Frequency control method and device of optical storage system, medium and equipment

Abstract

The invention discloses a frequency control method and device for an optical storage system, a medium and equipment, and the method comprises the steps: monitoring the actual frequency of a power system, and when the actual frequency is not equal to a rated frequency, calculating the frequency of the power system based on the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid-connected point of the optical storage system and a power grid system; determining a fault type; when the fault type is a non-unidirectional frequency anomaly accident, acquiring a change rate of a frequency variation of the power system, modifying an active droop coefficient based on the change rate and the frequency deviation of the frequency variation, and acquiring a change amount of active power based on the change rate and the frequency deviation of the frequency variation and the modified active droop coefficient; and obtaining the frequency of the power system based on the variable quantity of the active power. According to the invention, the problem of contradiction between an instruction generated by adopting a traditional frequency control technology and a demand is solved, so that the stored energy is charged and discharged according to an actual situation, and more serious frequency fluctuation caused by wrong charging and discharging of the stored energy is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency control of power systems, and in particular to a frequency control method, device, medium and equipment for a photovoltaic storage system. Background Art

[0002] With the continuous development of power technology, the "double high" power system, that is, a high proportion of new energy and a high proportion of power electronics, has become the main trend of current power development. The continuous advancement of this trend has significantly increased the proportion of new energy in the power system, but it has also caused the inertia level of the power system to drop sharply. In the power system, the load is constantly changing. Although the low-inertia power system can respond quickly to load changes, it needs to adjust the frequency when disturbed to ensure that the output power of the generator can keep up with the load changes in time and maintain the stable operation of the system.

[0003] At present, the frequency regulation method of the photovoltaic storage system is mainly designed based on the frequency change in a single direction. The frequency change in a single direction includes machine cutting, sudden increase in load and sudden decrease in load. For example, when the system is cutting off the machine, if part of the circuit is cut off due to system failure or maintenance needs, it may cause other circuits in the overloaded part of the system to be cut off by the protection device. At this time, the system frequency will be adjusted upward. When the load increases suddenly, especially during peak power consumption periods such as summer and winter, the system frequency will decrease because the system active output is lower than the system active consumption. The grid-type VSG (virtual synchronous generator) control technology is usually used for frequency regulation when the frequency changes in a single direction. The virtual synchronous generator simulates the stator and rotor functions of the synchronous generator, realizes the conversion of DC power to AC power, and also provides inertia support for the power system.

[0004] Although the situations of machine cutting, sudden increase in load and sudden decrease in load can cover most of the frequency instability caused by disturbances, there are other types of non-unidirectional frequency abnormal change events in the actual power system, such as short circuit faults, DC blocking, etc. When a non-unidirectional frequency abnormal change event occurs in the transmission line, the photovoltaic storage will perform corresponding charging and discharging actions under the control of the grid-forming VSG to adjust the frequency, thereby maintaining the stability of the system frequency. However, in actual applications, this traditional frequency regulation strategy will have problems in some cases. For example, when a short circuit fault occurs, the system output power is excessive in a short period of time, resulting in an instantaneous increase in the system frequency. Although the VSG control can respond and enable the energy storage system to absorb the excess active power of the system to prevent the frequency from rising, after the fault is restored, when the active output in the system is lower than the active consumption, resulting in insufficient active power, the system frequency will drop, and the system output power is required to prevent the frequency from falling. At this time, due to the problem of the control strategy, the photovoltaic storage system still receives the charging signal instead of the discharging signal, resulting in the actual action of the energy storage being inconsistent with the system demand, which in turn causes a more serious frequency drop problem, resulting in the instability of the frequency of the power grid system. Summary of the invention

[0005] In view of this, the present invention provides a frequency control method, device, medium and equipment for a photovoltaic storage system, the main purpose of which is to solve the problem of low frequency stability of the frequency control method of the existing photovoltaic storage system.

[0006] According to one aspect of the present application, a frequency control method for an optical storage system is provided, the method comprising:

[0007] The actual frequency of the power system is monitored, and when it is monitored that the actual frequency is not equal to the rated frequency, a frequency deviation between the actual frequency and the rated frequency, and a zero-sequence voltage at a grid connection point of a photovoltaic storage system and a power grid system are obtained, and the fault type is determined based on the zero-sequence voltage and the frequency deviation, wherein the power system includes a photovoltaic storage system and a power grid system;

[0008] When the fault type is a non-unidirectional frequency abnormality accident, the change rate of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained, based on the change rate of the frequency change amount and the frequency deviation, the frequency deviation change trend amount is obtained, and based on the frequency deviation change trend amount, the active power droop coefficient is modified to obtain a new active power droop coefficient;

[0009] Based on the rate of change of the frequency change, the frequency deviation and the new active droop coefficient, the change of active power is obtained, and the change of active power is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur;

[0010] Based on the change in active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained.

[0011] Optionally, the determining of the fault type based on the zero-sequence voltage and the frequency deviation includes:

[0012] Determine whether the zero-sequence voltage is less than a preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than a preset frequency difference. If the zero-sequence voltage is greater than or equal to the preset voltage, determine that the fault type is a unidirectional frequency abnormality accident.

