Photovoltaic power generation system and control method thereof

Abstract

The invention discloses a photovoltaic power generation system and a control method of the photovoltaic power generation system, which are used for realizing rapid frequency support. The photovoltaic power generation system comprises a direct current converter which is used for connecting the output of a photovoltaic module and performing voltage conversion on the direct current output by the photovoltaic module; the inverter is used for converting the direct current output by the direct current converter into alternating current and outputting the alternating current to a power grid; and the first controller is used for generating a first driving signal according to two of the first voltage of the direct current of the direct current converter, the active power output by the inverter and the operating parameters of the power grid, and controlling the operating state of the inverter according to the first driving signal.

Description

[0001] This application is a divisional application. The application number of the original application is 202211024308.0, and the original application date is August 24, 2022. The entire contents of the original application are incorporated into this application by reference. Technical Field

[0002] The present application relates to the photovoltaic field, and in particular to a photovoltaic power generation system and a control method for the photovoltaic power generation system. Background Art

[0003] As the new national energy security strategy of building a new power system with new energy as the main body is gradually promoted, the role of new energy power generation systems such as wind power and photovoltaics in the power grid will gradually change from supporting power sources to main power sources, and higher requirements are placed on new energy equipment. With the rapid increase in the penetration rate of photovoltaic installed capacity in the power grid, the ability of photovoltaic equipment to support the power grid will become an important part of the safety and stability of the power system. However, in current photovoltaic construction projects, photovoltaic equipment generally does not have the ability to actively support the frequency and voltage of the power grid, which can easily cause system instability problems in some high-penetration, large-scale photovoltaic transmission scenarios over long distances through long transmission lines. At the same time, when low-frequency or over-frequency events occur in the power grid, the new energy power system may be disconnected from the grid. Summary of the invention

[0004] The present application provides a photovoltaic power generation system and a control method for the photovoltaic power generation system, which can achieve rapid frequency support.

[0005] In a first aspect, an embodiment of the present application provides a photovoltaic power generation system, including a DC converter, an inverter and an inverter controller.

[0006] The DC converter is used to connect the output of the photovoltaic module to convert the DC power output by the photovoltaic module into voltage; the inverter is used to convert the DC power output by the DC converter into AC power and output it to the power grid; the first controller is used to generate a first drive signal according to two of the first voltage of the DC power output by the DC converter, the active power output by the inverter, and the operating parameters of the power grid, and control the operating state of the inverter according to the first drive signal. The first voltage is the voltage amplitude of the DC power output by the DC converter, and the operating parameters of the power grid include one or more of reactive current, active current, reactive power, active power, voltage amplitude, and power grid frequency.

[0007] In the photovoltaic power generation system provided in the embodiment of the present application, when the grid frequency changes, the amplitude of the first voltage will change, and the active power output by the inverter will also cause the grid frequency to change, that is, the above three parameters affect each other. Therefore, when the first controller detects that the grid deviates from its rated frequency during normal operation, it can use any two of the above three parameters to generate corresponding drive signals and adjust the operating state of the inverter, so that the AC power output by the inverter can achieve the frequency support function.

[0008] In a possible design, the first controller is specifically used to: generate a first active power control signal according to the first voltage difference and the first frequency difference; and generate a first drive signal according to the first active power control signal and the operating parameters of the power grid. The first voltage is the voltage amplitude of the direct current output by the direct current converter, and the operating parameters of the power grid include one or more of reactive current, active current, reactive power, active power, voltage amplitude, and power grid frequency.

[0009] By adopting the above-mentioned photovoltaic power generation system, droop control can be performed between the active power output by the inverter and the DC voltage according to the first voltage difference between the first voltage and the first reference voltage, and droop control can be performed between the active power output by the inverter and the grid frequency according to the frequency difference, and the above-mentioned two droop control strategies can be used to jointly determine the active power value used to achieve frequency support.

[0010] In one possible design, the first controller is specifically used to: generate a first modulation wave signal based on a first active power control signal and operating parameters of a power grid; generate a first drive signal based on the first modulation wave signal and a first carrier signal, wherein the first carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0011] By adopting the above photovoltaic power generation system, the first carrier signal is adjusted by the first modulation wave signal used to control the output power of the inverter to obtain the first drive signal used to control the conduction timing of the switch tube in the inverter, thereby adjusting the active power value output by the inverter.

[0012] In a possible design, the first controller is specifically used to: obtain a first power value using a first voltage difference and a first droop coefficient; the first droop coefficient is determined according to the correspondence between the DC power output by the DC converter and the active power output by the inverter; obtain a second power value using a first frequency difference and a second droop coefficient; the second droop coefficient is determined according to the correspondence between the grid frequency and the active power output by the inverter; generate a first active power control signal according to the first power value, the second power value and the third power value. The third power value is the initial value of the active power issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0013] With the photovoltaic power generation system, a suitable droop curve is selected based on the correspondence between the grid frequency and the active power output by the inverter and the correspondence between the DC voltage output by the DC converter and the active power output by the inverter, thereby improving the frequency support effect.

[0014] In a possible design, the first controller is specifically used to: generate a first voltage control signal according to a first power difference and a second frequency difference; and generate a first drive signal according to the first voltage control signal and an operating parameter of a power grid. The first power difference is the difference between the active power output by the inverter and the first reference power, the second frequency difference is the difference between the power grid frequency and the second reference frequency, the first reference power is the rated active power value output by the inverter when the power grid is operating normally, and the first reference frequency is the rated frequency value when the power grid is operating normally.

[0015] By adopting the above-mentioned photovoltaic power generation system, droop control can be performed between the active power output by the inverter and the DC side voltage according to the first power difference, and droop control can be performed between the grid frequency and the DC side voltage according to the second frequency difference. The above-mentioned two droop control strategies are used to jointly determine the DC voltage amplitude used to control the inverter drive signal, and by controlling the inverter drive signal, rapid frequency support can be achieved.

[0016] In one possible design, the first controller is specifically used to: generate a second modulation wave signal based on the first voltage control signal and the operating parameters of the power grid; generate a first drive signal based on the second modulation wave signal and the second carrier signal, wherein the second carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0017] By adopting the above photovoltaic power generation system, the second carrier signal is adjusted by the second modulation wave signal for controlling the output power of the inverter to obtain the first drive signal for controlling the conduction timing of the switch tube in the inverter, thereby adjusting the output parameters of the inverter.

[0018] In a possible design, the first controller is specifically used to obtain a first DC voltage value using a first power difference and a third droop coefficient; the third droop coefficient is determined based on the correspondence between the active power output by the DC converter and the DC power output by the DC converter; the second DC voltage value is obtained using a second frequency difference and a fourth droop coefficient; the fourth droop coefficient is determined based on the correspondence between the grid frequency and the DC power output by the DC converter; a first voltage control signal is generated based on the first DC voltage value, the second DC voltage value and the third DC voltage value, wherein the third DC voltage value is an initial value of the DC voltage issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0019] By adopting the above photovoltaic power generation system, a suitable droop curve is selected for the correspondence between the grid frequency and the first voltage output by the DC converter and the correspondence between the active power output by the inverter and the first voltage output by the DC converter, thereby improving the frequency support effect.

[0020] In a possible design, the first controller is specifically used to: generate a first frequency control signal according to the second power difference and the second voltage difference; generate a first drive signal according to the first frequency control signal and the operating parameters of the power grid. The second power difference is the difference between the active power output by the inverter and the second reference power, the second voltage difference is the difference between the first voltage and the second reference voltage, the second reference power is the rated active power value output by the inverter when the power grid is operating normally, and the second reference voltage is the rated voltage value output by the DC converter when the power grid is operating normally.

[0021] By adopting the above-mentioned photovoltaic power generation system, droop control can be performed between the grid frequency and the active power output by the inverter according to the second power difference, and droop control can be performed between the grid frequency and the first voltage output by the DC converter according to the second voltage difference. The above-mentioned two droop control strategies are used to jointly determine the frequency of the inverter output, and the frequency support effect is achieved by adjusting the frequency of the inverter output.

[0022] In one possible design, the first controller is specifically used to: generate a third modulation wave signal based on the first frequency control signal and the operating parameters of the power grid; generate a first drive signal based on the third modulation wave signal and the third carrier signal, wherein the third carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0023] By adopting the above photovoltaic power generation system, the third carrier signal is adjusted by the third modulation wave signal used to control the output power of the inverter to obtain the first drive signal used to control the conduction timing of the switch tube in the inverter, thereby adjusting the output parameters of the inverter.

[0024] In a possible design, the first controller is specifically used to: generate a first frequency value using the second power difference and the fifth droop coefficient, the fifth droop coefficient is determined according to the corresponding relationship between the active power output by the inverter and the grid frequency; generate a second frequency value using the second voltage difference and the sixth droop coefficient, the sixth droop coefficient is determined according to the corresponding relationship between the direct current output by the DC converter and the grid frequency; generate a first frequency control signal according to the first frequency value, the second frequency value and the third frequency value. Among them, the third frequency value is the initial frequency value issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0025] By adopting the photovoltaic power generation system, a suitable droop curve is selected for the correspondence between the grid frequency and the active power output by the inverter and the correspondence between the first voltage output by the DC converter and the grid frequency, thereby improving the frequency support effect.

