Primary frequency modulation method and device of power system, electronic equipment and storage medium

Abstract

The invention discloses a primary frequency modulation method and device of a power system, electronic equipment and a storage medium, and is used for solving the problems that a sending end and a receiving end of a current flexible direct current system are difficult to mutually acquire actual operation states and a sending end power grid can only indirectly participate in frequency modulation of a receiving end power grid by means of the flexible direct current system. The power system comprises a receiving end converter station, a sending end converter station and an energy storage system. Acquiring an inertia parameter of the power system, a first power operation parameter of a receiving-end converter station and a second power operation parameter of a sending-end converter station; based on the first power operation parameter, determining a direct current voltage reference value of the receiving end converter station under voltage-frequency coupling control; determining a power reference value of the transmitting-end converter station under power-voltage coupling control based on the first power operation parameter and the second power operation parameter; based on the inertia parameter, determining an energy storage output power variation when the energy storage system participates in frequency modulation; and participating in primary frequency modulation of the power system based on the determined parameters to obtain a primary frequency modulation result.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power systems, and in particular to a primary frequency modulation method and device for a power system, an electronic device and a storage medium. BACKGROUND

[0002] Frequency instability poses a significant threat to the safe and stable operation of a power system. Substandard primary frequency modulation performance can lead to deterioration of power quality and even cause the splitting of the power grid, resulting in significant economic losses. With the continued development and utilization of new energy, the proportion of non-synchronous power sources such as wind turbines, photovoltaic devices, flexible direct current transmission stations and energy storage devices is gradually increasing, leading to a decrease in the overall inertia level and frequency modulation capacity of the power grid, seriously threatening the frequency stability of the system. Against this background, the necessity for flexible direct current systems and energy storage to participate in system frequency modulation is increasingly prominent.

[0003] In view of how non-synchronous mechanical power sources participate in grid frequency modulation, current technologies have proposed many effective frequency modulation strategies, including virtual synchronous control and active power-frequency droop control. However, considering the operating constraints of non-synchronous mechanical power sources, the energy and power support that they can provide to the alternating current grid is limited. Depending on the type and physical characteristics, the operating constraints of different types of non-synchronous mechanical power sources are different, resulting in differences in the frequency modulation role that different types of non-synchronous mechanical power sources can play. For example, the pitch angle of a wind turbine moves slowly and is difficult to provide a large amount of power support in a very short time. For another example, the action time of energy storage is fast, but it is limited by the state of charge and is difficult to support the system frequency for a long time.

[0004] In recent years, although there have been many documents discussing the frequency modulation of different non-synchronous mechanical power sources, for flexible direct current systems, the sending end and the receiving end of the grid are decoupled and it is difficult for them to obtain the actual operating state from each other, so the sending end grid can only indirectly participate in the frequency modulation of the receiving end grid with the help of the flexible direct current system. SUMMARY

[0005] The present application provides a primary frequency modulation method and device for a power system, an electronic device and a storage medium, which are used to solve or partially solve the technical problem that the sending end and the receiving end of the current flexible direct current system cannot obtain the actual operating state from each other, and the sending end grid can only indirectly participate in the frequency modulation of the receiving end grid with the help of the flexible direct current system.

[0006] The present application provides a primary frequency modulation method for a power system, the power system comprising a receiving end converter station, a sending end converter station and an energy storage system; the method comprising:

[0007] obtaining inertia parameters of the power system, first power operating parameters of the receiving end converter station and second power operating parameters of the sending end converter station;

[0008] determining a direct current voltage reference value of the receiving end converter station under voltage-frequency coupling control based on the first power operating parameters;

[0009] Based on the first power operation parameters and the second power operation parameters, the power reference value of the sending-end converter station under power-voltage coupling control is determined;

[0010] Based on the inertia parameter, determine the change in energy storage output power when the energy storage system participates in frequency regulation;

[0011] Based on the DC voltage reference value and the power reference value, and / or, the change in the energy storage output power participates in the primary frequency regulation of the power system to obtain the primary frequency regulation result.

[0012] Optionally, the first power operating parameters include lumped capacitance parameters, receiving-end DC voltage, inflow active power, outflow active power, minimum DC voltage, minimum allowable frequency, rated DC voltage, rated frequency, and instantaneous frequency; the step of determining the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control based on the first power operating parameters includes:

[0013] A receiving-end DC voltage model is constructed based on the lumped capacitance parameters, the receiving-end DC voltage, the inflow active power, and the outflow active power.

[0014] Under the condition of satisfying the receiving-end DC voltage model, a model of the maximum energy that the receiving-end converter station can release under the minimum DC voltage is constructed based on the lumped capacitance parameters and the rated DC voltage.

[0015] Considering the voltage-frequency coupling control of the receiving-end converter station, based on the maximum energy model and in combination with the rated frequency and the instantaneous frequency, the DC voltage reference value of the receiving-end converter station at the minimum allowable frequency is solved.

[0016] Optionally, the first power operating parameters include the receiving-end DC voltage, rated DC voltage, and minimum DC voltage; the second power operating parameters include the sending-end DC resistance, sending-end DC current, initial operating power of the wind turbine, and maximum output power of the sending end; determining the power reference value of the sending-end converter station under power-voltage coupling control based on the first power operating parameters and the second power operating parameters includes:

[0017] The DC voltage at the receiving end is determined based on the DC resistance at the sending end and the DC current at the sending end.

[0018] The droop control coefficient is determined based on the initial operating power of the fan, the maximum output power of the feed end, the rated DC voltage, and the minimum DC voltage.

[0019] Based on the initial operating power of the wind turbine, the droop control coefficient, the DC voltage at the sending end, and the rated DC voltage, calculate the power reference value of the sending end converter station under power-voltage coupling control.

