Control method and control system for photovoltaic grid-connected power generation system

Abstract

The application discloses a control method and a control system of a photovoltaic grid-connected power generation system. The method comprises the following steps: a first selection switch determines a first control signal of each switch tube based on a stage of a current period of a grid voltage and a first output signal generated by a flip-flop; a calculation unit obtains a first voltage by subtracting a reference operating voltage of a photovoltaic panel from a direct current voltage; a proportional integral controller and a coordinate transformation unit process the first voltage in sequence to obtain a grid-connected current reference value; a first multiplier inputs an integrator after multiplying the direct current voltage and an inductance current determined by a second switch tube; a second multiplier multiplies the grid-connected current reference value and a voltage of the grid; a comparator generates a high-level input signal when an output of the integrator is greater than or equal to an output of the second multiplier; a flip-flop generates a second output signal based on the high-level input signal; and the first selection switch determines a second control signal corresponding to each switch tube based on the stage of the current period and the second output signal.

Description

Technical Field

[0001] This application relates to the field of photovoltaic grid-connected power generation system control technology, specifically to a control method and control system for a photovoltaic grid-connected power generation system. Background Technology

[0002] Solar power generation, as one of the most valuable renewable energy sources, has been applied in many fields. Its main utilization method is photovoltaic cell power generation, such as large-scale photovoltaic power plants, photovoltaic charging equipment, and building-integrated photovoltaics.

[0003] Current photovoltaic (PV) power generation applications increasingly favor a single-stage structure, primarily referring to a single-stage grid-connected system. In this structure, the system contains only one power conversion unit, namely the grid-connected inverter. Because it only has one power conversion unit, the system structure is relatively simple, requiring fewer components, reducing energy losses in intermediate stages, and improving overall system efficiency. However, while simplifying the system structure, it makes it more sensitive to environmental factors such as sunlight. In fact, during the process of converting solar energy into electrical energy, the DC output from the PV panels contains certain low-frequency pulsations. These pulsations become more pronounced when the environment changes, such as under partial shading or uneven lighting conditions. Traditional systems mainly rely on capacitors before the inverter for filtering; however, this cannot completely eliminate them. Furthermore, larger capacitors increase physical size and weight, and require higher-quality materials, thus increasing costs. The uneliminated low-frequency pulsations result in a large number of low-order harmonics in the output waveform of the grid-connected inverter. These harmonics cannot be filtered out by filters. Directly applying this output voltage waveform to a practical system will cause significant pollution to the power grid and pose numerous hazards to electrical equipment.

[0004] Therefore, it is essential to take certain measures to suppress the waveform distortion caused by this. Summary of the Invention

[0005] This application provides a control method and control system for a photovoltaic grid-connected power generation system, which improves the suppression effect of low-frequency pulsation in the DC power output from the photovoltaic panel on the DC side, thereby suppressing the distortion of the output voltage waveform and reducing pollution to the power grid.

[0006] In a first aspect, this application provides a control method for a photovoltaic grid-connected power generation system. This method is applied to the control system of the photovoltaic grid-connected power generation system. The control system includes a maximum power point tracking unit, an arithmetic unit, a proportional-integral controller, a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger. The photovoltaic grid-connected power generation system includes photovoltaic panels, an inverter, and a power grid. The inverter includes multiple switching transistors and multiple inductors. The method includes:

[0007] The flip-flop generates a first output signal based on the high-level clock signal currently received at the set input terminal, wherein the output terminal of the flip-flop is at a high level and the inverting output terminal is at a low level in the first output signal;

[0008] The first selection switch determines the first control signal corresponding to each switch tube in the current cycle stage based on the voltage of the power grid in the current cycle stage and the first output signal.

[0009] The maximum power point tracking unit determines the reference operating voltage of the photovoltaic panel at the maximum power point;

[0010] The arithmetic unit calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain the first voltage;

[0011] The proportional-integral controller processes the first voltage to obtain the first current;

[0012] The coordinate transformation unit performs coordinate transformation on the first current and the preset second current to obtain the grid-connected current reference value;

[0013] The second selection switch determines the inductor current based on the grid voltage at the current cycle stage, where the inductor current is one of multiple currents corresponding to multiple inductors;

[0014] The first multiplier multiplies the DC voltage and inductor current output by the photovoltaic panel and then inputs the result into the integrator; the second multiplier multiplies the grid-connected current reference value and the grid voltage.

[0015] The comparator compares the output of the second multiplier and the output of the integrator. When the output of the integrator is greater than or equal to the output of the second multiplier, a high-level input signal is generated at the reset input of the flip-flop.

[0016] The trigger generates a second output signal based on a high-level input signal at the reset input terminal, wherein the inverting output terminal of the trigger is high and the output terminal is low in the second output signal;

[0017] The first selection switch determines the second control signal corresponding to each switch tube in the current cycle stage based on the grid voltage and the second output signal.

[0018] Secondly, this application provides a control system for a photovoltaic grid-connected power generation system. The control system includes a maximum power point tracking unit, an arithmetic unit, a proportional-integral controller, a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger.

[0019] A flip-flop is used to generate a first output signal based on a high-level clock signal currently received at the set input terminal, wherein the output terminal of the flip-flop is high-level and the inverting output terminal is low-level in the first output signal;

[0020] A first selection switch is used to determine a first control signal corresponding to each of a plurality of switching transistors in the current cycle based on the voltage of the power grid in the current cycle and a first output signal, wherein the plurality of switching transistors are multiple switching transistors in the inverter of the photovoltaic power generation system.

[0021] The maximum power point tracking unit is used to determine the reference operating voltage of the photovoltaic panel in the photovoltaic power generation system at the maximum power point; the arithmetic unit is used to calculate the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain the first voltage; the proportional-integral controller is used to process the first voltage to obtain the first current; the coordinate transformation unit is used to perform coordinate transformation on the first current and the preset second current to obtain the grid-connected current reference value.

