Dual-frequency control method for power factor during grid connection of flyback inverter, and controller

Abstract

Disclosed in the present application are a dual-frequency control method for a power factor during grid connection of a flyback inverter, and a controller. The method comprises: acquiring an operating electrical signal of a power grid; obtaining a first sinusoidal modulation wave signal; obtaining a second sinusoidal modulation wave signal; on the basis of a power factor, determining a phase angle difference and a time difference corresponding to the phase angle difference; obtaining a sinusoidal correction modulation frequency; generating a sinusoidal correction modulation wave signal, the frequency of which is the sinusoidal correction modulation frequency; and by means of the sinusoidal correction modulation wave signal, controlling a flyback inverter to output an alternating current. The power factor is adjusted by means of adjusting the phase difference between a target power grid and a sinusoidal correction modulation wave; moreover, a first sinusoidal modulation wave can operate independently when a power source only has active power, and the sinusoidal correction modulation wave can operate independently when the power source requires reactive power adjustment. The flyback inverter is controlled by means of the sinusoidal correction modulation wave in the present application, such that the flyback inverter can accurately adjust the power factor during grid connection, and a harmonic distortion rate is reduced.

Description

Method and controller for double-frequency control of power factor of flyback inverter grid-connected TECHNICAL FIELD

[0001] The present application relates to the field of flyback inverter grid connection, and particularly relates to a method and controller for double-frequency control of power factor of flyback inverter grid-connected. BACKGROUND

[0002] An inverter is a device that converts direct current (DC) to alternating current (AC). A general inverter uses a technology called PWM (pulse width modulation) or SPWM (sine pulse width modulation) to generate alternating current. In the process of using SPWM technology, the inverter simulates a sine waveform by rapidly switching a switching device (such as an IGBT). Because the switching speed of the switching device is very fast, the inverter will generate high-frequency harmonics when switching the switching device to simulate the sine wave. And the photovoltaic power generation circuit generally has inductive load or capacitive load, thereby generating active power and reactive power, which are out of sync or have a phase angle, resulting in a change in power factor.

[0003] In related technologies, the output of the flyback circuit usually uses a diode. This circuit can achieve a grid-connected current with a power factor of 1, but due to the unidirectional conduction characteristic of the diode, energy cannot be transmitted from the grid to the photovoltaic side, and the power factor adjustment of the inverter grid-connected cannot be achieved. There is no detailed disclosure of a special method for controlling the power factor adjustment of the flyback micro inverter grid-connected in the related art.

[0004] SUMMARY

[0005] The main purpose of the present application is to provide a method and controller for double-frequency control of power factor of flyback inverter grid-connected, aiming to solve the problem of how to accurately adjust the power factor.

[0006] To achieve the above-mentioned purpose, the present application provides a method for double-frequency control of power factor of flyback inverter grid-connected, comprising the following steps:

[0007] Obtaining a working electrical signal of a target grid;

[0008] Phase-locked to the working electrical signal to obtain a first sinusoidal modulation wave signal consistent with the initial phase and frequency of the working electrical signal;

[0009] According to a preset power factor and the first sinusoidal modulation wave signal, a second sinusoidal modulation wave signal is obtained, which is consistent with the frequency of the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal;

[0010] According to the phase angle difference, a time difference corresponding to the phase angle difference is obtained;

[0011] obtaining a half cycle length of the first sinusoidal modulation wave signal, and obtaining a sinusoidal correction modulation frequency different from the working electrical signal frequency through a difference between the half cycle length of the first sinusoidal modulation wave signal and the time difference;

[0012] generating a sinusoidal correction modulation wave signal with a frequency of the sinusoidal correction modulation frequency;

[0013] controlling the flyback inverter to output target alternating current corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical equipment based on the sinusoidal correction modulation wave signal.

[0014] In some embodiments, the generating the sinusoidal correction modulation wave signal with the frequency of the sinusoidal correction modulation frequency comprises:

[0015] generating a third sinusoidal modulation wave signal with a frequency of the sinusoidal correction modulation frequency;

[0016] obtaining a carrier signal, the carrier signal being a triangular wave signal or a sawtooth wave signal;

[0017] superimposing the third sinusoidal modulation wave signal and the carrier signal to obtain the sinusoidal correction modulation wave signal.