[0020] Optionally, the inertia parameters include system inertia and virtual inertia; determining the change in energy storage output power when the energy storage system participates in frequency regulation based on the inertia parameters includes:

[0021] Based on the system inertia and the virtual inertia, considering the system's maximum power deficit and the maximum output power of the energy storage, the energy storage inertia coefficient of the energy storage system is calculated when the power system experiences the maximum rate of frequency change.

[0022] Considering the maximum output power of the energy storage, calculate the energy storage damping coefficient of the energy storage system when the power system experiences the maximum rate of frequency change.

[0023] Based on the energy storage inertia coefficient and the energy storage damping coefficient, the change in energy storage output power when the energy storage system participates in frequency regulation is calculated.

[0024] Optionally, the step of calculating the energy storage inertia coefficient of the energy storage system when the power system experiences its maximum rate of frequency change, based on the system inertia and the virtual inertia, considering the system's maximum power deficit and the maximum output power of the energy storage, includes:

[0025] Based on the system inertia and the virtual inertia, and considering the maximum power deficit of the system, a model of the first maximum frequency change rate when the energy storage system participates in frequency regulation is constructed.

[0026] Based on the first maximum frequency change rate model, and considering the maximum output power of the energy storage, the energy storage inertia coefficient of the power system when the maximum frequency change rate occurs is calculated.

[0027] Optionally, the step of having the energy storage output power change participate in the primary frequency regulation of the power system based on the DC voltage reference value and the power reference value, and / or, includes:

[0028] Based on the inertia parameter, calculate the second maximum frequency change rate when the energy storage system does not participate in frequency regulation;

[0029] Based on the second maximum frequency change rate, determine whether the change in the energy storage output power needs to participate in the primary frequency regulation of the power system;

[0030] If so, then the power system's primary frequency regulation is simultaneously based on the DC voltage reference value, the power reference value, and the change in energy storage output power.

[0031] If not, then the power system will participate in primary frequency regulation based on both the DC voltage reference value and the power reference value.

[0032] Optionally, determining whether the change in energy storage output power needs to participate in the primary frequency regulation of the power system based on the second maximum frequency change rate includes:

[0033] Obtain the first maximum frequency change rate calculated by the energy storage system based on the inertia parameter; the first maximum frequency change rate corresponds to the maximum frequency change rate allowed by the power system;

[0034] Compare the first maximum frequency change rate with the second maximum frequency change rate;

[0035] When the second maximum frequency change rate is greater than or equal to the first maximum frequency change rate, it is determined that the change in the energy storage output power needs to participate in the primary frequency regulation of the power system.

[0036] When the second maximum frequency change rate is less than the first maximum frequency change rate, it is determined that the change in the energy storage output power does not need to participate in the primary frequency regulation of the power system.

[0037] The present invention also provides a primary frequency regulation device for a power system, the power system including a receiving-end converter station, a sending-end converter station, and an energy storage system; the device includes:

[0038] The data acquisition unit is used to acquire the inertia parameters of the power system, the first power operation parameters of the receiving-end converter station, and the second power operation parameters of the sending-end converter station.

[0039] A DC voltage reference value determination unit is used to determine the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control based on the first power operation parameters.

[0040] A power reference value determination unit is used to determine the power reference value of the sending-end converter station under power-voltage coupling control based on the first power operating parameters and the second power operating parameters.

[0041] An energy storage output power change determination unit is used to determine the energy storage output power change when the energy storage system participates in frequency regulation based on the inertia parameter.

[0042] A primary frequency regulation unit is used to participate in the primary frequency regulation of the power system based on the DC voltage reference value, the power reference value, and / or the change in energy storage output power, to obtain the primary frequency regulation result.

[0043] The present invention also provides an electronic device, the device comprising a processor and a memory:

[0044] The memory is used to store program code and transmit the program code to the processor;

[0045] The processor is configured to execute the primary frequency regulation method of the power system as described above, according to the instructions in the program code.

[0046] The present invention also provides a computer-readable storage medium for storing program code for performing a primary frequency regulation method for a power system as described in any of the preceding claims.

[0047] As can be seen from the above technical solutions, the present invention has the following advantages:

[0048] This paper presents a method for primary frequency regulation of a power system. First, the inertia parameters of the power system, the first power operating parameters of the receiving-end converter station, and the second power operating parameters of the sending-end converter station are obtained as basic data for subsequent primary frequency regulation calculations. Next, based on the first power operating parameters, the DC voltage reference value of the receiving-end converter station under voltage-frequency coupled control is determined. This allows for the construction of a DC voltage-frequency coupled control strategy from the receiving-end converter station's perspective, enabling the receiving-end of the flexible DC transmission line to better participate in the system's primary frequency regulation. Then, based on the first and second power operating parameters, the power reference value of the sending-end converter station under power-voltage coupled control is determined. Based on the control strategy of the receiving-end converter station, a power-voltage coupled control strategy is constructed from the sending-end converter station's perspective, enabling the sending-end of the flexible DC transmission line to better participate in the system's primary frequency regulation. Finally, based on the inertia parameters, the change in energy storage output power when the energy storage system participates in frequency regulation is determined. This considers that relying solely on wind turbines and DC systems may be insufficient to meet the frequency support requirements of the AC grid, further considering the possibility of using energy storage to provide frequency regulation support to the AC grid. When frequency regulation relying solely on wind turbines and DC systems cannot meet the system's safety and stability requirements, energy storage provides leveling support to the AC grid, maintaining the system's safe and stable operation. Finally, based on DC voltage and power reference values, and / or changes in energy storage output power, the primary frequency regulation of the power system is achieved, yielding the primary frequency regulation result. Thus, based on three control strategies, appropriate frequency regulation strategies can be selected for different frequency regulation needs, improving the flexibility and selectivity of primary frequency regulation and enhancing its effectiveness. By adopting appropriate frequency regulation strategies, system frequency stability can be effectively improved. The technical solution provided by this invention, by effectively utilizing the frequency regulation potential of flexible DC systems and energy storage systems, can provide a reference for the operation of new energy power systems, ensuring their safe and stable operation. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 A flowchart illustrating the steps of a primary frequency regulation method for a power system;

[0051] Figure 2 A schematic diagram of the overall process of a primary frequency regulation method for a power system;

[0052] Figure 3 Example diagram of modified IEEE 39-node system network topology;

[0053] Figure 4 Example graphs of system frequency response curves before and after the participation of flexible DC and energy storage in frequency regulation;

[0054] Figure 5 This is a structural block diagram of a primary frequency regulation device for a power system. Detailed Implementation

[0055] This invention provides a primary frequency regulation method, apparatus, electronic device, and storage medium for a power system, which solves or partially solves the technical problem that the sending and receiving ends of a current flexible DC system cannot obtain each other's actual operating status, and the sending-end power grid can only indirectly participate in the frequency regulation of the receiving-end power grid through the flexible DC system.

