A method and system for power control of a photovoltaic power plant

Abstract

The application provides a photovoltaic power station power control method, comprising the following steps: bringing a grid-connected point signal and a control parameter into a pre-constructed photovoltaic power station power control model, and adjusting active / reactive current output values of the photovoltaic power station; and based on the active / reactive current output values of the photovoltaic power station, controlling active / reactive frequency of a grid-connected point of the photovoltaic power station to a grid dispatching setting value. The technical scheme provided by the application adopts a modularized idea, and through the photovoltaic power station active / reactive control structure obtained by division and comprising three parts of a field station level active / reactive control module, a photovoltaic inverter control module and a photovoltaic inverter grid interface module, different types and different scales of photovoltaic power stations are reacted to access grid active / reactive operation dynamics.

Description

Technical Field

[0001] The present invention relates to the field of new energy power generation technology photovoltaic power station modeling and simulation technology, and in particular to a photovoltaic power station power control method. Background Art

[0002] Photovoltaic power generation is characterized by randomness, volatility, and intermittency, and its large-scale integration has a significant impact on the safe and stable operation of the power system. As the proportion of photovoltaic power generation in the power system continues to increase, its impact on the power grid has evolved from individual or local operational control issues to system-level safety and stability control issues, gradually transitioning from short-term electromagnetic and electromechanical transient processes to medium- and long-term dynamic processes. Under abnormal meteorological conditions such as large-scale cloud movement, sandstorms, and solar eclipses, photovoltaic power generation output may fluctuate significantly in a short period of time, resulting in high-risk "climbing events" that affect the frequency stability of the power system. Certain regions have repeatedly experienced sandstorms, large-scale cloud movement, and solar eclipses. These events often last from minutes to hours. In areas with large and concentrated photovoltaic power generation capacity, these abnormal weather conditions will have a significant impact on renewable energy power generation output, seriously threatening the safe and stable operation of the local power system.

[0003] In recent years, both academia and power companies have conducted in-depth research on photovoltaic grid integration. Research focuses primarily on fault ride-through technology for wind / photovoltaic power generation, active and reactive power control, and static and transient stability analysis. The models employed generally consider various aspects, including power electronic converters / inverters, generators, wind turbines, active and reactive power control, and fault ride-through control. The primary focus is on the dynamic characteristics of renewable energy generation on the microsecond to second scale, with the timeframe typically not exceeding one minute, falling within the realm of electromagnetic or electromechanical transient research. The emphasis is on addressing coordinated control issues on short timescales within components or local areas. Existing photovoltaic grid-connected operation standards explicitly stipulate that photovoltaic power stations must possess active and reactive power control capabilities, adjusting the power output at the grid connection point based on real-time or pre-set control commands issued by the grid dispatcher. The entire dynamic adjustment process takes approximately seconds to minutes, making it a slow regulation process.

[0004] Existing photovoltaic power generation models include electromechanical transient and electromagnetic transient models, focusing primarily on the control modeling of photovoltaic power generation units, with less attention paid to the active and reactive power control systems at the site level of the photovoltaic power station. Furthermore, traditional models are based on the actual electrical connections and control structure of the photovoltaic power station. Specifically, they require modeling of the site-level power control system and photovoltaic power generation units. When modeling the site-level control system, if the power station utilizes constant active power control, the constant active power control model is established based on the actual system during physical modeling. This model does not include frequency regulation control capabilities. When modeling a photovoltaic power station with frequency regulation, a site-level power control system model must be established based on the station's actual frequency regulation control system. This requires repeated modeling for different application scenarios, resulting in a cumbersome process. Summary of the Invention

[0005] In accordance with the grid-connected standard requirements for photovoltaic power stations, it is necessary to establish a model that can accurately reflect the slow adjustment process of active / reactive power control of photovoltaic power stations, analyze the medium- and long-term operating characteristics of photovoltaic power stations, and guide grid planning and design and dispatching operators in production and operation. At the same time, different application scenarios can be reflected by adjusting different control parameters.

[0006] In order to accurately reflect the model of the slow adjustment process of active / reactive power control of a photovoltaic power station, the present invention provides a method for implementing photovoltaic power station power control, which is suitable for slow adjustment with a time scale of approximately seconds to minutes during the entire dynamic adjustment process. A modular design approach is adopted to abstract the photovoltaic power station model including active / reactive power control functions into a site-level active / reactive power control module, a photovoltaic inverter control module, and a photovoltaic inverter grid interface control module. By setting different control parameters, the dynamic response characteristics of the active / reactive power control of the photovoltaic power station are accurately reflected, providing a model basis for the grid connection analysis of large-scale renewable energy access to the power system.

[0007] The technical solution provided by the present invention is:

[0008] A photovoltaic power station power control method is suitable for slow regulation with a time scale of approximately seconds to minutes throughout the entire dynamic adjustment process, including:

[0009] The grid connection point signal and control parameters are introduced into the pre-built PV power plant power control model to adjust the active / reactive current output value of the PV power plant;

[0010] Based on the active / reactive current output value of the photovoltaic power station, controlling the active / reactive frequency of the photovoltaic power station grid connection point to the grid dispatch set value;

[0011] The photovoltaic power station power control model includes: a station-level active / reactive power control module, a photovoltaic inverter control module and a photovoltaic inverter grid interface module;

[0012] The control parameters include: active / reactive power control instructions issued by the grid dispatcher, auxiliary frequency control signals, actual grid operation status signals, PI regulator parameters of the station-level active / reactive power control module, system frequency setpoints, and active / reactive power priority signals;

[0013] The grid connection point signal includes: grid connection point voltage value, grid connection point reactive power measurement value, system frequency measurement value, node voltage amplitude and current amplitude of the node and photovoltaic power station grid connection point transmission line.

[0014] Preferably, the photovoltaic power station power control model includes:

[0015] Station-level active / reactive power control module, photovoltaic inverter control module and photovoltaic inverter grid interface module;

[0016] The station-level active / reactive power control module includes: a station-level active power control module and a station-level reactive power control module;

[0017] The station-level active power control module includes: first-order filtering, delay control, auxiliary frequency control and active power control PI regulator with set adjustment parameters;

[0018] The station-level reactive power control module includes: first-order filtering, line compensation, reactive power limiting, lead-lag control and reactive power control PI regulator with set adjustment parameters;

[0019] The photovoltaic inverter control module includes: delay control and current limit control;

[0020] The photovoltaic inverter grid interface module includes: a delay control and a controlled AC current source.