[0013] If the frequency deviation is greater than the preset frequency difference, the fault type is determined to be a non-unidirectional frequency abnormality accident; if the frequency deviation is less than or equal to the preset frequency difference, the fault type is determined to be a unidirectional frequency abnormality accident.

[0014] Optionally, obtaining a frequency deviation change trend amount based on the change rate of the frequency change amount and the frequency deviation, and modifying the active power droop coefficient based on the frequency deviation change trend amount to obtain a new active power droop coefficient includes:

[0015] The product of the rate of change of the frequency change amount and the frequency deviation is used as the frequency deviation change trend amount;

[0016] If the frequency deviation change trend amount is less than zero, the initial active power droop coefficient is inverted to serve as a new active power droop coefficient.

[0017] Optionally, obtaining the change in active power based on the change rate of the frequency change, the frequency deviation and the new active power droop coefficient includes:

[0018] Acquire a virtual inertia coefficient, and obtain a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient;

[0019] Based on the new active droop coefficient and the frequency deviation, obtaining a compensation value of a first virtual droop control;

[0020] The sum of the compensation value of the first virtual droop control and the compensation value of the virtual inertia control is taken as the change in active power.

[0021] Optionally, after determining that the fault type is a unidirectional frequency abnormality accident or if the frequency deviation change trend amount is greater than or equal to zero, the frequency control method of the photovoltaic storage system further includes:

[0022] Acquire a virtual inertia coefficient, and obtain a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient;

[0023] Based on the initial active power droop coefficient and the frequency deviation, obtaining a compensation value for a second virtual droop control;

[0024] The sum of the compensation value of the second virtual droop control and the compensation value of the virtual inertia control is used as the change in active power.

[0025] Optionally, the active power-frequency control method based on the change in active power and the virtual synchronous generator adopts the following method to obtain the frequency of the power system:

[0026]

[0027] Where J is the moment of inertia, is the rate of change of frequency change, ΔP is the change of active power, D p is the damping coefficient, ω ref is the rated angular frequency of the power system, and f is the frequency of the power system.

[0028] According to another aspect of the present application, a frequency control device of an optical storage system is provided, comprising:

[0029] A fault type determination module is used to monitor the actual frequency of the power system, and when it is monitored that the actual frequency is not equal to the rated frequency, obtain the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system, and determine the fault type based on the zero-sequence voltage and the frequency deviation, wherein the power system includes the photovoltaic storage system and the power grid system;

[0030] An active droop coefficient modification module is used for, when the fault type is a non-unidirectional frequency abnormality accident, obtaining a change rate of a frequency change amount after a non-unidirectional frequency abnormality accident occurs in the power system, obtaining a frequency deviation change trend amount based on the change rate of the frequency change amount and the frequency deviation, and modifying an active droop coefficient based on the frequency deviation change trend amount to obtain a new active droop coefficient;

[0031] An active power change acquisition module, used to obtain the active power change based on the change rate of the frequency change, the frequency deviation and the new active droop coefficient, wherein the active power change is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur;

[0032] The frequency acquisition module is used to obtain the frequency of the power system based on the change in active power and the active power-frequency control method of the virtual synchronous generator.

[0033] Optionally, the fault type determination module is further used to:

[0034] Determine whether the zero-sequence voltage is less than a preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than a preset frequency difference. If the zero-sequence voltage is greater than or equal to the preset voltage, determine that the fault type is a unidirectional frequency abnormality accident.

[0035] If the frequency deviation is greater than the preset frequency difference, the fault type is determined to be a non-unidirectional frequency abnormality accident; if the frequency deviation is less than or equal to the preset frequency difference, the fault type is determined to be a unidirectional frequency abnormality accident.

[0036] Optionally, the active droop coefficient modification module is further used for:

[0037] The product of the rate of change of the frequency change amount and the frequency deviation is used as the frequency deviation change trend amount;

[0038] If the frequency deviation change trend amount is less than zero, the initial active power droop coefficient is inverted to serve as a new active power droop coefficient.

[0039] Optionally, the active power change acquisition module is further used for:

[0040] Acquire a virtual inertia coefficient, and obtain a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient;

[0041] Based on the new active droop coefficient and the frequency deviation, obtaining a compensation value of a first virtual droop control;

[0042] The sum of the compensation value of the first virtual droop control and the compensation value of the virtual inertia control is taken as the change in active power.

[0043] Optionally, after determining that the fault type is a unidirectional frequency abnormality accident or if the frequency deviation change trend amount is greater than or equal to zero, the active power change amount acquisition module is further used to:

[0044] Acquire a virtual inertia coefficient, and obtain a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient;

[0045] Based on the initial active power droop coefficient and the frequency deviation, obtaining a compensation value for a second virtual droop control;

[0046] The sum of the compensation value of the second virtual droop control and the compensation value of the virtual inertia control is used as the change in active power.