[0056] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0057] As an example, current technologies have proposed many effective frequency regulation strategies for asynchronous power sources to participate in grid frequency regulation. These include virtual synchronization control and active power-frequency droop control. However, considering the inherent operational constraints of asynchronous power sources, the energy and power support they can provide to the AC grid is limited. Depending on their type and physical characteristics, different types of asynchronous power sources have different operational constraints, resulting in variations in their frequency regulation capabilities. For example, wind turbine pitch angle response time is slow, making it difficult to provide substantial power support in a very short time. Similarly, energy storage has a faster response time, but is limited by its charging state, making it difficult to support system frequency for extended periods.

[0058] In recent years, although many papers have discussed the frequency regulation of different asynchronous power sources, for flexible DC systems, the sending and receiving power grids are decoupled, making it difficult for them to obtain each other's actual operating status. The sending power grid can only indirectly participate in the frequency regulation of the receiving power grid by means of the flexible DC system.

[0059] It is of great significance to study and formulate strategies for the coordinated participation of flexible DC systems and energy storage systems in primary frequency regulation, so as to give full play to the synergistic effect of the sending-end power grid, flexible DC systems and energy storage systems, thereby improving the system frequency stability and power quality.

[0060] Therefore, one of the core inventive points of this invention is: considering the problem of primary frequency regulation in conjunction with flexible DC systems and energy storage systems, a primary frequency regulation method based on the coordination of flexible DC systems and energy storage systems is proposed. First, relevant power system basic data is acquired to participate in subsequent primary frequency regulation calculations. Then, considering the receiving-end converter station, a DC voltage-frequency coupling control strategy is constructed, enabling the receiving end of the flexible DC system to better participate in the primary frequency regulation of the system. Next, based on the control strategy of the receiving-end converter station, considering the sending-end converter station, a power-voltage coupling control strategy is constructed, enabling the sending end of the flexible DC system to better participate in the primary frequency regulation of the system. Considering that relying solely on wind turbines and DC systems may be insufficient to meet the frequency support requirements for the AC grid, the use of energy storage to provide frequency regulation support to the AC grid is further considered. When frequency regulation relying solely on wind turbines and DC systems cannot meet the system's safety and stability requirements, energy storage provides leveling support to the AC grid, maintaining the safe and stable operation of the system. Based on the construction of three control strategies, appropriate frequency regulation strategies can be selected for different frequency regulation needs, improving the flexibility and selectivity of primary frequency regulation and enhancing its effectiveness. By adopting appropriate frequency regulation strategies, system frequency stability can be effectively improved. The technical solution provided by this invention, by effectively utilizing the frequency regulation potential of flexible DC systems and energy storage systems, can provide a reference for the operation of new energy power systems, ensuring the safe and stable operation of the system.

[0061] ReferenceFigure 1 This document illustrates a flowchart of a primary frequency regulation method for a power system according to an embodiment of the present invention. The power system includes a receiving-end converter station, a sending-end converter station, and an energy storage system. The method specifically includes the following steps:

[0062] Step 101: Obtain the inertia parameters of the power system, the first power operation parameters of the receiving-end converter station, and the second power operation parameters of the sending-end converter station;

[0063] In practical applications, when primary frequency regulation of a power system (flexible DC system) is required, relevant data needs to be acquired or calculated. This includes inertia parameters, power operation parameters of the receiving-end converter station (defined here as the first power operation parameter for ease of distinction), and power operation parameters of the sending-end converter station (defined here as the second power operation parameter for ease of distinction).

[0064] Furthermore, inertia parameters mainly include system inertia and virtual inertia. Virtual inertia can be obtained through calculation; the specific calculation method will be discussed later.

[0065] The primary power operating parameters of the receiving-end converter station can include lumped capacitance parameters, receiving-end DC voltage, inflow active power, outflow active power, minimum DC voltage, minimum allowable frequency, rated DC voltage, rated frequency, and instantaneous frequency.

[0066] The second power operation parameters of the sending-end converter station can mainly include the sending-end DC resistance, sending-end DC current, initial operating power of the wind turbine, and maximum output power of the sending end.

[0067] Therefore, by acquiring the aforementioned power data as basic data, it can be used to participate in subsequent primary frequency regulation related calculations.

[0068] Step 102: Based on the first power operation parameters, determine the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control;

[0069] This step primarily establishes the DC voltage-frequency coupling control strategy for the receiving-end converter station, which will be used to participate in the primary frequency regulation of the subsequent power system. Specifically, based on the initial power operating parameters of the receiving-end converter station, the reference value of the DC voltage at the receiving-end converter station under voltage-frequency coupling control is determined.