[0021] Furthermore, the grid connection point signal and control parameters are introduced into a pre-built photovoltaic power station power control model to adjust the active / reactive current output value of the photovoltaic power station, including:

[0022] The station-level active / reactive power control module calculates the active / reactive power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station according to the grid connection point signal and the control parameters; the photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal;

[0023] The photovoltaic inverter grid interface module adjusts the active / reactive current output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value.

[0024] Furthermore, the station-level active / reactive power control module calculates the active / reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point signal and control parameters, including:

[0025] The station-level active power control module calculates the active power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the system frequency measurement value, the active power control instruction issued by the grid dispatcher, the auxiliary frequency control signal and the system frequency setting value;

[0026] The station-level reactive power control module calculates the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher and the actual operation status signal of the grid.

[0027] Furthermore, the station-level active power control module calculates the active power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station based on the system frequency measurement value, the active power control instruction issued by the grid dispatcher, the auxiliary frequency control signal and the system frequency setting value, including:

[0028] Determining whether the station-level active power control module operates in a constant active power mode or a frequency modulation control mode according to the auxiliary frequency control signal value;

[0029] When the station-level active power control module operates in the constant active power mode, the active power reference value of the entire photovoltaic power station is equal to the active power command value issued by the grid dispatcher;

[0030] When the station-level active power control module operates in frequency modulation control mode, the active power reference value of the entire photovoltaic power station is calculated based on the system frequency measurement value, the system frequency setting value and the active power command value issued by the grid dispatcher;

[0031] According to the operating conditions of each photovoltaic power generation unit in the power station, the active power reference value of each photovoltaic power generation unit is calculated based on the active power reference value of the entire photovoltaic power station.

[0032] Furthermore, the active power reference value of the entire photovoltaic power station is calculated based on the system frequency measurement value, the system frequency setting value and the active power command value issued by the grid dispatcher, including:

[0033] Obtain a frequency adjustment reference value based on the system frequency measurement value and the set system frequency value;

[0034] The frequency adjustment reference value is used as an additional control signal, and together with the active power command value issued by the grid dispatcher, the active power reference value of the entire photovoltaic power station is obtained through the PI regulator and the delay control link.

[0035] Furthermore, obtaining a frequency adjustment reference value based on the system frequency measurement value and the set system frequency value includes:

[0036] Calculating the difference between the system frequency measurement value and the set system frequency value, and comparing the difference with the set overfrequency action threshold and underfrequency action threshold;

[0037] When the difference is greater than the set over-frequency action threshold, the frequency difference is multiplied by the set over-frequency frequency modulation coefficient to obtain a frequency adjustment reference value;

[0038] When the difference is greater than the set underfrequency action threshold, the frequency difference is multiplied by the set underfrequency frequency modulation coefficient to obtain a frequency adjustment reference value.

[0039] Furthermore, the station-level reactive power control module calculates the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher, and the actual grid operation status signal, including:

[0040] Determining whether the station-level reactive power control module operates in a constant reactive power control mode or a constant voltage control mode according to the actual operation status signal value of the power grid;

[0041] When the station-level reactive power control module operates in a constant reactive power control mode, a reactive power reference value of the entire photovoltaic power station is obtained according to the reactive power command value issued by the grid dispatcher and the reactive power measurement value of the grid connection point;

[0042] When the station-level reactive power control module operates in a constant voltage control mode, the reactive power reference value of the entire photovoltaic power station is calculated based on the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, and the grid connection point voltage value;

[0043] According to the operating conditions of each photovoltaic power generation unit in the power station and based on the reactive power reference value of the entire photovoltaic power station, the reactive power reference value of each photovoltaic power generation unit is calculated.

[0044] Furthermore, the reactive power reference value of the entire photovoltaic power station is obtained according to the reactive power command value issued by the grid dispatch and the reactive power measurement value of the grid connection point, including:

[0045] Calculating the difference between the reactive power command value and the reactive power measurement value of the photovoltaic power station grid connection point after first-order filtering, and determining whether the difference exceeds a set reactive power regulation control dead zone;

[0046] When the difference exceeds the set reactive power regulation control dead zone, the difference is passed through the PI regulator and the lead-lag link to obtain the reactive power reference value of the entire photovoltaic power station;

[0047] When the difference does not exceed the set reactive power regulation control dead zone, the reactive power reference value of the entire photovoltaic power station is equal to the current reactive power output of the photovoltaic power station.

[0048] Furthermore, the reactive power reference value of the entire photovoltaic power station is calculated based on the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, and the grid connection point voltage value, including:

[0049] Calculating a reference voltage value of the photovoltaic power station grid connection point after taking into account the voltage drop of the transmission line based on the node voltage amplitude and the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point;

[0050] Calculating the difference between the grid connection point voltage reference value after first-order filtering and the node voltage amplitude, and determining whether the difference exceeds a set reactive power regulation control dead zone;

[0051] When the difference exceeds the set reactive power regulation control dead zone, the difference is passed through the PI regulator and the lead-lag control link to obtain the reactive power reference value of the entire photovoltaic power station;

[0052] When the difference does not exceed the set reactive power regulation control dead zone, the reactive power reference value of the entire photovoltaic power station is equal to the current reactive power output of the photovoltaic power station.

[0053] Furthermore, the calculation formula of the grid-connected point voltage reference value of the photovoltaic power station is as follows:

[0054] V comp =|V reg -(R c +jX c )×I branch |

[0055] Among them, V comp is the reference voltage value of the photovoltaic power station grid connection point, V reg is the node voltage amplitude, R c is the output line resistance, X c is the output line reactance, I branch is the current amplitude of the transmission line between the node and the grid-connected point of the photovoltaic power station, and j is the imaginary unit of the line impedance.

