Voltage control method and power generation system

Abstract

The application provides a voltage control method, which is executed by a controller. The voltage control method comprises the following steps: detecting an output power of a DC converter. When the output power value of the DC converter is lower than or equal to a preset power threshold, controlling the DC conversion circuit to charge an output capacitor. When an electrical connection between the DC converter and an inverter is turned on, controlling the DC conversion circuit to stop charging the output capacitor, and adjusting an output voltage reference value of the DC converter according to a current output voltage of the DC converter, so as to control the output voltage of the DC converter according to the output voltage reference value. The application also provides a power generation system. Thus, the voltage control method provided by the application can timely adjust the output voltage of the DC converter according to the input voltage of the inverter, reduce signal delay caused by communication delay between the inverter and the DC converter, and ensure high voltage ride-through performance of the power generation system.

Description

Technical Field

[0001] This application relates to the field of power technology, and in particular to a voltage control method and a power generation system. Background Technology

[0002] With the development of new energy power generation technologies, photovoltaic / wind power generation systems have been more widely used. A photovoltaic / wind power generation system typically includes a DC / DC converter and a DC / AC converter. The output of the DC / DC converter is connected to the input of the DC / AC converter, and the output of the DC / AC converter is connected to the power grid. When the grid voltage increases, the input voltage of the DC / AC converter increases synchronously. However, due to the communication delay between the DC / DC converter and the DC / AC converter, the DC / DC converter cannot receive the change in input voltage from the DC / AC converter in a timely manner. Consequently, the output voltage of the DC / DC converter cannot be adjusted in a timely manner according to the input voltage of the DC / AC converter, affecting the high voltage ride-through (HVRT) performance of the photovoltaic / wind power generation system. Summary of the Invention

[0003] In view of the above problems, this application provides a voltage control method and a power generation system, which enables the output voltage of the DC converter to be adjusted in a timely manner according to the input voltage of the inverter, reducing signal delay caused by communication delay between the inverter and the DC converter, and ensuring the high voltage ride-through performance of the power generation system.

[0004] In a first aspect, this application provides a voltage control method applied to a power generation system. The power generation system includes a DC-DC converter, an inverter, and a controller. The DC-DC converter includes a DC-DC conversion circuit and an output capacitor. The input terminal of the DC-DC conversion circuit is used to connect to a DC source. The first output terminal of the DC-DC conversion circuit is used to connect to the first input terminal of the inverter and the first terminal of the output capacitor. The second output terminal of the DC-DC conversion circuit is used to connect to the second input terminal of the inverter and the second terminal of the output capacitor. The output terminal of the inverter is used to connect to the power grid. The voltage control method is executed by the controller. The voltage control method includes: detecting the output power of the DC-DC converter; when the output power value of the DC-DC converter decreases to less than or equal to a preset power threshold, controlling the DC-DC conversion circuit to charge the output capacitor; when the electrical connection between the DC-DC converter and the inverter is established, controlling the DC-DC conversion circuit to stop charging the output capacitor, and adjusting the output voltage reference value of the DC-DC converter according to the current output voltage of the DC-DC converter, so as to control the output voltage of the DC-DC converter according to the output voltage reference value. The voltage control method provided in this application enables the output voltage of the DC-DC converter to be adjusted in a timely manner according to the input voltage of the inverter, reducing signal delay caused by communication delay between the inverter and the DC-DC converter, and ensuring the high voltage ride-through performance of the power generation system.

[0005] In conjunction with the first aspect, in some possible implementations, when the electrical connection between the DC-DC converter and the inverter is established, controlling the DC-DC converter circuit to stop charging the output capacitor includes: acquiring the rate of change of the output voltage of the DC-DC converter. When the rate of change decreases to less than or equal to a preset rate, controlling the DC-DC converter circuit to stop charging the output capacitor. This application controls the DC-DC converter circuit to stop charging the output capacitor by detecting that the rate of change of the output voltage of the DC-DC converter decreases to less than or equal to a preset rate, thereby allowing the output power of the DC-DC converter to be transferred to the inverter, thus enabling the inverter to continuously and stably output active power to the grid during high-voltage ride-through.

[0006] In conjunction with the first aspect, in some possible implementations, the voltage control method further includes: receiving a control signal and updating the output voltage reference value according to the control signal. The control signal is generated by the inverter and is used to indicate the output voltage reference value. By receiving the control signal transmitted by the inverter and updating the previous output voltage reference value according to the output voltage reference value indicated by the control signal, this application can more accurately match the voltage conditions of the power grid and improve the high-voltage ride-through performance of the power generation system.

[0007] In conjunction with the first aspect, in some possible implementations, the voltage control method further includes: receiving a control signal and adjusting the output voltage of the DC-DC converter according to the control signal; and real-time detection of the output power of the DC-DC converter. The control signal is generated by the inverter based on the grid voltage and is used to indicate the output voltage of the DC-DC converter. This application, by detecting the output power of the DC-DC converter in real time, can reduce the impact of communication delays between the inverter and the DC-DC converter, thereby allowing direct detection of the DC-DC converter's output power without waiting for the control signal transmitted by the inverter. This ensures that the power generation system continuously and stably outputs active power during high-voltage ride-through.