[0026] In a possible design, the photovoltaic power generation system further includes a second controller connected to the DC converter, configured to generate a second drive signal according to the third voltage difference, and control the active power output by the DC converter according to the second drive signal. The third voltage difference is the difference between the third reference voltage and the first voltage, and the third reference voltage is the rated voltage output by the DC converter when the power grid is operating normally.

[0027] In the above photovoltaic power generation system, since the inverter is connected to the DC converter, that is, the active power output by the inverter is mainly provided by the DC converter, in order to realize that the inverter can output active power for realizing frequency support, the active power output by the DC converter can be adjusted by the DC controller, so that the output active power meets the frequency support requirements. In addition, since the second controller can directly determine the grid frequency through the first voltage, there is no need to obtain the grid frequency through a high-speed transmission line, which speeds up the frequency support speed of the photovoltaic power generation system.

[0028] In one possible design, the second controller is specifically used to: determine the working mode of the DC converter, the working modes including a unidirectional support mode and a bidirectional support mode; generate a third reference voltage according to the working mode of the DC converter and the operating parameters of the DC converter, the operating parameters of the DC converter including one or more of input current, input voltage and input power; obtain a fourth power value according to the third voltage difference and a seventh droop coefficient, the seventh droop coefficient is determined according to the correspondence between the output voltage of the DC converter and the active power output by the DC converter; determine a second active power control signal according to the fourth power value and the maximum power value; generate a second drive signal according to the second active power control signal and the input parameters of the DC converter.

[0029] When the above photovoltaic power generation system is used, when the grid frequency increases, the output voltage of the DC converter increases. Correspondingly, when the grid frequency decreases, the output voltage of the DC converter decreases. Therefore, the current grid situation can be determined by the second voltage difference between the voltage output by the DC converter and the reference voltage, and corresponding power adjustments can be made to achieve frequency support.

[0030] In a possible design, the second controller is further configured to calculate a maximum power value MPPE according to operating parameters of the DC converter.

[0031] With the above photovoltaic power generation system, the DC converter will operate in MPPT mode without frequency support and output the maximum power value. When grid frequency support is required, MPPE can be used to estimate the maximum power value and adjust the power based on the maximum power value.

[0032] In a possible design, the second controller is specifically used to: determine the additional reserved power value according to the working mode of the DC converter; and generate a third reference voltage according to the operating parameters of the DC converter and the additional reserved power value.

[0033] By adopting the photovoltaic power generation system, the output power of the DC converter can be determined according to the operating parameters of the DC converter and the set additional reserved power value, so as to dynamically adjust the reference voltage value.

[0034] In a second aspect, an embodiment of the present application provides a control method for a photovoltaic power generation system, which can be applied to a photovoltaic power generation system, and specifically includes the following steps: monitoring the operating parameters of a power grid, a first voltage output by an inverter, and an active power output by a DC converter; generating a first drive signal based on the first voltage, the active power output by the DC converter, and two of the operating parameters of the power grid, and controlling the operating state of the inverter based on the first drive signal, wherein the first voltage is the voltage amplitude of the direct current output by the DC converter, and the operating parameters of the power grid include one or more of reactive current, active current, reactive power, active power, voltage amplitude, and power grid frequency.

[0035] In one possible design, a first drive signal is generated based on two of the first voltage, the active power output by the inverter, and the operating parameters of the power grid, including: generating a first active power control signal based on a first voltage difference and a first frequency difference, wherein the first voltage difference is the difference between the first voltage and a first reference voltage, the first frequency difference is the difference between the power grid frequency and the first reference frequency, the first reference voltage is the rated voltage value output by the DC converter when the power grid operates normally, and the first reference frequency is the rated frequency value when the power grid operates normally; generating the first drive signal based on the first active power control signal and the operating parameters of the power grid.

[0036] In one possible design, a first drive signal is generated according to a first active power control signal and operating parameters of a power grid, including: generating a first modulation wave signal according to the first active power control signal and the operating parameters of the power grid; generating a first drive signal according to the first modulation wave signal and a first carrier signal, wherein the first carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0037] In a possible design, a first active power control signal is generated according to a first voltage difference and a first frequency difference, including: obtaining a first power value by using the first voltage difference and a first droop coefficient; the first droop coefficient is determined according to the correspondence between the DC voltage output by the DC converter and the active power output by the DC converter; obtaining a second power value by using the first frequency difference and a second droop coefficient; the second droop coefficient is determined according to the correspondence between the grid frequency and the active power output by the inverter; generating a first active power control signal according to the first power value, the second power value and the third power value, wherein the third power value is the initial value of the active power issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0038] In one possible design, a first drive signal is generated based on two of a first voltage, active power output by an inverter, and operating parameters of a power grid, including: generating a first voltage control signal based on a first power difference and a second frequency difference, wherein the first power difference is the difference between the active power output by the inverter and a first reference power, the second frequency difference is the difference between the power grid frequency and a second reference frequency, the first reference power is the rated active power value output by the inverter when the power grid operates normally, and the first reference frequency is the rated frequency value when the power grid operates normally; generating a first drive signal based on the first voltage control signal and the operating parameters of the power grid.

[0039] In one possible design, a first drive signal is generated according to a first voltage control signal and operating parameters of a power grid, including: generating a second modulation wave signal according to the first voltage control signal and the operating parameters of the power grid; generating the first drive signal according to the second modulation wave signal and a second carrier signal, wherein the second carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0040] In one possible design, a first voltage control signal is generated according to a first power difference and a second frequency difference, including: obtaining a first DC voltage value using the first power difference and a third droop coefficient; the third droop coefficient is determined based on the correspondence between the active power output by the DC converter and the DC power output by the DC converter; obtaining a second DC voltage value using the second frequency difference and a fourth droop coefficient; the fourth droop coefficient is determined based on the correspondence between the grid frequency and the DC power output by the DC converter; generating a first voltage control signal according to the first DC voltage value, the second DC voltage value and the third DC voltage value, wherein the third DC voltage value is an initial value of the DC voltage issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0041] In one possible design, a first drive signal is generated based on two of a first voltage, an active power output by an inverter, and an operating parameter of a power grid, including: generating a first frequency control signal based on a second power difference and a second voltage difference, wherein the second power difference is a difference between the active power output by the inverter and a second reference power, the second voltage difference is a difference between the first voltage and the second reference voltage, the second reference power is a rated active power value output by the inverter when the power grid operates normally, and the second reference voltage is a rated voltage value output by the DC converter when the power grid operates normally; generating a first drive signal based on the first frequency control signal and the operating parameters of the power grid.

[0042] In one possible design, a first drive signal is generated according to a first frequency control signal and operating parameters of a power grid, including: generating a third modulation wave signal according to the first frequency control signal and operating parameters of a power grid; generating the first drive signal according to the third modulation wave signal and a third carrier signal, wherein the third carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0043] In one possible design, a first frequency control signal is generated according to the second power difference and the second voltage difference, including: generating a first frequency value by using the second power difference and a fifth droop coefficient, the fifth droop coefficient being determined according to the correspondence between the active power output by the inverter and the grid frequency; generating a second frequency value by using the second voltage difference and a sixth droop coefficient, the sixth droop coefficient being determined according to the correspondence between the direct current output by the direct current converter and the grid frequency; generating a first frequency control signal according to the first frequency value, the second frequency value and the third frequency value, wherein the third frequency value is the initial frequency value issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0044] In one possible design, the method also includes: generating a second drive signal based on the difference between the first voltage and the third voltage, and controlling the active power output by the DC converter based on the second drive signal, wherein the third voltage difference is the difference between a third reference voltage and the first voltage, and the third reference voltage is the rated voltage output by the DC converter when the power grid operates normally.

[0045] In one possible design, a second drive signal is generated according to the difference between the first voltage and the third voltage, including: determining an operating mode of the DC converter, the operating mode including a unidirectional support mode and a bidirectional support mode; generating a third reference voltage according to the operating mode of the DC converter and the operating parameters of the DC converter, the operating parameters of the DC converter including one or more of an input current and an input power; obtaining a fourth power value according to the third voltage difference and a seventh droop coefficient, the seventh droop coefficient being determined according to the correspondence between the output voltage of the DC converter and the active power output by the DC converter; determining a second active power control signal according to the fourth power value and the maximum power value MPPE; and generating a second drive signal according to the second active power control signal and the input parameters of the DC converter.

[0046] In one possible design, a second drive signal is generated according to a second active power control signal and input parameters of a DC converter, including: generating a fourth modulation wave signal according to the second active power control signal and the input parameters of the DC converter; generating a second drive signal according to the fourth modulation wave signal and a fourth carrier signal, wherein the fourth carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0047] In one possible design, the method further includes: determining the MPPE based on operating parameters of the DC converter.

[0048] In one possible design, a third reference voltage is generated according to an operating mode of the DC converter and operating parameters of the DC converter, including: determining an additional reserved power value according to the operating mode of the DC converter; and generating the third reference voltage according to the operating parameters of the DC converter and the additional reserved power value.