[0056] Furthermore, the photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal, including:

[0057] Determine the active / reactive power control priority of the photovoltaic power station based on the active / reactive priority signal quantity, calculate the maximum and minimum active / reactive current values, and obtain the active / reactive current limit range;

[0058] The active / reactive power reference value is divided by the filtered photovoltaic inverter terminal voltage value after a delay control link to obtain the active / reactive current signal;

[0059] determining whether the active / reactive current signal is within the active / reactive current limit range, and when the active / reactive current signal is within the active / reactive current limit range, setting the active / reactive current reference value to be equal to the active / reactive current signal;

[0060] Otherwise, the active / reactive current signal is subjected to current limiting control to output the maximum / minimum active / reactive current value as the active / reactive current reference value.

[0061] Furthermore, the maximum and minimum active / reactive currents are calculated as follows:

[0062]

[0063]

[0064] Among them, I pmax is the maximum active current, I pmin is the minimum active current, I qmax is the maximum reactive current, I qmin is the minimum value of reactive current, I max is the maximum apparent current, I pcmd0 is the active current signal, I qcmd0 is the reactive current signal, and Pqflag is the active / reactive priority signal.

[0065] Furthermore, the photovoltaic inverter grid interface module adjusts the active / reactive output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value, including:

[0066] Inputting the active / reactive current reference value into the photovoltaic inverter grid interface module after passing through a delay control link;

[0067] The controllable AC current source in the photovoltaic inverter grid interface module outputs active / reactive current values ​​to the grid according to the delayed active / reactive current reference values.

[0068] A photovoltaic power station power control system, the system comprising:

[0069] The photovoltaic power station power control module is used to bring the grid connection point signal and control parameters into the pre-built photovoltaic power station power control model to adjust the active / reactive current output value of the photovoltaic power station;

[0070] The regulating module is used to control the active / reactive frequency of the photovoltaic power station grid connection point to the grid dispatching set value based on the active / reactive current output value of the photovoltaic power station.

[0071] The photovoltaic power station power control module includes a station-level active power control unit, a station-level reactive power control unit, a photovoltaic inverter control unit, and a photovoltaic inverter grid interface unit:

[0072] The station-level active power control unit is used to calculate the active / reactive power reference value that the photovoltaic power generation unit of the photovoltaic power station needs to output based on the system frequency measurement value, the active power control instruction issued by the grid dispatch, the auxiliary frequency control signal and the system frequency setting value;

[0073] The station-level reactive power control unit is used to calculate the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher and the actual grid operation status signal;

[0074] The photovoltaic inverter control unit is configured to calculate, based on the active / reactive power reference value, the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter;

[0075] The photovoltaic inverter grid interface unit is used to adjust the active / reactive output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] The present invention provides a photovoltaic power station power control method suitable for slow regulation with a dynamic adjustment process time scale of approximately seconds to minutes. The method incorporates grid connection point signals and control parameters into a pre-built photovoltaic power station power control model to adjust the active / reactive current output values ​​of the photovoltaic power station. Based on the active / reactive current output values ​​of the photovoltaic power station, the active / reactive frequency at the photovoltaic power station grid connection point is controlled to the grid dispatch setpoint. The technical solution provided by the present invention designs a photovoltaic power station active / reactive control structure comprising three components: a site-level active / reactive control module, a photovoltaic inverter control module, and a photovoltaic inverter network interface module. This structure responds to grid dispatch instructions to change the active / reactive power of the photovoltaic power generation units to the setpoints.

[0078] The technical solution provided by the present invention determines the working mode of active / reactive control by setting different control parameters, namely the auxiliary frequency control signal, the actual grid operation signal and the active / reactive priority signal to 1 or 0. This can accurately reflect the active / reactive operation dynamics of photovoltaic power stations of different types and sizes connected to the grid, making the model highly adaptable.

[0079] The technical solution provided by the present invention is universal, and its model structure can be easily extended to the active / reactive power control system of renewable energy grid-connected systems such as wind farms, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 This is a flow chart of a photovoltaic power station power control method of the present invention;

[0081] Figure 2 A structural diagram of a photovoltaic power station power control method and system according to an embodiment of the present invention;

[0082] Figure 3 Schematic diagram of a station-level active / reactive power control module in an embodiment of the present invention;

[0083] Figure 4 Schematic diagram of a photovoltaic inverter control module according to an embodiment of the present invention;

[0084] Figure 5 Schematic diagram of a photovoltaic inverter grid interface control module according to an embodiment of the present invention;

[0085] Figure 6 Schematic diagram of a photovoltaic power station connected to a power grid model in an embodiment of the present invention;

[0086] Figure 7 The active power dispatch command value curve and the active power measurement value curve of the photovoltaic power station grid connection point in the embodiment of the present invention are shown;

[0087] Figure 8 A graph showing reactive power dispatch command value curve and reactive power measurement value curve of a photovoltaic power station grid connection point in an embodiment of the present invention;

[0088] Figure 9 The figure is a schematic structural diagram of a photovoltaic power station power control system according to the present invention. DETAILED DESCRIPTION

[0089] In order to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and examples. Obviously, the embodiments described are only part of the embodiments of the present invention, but not all of them.

[0090] Example 1:

[0091] The embodiment of the present invention provides a photovoltaic power station power control method, which is suitable for slow adjustment with a time scale of about seconds to minutes during the entire dynamic adjustment process. The specific implementation process is as follows: Figure 1 Shown, including:

[0092] S101: Submit the grid connection point signal and control parameters into the pre-built photovoltaic power plant power control model to adjust the active / reactive current output value of the photovoltaic power plant;

[0093] S102: Based on the active / reactive current output value of the photovoltaic power station, controlling the active / reactive frequency of the photovoltaic power station grid connection point to a grid dispatching set value.

[0094] Specifically, step S101 is to bring the grid connection point signal and control parameters into the pre-built photovoltaic power station power control model to adjust the active / reactive current output value of the photovoltaic power station, including:

[0095] Step S101-1: Establishing a photovoltaic power station power control model, specifically including:

[0096] Step S101-1-1: Based on the interaction of power and current between the photovoltaic power station and the power grid, the photovoltaic power station model is divided into a site-level active / reactive power control module, a photovoltaic inverter control module, and a photovoltaic inverter grid interface module;

[0097] The model is suitable for the steady-state operation of the power system. dip and high voltage setting value V up When the voltage at the grid-connected point of the photovoltaic power station is lower than the low voltage setting value V dip When the PV power station is operating in low voltage ride-through mode, the PV power station is said to be operating in low voltage ride-through mode. When the grid voltage of the PV power station is higher than the high voltage setting V up When the PV power station is operating in high voltage ride-through mode, both high and low voltage ride-through modes of the PV power station are transient operating conditions. The PV power station model involved in this invention does not cover transient operating conditions.