[0022] The second selector switch is used to determine the inductor current based on the voltage of the grid in the photovoltaic power generation system at the current cycle stage, wherein the inductor current is one of multiple currents corresponding to multiple inductors in the inverter.

[0023] The first multiplier is used to multiply the DC voltage and inductor current output by the photovoltaic panel and then input them into the integrator; the second multiplier is used to multiply the grid-connected current reference value and the grid voltage.

[0024] The comparator is used to compare the output of the second multiplier and the output of the integrator. When the output of the integrator is greater than or equal to the output of the second multiplier, a high-level input signal is generated at the reset input of the flip-flop.

[0025] The flip-flop is also used to generate a second output signal based on a high-level input signal at the reset input terminal, wherein the inverting output terminal of the flip-flop is high and the output terminal is low in the second output signal;

[0026] The first selection switch is also used to determine the second control signal corresponding to each switch tube in the current cycle stage based on the voltage of the power grid in the current cycle stage and the second output signal.

[0027] Thirdly, this application provides a photovoltaic power generation system; the photovoltaic power generation system includes a photovoltaic panel, a capacitor, an inverter, a filter, and a power grid; the inverter includes a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a first inductor, a second inductor, a first device, and a second device;

[0028] The two ends of the capacitor are connected to the two ends of the photovoltaic panel; the other ends of the first switch transistor, the other ends of the fourth switch transistor, one end of the third switch transistor, and one end of the sixth switch transistor are all connected to one end of the capacitor; one end of the fifth switch transistor and one end of the second switch transistor are all connected to the other end of the capacitor.

[0029] One end of the second device is connected to the other end of the second inductor and the other end of the fifth switch. The other ends of the second device and the third switch are both connected to one end of the filter. One end of the first device is connected to the other end of the second switch and the other end of the first inductor. The other ends of the first device and the sixth switch are both connected to the other end of the filter. Both ends of the filter are connected to the power grid.

[0030] Implementing this application will have the following beneficial effects:

[0031] The control method and control system for a photovoltaic grid-connected power generation system provided in this application include a maximum power point tracking unit, an arithmetic unit, a proportional-integral controller, a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger. The photovoltaic grid-connected power generation system includes photovoltaic panels, an inverter, and a power grid. The inverter includes multiple switching transistors and multiple inductors. A high-level clock signal can be sent to the set input of the trigger at a preset frequency. Then, the trigger generates a first output signal based on the high-level clock signal currently received at the set input. The first output signal contains... The trigger output is high and the inverting output is low. Then, the first selection switch, based on the grid voltage at the current cycle stage and the first output signal, determines the first control signal corresponding to each switch at the current cycle stage. Accordingly, each switch can be turned on or off based on the corresponding first control signal. The maximum power point tracking unit determines the reference operating voltage of the photovoltaic panel at its maximum power point. The arithmetic unit calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain the first voltage. The proportional-integral controller processes the first voltage to obtain the first current. The coordinate transformation unit calculates the difference between the first current and a preset second current. The current is transformed into a coordinate system to obtain the grid-connected current reference value. The second selection switch determines the inductor current based on the grid voltage at the current cycle stage; the inductor current is one of multiple currents corresponding to multiple inductors. Then, the first multiplier multiplies the DC voltage output from the photovoltaic panel and the inductor current, and inputs the result to the integrator. The second multiplier multiplies the grid-connected current reference value and the grid voltage. Then, the comparator compares the outputs of the second multiplier and the integrator; when the integrator's output is greater than or equal to the second multiplier's output, a high-level input signal is generated at the reset input of the trigger. Then, the trigger is based on the reset input... A high-level input signal generates a second output signal, wherein the inverting output terminal of the trigger in the second output signal is high and the output terminal is low. Then, the first selection switch determines the second control signal corresponding to each switch in the current cycle based on the grid voltage and the second output signal. Accordingly, each switch is turned on or off based on the corresponding second control signal. In a photovoltaic grid-connected power generation system, the DC power output from the photovoltaic panel needs to be converted into AC power for the grid. Since the output DC power will have low-frequency pulsations, if they are not filtered out, the waveform of the final output AC power will be distorted.

[0032] In other words, through the above control method, using a single cycle as the granularity, the inverter's switching transistors are first controlled to turn on or off based on the grid voltage during the current cycle phase (positive or negative half-cycle phase) and the received clock signal. The maximum power point tracking (MPPT) unit then adjusts the operating point in real time based on the photovoltaic panel's output voltage and current, ensuring the photovoltaic system always operates at its maximum power point and avoiding operation in the nonlinear region, which helps reduce low-order harmonics. Then, the proportional-integral (PI) controller processes the voltage error (i.e., the first voltage) and generates a corresponding current. This feedback mechanism ensures a smoother current waveform and reduces harmonic generation. Finally, the coordinate transformation unit compares the first current with a preset... The two currents undergo coordinate transformation to avoid generating low-order harmonics caused by phase mismatch. Then, the trigger and comparator can be adjusted in real time according to changes in grid voltage or output current. Under the action of the comparator, when the system finds that the current or voltage waveform in a certain state does not meet expectations, if the output value of the integrator is greater than or equal to the output of the second multiplier (usually related to the grid voltage), a reset signal will be issued. The trigger adjusts its output according to this signal, which helps to smooth the system response and can adjust the inverter output in real time, so that the photovoltaic current waveform is as close as possible to the ideal sine wave, suppressing low-order harmonics, thereby improving the quality of grid-connected current and avoiding the impact of harmonics on the power system. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 A schematic diagram of a photovoltaic grid-connected power generation system provided in an embodiment of this application;

[0035] Figure 2 A schematic diagram of a control system for a photovoltaic grid-connected power generation system provided in an embodiment of this application;

[0036] Figure 3 This is a control schematic diagram of a photovoltaic grid-connected power generation system provided in an embodiment of this application. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0039] In this document, the term "embodiment" means that a particular feature, result, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] First, the relevant terms used in this application will be explained:

[0041] Maximum power point tracking (MPPT) is a technology commonly used in wind turbines and photovoltaic solar energy systems, with the aim of achieving maximum power output under various conditions.