[0049] The technical effects that can be achieved in the above-mentioned second aspect can refer to the description of the beneficial effects in the above-mentioned first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of a photovoltaic power generation system provided in an embodiment of the present application Figure 1 ;

[0051] Figure 2 A schematic diagram of a photovoltaic power generation system provided in an embodiment of the present application Figure 2 ;

[0052] Figure 3 A schematic diagram of the corresponding relationship between the active power output by an inverter and the DC voltage provided in an embodiment of the present application;

[0053] Figure 4 A schematic diagram of the corresponding relationship between the active power output by an inverter and the grid frequency provided in an embodiment of the present application;

[0054] Figure 5 A schematic diagram of the corresponding relationship between a DC voltage and a grid frequency provided in an embodiment of the present application;

[0055] Figure 6 A schematic diagram of a photovoltaic power generation system provided in an embodiment of the present application Figure 3 ;

[0056] Figure 7 A schematic diagram of the corresponding relationship between the active power output by a DC converter and the DC voltage provided in an embodiment of the present application Figure 1 ;

[0057] Figure 8 The output waveform of a photovoltaic power generation system provided in the embodiment of the present application is shown as follows: Figure 1 ;

[0058] Fig. 9 The output waveform of a photovoltaic power generation system provided in the embodiment of the present application is shown as follows: Figure 2 ;

[0059] Fig.10 A schematic diagram of the corresponding relationship between the active power output by a DC converter and the DC voltage provided in an embodiment of the present application Figure 2 ;

[0060] Fig.11 The output waveform of a photovoltaic power generation system provided in the embodiment of the present application is shown as follows: Figure 3 ;

[0061] Fig.12 The output waveform of a photovoltaic power generation system provided in the embodiment of the present application is shown as follows: Figure 4 ;

[0062] Fig.13 A schematic diagram of a control method for a photovoltaic power generation system provided in an embodiment of the present application Figure 1 ;

[0063] Fig.14 A schematic diagram of a control method for a photovoltaic power generation system provided in an embodiment of the present application Figure 2 ;

[0064] Fig.15 A schematic diagram of a control method for a photovoltaic power generation system provided in an embodiment of the present application Figure 3 ;

[0065] Fig.16 A schematic diagram of a control method for a photovoltaic power generation system provided in an embodiment of the present application Figure 4 ;

[0066] Fig.17A schematic diagram of a control method for a photovoltaic power generation system provided in an embodiment of the present application Figure 5 . DETAILED DESCRIPTION

[0067] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. The terms used in the implementation mode of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0068] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims.

[0069] Below, some terms in the embodiments of the present application are explained to facilitate understanding by those skilled in the art.

[0070] (1) In the embodiments of the present application, the term "plurality" refers to two or more than two, and other quantifiers are similar.

[0071] (2) The switch tube in the embodiment of the present application may be one or more of various types of switch tubes such as relays, metal oxide semiconductor field effect transistors (MOSFET), bipolar junction transistors (BJT), insulated gate bipolar transistors (IGBT), silicon carbide (SiC) transistors, etc., which are not listed one by one in the embodiment of the present application. The packaging form of each switch tube may be a single tube package or a multi-tube package, which is not limited in the embodiment of the present application. Each switch tube may include a first end, a second end and a control end, wherein the control end is used to control the on or off of the switch tube. When the switch tube is on, current can be transmitted between the first end and the second end of the switch tube, and when the switch tube is off, current cannot be transmitted between the first end and the second end of the switch tube. Taking MOSFET as an example, the control end of the switch tube is the gate, the first end of the switch tube may be the source, the second end may be the drain, or the first end may be the drain, and the second end may be the source.

[0072] (3) In the embodiments of the present application, "connection" can be understood as electrical connection, and the connection between two electrical components can be a direct or indirect connection between the two electrical components. For example, the connection between A and B can be either a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, the connection between A and B can also be a direct connection between A and C, and C and B can be directly connected, and A and B are connected through C. The "connection" in the embodiments of the present application can also be understood as a wireless connection, that is, the connection between two electrical components can be an electromagnetic connection between the two electrical components.

[0073] (4) Active power-frequency droop control: Active power-frequency droop control can be constructed by using the approximate linear relationship between active power and the frequency of the power grid. When the power grid cannot meet the load demand and the frequency of the power grid fluctuates, the inverter output can be controlled to control the active power of the power grid frequency to restore to normal.

[0074] (5) Voltage-active power droop control: establish an approximate linear relationship between the DC voltage on the inverter input side and the active power output by the inverter, and use this approximate linear relationship to construct voltage-active power droop control. Through voltage-active power droop control, when the grid fails to meet the load demand and causes the grid frequency to fluctuate, the inverter output can be controlled to control the grid frequency to restore normal active power.

[0075] (6) Voltage-frequency droop control: establish an approximate linear relationship between the DC voltage and the frequency of the power grid, and use this approximate linear relationship to construct voltage-frequency droop control. Through DC voltage-frequency droop control, when the power grid cannot meet the load demand and the frequency of the power grid fluctuates, the DC converter can be controlled to output the active power required to restore the power grid frequency.

[0076] (7) Maximum power point tracking (MPPT) mode: The controller of the DC converter can track the maximum power point of the PV module, which can significantly increase the output power of the PV array and thus improve the energy utilization rate of the PV system.

[0077] (8) Maximum power point estimation (MPPE) mode: the DC converter controller can estimate the maximum power point of the PV panel.

[0078] The solution disclosed in this application can be applied to new energy systems and to grid-connected scenarios of new energy systems, wherein the new energy systems may include but are not limited to: photovoltaic power generation systems, wind power generation systems, hydropower generation systems, etc.

[0079] In a specific application scenario, the new energy system may be a photovoltaic power generation system. Figure 1 The schematic diagram of the structure of a photovoltaic power generation system is shown as an example. Figure 1 As shown, the photovoltaic power generation system mainly includes a DC converter, an inverter and a controller. The photovoltaic power generation system is connected to the photovoltaic module and outputs the electric energy output by the photovoltaic module to the power grid.

[0080] In a possible implementation, a photovoltaic power generation system includes a photovoltaic module.

[0081] During the process of photovoltaic power generation system grid connection, photovoltaic modules can convert light energy into direct current; the DC converter is connected to the output end of the photovoltaic module, can receive the DC output of the photovoltaic module, and perform voltage conversion on the received DC; the inverter can receive the DC output of the DC converter after voltage conversion, and convert the received DC into AC, and output it to the grid through the grid connection point, so as to realize the grid connection of the photovoltaic power generation system; the controller is connected to the inverter, and is used to control the inverter to convert the received DC into AC. Among them, the DC converter is generally connected to the inverter through the DC bus, that is, the voltage amplitude of the DC output by the DC converter is the DC bus voltage.

[0082] In actual use, the inverter is composed of multiple switching devices. The controller controls the conduction state of multiple switching devices in the inverter by sending drive signals to multiple switches in the inverter, thereby controlling the operation of the inverter.

[0083] Continue to see Figure 1 As shown, the controller is connected to the power station management system at the upper layer of the photovoltaic power generation system, and adjusts the operating state of the inverter when receiving the control command sent by the power station management system. Specifically, the power station management system can obtain the operating parameters of the power grid regularly or in real time, and monitor the operating state of the power grid. When the power grid fails or the connected load changes significantly, causing the frequency of the power grid to change, the power station management system can calculate the active power value required for frequency support according to the operating conditions of the power grid, and send a dispatching instruction to the controller. After receiving the above dispatching instruction, the controller adjusts the active power value output by the inverter by adjusting the driving signal of the switch tube in the inverter, thereby realizing the frequency support function of the power grid.

[0084] In actual use, the frequency support function of the controller is realized through the dispatching instructions issued by the upper-level power station management system. The controller is coordinated and controlled by the power station management system. When the frequency of the power grid fluctuates, the response speed is slow.

[0085] In view of this, the embodiment of the present application provides a photovoltaic power generation system and a control method of the photovoltaic power generation system for quickly achieving frequency support. In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings.

[0086] Figure 2 A schematic diagram of the structure of a photovoltaic power generation system provided in an embodiment of the present application. Figure 2 As shown, the photovoltaic power generation system 20 includes a DC converter 21, an inverter 22 and a first controller 23. The input end of the DC converter 21 is connected to the output end of the photovoltaic module 24, the output end of the DC converter 21 is connected to the inverter 22; and the inverter 22 is connected to the first controller 23.

[0087] In one example, the photovoltaic power generation system 20 may further include a photovoltaic component 24 .

[0088] See also Figure 2As shown, during the process of the photovoltaic power generation system 20 being connected to the grid, the photovoltaic module 24 can convert light energy into direct current and output the direct current to the direct current converter 21; the direct current converter 21 can convert the direct current output by the photovoltaic module 24 into voltage and output the direct current after voltage conversion; the inverter 22 can convert the direct current output by the direct current converter 21 into alternating current and output it to the grid, thereby realizing the connection of the photovoltaic power generation system to the grid; the first controller 23 is connected to the inverter 22, and can control the inverter 22 to convert the received direct current into alternating current. Among them, the direct current converter 21 and the inverter 22 are connected through a direct current bus.

[0089] In actual use, the DC converter 21 is connected to the inverter 22 via a DC bus, and the voltage of the AC power output by the DC converter 21 is the DC bus voltage.

[0090] Specifically, the first controller 23 can generate a first drive signal based on the first voltage of the direct current output by the DC converter 21, the active power output by the inverter 22, and two of the operating parameters of the power grid, and control the operating state of the inverter 22 according to the first drive signal, so that the alternating current output by the inverter 22 can achieve a frequency support function.