[0098] Step S101-1-2: The station-level active / reactive power control module includes: a station-level active power control module and a station-level reactive power control module:

[0099] The station-level active power control module includes first-order filtering, delay control, auxiliary frequency control and active power control PI regulator with set adjustment parameters;

[0100] The station-level reactive power control module includes first-order filtering, line compensation, reactive power limiting, lead-lag control, and a reactive power control PI regulator with set adjustment parameters;

[0101] Step S101-1-3, the photovoltaic inverter control module includes delay control and current limit control;

[0102] Step S101-1-4, the photovoltaic inverter grid interface module includes a delay control and a controlled AC current source;

[0103] Step S101-2: The station-level active power control module calculates the active power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station based on the system frequency measurement value, the active power control instruction issued by the grid dispatcher, the auxiliary frequency control signal, and the system frequency setting value. Specifically, the step includes:

[0104] Step S101-2-1, judging whether the station-level active power control module operates in a constant active power mode or a frequency modulation control mode according to the value of the auxiliary frequency control signal;

[0105] Among them, the auxiliary frequency control signal is a Boolean quantity with a value of 1 or 0;

[0106] When the auxiliary frequency control signal value is 1, the station-level active power control works in the constant active power mode; when the auxiliary frequency control signal value is 0, the station-level active power control works in the frequency modulation control mode;

[0107] Step S101-2-2: When the station-level active power control module operates in the constant active power mode, the active power reference value of the entire photovoltaic power station is equal to the active power command value issued by the grid dispatcher;

[0108] Step S101-2-3, when the station-level active power control module operates in the frequency modulation control mode, obtains a frequency adjustment reference value based on the system frequency measurement value and the set system frequency value, specifically including:

[0109] Step S101-2-3-1, calculating the difference between the system frequency measurement value and the set system frequency value, and comparing the difference with the set over-frequency action threshold and under-frequency action threshold;

[0110] Step S101-2-3-2: When the frequency difference is greater than the set overfrequency action threshold, multiply the frequency difference by the set overfrequency frequency modulation coefficient to obtain a frequency adjustment reference value; when the frequency difference is greater than the set underfrequency action threshold, multiply the frequency difference by the set underfrequency frequency modulation coefficient to obtain a frequency adjustment reference value;

[0111] Step S101-2-3-3: Use the frequency adjustment reference value as an additional control signal, and combine it with the active power command value issued by the grid dispatcher through the PI regulator and delay control link to obtain the active power reference value of the entire photovoltaic power station;

[0112] Step S101-2-4, calculating the active power reference value of each photovoltaic power generation unit based on the operating conditions of each photovoltaic power generation unit in the power station and the active power reference value of the entire photovoltaic power station;

[0113] Step S101-3: The station-level reactive power control module calculates the reactive power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher, and the actual grid operation status signal. Specifically, the calculation includes:

[0114] Step S101-3-1, judging whether the station-level reactive power control module operates in a constant reactive power control mode or a constant voltage control mode according to the actual operation signal value of the power grid;

[0115] Among them, the actual operation status signal of the power grid is a Boolean quantity with a value of 1 or 0;

[0116] When the actual operation status signal value of the power grid is 1, the station-level reactive power control works in the constant reactive power control mode; when the actual operation status signal value of the power grid is 0, the station-level reactive power control works in the constant voltage control mode;

[0117] Step S101-3-2, when the station-level reactive power control module operates in constant reactive power control mode, obtains the reactive power reference value of the entire photovoltaic power station based on the reactive power command value issued by the grid dispatcher and the reactive power measurement value of the grid connection point; specifically includes:

[0118] Step S101-3-2-1, calculate the difference between the reactive power command value and the reactive power measurement value of the photovoltaic power station grid connection point after first-order filtering, and determine whether the difference exceeds the set reactive power regulation control dead zone;

[0119] Step S101-3-2-2: When the difference exceeds the set reactive power regulation control dead zone, the difference is passed through the PI regulator and the lead-lag link to obtain the reactive power reference value of the entire photovoltaic power station;

[0120] Step S101-3-2-3: when the difference does not exceed the set reactive power regulation control dead zone, the reactive power reference value of the entire photovoltaic power station is equal to the current reactive power output of the photovoltaic power station;

[0121] Step S101-3-3: When the station-level reactive power control module operates in the constant voltage control mode, the reactive power reference value of the entire photovoltaic power station is calculated based on the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, and the grid connection point voltage value, specifically including:

[0122] Step S101-3-3-1, calculating a reference voltage value of the photovoltaic power station grid connection point after taking into account the voltage drop of the transmission line based on the node voltage amplitude and the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point;

[0123] The calculation formula for the voltage reference value of the grid connection point of a photovoltaic power station is as follows:

[0124] V comp =|V reg -(R c +jx c )XI branch |

[0125] Among them, V comp is the reference voltage value of the photovoltaic power station grid connection point, V reg is the node voltage amplitude, R c is the output line resistance, X c is the output line reactance, I branch is the current amplitude of the transmission line between the node and the grid-connected point of the photovoltaic power station, and j is the imaginary unit of the line impedance;

[0126] Step S101-3-3-2, calculating the difference between the grid connection point voltage reference value after first-order filtering and the node voltage amplitude, and determining whether the difference exceeds the set reactive power regulation control dead zone;

[0127] Step S101-3-3-3: When the difference exceeds the set reactive power regulation control dead zone, the difference is passed through the PI regulator and the lead-lag control link to obtain the reactive power reference value of the entire photovoltaic power station;

[0128] Step S101-3-3-4: when the difference does not exceed the set reactive power regulation control dead zone, the reactive power reference value of the entire photovoltaic power station is equal to the current reactive power output of the photovoltaic power station;

[0129] Step S101-4: The photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal, specifically including:

[0130] Step S101-4-1: the active / reactive power reference value is divided by the filtered photovoltaic inverter terminal voltage value after a delay control link to obtain the active / reactive current signal;

[0131] Step S101-4-2, calculating the maximum and minimum active / reactive current values ​​based on the active / reactive priority signal quantity to obtain the active / reactive current limit range;

[0132] The calculation formula for the maximum and minimum active / reactive current is as follows:

[0133]

[0134]

[0135] Among them, I pmax is the maximum active current, I pmin is the minimum active current, I qmax is the maximum reactive current, I qmin is the minimum value of reactive current, I max is the maximum apparent current, I pcmd0 is the active current signal, I qcmd0 is the reactive current signal, and Pqflag is the active / reactive priority signal.