[0047] Optionally, the frequency acquisition module is further used to obtain the frequency of the power system by adopting the following method:

[0048]

[0049] Where J is the moment of inertia, is the rate of change of frequency change, ΔP is the change of active power, D p is the damping coefficient, ω ref is the rated angular frequency of the power system, and f is the frequency of the power system.

[0050] According to another aspect of the present application, a storage medium is provided, wherein at least one executable instruction is stored in the storage medium, and the executable instruction enables a processor to execute operations corresponding to the frequency control method of the optical storage system.

[0051] According to another aspect of the present application, a computer device is provided, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus;

[0052] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the frequency control method of the optical storage system.

[0053] By means of the above technical solution, the technical solution provided by the embodiment of the present invention has at least the following advantages:

[0054] The present application provides a frequency control method, device, equipment and medium for a photovoltaic storage system. When the actual frequency fluctuates, the fault type is determined to be a non-unidirectional frequency abnormality accident based on the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system. The rate of change of the frequency change after the non-unidirectional frequency abnormality accident occurs in the power system is obtained. Based on the rate of change of the frequency change and the frequency deviation, a frequency deviation change trend is obtained. The frequency deviation change trend can indicate whether the fault has been restored. When the frequency deviation change trend indicates that the fault has been restored, the active power droop coefficient is modified. Based on the modified active power droop coefficient, the change in active power is calculated. At this time, the calculated change in active power is greater than zero, and the energy storage system discharges to provide active power to prevent the frequency from continuing to drop. Therefore, according to the change in active power, the frequency of the power system obtained is a frequency that drops more slowly, which helps the frequency to smoothly return to the rated state, solving the problem of contradiction between instructions and demands caused by adopting traditional frequency control technology, allowing the energy storage to be charged and discharged according to actual conditions to prevent more serious frequency fluctuations caused by incorrect charging and discharging of energy storage, making the system frequency more stable, and at the same time distinguishing unidirectional frequency changes from non-unidirectional frequency changes so that corresponding control strategies can be adopted respectively, supplementing the current technology for frequency change events.

[0055] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0057] Figure 1 A flow chart of a frequency control method of a photovoltaic storage system provided in an embodiment of the present application is shown;

[0058] Figure 2a The structure diagram of the grid-connected photovoltaic energy storage provided in the embodiment of the present application is shown;

[0059] Figure 2b A schematic diagram of an active control loop of a grid-connected photovoltaic energy storage system provided in an embodiment of the present application is shown;

[0060] Figure 3 A frequency response characteristic diagram under a non-unidirectional frequency abnormal change event provided by an embodiment of the present application is shown;

[0061] Figure 4 A flow chart showing a frequency control method of another photovoltaic storage system provided in an embodiment of the present application is shown;

[0062] Figure 5 A flow chart showing another frequency control method of a photovoltaic storage system provided in an embodiment of the present application is shown;

[0063] Figure 6 A flow chart showing a frequency control method of another photovoltaic storage system provided in an embodiment of the present application is shown;

[0064] Figure 7 A structural block diagram of a frequency control device of another optical storage system provided in an embodiment of the present application is shown;

[0065] Figure 8 A schematic structural diagram of a computer device provided by an embodiment of the present invention is shown.

[0066] in,

[0067] Figure 7 In: 702-fault type determination module; 704-active power droop coefficient modification module; 706-active power change acquisition module; 708-frequency acquisition module;

[0068] Figure 8 In it: 802 - processor; 804 - communication interface; 806 - memory; 808 - communication bus; 810 - program. DETAILED DESCRIPTION

[0069] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0070] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0071] In view of the problem that the frequency stability of the existing frequency control method for the photovoltaic storage system is low, the embodiment of the present application provides a frequency control method for the photovoltaic storage system, such as Figure 1 As shown, the method includes:

[0072] 102: monitoring the actual frequency of the power system, and when it is monitored that the actual frequency is not equal to the rated frequency, obtaining a frequency deviation between the actual frequency and the rated frequency, and a zero-sequence voltage at a grid connection point of the photovoltaic storage system and the grid system, and determining a fault type based on the zero-sequence voltage and the frequency deviation, wherein the power system includes the photovoltaic storage system and the grid system;

[0073] 104: When the fault type is a non-unidirectional frequency abnormality accident, the change rate of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained, based on the change rate of the frequency change amount and the frequency deviation, the frequency deviation change trend amount is obtained, and based on the frequency deviation change trend amount, the active power droop coefficient is modified to obtain a new active power droop coefficient;

[0074] 106: based on the change rate of the frequency change, the frequency deviation and the new active droop coefficient, the change of active power is obtained, and the change of active power is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur;

[0075] 108: Based on the change in active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained.

[0076] Specifically, the power system of the present application includes a photovoltaic storage system and a power grid system, and the power system is a grid-connected photovoltaic storage structure, such as Figure 2a The PV-storage system is connected to the grid using the traditional grid-building VSG control technology. When an abnormal frequency change event occurs in the transmission line of the grid-connected system, the system frequency will fluctuate accordingly. At this time, the energy storage takes effect under the control of the grid-building VSG, and performs corresponding charging and discharging actions to adjust the frequency to maintain the stability of the system frequency.