[0042] Proportional-integral controller (PI): It achieves precise control of the system output through proportional and integral regulation. Its principle can be roughly divided into (1) Input signal processing: The PI controller receives the actual value measured by the sensor and compares it with the set value to obtain the deviation signal; (2) Proportional regulation: The deviation signal is multiplied by the proportional coefficient to obtain the proportional control signal; (3) Integral regulation: The deviation signal is integrated to obtain the integral control signal; (4) Control signal synthesis: The proportional control signal and the integral control signal are added to obtain the final control signal; (5) Output signal processing: The control signal is converted and amplified appropriately and output to the actuator to realize the control of the system.

[0043] Trigger: This application mainly refers to the RS trigger.， Includes a set input (denoted as S), a reset input (denoted as R), an output (denoted as Q), and an inverting output (denoted as...). ).

[0044] First, this application does not limit the types of the switching transistor, the first device, and the second device. The embodiments of this application mainly use a transistor as the switching transistor and diodes as the first device and the second device as examples for explanation and illustration.

[0045] The following section provides an example illustration of the photovoltaic grid-connected power generation system and its control system, using diagrams as examples.

[0046] See Figure 1 , Figure 1 This is a schematic diagram of a photovoltaic grid-connected power generation system provided in an embodiment of this application.

[0047] like Figure 1 The photovoltaic grid-connected power generation system shown includes photovoltaic panels (denoted as PV), capacitors (denoted as C), an inverter, a filter, and a power grid. The inverter includes multiple switching transistors, multiple inductors, and a first device (corresponding to...). Figure 1 Diode D1 in the middle), the second device (corresponding to) Figure 1 Diode D2 in the middle); multiple switching transistors including the first switching transistor (corresponding to Figure 1 The transistor Q1), the second switching transistor (corresponding to) Figure 1 The transistor Q2), the third switching transistor (corresponding to) Figure 1 The transistor Q3), the fourth switching transistor (corresponding to) Figure 1 Transistor Q4), the fifth switch (corresponding to) Figure 1 Transistor Q5), the sixth switch (corresponding to) Figure 1 Transistor Q6); multiple inductors including the first inductor (corresponding to...) Figure 1 L1 in the middle), the second inductor (corresponding to) Figure 1 L2 in the middle.

[0048] The two ends of capacitor C are connected to the photovoltaic panel (denoted as PV); one end of the first switching transistor is connected to one end of the first inductor, and one end of the fourth switching transistor is connected to one end of the second inductor; the other ends of the first switching transistor, the fourth switching transistor, the third switching transistor, and the sixth switching transistor are all connected to one end of the capacitor; one end of the fifth switching transistor and one end of the second switching transistor are both connected to the other end of the capacitor; one end of the second device is connected to the other end of the second inductor and the other end of the fifth switching transistor, and the other ends of the second device and the third switching transistor are both connected to one end of the filter; one end of the first device is connected to the other end of the second switching transistor and the other end of the first inductor, and the other ends of the first device and the sixth switching transistor are both connected to the other end of the filter; the two ends of the filter are connected to the power grid.

[0049] See Figure 2 , Figure 2 This is a schematic diagram of a control system for a photovoltaic grid-connected power generation system provided in an embodiment of this application.

[0050] Figure 2 The control system of the photovoltaic grid-connected power generation system shown includes a maximum power point tracking unit (MPPT), an arithmetic unit, a proportional-integral controller (PI), a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger.

[0051] The first selection switch includes multiple output terminals corresponding to multiple switching transistors, each output terminal being used to connect to its corresponding switching transistor; the output terminal (i.e., the Q terminal) and the inverting output terminal (… All terminals (R, S, S) are connected to the input terminals of the first selection switch; the reset input terminal of the flip-flop (R) is connected to the output terminal of the comparator; the set input terminal of the flip-flop (S) is used to receive a clock signal, such as from an external clock circuit, etc., and this application does not limit the source of the clock signal; the first input terminal of the comparator (i.e., the corresponding...) Figure 2 The "-" terminal of the comparator is connected to the output of the second multiplier; the second input terminal of the comparator (i.e., the corresponding...) Figure 2 The "+" terminal of the comparator is connected to the output terminal of the integrator; the input terminal of the integrator is connected to the output terminal of the first multiplier; the inverted output terminal of the flip-flop is also connected to the integrator; the input terminal of the first multiplier is connected to the second selection switch.

[0052] A trigger is used to generate a first output signal based on a high-level clock signal currently received at the set input terminal, wherein the output terminal of the trigger is high-level and the inverting output terminal is low-level in the first output signal; a first selection switch is used to determine a first control signal corresponding to each of the multiple switching transistors in the current cycle based on the voltage of the power grid in the current cycle stage and the first output signal, wherein the multiple switching transistors are multiple switching transistors in the inverter of the photovoltaic power generation system.

[0053] The maximum power point tracking unit receives the voltage and current of the photovoltaic panel and determines the reference operating voltage of the photovoltaic panel at the maximum power point. Then, the arithmetic unit calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain a first voltage. Then, the proportional-integral controller processes the first voltage to obtain a first current. Then, the coordinate transformation unit performs coordinate transformation on the first current and a preset second current to obtain a grid-connected current reference value.