[0018] In some embodiments, the generating the third sinusoidal modulation wave signal with the frequency of the sinusoidal correction modulation frequency comprises:

[0019] when the waveform of the second sinusoidal modulation wave signal leads the voltage waveform of the first sinusoidal modulation wave signal, the sinusoidal correction modulation wave signal is generated in a time period corresponding to a half cycle start point of the second sinusoidal modulation wave signal to a half cycle end point of the first sinusoidal modulation wave signal;

[0020] when the waveform of the second sinusoidal modulation wave signal lags the voltage waveform of the first sinusoidal modulation wave signal, the sinusoidal correction modulation wave signal is generated in a time period corresponding to a half cycle start point of the second sinusoidal modulation wave signal to a half cycle end point of the first sinusoidal modulation wave signal.

[0021] In some embodiments, the obtaining the second sinusoidal modulation wave signal with the frequency consistent with the frequency of the first sinusoidal modulation wave signal and the phase angle difference relative to the first sinusoidal modulation wave signal according to the preset power factor and the first sinusoidal modulation wave signal comprises:

[0022] phase-shifting the first sinusoidal modulation wave signal according to the phase angle corresponding to the preset power factor to obtain the second sinusoidal modulation wave signal with the frequency consistent with the frequency of the first sinusoidal modulation wave signal and the phase angle difference relative to the first sinusoidal modulation wave signal.

[0023] In some embodiments, the first sinusoidal modulation wave signal is phase-shifted according to a phase angle corresponding to a preset power factor to obtain a second sinusoidal modulation wave signal having a same frequency as the first sinusoidal modulation wave signal and a phase angle difference with respect to the first sinusoidal modulation wave signal.

[0024] When the load connected to the flyback inverter is an inductive load, the first sinusoidal modulation wave signal is phase-shifted in a lagging direction according to a phase angle corresponding to a preset power factor to obtain a second sinusoidal modulation wave signal having a same frequency as the first sinusoidal modulation wave signal and a phase angle difference with respect to the first sinusoidal modulation wave signal.

[0025] When the load connected to the flyback inverter is a capacitive load, the first sinusoidal modulation wave signal is phase-shifted in a leading direction according to a phase angle corresponding to a preset power factor to obtain a second sinusoidal modulation wave signal having a same frequency as the first sinusoidal modulation wave signal and a phase angle difference with respect to the first sinusoidal modulation wave signal.

[0026] In some embodiments, the frequency of the working electrical signal is 50 Hz or 60 Hz.

[0027] In some embodiments, the control of the flyback inverter to output target alternating current corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical device by the sinusoidal correction modulation wave signal comprises the following steps:

[0028] The switch tube in the flyback inverter is controlled by the sinusoidal correction modulation wave signal, so that the power supply outputs alternating current corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical device through the flyback inverter.

[0029] In some embodiments, the frequency of the carrier signal is greater than the frequency of the third sinusoidal modulation wave signal.

[0030] In some embodiments, the sinusoidal correction modulation wave signal is an SPWM wave signal.

[0031] The present application also provides an inverter controller, wherein the inverter controller stores a computer program, and the computer program is executed by a processor to implement the method for controlling the power factor of the flyback inverter connected to the target power grid.

[0032] The present application adjusts the phase difference between the target power grid and the sinusoidal correction modulation wave to adjust the power factor, and the first sinusoidal modulation wave can work independently when the power supply only has active power, and the sinusoidal correction modulation wave can work independently when the power supply needs to adjust the reactive power. The flyback inverter is controlled by the sinusoidal correction modulation wave in the present application, so that the flyback inverter can accurately adjust the power factor when connected to the grid, and the harmonic distortion rate is reduced. Attached Figure Description

[0033] Figure 1 is a schematic diagram of the steps of a method for improving the grid-connected power factor of a dual-frequency control flyback inverter according to an embodiment of this application.