[0077] Traditional VSG control can simulate the operating characteristics of synchronous machines more accurately than droop control by simulating the second-order equation of synchronous generator rotor motion. The second-order equation of synchronous machine rotor motion is shown below

[0078]

[0079] Where J is the moment of inertia of the synchronous machine; T m , T e are mechanical torque and electromagnetic torque respectively; D p is the damping coefficient.

[0080] The active-frequency equation and reactive-voltage equation of grid-type VSG control are as follows:

[0081]

[0082] V=V ref +D q (Q ref -Q) (3)

[0083] like Figure 2b As shown, according to the relationship between angular frequency and system frequency ω=2πf, the active control link can be further solved as

[0084]

[0085]

[0086] In the formula, K p is the active power droop coefficient, -K p Δf is the virtual droop control part, simulating the damping characteristics of the synchronous machine; K d is the virtual inertia coefficient, For virtual inertia control, the inertia response characteristics of the synchronous machine are simulated.

[0087] Substitute the deviation Δf between the actual frequency and the rated frequency and the rate of change of the frequency change dΔf / dt into formula 5 to calculate the change in output power ΔP. Substitute the change in output power ΔP into formula 2 to calculate the frequency. The frequency controlled by this frequency control method is relatively stable when the machine is cut off, the load suddenly increases, or the load suddenly decreases.

[0088] Although machine shedding, sudden load increase and sudden load decrease can cover most of the disturbances in the circuit that lead to frequency instability, in actual systems, in addition to the above-mentioned unidirectional frequency change events, there are also non-unidirectional frequency abnormal change events caused by short circuit faults, DC lockout, etc.

[0089] Taking a three-phase short circuit fault as an example, the fault frequency waveform is as follows: Figure 3 As shown, t 0 At this moment, when a three-phase short circuit occurs, the system output power is excessive for a short time, and the system frequency rises instantaneously. At this time, the VSG control responds, and the output power change ΔP = -K(ff N )<0, the energy storage system absorbs the excess active power of the system to prevent the increase of system frequency. 1 At this moment, when the instantaneous short circuit fault is restored to normal, the load returns to the normal level, the active output of the system is lower than the active consumption, resulting in insufficient active power, and the system frequency drops. At this time, the energy storage system needs to discharge to prevent the frequency from dropping. However, since the deviation Δf between the actual frequency and the rated frequency is still greater than 0, according to the droop control method ΔP=-K(ff N )<0, the energy storage still receives the charging signal, resulting in the actual action of the energy storage being inconsistent with the system requirements, which may lead to a more serious frequency drop. 2 At this moment, when the frequency drops to the rated value, due to inertia, the frequency will continue to drop. At this time, VSG control causes the energy storage to discharge. According to the droop control method, ΔP = -K (ff N )>0, the energy storage receives the discharge signal and provides active power to the system to prevent the frequency from continuing to drop.

[0090] Therefore, the traditional frequency control method is not suitable for non-unidirectional frequency abnormal change events, resulting in the actual energy storage action being inconsistent with system requirements, leading to more serious frequency drop. Therefore, this application proposes a frequency control method for non-unidirectional frequency abnormal change events.

[0091] Specifically, the frequency of the power system is monitored. The rated frequencies of the photovoltaic storage system and the power grid system are both 50Hz. When the actual frequency is not equal to the rated frequency, it means that the frequency of the system fluctuates and an accident may occur. The frequency deviation (also called frequency change) Δf between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system are obtained. The fault type is judged based on the frequency deviation and the zero-sequence voltage to determine whether it is a non-unidirectional frequency abnormal change event or a unidirectional frequency abnormal change event. When a non-unidirectional frequency abnormal change event occurs, the rate of change of the frequency change is obtained. The change of the frequency change (i.e., the increase or decrease of the frequency) over time is usually expressed as dΔf / dt, that is, the derivative of the frequency change Δf with respect to time t. The frequency deviation change trend is calculated based on the frequency deviation Δf and the rate of change of the frequency change dΔf / dt. The frequency deviation change trend can characterize whether the fault is restored. When the frequency deviation change trend is less than zero, it indicates non-unidirectional frequency recovery. At this time, the active power droop coefficient is modified so that the change in output power based on the modified active power droop coefficient is greater than zero. The energy storage receives the signal for discharge and provides active power to prevent the continuous decrease in frequency, which is equivalent to increasing the regulation frequency and improving the stability of frequency regulation.