[0008] In conjunction with the first aspect, in some possible implementations, controlling the DC-DC converter circuit to charge the output capacitor includes controlling the DC-DC converter circuit to charge the output capacitor in a constant current or constant power manner. This application, by charging the output capacitor in a constant current or constant power manner, can rapidly increase the output voltage of the DC-DC converter, thereby enabling the electrical connection between the DC-DC converter and the inverter to be established, allowing the inverter to quickly and stably output active power to the grid during high-voltage ride-through.

[0009] Secondly, this application provides a power generation system including a DC-DC converter, an inverter, and a controller. The DC-DC converter includes a DC-DC conversion circuit and an output capacitor. The input terminal of the DC-DC conversion circuit is connected to a DC source. The first output terminal of the DC-DC conversion circuit is connected to the first input terminal of the inverter and the first terminal of the output capacitor. The second output terminal of the DC-DC conversion circuit is connected to the second input terminal of the inverter and the second terminal of the output capacitor. The output terminal of the inverter is connected to the power grid. The controller is used to: detect the output power of the DC-DC converter; when the output power value of the DC-DC converter drops to less than or equal to a preset power threshold, control the DC-DC conversion circuit to charge the output capacitor; when the electrical connection between the DC-DC converter and the inverter is established, control the DC-DC conversion circuit to stop charging the output capacitor, and adjust the output voltage reference value of the DC-DC converter according to the current output voltage of the DC-DC converter, so as to control the output voltage of the DC-DC converter according to the output voltage reference value.

[0010] In conjunction with the second aspect, in some possible implementations, the DC controller is also used to: acquire the rate of change of the output voltage of the DC converter; and control the DC converter circuit to stop charging the output capacitor when the rate of change decreases to less than or equal to a preset rate.

[0011] In conjunction with the second aspect, in some possible implementations, the DC controller is also used to: receive control signals and update the output voltage reference value based on the control signals. The control signals are generated by the inverter and are used to indicate the output voltage reference value.

[0012] In conjunction with the second aspect, in some possible implementations, the DC controller is also used to: receive control signals and adjust the output voltage of the DC-DC converter according to the control signals; and detect the output power of the DC-DC converter when the grid voltage exceeds a voltage threshold. The control signals are generated by the inverter based on the grid voltage and are used to indicate the output voltage of the DC-DC converter.

[0013] In conjunction with the second aspect, in some possible implementations, the power generation system also includes a switching element. The first terminal of the switching element is electrically connected to the first output terminal of the DC-DC converter, and the second terminal is electrically connected to the first input terminal of the inverter. When the voltage difference between the second terminal and the first terminal of the switching element exceeds a preset value, the switching element is disconnected, and the controller controls the DC-DC converter circuit to charge the output capacitor. By incorporating this switching element, this application enables decoupling of the faulty inverter from the others in applications where multiple inverters are connected in parallel, preventing fault propagation and improving the reliability of the power generation system.

[0014] In conjunction with the second aspect, in some possible implementations, when the switching element is turned on, the controller controls the DC-DC converter circuit to stop charging the output capacitor.

[0015] In conjunction with the second aspect, in some possible implementations, the switching element is a diode.

[0016] In conjunction with the second aspect, in some possible implementations, the DC source is a photovoltaic module, and the power generation system constitutes a photovoltaic power generation system.

[0017] Furthermore, the technical effects of any possible implementation in the second aspect can be found in the technical effects of different implementations in the first aspect, and will not be repeated here. Attached Figure Description

[0018] Figure 1 A structural diagram of the power generation system provided in this application.

[0019] Figure 2 Another structural schematic diagram of the power generation system provided in this application.

[0020] Figure 3 This is another structural schematic diagram of the power generation system provided in this application.

[0021] Figure 4 This is another structural schematic diagram of the power generation system provided in this application.

[0022] Figure 5 A flowchart of the voltage control method provided in this application.

[0023] Figure 6The signal timing diagram of the DC-DC converter provided in this application. Detailed Implementation

[0024] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0025] It is understood that the connection relationships described in this application refer to direct or indirect connections. For example, the connection between A and B can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components. For example, A can be directly connected to C, and C can be directly connected to B, thus achieving a connection between A and B through C. It is also understood that the "A connects to B" described in this application can be a direct connection between A and B, or an indirect connection between A and B through one or more other electrical components.

[0026] In the description of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists alone, A and B exist simultaneously, and B exists alone.

[0027] In the description of this application, the words "first," "second," etc., are used only to distinguish different objects and do not limit the quantity or order of execution, nor do they imply that they must be different. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0028] The technical solution of this application will be further described in detail below with reference to the accompanying drawings.