[0034] Figure 2 is a schematic diagram of the waveforms of u1, i1, and i2 when i2 lags u1 according to an embodiment of this application;

[0035] Figure 3 is a timing diagram composed of the waveforms of u1 and i3 when i2 lags u1 and the SPWM waveform of i3 provided in the embodiment of this application;

[0036] Figure 4 is a schematic diagram of the waveforms of u1, i1, and i2 when i2 leads u1 according to an embodiment of this application;

[0037] Figure 5 is a timing diagram composed of the waveforms of u1 and i3 when i2 leads u1 and the SPWM waveform of i3 provided in the embodiment of this application.

[0038] Figure 6 is a flowchart provided in an embodiment of this application;

[0039] Figure 7 is a circuit diagram provided in an embodiment of this application.

[0040] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] The solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments in this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0042] The use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the steps described for that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0043] As shown in Figure 1, this application proposes a method for improving the grid-connected power factor of a dual-frequency controlled flyback inverter, comprising the following steps (S1, S2, S3, S4, S5, S6 and S7):

[0044] Step S1: obtaining the working electrical signal of the target power grid. Specifically, the power grid in the present application refers to a system composed of power plants, power transmission lines, substations and power distribution facilities and other power devices. In the power grid, AC mode is used for power transmission. The current and voltage in the power grid are sinusoidal AC, and the frequency is 50Hz or 60Hz. Therefore, the working electrical signal of the target power grid obtained in the present application is a sinusoidal AC signal with a frequency of 50Hz or 60Hz.

[0045] Step S2: phase locking the working electrical signal to obtain a first sinusoidal modulation wave signal consistent with the initial phase and frequency of the working electrical signal. Specifically, phase locking the working electrical signal refers to obtaining a first current modulation wave signal consistent with the phase and frequency of the working electrical signal through phase locking technology. It should be noted that the working electrical signal is a voltage signal. Phase locking technology is a technology that controls the phase of the controlled oscillator by a standard signal or an external signal, which is used to realize phase synchronization with the external signal or track the frequency or phase of the external signal.

[0046] Step S3: obtaining a second sinusoidal modulation wave signal according to the preset power factor and the first sinusoidal modulation wave signal, the second sinusoidal modulation wave signal having a same frequency as the first sinusoidal modulation wave signal and having a phase angle difference with respect to the first sinusoidal modulation wave signal. The frequency of the second sinusoidal modulation wave signal is the same as the frequency of the first current modulation wave signal, and the second sinusoidal modulation wave signal has a phase angle difference corresponding to the preset power factor with respect to the working electrical signal. It should be noted that the phase angle difference is the difference between the initial phase of the second sinusoidal modulation wave signal and the initial phase of the first sinusoidal modulation wave signal. Specifically, the working electrical signal is a voltage signal. As an implementation form, after obtaining the preset power factor, the power factor angle is obtained, and the power factor angle is the phase angle difference. The working electrical signal is a sinusoidal alternating voltage signal, the preset power factor angle is Ψ, and the power factor is cos Ψ. Further, the first sinusoidal modulation wave signal is a current signal. The working electrical signal is represented as u1=A0sin(ω0t), where A0 represents the voltage amplitude of the working electrical signal, ω0 represents the angular frequency of the working electrical signal, and t represents time. The first sinusoidal modulation wave signal is represented as i1=A1sin(ω1t), where A1 represents the current amplitude of the first sinusoidal modulation wave signal, ω1 represents the angular frequency of the first sinusoidal modulation wave signal, and t represents time. Since the frequency of the first sinusoidal modulation wave signal is the same as that of the working electrical signal, ω0=ω1. The second sinusoidal modulation wave signal is represented as i2=A2sin(ω2t-Ψ) or i2=A2sin(ω2t+Ψ), where A2 represents the current amplitude of the second sinusoidal modulation wave signal, ω2 represents the angular frequency of the second sinusoidal modulation wave signal, and t represents time. Since the frequency of the second sinusoidal modulation wave signal is the same as that of the first sinusoidal modulation wave signal, ω1=ω2. The sinusoidal correction modulation wave signal is represented as i3=A3sin(ω3t-Ψ) or i3=A3sin(ω3t+Ψ), where A3 represents the current amplitude of the sinusoidal correction modulation wave signal, ω3 represents the angular frequency of the sinusoidal correction modulation wave signal, and t represents time.