[0136] Step S101-4-3, determining whether the active / reactive current signal is within the active / reactive current limit range. If the active / reactive current signal is within the active / reactive current limit range, the active / reactive current reference value is equal to the active / reactive current signal. Otherwise, the active / reactive current signal is subjected to current limiting control and the maximum / minimum active / reactive current value is output as the active / reactive current reference value.

[0137] Step S101-5: The photovoltaic inverter grid interface module adjusts the active / reactive output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value, specifically including:

[0138] Step S101-5-1, inputting the active / reactive current reference value into the grid interface module of the photovoltaic inverter after passing through a delay control link;

[0139] Step S101 - 5 - 2 : The controllable AC current source in the grid interface module of the photovoltaic inverter outputs the active / reactive current value to the grid according to the delayed active / reactive current reference value.

[0140] Example 2:

[0141] Existing standards for photovoltaic grid-connected operation, such as the industry standard GB 19964-2012 "Technical Regulations for the Connection of Photovoltaic Power Stations to the Power System" that must be met in China, clearly stipulate that photovoltaic power stations must have active / reactive power control functions and adjust the power output of the photovoltaic power station grid connection point according to real-time or pre-set control instructions issued by the grid dispatcher. The entire dynamic adjustment process takes approximately seconds to minutes, which is a slow regulation process.

[0142] The embodiment of the present invention abstracts the model into three sub-modules based on the modular design concept: station-level active / reactive power control system, photovoltaic inverter control and photovoltaic inverter network interface. Figure 2 Shown, including:

[0143] (1) The station-level active / reactive power control module can calculate the active / reactive power that the photovoltaic power station needs to inject into the grid under the current operating state according to the active / reactive power control instructions issued by the grid dispatcher.

[0144] (2) The photovoltaic inverter control module receives the photovoltaic inverter active / reactive power command value signal output by the station-level active / reactive power control module, obtains the photovoltaic inverter active / reactive current reference value through calculation, and sends it to the photovoltaic inverter grid interface control module.

[0145] (3) The photovoltaic inverter grid interface module uses a controlled current source as the interface between the photovoltaic power generation unit and the grid. By controlling the active / reactive output value of the AC current source, the active / reactive power of the photovoltaic power generation unit is changed to the set value.

[0146] Specifically, the structure and implementation of each submodule are as follows:

[0147] The station-level active / reactive power control module not only has the function of responding to the active power control command issued by the grid dispatcher, but also has the function of responding to the grid frequency regulation. req_flag Determine whether to add an auxiliary frequency control link. The additional frequency control link compares the system frequency measurement value F req With the set value F req_ref If the frequency difference exceeds the over-frequency action threshold fdbd1, the frequency modulation controller will be activated and the frequency deviation signal will be multiplied by the frequency modulation coefficient (over-frequency) D. up Get the frequency adjustment reference signal; (2) If the frequency difference exceeds the underfrequency action threshold fdbd2, the frequency modulation controller will act and multiply the frequency deviation signal by the frequency modulation coefficient (underfrequency) D dn Then, the frequency regulation reference signal is used as an additional control signal and acts together with the active power setting value plant_ref issued by the dispatcher in the active control link, and the final active power reference value signal P of the photovoltaic power station is obtained through the PI regulator. ref If the active power control of the photovoltaic power station does not include the frequency control function, the active power setting value plant_ref issued by the dispatcher is the active power reference value P of the photovoltaic power station. ref (like Figure 3 ).

[0148] Over-frequency / under-frequency action thresholds fdbd1 and fdbd2 of the station-level active power control system module, and PI regulator parameter K pg (proportional coefficient), K ig (integral coefficient) and other parameters can be adjusted according to the actual operating conditions of the photovoltaic power station.

[0149] The reactive power control object at the station level can be the reactive power instruction issued by the dispatcher (reactive power control mode), or it can be the voltage of a node in the system set in advance (constant voltage control mode). The control mode is determined by the signal quantity R according to the actual operation of the power grid. ref_flag Sure.

[0150] If the station-level reactive power control adopts the constant voltage control mode, the input signal is the set node voltage amplitude V reg And the current value I of the transmission line between this node and the photovoltaic power station grid connection point branch , and the voltage reference value of the photovoltaic power station grid connection point after taking into account the voltage drop of the transmission line can be calculated according to the following formula:

[0151] V comp =|V reg -(R c +jX c )XI branch |

[0152] Among them, V comp is the reference voltage value of the photovoltaic power station grid connection point, V reg is the node voltage amplitude, R c is the output line resistance, X c is the output line reactance, I branch It is the current amplitude of the line connecting the node and the photovoltaic power station.

[0153] Grid connection point voltage reference value signal V comp After the first-order filtering link and the grid voltage value V reg Perform difference comparison. If the voltage difference exceeds the reactive power regulation control dead zone dbd, the difference signal is passed through the PI control link and the lead-lag link to obtain the photovoltaic inverter reactive power reference value Q ext .

[0154] If the reactive power control mode is adopted for the station-level reactive power control, if the reactive power command value Q ref The reactive power measurement value Q of the photovoltaic power station grid connection point after filtering branch If the difference exceeds the reactive power regulation dead zone, the difference signal is converted into the reactive power reference value Q of the photovoltaic inverter through the PI control link and the lead-lag link. ext .

[0155] The photovoltaic inverter control module receives the active / reactive power reference value signal issued by the station-level active / reactive power control module through the corresponding control link, and obtains the active / reactive current reference value signal through calculation through the relevant control link.

