recorded as u1. 11 And the voltage of the thirteenth harmonic is recorded as u 13 , then the fundamental wave and low-order harmonics are superimposed and summed up to be expressed as u g ’ =u1+ u3+ u5+ u7+ u9+ u 11 + u 13 , and the corresponding result is the reconstructed grid voltage, which is expressed as u g ’ .

[0037] S140. Determine a current voltage feedforward control coefficient based on a difference between the output voltage and the reconstructed grid voltage, and use the current voltage feedforward control coefficient as a feedforward amount of a duty cycle output by a target control loop.

[0038] In this embodiment, after determining the reconstructed grid voltage, the current voltage feedforward control coefficient can be further determined by the difference between the output voltage and the reconstructed grid voltage, and the obtained voltage feedforward control coefficient is used as the feedforward amount of the duty cycle output by the target control loop corresponding to the PFC control circuit. Moreover, the voltage feedforward control method for improving the adaptability of PFC weak grid in this application can be specifically used in circuits such as Boost circuits, single-phase PFC, three-phase PFC, Vienna topology PFC, and can also be specifically applied to charging pile modules, on-board chargers and other devices.

[0039] In one embodiment, if Figure 4 As shown, step S140 includes: S141, obtaining a difference between the output voltage and the absolute value of the reconstructed grid voltage to obtain a voltage difference; S142. Obtain a ratio of the voltage difference to the grid sampling voltage, and use the ratio as the current voltage feedforward control coefficient.

[0040] In this embodiment, when the reconstructed grid voltage u is obtained g ’ And the output voltage u o Then, the difference between the output voltage and the absolute value of the reconstructed grid voltage is calculated to obtain the voltage difference, that is, , and then calculate the ratio of the voltage difference to the grid sampling voltage, that is, , and finally d feed As the current voltage feedforward control coefficient, and as the feedforward amount of the duty cycle output by the target control loop corresponding to the PFC control circuit.

[0041] It can be seen that the embodiment of the method performs feed-forward control on the grid voltage by reconstructing the input voltage of the connected grid, which not only improves the adaptability of PFC to weak grids, but also maintains the effect of suppressing background harmonics.

[0042] Figure 5Schematic block diagram of a voltage feedforward control device for improving the adaptability of PFC weak grid provided by an embodiment of the present invention. Figure 5 As shown, corresponding to the above voltage feedforward control method for improving the adaptability of PFC weak power grid, the present invention also provides a voltage feedforward control device 100 for improving the adaptability of PFC weak power grid. The voltage feedforward control device 100 for improving the adaptability of PFC weak power grid includes: a power grid voltage sampling unit 110, a harmonic decomposition unit 120, a voltage reconstruction unit 130 and a feedforward control coefficient acquisition unit 140.

[0043] The grid voltage sampling unit 110 is used to obtain a grid sampling voltage of the grid to which the PFC control circuit is connected, and an output voltage of the PFC control circuit.

[0044] In this embodiment, the voltage feedforward control method for improving the adaptability of PFC to weak power grid is applied to the PFC control circuit, and the specific circuit of the PFC control circuit is as follows: Figure 2 As shown. The PFC control circuit specifically includes an inductor L1, a switch tube Q1, a diode (specifically including 5 diodes, and respectively recorded as a first diode D1, a second diode D2, a third diode D3, a fourth diode D4 and a fifth diode D5) arranged in a preset connection mode, a capacitor C1 and a load resistor RL. More specifically, the cathode of the second diode D2 is connected to the anode of the first diode D1, and is also connected to a power source (for example, the power source is a power grid, and its input voltage is u g ) is connected to the positive electrode of the first diode D1; the negative electrode of the first diode D1 is connected to the first end of the inductor L1; the negative electrode of the fourth diode D4 is connected to the positive electrode of the third diode D3, and is also connected to the negative electrode of the power supply; the negative electrode of the third diode D3 is connected to the first end of the inductor L1; the second end of the inductor L1 is connected to the drain of the switch tube Q1 (specifically a metal-oxide-semiconductor field effect transistor or an insulated gate bipolar transistor), and is also connected to the positive electrode of the fifth diode D5; the source of the switch tube Q1 is connected to the positive electrode of the second diode D2 and the positive electrode of the fourth diode D4; the negative electrode of the fifth diode D5 is connected to the first end of the capacitor C1, and is also connected to the first end of the load resistor RL; the second end of the capacitor C1 is connected to the source of the switch tube Q1; the second end of the load resistor RL is connected to the source of the switch tube Q1.