[0047] In some embodiments, the second sinusoidal modulation wave signal has a phase angle difference corresponding to the preset power factor with respect to the first sinusoidal modulation wave signal, that is, the second sinusoidal wave modulation wave signal leads or lags the first sinusoidal modulation wave signal by an angle of Ψ. Further, since the frequency and initial phase of the first sinusoidal modulation wave signal are the same as those of the working electrical signal, the second sinusoidal wave modulation wave signal leads or lags the first sinusoidal modulation wave signal by an angle of Ψ.

[0048] As an implementation form, as shown in FIG. 2, the second sinusoidal wave modulation wave signal lags the working electrical signal by an angle of Ψ, that is, represented as i2=A2sin(ω2t-Ψ), where Ψ represents the initial phase of the second sinusoidal wave modulation wave signal.

[0049] As an implementation, as shown in FIG. 4, the second sinusoidal modulation wave signal leads the working electrical signal by an angle of Ψ, that is, represented as i2=A2sin(ω2t+Ψ), where Ψ represents the initial phase of the second sinusoidal modulation wave signal.

[0050] Step S4: According to the phase angle difference, a time difference corresponding to the phase angle difference is obtained. Specifically, the time difference corresponding to the phase angle difference can be represented as

[0051] Step S5: The half cycle time length of the first sinusoidal modulation wave signal is obtained, and a sinusoidal correction modulation frequency different from the working electrical signal frequency is obtained by the difference between the half cycle time length of the first sinusoidal modulation wave signal and the time difference.

[0052] Step S6: A sinusoidal correction modulation wave signal with a frequency of the sinusoidal correction modulation frequency is generated. The half cycle time length of the sinusoidal correction modulation wave signal is equal to the difference between the half cycle time length of the first sinusoidal modulation wave signal and the time difference. As shown in FIG. 2 and FIG. 4, the period of the first sinusoidal modulation wave signal is T1, the half cycle of the first sinusoidal modulation wave signal is The period of the sinusoidal correction modulation wave signal is T3, and Since Therefore After T3 is obtained, the sinusoidal correction modulation frequency can be obtained, and thus the sinusoidal correction modulation wave signal with the frequency of the sinusoidal correction modulation frequency is generated.

[0053] As an implementation, as shown in FIG. 2 and FIG. 3, when the second sinusoidal modulation wave signal lags behind the first sinusoidal modulation wave signal, the sinusoidal correction modulation wave signal is only generated in the time period corresponding to the starting point of the half cycle of the second sinusoidal modulation wave signal to the ending point of the half cycle of the first sinusoidal modulation wave signal. Specifically, the sinusoidal correction modulation wave signal can be generated in the time period corresponding to the starting point of the half cycle of the second sinusoidal modulation wave signal (for example, the Ψ point in FIG. 2 and FIG. 3) to the ending point of the half cycle of the first sinusoidal modulation wave signal (for example, the π point in FIG. 2 and FIG. 3), and the sinusoidal correction modulation wave signal can also be generated in the time period corresponding to the starting point of the half cycle of the second sinusoidal modulation wave signal (for example, the π+Ψ point in FIG. 2 and FIG. 3) to the ending point of the half cycle of the first sinusoidal modulation wave signal (for example, the 2π point in FIG. 2 and FIG. 3). As shown in FIG. 3, the sinusoidal correction modulation wave signal generated in the time period corresponding to the Ψ point to the π point in FIG. 3 is a positive half cycle sinusoidal wave of the positive half cycle wave in the lagging working electrical signal, and the sinusoidal correction modulation wave signal i2 generated in the time period corresponding to the π+Ψ point to the 2π point in FIG. 3 is a negative half cycle sinusoidal wave of the negative half cycle wave in the lagging working electrical signal.