[0156] The method for obtaining the active current reference value signal of the photovoltaic inverter in the photovoltaic inverter control module is as follows: the input station-level active power reference value signal P ref After a delay link, it is divided by the filtered photovoltaic inverter terminal voltage value V t-filt , calculate and judge whether the obtained signal quantity is within the reactive current limit range [I pmin ,I pmax ], the current reference value signal I is obtained after the limit link pcmd (like Figure 4 The active power output of the photovoltaic inverter is limited by the rated capacity of the inverter, ensuring that the active power output is within the normal power operating range [P min ,P max ], and in order to avoid "climbing events", it is also necessary to set the active power increase / decrease rate limit dP max / dP min Specific parameter settings can be set according to the actual operation of the photovoltaic power station while meeting the requirements of industry standards. For example, the industry standard that needs to be met in China can be the national standard 19964-2012 "Technical Regulations for Photovoltaic Power Stations Connected to the Power System".

[0157] The method for obtaining the reactive current reference value signal of the photovoltaic inverter in the photovoltaic inverter control module is as follows: the input station-level reactive power reference value signal Q ext After a delay link, it is divided by the filtered photovoltaic inverter terminal voltage value V t-filt , calculate and judge whether the obtained signal quantity is within the reactive current limit range [I qmin ,I qmax ], the current reference value signal I is obtained after the limit link qcmd ,like Figure 4 shown.

[0158] Photovoltaic power stations need to determine the current active / reactive power control priority according to the scheduling requirements. When the specific model is implemented, the active / reactive priority is determined by setting the active / reactive priority signal Pqflag, and the active / reactive current maximum value I is determined. pmax , I qmax and minimum value I pmin , I qmin .

[0159] If reactive power priority is used (Pqflag = 0), the maximum active / reactive current is calculated as follows:

[0160]

[0161] Among them, I max is the maximum apparent current.

[0162] If active power priority is used (Pqflag = 1), the maximum active / reactive current is calculated as follows:

[0163]

[0164] The grid interface layer of the photovoltaic inverter uses a controlled current source as the interface between the photovoltaic power generation unit and the grid, and converts the active / reactive current reference value I output by the photovoltaic inverter control layer into pcmd / I qcmd The active / reactive current value of the AC current source is adjusted according to the active / reactive current reference value, and the active / reactive power output value of the photovoltaic power generation unit is finally changed (such as Figure 5 ). Delay link time constant T g It can be set according to the actual operating performance of the inverter, and the grid interface layer can use the controlled current source model that comes with the simulation platform.

[0165] Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 The circuit parameters that appear in are as follows:

[0166] V reg is the grid connection point voltage value obtained by power flow calculation; Q ref is the reactive power command value; V ref is the grid connection point voltage value; P ref is the active power reference value; P branch F is the measured value of active power at the grid connection point; req_ref is the system frequency setting value; F req is the system frequency measurement value; Q ext is the reactive power reference value; P ref is the active power reference value; I qcmd is the reactive current reference value; I pcmd is the active current reference value; I qw is the reactive current value; I p is the active current value;

[0167] plant_ref is the active power setting value issued by the dispatcher; F req_flag P is the auxiliary frequency control signal (0-exit, 1-input); min is the minimum active power; P max is the maximum active power; T p Active power measurement delay; T lag K is the active power control delay; pg , K ig D is the active power control PI adjustment parameter; dn To adjust the FM control gain; D upis the FM control gain for downward adjustment; fdbd is the FM control action dead zone;

[0168] I branch The output line current value of the photovoltaic power station; Q branch is the reactive power measurement value of the grid connection point; R ref_flag is the signal quantity of the actual operation status of the power grid; Q min is the minimum value of reactive power; Q max is the maximum reactive power; K p , K i is the reactive power control PI adjustment parameter; dbd is the reactive power control dead zone; R c 、X c is the line impedance; T fltr T is the filter delay of reactive power control link; ft 、T fv is the time constant of the lead-lag link of reactive power control;

[0169] T pord is the active power control delay parameter; T iq is the reactive power control delay parameter; dP max is the maximum value of active power change rate; dP min is the minimum value of the active power change rate; I pmax is the maximum active current; I pmin is the minimum value of active current; I max is the maximum current; Pqflag is the active / reactive priority signal; T iq Reactive power control delay; I qmax is the maximum value of reactive current; I qmin is the minimum value of reactive current; I pcmd is the active current reference value; I qcmd is the reactive current reference value; V t-filt is the voltage value of the photovoltaic inverter terminal; T g Controls delay parameters for the grid interface.

[0170] Taking the PowerFactory platform as an example, the method proposed in this invention is used to establish a photovoltaic power station model. By changing the active power and reactive power command value signals issued by the grid dispatch, the active power and reactive power output of the photovoltaic power station grid connection point are observed to see whether they can accurately respond to the grid dispatch command, so as to verify the accuracy of the established model.

[0171] During the simulation, the photovoltaic power station capacity is set to 50MWp, consisting of 100 photovoltaic inverters with a single unit capacity of 500kW. The photovoltaic power station is connected to the system electrical connection as follows: Figure 6As shown in the figure, the specific simulation model uses the single-machine multiplication method to perform the equivalent, and a photovoltaic inverter model is used to equate to the photovoltaic power station model. The simulation comparison of the active / reactive power command value issued by the dispatcher and the active / reactive power of the photovoltaic power station grid connection point is shown in the figure. Figure 7 , Figure 8 As shown in the figure, when the active / reactive power control instructions of the power grid change, the active / reactive power measurement values ​​at the grid connection point of the photovoltaic power station can accurately track the dispatching instructions, which also verifies the accuracy of the established model.

[0172] Example 3:

[0173] Based on the same inventive concept, the present invention also provides a photovoltaic power station power control system, such as Figure 9 As shown, the system includes:

[0174] The photovoltaic power station power control module is used to bring the grid connection point signal and control parameters into the pre-built photovoltaic power station power control model to adjust the active / reactive current output value of the photovoltaic power station;

[0175] The regulating module is used to control the active / reactive frequency of the photovoltaic power station grid connection point to the grid dispatching set value based on the active / reactive current output value of the photovoltaic power station.

[0176] The photovoltaic power station power control module includes a station-level active power control unit, a station-level reactive power control unit, a photovoltaic inverter control unit, and a photovoltaic inverter grid interface unit:

[0177] The station-level active power control unit is used to calculate the active / reactive power reference value that the photovoltaic power generation unit of the photovoltaic power station needs to output based on the system frequency measurement value, the active power control instruction issued by the grid dispatch, the auxiliary frequency control signal and the system frequency set value;

[0178] The station-level reactive power control unit is used to calculate the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, grid connection point reactive power measurement value, node voltage amplitude, current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, reactive power control instructions issued by the grid dispatcher, and actual grid operation status signals;

[0179] A photovoltaic inverter control unit is used to calculate the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value;

[0180] The photovoltaic inverter grid interface unit is used to adjust the active / reactive output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value.