[0070] As discussed above, the primary power operating parameters of the receiving-end converter station mainly include lumped capacitance parameters, receiving-end DC voltage, inflow active power, outflow active power, minimum DC voltage, minimum allowable frequency, rated DC voltage, rated frequency, and instantaneous frequency. In some embodiments, the process of determining the DC voltage reference value of the receiving-end converter station under voltage-frequency coupled control based on the primary power operating parameters can include: first, constructing a receiving-end DC voltage model based on the lumped capacitance parameters, receiving-end DC voltage, inflow active power, and outflow active power; second, under the condition of satisfying the receiving-end DC voltage model, constructing a model of the maximum energy that the receiving-end converter station can release under the minimum DC voltage based on the lumped capacitance parameters and the rated DC voltage; and third, considering the voltage-frequency coupled control of the receiving-end converter station, solving for the DC voltage reference value of the receiving-end converter station at the minimum allowable frequency based on the maximum energy model and in combination with the rated frequency and instantaneous frequency.

[0071] Specifically, the DC voltage expression for the receiving-end converter station of the flexible DC system can be represented by the following receiving-end DC voltage model:

[0072] (1)

[0073] In the formula, The lumped capacitance parameters of the receiving-end converter station of the flexible DC system; The DC voltage of the receiving-end converter station of the flexible DC system; The active power flowing into the receiving-end converter station of the flexible DC system from the DC side; This refers to the active power flowing out of the receiving-end converter station of the AC-side flexible DC system.

[0074] Assuming the minimum operating DC voltage of the receiving-end converter station of the flexible DC system is... The minimum permissible frequency of the receiving-end power grid is Then the maximum energy allowed to be released by the receiving-end converter station of the flexible DC system is:

[0075] (2)

[0076] In the formula, The maximum energy allowed to be released by the receiving-end converter station of the flexible DC system; This is the rated DC voltage (i.e., the initial value of the DC voltage at the receiving end converter station).

[0077] To maximize the power support capacity of the receiving-end converter station of the flexible DC system, the DC voltage of the receiving-end converter station should be minimized when the grid frequency is lowest. Therefore, equation (3) must be satisfied at any given time. Thus, the reference value for the DC voltage of the receiving-end converter station of the flexible DC system can be set as (4):

[0078] (3)

[0079] (4)

[0080] In the formula, This is the reference value for the DC voltage at the receiving end converter station of the flexible DC system; The rated frequency of the AC power grid; This refers to the instantaneous frequency of the converter bus at the receiving end of the flexible DC system during operation.

[0081] Therefore, considering the receiving end converter station side, a DC voltage-frequency coupling control strategy is constructed so that the receiving end of the flexible DC can better participate in the primary frequency regulation of the system.

[0082] Step 103: Based on the first power operating parameters and the second power operating parameters, determine the power reference value of the sending-end converter station under power-voltage coupling control;

[0083] This step primarily establishes a power control method for the sending-end converter station based on DC voltage information, namely, a power-voltage coupling control strategy for the sending-end converter station, which is used to participate in the primary frequency regulation of the subsequent power system. At this point, the power reference value of the sending-end converter station under power-voltage coupling control can be determined based on the first power operating parameters of the receiving-end converter station and the second power operating parameters of the sending-end converter station.

[0084] Based on the preceding information, the first power operating parameters of the receiving-end converter station can include the receiving-end DC voltage, rated DC voltage, and minimum DC voltage. The second power operating parameters of the sending-end converter station mainly include the sending-end DC resistance, sending-end DC current, initial operating power of the wind turbine, and maximum output power of the sending end. In some embodiments, the process of determining the power reference value of the sending-end converter station under power-voltage coupling control based on the first and second power operating parameters can include: first, determining the sending-end DC voltage of the sending-end converter station based on the receiving-end DC voltage, sending-end DC resistance, and sending-end DC current; then, determining the droop control coefficient based on the initial operating power of the wind turbine, maximum output power of the sending end, rated DC voltage, and minimum DC voltage; and finally, calculating the power reference value of the sending-end converter station under power-voltage coupling control based on the initial operating power of the wind turbine, the droop control coefficient, the sending-end DC voltage, and the rated DC voltage.

[0085] Specifically, the DC voltage of the sending-end and receiving-end converters MMC (Modular Multilevel Converter) satisfies the following equation (5).

[0086] (5)

[0087] In the formula, The DC voltage of the MMC at the sending end; and These are the DC resistance and current at the sending end, respectively.

[0088] In order to enable the sending-end grid to participate in system frequency regulation, the power of the sending-end grid adopts a droop control method coupled with the DC voltage of the receiving-end converter station:

[0089] (6)

[0090] In the formula, Reference power for the flexible direct-transmission converter station; This represents the initial operating power of the wind turbine. This is the droop control coefficient.

[0091] To ensure that the power margin of the flexible direct-transmission converter station is commensurate with the magnitude of frequency regulation, the droop control coefficient... The following formula should be satisfied:

[0092] (7)

[0093] In the formula, The maximum output power of the flexible direct-transmission converter station (sending-end grid) can be achieved.

[0094] Ignoring losses in the DC line resistance, and combining equations (4) and (7), the change in output power of the flexible DC receiving-end converter station with frequency deviation can be approximated by equation (8):

[0095] (8)

[0096] Equation (8) reflects the inertia and primary frequency regulation support power that the flexible DC can provide from the perspective of the AC power grid connected to the receiving end. More specifically, Equation (8) gives the relationship between the receiving end power grid frequency and the sending end flexible DC power reference value (i.e., the actual output power of the flexible DC).

[0097] In the above formula, This refers to the power variation of the flexible DC receiving-end converter station; The frequency variation of the converter bus at the flexible DC receiving end converter station; and These are virtual inertia and damping, respectively, expressed as:

[0098] (9)

[0099] Based on the control strategy of the receiving-end converter station, a power-voltage coupling control strategy for the sending-end converter station is constructed from the perspective of the sending-end converter station, so that the flexible DC transmission end can better participate in the primary frequency regulation of the system.

[0100] Step 104: Based on the inertia parameter, determine the change in energy storage output power when the energy storage system participates in frequency regulation;

[0101] This step primarily establishes a frequency response strategy that takes into account the capacity of the energy storage system, for participation in the primary frequency regulation of the subsequent power system. Specifically, based on inertia parameters, it determines the change in energy storage output power when the energy storage system participates in frequency regulation.