[0029] With the development of new energy power generation technologies, photovoltaic (PV) / wind power generation systems have been more widely used. PV / wind power generation systems typically include DC / DC converters and DC / AC converters, with the output of the DC / DC converter connected to the input of the DC / AC converter. When the PV / wind power generation system is a grid-connected inverter system, the output power of the PV / wind power generation system is fed into the grid, meaning the output of the DC / AC converter is also connected to the grid. When the grid voltage rises, the PV / wind power generation system needs to ensure its High Voltage Ride-Through (HVRT) performance. HVRT refers to the ability of the PV / wind power generation system to maintain continuous operation without disconnecting from the grid within a certain voltage rise range and time interval. In other words, the PV / wind power generation system needs to rapidly and stably output active power to the grid within a certain voltage rise range and time interval to cope with the increased grid voltage. Active power refers to the actual AC energy generated or consumed by the PV / wind power generation system per unit time, i.e., the average power within the AC cycle. If a rapid and stable output of active power to the grid is required, the output power or output voltage of the DC / DC converter needs to be adjusted. However, when the grid voltage rises, the input voltage of the DC / AC converter also needs to rise to prevent the DC / AC converter from disconnecting from the grid. Due to the communication delay between the DC / DC converter and the DC / AC converter, the DC / DC converter cannot receive the change information of the DC / AC converter's input voltage in a timely manner. Consequently, the output voltage of the DC / DC converter cannot be adjusted in a timely manner according to the input voltage of the DC / AC converter, affecting the high-voltage ride-through performance of the photovoltaic / wind power generation system.

[0030] Therefore, this application provides a voltage control method and a power generation system, which enables the output voltage of the DC / DC converter to be adjusted in a timely manner according to the input voltage of the DC / AC converter, thereby ensuring the high voltage ride-through performance of the photovoltaic / wind power generation system.

[0031] Please see Figure 1 , Figure 1 This is a structural diagram of a power generation system 100 provided in this application. The power generation system 100 includes a DC source 11, a DC converter 12, a diode D1, an inverter 13, and a controller 15. The DC converter 12 is a DC / DC converter, and the inverter 13 is a DC / AC converter. The DC converter 12 includes a DC conversion circuit 121 and a capacitor C1, and the inverter 13 includes an inverter circuit 131 and a capacitor C2. The controller 15 includes a DC controller 122 and an inverter controller 132.

[0032] The output terminal of DC source 11 is electrically connected to the input terminal of DC converter 12. DC source 11 is used to provide DC power to power DC converter 12.

[0033] It is understood that the electrical energy supplied by the DC source 11 to the DC converter 12 can be converted from other energy sources, and this application does not impose any restrictions on the source of electrical energy for the DC source 11. The type of power generation system 100 can be determined by the type of DC source 11. For example, when the power generation system 100 is a photovoltaic power generation system, the DC source 11 is a photovoltaic (PV) module or photovoltaic string, used to receive solar energy and convert it into electrical energy to output DC power to the DC converter 12. The photovoltaic module is a DC power supply composed of solar cells connected in series or parallel, and the photovoltaic string is a DC power supply composed of multiple photovoltaic modules connected in series through positive and negative terminals. In other embodiments, the DC source 11 can be a battery, which outputs DC power to supply power to the DC converter 12.

[0034] The output of DC-DC converter 12 is electrically connected to the input of inverter 13 via diode D1. The DC-DC conversion circuit 121 receives the DC power output from DC source 11 and converts it to power inverter 13. In some embodiments, the conversion circuit 121 may include any one of a BOOST circuit, a BUCK circuit, a BUCK-BOOST circuit, or a combination of these circuits. For example, a typical BOOST circuit utilizes a fully controlled switch, a freewheeling diode, and an inductor and capacitor to form a DC / DC boost circuit. The voltage conversion function of the BOOST circuit is achieved by modulating the control signal (e.g., a pulse width modulation (PWM) signal) that controls the switching state transition of the switch.

[0035] In some implementations, the DC-DC converter 12 operates in Maximum Power Point Tracking (MPPT) mode. MPPT mode means that the DC-DC converter 12 controls the output voltage of the DC source 11 to enable the DC source 11 to output DC power at maximum power, thereby maximizing the output capability of the DC source 11. Specifically, the DC controller 122 can detect the output voltage of the DC source 11 and further adjust the output voltage of the DC source 11 based on the output voltage to ensure that the DC source 11 outputs maximum power.

[0036] The anode of diode D1 is connected to the output terminal of DC-DC converter 12, and the cathode of diode D1 is connected to the input terminal of inverter 13. Diode D1 is used to prevent fault propagation. For example, in applications where multiple inverters 13 are connected in parallel, such as... Figure 4As shown, when one or more inverters 13 fail (e.g., a short-circuit fault), diode D1 can isolate the one or more faulty inverters 13 from the other inverters 13, thereby decoupling the one or more faulty inverters 13 from the other inverters 13, minimizing fault isolation, preventing fault propagation, and improving the reliability of the power generation system 100.