[0054] ​As an implementation, as shown in FIG. 4 and FIG. 5, the sinusoidal correction modulation wave signal is generated only in the time period corresponding to the half cycle starting point of the working electrical signal to the half cycle ending point of the first sinusoidal modulation wave signal when the first sinusoidal modulation wave signal leads the working electrical signal. Specifically, the sinusoidal correction modulation wave signal can be generated in the time period corresponding to the half cycle starting point of the working electrical signal (for example, 0 point in FIG. 4 and FIG. 5) to the half cycle ending point of the first sinusoidal modulation wave signal (for example, π-Ψ point in FIG. 4 and FIG. 5), and the sinusoidal correction modulation wave signal can also be generated in the time period corresponding to the half cycle starting point of the working electrical signal (for example, π point in FIG. 4 and FIG. 5) to the half cycle ending point of the first sinusoidal modulation wave signal (for example, 2π-Ψ point in FIG. 4 and FIG. 5). As shown in FIG. 5, the sinusoidal correction modulation wave signal i2 generated in the time period corresponding to 0 point to π-Ψ point in FIG. 5 is a positive half cycle sinusoidal wave synchronized with the positive half cycle wave in the working electrical signal, and the sinusoidal correction modulation wave signal i2 generated in the time period corresponding to π point to 2π-Ψ point in FIG. 5 is a negative half cycle sinusoidal wave synchronized with the negative half cycle wave in the working electrical signal.

[0055] Specifically, since the sinusoidal correction modulation wave signal is generated according to the working electrical signal and the first sinusoidal modulation wave signal, and the frequency of the sinusoidal correction modulation wave signal is different from the frequency of the working electrical signal, the control of the flyback inverter by the sinusoidal correction modulation wave signal is called double frequency control.

[0056] As an implementation, the second sinusoidal modulation wave signal which is consistent with the frequency of the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal is obtained according to the preset power factor and the first sinusoidal modulation wave signal, including:

[0057] The first sinusoidal modulation wave signal is phase-shifted according to the phase angle corresponding to the preset power factor, to obtain the second sinusoidal modulation wave signal which is consistent with the frequency of the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal.

[0058] In some embodiments, the first sinusoidal modulation wave signal is phase-shifted according to the phase angle corresponding to the preset power factor, to obtain the second sinusoidal modulation wave signal which is consistent with the frequency of the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal, including:

[0059] When the load connected to the flyback inverter is an inductive load, the first sinusoidal modulation wave signal is phase-shifted in a lagging direction according to the phase angle corresponding to the preset power factor, to obtain the second sinusoidal modulation wave signal which is consistent with the frequency of the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal;

[0060] When the load connected to the flyback inverter is a capacitive load, the first sinusoidal modulation wave signal is phase-shifted in a leading direction according to a phase angle corresponding to a preset power factor, to obtain a second sinusoidal modulation wave signal having a same frequency as the first sinusoidal modulation wave signal and a phase angle difference with respect to the first sinusoidal modulation wave signal.

[0061] Step S7: controlling the power supply to output a target electric signal corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical equipment by sinusoidal correction modulation wave signal.

[0062] As an implementation form, step S5: controlling the power supply to output a target electric signal corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical equipment by sinusoidal correction modulation wave signal, includes the following steps:

[0063] The switch tube in the flyback inverter is controlled by the sinusoidal correction modulation wave signal, so that the power supply outputs a target alternating current corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical equipment through the micro inverter.

[0064] In some embodiments, step S6: generating a third sinusoidal modulation wave signal having a frequency of the sinusoidal correction modulation frequency includes:

[0065] The third sinusoidal modulation wave signal having a frequency of the sinusoidal correction modulation frequency is generated, a half cycle time length of the third sinusoidal modulation wave signal is equal to a difference between a half cycle time length of the first sinusoidal modulation wave signal and the time difference, and the third sinusoidal modulation wave signal has a phase angle difference with respect to the first sinusoidal modulation wave signal.

[0066] The carrier signal is obtained, and the carrier signal is a triangular wave signal or a sawtooth wave signal.

[0067] The third sinusoidal modulation wave signal and the carrier signal are superimposed to obtain the sinusoidal correction modulation wave signal.