[0054] The second selection switch is used to receive the current of the first inductor or the second inductor in the photovoltaic grid-connected power generation system based on the voltage of the grid in the photovoltaic power generation system at the current cycle stage, and determine it as the inductor current, wherein the inductor current is one of the multiple currents corresponding to multiple inductors in the inverter; then the first multiplier is used to multiply the DC voltage output by the photovoltaic panel and the inductor current and then input it to the integrator.

[0055] The system includes a second multiplier, which receives the grid voltage and grid-connected current reference values ​​and multiplies them; a comparator, which compares the output of the second multiplier with the output of the integrator. When the output of the integrator is greater than or equal to the output of the second multiplier, a high-level input signal is generated at the reset input of the flip-flop.

[0056] The trigger is also used to generate a second output signal based on a high-level input signal from the reset input terminal, wherein the inverting output terminal of the trigger is high and the output terminal is low in the second output signal; then the first selection switch is also used to determine a second control signal corresponding to each switch transistor in the current cycle stage based on the voltage of the power grid in the current cycle stage and the second output signal.

[0057] In one optional embodiment, the plurality of switching transistors includes a first switching transistor group and a second switching transistor group; the first switching transistor group includes a first switching transistor, a second switching transistor, and a third switching transistor; the second switching transistor includes a fourth switching transistor, a fifth switching transistor, and a sixth switching transistor; regarding the first selection switch determining the first control signal corresponding to each switching transistor in the current cycle phase based on the grid voltage in the current cycle phase and a first output signal, when the grid voltage is in the positive half-cycle phase of the current cycle, the first selection switch is further configured to determine, based on the first output signal, that the first control signals corresponding to the first switching transistor and the second switching transistor are conduction signals, and further configured to determine that the first control signals corresponding to the third switching transistor, the fourth switching transistor, the fifth switching transistor, and the sixth switching transistor are deactivation signals. When the grid voltage is in the negative half-cycle phase of the current cycle, the first selection switch is further configured to determine, based on the first output signal, that the first control signals corresponding to the fourth switching transistor and the fifth switching transistor are conduction signals, and further configured to determine that the first control signals corresponding to the first switching transistor, the second switching transistor, the third switching transistor, and the sixth switching transistor are deactivation signals.

[0058] In one optional embodiment, the plurality of inductors includes a first inductor and a second inductor; one end of a first switching transistor is connected to one end of the first inductor, and one end of a fourth switching transistor is connected to one end of the second inductor; when the voltage of the mains grid is in the positive half-cycle of the current cycle, the inductor current is the current corresponding to the first inductor; when the voltage of the mains grid is in the negative half-cycle of the current cycle, the inductor current is the current corresponding to the second inductor.

[0059] In an optional embodiment, regarding the first selection switch determining the second control signal corresponding to each switch transistor in the current cycle phase based on the grid voltage in the current cycle phase and the second output signal, when the grid voltage is in the positive half-cycle phase of the current cycle, the first selection switch determines, based on the second output signal, that the second control signals corresponding to the first and third switches transistors are turn-on signals, and determines that the second control signals corresponding to the second, fourth, fifth, and sixth switches transistors are turn-off signals;

[0060] When the grid voltage is in the negative half-cycle of the current cycle, the first selector switch determines, based on the second output signal, that the second control signals corresponding to the fourth and sixth switches are turn-on signals, and determines that the second control signals corresponding to the first, second, third, and fifth switches are turn-off signals.

[0061] In an alternative embodiment, after generating the second output signal, the integrator is further configured to receive notification information for the second output signal from the inverting output of the flip-flop, and then the integrator is further configured to clear the current integration result so that if a high-level clock signal is received again at the set input of the flip-flop, the integrator can start integrating again to obtain the second control signal corresponding to each switch.

[0062] It should be noted that, Figure 2 The steps and principles performed by each structure in the control system shown are not limited to the above embodiments, and can also be described in the corresponding descriptions of the method embodiments below, which will not be elaborated in detail here.

[0063] To facilitate understanding, the following will be combined with... Figure 1 and Figure 2 For an example, see [link to example]. Figure 3 , Figure 3 This application provides a control schematic diagram of a photovoltaic grid-connected power generation system, and in conjunction with... Figure 3 The embodiments illustrate the control method of the photovoltaic grid-connected power generation system of this application. This control method is applied to the control system of the photovoltaic grid-connected power generation system in the above embodiments, and will not be repeated here. The control method specifically includes, but is not limited to, steps S11-S22:

[0064] S11. The flip-flop generates the first output signal based on the high-level clock signal currently received at the set input terminal.

[0065] In the embodiments of this application, the transmission frequency of the clock signal can be preset. At the beginning, when the S terminal of the flip-flop receives the clock signal (generally high level), the circuit in the photovoltaic grid-connected power generation system starts to operate. At the start of a cycle, the flip-flop generates a first output signal based on the currently received high-level clock signal. In the first output signal, the output terminal of the flip-flop is high level and the inverted output terminal is low level.

[0066] S12. The first selection switch determines the first control signal corresponding to each switch tube in the current cycle stage based on the voltage of the power grid in the current cycle stage and the first output signal.

[0067] The plurality of switching transistors includes a first switching transistor group and a second switching transistor group; the first switching transistor group includes a first switching transistor, a second switching transistor, and a third switching transistor; the second switching transistor includes a fourth switching transistor, a fifth switching transistor, and a sixth switching transistor. It should be noted that the period of this application is similar to the transformation of a sine curve; in each period, a value greater than zero represents the positive half-cycle of the period, and a value less than zero represents the negative half-cycle of the period. For example:

[0068] When the grid voltage is in the positive half-cycle of the current cycle, the first selector switch determines, based on the first output signal, that the first control signals corresponding to the first and second switching transistors are turn-on signals, and determines that the first control signals corresponding to the third, fourth, fifth, and sixth switching transistors are turn-off signals. That is, at this time, Q1 and Q2 are turned on, and Q3, Q4, Q5, and Q6 are turned off.