[0092] The present application provides a frequency control method for a photovoltaic storage system. Compared with the prior art, when the actual frequency is monitored to fluctuate, the fault type is determined to be a non-unidirectional frequency abnormality accident according to the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system. The change rate of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained. Based on the change rate of the frequency change amount and the frequency deviation, the frequency deviation change trend amount is obtained. The frequency deviation change trend amount can indicate whether the fault is restored. When the frequency deviation change trend amount indicates that the fault is restored, the active power droop coefficient is modified. Based on the modified active power droop coefficient, the change of active power is calculated. quantification, at this time the calculated change in active power is greater than zero, the energy storage system discharges and provides active power to prevent the continuous decrease in frequency. Therefore, according to the change in active power, the frequency of the power system obtained is a frequency that decreases more slowly, which helps the frequency to smoothly return to the rated state, solving the problem of contradiction between instructions and demands caused by traditional control technology, allowing the energy storage to be charged and discharged according to actual conditions to prevent more serious frequency fluctuations caused by incorrect charging and discharging of energy storage, making the system frequency more stable, and distinguishing unidirectional frequency changes from non-unidirectional frequency changes so as to adopt corresponding control strategies respectively, supplementing the current technology for frequency change events.

[0093] In another embodiment of the present invention, in order to further define and illustrate, as Figure 4 As shown, the frequency control method of the optical storage system also includes:

[0094] 402: Determine whether the zero-sequence voltage is less than a preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than a preset frequency difference. If the frequency deviation is greater than the preset frequency difference, determine that the fault type is a non-unidirectional frequency abnormality accident.

[0095] 404: when the fault type is a non-unidirectional frequency abnormality accident, the change rate of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained, and the product of the change rate of the frequency change amount and the frequency deviation is used as the frequency deviation change trend amount. If the frequency deviation change trend amount is less than zero, the initial active power droop coefficient is inverted to be used as the new active power droop coefficient;

[0096] 406: Obtain a virtual inertia coefficient, obtain a compensation value of virtual inertia control based on the change rate of the frequency change and the virtual inertia coefficient; obtain a compensation value of the first virtual droop control based on the new active power droop coefficient and the frequency deviation; and use the sum of the compensation value of the first virtual droop control and the compensation value of the virtual inertia control as the change of active power;

[0097] 408: Based on the change in active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained.

[0098] Specifically, the frequency deviation between the actual frequency and the rated frequency, the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system are obtained, and the zero-sequence voltage U 0 额 *85% and frequency deviation Δf>0.033Hz are used as judgment conditions to distinguish single-direction frequency abnormal events from non-single-direction frequency abnormalities. The zero-sequence voltage U 0 额 *85% and the frequency deviation Δf>0.033Hz, the fault type is determined to be a non-unidirectional frequency abnormality accident. After the fault is restored, the existing active-frequency control method of the grid-type VSG will cause the actual action of the energy storage to conflict with the system demand, resulting in a more serious frequency drop. Therefore, it is determined whether the product of the frequency deviation and the rate of change of the frequency change is negative. If the product of the frequency deviation and the rate of change of the frequency change is negative, it means that the instantaneous short-circuit fault is restored, and the system frequency enters the beginning of the decline stage. The initial active droop coefficient is reversed to obtain a new active droop coefficient. The output power change ΔP>0 calculated based on the new active droop coefficient. In the case of the output power change ΔP>0, the energy storage receives the signal to discharge and provide active power to prevent the continuous decline of the frequency, so as to prevent the energy storage from being charged and discharged incorrectly and causing more serious frequency fluctuations, so that the system frequency is more stable, solving the problem of the contradiction between the instructions and the demand in the existing technology in this scenario.

[0099] ​​In another embodiment of the present invention, in order to further define and illustrate, as Figure 5 As shown, the frequency control method of the optical storage system also includes:

[0100] 502: Determine that the fault type is a one-way frequency abnormality accident or determine that the frequency deviation change trend is greater than or equal to zero;

[0101] Specifically, determine whether the zero-sequence voltage is less than the preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than the preset frequency difference. If the frequency deviation is less than or equal to the preset frequency difference, determine that the fault type is a unidirectional frequency abnormality accident; if the zero-sequence voltage is greater than or equal to the preset voltage, determine that the fault type is a unidirectional frequency abnormality accident.

[0102] 504: obtaining a virtual inertia coefficient, obtaining a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient; obtaining a compensation value of a second virtual droop control based on the initial active power droop coefficient and the frequency deviation; and taking the sum of the compensation value of the second virtual droop control and the compensation value of the virtual inertia control as the change of active power;

[0103] 506: Based on the change in active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained.

[0104] Specifically, when the fault type is determined to be a unidirectional frequency abnormality accident, the existing active power-frequency control method of the grid-forming VSG will not cause the actual action of the energy storage to be inconsistent with the system demand, and will not cause a more serious frequency drop. Therefore, the unidirectional frequency abnormality accident adopts the existing active power-frequency control method of the grid-forming VSG, that is, the initial active power droop coefficient is adopted.

[0105] When the frequency deviation change trend is greater than or equal to zero, it indicates that the short-circuit fault has not been restored, and the energy storage system continues to absorb excess active power of the system to prevent the increase in system frequency. It will not cause the actual action of the energy storage to be inconsistent with the system demand, and will not lead to more serious frequency drops. Therefore, the one-way frequency abnormality accident adopts the existing active power-frequency control method of the grid-type VSG, that is, the initial active power droop coefficient is adopted.

