Photovoltaic power station virtual synchronization control method and device suitable for black start

Abstract

The invention provides a photovoltaic power station virtual synchronous control method and device suitable for black start. A first control signal can be output in an active standby control mode, a damping coefficient is determined according to the angular frequency variation of an alternating current power grid, and a second control signal is output, so that virtual synchronous control of a photovoltaic power station is realized. The active standby control mode is adopted, the damping coefficient determined according to the angular frequency variation of the alternating current power grid is dynamically variable, it can be guaranteed that the frequency fluctuation range is basically consistent in the positive and negative intervals, the frequency adjusting characteristics are similar under different illumination conditions, and then the output power of the photovoltaic power station is balanced as much as possible; and the frequency instability of the alternating-current power grid is avoided.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a method and device for virtual synchronization control of a photovoltaic power station suitable for black start. Background Art

[0002] The black start of an electric power system generally refers to the process in which, after the electric power system enters a completely black state, the generator sets with self-starting capabilities in the electric power system are started first, and then the generator sets without self-starting capabilities are started, and the power supply range is gradually expanded, and finally the entire power supply is restored.

[0003] Photovoltaic power stations have the potential to be used as black-start power sources for power systems due to their small self-use load, fast startup, and wide distribution range. With the rapid development of new energy and power electronic grid-connected control technology, photovoltaic power stations can not only provide power and electricity for power systems, but also provide voltage and frequency support for power systems while outputting active power. As the proportion of photovoltaic power station installed capacity continues to increase, the demand for photovoltaic power stations as black-start power sources will become increasingly prominent.

[0004] Existing technologies usually use maximum power point tracking control (MPPT control) or power-limited operation strategies to achieve virtual synchronous control of photovoltaic power stations. When a photovoltaic power station is used as a black start power source, it faces uncertain loads and load changes, especially when the external load exceeds the photovoltaic maximum power point under current light and weather conditions. The unbalanced output power of the photovoltaic power station can easily lead to frequency instability of the AC power grid. Summary of the invention

[0005] In order to solve the problem that the frequency of the AC power grid is easily destabilized in the prior art, the present application provides a virtual synchronization control method for a photovoltaic power station suitable for black start, which may include:

[0006] According to the actual value of the output voltage and the actual value of the output current of the photovoltaic power station, an active standby control method is adopted to output a first control signal.

[0007] The damping coefficient is determined according to the angular frequency variation of the AC power grid, and the second control signal is output according to the damping coefficient.

[0008] A DC converter connected to the photovoltaic power station is controlled according to the first control signal, and a voltage source converter (VSC) connected to the DC converter is controlled according to the second control signal.

[0009] In some possible implementations, according to the actual value of the output voltage and the actual value of the output current of the photovoltaic power station, the first control signal is outputted in an active standby control mode, including:

[0010] The actual value of the output power of the photovoltaic power station is calculated according to the actual value of the output voltage and the actual value of the output current of the photovoltaic power station.

[0011] The output voltage reference value of the photovoltaic power station is determined according to the actual output power value of the photovoltaic power station and the output power reference value of the photovoltaic power station.

[0012] The voltage difference between the output voltage reference value of the photovoltaic power station and the actual output voltage value of the photovoltaic power station is controlled proportionally and integrally to obtain the duty cycle of the thyristor in the DC converter.

[0013] The duty cycle of the thyristor is modulated to output a first control signal.

[0014] Optionally, the actual output power value of the photovoltaic power station meets: P PV =U PV ×I PV Or the actual output power value of the photovoltaic power station meets: P PV =U PV ×I PV -k DC (U DCref -U DC ). Among them, P PV Indicates the actual output power value of the photovoltaic power station, U PV Indicates the actual output voltage value of the photovoltaic power station, I PV Indicates the actual value of the output current of the photovoltaic power station, k DC Represents the proportional adjustment coefficient, U DCref Indicates the output voltage reference value of the DC converter, U DC Indicates the actual value of the output voltage of the DC converter.

[0015] Further, determining an output voltage reference value of the photovoltaic power station according to an actual output power value of the photovoltaic power station and an output power reference value of the photovoltaic power station includes:

[0016] If the actual output power value of the photovoltaic power station is greater than the output power reference value of the photovoltaic power station, or the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station and the ratio of the power difference of the photovoltaic power station at adjacent moments to the voltage difference of the photovoltaic power station at adjacent moments is greater than 0, the output voltage reference value of the photovoltaic power station at time t-1 is superimposed with the preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t.

[0017] If the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station, and the ratio of the power difference value of the photovoltaic power station at adjacent times to the voltage difference value of the photovoltaic power station at adjacent times is less than 0, the output voltage reference value of the photovoltaic power station at time t-1 is subtracted from the preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t.

[0018] Exemplarily, the damping coefficient satisfies:

[0019]

[0020] Where D is the damping coefficient, P pvref Represents the output power reference value of the photovoltaic power station, ω ref Indicates the reference angular frequency of the AC grid, Δω max Indicates the change in angular frequency of the AC power grid.

[0021] In another possible implementation, outputting the second control signal according to the damping coefficient includes:

[0022] The actual value of active power and the actual value of reactive power output by the voltage source converter are calculated according to the actual value of output current and the actual value of output voltage of the voltage source converter.

[0023] According to the damping coefficient and the actual value of the active power output by the voltage source converter, a phase reference value of the voltage source converter is obtained by adopting a virtual synchronous control method.

[0024] According to the actual value of reactive power output by the voltage source converter and the actual value of output voltage amplitude, a reference value of output voltage amplitude of the voltage source converter is obtained by adopting a virtual synchronous control method.

[0025] An output voltage reference value of the voltage source converter is determined according to a phase reference value and an output voltage amplitude reference value.