[0102] Based on the foregoing description, inertia parameters can include system inertia and virtual inertia. In some embodiments, the process of determining the change in energy storage output power when the energy storage system participates in frequency regulation based on inertia parameters can include: calculating the energy storage inertia coefficient of the energy storage system when the power system experiences its maximum rate of frequency change, considering the system's maximum power deficit and the maximum output power of the energy storage; calculating the energy storage damping coefficient of the energy storage system when the power system experiences its maximum rate of frequency change, considering the maximum output power of the energy storage; and calculating the change in energy storage output power when the energy storage system participates in frequency regulation based on the energy storage inertia coefficient and the energy storage damping coefficient.

[0103] Furthermore, based on system inertia and virtual inertia, and considering the system's maximum power deficit and the maximum output power of energy storage, the process for calculating the energy storage inertia coefficient of the energy storage system when the power system experiences the maximum rate of frequency change can specifically include: constructing a first maximum rate of frequency change model for the energy storage system when participating in frequency regulation, based on system inertia and virtual inertia and considering the system's maximum power deficit; and calculating the energy storage inertia coefficient of the power system when the power system experiences the maximum rate of frequency change, based on the first maximum rate of frequency change model and considering the maximum output power of energy storage.

[0104] Specifically, in some application scenarios, considering that relying solely on wind turbines and DC systems may be insufficient to meet the demand for frequency support to the AC power grid, it is necessary to further consider utilizing energy storage to provide frequency regulation support to the AC power grid.

[0105] Assume the maximum possible power deficit in the system is After considering the frequency support of the DC system and energy storage, the maximum possible rate of frequency change in the system is... for:

[0106] (10)

[0107] In the formula, For system inertia; Inertia provided for energy storage; This is virtual inertia.

[0108] Assuming the maximum output power of energy storage is The maximum power output of the energy storage is when the system reaches the maximum rate of change of frequency, as shown in equation (11). Thus, the inertia that the energy storage should be set can be obtained as equation (12).

[0109] (11)

[0110] (12)

[0111] This represents the maximum potential power deficit in the system. Assuming the AC power grid does not trigger the three lines of defense during a transient process, the maximum frequency deviation is... The maximum power output of the energy storage is when the system experiences the maximum frequency deviation, as shown in equation (13). Therefore, the damping coefficient that should be set for the energy storage can be obtained. Equation (14).

[0112] (13)

[0113] (14)

[0114] Under the above settings, the change in energy storage output power Set to:

[0115] (15)

[0116] in, This represents the change in system frequency.

[0117] Therefore, considering that relying solely on wind turbines and DC systems may be insufficient to meet the frequency support requirements for the AC power grid, this embodiment of the invention further considers the use of energy storage to provide frequency regulation support to the AC power grid. When frequency regulation using only wind turbines and DC systems cannot meet the system's safety and stability requirements, energy storage provides leveling support to the AC power grid, maintaining the system's safe and stable operation.

[0118] Step 105: Based on the DC voltage reference value and the power reference value, and / or the change in energy storage output power, participate in the primary frequency regulation of the power system to obtain the primary frequency regulation result.

[0119] In some embodiments, the change in energy storage output power participates in the primary frequency regulation of the power system based on the DC voltage reference value and the power reference value, and / or the change in power output power. Specifically, this may include:

[0120] Calculate the second maximum frequency change rate when the energy storage system does not participate in frequency regulation based on the inertia parameter;

[0121] Based on the second maximum frequency change rate, determine whether the change in energy storage output power needs to participate in the primary frequency regulation of the power system.

[0122] If so, it will participate in the primary frequency regulation of the power system based on the DC voltage reference value, power reference value, and changes in energy storage output power.

[0123] If not, it will participate in the primary frequency regulation of the power system based on both the DC voltage reference value and the power reference value.

[0124] Furthermore, based on the second maximum frequency change rate, it is determined whether the change in energy storage output power needs to participate in the primary frequency regulation of the power system. Specifically, this may include:

[0125] Obtain the first maximum frequency change rate of the energy storage system calculated based on the inertia parameter; wherein, the first maximum frequency change rate corresponds to the maximum frequency change rate allowed by the power system;

[0126] Compare the first maximum frequency change rate with the second maximum frequency change rate;

[0127] When the second maximum frequency change rate is greater than or equal to the first maximum frequency change rate, it is determined that the change in energy storage output power needs to participate in the primary frequency regulation of the power system.

[0128] When the second maximum frequency change rate is less than the first maximum frequency change rate, it is determined that the change in energy storage output power does not need to participate in the primary frequency regulation of the power system.

[0129] In practical applications, the maximum rate of frequency change that a system without energy storage may experience is considered to meet the system's safety and stability requirements, i.e., the maximum rate of frequency change without energy storage. Greater than (at this time When the maximum frequency change rate that the system can allow is reached, only the fan and DC system can be used to provide frequency support, that is, the strategy of combining Equation (4) and Equation (6) to form a flexible DC system to participate in primary frequency regulation.

[0130] When the above two strategies cannot be met, an energy storage frequency regulation strategy is added on top of the previous two strategies. That is, by combining equations (4), (6) and (15), a strategy is finally formed in which the flexible DC system and the energy storage system participate in primary frequency regulation.

[0131] Therefore, based on the construction of three control strategies, appropriate frequency modulation strategies can be selected for different frequency modulation requirements, improving the flexibility and selectivity of the system's primary frequency modulation and enhancing its effectiveness. By adopting appropriate frequency modulation strategies, the system's frequency stability can be effectively improved.