[0091] See also Figure 2 As shown, during the grid-connected process of the photovoltaic power generation system 20, when the grid frequency changes, the amplitude of the first voltage will change, and the active power output by the inverter 22 will also cause the grid frequency to change, that is, the above three parameters affect each other. Therefore, when the first controller detects that the grid deviates from its rated frequency during normal operation, it can use any two of the above three parameters to generate an adjustment value of another parameter, and by generating a corresponding drive signal, the inverter 22 outputs alternating current for achieving frequency support, thereby realizing the frequency support function of the photovoltaic power generation system.

[0092] The operating parameters of the power grid may include one or more of the following: reactive current, active current, active power, reactive power, voltage amplitude and power grid frequency.

[0093] It should be understood that in the photovoltaic power generation system 20 provided in the embodiment of the present application, frequency support calculation can be performed by the first controller 23 local to the photovoltaic power generation system 20. Compared with the frequency support calculation performed by the upper-level power station management system in the prior art, the acquisition time of the grid frequency and related parameters and the issuance time of the dispatching instructions are reduced, thereby achieving rapid frequency support and allowing the grid to quickly recover to a stable state.

[0094] In addition, the photovoltaic power generation system 20 provided in the embodiment of the present application will involve the first voltage that characterizes the output of the photovoltaic power generation system 20 in the frequency support calculation, taking into account the power generation of the photovoltaic power generation system 20. Without affecting the operation of the power grid, the active power value output by the photovoltaic power generation system 20 can be appropriately increased, thereby increasing the proportion of new energy in the power grid.

[0095] In actual use, the inverter 22 may be composed of components such as switch tubes, diodes, inductors, capacitors, etc. The working state of the inverter 22 may be achieved by adjusting the working states of these components (such as switch tubes).

[0096] Specifically, if the switch tube in the inverter 22 is a MOS tube, the first controller 23 can be connected to the gate of the MOS tube to adjust the operation of the inverter 22 by controlling the on-off of the MOS tube; if the switch tube in the inverter 22 is a BJT, the first controller 23 can be connected to the base of the BJT to adjust the operation of the inverter 22 by controlling the on-off of the BJT.

[0097] The process of the first controller 23 implementing frequency support by using different parameters is described below in conjunction with the embodiments.

[0098] Embodiment 1

[0099] In actual use, the first controller 23 generates a first driving signal according to the first voltage output by the DC converter 21 and the grid frequency.

[0100] Specifically, the first controller 23 can calculate the first voltage difference between the first voltage and the first reference voltage, and calculate the first frequency difference between the grid frequency and the first reference frequency; generate a first active power control signal according to the first voltage difference and the first frequency difference; generate a first drive signal according to the first active power control signal and the current grid operation parameters. The DC converter 21 outputs a rated voltage value when the first reference voltage grid is operating normally. The first reference frequency is the rated frequency value when the grid is operating normally.

[0101] In actual use, when the grid frequency is higher than the first reference frequency, it indicates that the active power currently transmitted on the grid is higher than the active power actually required by the grid. When the grid frequency is lower than the first reference frequency, it indicates that the active power currently transmitted on the grid is lower than the active power actually required by the grid. According to the correspondence between the grid frequency and the active power output by the inverter, an active-frequency droop control strategy is established. Similarly, when the first voltage output by the DC converter 21 is higher than the first reference voltage, it indicates that the power output by the DC converter 21 exceeds the rated power value when the grid is in normal operation. When the inverter sends the power to the grid, the power transmitted on the grid will exceed the power actually required by the grid. When the first voltage output by the DC converter 21 is lower than the first reference power, it indicates that the power output by the DC converter 21 exceeds the rated power when the grid is in normal operation. When the inverter sends the power to the grid, the power transmitted on the grid will be less than the power actually required by the grid. Based on the correspondence between the active power output by the inverter and the DC bus voltage, a voltage-active droop control strategy is established. The active power value required for frequency support is calculated through the above two droop control strategies.

[0102] In actual use, the first controller 23 uses the first voltage difference and the first droop coefficient to form a voltage-active power droop control strategy to obtain a first power value; the first controller 23 uses the first frequency difference and the second droop coefficient to obtain a second power value, wherein the second droop coefficient is determined according to the correspondence between the grid frequency and the active power output by the inverter; the first power value, the second power value and the third power value obtained by the above two droop control strategies are used to generate the first active power control signal required for frequency support. Among them, the first droop coefficient is determined according to the correspondence between the direct current output by the DC converter and the active power output by the inverter. Similarly, the third power value is the initial value of the active power issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system 20.

[0103] In one example, the first controller 23 can be connected to a DC sensor and an AC sensor respectively, the DC sensor is used to detect the first voltage output by the DC converter 21, and the AC sensor can detect the operating parameters of the power grid. The AC detection unit can be, but is not limited to, a voltage sensor and a current sensor. For example, a Hall sensor.

[0104] In actual use, after the first controller 23 obtains the value detected by the above sensor, the following formula can be used to calculate the first active power control signal P for power support: INV :

[0105]

[0106] Among them, K upFirst droop coefficient, K pf is the second droop coefficient, U bus is the first voltage, is the first reference voltage, f req is the frequency of the power grid, is the first reference frequency, P cmd is the initial value of active power sent by the upper power station management system. Among them, the first droop coefficient K up and the second droop coefficient K pf It can be, but is not limited to, a constant, an exponent, and a power.

[0107] In specific implementation, the first droop coefficient is set according to the corresponding relationship curve between the DC bus voltage and the active power output by the inverter 22, and the second droop coefficient is set according to the corresponding relationship curve between the active power output by the inverter and the grid frequency. The above values ​​can be configured by a proportional controller, an integrator, other combinations or user selection.

[0108] See also Figure 2 As shown, the first controller 23 generates a first active power control signal using the above formula 1, and generates a first modulation wave signal using the first active power control signal and the operating parameters of the current power grid. The first modulation wave signal is compared with the first carrier signal to generate a first drive signal, and is sent to the switch tube in the inverter 22. The switch tube in the inverter 22 adjusts its conduction timing under the control of the above first drive signal, thereby adjusting the active power value output by the inverter 22 to achieve a frequency support function. Among them, the first carrier signal can be a sine wave signal or a pulse signal with a fixed period.

[0109] It can be seen from the above formula 1 that the active power output by the inverter 22 can be dynamically adjusted by utilizing the dynamic change of the DC bus voltage and the dynamic change of the grid frequency.

[0110] Specifically, the first controller 23 uses the voltage-active power droop control strategy and the active power-frequency droop control strategy to jointly adjust the active power output by the inverter 22. Referring to Formula 1, when the grid frequency remains unchanged, since the DC converter 21 operates in the MPPT mode, as the DC bus voltage gradually increases within the range of [Ubusmin, Ubusmax], it means that when the power generation of the photovoltaic power generation system 20 gradually increases, the active power value output by the inverter 22 can be controlled to increase monotonically without affecting the operation of the grid. The corresponding relationship between the active power output by the inverter 22 and the DC voltage can be seen in Figure 3 The DC bus voltage range is the operating range of the DC bus when the DC converter 21 works normally, and is determined by the operating voltage of the DC converter 21 and the AC voltage amplitude at the output side of the inverter.

[0111] In one example, when the active power output by the inverter 22 increases, the frequency on the grid will increase, and other devices on the grid can reduce the amount of electricity transmitted to the grid, thereby achieving coordinated control with other devices on the grid.

[0112] Specifically, the first controller 23 uses the voltage-active power droop control strategy and the active power-frequency droop control strategy to jointly adjust the active power output by the inverter 22. Referring to Formula 1, when the DC bus voltage remains unchanged, as the grid frequency gradually increases in the range of [freqmin, freqmax], it means that the active power transmitted on the current grid is gradually increasing and exceeds the active power actually required by the grid. The active power output by the inverter 22 can be controlled to decrease monotonically. The corresponding relationship between the active power output by the inverter 22 and the grid frequency can be seen in Figure 4 The above-mentioned power grid frequency range is the fluctuation range when the power grid is working normally.

[0113] Combination Figure 3 and Figure 4 , and the content of formula 1 shows that, when the active power output by the inverter 22 is fixed, the corresponding relationship between the DC bus voltage and the grid frequency can be seen in Figure 5 shown.

[0114] Embodiment 2

[0115] In actual use, the first controller 23 generates a first driving signal according to the active power output by the inverter 22 and the grid frequency.

[0116] Specifically, the first controller 23 can generate a first voltage control signal according to the first power difference and the second frequency difference, and generate a first drive signal according to the first voltage control signal and the operation parameters of the power grid. The first power difference is the difference between the active power output by the inverter 22 and the first reference power, the second frequency difference is the difference between the power grid frequency and the second reference frequency, the first reference power is the rated active power value output by the inverter 22 when the power grid is operating normally, and the first reference frequency is the rated frequency value when the power grid is operating normally.