[0037] It is understood that in some embodiments, the power generation system 100 may not include diode D1, as long as inverter 13 and DC-DC converter 12 are isolated from each other. For example, inverter 13 and DC-DC converter 12 may be located in different devices that are geographically far apart. In other embodiments, diode D1 may be replaced by other semiconductors or switching elements, such as transistors, MOSFETs, controlled switches, etc.

[0038] The two ends of capacitor C1 are electrically connected to the two output terminals of DC-DC converter 121, and one end of capacitor C1 is electrically connected to the anode of diode D1. It can be understood that capacitor C1 is the output capacitor of DC-DC converter 12, used to filter the output voltage of DC-DC converter 12 to reduce voltage ripple and thus make the output voltage of DC-DC converter 12 smoother.

[0039] The two ends of capacitor C2 are electrically connected to the two input terminals of inverter circuit 131, and one end of capacitor C1 is electrically connected to the cathode of diode D1. It can be understood that capacitor C2 is the input capacitor of inverter 13, used to filter the input voltage of inverter 13.

[0040] The inverter circuit 131 in inverter 13 is used to convert the DC power output from DC converter 12 into AC power and connect the AC power to the power grid 14. The inverter circuit 131 may include a power conversion system (PCS), a direct current to alternating current (DC / AC) conversion circuit, etc.

[0041] The controller 15 is used to control the operation of the DC-DC converter 12 and the inverter 13. For example, the inverter controller 132 is used to acquire electrical parameter information of the power grid 14 and generate control signals based on the electrical parameter information to control the input voltage of the inverter circuit 131 and the output voltage of the DC-DC converter 121. The inverter controller 132 transmits the control signals to the DC controller 122 via communication, and the DC controller 122 generates an output voltage reference value based on the control signals to control the output voltage of the DC-DC converter 121. In some embodiments, the inverter controller 132 can communicate wirelessly with the DC controller 122. It is understood that this application does not limit the communication method between the inverter controller 132 and the DC controller 122.

[0042] It is understood that the DC controller 122 provided in this application can detect the output power of the DC converter 12 and control the DC converter circuit 121 to charge the capacitor C1 when the output power value of the DC converter 12 drops to less than or equal to a preset power threshold.

[0043] It is understandable that when a high-voltage ride-through occurs, the voltage of the grid 14 increases, and the input voltage of the inverter 13 also needs to increase. This causes the voltage at the cathode of diode D1 to be greater than the voltage at the anode of diode D1, resulting in diode D1 being reverse-biased and the electrical connection between the DC-DC converter 12 and the inverter 13 being disconnected. The output power of the DC-DC converter 12 decreases, preventing the inverter 13 from outputting active power to the grid 14 during the high-voltage ride-through, thus failing to guarantee continuous operation of the inverter 13 without disconnecting from the grid. However, if the high-voltage ride-through status information and the control signal corresponding to the output voltage of the DC-DC converter circuit 121 are transmitted to the DC-DC controller 122 via communication, due to communication delays, the high-voltage ride-through status information and the control signal corresponding to the output voltage of the DC-DC converter circuit 121 may not be transmitted to the DC-DC controller 122 in time. This causes the DC-DC converter circuit 121 to be unable to adjust the output power according to the voltage changes of the grid 14 in a timely manner, preventing the inverter 13 from providing active power to the grid 14 in a timely manner during the high-voltage ride-through.

[0044] Furthermore, when diode D1 is reverse-biased, the output current of DC-DC converter 12 decreases significantly, meaning the output power of DC-DC converter 12 decreases significantly. Therefore, when the output power of DC-DC converter 12 is less than or equal to a preset power threshold, diode D1 is cut off, and the output voltage of DC-DC converter 12 needs to be adjusted.

[0045] However, for diode D1 to conduct, the anode voltage of diode D1 must be greater than the cathode voltage, meaning the output voltage of DC-DC converter 12 must be greater than the input voltage of inverter 13. Therefore, when the output power of DC-DC converter 12 is less than or equal to a preset power threshold, charging capacitor C1 can increase the output voltage of DC-DC converter 12, which in turn increases the anode voltage of diode D1.

[0046] In some embodiments, capacitor C1 can be charged by constant current or constant power. This application does not limit the charging method of capacitor C1.

[0047] It is understood that the DC controller 122 can control the DC conversion circuit 121 to stop charging the capacitor C1 when the electrical connection between the DC converter 12 and the inverter 13 is established. In some embodiments, the DC controller 122 can obtain the rate of change of the output voltage of the DC converter 12 (i.e., the slope value of the output voltage), and when the slope value of the output voltage of the DC converter 12 is less than or equal to a preset slope value (i.e., when the rate of change of the output voltage of the DC converter 12 is less than or equal to a preset rate), the DC controller 122 controls the DC conversion circuit 121 to stop charging the capacitor C1.