[0026] The actual value of the output current of the voltage source converter is subjected to Park transformation to obtain the current component in the two-phase rotating coordinate system, and the actual value of the output voltage of the voltage source converter is subjected to Park transformation to obtain the voltage component in the two-phase rotating coordinate system.

[0027] According to the output voltage reference value of the voltage source converter, voltage and current double closed-loop control is performed on the current component and the voltage component in the two-phase rotating coordinate system to obtain the three-phase voltage reference value of the voltage source converter.

[0028] The three-phase voltage reference value of the voltage source converter is modulated to output a second control signal.

[0029] It can be seen that the present application realizes the output of the second control signal through the active power-frequency control strategy. A dynamically variable damping coefficient is adopted in the active power-frequency control strategy to keep the output voltage frequency of the VSC within the requirement at all times and to ensure the normal operation of the photovoltaic power station.

[0030] On the other hand, the present application also provides a photovoltaic power station virtual synchronization control device suitable for black start, comprising:

[0031] The first output module is used to output a first control signal in an active standby control mode according to an actual value of an output voltage and an actual value of an output current of the photovoltaic power station.

[0032] The second output module is used to determine the damping coefficient according to the angular frequency change of the AC power grid, and output a second control signal according to the damping coefficient.

[0033] The control module is used to control a DC converter connected to the photovoltaic power station according to a first control signal, and to control a voltage source converter connected to the DC converter according to a second control signal.

[0034] In a possible implementation, the first output module is specifically configured to:

[0035] The actual value of the output power of the photovoltaic power station is calculated according to the actual value of the output voltage and the actual value of the output current of the photovoltaic power station.

[0036] The output voltage reference value of the photovoltaic power station is determined according to the actual output power value of the photovoltaic power station and the output power reference value of the photovoltaic power station.

[0037] The voltage difference between the output voltage reference value of the photovoltaic power station and the actual output voltage value of the photovoltaic power station is controlled proportionally and integrally to obtain the duty cycle of the thyristor in the DC converter.

[0038] The duty cycle of the thyristor is modulated to output a first control signal.

[0039] Optionally, the actual output power value of the photovoltaic power station meets P PV =U PV ×I PV Alternatively, the actual output power value of the photovoltaic power station satisfies P PV =U PV ×I PV -k DC (U DCref -U DC ). Among them, P PV Indicates the actual output power value of the photovoltaic power station, U PV Indicates the actual output voltage value of the photovoltaic power station, I PV Indicates the actual value of the output current of the photovoltaic power station, k DC Represents the proportional adjustment coefficient, U DCref Indicates the output voltage reference value of the DC converter, U DC Indicates the actual value of the output voltage of the DC converter.

[0040] In another possible implementation, the first output module is specifically configured to:

[0041] If the actual output power value of the photovoltaic power station is greater than the output power reference value of the photovoltaic power station, or the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station and the ratio of the power difference of the photovoltaic power station at adjacent times to the voltage difference of the photovoltaic power station at adjacent times is greater than 0, the output voltage reference value of the photovoltaic power station at time t-1 is superimposed with the preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t.

[0042] If the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station, and the ratio of the power difference value of the photovoltaic power station at adjacent times to the voltage difference value of the photovoltaic power station at adjacent times is less than 0, the output voltage reference value of the photovoltaic power station at time t-1 is subtracted from the preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t.

[0043] Exemplarily, the damping coefficient satisfies:

[0044]

[0045] Where D is the damping coefficient, P pvref Represents the output power reference value of the photovoltaic power station, ω ref Indicates the reference angular frequency of the AC grid, Δω max Indicates the change in angular frequency of the AC power grid.

[0046] In yet another possible implementation, the second output module is specifically configured to:

[0047] The actual value of active power and the actual value of reactive power output by the voltage source converter are calculated according to the actual value of output current and the actual value of output voltage of the voltage source converter.

[0048] According to the damping coefficient and the actual value of the active power output by the voltage source converter, a phase reference value of the voltage source converter is obtained by adopting a virtual synchronous control method.

[0049] According to the actual value of reactive power output by the voltage source converter and the actual value of output voltage amplitude, a reference value of output voltage amplitude of the voltage source converter is obtained by adopting a virtual synchronous control method.

[0050] An output voltage reference value of the voltage source converter is determined according to a phase reference value and an output voltage amplitude reference value.

[0051] The actual value of the output current of the voltage source converter is subjected to Park transformation to obtain the current component in the two-phase rotating coordinate system, and the actual value of the output voltage of the voltage source converter is subjected to Park transformation to obtain the voltage component in the two-phase rotating coordinate system.

[0052] According to the output voltage reference value of the voltage source converter, voltage and current double closed-loop control is performed on the current component and the voltage component in the two-phase rotating coordinate system to obtain the three-phase voltage reference value of the voltage source converter.

[0053] The three-phase voltage reference value of the voltage source converter is modulated to output a second control signal.

[0054] On the other hand, the present application also provides a computer device, including: one or more processors.

[0055] A processor is used to execute one or more programs.

[0056] When one or more programs are executed by one or more processors, the control method as described above is implemented.

[0057] In another aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed, the control method described above is implemented.

[0058] Compared with the prior art, the beneficial effects of this application are:

[0059] The photovoltaic power station virtual synchronization control method suitable for black start provided in the present application can output a first control signal according to the actual value of the output voltage and the actual value of the output current of the photovoltaic power station and adopt an active standby control method, determine the damping coefficient according to the angular frequency change of the AC power grid, and output a second control signal according to the damping coefficient, and then realize virtual synchronization control of the photovoltaic power station according to the first control signal and the second control signal. Since the present application adopts an active standby control method, and the damping coefficient determined according to the angular frequency change of the AC power grid is dynamically variable, it can ensure that the frequency fluctuation range is basically consistent in the positive and negative intervals, and the frequency regulation characteristics are similar under different lighting conditions, so that the output power of the photovoltaic power station is as balanced as possible, avoiding frequency instability of the AC power grid.