[0117] In actual use, when the grid frequency is higher than the second reference frequency, it indicates that the active power currently transmitted on the grid is higher than the active power actually required by the grid. When the grid frequency is lower than the second reference frequency, it indicates that the active power currently transmitted on the grid is lower than the active power actually required by the grid. According to the correspondence between the grid frequency and the active power, an active-frequency droop control strategy is established. Similarly, when the grid frequency is higher than the second reference frequency, the DC bus voltage rises, and when the grid frequency is lower than the first reference frequency, the DC bus voltage drops. Based on the correspondence between the grid frequency and the DC bus voltage, a voltage-frequency droop control strategy is established. The first voltage for frequency support is calculated by the above two droop control strategies.

[0118] Specifically, the first controller 23 obtains the first DC voltage value using the first power difference and the third droop coefficient; the third droop coefficient is determined according to the corresponding relationship between the active power output by the DC converter 21 and the DC power output by the DC converter 21; the second DC voltage value is obtained using the second frequency difference and the fourth droop coefficient; the fourth droop coefficient is determined according to the corresponding relationship between the grid frequency and the DC power output by the DC converter; and the first voltage control signal is generated according to the first DC voltage value, the second DC voltage value and the third DC voltage value. Among them, the third DC voltage value is the initial value of the DC voltage issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0119] It should be understood that the inverter 22 can operate in the MPPT mode. When the inverter 22 can control the output power of the DC converter by adjusting the output voltage of the DC converter, when the input voltage of the inverter 22 changes, the voltage output to the grid will also change, thereby achieving frequency support.

[0120] In one example, the first controller 23 may be connected to a first sensor and a second sensor respectively, the first sensor is used to detect the operating parameters of the power grid, and the second sensor is used to detect the active power output by the inverter 22. The first sensor and the second sensor are both AC sensors, such as Hall sensors.

[0121] Specifically, the first controller 23 dynamically adjusts the DC voltage on the inverter side by utilizing the dynamic change of the grid frequency and the dynamic change of the active power output by the inverter 22. Specifically, the first controller 23 calculates the first voltage control signal for frequency support using the following formula:

[0122]

[0123] in, is the first voltage control signal generated, is the initial value of the DC voltage issued by the power station management system, Dup is the third droop coefficient, Duf is the fourth droop coefficient, P INVRef is the power command value, P INV Output active power for the inverter. req is the frequency of the power grid, is the reference frequency.

[0124] The third droop coefficient is determined according to the corresponding relationship between the active power output by the DC converter 21 and the DC power output by the DC converter, and the fourth droop coefficient is determined according to the corresponding relationship between the grid frequency and the DC power output by the DC converter 21.

[0125] Specifically, the third droop coefficient is set according to the corresponding relationship curve between the DC bus voltage and the active power output by the inverter 22, and the fourth droop coefficient is set according to the corresponding relationship curve between the first voltage output by the DC converter 21 and the grid frequency. The above values ​​can be configured by a proportional controller, an integrator, other combinations or user selection.

[0126] See also Figure 2 As shown, the first controller 23 generates a first voltage control signal for realizing frequency support using the above formula 2, and generates a second modulation wave signal using the first voltage control signal and the operating parameters of the current power grid. The second modulation wave signal is compared with the second carrier signal to generate a first drive signal, and is sent to the switch tube in the inverter 22. The switch tube in the inverter 22 adjusts its conduction timing under the control of the above second drive signal, thereby adjusting the active power value output by the inverter 22 to realize the frequency support function. Among them, the second carrier signal can be a sine wave signal or a pulse signal with a fixed period.

[0127] It can be seen from the above formula 2 that the DC voltage output by the DC converter 21 can be dynamically adjusted by utilizing the dynamic change of the grid frequency and the dynamic transformation of the active power output by the inverter.

[0128] Specifically, the first controller 23 uses the voltage-active power droop control strategy and the voltage-frequency droop control strategy to jointly adjust the DC voltage received by the inverter 22. Referring to Formula 2, it can be seen that when the active power output by the inverter 22 remains unchanged, as the grid frequency gradually increases in the range of [freqmin, freqmax], it means that the active power transmitted on the current grid is gradually increasing and exceeds the active power actually required by the grid. The amplitude of the output current of the DC converter 21 can be controlled to reduce the active power output by the inverter 22. When the grid frequency remains unchanged, as the active power output by the inverter 22 gradually increases, it means that when the power generation of the photovoltaic power generation system 20 gradually increases, the active power value output by the inverter 22 can be controlled to decrease monotonically without affecting the operation of the grid.

[0129] Embodiment 3

[0130] In actual application, the first controller 23 can generate a first driving signal by using the first voltage of the direct current output by the direct current converter 21 and the active power output by the inverter 22 .

[0131] Specifically, the first controller 23 generates a first frequency control signal according to the second power difference and the second voltage difference; and generates a first drive signal according to the first frequency control signal and the operating parameters of the power grid. The second power difference is the difference between the active power output by the inverter and the second reference power, the second voltage difference is the difference between the first voltage and the second reference voltage, the second reference power is the rated active power value output by the inverter when the power grid is operating normally, and the second reference voltage is the rated voltage value output by the DC converter when the power grid is operating normally.

[0132] In actual use, when the active power output by the inverter 22 is higher than the second reference power, it indicates that the active power output by the inverter 22 is higher than the active power actually required by the power grid, which will cause the power grid frequency to rise. When the active power output by the inverter 22 is lower than the second reference power, it indicates that the active power output by the inverter 22 is lower than the active power actually required by the power grid, which will cause the power grid frequency to drop. Based on the correspondence between the active power output by the inverter 22 and the power grid frequency, an active-frequency droop control strategy is established. Similarly, when the first voltage output by the DC converter 21 is higher than the second reference voltage, it indicates that the power transmitted on the power grid exceeds the power actually required by the power grid, and the power grid frequency rises. When the first voltage output by the DC converter 21 is lower than the second reference voltage, it indicates that the power transmitted on the power grid is lower than the power actually required by the power grid, and the power grid frequency drops. Based on the correspondence between the first voltage output by the DC converter 21 and the power grid frequency, a voltage-frequency droop control strategy is established, and the frequency used for frequency support is calculated by the above two droop control strategies.

[0133] Specifically, the first controller 23 obtains a first DC voltage value using the first power difference and the third droop coefficient; the third droop coefficient is determined according to the correspondence between the active power output by the DC converter and the DC power output by the DC converter; the second DC voltage value is obtained using the second frequency difference and the fourth droop coefficient; the fourth droop coefficient is determined according to the correspondence between the grid frequency and the DC power output by the DC converter; and the first voltage control signal is generated according to the first DC voltage value, the second DC voltage value and the third DC voltage value. Among them, the third DC voltage value is the initial value of the DC voltage issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0134] Specifically, the first controller 23 may be connected to a DC sensor and an AC sensor respectively, the DC sensor is used to detect the first voltage output by the DC converter 21 , and the AC sensor is used to detect the active power output by the inverter 22 .

[0135] In actual use, the first controller 23 dynamically adjusts the frequency of the AC power output by the inverter 22 by using the dynamic change of the active power output by the inverter 22 and the dynamic change of the first voltage output by the DC converter 21. Specifically, the first controller 23 calculates the first frequency control signal for frequency support using the following formula:

[0136]

[0137] in, is the first frequency control signal generated, is the initial frequency value issued by the power station management system. Rfp is the fifth droop coefficient, Rfu is the sixth droop coefficient, P INVRef is the second reference power, P INV Output active power for the inverter. bus is the first voltage, is the second reference DC voltage.

[0138] Specifically, the fifth droop coefficient is determined according to the corresponding relationship between the active power output by the inverter and the grid frequency, and the sixth droop coefficient is determined according to the corresponding relationship between the DC power output by the DC converter and the grid frequency. The above values ​​can be configured by a proportional controller, an integrator, other combinations or user selection.

[0139] See also Figure 2As shown, the first controller 23 generates a first frequency control signal for realizing frequency support using the above formula three, and generates a third modulation wave signal using the first frequency control signal and the operating parameters of the current power grid. The third modulation wave signal is compared with the third carrier signal to generate a first drive signal, and is sent to the switch tube in the inverter 22. The switch tube in the inverter 22 adjusts its conduction timing under the control of the above second drive signal, thereby adjusting the active power value output by the inverter 22 to realize the frequency support function. Among them, the third carrier signal can be a sine wave signal or a pulse signal with a fixed period.

[0140] It can be seen from the above formula 3 that the frequency of the alternating current output by the inverter can be dynamically changed by utilizing the dynamic change of the first voltage output by the DC converter and the dynamic change of the active power output by the inverter.

[0141] Specifically, the first controller 23 uses the active-frequency droop control strategy and the voltage-frequency droop control strategy to jointly adjust the DC voltage received by the inverter 22. Referring to Formula 3, it can be seen that when the active power output by the inverter 22 remains unchanged, since the DC converter 21 operates in the MPPT mode, as the DC bus voltage gradually increases within the range of [Ubusmin, Ubusmax], it means that when the power generation of the photovoltaic power generation system 20 gradually increases, the active power value output by the inverter 22 can be controlled to increase monotonically without affecting the operation of the power grid. When the first voltage output by the DC converter remains unchanged, as the active power output by the inverter gradually increases, it means that the active power currently transmitted on the power grid exceeds the active power actually required by the power grid. Without affecting the operation of the power grid, the active power value output by the inverter 22 can be controlled to decrease monotonically.