[0048] It is understood that when the DC controller 122 detects that the output power of the DC converter 12 is less than or equal to a preset power threshold, it controls the DC converter circuit 121 to charge the capacitor C1 to quickly increase the output voltage of the DC converter 12, thereby increasing the output power of the DC converter 12. Specifically, the DC controller 122 can control the DC converter circuit 121 to charge the capacitor C1 in a constant current or constant power manner.

[0049] When the DC-DC converter circuit 121 charges capacitor C1, the output voltage of the DC-DC converter 12 continuously increases. When the output voltage of the DC-DC converter 12 is greater than the input voltage of the inverter 13, diode D1 will conduct. However, when the diode is in the off state, the DC-DC converter 12 cannot obtain the input voltage value of the inverter 13, that is, the input voltage value of the inverter 13 cannot be used as a comparison reference for the output voltage of the DC-DC converter 12.

[0050] Since the output capacitor (i.e., capacitor C1) of DC-DC converter 12 is connected in parallel with the input capacitor (i.e., capacitor C2) of inverter 13 after diode D1 is turned on, the growth rate of the output voltage of DC-DC converter 12 slows down. Therefore, DC-DC converter 12 can obtain the rate of change of the output voltage of DC-DC converter 12 (i.e., the slope value of the output voltage of DC-DC converter 12), and when the rate of change decreases to less than or equal to the preset rate, control DC-DC converter circuit 121 to stop charging capacitor C1.

[0051] It is understood that, in this embodiment, after the electrical connection between the DC-DC converter 12 and the inverter 13 is established, the DC controller 122 can also adjust the output voltage reference value according to the current output voltage of the DC-DC converter 12, and control the output voltage of the DC-DC converter 12 according to the output voltage reference value. When the slope of the output voltage of the DC-DC converter 12 is less than or equal to a preset slope value, diode D1 conducts. To ensure a stable conduction state of diode D1, the DC-DC converter 12 adjusts the output voltage reference value according to the current output voltage of the DC-DC converter 12 when the slope of its output voltage is less than or equal to the preset slope value. For example, the output voltage reference value of the DC-DC converter 12 can be the sum of the current output voltage of the DC-DC converter 12 and a preset reference voltage value. For example, the preset reference value can be 10V, 20V, etc.

[0052] It is understandable that by controlling the output voltage of the DC-DC converter 12 according to the output voltage reference value, the diode D1 can be stably turned on, so that the inverter 13 can maintain active power output during high voltage ride-through, thus ensuring the high voltage ride-through performance of the power generation system 100.

[0053] In some implementations, when the DC controller 122 receives the control signal transmitted by the inverter controller 132 in a communication manner, it can readjust the output voltage of the DC converter 12 according to the indication of the control signal, so that the output voltage of the DC converter 12 is more accurate and better matches the voltage condition of the power grid 14, thereby improving the high voltage ride-through performance of the power generation system 100.

[0054] Please see Figure 2 , Figure 2 The diagram shown is a structural schematic of the power generation system 101 provided in this application. Figure 2 As shown, power generation system 101 and Figure 1 The difference between the power generation system 101 and the power generation system 102 is that the power generation system 101 includes multiple DC converters 12, which are electrically connected to multiple DC sources 11 respectively, and the multiple DC converters 12 are connected in parallel.

[0055] Please see Figure 3 , Figure 3 The diagram shown is a structural schematic of the power generation system 102 provided in this application. Figure 3 As shown, power generation system 101 and Figure 1 The difference between the power generation system 100 and the power generation system 101 is that the power generation system 101 includes multiple inverters 13, and the multiple inverters 13 are connected in parallel.

[0056] Please see Figure 4 , Figure 4The diagram shown is a structural schematic of the power generation system 103 provided in this application. Figure 4 As shown, power generation system 101 and Figure 1 The difference between the power generation system 100 and the power generation system 101 is that the power generation system 101 includes multiple DC converters 12 and multiple inverters 13. The multiple DC converters 12 are electrically connected to multiple DC sources 11 respectively, and the multiple DC converters 12 are connected in parallel, and the multiple inverters 13 are connected in parallel.

[0057] Based on the aforementioned power generation systems 100, 101, 102, and 103, this application provides a voltage control method that enables the output voltage of the DC converter 12 to be adjusted in a timely manner according to the input voltage of the inverter 13, thereby ensuring the high voltage ride-through performance of the power generation systems 100, 101, 102, and 103.

[0058] Please see Figure 5 , Figure 5 The diagram shows a flowchart of the voltage control method provided in this application. The voltage control method can be used to control the output voltage of the DC-DC converter 12. The voltage control method provided in this application is illustrated below using a power generation system 100 as an example.

[0059] like Figure 5 As shown, the voltage control method provided in this application includes the following steps:

[0060] Step S1: Detect the output power of DC-DC converter 12.

