Frequency control method for wind-light-water storage micro-grid system

Abstract

The invention provides a frequency control method for a wind-light-water storage micro-grid system, and belongs to the technical field of new energy grid-connected power generation. The control method comprises photovoltaic power frequency partition control with lower limit power maintenance, wind power frequency partition control with lower limit power maintenance, energy storage system power frequency partition control and wind, light and water storage micro-grid system power frequency partition control. The method can be applied to a wind-light-water-storage multi-energy complementary micro-grid system, the synchronous rotation generator unit and the power electronic generation unit jointly participate in system frequency control, a multi-stage Droop control mode with higher stability is realized, a minimum lower limit power output interval is added in a program of the multi-stage Droop control mode, and the stability of the multi-stage Droop control mode is improved. The photovoltaic and wind power generation utilization rate is improved, and the micro-grid power supply system is more stable, more efficient and more flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of renewable energy grid-connected power generation, and specifically to a frequency control method for a wind, solar, and water storage microgrid system. Background Art

[0002] Due to the randomness, volatility and intermittency of wind and solar power output, the reliability and economy of the system are poor when they are used alone for power supply. Even the wind-solar complementary system needs to be equipped with a large-capacity energy storage device. Considering that hydropower units have the characteristics of rapid start-up, flexible adjustment and fast load response, they can quickly compensate and adjust the system frequency changes. Therefore, systematic research on frequency stability control of wind-solar-hydropower microgrid systems is both an engineering need and a need for theoretical development.

[0003] At present, independent microgrid frequency regulation technologies at home and abroad are divided into the following categories:

[0004] 1. Master-slave control, which is characterized by the presence of a master control unit and a slave control unit in the microgrid system. At the same time, a fast communication network is configured, and the master controller performs system-level coordinated control of other slave control units to maintain the stable operation of the microgrid system. When the microgrid is connected to the grid, all micro sources in the system adopt a constant power P / Q control strategy, and output constant reactive power, active power and stable voltage and frequency according to the system dispatch instructions. In off-grid mode, the master control unit must be able to quickly and smoothly switch to a constant voltage and frequency V / F mode to adjust the grid voltage and frequency, while the slave control unit still operates in P / Q mode and does not participate in the frequency and voltage regulation of the system. In summary, in the on-grid and off-grid operation modes, the control strategy adopted by the master control unit needs to be changed accordingly, so there is a possibility of failure in the operation mode switching.

[0005] 2. Peer control, which generally adopts a plug-and-play control method. In the absence of communication or weak communication connection, the micro-source relies on the control of local information to achieve stable operation of the microgrid. The main features of this control structure are plug-and-play and peer-to-peer, that is, all micro-sources in the microgrid are equal, and there is no master-slave control relationship. However, since the control is essentially subject to differential control and does not involve the recovery control of the frequency and voltage amplitude of the system, when the system is severely disturbed, the frequency and voltage amplitude of the microgrid will be greatly impacted, compromising the power quality and power supply stability of the system. On the other hand, this solution is mainly applicable to micro-sources with inverter interfaces, and its applicability to traditional power generation units such as synchronous generators and gas turbines needs further research and verification.

[0006] In addition, current microgrid frequency regulation technologies do not involve lower-limit power retention design, which can usually provide a basic stable output, so that the system has a certain buffering capacity when facing emergencies. Without a lower-limit power retention design, the system may not be able to guarantee power supply during peak load periods or low output periods of renewable energy. Therefore, the energy management system requires more complex algorithms and control strategies to balance multiple energy sources and loads in real time, which further leads to the need for energy storage systems to frequently perform charging and discharging operations to balance supply and demand. Frequent energy storage charging and discharging operations not only increase equipment wear and maintenance costs, but may also lead to reduced energy utilization efficiency. These deficiencies need to be improved urgently.