[0142] In actual use, the above formula 1 can be used to control the active power output by the inverter alone, and the above formulas 2 and 3 can also be used to control the DC voltage and frequency to achieve composite control.

[0143] See also Figure 2 and Figure 3 As shown, the inverter 22 is connected to the DC converter 24, and the active power output by the inverter 22 is mainly obtained from the DC converter 21. In order to enable the inverter 22 to quickly output the active power required for frequency support, the photovoltaic power generation system 20 provided in the embodiment of the present application may also include a second controller, see Figure 6 As shown, the second controller 25 can be connected to the DC converter 21, can generate a second drive signal according to a third voltage difference between the third reference voltage and the first voltage, and control the active power output by the DC converter 21 according to the second drive signal. The third reference voltage is the rated voltage output by the DC converter 21 when the power grid is operating normally.

[0144] As before, when the frequency of the power grid increases, the DC bus voltage will increase, and when the frequency of the power grid decreases, the DC bus voltage will decrease. Based on the relationship between the frequency and the DC bus voltage, the second controller 25 can determine the frequency of the current power grid by detecting the DC bus voltage, thereby outputting active power for frequency support to the inverter 22.

[0145] It should be understood that the second controller 25 can adjust the active power directly by detecting the current DC bus voltage through the corresponding relationship between the grid frequency and the DC bus voltage, so that there is no need to use a high-speed transmission line to obtain the frequency condition on the grid side, which can solve the problem that the frequency support of the DC converter 21 is limited by the frequency sampling performance and high-speed communication performance. At the same time, the DC converter 21 can control the power generation of the inverter photovoltaic power generation system by controlling the DC bus voltage, so that the inverter can control the amount of active power output to the grid according to the power generation condition, and inform other devices connected to the grid through the change of the grid frequency.

[0146] In specific implementation, the second controller is specifically used to: determine the working mode of the DC converter, the working modes include a unidirectional support mode and a bidirectional support mode; generate a third reference voltage according to the working mode of the DC converter and the operating parameters of the DC converter, the operating parameters of the DC converter include one or more of input current, input voltage and input power; obtain a fourth power value according to the third voltage difference and the seventh droop coefficient, the seventh droop coefficient is determined according to the correspondence between the output voltage of the DC converter and the active power output by the DC converter; determine a second active power control signal according to the fourth power value and the maximum power value MPPE; generate a second drive signal according to the second active power control signal and the input parameters of the DC converter.

[0147] In one example, the second controller may further include a DC detection unit for detecting a DC bus voltage, obtaining a first voltage, and outputting the first voltage to the second droop calculation unit.

[0148] In another example, the second controller 25 is connected to a DC sensor, a signal input end of the DC sensor is connected to an output end of a DC converter, a signal output end of the DC sensor is connected to the second controller 25, and the second controller 25 obtains the first voltage through the DC sensor.

[0149] After receiving the first voltage and the reference voltage generated by the mode selection unit, the second droop calculation unit calculates the second active power control signal for realizing frequency support by using the following formula:

[0150]

[0151] Among them, P BSTis the generated second active power control signal, P MPPE is the estimated maximum power value, D PV is the seventh droop coefficient. PV It can be, but is not limited to, a constant, an exponent, and a power.

[0152] It can be seen from Formula 4 that when the illumination condition of the photovoltaic assembly 24 is fixed and the maximum power value is fixed, the active power output by the DC converter 21 is determined by the reference voltage.

[0153] Specifically, the second controller 25 can determine the third reference voltage using the following formula:

[0154]

[0155] Among them, U BstBusRef is the set value, dU(P,U bus , △P) is the dynamic voltage adjustment value, P is the maximum power value output by the inverter, and △P is the set additional reserved power value. The dynamic voltage adjustment value can be obtained by a proportional controller, an integrator or other combinations.

[0156] It should be understood that when the lighting conditions of the photovoltaic component 24 change, the photoelectric conversion efficiency of the photovoltaic component 24 changes. In order to achieve the maximum power generation of the photovoltaic power generation system, the DC converter 24 connected to the photovoltaic component 24 operates in MPPT mode by dynamically adjusting its voltage value.

[0157] In actual use, when the DC converter 21 works in the unidirectional support mode, ΔP is zero. When the DC converter 21 works in the bidirectional support mode, ΔP is less than the maximum power value and greater than zero. For example, ΔP can be 10% of the maximum power value, and other values ​​can also be selected, for example, 15% of the maximum power value. The purpose of setting ΔP is to control the DC converter to reduce power operation and realize bidirectional support for the grid frequency.

[0158] Referring to Formula 5, it can be seen that when the above-mentioned mode selection unit determines that the DC converter operates in the unidirectional support mode, the bus reference voltage of the DC converter is mainly determined by the dynamic voltage point, that is, the DC converter 21 has a unidirectional support capability for rapid power reduction, but does not have the support capability for rapid power increase. However, when the power grid operates normally, the DC converter can be able to operate in the MPPT mode to ensure the power generation of the photovoltaic power generation system.

[0159] See also Figure 7As shown, the DC converter 21 achieves the maximum power Pmppt1 output at the O1 operating point and has the ability to quickly support unidirectional power. When the light on the photovoltaic module 24 increases, the output power of the MPPT unit increases. According to Formula 4 and Formula 5, the MPPT unit will move the dynamic point of the DC converter 21 to the maximum power point O2, that is, the mode selection module updates the reference value of the DC voltage droop. When the light on the photovoltaic module 24 decreases, according to the calculation of formula 2 and formula 3, the working voltage of the DC converter will drop to the maximum power point O3, realizing the MPPT mode operation and having the ability to quickly support unidirectional power.

[0160] Refer to Formula 1 to Formula 5. If the DC converter works in the unidirectional support mode, when the system detects that the grid frequency rises and the grid frequency drops, the fluctuation of the active power output by the DC converter and the active power output by the inverter can be seen in Figure 8 and Fig. 9 shown.

[0161] Referring to Formula 5, it can be seen that when the above-mentioned mode selection unit determines that the DC converter works in the bidirectional support mode, the bus reference voltage of the DC converter is not only determined by the dynamic point, but also uses △P to reduce the additional reserved power value, thereby reducing the reference voltage of the DC bus, and realizing that the DC converter works in the power reserve mode, that is, when working normally, the DC converter reduces the power output. Therefore, when the grid frequency decreases or increases, the output power can be quickly increased or decreased to achieve bidirectional support capability. Among them, the corresponding relationship between the active power output of the DC converter and the DC bus voltage can be seen in Fig.10 shown.

[0162] Refer to Formula 1 to Formula 5. If the DC converter works in the bidirectional support mode, when the system detects that the grid frequency rises and the grid frequency drops, the fluctuation of the active power output by the DC converter and the active power output by the inverter can be seen in Fig.11 and Fig.12 shown.

[0163] The selection of the working mode of the DC converter can be set according to the user's selection, or can be set by receiving a selection instruction sent by an upper layer. Of course, other methods can also be used for setting, for example, the DC converter is set with a default working mode, and when the photovoltaic power generation system is connected to the grid, the default working mode can be used to control the operation of the DC converter.

[0164] Optionally, the present application is applicable to the grid-connected architecture of other new energy systems, such as wind power generation systems and hydropower generation systems. The above new energy systems are all equipped with grid-connected inverters for connecting the generated electricity to the grid. They are also applicable to large-scale energy storage application scenarios, small and medium-sized distributed energy storage application scenarios, etc. This is just an example, and the present application does not limit specific application scenarios. Optionally, the present application is also applicable to off-grid scenarios of new energy systems.

[0165] Based on the above photovoltaic power generation system embodiment, the present application embodiment also provides a control method for a photovoltaic power generation system, which is applied to the photovoltaic power generation system. The method can be executed by a controller in the photovoltaic power generation system. Specifically, the controller in the photovoltaic power generation system includes a first controller connected to an inverter. Fig.13 As shown, the method provided in the embodiment of the present application specifically includes the following steps:

[0166] Step 1301: Monitor the operation parameters of the power grid, the first voltage of the DC power output by the DC converter, and the active power output by the inverter. The first voltage is the voltage amplitude of the DC power output by the DC converter, and the operation parameters of the power grid include one or more of reactive current, active current, reactive power, active power, voltage amplitude, and power grid frequency.

[0167] In a specific implementation, corresponding AC sensors or DC sensors, such as voltage sensors and current sensors, may be used to obtain the operation parameters of the power grid, the first voltage, and the active power output by the inverter.

[0168] Step 1302: Generate a first drive signal according to two of the first voltage, the active power output by the inverter, and the operating parameters of the power grid, and control the operating state of the inverter according to the first drive signal.

[0169] In a possible implementation, a first drive signal is generated based on two of the first voltage, the active power output by the inverter, and the operating parameters of the power grid, including: generating a first active power control signal based on a first voltage difference and a first frequency difference, wherein the first voltage difference is the difference between the first voltage and a first reference voltage, the first frequency difference is the difference between the power grid frequency and the first reference frequency, the first reference voltage is the rated voltage value output by the DC converter when the power grid operates normally, and the first reference frequency is the rated frequency value when the power grid operates normally; generating the first drive signal based on the first active power control signal and the operating parameters of the power grid.