[0061] Step S2: When the output power of DC converter 12 is less than or equal to a preset power threshold, control DC converter circuit 121 to charge capacitor C1.

[0062] Step S3: When the electrical connection between DC converter 12 and inverter 13 is made on, control DC converter circuit 121 to stop charging capacitor C1, and adjust the output voltage reference value of DC converter 12 according to the current output voltage of DC converter 12.

[0063] Step S4: Control the output voltage of DC converter 12 according to the output voltage reference value.

[0064] It is understood that, in the embodiments of this application, the steps in the voltage control method can be executed by the controller 12. For example, the voltage control method can be executed by the DC controller 122. See the attached document for details. Figures 1-4 The description of the DC controller 122 in the document will not be repeated here.

[0065] Understandable, such as Figure 5 As shown, in some embodiments, the voltage control method further includes:

[0066] Step S5: Receive the control signal and update the output voltage reference value according to the control signal.

[0067] It is understood that the control signal can be generated by the inverter controller 132 in the inverter 13 based on electrical parameter information. The control signal is used to control the output voltage of the DC-DC converter circuit 121. The inverter controller 132 transmits the control signal to the DC controller 122 via communication. The DC controller 122 updates the output voltage reference value based on the received control signal, and then controls the output voltage of the DC-DC converter 12 according to the updated output voltage reference value. This makes the output voltage of the DC-DC converter 12 more compatible with the voltage conditions of the power grid 14, thereby improving the high-voltage ride-through performance of the power generation system 100.

[0068] Therefore, the voltage control method of this application does not rely on the inverter 13 to transmit high voltage ride-through information to the DC converter 12 via communication. The control method is simple and can quickly increase the output voltage of the DC converter 12 during high voltage ride-through to ensure the high voltage ride-through performance of the power generation system 100.

[0069] In some embodiments, the voltage control method provided in this application includes, in addition to, Figure 5 In addition to steps S1-S4 or S1-S5 shown, the following steps may also be included:

[0070] Step S6: Receive the control signal and adjust the output voltage of the DC-DC converter 12 according to the control signal.

[0071] It is understood that the DC controller 122 can generate an output voltage reference value based on the control signal, and in some embodiments, the DC-DC converter circuit 121 can adjust its own output voltage based on the output voltage reference value.

[0072] When the voltage of the power grid 14 exceeds the voltage threshold, the input voltage of the inverter 13 increases due to the control of the inverter controller 132, while the output voltage of the DC-DC converter 12 remains unchanged. Diode D1 is then disconnected, reducing the output power of the DC-DC converter 12. Therefore, to reduce the impact of communication delay between the inverter controller 132 and the DC controller 122, the DC controller 122 can directly detect the output power of the DC-DC converter 12 without waiting for the control signal transmitted by the inverter controller 132. This ensures that the power generation system 100 continuously and stably outputs active power during high-voltage ride-through.

[0073] The following continues with Figure 1 Taking the example of a power grid 14 in the power generation system 100 having a rated voltage of 800V and a voltage of 960V during high voltage ride-through, this application details the voltage control method provided.

[0074] When the voltage of the mains grid 14 is the rated voltage of 800V, the inverter controller 132 controls the input voltage of the inverter circuit 131 to be 1200V based on the 800V mains grid voltage, and transmits the control signal to the DC controller 122 via communication. The DC controller 122 controls the DC converter 12 to operate in MPPT mode and receives the control signal. The DC controller 122 generates an output voltage reference value based on the control signal.

[0075] In some embodiments, the DC-DC converter 12 can adjust its output voltage based on an output voltage reference value. For example, the DC-DC converter 12 adjusts its output voltage to 1230V. In other embodiments, the DC-DC converter 12 can also adjust its output voltage based on other conditions. That is, the output voltage of the DC-DC converter 12 can be controlled by a voltage loop including the DC controller 122, or by other loops. This application does not limit the control method of the output voltage of the DC-DC converter 12 during non-high voltage ride-through periods.

[0076] When the voltage of the grid 14 rises to 960V, the inverter controller 132 controls the input voltage of the inverter circuit 131 to rise to 1357V based on the grid voltage of 960V, that is, the cathode voltage of diode D1 is 1357V. At this time, diode D1 is disconnected, that is, the electrical connection between DC converter 12 and inverter 13 is broken, the output power of DC converter 12 drops to zero, so that inverter 13 cannot continuously output active power to grid 14.

[0077] When the DC controller 122 detects that the output power of the DC converter 12 is less than or equal to a preset power threshold, it charges the capacitor C1. For example, the DC controller 122 charges the capacitor C1 at a constant power of 10kW. It can be understood that charging the capacitor C1 can increase the output voltage of the DC converter 12, that is, increase the anode voltage of the diode D1, so as to restore the electrical connection between the DC converter 12 and the inverter 13.