[0060] The present application adopts an active standby control method to control the actual value of the output voltage of the DC / DC converter, so that the actual value of the output voltage of the DC / DC converter remains stable, thereby ensuring that the actual value of the output power of the photovoltaic power station is equal to the power absorbed by the load, thereby making the photovoltaic power station operate stably.

[0061] The present application realizes the output of the second control signal through an active power-frequency control strategy. A dynamically variable damping coefficient is adopted in the active power-frequency control strategy to keep the output voltage frequency of the VSC within the requirements at all times, while ensuring the normal operation of the photovoltaic power station and avoiding affecting the frequency of the AC power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] In order to more clearly illustrate the technical solutions in the present application or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0063] Figure 1 This is a schematic structural diagram of a two-stage photovoltaic power generation system in an embodiment of the present application.

[0064] Figure 2 A schematic flowchart of a virtual synchronization control method for a photovoltaic power station in an embodiment of the present application.

[0065] Figure 3 A schematic flowchart of outputting a first control signal using an active standby control method in an embodiment of the present application.

[0066] Figure 4 Another schematic flowchart of outputting the first control signal using the active standby control method in an embodiment of the present application.

[0067] Figure 5 Schematic diagram of the output characteristic curve of the photovoltaic power station in the embodiment of the present application.

[0068] Figure 6 A schematic flowchart of determining an output voltage reference value of a photovoltaic power station in an embodiment of the present application.

[0069] Figure 7 This is a schematic flowchart of outputting a second control signal according to a damping coefficient in an embodiment of the present application.

[0070] Figure 8a Schematic waveform diagram of the actual value of the output voltage of the VSC in the embodiment of the present application.

[0071] Figure 8b A schematic waveform diagram of the actual value of the output voltage amplitude of the VSC in the embodiment of the present application.

[0072] Figure 9a A schematic waveform diagram of the actual value of the output voltage of the photovoltaic power station in the embodiment of the present application.

[0073] Figure 9b It is a schematic waveform diagram of the actual value of the output voltage of the photovoltaic power station under overload conditions in an embodiment of the present application.

[0074] Fig.10 It is a schematic waveform diagram of the actual value of the output power of the photovoltaic power station PV in the embodiment of the present application.

[0075] Fig.11 A schematic waveform diagram of the actual value of the output voltage of the DC / DC converter in an embodiment of the present application.

[0076] Fig.12 A schematic waveform diagram of the load power on the AC power grid side in an embodiment of the present application.

[0077] Fig.13 It is a schematic structural diagram of a virtual synchronous control device for a photovoltaic power station in an embodiment of the present application. DETAILED DESCRIPTION

[0078] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0079] The terms "first", "second", etc. in the specification embodiments, claims, and drawings of the present application are only used for the purpose of distinguishing descriptions, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, including a series of steps or units. The method, system, product, or device is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0080] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0081] Example 1

[0082] The embodiment of the present application provides a virtual synchronization control method for a photovoltaic power station suitable for black start. The embodiment of the present application is described by taking a two-stage photovoltaic power generation system as an example. Figure 1 As shown in FIG. 1 , a two-stage photovoltaic power generation system includes a photovoltaic array PV, a DC converter (i.e., a DC / DC converter), and a VSC. The low-voltage DC power output by the photovoltaic array PV is converted into high-voltage DC power by a DC / DC converter with a boost function, and then converted into AC power by the VSC and connected to the AC grid. Figure 1 In, L f Represents the filter inductance, C f Represents the filter capacitor, L g Indicates line inductance, U g Indicates the AC bus voltage, P load1 Represents the active power of load 1, P load2 Represents the active power of load 2, P load3 Indicates the active power of load 3.

[0083] like Figure 2 As shown, the control method 100 provided in the embodiment of the present application includes the following steps:

[0084] Step S1: According to the actual output voltage value of the photovoltaic power station PV (U PV The actual value of the output current (which can be expressed by I PV denoted by CS1), and outputs a first control signal (which can be denoted by CS1) in an active standby control mode.

[0085] Step S2: According to the angular frequency change of the AC power grid (which can be expressed as Δω max The damping coefficient (which can be represented by D) is determined, and a second control signal (which can be represented by CS2) is output according to the damping coefficient D.

[0086] Step S3: Control the DC / DC converter according to the first control signal CS1, and control the VSC according to the second control signal CS2.

[0087] During the black start process of the photovoltaic power station, the external load is put into operation in a time sequence, and the maximum power of the two-stage photovoltaic power generation system fluctuates randomly due to the influence of light and weather conditions. Therefore, the load power and the maximum power of the two-stage photovoltaic power generation system often do not match. The two-stage photovoltaic power generation system can output the maximum power by using MPPT control. When the connected load power is less than or exceeds the maximum power, the output voltage of the DC / DC converter is out of control due to power imbalance, resulting in instability of the AC power grid. In addition, if the two-stage photovoltaic power generation system adopts virtual synchronous control (ie, VSG control), its active frequency regulation characteristics also require photovoltaics to reserve a certain margin. Therefore, in the embodiment of the present application, the two-stage photovoltaic power generation system can adopt active standby control.

[0088] In some embodiments, in step S1, the actual output voltage U of the photovoltaic power station PV is PV And the actual value of output current I PV , the first control signal CS1 is outputted in an active standby control mode, such as Figure 3 and Figure 4 As shown, the following steps may be included:

[0089] According to the actual value U of the output voltage of the photovoltaic power station PV PV And the actual value of output current I PV Calculate the actual output power value P of the photovoltaic power station PV PV .