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a frequency control method for a wind-solar-water-storage microgrid system, which can be applied to a wind-solar-water-storage multi-energy complementary microgrid system, and utilizes a synchronous rotating generator unit and a power electronic generating unit to jointly participate in the system frequency control, thereby achieving a more stable multi-stage Dr oo p control mode, and adds a minimum lower limit power output range in the program of the multi-stage Droop control mode, which improves the power generation utilization rate of photovoltaic and wind power, making the microgrid power supply system more stable, efficient and flexible. Summary of the invention

[0008] The technical problem to be solved by the present invention is the deficiency of the above-mentioned prior art. The present invention provides a frequency control method for a wind, solar, and hydropower storage microgrid system, which can be applied to a wind, solar, and hydropower storage multi-energy complementary microgrid system. The frequency control part of the system includes two parts: a synchronous rotating generator unit and a power electronic generation unit, which effectively ensures high-quality power supply of the system.

[0009] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical scheme:

[0010] A frequency control method for a wind-solar-water-storage microgrid system, wherein the wind-solar-water-storage microgrid system comprises a photovoltaic power generation system, a wind power generation system, a hydropower generation system and an energy storage system, and each system is connected to a power grid via a grid-connected inverter. The hydropower generation system comprises a turbine set and a turbine set speed governor. The control method comprises the following steps:

[0011] Step 1, photovoltaic power frequency partition control with lower limit power maintenance;

[0012] Step 2: Wind power frequency partition control with lower power limit maintenance;

[0013] Step 3: Power frequency partition control of energy storage system;

[0014] Step 4: Power and frequency zoning control of wind, solar, water and storage microgrid systems.

[0015] Preferably, the implementation process of step 1 is as follows:

[0016] First define the following parameters: t_pv is the operating frequency of the photovoltaic power generation system at time t, f min_pv is the minimum operating frequency of the photovoltaic power generation system, f 1_pv is the inflection point value of the maximum upper limit active power droop frequency of the photovoltaic power generation system, f 2_pv is the first inflection point value of the active standby power frequency of the photovoltaic power generation system, f 3_pv is the second inflection point value of the active standby power frequency of the photovoltaic power generation system, f 4_pv is the minimum lower limit power droop frequency inflection point value of the photovoltaic power generation system, f max_pv is the maximum operating frequency of the photovoltaic power generation system, f n_pv is the rated operating frequency of the photovoltaic power generation system, and f min_pv <f 1_pv <f 2_pv <f n_pv <f 3_pv <f 4_pv <f max_pv ;

[0017] The photovoltaic power frequency partition control with lower limit power maintenance is performed in the following manner;

[0018] When f t_pv <f min_pv When , the photovoltaic grid-connected inverter starts under-frequency protection and exits operation;

[0019] When f min_pv f t_pv ≤f 1_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the maximum upper limit power setting value P re_pv_max run;

[0020] When f 1_pv <f t_pv <f 2_pv When the photovoltaic grid-connected inverter performs the first Droop mode frequency modulation, the photovoltaic power generation system uses the photovoltaic grid-connected inverter first frequency modulation active power given value P re_pv_1 run:

[0021] When f 2_pv ≤f t_pv ≤f 3_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the active standby power of the photovoltaic grid-connected inverter is set to P re_pv_st run;

[0022] When f 3_pv <f t_pv <f 4_pvWhen the photovoltaic grid-connected inverter performs the second frequency modulation in the Droop mode, the photovoltaic power generation system uses the second frequency modulation active power given value P of the photovoltaic grid-connected inverter. re_pv_2 run;

[0023] When f 4_pv ≤f t_pv ≤f max_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the minimum lower limit power given value P re_pv_min run;

[0024] When f t_pv >f max_pv When the over-frequency protection is activated, the photovoltaic grid-connected inverter will exit operation.