[0106] In one embodiment, based on the change in active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained by the following method:

[0107]

[0108] Where J is the moment of inertia, is the rate of change of frequency change, ΔP is the change of active power, D p is the damping coefficient, ω refis the rated angular frequency of the power system, and f is the frequency of the power system.

[0109] In one embodiment, Figure 6 As shown in the figure, taking a short-circuit fault in the power system as an example, first, when the system frequency fluctuates, a disturbance judgment is performed to obtain the frequency deviation between the actual frequency and the rated frequency, the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the grid system, and the zero-sequence voltage U 0 额* 85% and the frequency deviation Δf>0.033Hz crosses the frequency modulation dead zone as the judgment condition, distinguishing the single-direction frequency abnormality event from the non-single-direction frequency abnormality, and the zero-sequence voltage U 0 额* When the frequency deviation Δf>0.033Hz is 85%, it is a non-unidirectional frequency abnormal event. The rest are unidirectional frequency abnormal events, which makes up for the problem that the prior art lacks analysis of the cause of abnormal frequency change. If the accident is a non-unidirectional frequency abnormal event, it is determined whether the product of the frequency deviation Δf and the rate of change of the frequency change dΔf / dt is negative. If the product of the frequency deviation Δf and the rate of change of the frequency change dΔf / dt is negative, it is an instantaneous short-circuit fault recovery, and the system frequency enters the beginning of the decline stage. The initial active droop coefficient K p becomes -K p , at this time, the output power change ΔP>0, the energy storage receives the signal to discharge, and provides active power to prevent the continuous decrease of frequency, which solves the problem of the contradiction between the instructions and the demand in the existing technology in this scenario. If the accident is a unidirectional frequency abnormality event or the product of the frequency deviation Δf and the change rate of the frequency change dΔf / dt is not negative, the frequency response is performed in the traditional way, that is, the initial active droop coefficient K p Calculate the change in output power ΔP.

[0110] Furthermore, as a response to the above Figure 1 In order to realize the method shown in the figure, the embodiment of the present invention provides a frequency control device for an optical storage system, such as Figure 7 As shown, the device comprises:

[0111] The fault type determination module 702 is used to monitor the actual frequency of the power system. When it is monitored that the actual frequency is not equal to the rated frequency, the frequency deviation between the actual frequency and the rated frequency, the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system are obtained, and the fault type is determined based on the zero-sequence voltage and the frequency deviation, wherein the power system includes the photovoltaic storage system and the power grid system;

[0112] ​​The active power droop coefficient modification module 704 is used to obtain the rate of change of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system when the fault type is a non-unidirectional frequency abnormality accident, obtain the frequency deviation change trend amount based on the rate of change of the frequency change amount and the frequency deviation, and modify the active power droop coefficient based on the frequency deviation change trend amount to obtain a new active power droop coefficient;

[0113] The active power change amount acquisition module 706 is used to obtain the active power change amount based on the change rate of the frequency change amount, the frequency deviation and the new active power droop coefficient, and the active power change amount is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur;

[0114] The frequency acquisition module 708 is used to obtain the frequency of the power system based on the change in active power and the active power-frequency control method of the virtual synchronous generator.

[0115] The present application provides a frequency control device for a photovoltaic storage system. Compared with the prior art, when it is monitored that the actual frequency fluctuates, the fault type is determined to be a non-unidirectional frequency abnormality accident based on the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system. The rate of change of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained. Based on the rate of change of the frequency change amount and the frequency deviation, a frequency deviation change trend amount is obtained. The frequency deviation change trend amount can indicate whether the fault has been restored. When the frequency deviation change trend amount indicates that the fault has been restored, the active power droop coefficient is modified. Based on the modified active power droop coefficient, the change in active power is calculated. At this time, the calculated change in active power is greater than zero, and the energy storage system discharges to provide active power to prevent the frequency from continuing to drop. Therefore, according to the change in active power, the frequency of the power system obtained is a frequency that drops more slowly, which helps the frequency to smoothly return to the rated state, solving the problem of contradiction between instructions and demands caused by traditional frequency control technology, allowing the energy storage to be charged and discharged according to actual conditions to prevent more serious frequency fluctuations caused by incorrect charging and discharging of energy storage, making the system frequency more stable, and at the same time distinguishing unidirectional frequency changes from non-unidirectional frequency changes so that corresponding control strategies can be adopted respectively, supplementing the current technology for frequency change events.

[0116] In one embodiment, the fault type determination module is further configured to:

[0117] Determine whether the zero-sequence voltage is less than the preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than the preset frequency difference. If the zero-sequence voltage is greater than or equal to the preset voltage, determine that the fault type is a unidirectional frequency abnormality accident.

[0118] If the frequency deviation is greater than the preset frequency difference, the fault type is determined to be a non-unidirectional frequency abnormality accident; if the frequency deviation is less than or equal to the preset frequency difference, the fault type is determined to be a unidirectional frequency abnormality accident.