[0069] When the grid voltage is in the negative half-cycle of the current cycle, the first selector switch determines, based on the first output signal, that the first control signals corresponding to the fourth and fifth switches are turn-on signals, and determines that the first control signals corresponding to the first, second, third, and sixth switches are turn-off signals. That is, at this time, Q4 and Q5 are turned on, and Q1, Q2, Q3, and Q6 are turned off.

[0070] S13. The maximum power point tracking unit determines the reference operating voltage of the photovoltaic panel at the maximum power point.

[0071] S14. The arithmetic unit calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain the first voltage.

[0072] S15, the proportional-integral controller processes the first voltage to obtain the first current.

[0073] S16. The coordinate transformation unit performs coordinate transformation on the first current and the preset second current to obtain the grid-connected current reference value.

[0074] At the same time, the maximum power point tracking unit receives the voltage u from the photovoltaic panel. PV and current i PV And based on voltage u PV and current i PV Determine the reference operating voltage u of the photovoltaic panel at its maximum power point. dcref The arithmetic unit then calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain the first voltage; the proportional-integral controller then processes the first voltage to obtain the first current i. dref Then the coordinate transformation unit transforms the first current and the preset second current i. qref Perform coordinate transformation to obtain the grid-connected current reference value i. ref .

[0075] S17. The second selection switch determines the inductor current based on the grid voltage at the current cycle stage.

[0076] At the same time, the second selection switch determines the inductor current i based on the grid voltage at the current cycle stage. L Wherein, the inductor current is one of the multiple currents corresponding to multiple inductors, that is, the inductor current is i. L1 i L2 One of the four switches is connected; one end of the first switch is connected to one end of the first inductor, and one end of the fourth switch is connected to one end of the second inductor. When the grid voltage is in the positive half-cycle of the current period, the inductor current is the current corresponding to the first inductor; when the grid voltage is in the negative half-cycle of the current period, the inductor current is the current corresponding to the second inductor. Since Q1 and Q2 are on and Q3, Q4, Q5, and Q6 are off, meaning the grid voltage is in the positive half-cycle of the current period, the inductor current i... L Just for i L1 .

[0077] S18. The first multiplier multiplies the DC voltage and inductor current output by the photovoltaic panel and then inputs the result to the integrator.

[0078] S19, the second multiplier multiplies the grid-connected current reference value and the grid voltage.

[0079] The first multiplier applies DC voltage u output from the photovoltaic panel. dc Inductor current i L After multiplication, the product is input to the integrator; and the second multiplier is used to input the grid-connected current reference value i. ref The voltage u of the power grid grid Perform product processing.

[0080] S20. The comparator compares the output of the second multiplier and the output of the integrator. When the output of the integrator is greater than or equal to the output of the second multiplier, a high-level input signal is generated at the reset input of the flip-flop.

[0081] The comparator compares the outputs of the second multiplier and the integrator to obtain the reset input signal for the flip-flop. When the integrator's output is greater than or equal to the second multiplier's output, the reset input signal is high; when the integrator's output is less than the second multiplier's output, the reset input signal is low. The control equations in the control system satisfy Equation 1:

[0082]

[0083] Among them, u grid It is the voltage of the power grid; i ref This is the grid-connected current reference value; u dc It is the DC-side voltage output by the photovoltaic panel; i L It is the inductor current, i, when it is in the positive half-cycle of the cycle. L For i L1 When it is the negative half-cycle phase of the cycle, i L For i L1 T is the switching period.

[0084] S21. The trigger generates a second output signal based on the high-level input signal at the reset input terminal.

[0085] When the output of the integrator is greater than or equal to the output of the second multiplier, the flip-flop generates a second output signal based on the high-level input signal at the reset input terminal. In the second output signal, the inverting output terminal of the flip-flop is at a high level and the output terminal is at a low level.

[0086] S22. The first selection switch determines the second control signal corresponding to each switch tube in the current cycle stage based on the voltage of the power grid and the second output signal.

[0087] For example, when the grid voltage is in the positive half-cycle of the current cycle, the first selector switch determines, based on the second output signal, that the second control signals corresponding to the first and third switches are turn-on signals, and determines that the second control signals corresponding to the second, fourth, fifth, and sixth switches are turn-off signals. That is, at this time, the turn-on and turn-off status of the switches is switched from Q1 and Q2 being on and Q3, Q4, Q5, and Q6 being off to Q1 and Q3 being on and Q2, Q4, Q5, and Q6 being off.

[0088] When the grid voltage is in the negative half-cycle of the current cycle, the first selector switch determines, based on the second output signal, that the second control signals corresponding to the fourth and sixth switches are turn-on signals, and that the second control signals corresponding to the first, second, third, and fifth switches are turn-off signals. That is, at this time, the turn-on and turn-off status of the switches is switched from Q4 and Q5 being on and Q1, Q2, Q3, and Q6 being off to Q4 and Q6 being on and Q1, Q2, Q5, and Q6 being off.

[0089] Of course, when the integrator's output is less than the second multiplier's output, the trigger generates a third output signal based on the low-level input signal at the reset input. At this time, the third output signal is consistent with the first output signal, with the trigger's output terminal still at a high level and its inverting output terminal at a low level. Then, the principle of the first selection switch determining the second control signal corresponding to each switch in the current cycle based on the grid voltage and the third output signal is similar to the principle of the first selection switch determining the first control signal corresponding to each switch in the current cycle based on the grid voltage and the first output signal, and will not be repeated here.

[0090] Of course, if the trigger generates a second output signal, the integrator can also receive notification information for the second output signal from the trigger. Then the integrator clears the current integration result so that when a high-level clock signal is received again at the set input of the trigger, the integrator can start integrating again to obtain the second control signal corresponding to each switch.