[0025] Preferably, the maximum upper limit power setting value P of the photovoltaic grid-connected inverter re_pv_max The expression is:

[0026] P re_pv_max =P re_MPPT_pv

[0027] Among them, P re_MPPT_pv It is the maximum active power tracking value of the photovoltaic grid-connected inverter;

[0028] The first frequency modulation active power given value P of the photovoltaic grid-connected inverter re_pv_1 The expression is:

[0029] P re_pv_1 =P re_MPPT_pv +k pv ×P re_MPPT_pv ×(f t_pv -f 1_pv )

[0030] Among them, k pv is the power frequency droop coefficient of the photovoltaic grid-connected inverter;

[0031] The active standby power given value P of the photovoltaic grid-connected inverter re_pv_st The expression is:

[0032] P re_pv_st =0.9×P re_MPPT_pv

[0033] The second frequency modulation active power given value P of the photovoltaic grid-connected inverter re_pv_2 The expression is:

[0034] P re_pv_2 =P re_pv_st +k pv ×P re_MPPT_pv ×(f t_pv -f 3_pv )

[0035] The minimum lower limit power given value P of the photovoltaic grid-connected inverter re_pv_min The expression is:

[0036] P re_pv_min =0.1×P re_MPPT_pv .

[0037] Preferably, the implementation process of step 2 is as follows:

[0038] First define the following parameters: t_wp is the operating frequency of the wind power generation system at time t, f min_wp is the minimum operating frequency of the wind power generation system, f 1_wp is the inflection point value of the maximum upper limit active power droop frequency of the wind power grid-connected inverter, f 2_wp is the first inflection point value of the active standby power frequency of the wind power grid-connected inverter, f 3_wp is the second inflection point value of the active standby power frequency of the wind power grid-connected inverter, f 4_wp is the frequency inflection point value of the minimum lower limit power mode of the wind power grid-connected inverter, f max_wp is the maximum operating frequency of the wind power generation system, f n is the rated operating frequency of the wind power generation system, and f min_wp <f 1_wp <f 2_wp <f n_wp <f 3_wp <f 4_wp <f max_wp ;

[0039] The wind power generation system comprises a wind power generator set;

[0040] The wind power frequency partition control with lower power limit maintenance is performed in the following manner:

[0041] When f t_wp <f min_wp When the wind power grid-connected inverter starts under-frequency protection and exits operation;

[0042] When f min_wp ≤f t _ wp ≤f 1_wp When the wind turbine generator set is connected to the wind power grid, the maximum upper limit power setting value P re_wp_max run;

[0043] When f 1_wp <f t_wp <f 2_wpWhen the wind power grid-connected inverter performs the first Droop mode frequency modulation, the wind turbine generator set uses the wind power grid-connected inverter first frequency modulation active power given value P re_wp_1 run:

[0044] When f 2_wp ≤f t_wp ≤f 3_wp When the wind turbine generator set is connected to the wind power grid, the active reserve power of the inverter is set to P re_wp_st run:

[0045] When f 3_wp <f t_wp <f 4_wp When the wind power grid-connected inverter performs the second frequency modulation in the Droop mode, the wind turbine generator set uses the second frequency modulation active power given value P of the wind power grid-connected inverter. re_wp_2 run:

[0046] When f 4_wp ≤f t_wp ≤f max_wp When the wind turbine generator set is connected to the wind power grid, the minimum lower limit power setting value P re_wp_min run:

[0047] When f t_wp >f max_wp When the wind power grid-connected inverter starts over-frequency protection and exits operation.

[0048] Preferably, the maximum upper limit power setting value P of the wind power grid-connected inverter is re_wp_max The expression is:

[0049] P re_wp_max =P re_MPPT_wp

[0050] Among them, P re_MPPT_wp It is the maximum active power tracking value of the wind power grid-connected inverter;

[0051] The first frequency modulation active power given value P of the wind power grid-connected inverter re_wp_1 The expression is:

[0052] P re_wp_t =P re_MPPT_wp +k wp ×P re_MPPT_wp ×(f t_wp -f 1_wp )

[0053] where k wp is the power frequency droop coefficient of the wind power grid-connected inverter;

[0054] The active standby power given value P of the wind power grid-connected inverter re_wp_st The expression is:

[0055] P re_wp_st =0.9×P re_MPPT_wp

[0056] The second frequency modulation active power given value P of the wind power grid-connected inverter re_wp_2 The expression is:

[0057] P re_wp_2 =P re_wp_st +k wp ×P re_MPPT_wp ×(f t_wp -f 3_wp )

[0058] The minimum lower limit power given value P of the wind power grid-connected inverter re_wp_min The expression is:

[0059] P re_wp_min =0.1×P re_MPPT_wp .