[0090] According to the actual output power value P of the photovoltaic power station PV PV And the output power reference value P of the photovoltaic power station PV PVref Determine the output voltage reference value U of the photovoltaic power station PV PVref .

[0091] The output voltage reference value U of the photovoltaic power station PV PVref The actual output voltage U of the photovoltaic power station PV PV The voltage difference U error Perform proportional integral control (PI control) to obtain the duty cycle D of the thyristor in the DC / DC converter. 1 .

[0092] Duty cycle D of thyristor 1 Modulation is performed to output a first control signal CS1.

[0093] It can be seen that the first control signal CS1 is used to control the thyristors in the DC / DC converter.

[0094] The actual output power value P of the photovoltaic power station PV PV Greater than the active power P input from the photovoltaic power station PV to the AC grid grid In the case of , the DC capacitor in the DC / DC converter is charged, and the actual output voltage value of the DC / DC converter is U DC Increase, that is, the change in the actual value of the output voltage of the DC / DC converter △U DC If P is negative, PV Greater than U PV ×I PV On the contrary, the actual output power value P of the photovoltaic power station PV PV Less than the active power P input from the photovoltaic power station PV to the AC grid grid In the case of DC capacitor discharge, U DC Decline, △U DC is positive, P PV Less than U PV ×I PV .

[0095] Optional, the actual output power value P of the photovoltaic power station PV PV Satisfaction: P PV =U PV ×I PVOr, the actual output power value P of the photovoltaic power station PV PV Satisfy P PV =U PV ×I PV -k DC (U DCref -U DC ). Among them, k DC Represents the proportional adjustment coefficient, U DCref Indicates the output voltage reference value of the DC / DC converter, U DC Indicates the actual value of the output voltage of the DC / DC converter.

[0096] It is conceivable that k DC The value of needs to be selected reasonably. DC If the value is too small, U DC If k drops to zero or overvoltage occurs, the AC power grid will become unstable. DC If the value is too large, U DC Being overly sensitive to power fluctuations may also lead to instability of the AC power grid. Through this application, the output power of the photovoltaic power station PV can be adjusted by adjusting the size of the photovoltaic power station PV output voltage, so that the two-stage photovoltaic power generation system maintains power balance and voltage stability on the DC side of the two-stage photovoltaic power generation system when the load changes.

[0097] It is also conceivable that satisfying P PV =U PV ×I PV In the case of Figure 3 . Satisfy P PV =U PV ×I PV -k DC (U DCref -U DC ), the specific process of step S1 can refer to Figure 4 It can be considered that Figure 4 P PV Based on U DC right Figure 3 P PV Corrections have been made.

[0098] Furthermore, the output characteristic curve of the photovoltaic power station PV is as follows Figure 5 shown. Figure 5 In the figure, the horizontal axis represents the output voltage of the photovoltaic power station PV, the vertical axis represents the output power of the photovoltaic power station PV, Pmppt represents the maximum output power of the photovoltaic power station PV, Umppt represents the output voltage corresponding to the maximum output power of the photovoltaic power station PV, and U OC Indicates the open circuit voltage of the photovoltaic power station PV.

[0099] Depend on Figure 5 It can be seen that at the MPPT point (i.e. Figure 5 In the left part of the MPPT point (in the middle), the ratio of the power difference of the photovoltaic power station PV at adjacent moments (which can be expressed by △P) to the voltage difference of the photovoltaic power station PV at adjacent moments (which can be expressed by △U) (i.e. △P / △U) is greater than 0, i.e. △P / △U>0, and the change trends of voltage and power are consistent. In the right part of the MPPT point, △P / △U<0, and the change trends of voltage and power are opposite. The active standby control method can keep the stable operation point of the photovoltaic power station PV at the right part of the MPPT point. Therefore, according to the actual output power value P of the photovoltaic power station PV PV And the output power reference value P of the photovoltaic power station PV PVref Determine the output voltage reference value U of the photovoltaic power station PV PVref ,refer to Figure 6 , can be divided into two cases:

[0100] (1) If the actual output power value of the photovoltaic power station PV is P PV Greater than the output power reference value P of the photovoltaic power station PV PVref (That is, P PV >P PVref );or, the actual output power value P of the photovoltaic power station PV PV Less than the output power reference value P of the photovoltaic power station PV PVref And the ratio of the power difference of the photovoltaic power station PV at adjacent times (which can be expressed by △P) to the voltage difference △U of the photovoltaic power station PV at adjacent times (i.e. △P / △U) is greater than 0, the output voltage reference value of the photovoltaic power station PV at time t-1 (which can be expressed by U PVref (t-1)) and the preset voltage increment (which can be expressed by △U set The output voltage reference value of the photovoltaic power station PV at time t (which can be represented by U PVref (t) indicates). That is, it satisfies: U PVref (t) = U PVref (t-1)+△U set .

[0101] (2) If the actual output power value of the photovoltaic power station PV is P PV Less than the output power reference value P of the photovoltaic power station PV PVref (That is, P PV <P PVref ), and the ratio of the power difference △P of the photovoltaic power station PV at adjacent times to the voltage difference △P / △U of the photovoltaic power station PV at adjacent times is less than 0, the output voltage reference value U of the photovoltaic power station PV at time t-1 is PVref (t-1) and the preset voltage increment △U setSubtract the output voltage reference value U of the photovoltaic power station PV at time t. PVref (t). That is, it satisfies: U PVref (t) = U PVref (t-1)-△U set .