[0068] In some embodiments, the frequency of the carrier signal is greater than the frequency of the third sinusoidal modulation wave signal.

[0069] In some embodiments, the sinusoidal modified modulation wave signal is a sinusoidal pulse width modulation (SPWM) wave signal, which is an output signal approximating a sinusoidal wave. SPWM controls alternating voltage and current by adjusting the width of square wave pulses so that their average value varies as a sinusoidal waveform over a period, thereby achieving control. SPWM wave signals have the characteristics of low harmonic content, flexible control and high efficiency. Specifically, as shown in FIG. 3 and FIG. 5, FIG. 3 has a SPWM waveform diagram of the sinusoidal modified modulation wave when the second sinusoidal modulation wave signal lags the operating electrical signal, and FIG. 5 has a SPWM waveform diagram of the sinusoidal modified modulation wave when the second sinusoidal modulation wave signal leads the operating electrical signal.

[0070] As an implementation, as shown in FIG. 6, the operating electrical signal of the target power grid is obtained by the controller. Specifically, the controller is an inverter controller for controlling the flyback inverter, and the controller includes a microprocessor, which is one of the core components of the controller and is responsible for overall control and coordination functions. The microprocessor can implement the control algorithm and logic of the flyback inverter, including power regulation, frequency control, voltage adjustment, etc., to ensure that the output power of the flyback inverter meets the requirements of the power grid. The microprocessor also provides a communication interface with external systems, such as a monitoring system, and a power grid interface. Through the communication interface, the microprocessor can exchange data with external devices, receive instructions, and report the operating status of the flyback inverter through the monitoring system. In addition, the microprocessor can process data from various sensors (such as current sensors, voltage sensors) and input devices (such as buttons, switches), and make appropriate decisions based on the monitored conditions, such as switching operating modes or adjusting output parameters. For example, the controller can control the first sinusoidal modulation wave to work independently when the power supply only has active power, and can control the sinusoidal modified modulation wave signal to work independently when the power supply needs to adjust reactive power.

[0071] Further, after the controller obtains the working signal of the target power grid, the working signal is phase-locked to obtain a first sinusoidal modulation wave signal with the same initial phase and frequency as the working signal. Meanwhile, the controller can obtain a preset power factor of the power source to be connected to the grid. It should be noted that, assuming that the power factor of the power grid is 1, the preset power factor can be set to 0.8 or 0.9 according to the nature of the load in the power source to be connected to the grid (for example, an inductive load or a capacitive load). After obtaining the preset power factor, the controller obtains a second sinusoidal modulation wave signal with the same frequency as the first sinusoidal modulation wave signal and a phase angle difference with respect to the first sinusoidal modulation wave signal according to the preset power factor and the first sinusoidal modulation wave signal. Specifically, the second sinusoidal modulation wave signal is obtained by phase-shifting the first sinusoidal modulation wave signal, and the phase-shifting angle is the angle corresponding to the preset power factor, i.e., the phase angle difference. When the load is an inductive load, the second sinusoidal modulation wave signal is obtained by phase-shifting the first sinusoidal modulation wave signal in the lag direction; when the load is a capacitive load, the second sinusoidal modulation wave signal is obtained by phase-shifting the first sinusoidal modulation wave signal in the lag direction.

[0072] Further, the controller obtains a time difference corresponding to the phase angle difference according to the phase angle difference. Then the controller generates a sinusoidal correction modulation wave signal according to the time difference and the first sinusoidal modulation wave signal, wherein the half-cycle time length of the sinusoidal correction modulation wave signal is equal to the difference between the half-cycle time length of the first sinusoidal modulation wave signal and the time difference. It can be known that the period and frequency of the sinusoidal correction modulation wave signal, so as to generate the sinusoidal correction modulation wave signal. Finally, the controller controls the flyback inverter to output the target alternating current corresponding to the sinusoidal correction modulation wave signal to the target power grid or the electrical equipment based on the sinusoidal correction modulation wave signal.