[0181] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0182] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes 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 produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. 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.

[0183] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0184] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0185] The above are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of the claims of the present invention to be approved.

Claims

1. A photovoltaic power station power control method, characterized in that: include: The grid connection point signal and control parameters are introduced into the pre-built PV power plant power control model to adjust the active / reactive current output value of the PV power plant; Based on the active / reactive current output value of the photovoltaic power station, controlling the active / reactive frequency of the photovoltaic power station grid connection point to the grid dispatch set value; The photovoltaic power station power control model includes: a station-level active / reactive power control module, a photovoltaic inverter control module and a photovoltaic inverter grid interface module; The control parameters include: active / reactive power control instructions issued by the grid dispatcher, auxiliary frequency control signals, actual grid operation status signals, PI regulator parameters of the station-level active / reactive power control module, system frequency setpoints, and active / reactive power priority signals; The grid connection point signal includes: grid connection point voltage value, grid connection point reactive power measurement value, system frequency measurement value, node voltage amplitude and current amplitude of the node and photovoltaic power station grid connection point output line; The step of introducing the grid connection point signal and control parameters into a pre-built photovoltaic power plant power control model to adjust the active / reactive current output value of the photovoltaic power plant includes: The station-level active / reactive power control module calculates the active / reactive power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station according to the grid connection point signal and the control parameters; the photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal; The photovoltaic inverter grid interface module adjusts the active / reactive current output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value; The photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal, including: Determine the active / reactive power control priority of the photovoltaic power station based on the active / reactive priority signal quantity, calculate the maximum and minimum active / reactive current values, and obtain the active / reactive current limit range; The active / reactive power reference value is divided by the filtered photovoltaic inverter terminal voltage value after a delay control link to obtain the active / reactive current signal; determining whether the active / reactive current signal is within the active / reactive current limit range, and when the active / reactive current signal is within the active / reactive current limit range, setting the active / reactive current reference value to be equal to the active / reactive current signal; Otherwise, the active / reactive current signal is subjected to current limiting control to output the maximum / minimum active / reactive current value as the active / reactive current reference value.

2. The photovoltaic power station power control method according to claim 1, wherein: The photovoltaic power station power control model includes: Station-level active / reactive power control module, photovoltaic inverter control module and photovoltaic inverter grid interface module; The station-level active / reactive power control module includes: a station-level active power control module and a station-level reactive power control module; The station-level active power control module includes: first-order filtering, delay control, auxiliary frequency control and active power control PI regulator with set adjustment parameters; The station-level reactive power control module includes: first-order filtering, line compensation, reactive power limiting, lead-lag control and reactive power control PI regulator with set adjustment parameters; The photovoltaic inverter control module includes: delay control and current limit control; The photovoltaic inverter grid interface module includes: a delay control and a controlled AC current source.

3. The photovoltaic power station power control method according to claim 2, wherein: The station-level active / reactive power control module calculates the active / reactive power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station based on the grid connection point signal and control parameters, including: The station-level active power control module calculates the active power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the system frequency measurement value, the active power control instruction issued by the grid dispatcher, the auxiliary frequency control signal and the system frequency setting value; The station-level reactive power control module calculates the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher and the actual operation status signal of the grid.

4. The photovoltaic power station power control method according to claim 3, wherein: The station-level active power control module calculates the active power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station based on the system frequency measurement value, the active power control instruction issued by the grid dispatcher, the auxiliary frequency control signal and the system frequency setting value, including: Determining whether the station-level active power control module operates in a constant active power mode or a frequency modulation control mode according to the auxiliary frequency control signal value; When the station-level active power control module operates in the constant active power mode, the active power reference value of the entire photovoltaic power station is equal to the active power command value issued by the grid dispatcher; When the station-level active power control module operates in frequency modulation control mode, the active power reference value of the entire photovoltaic power station is calculated based on the system frequency measurement value, the system frequency setting value and the active power command value issued by the grid dispatcher; According to the operating conditions of each photovoltaic power generation unit in the power station, the active power reference value of each photovoltaic power generation unit is calculated based on the active power reference value of the entire photovoltaic power station.

5. The photovoltaic power station power control method according to claim 4, characterized in that: The active power reference value of the entire photovoltaic power station is calculated based on the system frequency measurement value, the system frequency setting value and the active power command value issued by the grid dispatcher, including: Obtain a frequency adjustment reference value based on the system frequency measurement value and the set system frequency value; The frequency adjustment reference value is used as an additional control signal, and together with the active power command value issued by the grid dispatcher, the active power reference value of the entire photovoltaic power station is obtained through the PI regulator and the delay control link.

6. The photovoltaic power station power control method according to claim 5, characterized in that: Obtaining a frequency adjustment reference value based on a system frequency measurement value and a set system frequency value includes: Calculating a frequency difference between a system frequency measurement value and a set system frequency value, and comparing the frequency difference with a set overfrequency action threshold and an underfrequency action threshold; When the frequency difference is greater than the set over-frequency action threshold, the frequency difference is multiplied by the set over-frequency frequency modulation coefficient to obtain a frequency adjustment reference value; When the frequency difference is greater than the set underfrequency action threshold, the frequency difference is multiplied by the set underfrequency frequency modulation coefficient to obtain a frequency adjustment reference value.

7. The photovoltaic power station power control method according to claim 3, wherein: The station-level reactive power control module calculates the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher, and the actual grid operation status signal, including: Determining whether the station-level reactive power control module operates in a constant reactive power control mode or a constant voltage control mode according to the actual operation status signal value of the power grid; When the station-level reactive power control module operates in a constant reactive power control mode, a reactive power reference value of the entire photovoltaic power station is obtained according to the reactive power command value issued by the grid dispatcher and the reactive power measurement value of the grid connection point; When the station-level reactive power control module operates in a constant voltage control mode, the reactive power reference value of the entire photovoltaic power station is calculated based on the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, and the grid connection point voltage value; According to the operating conditions of each photovoltaic power generation unit in the power station and based on the reactive power reference value of the entire photovoltaic power station, the reactive power reference value of each photovoltaic power generation unit is calculated.