[0102] During the black start process, P PV It will change with the load switching. In order to ensure that the frequency fluctuation range is basically consistent in the positive and negative ranges, and the frequency regulation characteristics are similar under different lighting conditions, the damping coefficient can be set to a dynamically variable damping coefficient. The damping coefficient satisfies:

[0103]

[0104] Where D is the damping coefficient, P pvref Represents the output power reference value of the photovoltaic power station PV, ω ref Indicates the reference angular frequency of the AC grid, Δω max Represents the angular frequency change of the AC power grid. It is understandable that due to the capacity limitation of photovoltaic power generation, the AC power grid capacity that can achieve black start is generally far less than 3 million kilowatts. Therefore, the frequency range that VSG control can provide in photovoltaic power generation is between 50±0.5Hz. Therefore, in the embodiment of the present application, Δω max It indicates the angular frequency change of the AC power grid within the allowable frequency deviation range of ±0.5Hz.

[0105] In some other embodiments, in the above step S2, the second control signal CS2 is output according to the damping coefficient D, such as Figure 7 As shown, the following steps are included:

[0106] Step S2a: Based on the actual output current value of the VSC (which can be expressed as I abc The actual value of the output voltage (which can be represented by U abc The actual value of the active power output of the VSC can be calculated using P e Represented) and the actual value of reactive power (which can be represented by Q e Of course, you can also e and Q e The filtering is performed, which is not limited in the embodiment of the present application.

[0107] Step S2b: According to the damping coefficient D and the actual value of the active power P output by the VSC e , the phase reference value of the VSC (which can be expressed as θ) is obtained by using the virtual synchronous control method.

[0108] Specifically, the active power reference value P of the VSC can be ref Subtract the actual value of active power P eThen divide by ω ref , and the electromagnetic torque deviation △T is obtained e △T e Subtract the damping torque △T d (Satisfy △T d =△ω×D) to obtain the mechanical torque deviation △T m , for △T m Integrate to get the frequency deviation △ω of VSC. △ω and ω ref After adding, the reference frequency ω of the VSC is obtained. By integrating ω, the phase reference value θ of the VSC can be obtained. Figure 7 In , J represents the inertia of VSC and s represents the Laplace operator.

[0109] Step S2c: Based on the actual value of reactive power Q output by the VSC e And the actual value of the output voltage amplitude (which can be represented by V), the output voltage amplitude reference value of the VSC (which can be represented by U) is obtained by adopting the virtual synchronous control method.

[0110] Specifically, the reactive power reference value Q of VSC ref Subtract the actual value of reactive power Q output by VSC e , then multiply the reactive power droop coefficient k q Get the droop voltage V d . According to the droop voltage V d , VSC rated AC voltage amplitude reference value V ref The actual value V of the output voltage amplitude of VSC can be obtained by calculating the voltage amplitude deviation △V of VSC, which satisfies △V=V d +(V ref -V). Integrate △V to obtain the output voltage amplitude reference value U of the VSC.

[0111] Step S2d: Determine the output voltage reference value of the VSC according to the phase reference value θ and the output voltage amplitude reference value U (which can be expressed as U ref express).

[0112] Specifically, the output voltage reference value U of the VSC can be obtained by multiplying the output voltage amplitude reference value U by sinθ. ref .

[0113] Step S2e: The actual value of the output current I of the VSC abc Perform Park transformation (i.e. Park transformation) to obtain the current component I in the two-phase rotating coordinate system dq , the actual value of the output voltage U of VSC abc Perform Park transformation to obtain the voltage component U in the two-phase rotating coordinate system dq .

[0114] Step S2f: According to the VSC output voltage reference value U ref , for the current component I in the two-phase rotating coordinate system dq And the voltage component U dq Perform voltage and current double closed-loop control to obtain the three-phase voltage reference value of VSC (which can be obtained by U abcref express).

[0115] Step S2g: The three-phase voltage reference value U of the VSC abcref Modulation (such as pulse width modulation, namely PWM modulation) is performed to output a second control signal CS2.

[0116] It can be seen that the control of the power tube in the VSC can be achieved through the second control signal CS2. The present application realizes the output of the second control signal CS2 through the active power-frequency control strategy. A dynamically variable damping coefficient D is used in the active power-frequency control strategy to keep the output voltage frequency of the VSC within the requirements at all times, while ensuring the normal operation of the cascade photovoltaic power generation system.

[0117] The following is a two-stage photovoltaic power generation system (such as a photovoltaic power station virtual synchronization control method suitable for black start) using the embodiment of the present application. Figure 1 The simulation verification is performed as shown).

[0118] The parameter settings of the two-stage photovoltaic power generation system can refer to Table 1:

[0119] Table 1

[0120] The maximum output power of photovoltaic power station PV 50kW The maximum output voltage of photovoltaic power station PV 383.5V DC / DC converter output voltage reference value 1500V Proportional adjustment coefficient <![CDATA[0.5P mppt / 5]]> Output voltage reference value of VSC 690V Reference angular frequency of AC power grid 50Hz Primary frequency modulation coefficient of VSC <![CDATA[0.5P mppt / 0.25Hz]]> VSC moment of inertia <![CDATA[1kg·m 2 ]]> VSC zero-start boost time 0.3s

[0121] The load changes and light changes are shown in Table 2:

[0122] Table 2

[0123]

[0124] For the two-stage photovoltaic power generation system in Table 1, during the black start boost phase, Figure 8a As shown, the actual output voltage value of VSC is U abc It continuously increases from 0p.u. to 1p.u. and has a standard sinusoidal waveform. Figure 8b As shown, the actual value V of the output voltage amplitude of the VSC is always maintained near 1p.u. during the load change process. Figure 8a and Figure 8b In the figure, t represents time.