[0091] In other words, when the set input of the trigger receives a high-level clock signal, a cycle begins. If this cycle starts from the positive half-cycle (i.e., the grid voltage is in the positive half-cycle phase), and the trigger outputs a high level while the inverting output outputs a low level, then switches Q1 and Q2 are turned on, and Q3, Q4, Q5, and Q6 are turned off. Simultaneously, the second selection switch determines the inductor current to be the current corresponding to L1. Then, the second multiplier, first multiplier, integrator, comparator, etc., sequentially execute the corresponding steps according to the principle of the above embodiment. If the output of the integrator is greater than or equal to the output of the second multiplier, the trigger is reset, its output is low, and the inverting output is high. Correspondingly, switches Q1 and Q3 are turned on, and Q2, Q4, Q5, and Q6 are turned off. The integrator also clears the current integration result to zero until the current... During the positive half-cycle of the cycle, the S-terminal of the flip-flop receives a high-level clock signal again, and steps S11-S22 are repeated. That is, the flip-flop outputs a high level, and the inverting output outputs a low level. Correspondingly, it controls the switching transistors Q1 and Q2 to turn on, and Q3, Q4, Q5, and Q6 to turn off. The second selection switch determines the inductor current as the current corresponding to L2, and the subsequent steps are executed in sequence. If the output of the integrator is greater than or equal to the output of the second multiplier, the flip-flop is reset, the flip-flop outputs a low level, and the inverting output outputs a high level. Correspondingly, it controls the switching transistors Q1 and Q3 to turn on, and Q2, Q4, Q5, and Q6 to turn off. The integrator also clears the current integration result to zero. This process continues until the S-terminal of the flip-flop receives a high-level clock signal again during the positive half-cycle of the cycle, and steps S11-S22 are repeated.

[0092] In short, since the clock signal is sent at a preset frequency, the S-terminal of the flip-flop can receive multiple high-level clock signals during the positive half-cycle of a cycle. When the high-level clock signal is received for the first time, the switches Q1 and Q2 are turned on, while Q3, Q4, Q5, and Q6 are turned off. Then, the integrator continuously integrates based on the above principle until the output of the integrator is greater than or equal to the output of the second multiplier (which can also be understood as the left side of the above formula (1) being greater than or equal to the right side). The flip-flop is then reset, and correspondingly, the switches Q1 and Q3 are turned on. Q2, Q4, Q5, and Q6 are turned off. Then, when a high-level clock signal is received for the second time, the switches Q1 and Q2 are turned on, while Q3, Q4, Q5, and Q6 are turned off. This process continues until Q1 and Q3 are turned on, while Q2, Q4, Q5, and Q6 are turned off. Similarly, during the third, fourth, ... Nth high-level clock signal received in the positive half-cycle of a cycle, the principle is the same. Ultimately, during the positive half-cycle of a cycle, Q4, Q5, and Q6 are always turned off, Q1 is always turned on, and Q2 and Q3 are turned on alternately.

[0093] Furthermore, similarly, when the clock signal enters the negative half-cycle of a cycle from the positive half-cycle, the S-terminal of the flip-flop can still receive multiple high-level clock signals. Upon receiving the first high-level clock signal, switches Q4 and Q5 are turned on, while Q1, Q2, Q3, and Q6 are turned off. The integrator then integrates continuously based on the above principle until its output is greater than or equal to the output of the second multiplier (which can also be understood as the left side of formula (1) being greater than or equal to the right side). The flip-flop is then reset, and correspondingly, switches Q4 and Q6 are turned on. Q1, Q2, Q3, and Q5 are turned off. Then, when a high-level clock signal is received for the second time, the switches Q4 and Q5 are turned on, while Q1, Q2, Q3, and Q6 are turned off. This process continues until the switches Q4 and Q6 are turned on, while Q1, Q2, Q3, and Q5 are turned off. Similarly, during the negative half-cycle of a cycle, the same principle applies when a high-level clock signal is received for the third, fourth, ..., Nth time. Ultimately, during the negative half-cycle of a cycle, Q1, Q2, and Q3 are always turned off, Q4 is always turned on, and Q5 and Q6 are turned on alternately.

[0094] Furthermore, it enters the positive half-cycle phase of the next cycle, and so on. This process will not be elaborated on here. It achieves single-cycle control and has a better effect on suppressing low-order harmonics.

[0095] The control method and control system for a photovoltaic grid-connected power generation system provided in this application include a maximum power point tracking unit, an arithmetic unit, a proportional-integral controller, a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger. The photovoltaic grid-connected power generation system includes photovoltaic panels, an inverter, and a power grid. The inverter includes multiple switching transistors and multiple inductors. A high-level clock signal can be sent to the set input of the trigger at a preset frequency. Then, the trigger generates a first output signal based on the high-level clock signal currently received at the set input. The first output signal contains... The trigger output is high and the inverting output is low. Then, the first selection switch, based on the grid voltage at the current cycle stage and the first output signal, determines the first control signal corresponding to each switch at the current cycle stage. Accordingly, each switch can be turned on or off based on the corresponding first control signal. The maximum power point tracking unit determines the reference operating voltage of the photovoltaic panel at its maximum power point. The arithmetic unit calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain the first voltage. The proportional-integral controller processes the first voltage to obtain the first current. The coordinate transformation unit calculates the difference between the first current and a preset second current. The current is transformed into a coordinate system to obtain the grid-connected current reference value. The second selection switch determines the inductor current based on the grid voltage at the current cycle stage; the inductor current is one of multiple currents corresponding to multiple inductors. Then, the first multiplier multiplies the DC voltage output from the photovoltaic panel and the inductor current, and inputs the result to the integrator. The second multiplier multiplies the grid-connected current reference value and the grid voltage. Then, the comparator compares the outputs of the second multiplier and the integrator; when the integrator's output is greater than or equal to the second multiplier's output, a high-level input signal is generated at the reset input of the trigger. Then, the trigger is based on the reset input... A high-level input signal generates a second output signal, wherein the inverting output terminal of the trigger in the second output signal is high and the output terminal is low. Then, the first selection switch determines the second control signal corresponding to each switch in the current cycle based on the grid voltage and the second output signal. Accordingly, each switch is turned on or off based on the corresponding second control signal. In a photovoltaic grid-connected power generation system, the DC power output from the photovoltaic panel needs to be converted into AC power for the grid. Since the output DC power will have low-frequency pulsations, if they are not filtered out, the waveform of the final output AC power will be distorted.