[0119] In one embodiment, the active droop coefficient modification module is further used for:

[0120] The product of the frequency variation rate and the frequency deviation is taken as the frequency deviation variation trend;

[0121] If the frequency deviation change trend is less than zero, the initial active power droop coefficient is inverted to serve as the new active power droop coefficient.

[0122] In one embodiment, the active power change acquisition module is further used for:

[0123] Obtain the virtual inertia coefficient, and obtain the compensation value of the virtual inertia control based on the change rate of the frequency change and the virtual inertia coefficient;

[0124] Based on the new active droop coefficient and the frequency deviation, a compensation value of the first virtual droop control is obtained;

[0125] The sum of the compensation value of the first virtual droop control and the compensation value of the virtual inertia control is taken as the change in active power.

[0126] In one embodiment, after determining that the fault type is a unidirectional frequency abnormality accident or if the frequency deviation change trend is greater than or equal to zero, the active power change amount acquisition module is further used to:

[0127] Obtain the virtual inertia coefficient, and obtain the compensation value of the virtual inertia control based on the change rate of the frequency change and the virtual inertia coefficient;

[0128] Based on the initial active power droop coefficient and the frequency deviation, a compensation value of the second virtual droop control is obtained;

[0129] The sum of the compensation value of the second virtual droop control and the compensation value of the virtual inertia control is taken as the change in active power.

[0130] In one embodiment, the frequency acquisition module is further used to obtain the frequency of the power system using the following method:

[0131]

[0132] Where J is the moment of inertia, is the rate of change of frequency change, ΔP is the change of active power, D p is the damping coefficient, ω ref is the rated angular frequency of the power system, and f is the frequency of the power system.

[0133] According to an embodiment of the present invention, a storage medium is provided, wherein the storage medium stores at least one executable instruction, and the computer executable instruction can execute the frequency control method of the optical storage system in any of the above method embodiments.

[0134] Figure 8 A schematic diagram of the structure of a computer device provided according to an embodiment of the present invention is shown. The specific embodiment of the present invention does not limit the specific implementation of the computer device.

[0135] like Figure 8 As shown, the computer device may include: a processor (processor) 802 , a communication interface (Communications Interface) 804 , a memory (memory) 806 , and a communication bus 808 .

[0136] The processor 802 , the communication interface 804 , and the memory 806 communicate with each other via a communication bus 808 .

[0137] The communication interface 804 is used to communicate with other devices such as clients or other servers.

[0138] The processor 802 is used to execute the program 810, and specifically can execute the relevant steps in the above-mentioned embodiment of the frequency control method of the optical storage system.

[0139] Specifically, the program 810 may include program codes, which include computer operation instructions.

[0140] The processor 802 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention. The one or more processors included in the computer device may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0141] The memory 806 is used to store the program 810. The memory 806 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0142] The program 810 may be specifically configured to enable the processor 802 to perform the following operations:

[0143] Monitor the actual frequency in the power system, and when it is detected that the actual frequency is not equal to the rated frequency, obtain the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system, and determine the fault type based on the zero-sequence voltage and frequency deviation, wherein the power system includes the photovoltaic storage system and the power grid system;

[0144] When the fault type is a non-unidirectional frequency abnormality accident, the change rate of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained, and the frequency deviation change trend amount is obtained based on the change rate of the frequency change amount and the frequency deviation. Based on the frequency deviation change trend amount, the active power droop coefficient is modified to obtain a new active power droop coefficient;

[0145] Based on the change rate of the frequency change, the frequency deviation and the new active droop coefficient, the change of active power is obtained. The change of active power is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur;

[0146] Based on the variation of active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained.

[0147] Obviously, those skilled in the art should understand that the above modules or steps of the present invention can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices. In one embodiment, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order than here, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present invention is not limited to any specific combination of hardware and software.

[0148] The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application. The protection scope of the present application is defined by the claims. Those skilled in the art may make various modifications or equivalent substitutions to the present application within the essence and protection scope of the present application, and such modifications or equivalent substitutions shall also be deemed to fall within the protection scope of the present application.

Claims

1. A frequency control method for an optical storage system, characterized in that: include: The actual frequency of the power system is monitored, and when it is monitored that the actual frequency is not equal to the rated frequency, a frequency deviation between the actual frequency and the rated frequency, and a zero-sequence voltage at a grid connection point of a photovoltaic storage system and a grid system are obtained, and the fault type is determined based on the zero-sequence voltage and the frequency deviation, wherein the power system includes a photovoltaic storage system and a grid system; When the fault type is a non-unidirectional frequency abnormality accident, the change rate of the frequency change amount after the non-unidirectional frequency abnormality accident occurs in the power system is obtained, based on the change rate of the frequency change amount and the frequency deviation, the frequency deviation change trend amount is obtained, and based on the frequency deviation change trend amount, the active power droop coefficient is modified to obtain a new active power droop coefficient; Based on the rate of change of the frequency change, the frequency deviation and the new active droop coefficient, the change of active power is obtained, and the change of active power is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur; Based on the change in active power and the active power-frequency control method of the virtual synchronous generator, the frequency of the power system is obtained.