[0170] In one possible implementation, a first drive signal is generated according to a first active power control signal and operating parameters of a power grid, including: generating a first modulation wave signal according to the first active power control signal and the operating parameters of the power grid; generating a first drive signal according to the first modulation wave signal and a first carrier signal, wherein the first carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0171] In a possible implementation, a first active power control signal is generated according to a first voltage difference and a first frequency difference, including: obtaining a first power value using the first voltage difference and a first droop coefficient; the first droop coefficient is determined according to the correspondence between the DC voltage output by the DC converter and the active power output by the DC converter; obtaining a second power value using the first frequency difference and a second droop coefficient; the second droop coefficient is determined according to the correspondence between the grid frequency and the active power output by the inverter; generating a first active power control signal according to the first power value, the second power value and the third power value, wherein the third power value is the initial value of the active power issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0172] In a possible implementation, a first drive signal is generated based on two of a first voltage, an active power output by an inverter, and an operating parameter of a power grid, including: generating a first voltage control signal based on a first power difference and a second frequency difference, wherein the first power difference is a difference between the active power output by the inverter and a first reference power, the second frequency difference is a difference between a power grid frequency and a second reference frequency, the first reference power is a rated active power value output by the inverter when the power grid operates normally, and the first reference frequency is a rated frequency value when the power grid operates normally; generating a first drive signal based on the first voltage control signal and the operating parameters of the power grid.

[0173] In one possible implementation, a first drive signal is generated according to a first voltage control signal and operating parameters of a power grid, including: generating a second modulation wave signal according to the first voltage control signal and the operating parameters of the power grid; generating the first drive signal according to the second modulation wave signal and a second carrier signal, wherein the second carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0174] In a possible implementation, a first voltage control signal is generated according to a first power difference and a second frequency difference, including: obtaining a first DC voltage value using the first power difference and a third droop coefficient; the third droop coefficient is determined based on the correspondence between the active power output by the DC converter and the DC power output by the DC converter; obtaining a second DC voltage value using the second frequency difference and a fourth droop coefficient; the fourth droop coefficient is determined based on the correspondence between the grid frequency and the DC power output by the DC converter; generating a first voltage control signal according to the first DC voltage value, the second DC voltage value and the third DC voltage value, wherein the third DC voltage value is an initial value of the DC voltage issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0175] In a possible implementation, a first drive signal is generated based on two of a first voltage, an active power output by an inverter, and an operating parameter of a power grid, including: generating a first frequency control signal based on a second power difference and a second voltage difference, wherein the second power difference is a difference between the active power output by the inverter and a second reference power, the second voltage difference is a difference between the first voltage and the second reference voltage, the second reference power is a rated active power value output by the inverter when the power grid operates normally, and the second reference voltage is a rated voltage value output by the DC converter when the power grid operates normally; generating a first drive signal based on the first frequency control signal and the operating parameters of the power grid.

[0176] In one possible implementation, a first drive signal is generated according to a first frequency control signal and operating parameters of a power grid, including: generating a third modulation wave signal according to the first frequency control signal and the operating parameters of the power grid; generating the first drive signal according to the third modulation wave signal and a third carrier signal, wherein the third carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0177] In a possible implementation, a first frequency control signal is generated according to the second power difference and the second voltage difference, including: generating a first frequency value by using the second power difference and a fifth droop coefficient, the fifth droop coefficient being determined according to the correspondence between the active power output by the inverter and the grid frequency; generating a second frequency value by using the second voltage difference and a sixth droop coefficient, the sixth droop coefficient being determined according to the correspondence between the direct current output by the direct current converter and the grid frequency; generating a first frequency control signal according to the first frequency value, the second frequency value and the third frequency value, wherein the third frequency value is the initial frequency value issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

[0178] In a possible implementation, the method also includes: generating a second drive signal based on the difference between the first voltage and the third voltage, and controlling the active power output by the DC converter based on the second drive signal, wherein the third voltage difference is the difference between the third reference voltage and the first voltage, and the third reference voltage is the rated voltage output by the DC converter when the power grid operates normally.

[0179] In one possible implementation, a second drive signal is generated based on the difference between the first voltage and the third voltage, including: determining an operating mode of the DC converter, the operating modes including a unidirectional support mode and a bidirectional support mode; generating a third reference voltage based on the operating mode of the DC converter and the operating parameters of the DC converter, the operating parameters of the DC converter including one or more of an input current and an input power; obtaining a fourth power value based on the third voltage difference and a seventh droop coefficient, the seventh droop coefficient being determined based on the correspondence between the output voltage of the DC converter and the active power output by the DC converter; determining a second active power control signal based on the fourth power value and the maximum power value MPPE; and generating a second drive signal based on the second active power control signal and the input parameters of the DC converter.

[0180] In one possible implementation, a second drive signal is generated according to a second active power control signal and input parameters of a DC converter, including: generating a fourth modulation wave signal according to the second active power control signal and the input parameters of the DC converter; generating a second drive signal according to the fourth modulation wave signal and a fourth carrier signal, wherein the fourth carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

[0181] In a possible implementation manner, the method further includes: determining the MPPE according to operating parameters of the DC converter.

[0182] In a possible implementation, generating a third reference voltage according to an operating mode of the DC converter and operating parameters of the DC converter includes: determining an additional reserved power value according to the operating mode of the DC converter; and generating the third reference voltage according to the operating parameters of the DC converter and the additional reserved power value.

[0183] Combined with the above description, such as Fig.14 FIG. 1 is a flow chart of the first controller generating the first driving signal according to the first voltage and the grid frequency, see Fig.14 As shown, the first controller performs the following steps:

[0184] Step 1401: monitor the operation parameters and the first voltage of the power grid, wherein the operation parameters of the power grid may include one or more of active power, reactive power, active current, reactive current, power grid voltage and power grid frequency.

[0185] Step 1402: Calculate a first voltage difference between a first voltage and a first reference voltage, and a first frequency difference between a grid frequency and a first reference frequency.

[0186] Step 1403: Generate a first active power control signal using the first voltage difference and the first frequency difference.

[0187] Step 1404: Generate a first drive signal according to the first active power control signal and an operating parameter of the power grid.

[0188] Step 1405: Output the first driving signal to the inverter.

[0189] like Fig.15 FIG. 1 is a flow chart of the first controller generating the first driving signal according to the active power output by the inverter and the grid frequency, see Fig.15 As shown, the first controller performs the following steps:

[0190] Step 1501: monitor the operating parameters of the power grid and the active power output by the inverter, wherein the operating parameters of the power grid may include one or more of active power, reactive power, active current, reactive current, power grid voltage and power grid frequency.

[0191] Step 1502: Calculate a first power difference between the active power output by the inverter and a first reference power, and a second frequency difference between the grid frequency and a second reference frequency.

[0192] Step 1503: Generate a first voltage control signal using the first power difference and the second frequency difference.

[0193] Step 1504: Generate a first drive signal according to the first voltage control signal and an operating parameter of the power grid.

[0194] Step 1505: Output the first drive signal to the inverter.

[0195] like Fig.16 FIG. 1 is a flow chart of a first controller generating a first driving signal according to the active power output by the inverter and the first voltage output by the DC converter, see Fig.16 As shown, the first controller performs the following steps:

[0196] Step 1601: monitor a first voltage output by a DC converter and an active power output by an inverter.

[0197] Step 1602: Calculate a second voltage difference between the first voltage and the second reference voltage, and a second power difference between the active power output by the inverter and the second reference power.

[0198] Step 1603: Generate a first frequency control signal using the second power difference and the second voltage difference.

[0199] Step 1604: Generate a first drive signal according to the first frequency control signal and an operating parameter of the power grid.

[0200] Step 1605: Output the first drive signal to the inverter.

[0201] In actual use, the active power output by the inverter is provided by the DC converter. In order to achieve frequency support, the DC side also needs to control the output power. The inverter controller generates a second drive signal based on the second voltage difference between the reference voltage and the DC bus voltage, and controls the active power output by the DC converter according to the second drive signal.

[0202] Specifically, the inverter controller can obtain a fourth power value based on the second voltage difference and the third droop coefficient, where the third droop coefficient is determined based on the correspondence between the output voltage of the DC converter and the active power output by the DC converter; determine the second active power value based on the fourth power value and the maximum power value; and generate a second drive signal based on the second active power control signal and the input parameters of the DC converter.

[0203] Furthermore, the controller in the photovoltaic power generation system also includes a second controller connected to the DC converter, see Fig.17 As shown, the method provided in the embodiment of the present application also includes the following steps:

[0204] Step 1701: Monitor a first voltage.

[0205] Step 1702: Determine a reference voltage according to the operating mode of the DC converter.

[0206] Step 1703: Calculate a third voltage difference between the third reference voltage and the first voltage.

[0207] Step 1704: Generate a second active power control signal using the third voltage difference and the maximum power value.

[0208] Step 1705: Generate a second driving signal according to the second active power control signal and the input parameter of the DC converter.

[0209] Step 1706: Send the second driving signal to the DC converter.

[0210] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on the computer, the process or function according to the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (digital subscriber line, DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) mode to another website site, computer, server or data center. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server, data center, etc. that includes one or more available media integrated. The available medium can be a magnetic medium, (e.g., a floppy disk, a hard disk, a tape), or a semiconductor medium (e.g., a solid state drive (solid statedisk, SSD)), etc.