[0045] The grid sampling voltage of the grid to which the PFC control circuit is connected is the input voltage u in the above example. g , and the output voltage of the PFC control circuit is the output voltage u across the load resistor RL o The input voltage u obtained g And the output voltage u o , which can be used for subsequent voltage feedforward control.

[0046] Of course, in specific implementation, a preset sampling period for obtaining the grid sampling voltage of the grid to which the PFC control circuit is connected can be set, and the grid voltage sampling unit 110 is restarted after each interval of the sampling period, and voltage feedforward control is performed within this sampling period.

[0047] The harmonic decomposition unit 120 is used to perform harmonic decomposition on the grid sampling voltage to obtain a fundamental wave and low-order harmonics.

[0048] In this embodiment, the grid sampling voltage is subjected to harmonic decomposition to understand the power quality of the grid and possible problems. Among them, the fundamental wave refers to the sinusoidal wave component equal to the longest period of the oscillation in a complex periodic oscillation, and the frequency corresponding to this period is called the fundamental frequency, and the fundamental frequency represents the standard frequency of the grid, such as 50Hz. Harmonics refer to the components greater than the integer multiples of the fundamental frequency obtained by Fourier series decomposition of the periodic non-sinusoidal alternating current corresponding to the grid sampling voltage, that is, harmonics are formed by increasing the frequency of the fundamental wave on the basis of the fundamental wave. For example, if the fundamental frequency of the fundamental wave is 50Hz, the second harmonic is 100Hz (i.e., twice the fundamental frequency), the third harmonic is 150Hz (i.e., three times the fundamental frequency), and so on. It can be seen that by performing harmonic decomposition on the grid sampling voltage, the fundamental wave and low-order harmonics can be accurately obtained.

[0049] In one embodiment, the harmonic decomposition unit 120 is specifically used for: Inputting the grid sampling voltage into a phase-locked loop to obtain a phase-locked loop output signal; Performing Fourier transform on the phase-locked loop output signal to obtain a fundamental wave and each harmonic; Based on preset low-order harmonic frequency data, the low-order harmonics are obtained from each harmonic.

[0050] In this embodiment, when obtaining the grid sampling voltage, fundamental wave and each harmonic, it is necessary to process it through a phase-locked loop and perform Fourier transform in sequence to obtain the fundamental wave and each harmonic. Among them, the phase-locked loop (PLL, full name is PhaseLocked Loop) is a negative feedback control system that uses the voltage generated by phase synchronization to tune the voltage-controlled oscillator to generate the target frequency. g After processing, a phase-locked loop output signal that can be easily extracted can be obtained.

[0051] When Fourier transform is performed on the phase-locked loop output signal, the phase-locked loop output signal of the time domain signal type can be converted to the frequency domain signal type, and the fundamental wave and each harmonic can be accurately obtained in the frequency domain. Since not too many harmonics are needed for subsequent voltage reconstruction, it is also necessary to obtain the low-order harmonics from each harmonic based on the low-order harmonic frequency data, so as to retain the required low-order harmonics.

[0052] In one embodiment, the harmonic decomposition unit 120 is further specifically configured to: The grid sampling voltage is input into a phase-locked loop for phase detection, low-pass filtering and voltage-controlled oscillator control processing in sequence to obtain the phase-locked loop output signal whose output signal frequency is an integer multiple of the frequency of the grid sampling voltage.

[0053] In this embodiment, when the grid sampling voltage is processed by the phase-locked loop, the following process is mainly performed: 1) Phase detection, that is, the grid voltage is compared with the standard reference signal generated by the voltage-controlled oscillator inside the phase-locked loop through the phase detector to obtain the phase difference comparison result; the phase difference comparison result is a positive error voltage or a negative error voltage; 2) Low-pass filtering, that is, filtering out the high-frequency noise and clutter in the phase difference comparison result (which can also be understood as the error voltage) output after phase detection through a low-pass filter, so that the low-frequency or DC component in the phase difference comparison result passes through, and the phase-locked loop improves the stability and anti-interference ability of the system and reduces signal distortion; 3) Voltage-controlled oscillator control processing, that is, the low-frequency component and DC component output by the low-pass filter are input to the voltage-controlled oscillator for processing. For example, taking the processing of the DC component as an example, when the DC component is output to the voltage-controlled oscillator, the output frequency of the voltage-controlled oscillator will change with the change of the DC component. Specifically, the larger the DC component, the higher the output frequency of the voltage-controlled oscillator, and vice versa, the smaller the DC component, the lower the output frequency of the voltage-controlled oscillator. Through this adjustment, the output frequency of the voltage-controlled oscillator is related to the phase difference of the output signal of the low-pass filter; moreover, part of the output signal of the voltage-controlled oscillator will be fed back to the phase detector, and continuously compared and adjusted with the grid sampling voltage input to the phase detector until the phase difference reaches a stable value (such as zero or a minimum value infinitely close to zero).