[0073] It should be noted that the flyback inverter in the present application refers to an inverter using flyback switching power supply technology. Flyback switching power supply refers to a switching power supply using a flyback high-frequency transformer to isolate the input and output circuits. "Flyback" (FLY BACK) specifically refers to when the switch tube is turned on, the output transformer acts as an inductor, and the electrical energy is converted into magnetic energy, at which time there is no current in the output circuit. On the contrary, when the switch tube is turned off, the output transformer releases energy, and the magnetic energy is converted into electrical energy, and there is current in the output circuit. Preferably, the inverter in the embodiment is a micro inverter, which can realize maximum power point tracking (MPPT) at the component level and has advantages over centralized inverters. In this way, the output power of each module can be optimized to maximize the overall output power.

[0074] As an implementation, as shown in FIG. 7, the flyback inverter specifically includes a transformer T, switch tubes S0-S2, filter capacitors C1-C3, thyristors SCR1-SCR2, diodes D1, and inductors L1. In the circuit structure of FIG. 7, MOS tubes or IGBT tubes are arranged as flyback switch tubes on the primary side and the secondary side of the transformer respectively, when the power grid absorbs power, the MOS tube S0 on the primary side of the transformer as the main switch stores power to the transformer, and the diode D1 on the secondary side of the transformer as the auxiliary switch rectifies; when the power grid sends out power, the MOS tube S0 on the primary side of the transformer as the auxiliary switch rectifies, and the diode D1 on the secondary side of the transformer as the main switch stores power to the transformer. The circuit structure in FIG. 7 further includes a photovoltaic panel, the photovoltaic panel provides an input voltage of the inverter, the high-frequency flyback switch S0 is composed of MOS tubes or IGBT tubes, S1 and S2 are output power frequency switch tubes, SCR1 and SCR2 are thyristors, the power frequency switch tube S1 and the thyristor SCR1 are connected in series, S2 and the thyristor SCR2 are connected in series, the series connection of S1 and the thyristor SCR1 is connected in parallel with the series connection of S2 and the thyristor SCR2, forming a power frequency switch structure as shown in FIG. 7, the output power frequency switch tubes are composed of MOS tubes or IGBT tubes, and the controller is connected to the power grid and the input end of the flyback inverter. It should be noted that the circuit diagram in the present application is for illustration, and the present application does not limit the specific structure of the circuit diagram.

[0075] The present application also discloses an inverter controller, which stores a computer program, and the computer program is executed by a processor to realize the method for controlling the power factor of the dual-frequency flyback inverter.

[0076] The beneficial effects of the technical scheme of the present application are that the power factor is adjusted by adjusting the phase difference between the first sinusoidal modulation wave and the sinusoidal correction modulation wave, the first sinusoidal modulation wave can work independently when the power supply only has active power, and the sinusoidal correction modulation wave can work independently when the power supply needs to adjust the reactive power. The flyback inverter is controlled by the sinusoidal correction modulation wave in the present application, so that the flyback inverter can accurately adjust the power factor when connected to the power grid, and the harmonic distortion rate is reduced.

[0077] The above is only part or preferred embodiments of the present application, neither the text nor the drawings can limit the scope of protection of the present application, any equivalent structural transformation made by using the content of the specification and drawings, or direct / indirect application in other related technical fields is included in the scope of protection of the present application.

Claims

1. A method for controlling the power factor of a dual-frequency flyback inverter grid-connected, characterized in that, The method comprises the following steps: obtaining an operating electrical signal of a target power grid; phase-locked the operating electrical signal to obtain a first sinusoidal modulation wave signal consistent with the initial phase and frequency of the operating electrical signal; obtaining a second sinusoidal modulation wave signal consistent with the frequency of the first sinusoidal modulation wave signal and having a phase angle difference with respect to the first sinusoidal modulation wave signal according to a preset power factor and the first sinusoidal modulation wave signal; obtaining a time difference corresponding to the phase angle difference according to the phase angle difference; obtaining a half-cycle time length of the first sinusoidal modulation wave signal, and obtaining a sinusoidal correction modulation frequency different from the frequency of the operating electrical signal through the difference between the half-cycle time length of the first sinusoidal modulation wave signal and the time difference; generating a sinusoidal correction modulation wave signal with the sinusoidal correction modulation frequency; controlling a flyback inverter to output target alternating current corresponding to the sinusoidal correction modulation wave signal to the target power grid or a power consumption device based on the sinusoidal correction modulation wave signal.