[0132] This invention proposes a primary frequency regulation method based on the collaboration of a flexible DC system and an energy storage system. First, the inertia parameters of the power system, the first power operating parameters of the receiving-end converter station, and the second power operating parameters of the sending-end converter station are acquired as basic data for subsequent primary frequency regulation calculations. Next, based on the first power operating parameters, a DC voltage reference value for the receiving-end converter station under voltage-frequency coupled control is determined. This allows for the construction of a DC voltage-frequency coupled control strategy from the receiving-end converter station's perspective, enabling the flexible DC receiving end to better participate in the system's primary frequency regulation. Then, based on the first and second power operating parameters, a power reference value for the sending-end converter station under power-voltage coupled control is determined. Based on the control strategy of the receiving-end converter station, a power-voltage coupled control strategy for the sending-end converter station is constructed from the sending-end converter station's perspective, enabling the flexible DC sending end to better participate in the system's primary frequency regulation. Based on inertia parameters, the change in energy storage output power when the energy storage system participates in frequency regulation is determined. Considering that relying solely on wind turbines and DC systems may be insufficient to meet the frequency support requirements of the AC grid, the possibility of using energy storage to provide frequency regulation support to the AC grid is further considered. When frequency regulation using only wind turbines and DC systems cannot meet the system's safety and stability requirements, energy storage provides leveling support to the AC grid, maintaining the system's safe and stable operation. Finally, based on the DC voltage reference value and power reference value, and / or the change in energy storage output power, the primary frequency regulation of the power system is participated in, obtaining the primary frequency regulation result. Therefore, based on the construction of three control strategies, appropriate frequency regulation strategies can be selected for different frequency regulation needs, improving the flexibility and selectivity of the system's primary frequency regulation and enhancing its effectiveness. By adopting appropriate frequency regulation strategies, the system's frequency stability can be effectively improved. The technical solution provided by this invention, by effectively utilizing the frequency regulation potential of flexible DC systems and energy storage systems, can provide a reference for the operation of new energy power systems and ensure the safe and stable operation of the system.

[0133] For better explanation, refer to Figure 2 This diagram illustrates the overall flow of a primary frequency regulation method for a power system according to an embodiment of the present invention. It should be noted that this embodiment only provides a brief description of the general flow of primary frequency regulation in a power system. The specific implementation process of each step can be understood by referring to the relevant content in the foregoing embodiments, and will not be elaborated upon here. It is understood that the present invention does not impose any limitations on this.

[0134] Step 201: Obtain the inertia parameters of the power system, the first power operation parameters of the receiving-end converter station, and the second power operation parameters of the sending-end converter station;

[0135] Step 202: Based on the first power operation parameters, determine the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control;

[0136] Step 203: Based on the first power operation parameters and the second power operation parameters, determine the power reference value of the sending-end converter station under power-voltage coupling control;

[0137] Step 204: Based on the inertia parameter, determine the change in energy storage output power when the energy storage system participates in frequency regulation, and calculate the second maximum frequency change rate when the energy storage system does not participate in frequency regulation based on the inertia parameter;

[0138] Step 205: Based on the second maximum frequency change rate, determine whether the change in energy storage output power needs to participate in the primary frequency regulation of the power system;

[0139] Step 2061: If so, then simultaneously participate in the primary frequency regulation of the power system based on the DC voltage reference value, power reference value, and energy storage output power change, and obtain the primary frequency regulation result;

[0140] Step 2062: If not, then simultaneously participate in the primary frequency regulation of the power system based on the DC voltage reference value and the power reference value to obtain the primary frequency regulation result.

[0141] To enable those skilled in the art to better understand the technical solutions of the present invention, the following specific example is used to illustrate the embodiments of the present invention.

[0142] This example verifies the technical solution provided in the embodiments of the present invention within a modified IEEE 39-node system. Specifically, the network topology of the modified IEEE 39-node system is as follows: Figure 3 As shown. Figure 3 In this context, MMC-HVDC specifically refers to Modular Multilevel Converter-High Voltage Direct Current, also known as Flexible DC Transmission System (Flexible DC System). The Flexible DC System is connected to node 17. The main parameters of the Flexible DC System are shown in Table 1 below.

[0143]

[0144] The original IEEE 39-bus system had a total installed capacity of approximately 8050 MVA and a load of 6124 MW. After the flexible DC-DC system was integrated, the unit capacity and output remained unchanged, while all loads increased proportionally to maintain supply and demand balance. Assuming a 600 MW load step at bus 22, the simulation results of the system frequency response before and after the integration of flexible DC-DC and energy storage in frequency regulation are as follows: Figure 4 As shown. From Figure 4 As can be seen, the system frequency stability is effectively improved through frequency regulation using flexible DC and energy storage systems. This fully verifies the feasibility and frequency regulation effectiveness of the technical solution of this invention.

[0145] Reference Figure 5 This diagram illustrates a structural block diagram of a primary frequency regulation device for a power system according to an embodiment of the present invention. The power system includes a receiving-end converter station, a sending-end converter station, and an energy storage system. Specifically, the device may include:

[0146] Data acquisition unit 501 is used to acquire the inertia parameters of the power system, the first power operation parameters of the receiving-end converter station, and the second power operation parameters of the sending-end converter station;

[0147] The DC voltage reference value determination unit 502 is used to determine the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control based on the first power operation parameters.

[0148] The power reference value determination unit 503 is used to determine the power reference value of the sending-end converter station under power-voltage coupling control based on the first power operation parameters and the second power operation parameters.

[0149] The energy storage output power change determination unit 504 is used to determine the energy storage output power change when the energy storage system participates in frequency regulation based on the inertia parameter.

[0150] The primary frequency regulation unit 505 is used to participate in the primary frequency regulation of the power system based on the DC voltage reference value and the power reference value, and / or the change in the energy storage output power, to obtain the primary frequency regulation result.

[0151] In one optional embodiment, the first power operating parameters include lumped capacitance parameters, receiving-end DC voltage, inflow active power, outflow active power, minimum DC voltage, minimum permissible frequency, rated DC voltage, rated frequency, and instantaneous frequency; the DC voltage reference value determination unit 502 includes:

[0152] The receiving-end DC voltage model construction unit is used to construct a receiving-end DC voltage model based on the lumped capacitance parameters, the receiving-end DC voltage, the inflow active power, and the outflow active power.