[0054] Through the above processing method, the phase-locked loop realizes locking of the input signal, that is, the grid sampling voltage, and when the output reaches a stable state, the output signal has a fixed phase relationship with the input signal.

[0055] In one embodiment, the harmonic decomposition unit 120 is further specifically configured to: Obtaining the frequency multiple included in the low-order harmonic frequency data; wherein the frequency multiple is an odd number, and 1≤frequency multiple≤13; The low-order harmonics are obtained from the respective harmonics based on the frequency multiples included in the low-order harmonic frequency data.

[0056] In this embodiment, when obtaining low-order harmonics in each harmonic, the low-order harmonic frequency data can be pre-specified, and a number of odd frequency multiples (this frequency multiple represents the frequency of the harmonic / multiple of the fundamental frequency) can be included therein, and its value range can also be specifically limited. After the frequency multiples included in the low-order harmonic frequency data are known, the harmonics of the corresponding frequency multiples can be extracted from the various harmonics based on the frequency multiples included in the low-order harmonic frequency data, so as to quickly obtain the low-order harmonics.

[0057] In one embodiment, the frequency multiples included in the low-order harmonic frequency data include 3, 5, 7, 9, 11 and 13.

[0058] In this embodiment, if the low-order harmonics include more harmonics with higher frequency multiples, the impact on the subsequent voltage reconstruction will be greater. At this time, the frequency multiples included in the low-order harmonic frequency data can be set to include 3, 5, 7, 9, 11 and 13. The low-order harmonics are composed of the above 6 harmonics and participate in the subsequent signal synthesis.

[0059] Specifically, if the fundamental frequency of the fundamental wave is 50Hz, the low-order harmonics include the third harmonic of 150Hz (i.e. three times the fundamental frequency), the fifth harmonic of 250Hz (i.e. five times the fundamental frequency), the seventh harmonic of 450Hz (i.e. seven times the fundamental frequency), the ninth harmonic of 450Hz (i.e. nine times the fundamental frequency), the eleventh harmonic of 550Hz (i.e. eleven times the fundamental frequency), and the thirteenth harmonic of 650Hz (i.e. thirteen times the fundamental frequency).

[0060] The voltage reconstruction unit 130 is used to perform voltage reconstruction on the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage.

[0061] In this embodiment, after determining the fundamental wave and low-order harmonics corresponding to the grid sampling voltage, the fundamental wave and low-order harmonics can be voltage reconstructed to obtain the reconstructed grid voltage. For example, the preset voltage reconstruction strategy is to superimpose and sum the fundamental wave and low-order harmonics, so that the reconstructed grid voltage can be quickly obtained for subsequent voltage feedforward control, and because the high-order harmonics are filtered out, the adaptability of PFC to weak grids is improved, and the background harmonic suppression effect is maintained.

[0062] In one embodiment, the voltage reconstruction unit 130 is specifically used for: A signal synthesis model corresponding to the voltage reconstruction strategy is obtained, and the fundamental wave and the low-order harmonics are subjected to signal synthesis based on the signal synthesis model to obtain the reconstructed grid voltage.

[0063] In this embodiment, the signal synthesis model corresponding to the voltage reconstruction strategy can be obtained first. The fundamental wave and the low-order harmonics can be superimposed and summed through the signal synthesis model. For example, the voltage of the fundamental wave is recorded as u1, the voltage of the third harmonic is recorded as u3, the voltage of the fifth harmonic is recorded as u5, the voltage of the seventh harmonic is recorded as u7, the voltage of the ninth harmonic is recorded as u9, and the voltage of the eleventh harmonic is recorded as u1. 11 And the voltage of the thirteenth harmonic is recorded as u 13 , then the fundamental wave and low-order harmonics are superimposed and summed up to be expressed as u g ’ = u1+ u3+ u5+ u7+ u9+ u 11 + u 13 , and the corresponding result is the reconstructed grid voltage, which is expressed as u g ’ .