[0125] Similarly, in the black start boost phase, e.g. Figure 9a As shown, the actual output voltage value U of the photovoltaic power station PV PVIt can be stable and adjust the size according to the load change. When the load exceeds the maximum output power of the photovoltaic power station PV, the actual output voltage value U PV It can also be kept accurately at the MPPT point, such as Figure 9b shown.

[0126] The actual output power of the photovoltaic power station PV is as follows Fig.10 As shown, the actual value of the output voltage of the DC / DC converter is U DC like Fig.11 As shown, the load power P on the AC grid side load like Fig.12 As shown. Figures 10 to 12 It can be seen that the output power of the photovoltaic power station PV can follow the changes in the load power on the AC grid side to maintain the balance of the active power of the AC grid. DC During this process, the maximum drop is only 80V, maintaining U DC stability.

[0127] Embodiment 2:

[0128] Based on the same inventive concept, the embodiment of the present application also provides a PV virtual synchronization control device for a photovoltaic power station suitable for black start. Fig.13 As shown, the control device 200 may include:

[0129] The first output module 21 is used to output the actual value U of the output voltage of the photovoltaic power station PV. PV And the actual value of output current I PV , an active standby control mode is adopted to output the first control signal CS1.

[0130] The second output module 22 is used to output the angular frequency change Δω of the AC power grid. max The damping coefficient D is determined, and the second control signal CS2 is output according to the damping coefficient D.

[0131] The control module 23 is used to control the DC / DC converter connected to the photovoltaic power station PV according to the first control signal CS1, and to control the VSC connected to the DC / DC converter according to the second control signal CS2.

[0132] In a possible implementation, the first output module 21 is specifically used for:

[0133] refer to Figure 3 and Figure 4 , according to the actual output voltage value U of the photovoltaic power station PV PV And the actual value of output current I PV Calculate the actual output power value P of the photovoltaic power station PV PV .

[0134] According to the actual output power value P of the photovoltaic power station PV PV And the output power reference value P of the photovoltaic power station PV PVref Determine the output voltage reference value U of the photovoltaic power station PV PVref .

[0135] The output voltage reference value U of the photovoltaic power station PV PVref The actual output voltage U of the photovoltaic power station PV PV The voltage difference U error Perform proportional integral control (PI control) to obtain the duty cycle D of the thyristor in the DC / DC converter. 1 .

[0136] Duty cycle D of thyristor 1 Modulation is performed to output a first control signal CS1.

[0137] Optionally, the actual output power value of the photovoltaic power station PV satisfies P PV =U PV ×I PV , or, the actual output power value of the photovoltaic power station PV satisfies P PV =U PV ×I PV -k DC (U DCref -U DC ). Among them, k DC Represents the proportional adjustment coefficient, U DCref Indicates the output voltage reference value of the DC / DC converter, U DC Indicates the actual value of the output voltage of the DC / DC converter.

[0138] It is conceivable that k DC The value of needs to be selected reasonably. DC If the value is too small, U DC If k drops to zero or overvoltage occurs, the AC power grid will become unstable. DC If the value is too large, U DC Being overly sensitive to power fluctuations may also lead to instability of the AC power grid. Through this application, the output power of the photovoltaic power station PV can be adjusted by adjusting the size of the photovoltaic power station PV output voltage, so that the two-stage photovoltaic power generation system maintains power balance and voltage stability on the DC side of the two-stage photovoltaic power generation system when the load changes.

[0139] It is also conceivable that satisfying P PV =U PV ×I PV In the case of Figure 3 . Satisfy P PV =UPV ×I PV -k DC (U DCref -U DC ), the specific process of step S1 can refer to Figure 4 It can be considered that Figure 4 P PV Based on U DC right Figure 3 P PV Corrections have been made.

[0140] In another possible implementation, refer to Figure 6 , divided into the following two situations:

[0141] (1) If the actual output power value of the photovoltaic power station PV is P PV Greater than the output power reference value P of the photovoltaic power station PV PVref (That is, P PV >P PVref );or, the actual output power value P of the photovoltaic power station PV PV Less than the output power reference value P of the photovoltaic power station PV PVref The ratio of the power difference value (which can be represented by △P) of the photovoltaic power station PV at adjacent moments to the voltage difference value (which can be represented by △U) of the photovoltaic power station PV at adjacent moments (i.e., △P / △U) is greater than 0. The first output module 21 is specifically used to convert the output voltage reference value (which can be represented by U) of the photovoltaic power station PV at time t-1 into the output voltage reference value (which can be represented by U PVref (t-1)) and the preset voltage increment (which can be expressed by △U set The output voltage reference value of the photovoltaic power station PV at time t (which can be represented by U PVref (t) indicates). That is,

[0142] U PVref (t) = U PVref (t-1)+△U set .

[0143] (2) If the actual output power value of the photovoltaic power station PV is P PV Less than the output power reference value P of the photovoltaic power station PV PVref (That is, P PV <P PVref ), and the ratio of the power difference △P of the photovoltaic power station PV at adjacent moments to the voltage difference △U of the photovoltaic power station PV at adjacent moments △P / △U is less than 0, the first output module 21 is specifically used to convert the output voltage reference value U of the photovoltaic power station PV at time t-1 PVref (t-1) and the preset voltage increment △U set Subtract the output voltage reference value U of the photovoltaic power station PV at time t.PVref (t). That is, it satisfies: U PVref (t) = U PVref (t-1)-△U set .

[0144] Exemplarily, the damping coefficient satisfies:

[0145]

[0146] Where D is the damping coefficient, P pvref Represents the output power reference value of the photovoltaic power station PV, ω ref Indicates the reference angular frequency of the AC grid, Δω max Indicates the change in angular frequency of the AC power grid.