[0153] The maximum energy model construction unit is used to construct, under the condition of satisfying the receiving-end DC voltage model, the maximum energy model that the receiving-end converter station is allowed to release under the minimum DC voltage, based on the lumped capacitance parameters and the rated DC voltage.

[0154] The DC voltage reference value solving unit is used to consider the voltage-frequency coupling control of the receiving-end converter station, and based on the maximum energy model, combined with the rated frequency and the instantaneous frequency, to solve for the DC voltage reference value of the receiving-end converter station at the minimum allowable frequency.

[0155] In one optional embodiment, the first power operating parameters include the receiving-end DC voltage, the rated DC voltage, and the minimum DC voltage; the second power operating parameters include the sending-end DC resistance, the sending-end DC current, the initial operating power of the wind turbine, and the maximum output power at the sending end; the power reference value determination unit 503 includes:

[0156] The sending-end DC voltage determination unit is used to determine the sending-end DC voltage of the sending-end converter station based on the receiving-end DC voltage, the sending-end DC resistance, and the sending-end DC current.

[0157] The droop control coefficient determination unit is used to determine the droop control coefficient based on the initial operating power of the fan, the maximum output power of the sending end, the rated DC voltage, and the minimum DC voltage.

[0158] The power reference value calculation unit is used to calculate the power reference value of the sending-end converter station under power-voltage coupling control based on the initial operating power of the wind turbine, the droop control coefficient, the sending-end DC voltage, and the rated DC voltage.

[0159] In one optional embodiment, the inertia parameter includes system inertia and virtual inertia; the energy storage output power change determination unit 504 includes:

[0160] The energy storage inertia coefficient calculation unit is used to calculate the energy storage inertia coefficient of the energy storage system when the power system experiences the maximum frequency change rate, based on the system inertia and the virtual inertia, taking into account the maximum power deficit of the system and the maximum output power of the energy storage.

[0161] The energy storage damping coefficient calculation unit is used to calculate the energy storage damping coefficient of the power system when the maximum frequency change rate occurs, taking into account the maximum output power of the energy storage.

[0162] The energy storage output power change calculation unit is used to calculate the energy storage output power change when the energy storage system participates in frequency regulation based on the energy storage inertia coefficient and the energy storage damping coefficient.

[0163] In one optional embodiment, the energy storage inertia coefficient calculation unit includes:

[0164] The first maximum frequency change rate model construction unit is used to construct the first maximum frequency change rate model when the energy storage system participates in frequency regulation, based on the system inertia and the virtual inertia, and considering the system's maximum power deficit.

[0165] The energy storage inertia coefficient calculation subunit is used to calculate the energy storage inertia coefficient of the power system when the maximum frequency change rate occurs, based on the first maximum frequency change rate model and considering the maximum output power of energy storage.

[0166] In one alternative embodiment, the primary frequency modulation unit 505 includes:

[0167] The second maximum frequency change rate calculation unit is used to calculate the second maximum frequency change rate when the energy storage system does not participate in frequency regulation, based on the inertia parameter.

[0168] A primary frequency regulation participation determination unit is used to determine, based on the second maximum frequency change rate, whether the change in the energy storage output power needs to participate in the primary frequency regulation of the power system.

[0169] The first execution unit for primary frequency regulation is used to participate in the primary frequency regulation of the power system simultaneously based on the DC voltage reference value, the power reference value, and the change in energy storage output power.

[0170] The primary frequency regulation second execution unit is used to participate in the primary frequency regulation of the power system simultaneously based on the DC voltage reference value and the power reference value.

[0171] In one optional embodiment, the primary frequency modulation participation determination unit includes:

[0172] The first maximum frequency change rate acquisition unit is used to acquire the first maximum frequency change rate calculated by the energy storage system based on the inertia parameter; the first maximum frequency change rate corresponds to the maximum frequency change rate allowed by the power system.

[0173] The maximum frequency change rate comparison unit is used to compare the first maximum frequency change rate with the second maximum frequency change rate.

[0174] The first frequency regulation determination unit is used to determine that the change in the energy storage output power needs to participate in the primary frequency regulation of the power system when the second maximum frequency change rate is greater than or equal to the first maximum frequency change rate.

[0175] The primary frequency regulation second determination unit is used to determine that the change in the energy storage output power does not need to participate in the primary frequency regulation of the power system when the second maximum frequency change rate is less than the first maximum frequency change rate.

[0176] As the device embodiment is basically similar to the method embodiment, it is described in a relatively simple way. For relevant details, please refer to the description of the method embodiment above.

[0177] It should be noted that, in order to enable those skilled in the art to better distinguish data of the same type but with different actual meanings, the embodiments of the present invention use "first" and "second" to distinguish and describe some technical features. "First" and "second" are only used to distinguish data and have no other special meaning. It is understood that the present invention does not impose any limitations on them.

[0178] This invention also provides an electronic device, which includes a processor and a memory:

[0179] The memory is used to store program code and transfer the program code to the processor;

[0180] The processor is used to execute the primary frequency regulation method of the power system according to the instructions in the program code of any embodiment of the present invention.

[0181] This invention also provides a computer-readable storage medium for storing program code for executing a primary frequency regulation method for a power system according to any embodiment of this invention.

[0182] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0183] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0184] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0185] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0186] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0187] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A primary frequency regulation method for a power system, characterized in that, The power system includes a receiving-end converter station, a sending-end converter station, and an energy storage system; the method includes: Obtain the inertia parameters of the power system, the first power operation parameters of the receiving-end converter station, and the second power operation parameters of the sending-end converter station; Based on the first power operation parameters, determine the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control; Based on the first power operation parameters and the second power operation parameters, the power reference value of the sending-end converter station under power-voltage coupling control is determined; Based on the inertia parameter, determine the change in energy storage output power when the energy storage system participates in frequency regulation; Based on the DC voltage reference value and the power reference value, and / or, the change in the energy storage output power participates in the primary frequency regulation of the power system to obtain the primary frequency regulation result.