[0078] When the DC controller 122 detects that the slope value of the output voltage of the DC converter 12 is less than or equal to a preset slope value, the inverter 13 can continuously output active power to the grid 14.

[0079] After the electrical connection between DC-DC converter 12 and inverter 13 is re-established, DC controller 122 controls DC-DC converter circuit 121 to stop charging capacitor C1 and adjusts the current output voltage of DC-DC converter 12 by adding 20V to adjust it to the reference value of DC-DC converter 12's output voltage. It can be understood that after diode D1 conducts, the output voltage of DC controller 122 is approximately equal to the input voltage of inverter circuit 131, which is 1357V. Therefore, DC controller 122 adjusts 1377V to the reference value of DC-DC converter 12's output voltage, and DC-DC converter circuit 121 adjusts its own output voltage according to the reference value. For example, DC-DC converter circuit 121 adjusts its own output voltage to 1377V. Before DC controller 122 receives a control signal, the output voltage of DC-DC converter 12 remains at 1377V, ensuring that inverter 13 continuously outputs active power to grid 14 during high-voltage ride-through.

[0080] After receiving the control signal, the DC controller 122 adjusts the output voltage of the DC converter 12 to the new output voltage reference value indicated by the control signal to ensure the high voltage ride-through performance stability of the power generation system 100.

[0081] Please see Figure 6 , Figure 6 The diagram shown is a signal timing diagram of the DC-DC converter 12 provided in this application.

[0082] like Figure 6 As shown, before time t1, the voltage value of grid 14 was normal, and no high-voltage ride-through occurred. This is understandable. Figure 6 The voltage of the power grid 14 is an effective value. The DC-DC converter 12 operates in MPPT mode, at which time the output power of the DC-DC converter 12 is controlled by the load side (i.e., the inverter 13). The inverter controller 132 transmits the control signal corresponding to the output power of the DC-DC converter circuit 121 to the DC controller 122 via communication. The DC controller 122 controls the output power of the DC-DC converter 12 according to the control signal.

[0083] At time t1, the voltage of grid 14 suddenly increases, i.e., a high-voltage ride-through occurs. At this time, the input voltage of inverter 13 increases synchronously, diode D1 is reverse-biased and cut off, the active power output of inverter 13 decreases, and the output power of DC-DC converter 12 also decreases. For example, the output power of DC-DC converter 12 drops to zero.

[0084] At time t2, the DC controller 122 can detect that the output power of the DC converter 12 is less than or equal to a preset power threshold, and control the conversion circuit 121 to charge the capacitor C1. Therefore, the output voltage of the DC converter 12 rises.

[0085] At time t3, the output voltage of DC-DC converter 12 rises to the conduction voltage threshold of diode D1, and diode D1 turns on. At this time, the output capacitor (i.e., capacitor C1) of DC-DC converter 12 is connected in parallel with the input capacitor (i.e., capacitor C2) of inverter 13.

[0086] During the time interval t3-t4, the rate of increase of the output voltage of DC-DC converter 12 slows down. DC controller 122 controls DC-DC converter circuit 121 to stop charging C1, and adjusts the output voltage reference value of DC-DC converter 12 according to the output voltage of DC-DC converter 12 at this time.

[0087] At time t4, the DC controller 122 controls the output voltage of the DC-DC converter circuit 121 according to the output voltage reference value so that the diode D1 is stably turned on.

[0088] At time t5, the DC controller 122 receives the control signal and updates the output voltage reference value according to the control signal.

[0089] It is understood that, in some embodiments, the DC controller 122 provided in this application includes a terminal capable of automatically performing numerical calculations and / or information processing according to pre-set or stored instructions. Its hardware includes, but is not limited to, microprocessors, application-specific integrated circuits, programmable gate arrays, digital processors, and embedded devices. In some embodiments, the DC controller 122 or the inverter controller 132 further includes a memory for storing program code and various data. Memory may include read-only memory (ROM), random access memory (RAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), one-time programmable read-only memory (OTPROM), electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, disk storage, magnetic tape storage, or any other computer-readable medium capable of carrying or storing data.

[0090] In some embodiments, the DC controller 122 and the inverter controller 132 may include integrated circuits, such as a single-packaged integrated circuit or multiple integrated circuits in packages with the same or different functions, including microprocessors, digital processing chips, graphics processors, and combinations of various control chips. The DC controller 122 and the inverter controller 132 perform various functions and process data by running or executing programs or modules stored in memory and by calling data stored in memory.

[0091] The integrated unit implemented as a software functional module described above can be stored in a computer-readable storage medium. This software functional module, stored in a storage medium, includes several instructions to cause a computer device (which may be a personal computer, terminal, or network device, etc.) or processor to execute portions of the methods of the various embodiments of this application.

[0092] The memory stores program code, and the DC controller 122 and inverter controller 132 can call the program code stored in the memory to execute related functions. In one embodiment of this application, the memory stores multiple instructions, which are executed by the DC controller 122 to perform a voltage control method. For example, the specific implementation method of the DC controller 122 for the above instructions can be found in [reference needed]. Figure 5 The descriptions of the relevant steps in the corresponding embodiments are not repeated here.