[0064] The feedforward control coefficient acquisition unit 140 is used to determine the current voltage feedforward control coefficient based on the difference between the output voltage and the reconstructed grid voltage, and use the current voltage feedforward control coefficient as the feedforward amount of the duty cycle output by the target control loop.

[0065] In this embodiment, after determining the reconstructed grid voltage, the current voltage feedforward control coefficient can be further determined by the difference between the output voltage and the reconstructed grid voltage, and the obtained voltage feedforward control coefficient is used as the feedforward amount of the duty cycle output by the target control loop corresponding to the PFC control circuit. Moreover, the voltage feedforward control method for improving the adaptability of PFC weak grid in this application can be specifically used in circuits such as Boost circuits, single-phase PFC, three-phase PFC, Vienna topology PFC, and can also be specifically applied to charging pile modules, on-board chargers and other devices.

[0066] In one embodiment, the feedforward control coefficient acquisition unit 140 is specifically used for: Obtaining a difference between the output voltage and the absolute value of the reconstructed grid voltage to obtain a voltage difference; The ratio of the voltage difference to the grid sampling voltage is obtained and used as the current voltage feedforward control coefficient.

[0067] In this embodiment, when the grid voltage u is obtained g ’ And the output voltage u oThen, the difference between the output voltage and the absolute value of the reconstructed grid voltage is calculated to obtain the voltage difference, that is, , and then calculate the ratio of the voltage difference to the grid sampling voltage, that is, , and finally d feed As the current voltage feedforward control coefficient, and as the feedforward amount of the duty cycle output by the target control loop corresponding to the PFC control circuit.

[0068] It can be seen that the embodiment of the device implements feed-forward control of the grid voltage by reconstructing the input voltage of the connected grid, which not only improves the adaptability of PFC to weak grids, but also maintains the effect of suppressing background harmonics.

[0069] An embodiment of the present invention further provides a control circuit, which includes an inductor, a switch tube, a diode, a capacitor and a load resistor arranged in a preset connection manner; the control circuit is used to execute the aforementioned voltage feedforward control method for improving the adaptability of PFC weak power grid.

[0070] Among them, the control circuit can be specifically applied to Boost circuits, single-phase PFC, three-phase PFC, Vienna topology PFC and other circuits, and the control circuit can be specifically applied to charging pile modules, vehicle-mounted chargers and other devices.

[0071] The voltage feedforward control device for improving the adaptability of PFC weak grid can be implemented in the form of a computer program. The computer program can be used in Figure 6 Runs on the computer device shown.

[0072] See also Figure 6 , Figure 6 The schematic block diagram of a computer device provided by an embodiment of the present invention is shown in FIG. The computer device integrates any voltage feedforward control device for improving the adaptability of a PFC weak power grid provided by an embodiment of the present invention.

[0073] See also Figure 6 The computer device 400 includes a processor 402 , a memory and a network interface 405 connected via a system bus 401 , wherein the memory may include a storage medium 403 and an internal memory 404 .

[0074] The storage medium 403 can store an operating system 4031 and a computer program 4032. The computer program 4032 includes program instructions, and when the program instructions are executed, the processor 402 can execute the voltage feedforward control method for improving the adaptability of the PFC weak grid.

[0075] The processor 402 is used to provide computing and control capabilities to support the operation of the entire computer device.

[0076] The internal memory 404 provides an environment for the operation of the computer program 4032 in the storage medium 403. When the computer program 4032 is executed by the processor 402, the processor 402 can execute the above-mentioned voltage feedforward control method for improving the adaptability of the PFC weak grid.

[0077] The network interface 405 is used to communicate with other devices over the network. Figure 6 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present invention, and does not constitute a limitation on the computer device to which the solution of the present invention is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0078] The processor 402 is used to run a computer program 4032 stored in the memory to implement the voltage feedforward control method for improving the weak grid adaptability of PFC as described above.

[0079] It should be understood that in the embodiment of the present invention, the processor 402 may be a central processing unit (CPU), and the processor 402 may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Among them, the general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0080] It can be understood by those skilled in the art that all or part of the processes in the method for implementing the above embodiment can be completed by instructing the relevant hardware through a computer program. The computer program includes program instructions, and the computer program can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in the computer system to implement the process steps of the embodiment of the above method.