2. The method of claim 1, wherein, The method of generating a sinusoidal correction modulation wave signal with a sinusoidal correction modulation frequency comprises: generating a third sinusoidal modulation wave signal with the sinusoidal correction modulation frequency; obtaining a carrier signal, which is a triangular wave signal or a sawtooth wave signal; superimposing the third sinusoidal modulation wave signal and the carrier signal to obtain the sinusoidal correction modulation wave signal.

3. The method of claim 1, wherein, The method of generating a sinusoidal correction modulation wave signal with a sinusoidal correction modulation frequency comprises: when the waveform of the second sinusoidal modulation wave signal leads the voltage waveform of the first sinusoidal modulation wave signal, generating the sinusoidal correction modulation wave signal in a time period corresponding to the starting point of the half cycle of the first sinusoidal modulation wave signal to the ending point of the half cycle of the second sinusoidal modulation wave signal; when the waveform of the second sinusoidal modulation wave signal lags the voltage waveform of the first sinusoidal modulation wave signal, generating the sinusoidal correction modulation wave signal in a time period corresponding to the starting point of the half cycle of the second sinusoidal modulation wave signal to the ending point of the half cycle of the first sinusoidal modulation wave signal.

4. The method of claim 1, wherein, The method of obtaining a second sinusoidal modulation wave signal consistent with the frequency of the first sinusoidal modulation wave signal and having a phase angle difference with respect to the first sinusoidal modulation wave signal according to a preset power factor and the first sinusoidal modulation wave signal comprises: phase-shifting the first sinusoidal modulation wave signal according to a phase angle corresponding to the preset power factor to obtain the second sinusoidal modulation wave signal consistent with the frequency of the first sinusoidal modulation wave signal and having the phase angle difference with respect to the first sinusoidal modulation wave signal.

5. The method of claim 4, wherein, The method of phase-shifting the first sinusoidal modulation wave signal according to a phase angle corresponding to the preset power factor to obtain the second sinusoidal modulation wave signal consistent with the frequency of the first sinusoidal modulation wave signal and having the phase angle difference with respect to the first sinusoidal modulation wave signal comprises: When the load connected with the flyback inverter is an inductive load, the first sinusoidal modulation wave signal is phase-shifted in a lagging direction according to a phase angle corresponding to a preset power factor, to obtain the second sinusoidal modulation wave signal which has a same frequency as the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal. When the load connected with the flyback inverter is a capacitive load, the first sinusoidal modulation wave signal is phase-shifted in a leading direction according to a phase angle corresponding to a preset power factor, to obtain the second sinusoidal modulation wave signal which has a same frequency as the first sinusoidal modulation wave signal and has a phase angle difference with respect to the first sinusoidal modulation wave signal.

6. The method of controlling the power factor of a dual-frequency flyback inverter for grid connection according to any one of claims 1 to 4, characterized in that, The frequency of the working electrical signal is 50 Hz or 60 Hz.

7. The method of controlling the power factor of a dual-frequency flyback inverter for grid connection according to any one of claims 1 to 4, characterized in that, The control of the flyback inverter to output target alternating current corresponding to the sinusoidal correction modulation wave signal to a target power grid or a power consumption device includes: The control of the flyback inverter to output target alternating current corresponding to the sinusoidal correction modulation wave signal to a target power grid or a power consumption device includes:

8. The method of claim 2, wherein, The frequency of the carrier signal is greater than the frequency of the third sinusoidal modulation wave signal.

9. The method of claim 1 to 4, wherein, The sinusoidal correction modulation wave signal is an SPWM wave signal.

10. An inverter controller characterized by comprising: The inverter controller stores a computer program which is executed by a processor to implement the method for controlling the power factor of the flyback inverter connected to the target power grid or the power consumption device according to any one of claims 1 to 9.

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