2. The frequency control method of the optical storage system according to claim 1, characterized in that: The determining of the fault type based on the zero-sequence voltage and the frequency deviation includes: Determine whether the zero-sequence voltage is less than a preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than a preset frequency difference. If the zero-sequence voltage is greater than or equal to the preset voltage, determine that the fault type is a unidirectional frequency abnormality accident. If the frequency deviation is greater than the preset frequency difference, the fault type is determined to be a non-unidirectional frequency abnormality accident; if the frequency deviation is less than or equal to the preset frequency difference, the fault type is determined to be a unidirectional frequency abnormality accident.

3. The frequency control method of the optical storage system according to claim 2, characterized in that: The method of obtaining a frequency deviation change trend amount based on the change rate of the frequency change amount and the frequency deviation, and modifying the active power droop coefficient based on the frequency deviation change trend amount to obtain a new active power droop coefficient includes: The product of the rate of change of the frequency change amount and the frequency deviation is used as the frequency deviation change trend amount; If the frequency deviation change trend amount is less than zero, the initial active power droop coefficient is inverted to serve as a new active power droop coefficient.

4. The frequency control method of the optical storage system according to claim 3, characterized in that: The step of obtaining the change in active power based on the change rate of the frequency change, the frequency deviation and the new active power droop coefficient includes: Acquire a virtual inertia coefficient, and obtain a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient; Based on the new active droop coefficient and the frequency deviation, obtaining a compensation value of a first virtual droop control; The sum of the compensation value of the first virtual droop control and the compensation value of the virtual inertia control is taken as the change in active power.

5. The frequency control method of the optical storage system according to claim 3, characterized in that: After determining that the fault type is a unidirectional frequency abnormality accident or if the frequency deviation change trend amount is greater than or equal to zero, the frequency control method of the photovoltaic storage system further includes: Acquire a virtual inertia coefficient, and obtain a compensation value of virtual inertia control based on the rate of change of the frequency change and the virtual inertia coefficient; Based on the initial active power droop coefficient and the frequency deviation, obtaining a compensation value for a second virtual droop control; The sum of the compensation value of the second virtual droop control and the compensation value of the virtual inertia control is used as the change in active power.

6. The frequency control method of the optical storage system according to claim 1, characterized in that: The active power-frequency control method based on the change in active power and the virtual synchronous generator uses the following method to obtain the frequency of the power system: Where J is the moment of inertia, is the rate of change of frequency change, ΔP is the change of active power, D p is the damping coefficient, ω ref is the rated angular frequency of the power system, and f is the frequency of the power system.

7. A frequency control device for an optical storage system, characterized in that: include: A fault type determination module is used to monitor the actual frequency of the power system, and when it is monitored that the actual frequency is not equal to the rated frequency, obtain the frequency deviation between the actual frequency and the rated frequency, and the zero-sequence voltage at the grid connection point of the photovoltaic storage system and the power grid system, and determine the fault type based on the zero-sequence voltage and the frequency deviation, wherein the power system includes the photovoltaic storage system and the power grid system; An active droop coefficient modification module is used for, when the fault type is a non-unidirectional frequency abnormality accident, obtaining a change rate of a frequency change amount after a non-unidirectional frequency abnormality accident occurs in the power system, obtaining a frequency deviation change trend amount based on the change rate of the frequency change amount and the frequency deviation, and modifying an active droop coefficient based on the frequency deviation change trend amount to obtain a new active droop coefficient; An active power change acquisition module, used to obtain the active power change based on the change rate of the frequency change, the frequency deviation and the new active droop coefficient, wherein the active power change is the difference between the active power output at the grid connection point after the non-unidirectional frequency abnormality accident occurs and the active power expected to be output at the grid connection point when the non-unidirectional frequency abnormality accident does not occur; The frequency acquisition module is used to obtain the frequency of the power system based on the change in active power and the active power-frequency control method of the virtual synchronous generator.

8. The frequency control device of the optical storage system according to claim 7, characterized in that: The fault type determination module is also used for: Determine whether the zero-sequence voltage is less than a preset voltage. If the zero-sequence voltage is less than the preset voltage, determine whether the frequency deviation is greater than a preset frequency difference. If the zero-sequence voltage is greater than or equal to the preset voltage, determine that the fault type is a unidirectional frequency abnormality accident. If the frequency deviation is greater than the preset frequency difference, the fault type is determined to be a non-unidirectional frequency abnormality accident; if the frequency deviation is less than or equal to the preset frequency difference, the fault type is determined to be a unidirectional frequency abnormality accident.

9. A storage medium, wherein at least one executable instruction is stored in the storage medium, wherein the executable instruction enables a processor to execute an operation corresponding to the frequency control method of an optical storage system according to any one of claims 1 to 6.

10. A computer device comprising: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, and the executable instruction enables the processor to perform operations corresponding to the frequency control method of the photovoltaic storage system according to any one of claims 1-6.

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