[0147] In yet another possible implementation, the second output module 22 is specifically configured to:

[0148] like Figure 7 As shown, according to the actual value of VSC output current I abc And the actual value of output voltage U abc Calculate the actual value of active power P output by VSC e And the actual value of reactive power Q e Of course, you can also e and Q e The filtering is performed, which is not limited in the embodiment of the present application.

[0149] According to the damping coefficient D and the actual value of active power P output by VSC e , the phase reference value θ of the VSC is obtained by using the virtual synchronous control method. Specifically, the active power reference value P of the VSC can be ref Subtract the actual value of active power P e Then divide by ω ref , and the electromagnetic torque deviation △T is obtained e △T e Subtract the damping torque △T d (satisfy

[0150] △T d =△ω×D) to obtain the mechanical torque deviation △T m , for △T m Integrate to get the frequency deviation △ω of VSC. △ω and ω ref After adding, the reference frequency ω of the VSC is obtained. By integrating ω, the phase reference value θ of the VSC can be obtained. Figure 7 In , J represents the inertia of VSC and s represents the Laplace operator.

[0151] According to the actual value of reactive power Q output by VSC eThe output voltage amplitude actual value V is used to obtain the output voltage amplitude reference value U of the VSC using the virtual synchronous control method. Specifically, the reactive power reference value Q of the VSC ref Subtract the actual value of reactive power Q output by VSC e , then multiply the reactive power droop coefficient k q Get the droop voltage V d . According to the droop voltage V d , VSC rated AC voltage amplitude reference value V ref The actual value V of the output voltage amplitude of VSC can be obtained by calculating the voltage amplitude deviation △V of VSC, which satisfies △V=V d +(V ref -V). Integrate △V to obtain the output voltage amplitude reference value U of the VSC.

[0152] According to the phase reference value θ and the output voltage amplitude reference value U, the output voltage reference value U of the VSC is determined. ref Specifically, the output voltage reference value U of the VSC can be obtained by multiplying the output voltage amplitude reference value U by sinθ. ref .

[0153] The actual value of the VSC output current I abc Perform Park transformation (i.e. Park transformation) to obtain the current component I in the two-phase rotating coordinate system dq , the actual value of the output voltage U of VSC abc Perform Park transformation to obtain the voltage component U in the two-phase rotating coordinate system dq .

[0154] According to the VSC output voltage reference value U ref , for the current component I in the two-phase rotating coordinate system dq And the voltage component U dq Perform voltage and current double closed-loop control to obtain the three-phase voltage reference value U of VSC abcref .

[0155] The three-phase voltage reference value U of VSC abcref Modulation (such as pulse width modulation, namely PWM modulation) is performed to output a second control signal CS2.

[0156] Embodiment 3:

[0157] Based on the same inventive concept, an embodiment of the present application also provides a computer device, which includes a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the photovoltaic power station PV virtual synchronization control method provided in the above embodiment.

[0158] Embodiment 4:

[0159] Based on the same inventive concept, the embodiment of the present application also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in the computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the photovoltaic power station PV virtual synchronization control method provided in the above embodiment.

[0160] Those skilled in the art will appreciate that the embodiments of the application may be provided as methods, systems, or computer program products. Therefore, the application may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0161] The application is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0162] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0163] 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.

[0164] The above are merely embodiments of the application and are not intended to limit the application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the application are included in the scope of the claims of the pending application.

Claims

1. A virtual synchronization control method for a photovoltaic power station suitable for black start, characterized in that: include: According to the actual value of the output voltage and the actual value of the output current of the photovoltaic power station, a first control signal is outputted in an active standby control mode; Determining a damping coefficient according to the angular frequency change of the AC power grid, and outputting a second control signal according to the damping coefficient; A DC converter connected to the photovoltaic power station is controlled according to the first control signal, and a voltage source converter connected to the DC converter is controlled according to the second control signal.

2. The control method according to claim 1, characterized in that: The method of outputting a first control signal in an active standby control mode according to an actual value of an output voltage and an actual value of an output current of the photovoltaic power station comprises: Calculate the actual output power value of the photovoltaic power station according to the actual output voltage value and the actual output current value of the photovoltaic power station; Determine an output voltage reference value of the photovoltaic power station according to an actual output power value of the photovoltaic power station and an output power reference value of the photovoltaic power station; Performing proportional-integral control on the voltage difference between the output voltage reference value of the photovoltaic power station and the actual output voltage value of the photovoltaic power station to obtain the duty cycle of the thyristor in the DC converter; The duty cycle of the thyristor is modulated to output the first control signal.

3. The control method according to claim 2, characterized in that: The actual output power value of the photovoltaic power station satisfies P PV =U PV ×I PV , or P PV =U PV ×I PV -k DC (U DCref -U DC ); Among them, P PV Indicates the actual output power value of the photovoltaic power station, U PV Indicates the actual value of the output voltage of the photovoltaic power station, I PV represents the actual value of the output current of the photovoltaic power station, k DC Represents the proportional adjustment coefficient, U DCref represents the output voltage reference value of the DC converter, U DC Indicates the actual value of the output voltage of the DC converter.

4. The control method according to claim 2, characterized in that: The step of determining the output voltage reference value of the photovoltaic power station according to the actual output power value of the photovoltaic power station and the output power reference value of the photovoltaic power station comprises: If the actual output power value of the photovoltaic power station is greater than the output power reference value of the photovoltaic power station, or the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station and the ratio of the power difference value of the photovoltaic power station at adjacent moments to the voltage difference value of the photovoltaic power station at adjacent moments is greater than 0, the output voltage reference value of the photovoltaic power station at time t-1 is superimposed with a preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t; If the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station, and the ratio of the power difference value of the photovoltaic power station at adjacent moments to the voltage difference value of the photovoltaic power station at adjacent moments is less than 0, the output voltage reference value of the photovoltaic power station at time t-1 is subtracted from the preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t.