[0096] As can be seen, the above control method, using a single-cycle granularity, controls the switching of each transistor in the inverter based on the grid voltage during the current cycle (positive or negative half-cycle phase) and the received clock signal. The maximum power point tracking (MPPT) unit then adjusts the operating point in real-time based on the photovoltaic panel's output voltage and current, ensuring the photovoltaic system always operates at its maximum power point and avoiding operation in the nonlinear region, which helps reduce low-order harmonics. The proportional-integral (PI) controller then processes the voltage error (first voltage) to generate a corresponding current. This feedback mechanism ensures a smoother current waveform and reduces harmonic generation. Finally, the coordinate transformation unit transforms the first current and a preset second current to avoid phase mismatch. The low-order harmonics caused by this; then the trigger and comparator can be adjusted in real time according to the changes in grid voltage or output current. Under the action of the comparator, when the system finds that the current or voltage waveform in a certain state does not meet expectations, if the output value of the integrator is greater than or equal to the output of the second multiplier (usually related to the grid voltage), a reset signal will be issued. The trigger adjusts its output according to this signal, and then allows each switch to be turned on alternately in the positive half-cycle or negative half-cycle of a single cycle, and adjusts the output of the inverter in real time to ensure that the left side of the above formula (1) is less than or equal to the right side, so that the photovoltaic current waveform is as close as possible to the ideal sine wave, suppressing low-order harmonics, thereby improving the quality of grid-connected current and avoiding the impact of harmonics on the power system.

[0097] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to this application.

[0098] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed apparatus can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical or other forms.

[0100] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0101] Furthermore, the functional units in the various embodiments of this application 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. The integrated unit can be implemented in hardware or as a software program module.

[0102] If the integrated unit is implemented as a software program module and sold or used as an independent product, it can be stored in a computer-readable storage device (CMD). Based on this understanding, the technical solution of this application, in essence, 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. This computer software product is stored in a memory and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned memory includes various media capable of storing program code, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard drive, magnetic disk, or optical disk.

[0103] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include: flash drive, read-only memory (ROM), random access memory (RAM), disk or optical disk, etc.

[0104] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A control method for a photovoltaic grid-connected power generation system, characterized in that, A control system applied to a photovoltaic grid-connected power generation system; the control system includes a maximum power point tracking unit, an arithmetic unit, a proportional-integral controller, a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger; the photovoltaic grid-connected power generation system includes photovoltaic panels, an inverter, and a power grid; the inverter includes multiple switching transistors and multiple inductors; The plurality of switching transistors includes a first switching transistor group and a second switching transistor group; the first switching transistor group includes a first switching transistor, a second switching transistor, and a third switching transistor; the second switching transistor includes a fourth switching transistor, a fifth switching transistor, and a sixth switching transistor; The method includes: The trigger generates a first output signal based on the high-level clock signal currently received at the set input terminal, wherein the output terminal of the trigger is at a high level and the inverting output terminal is at a low level in the first output signal; The first selection switch, based on the grid voltage at the current cycle stage and the first output signal, determines the first control signal corresponding to each switch transistor at the current cycle stage, including: When the voltage of the power grid is in the positive half-cycle of the current cycle, the first selection switch determines, based on the first output signal, that the first control signals corresponding to the first switch and the second switch are turn-on signals, and determines that the first control signals corresponding to the third switch, the fourth switch, the fifth switch, and the sixth switch are turn-off signals; When the voltage of the power grid is in the negative half-cycle of the current cycle, the first selection switch determines, based on the first output signal, that the first control signals corresponding to the fourth switch and the fifth switch are conduction signals, and determines that the first control signals corresponding to the first switch, the second switch, the third switch, and the sixth switch are deactivation signals; The maximum power point tracking unit determines the reference operating voltage of the photovoltaic panel at the maximum power point; The arithmetic unit calculates the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain a first voltage; The proportional-integral controller processes the first voltage to obtain the first current; The coordinate transformation unit performs coordinate transformation on the first current and the preset second current to obtain the grid-connected current reference value. The second selection switch determines the inductor current based on the voltage of the power grid in the current cycle phase, wherein the inductor current is one of the multiple currents corresponding to the plurality of inductors; The first multiplier multiplies the DC voltage output by the photovoltaic panel and the inductor current, and then inputs the product into the integrator. The second multiplier multiplies the grid-connected current reference value and the grid voltage. The comparator compares the output of the second multiplier and the output of the integrator. When the output of the integrator is greater than or equal to the output of the second multiplier, a high-level input signal is generated at the reset input terminal of the flip-flop. The trigger generates a second output signal based on the high-level input signal at the reset input terminal, wherein the inverting output terminal of the trigger is high-level and the output terminal is low-level in the second output signal; The first selection switch determines the second control signal corresponding to each switch tube in the current cycle stage based on the voltage of the power grid in the current cycle stage and the second output signal.

2. The method according to claim 1, characterized in that, The plurality of inductors includes a first inductor and a second inductor; one end of the first switching transistor is connected to one end of the first inductor, and one end of the fourth switching transistor is connected to one end of the second inductor; When the voltage of the power grid is in the positive half-cycle of the current cycle, the inductor current is the current corresponding to the first inductor. When the grid voltage is in the negative half-cycle of the current cycle, the inductor current is the current corresponding to the second inductor.