[0081] Therefore, the present invention also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program, wherein the computer program includes program instructions. When the program instructions are executed by a processor, the processor executes the voltage feedforward control method for improving the adaptability of PFC weak power grid as described above.

[0082] The computer-readable storage medium may be a USB flash drive, a mobile hard disk, a read-only memory (ROM), a magnetic disk, or an optical disk, etc., which are computer-readable storage media that can store program codes.

[0083] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0084] In the several embodiments provided by the present invention, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of each unit is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed.

[0085] The steps in the method of the embodiment of the present invention can be adjusted in order, combined and deleted according to actual needs. The units in the device of the embodiment of the present invention can be combined, divided and deleted according to actual needs. In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0086] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a storage medium. Based on this understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, terminal, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention.

[0087] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A voltage feedforward control method for improving the adaptability of PFC weak power grid, characterized in that: include: Obtaining a grid sampling voltage of a grid to which the PFC control circuit is connected, and an output voltage of the PFC control circuit; Performing harmonic decomposition on the grid sampling voltage to obtain a fundamental wave and low-order harmonics; Reconstructing the voltage of the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage; Based on the difference between the output voltage and the reconstructed grid voltage, a current voltage feedforward control coefficient is determined, and the current voltage feedforward control coefficient is used as a feedforward amount of a duty cycle output by a target control loop.

2. The method according to claim 1, characterized in that The harmonic decomposition of the grid sampling voltage to obtain a fundamental wave and low-order harmonics includes: Inputting the grid sampling voltage into a phase-locked loop to obtain a phase-locked loop output signal; Performing Fourier transform on the phase-locked loop output signal to obtain a fundamental wave and each harmonic; Based on preset low-order harmonic frequency data, the low-order harmonics are obtained from each harmonic.

3. The method according to claim 2, characterized in that The step of inputting the grid sampling voltage into a phase-locked loop to obtain a phase-locked loop output signal comprises: The grid sampling voltage is input into a phase-locked loop for phase detection, low-pass filtering and voltage-controlled oscillator control processing in sequence to obtain the phase-locked loop output signal whose output signal frequency is an integer multiple of the frequency of the grid sampling voltage.

4. The method according to claim 2, characterized in that: The step of obtaining the low-order harmonics from each harmonic based on preset low-order harmonic frequency data includes: Obtaining the frequency multiple included in the low-order harmonic frequency data; wherein the frequency multiple is an odd number, and 1≤frequency multiple≤13; The low-order harmonics are obtained from the respective harmonics based on the frequency multiples included in the low-order harmonic frequency data.

5. The method according to claim 4, characterized in that The frequency multiples included in the low-order harmonic frequency data include 3, 5, 7, 9, 11 and 13.

6. The method according to claim 1, characterized in that The voltage reconstruction of the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage includes: A signal synthesis model corresponding to the voltage reconstruction strategy is obtained, and the fundamental wave and the low-order harmonics are subjected to signal synthesis based on the signal synthesis model to obtain the reconstructed grid voltage.

7. The method according to claim 1, characterized in that The step of determining a current voltage feedforward control coefficient based on a difference between the output voltage and the reconstructed grid voltage comprises: Obtaining a difference between the output voltage and the absolute value of the reconstructed grid voltage to obtain a voltage difference; The ratio of the voltage difference to the grid sampling voltage is obtained and used as the current voltage feedforward control coefficient.

8. A voltage feedforward control device for improving the adaptability of PFC weak power grid, characterized in that: include: A grid voltage sampling unit, used to obtain a grid sampling voltage of the grid to which the PFC control circuit is connected, and an output voltage of the PFC control circuit; A harmonic decomposition unit, used for performing harmonic decomposition on the grid sampling voltage to obtain a fundamental wave and low-order harmonics; A voltage reconstruction unit, configured to perform voltage reconstruction on the fundamental wave and the low-order harmonics based on a preset voltage reconstruction strategy to obtain a reconstructed grid voltage; A feedforward control coefficient acquisition unit is used to determine a current voltage feedforward control coefficient based on a difference between the output voltage and the reconstructed grid voltage, and use the current voltage feedforward control coefficient as a feedforward amount of a duty cycle output by a target control loop.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the voltage feedforward control method for improving the adaptability of PFC to weak power grids according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by a processor, the voltage feedforward control method for improving the adaptability of a PFC weak power grid as described in any one of claims 1 to 7 can be implemented.

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