2. The primary frequency regulation method for a power system according to claim 1, characterized in that, The first power operating parameters include lumped capacitance parameters, receiving-end DC voltage, inflow active power, outflow active power, minimum DC voltage, minimum allowable frequency, rated DC voltage, rated frequency, and instantaneous frequency; the step of determining the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control based on the first power operating parameters includes: Based on the lumped capacitance parameters, the receiving-end DC voltage, the inflow active power, and the outflow active power, a receiving-end DC voltage model is constructed. Under the condition of satisfying the receiving-end DC voltage model, a model of the maximum energy that the receiving-end converter station can release under the minimum DC voltage is constructed based on the lumped capacitance parameters and the rated DC voltage. Considering the voltage-frequency coupling control of the receiving-end converter station, based on the maximum energy model and in combination with the rated frequency and the instantaneous frequency, the DC voltage reference value of the receiving-end converter station at the minimum allowable frequency is solved.

3. The primary frequency regulation method for a power system according to claim 1, characterized in that, The first power operating parameters include the receiving-end DC voltage, rated DC voltage, and minimum DC voltage; the second power operating parameters include the sending-end DC resistance, sending-end DC current, initial operating power of the wind turbine, and maximum output power of the sending end; determining the power reference value of the sending-end converter station under power-voltage coupling control based on the first and second power operating parameters includes: The DC voltage at the receiving end is determined based on the DC resistance at the sending end and the DC current at the sending end. The droop control coefficient is determined based on the initial operating power of the fan, the maximum output power of the sending end, the rated DC voltage, and the minimum DC voltage. Based on the initial operating power of the wind turbine, the droop control coefficient, the DC voltage at the sending end, and the rated DC voltage, calculate the power reference value of the sending end converter station under power-voltage coupling control.

4. The primary frequency regulation method for a power system according to claim 1, characterized in that, The inertia parameters include system inertia and virtual inertia; determining the change in energy storage output power when the energy storage system participates in frequency regulation based on the inertia parameters includes: Based on the system inertia and the virtual inertia, considering the system's maximum power deficit and the maximum output power of the energy storage, the energy storage inertia coefficient of the energy storage system is calculated when the power system experiences the maximum rate of frequency change. Considering the maximum output power of the energy storage, calculate the energy storage damping coefficient of the energy storage system when the power system experiences the maximum rate of frequency change. Based on the energy storage inertia coefficient and the energy storage damping coefficient, the change in energy storage output power when the energy storage system participates in frequency regulation is calculated.

5. The primary frequency regulation method for a power system according to claim 4, characterized in that, Based on the system inertia and the virtual inertia, and considering the system's maximum power deficit and the maximum output power of the energy storage, the energy storage inertia coefficient of the energy storage system is calculated when the power system experiences its maximum rate of frequency change, including: Based on the system inertia and the virtual inertia, and considering the maximum power deficit of the system, a model of the first maximum frequency change rate when the energy storage system participates in frequency regulation is constructed. Based on the first maximum frequency change rate model, and considering the maximum output power of the energy storage, the energy storage inertia coefficient of the power system when the maximum frequency change rate occurs is calculated.

6. The primary frequency regulation method for a power system according to any one of claims 1 to 5, characterized in that, The step of having the energy storage output power change participate in the primary frequency regulation of the power system based on the DC voltage reference value and the power reference value, and / or, includes: Based on the inertia parameter, calculate the second maximum frequency change rate when the energy storage system does not participate in frequency regulation; Based on the second maximum frequency change rate, determine whether the change in the energy storage output power needs to participate in the primary frequency regulation of the power system; If so, then the power system's primary frequency regulation is simultaneously based on the DC voltage reference value, the power reference value, and the change in energy storage output power. If not, then the power system will participate in primary frequency regulation based on both the DC voltage reference value and the power reference value.

7. The primary frequency regulation method for a power system according to claim 6, characterized in that, The step of determining whether the change in energy storage output power needs to participate in the primary frequency regulation of the power system based on the second maximum frequency change rate includes: Obtain the first maximum frequency change rate calculated by the energy storage system based on the inertia parameter; the first maximum frequency change rate corresponds to the maximum frequency change rate allowed by the power system; Compare the first maximum frequency change rate with the second maximum frequency change rate; When the second maximum frequency change rate is greater than or equal to the first maximum frequency change rate, it is determined that the change in the energy storage output power needs to participate in the primary frequency regulation of the power system. When the second maximum frequency change rate is less than the first maximum frequency change rate, it is determined that the change in the energy storage output power does not need to participate in the primary frequency regulation of the power system.

8. A primary frequency regulation device for a power system, characterized in that, The power system includes a receiving-end converter station, a sending-end converter station, and an energy storage system; the device includes: The data acquisition unit is used to acquire the inertia parameters of the power system, the first power operation parameters of the receiving-end converter station, and the second power operation parameters of the sending-end converter station. A DC voltage reference value determination unit is used to determine the DC voltage reference value of the receiving-end converter station under voltage-frequency coupling control based on the first power operation parameters. A power reference value determination unit is used to determine the power reference value of the sending-end converter station under power-voltage coupling control based on the first power operating parameters and the second power operating parameters. An energy storage output power change determination unit is used to determine the energy storage output power change when the energy storage system participates in frequency regulation based on the inertia parameter. A primary frequency regulation unit is used to participate in the primary frequency regulation of the power system based on the DC voltage reference value, the power reference value, and / or the change in energy storage output power, to obtain the primary frequency regulation result.

9. An electronic device, characterized in that, The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the primary frequency regulation method of the power system according to any one of claims 1-7 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium is used to store program code for executing the primary frequency regulation method of the power system according to any one of claims 1-7.

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