3. The method according to claim 2, characterized in that, The first selection switch, based on the grid voltage at the current cycle stage and the second output signal, determines a second control signal corresponding to each switch transistor at the current cycle stage, including: When the grid voltage is in the positive half-cycle phase of the current cycle, the first selection switch determines, based on the second output signal, that the second control signals corresponding to the first switch and the third switch are conduction signals, and determines that the second control signals corresponding to the second switch, the fourth switch, the fifth switch, and the sixth switch are deactivation signals; When the grid voltage is in the negative half-cycle of the current cycle, the first selection switch determines, based on the second output signal, that the second control signals corresponding to the fourth and sixth switches are turn-on signals, and determines that the second control signals corresponding to the first, second, third, and fifth switches are turn-off signals.

4. The method according to claim 1 or 2, characterized in that, After generating the second output signal, the method further includes: The integrator clears the current integration result to zero so that when a high-level clock signal is received again at the set input of the trigger, the integrator can start integrating again to obtain the second control signal corresponding to each switch.

5. The method according to claim 1 or 2, characterized in that, The photovoltaic grid-connected power generation system also includes a capacitor and a filter; the inverter also includes a first device and a second device; the two ends of the capacitor are connected to the two ends of the photovoltaic panel; the other end of the first switch, the other end of the fourth switch, one end of the third switch, and one end of the sixth switch are all connected to one end of the capacitor; one end of the fifth switch and one end of the second switch are all connected to the other end of the capacitor. One end of the second device is connected to the other end of the second inductor and the other end of the fifth switch. The other ends of the second device and the third switch are both connected to one end of the filter. One end of the first device is connected to the other end of the second switch and the other end of the first inductor. The other ends of the first device and the sixth switch are both connected to the other end of the filter. Both ends of the filter are connected to the power grid.

6. The method according to claim 1 or 2, characterized in that, The first selection switch includes multiple output terminals corresponding to the plurality of switching transistors, and each output terminal is connected to each corresponding switching transistor; The output terminal and the inverting output terminal of the trigger are both connected to the input terminal of the first selection switch; the reset input terminal of the trigger is connected to the output terminal of the comparator. The first input terminal of the comparator is connected to the output terminal of the second multiplier; the second input terminal of the comparator is connected to the output terminal of the integrator; the input terminal of the integrator is connected to the output terminal of the first multiplier. The input terminal of the first multiplier is connected to the second selection switch.

7. A control system for a photovoltaic grid-connected power generation system, characterized in that, The control system includes a maximum power point tracking unit, an arithmetic unit, a proportional-integral controller, a coordinate transformation unit, a first selection switch, a second selection switch, a first multiplier, a second multiplier, an integrator, a comparator, and a trigger. The trigger is used to generate a first output signal based on the high-level clock signal currently received at the set input terminal, wherein the output terminal of the trigger is at a high level and the inverting output terminal is at a low level in the first output signal; The first selection switch is used to determine, based on the grid voltage at the current cycle stage and the first output signal, a first control signal corresponding to each of the plurality of switching transistors at the current cycle stage. The plurality of switching transistors are multiple switching transistors in an inverter of a photovoltaic power generation system, and the plurality of switching transistors include a first switching transistor group and a second switching transistor group; the first switching transistor group includes a first switching transistor, a second switching transistor, and a third switching transistor; the second switching transistor group includes a fourth switching transistor, a fifth switching transistor, and a sixth switching transistor. When the voltage of the power grid is in the positive half-cycle of the current cycle, the first selection switch determines, based on the first output signal, that the first control signals corresponding to the first switch and the second switch are turn-on signals, and determines that the first control signals corresponding to the third switch, the fourth switch, the fifth switch, and the sixth switch are turn-off signals; When the voltage of the power grid is in the negative half-cycle of the current cycle, the first selection switch determines, based on the first output signal, that the first control signals corresponding to the fourth switch and the fifth switch are conduction signals, and determines that the first control signals corresponding to the first switch, the second switch, the third switch, and the sixth switch are deactivation signals; The maximum power point tracking unit is used to determine the reference operating voltage of the photovoltaic panel in the photovoltaic power generation system at the maximum power point; The arithmetic unit is used to calculate the difference between the reference operating voltage and the DC voltage output by the photovoltaic panel to obtain a first voltage; The proportional-integral controller is used to process the first voltage to obtain the first current; The coordinate transformation unit is used to perform coordinate transformation on the first current and the preset second current to obtain the grid-connected current reference value. The second selection switch is used to determine the inductor current based on the voltage of the grid in the photovoltaic power generation system at the current stage of the cycle, wherein the inductor current is one of multiple currents corresponding to multiple inductors in the inverter; The first multiplier is used to multiply the DC voltage output by the photovoltaic panel and the inductor current, and then input the product to the integrator. The second multiplier is used to multiply the grid-connected current reference value and the grid voltage. The comparator is used to compare the output of the second multiplier and the output of the integrator. When the output of the integrator is greater than or equal to the output of the second multiplier, a high-level input signal is generated at the reset input terminal of the flip-flop. The trigger is also used to generate a second output signal based on the high-level input signal of the reset input terminal, wherein the inverting output terminal of the trigger is high-level and the output terminal is low-level in the second output signal; The first selection switch is also used to determine, based on the voltage of the power grid in the current cycle phase and the second output signal, a second control signal corresponding to each switch tube in the current cycle phase.

8. The control system according to claim 7, characterized in that, After generating the second output signal, the integrator is also used to clear the current integration result so that when a high-level clock signal is received again at the set input of the trigger, the integrator can start integrating again to obtain the second control signal corresponding to each switch.

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