[0211] The present application also provides a readable storage medium for storing the method or algorithm provided in the above embodiment, for example, a random access memory (RAM), a flash memory, a read only memory (ROM), an EPROM memory, an electronic programmable ROM (EPROM), a register, a hard disk, a removable disk or any other form of storage medium in the art.

[0212] The steps of the method or algorithm described in the embodiment of the present application can be directly embedded in the control device. The control device may include a RAM memory, a flash memory, a ROM memory, an EPROM memory, a register, a hard disk, a removable disk or other storage media of any form in the art for storing the steps of the method or algorithm provided in the embodiment of the present application. Exemplarily, the storage medium can be connected to the processing module or the processor (or controller) in the control device so that the processing module, the processor (or controller) can read information from the storage medium, and can write information to the storage medium. Optionally, the storage medium can also be integrated into the processing module, the processor (or controller).

[0213] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0214] Although the present application has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the scope of the present application. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present application as defined by the appended claims, and are deemed to have covered any and all modifications, variations, combinations or equivalents within the scope of the present application.

[0215] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the scope of protection of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A photovoltaic power generation system, characterized in that: include: A DC converter, used to connect to the output of the photovoltaic module and convert the DC power output by the photovoltaic module into a voltage; An inverter, used to convert the direct current output by the direct current converter into alternating current and output it to a power grid; The first controller is used Generate a first active power control signal according to a first voltage difference and a first frequency difference, wherein the first voltage difference is a difference between a first voltage and a first reference voltage, the first frequency difference is a difference between the grid frequency and a first reference frequency, the first reference voltage is a rated voltage value output by the DC converter when the grid is operating normally, and the first reference frequency is a rated frequency value when the grid is operating normally; The first drive signal is generated according to the first active power control signal and the operating parameters of the power grid, and the operating state of the inverter is controlled according to the first drive signal, wherein the first voltage is the voltage amplitude of the direct current output by the direct current converter, and the operating parameters of the power grid include one or more of reactive current, active current, reactive power, active power, voltage amplitude and power grid frequency.

2. The system according to claim 1, characterized in that The first controller is specifically used for: generating a first modulation wave signal according to the first active power control signal and the operating parameters of the power grid; The first drive signal is generated according to the first modulation wave signal and the first carrier signal, wherein the first carrier signal is a sinusoidal wave signal or a pulse signal with a fixed period.

3. The system according to claim 1 or 2, characterized in that: The first controller is specifically used for: A first power value is obtained by using the first voltage difference and a first droop coefficient; the first droop coefficient is determined according to a corresponding relationship between the direct current output by the direct current converter and the active power output by the inverter; A second power value is obtained by using the first frequency difference and a second droop coefficient; the second droop coefficient is determined according to a corresponding relationship between the grid frequency and the active power output by the inverter; The first active power control signal is generated according to the first power value, the second power value and the third power value, wherein the third power value is an initial value of active power issued by a power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system, or the first controller is specifically used to: Generate a first voltage control signal according to a first power difference and a second frequency difference, wherein the first power difference is a difference between the active power output by the inverter and a first reference power, the second frequency difference is a difference between the grid frequency and a second reference frequency, the first reference power is a rated active power value output by the inverter when the grid operates normally, and the first reference frequency is a rated frequency value when the grid operates normally; The first drive signal is generated according to the first voltage control signal and an operating parameter of the power grid.

4. The system according to claim 3, characterized in that The first controller is specifically used for: generating a second modulation wave signal according to the first voltage control signal and the operating parameters of the power grid; The first drive signal is generated according to the second modulation wave signal and the second carrier signal, wherein the second carrier signal is a sine wave signal or a pulse signal with a fixed period, or The first controller is specifically used for: A first DC voltage value is obtained by using the first power difference and a third droop coefficient; the third droop coefficient is determined according to a corresponding relationship between the active power output by the DC converter and the DC power output by the DC converter; A second DC voltage value is obtained by using the second frequency difference and the fourth droop coefficient; the fourth droop coefficient is determined according to the corresponding relationship between the grid frequency and the DC power output by the DC converter; The first voltage control signal is generated according to the first DC voltage value, the second DC voltage value and the third DC voltage value, wherein the third DC voltage value is an initial DC voltage value issued by a power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

5. The system according to claim 1, wherein: The first controller is specifically used for: Generate a first frequency control signal according to a second power difference and a second voltage difference, wherein the second power difference is a difference between the active power output by the inverter and a second reference power, the second voltage difference is a difference between the first voltage and a second reference voltage, the second reference power is a rated active power value output by the inverter when the power grid is operating normally, and the second reference voltage is a rated voltage value output by the DC converter when the power grid is operating normally; generating the first drive signal according to the first frequency control signal and the operating parameters of the power grid, The first controller is also used for: generating a third modulation wave signal according to the first frequency control signal and the operating parameters of the power grid; The first drive signal is generated according to the third modulation wave signal and the third carrier signal, wherein the third carrier signal is a sine wave signal or a pulse signal with a fixed period, or The first controller is specifically used for: Generate a first frequency value by using the second power difference and a fifth droop coefficient, wherein the fifth droop coefficient is determined according to a corresponding relationship between the active power output by the inverter and the grid frequency; generating a second frequency value by using the second voltage difference and a sixth droop coefficient, wherein the sixth droop coefficient is determined according to a corresponding relationship between the direct current output by the direct current converter and the grid frequency; The first frequency control signal is generated according to the first frequency value, the second frequency value and the third frequency value, wherein the third frequency value is an initial frequency value issued by a power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

6. The system according to any one of claims 1 to 5, characterized in that: The photovoltaic power generation system further includes a second controller connected to the DC converter, which is used to generate a second drive signal according to a difference between the first voltage and a third voltage, and control the active power output by the DC converter according to the second drive signal, wherein the third voltage difference is a difference between a third reference voltage and the first voltage, and the third reference voltage is a rated voltage output by the DC converter when the power grid is operating normally. The second controller is specifically used for: Determining an operating mode of the DC converter, wherein the operating mode includes a unidirectional support mode and a bidirectional support mode; generating the third reference voltage according to the working mode of the DC converter and the operating parameters of the DC converter, wherein the operating parameters of the DC converter include one or more of input current, input voltage and input power; Obtaining a fourth power value according to the third voltage difference and a seventh droop coefficient, wherein the seventh droop coefficient is determined according to a corresponding relationship between an output voltage of the DC converter and an active power output by the DC converter; Determining the second active power control signal according to the fourth power value and the maximum power value MPPE; The second drive signal is generated according to the second active power control signal and an input parameter of the DC converter.

7. The system according to claim 6, characterized in that The second controller is specifically used for: generating a fourth modulation wave signal according to the second active power control signal and an input parameter of the DC converter; The second drive signal is generated according to the fourth modulation wave signal and the fourth carrier signal, wherein the fourth carrier signal is a sine wave signal or a pulse signal with a fixed period, The second controller is further configured to calculate the MPPE according to operating parameters of the DC converter.

8. The system according to claim 6 or 7, characterized in that The DC controller is specifically used for: Determining an additional reserved power value according to the working mode of the DC converter; The third reference voltage is generated according to the operating parameters of the DC converter and the additional reserved power value.

9. A control method for a photovoltaic power generation system, characterized in that: Applied in photovoltaic power generation systems, including: Monitoring the operating parameters of the power grid, the first voltage of the direct current output by the direct current converter, and the active power output by the inverter; The generating a first driving signal according to two of the first voltage, the active power output by the inverter, and the operating parameter of the power grid includes: Generate a first active power control signal according to a first voltage difference and a first frequency difference, wherein the first voltage difference is a difference between a first voltage and a first reference voltage, the first frequency difference is a difference between the grid frequency and a first reference frequency, the first reference voltage is a rated voltage value output by the DC converter when the grid is operating normally, and the first reference frequency is a rated frequency value when the grid is operating normally; The first drive signal is generated according to the first active power control signal and the operating parameters of the power grid, and the operating state of the inverter is controlled according to the first drive signal, wherein the first voltage is the voltage amplitude of the direct current output by the inverter, and the operating parameters of the power grid include one or more of reactive current, active current, reactive power, active power, voltage amplitude and power grid frequency.

10. The method according to claim 9, characterized in that The step of generating the first drive signal according to the first active power control signal and the operating parameters of the power grid includes: generating a first modulation wave signal according to the first active power control signal and the operating parameters of the power grid; Generate the first drive signal according to the first modulation wave signal and the first carrier signal, wherein the first carrier signal is a sine wave signal or a pulse signal with a fixed period; The step of generating a first active power control signal and a first driving signal according to the first voltage difference and the first frequency difference comprises: A first power value is obtained by using the first voltage difference and a first droop coefficient; the first droop coefficient is determined according to a corresponding relationship between a DC voltage output by a DC converter and an active power output by the DC converter; A second power value is obtained by using the first frequency difference and a second droop coefficient; the second droop coefficient is determined according to a corresponding relationship between the grid frequency and the active power output by the inverter; The first active power control signal is generated according to the first power value, the second power value and the third power value, wherein the third power value is the initial value of active power issued by the power station management system, and the power station management system is used to control the operating state of the photovoltaic power generation system.

Images