5. The control method according to claim 1, characterized in that: The damping coefficient satisfies: Wherein, D represents the damping coefficient, P pvref represents the output power reference value of the photovoltaic power station, ω ref represents the reference angular frequency of the AC power grid, Δω max represents the angular frequency change of the AC power grid.

6. The control method according to claim 1, characterized in that: The outputting a second control signal according to the damping coefficient comprises: Calculating the actual value of active power and the actual value of reactive power output by the voltage source converter according to the actual value of output current and the actual value of output voltage of the voltage source converter; According to the damping coefficient and the actual value of the active power output by the voltage source converter, a phase reference value of the voltage source converter is obtained by adopting a virtual synchronous control method; According to the actual value of reactive power output by the voltage source converter and the actual value of output voltage amplitude, the reference value of output voltage amplitude of the voltage source converter is obtained by adopting the virtual synchronous control method; Determining an output voltage reference value of the voltage source converter according to the phase reference value and the output voltage amplitude reference value; Performing a Park transformation on the actual value of the output current of the voltage source converter to obtain a current component in a two-phase rotating coordinate system, and performing a Park transformation on the actual value of the output voltage of the voltage source converter to obtain a voltage component in a two-phase rotating coordinate system; According to the voltage reference value of the voltage source converter output voltage, voltage and current double closed-loop control is performed on the current component and the voltage component in the two-phase rotating coordinate system to obtain a three-phase voltage reference value of the voltage source converter; The three-phase voltage reference value of the voltage source converter is modulated to output the second control signal.

7. A virtual synchronization control device for a photovoltaic power station suitable for black start, characterized in that: include: A first output module is used to output a first control signal in an active standby control mode according to an actual value of an output voltage and an actual value of an output current of the photovoltaic power station; A second output module, used to determine a damping coefficient according to a change in angular frequency of the AC power grid, and output a second control signal according to the damping coefficient; The control module is used to control a DC converter connected to the photovoltaic power station according to a first control signal, and to control a voltage source converter connected to the DC converter according to a second control signal.

8. The control device according to claim 7, characterized in that: The first output module is specifically used for: Calculate the actual output power value of the photovoltaic power station according to the actual output voltage value and the actual output current value of the photovoltaic power station; Determine an output voltage reference value of the photovoltaic power station according to an actual output power value of the photovoltaic power station and an output power reference value of the photovoltaic power station; Performing proportional-integral control on the voltage difference between the output voltage reference value of the photovoltaic power station and the actual output voltage value of the photovoltaic power station to obtain the duty cycle of the thyristor in the DC converter; The duty cycle of the thyristor is modulated to output the first control signal.

9. The control device according to claim 8, characterized in that: The actual output power value of the photovoltaic power station satisfies P PV =U PV ×I PV , or P PV =U PV ×I PV -k DC (U DCref -U DC ); Among them, P PV Indicates the actual output power value of the photovoltaic power station, U PV Indicates the actual value of the output voltage of the photovoltaic power station, I PV represents the actual value of the output current of the photovoltaic power station, k DC Represents the proportional adjustment coefficient, U DCref represents the output voltage reference value of the DC converter, U DC Indicates the actual value of the output voltage of the DC converter.

10. The control device according to claim 8, characterized in that: The first output module is specifically used for: If the actual output power value of the photovoltaic power station is greater than the output power reference value of the photovoltaic power station, or the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station and the ratio of the power difference value of the photovoltaic power station at adjacent moments to the voltage difference value of the photovoltaic power station at adjacent moments is greater than 0, the output voltage reference value of the photovoltaic power station at time t-1 is superimposed with a preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t; If the actual output power value of the photovoltaic power station is less than the output power reference value of the photovoltaic power station, and the ratio of the power difference value of the photovoltaic power station at adjacent moments to the voltage difference value of the photovoltaic power station at adjacent moments is less than 0, the output voltage reference value of the photovoltaic power station at time t-1 is subtracted from the preset voltage increment to obtain the output voltage reference value of the photovoltaic power station at time t.

11. The control device according to claim 7, characterized in that: The damping coefficient satisfies: Wherein, D represents the damping coefficient, P pvref represents the output power reference value of the photovoltaic power station, ω ref represents the reference angular frequency of the AC power grid, Δω max represents the angular frequency change of the AC power grid.

12. The control device according to claim 7, characterized in that: The second output module is specifically used for: Calculating the actual value of active power and the actual value of reactive power output by the voltage source converter according to the actual value of output current and the actual value of output voltage of the voltage source converter; According to the damping coefficient and the actual value of the active power output by the voltage source converter, a phase reference value of the voltage source converter is obtained by adopting a virtual synchronous control method; According to the actual value of reactive power output by the voltage source converter and the actual value of output voltage amplitude, the reference value of output voltage amplitude of the voltage source converter is obtained by adopting the virtual synchronous control method; Determining an output voltage reference value of the voltage source converter according to the phase reference value and the output voltage amplitude reference value; Performing a Park transformation on the actual value of the output current of the voltage source converter to obtain a current component in a two-phase rotating coordinate system, and performing a Park transformation on the actual value of the output voltage of the voltage source converter to obtain a voltage component in a two-phase rotating coordinate system; According to the voltage reference value of the voltage source converter output voltage, voltage and current double closed-loop control is performed on the current component and the voltage component in the two-phase rotating coordinate system to obtain a three-phase voltage reference value of the voltage source converter; The three-phase voltage reference value of the voltage source converter is modulated to output the second control signal.

13. A computer device, characterized in that: include: one or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the control method according to any one of claims 1 to 6 is implemented.

14. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the control method according to any one of claims 1 to 6 is implemented.

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