8. The photovoltaic power station power control method according to claim 7, wherein: The reactive power reference value of the entire photovoltaic power station is obtained according to the reactive power command value issued by the grid dispatch and the reactive power measurement value of the grid connection point, including: Calculating the power difference between the reactive power command value and the reactive power measurement value of the photovoltaic power station grid connection point after first-order filtering, and determining whether the power difference exceeds a set reactive power regulation control dead zone; When the power difference exceeds the set reactive power regulation control dead zone, the power difference is passed through the PI regulator and the lead-lag link to obtain the reactive power reference value of the entire photovoltaic power station; When the power difference does not exceed the set reactive power regulation control dead zone, the reactive power reference value of the entire photovoltaic power station is equal to the current reactive power output of the photovoltaic power station.

9. The photovoltaic power station power control method according to claim 7, wherein: The reactive power reference value of the entire photovoltaic power station is calculated based on the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, and the grid connection point voltage value, including: Calculating a reference voltage value of the photovoltaic power station grid connection point after taking into account the voltage drop of the transmission line based on the node voltage amplitude and the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point; Calculating a voltage difference between the grid connection point voltage reference value after first-order filtering and the node voltage amplitude, and determining whether the voltage difference exceeds a set reactive power regulation control dead zone; When the voltage difference exceeds the set reactive power regulation control dead zone, the voltage difference is passed through the PI regulator and the lead-lag control link to obtain the reactive power reference value of the entire photovoltaic power station; When the voltage difference does not exceed the set reactive power regulation control dead zone, the reactive power reference value of the entire photovoltaic power station is equal to the current reactive power output of the photovoltaic power station.

10. The photovoltaic power station power control method according to claim 9, characterized in that: The calculation formula of the voltage reference value of the photovoltaic power station grid connection point is as follows: V comp =|V reg -(R c +jX c )×I branch | Among them, V comp is the reference voltage value of the photovoltaic power station grid connection point, V reg is the node voltage amplitude, R c is the output line resistance, X c is the output line reactance, I branch is the current amplitude of the transmission line between the node and the grid-connected point of the photovoltaic power station, and j is the imaginary unit of the line impedance.

11. The photovoltaic power station power control method according to claim 1, wherein: The maximum and minimum active / reactive current values ​​are calculated as follows: Among them, I pmax is the maximum active current, I pmin is the minimum active current, I qmax is the maximum reactive current, I qmin is the minimum value of reactive current, I max is the maximum apparent current, I pcmd0 is the active current signal, I qcmd0 is the reactive current signal, and Pqflag is the active / reactive priority signal.

12. The photovoltaic power station power control method according to claim 1, wherein: The photovoltaic inverter grid interface module adjusts the active / reactive output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value, including: Inputting the active / reactive current reference value into the photovoltaic inverter grid interface module after passing through a delay control link; The controllable AC current source in the photovoltaic inverter grid interface module outputs active / reactive current values ​​to the grid according to the delayed active / reactive current reference values.

13. A photovoltaic power station power control system, characterized in that: include: The photovoltaic power station power control module is used to bring the grid connection point signal and control parameters into the pre-built photovoltaic power station power control model to adjust the active / reactive current output value of the photovoltaic power station; A regulating module, configured to control the active / reactive frequency of the photovoltaic power station grid connection point to a grid dispatching set value based on the active / reactive current output value of the photovoltaic power station; The photovoltaic power station power control module includes: a station-level active / reactive power control module, a photovoltaic inverter control module and a photovoltaic inverter grid interface module; The control parameters include: active / reactive power control instructions issued by the grid dispatcher, auxiliary frequency control signals, actual grid operation status signals, PI regulator parameters of the station-level active / reactive power control module, system frequency setpoints, and active / reactive power priority signals; The grid connection point signal includes: grid connection point voltage value, grid connection point reactive power measurement value, system frequency measurement value, node voltage amplitude and current amplitude of the node and photovoltaic power station grid connection point output line; The step of introducing the grid connection point signal and control parameters into a pre-built photovoltaic power plant power control model to adjust the active / reactive current output value of the photovoltaic power plant includes: The station-level active / reactive power control module calculates the active / reactive power reference value required to be output by each photovoltaic power generation unit of the photovoltaic power station according to the grid connection point signal and the control parameters; the photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal; The photovoltaic inverter grid interface module adjusts the active / reactive current output value of the controllable AC current source connecting each photovoltaic power generation unit and the grid according to the active / reactive current reference value; The photovoltaic inverter control module calculates the active / reactive current reference value of each photovoltaic power generation unit corresponding to each photovoltaic inverter based on the active / reactive power reference value and the active / reactive priority signal, including: Determine the active / reactive power control priority of the photovoltaic power station based on the active / reactive priority signal quantity, calculate the maximum and minimum active / reactive current values, and obtain the active / reactive current limit range; The active / reactive power reference value is divided by the filtered photovoltaic inverter terminal voltage value after a delay control link to obtain the active / reactive current signal; determining whether the active / reactive current signal is within the active / reactive current limit range, and when the active / reactive current signal is within the active / reactive current limit range, setting the active / reactive current reference value to be equal to the active / reactive current signal; Otherwise, the active / reactive current signal is subjected to current limiting control to output the maximum / minimum active / reactive current value as the active / reactive current reference value.

14. The photovoltaic power station power control system according to claim 13, wherein: The station-level active / reactive power control module includes a station-level active power control module and a station-level reactive power control module: The station-level active power control module is used to calculate the active power reference value that the photovoltaic power generation unit of the photovoltaic power station needs to output based on the system frequency measurement value, the active power control instruction issued by the grid dispatch, the auxiliary frequency control signal and the system frequency setting value; The station-level reactive power control module is used to calculate the reactive power reference value that each photovoltaic power generation unit of the photovoltaic power station needs to output based on the grid connection point voltage value, the grid connection point reactive power measurement value, the node voltage amplitude, the current amplitude of the transmission line between the node and the photovoltaic power station grid connection point, the reactive power control instruction issued by the grid dispatcher and the actual operation status signal of the grid.

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