[0093] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A voltage control method applied to a power generation system, the power generation system comprising a DC-DC converter, an inverter, and a controller, the DC-DC converter comprising a DC-DC conversion circuit and an output capacitor, the input terminal of the DC-DC conversion circuit being connected to a DC source, the first output terminal of the DC-DC conversion circuit being connected to the first input terminal of the inverter and the first terminal of the output capacitor, the second output terminal of the DC-DC conversion circuit being connected to the second input terminal of the inverter and the second terminal of the output capacitor, and the output terminal of the inverter being connected to the power grid, characterized in that... The voltage control method is executed by the controller, and the voltage control method includes: Detect the output power of the DC-DC converter; When the output power of the DC-DC converter drops to less than or equal to a preset power threshold, the DC-DC converter circuit is controlled to charge the output capacitor. When the electrical connection between the DC converter and the inverter is made on, the DC converter circuit is controlled to stop charging the output capacitor, and the output voltage reference value of the DC converter is adjusted according to the current output voltage of the DC converter, so as to control the output voltage of the DC converter according to the output voltage reference value.

2. The voltage control method as described in claim 1, characterized in that, When the electrical connection between the DC converter and the inverter is established, controlling the DC conversion circuit to stop charging the output capacitor includes: The rate of change of the output voltage of the DC-DC converter is obtained, and when the rate of change decreases to less than or equal to a preset rate, the DC-DC converter circuit is controlled to stop charging the output capacitor.

3. The voltage control method as described in claim 1 or 2, characterized in that, The voltage control method further includes: Receive control signals and update the output voltage reference value according to the control signals; The control signal is generated by the inverter and is used to indicate the output voltage reference value.

4. The voltage control method as described in claim 1 or 2, characterized in that, The voltage control method further includes: Receive control signals and adjust the output voltage of the DC-DC converter according to the control signals; The control signal is generated by the inverter and is used to indicate the output voltage of the DC-DC converter.

5. The voltage control method as described in claim 1 or 2, characterized in that, The control of the DC-DC converter circuit to charge the output capacitor includes: The DC-DC converter circuit is controlled to charge the output capacitor in a constant current or constant power manner.

6. A power generation system, comprising a DC-DC converter, an inverter, and a controller, wherein the DC-DC converter includes a DC-DC conversion circuit and an output capacitor, an input terminal of the DC-DC conversion circuit is connected to a DC source, a first output terminal of the DC-DC conversion circuit is connected to a first input terminal of the inverter and a first terminal of the output capacitor, a second output terminal of the DC-DC conversion circuit is connected to a second input terminal of the inverter and a second terminal of the output capacitor, and an output terminal of the inverter is connected to a power grid, characterized in that... The controller is used for: Detect the output power of the DC-DC converter; When the output power of the DC-DC converter drops to less than or equal to a preset power threshold, the DC-DC converter circuit is controlled to charge the output capacitor. When the electrical connection between the DC converter and the inverter is made on, the DC converter circuit is controlled to stop charging the output capacitor, and the output voltage reference value of the DC converter is adjusted according to the current output voltage of the DC converter, so as to control the output voltage of the DC converter according to the output voltage reference value.

7. The power generation system as described in claim 6, characterized in that, The controller is also used for: Obtain the rate of change of the output voltage of the DC-DC converter; When the rate of change decreases to less than or equal to a preset rate, the DC-DC converter circuit is controlled to stop charging the output capacitor.

8. The power generation system as described in claim 6 or 7, characterized in that, The controller is also used for: Receive control signals and update the output voltage reference value according to the control signals; The control signal is generated by the inverter and is used to indicate the output voltage reference value.

9. The power generation system as described in claim 6 or 7, characterized in that, The controller is also used for: Receive control signals and adjust the output voltage of the DC-DC converter according to the control signals; The control signal is generated by the inverter and is used to indicate the output voltage of the DC-DC converter.

10. The power generation system as described in claim 6 or 7, characterized in that, The power generation system further includes a switching element, the first end of which is electrically connected to the first output terminal of the DC-DC converter, and the second end of which is electrically connected to the first input terminal of the inverter. When the difference between the voltage at the second end of the switching element and the voltage at the first end of the switching element is greater than a preset value, the switching element is disconnected, and the controller controls the DC-DC converter circuit to charge the output capacitor.

11. The power generation system as described in claim 10, characterized in that, When the switching element is turned on, the controller controls the DC-DC converter circuit to stop charging the output capacitor.

12. The power generation system as described in claim 10, characterized in that, The switching element is a diode.

13. The power generation system as described in claim 6, 7, 11, or 12, characterized in that, The DC source is a photovoltaic module, and the power generation system constitutes a photovoltaic power generation system.

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