[0060] Preferably, the implementation process of step 3 is as follows:

[0061] First define the following parameters: t_es is the operating frequency of the energy storage system at time t, P t_es is the active power of the energy storage system at time t, f min_es is the minimum operating frequency of the energy storage system, f 1_es is the inflection point value of the maximum upper limit active power droop frequency of the energy storage system, f 2_es is the first frequency inflection point value of the variable droop coefficient of the energy storage system, f 3_es is the second frequency inflection point value of the variable droop coefficient of the energy storage system, f 4_es is the inflection point value of the minimum lower limit active power droop frequency of the energy storage system, f max_es is the maximum operating frequency of the energy storage system, f n_es is the rated operating frequency of the energy storage system, P es_max is the maximum upper limit power given value of the energy storage grid-connected inverter, and has f min_es <f 1_es <f 2_es <f n_es <f 3_es <f 4_es <f max_es relationship;

[0062] The power frequency partition control of the energy storage grid-connected inverter is performed in the following manner:

[0063] When f t_es <fmin_es When the inverter is connected to the energy storage grid, the under-frequency protection is activated and the inverter exits operation;

[0064] When f min_es ≤f t_es ≤f 1_es When the energy storage system is connected to the grid, the maximum upper limit power of the energy storage inverter is given by P re_es_max run;

[0065] When f 1_es <f t_es <f 2_es When the energy storage grid-connected inverter performs the first Droop mode frequency modulation, the energy storage system uses the energy storage grid-connected inverter first frequency modulation active power given value P re_es_1 run;

[0066] When f 2_es <f t_es <f 3_es When the energy storage grid-connected inverter performs the second frequency modulation in the Droop mode, the energy storage system uses the second frequency modulation active power given value P of the energy storage grid-connected inverter. re_es_2 run;

[0067] When f 3_es <f t_es <f 4_es When the energy storage grid-connected inverter performs the third frequency modulation in the Droop mode, the energy storage system uses the third frequency modulation active power given value P of the energy storage grid-connected inverter. re_es_3 run;

[0068] When f 4_es ≤f t_es ≤f max_es When the energy storage system is connected to the grid, the minimum lower limit power of the energy storage inverter is given by P re_es_min run;

[0069] When the frequency f t_es >f max_es When the over-frequency protection is activated, the energy storage grid-connected inverter will exit operation.

[0070] Preferably, the maximum upper limit power setting value P of the energy storage grid-connected inverter re_es_max The expression is:

[0071] P re_es_max =P s1

[0072] Among them, P s1 is the maximum output power of the energy storage system;

[0073] The first frequency modulation active power given value P of the energy storage grid-connected inverter re_es_1 The expression is:

[0074] P re_es_1 =P s1 +k es1 ×P s1 ×(f t_es -f 1_es )

[0075] Among them, k es1 is the first power frequency droop coefficient of the energy storage grid-connected inverter;

[0076] The second frequency modulation active power given value P of the energy storage grid-connected inverter re_es_2 The expression is:

[0077] P re_es_2 =P s2 +k es2 ×P s1 ×(f t_es -f 2_es )

[0078] Among them, k es2 is the second power frequency droop coefficient of the energy storage grid-connected inverter, P s2 The first power inflection point value of the variable droop coefficient of the energy storage grid-connected inverter;

[0079] The third frequency modulation active power given value P of the energy storage grid-connected inverter re_es_3 The expression is:

[0080] Pr e_es_3 =-P s2 +k es1 ×P s1 ×(f t_es -f 3_es )

[0081] The minimum lower limit power setting value P of the energy storage grid-connected inverter re_es_min The expression is:

[0082] P re_es_min =-P s1 .

[0083] Preferably, the power frequency zoning control of the wind, solar, and water storage microgrid system described in step 4 includes the following situations:

[0084] The turbine speed governor controls the turbine opening to control the turbine output power frequency. The hydropower generation system participates in the frequency control of the wind, solar, and water storage power supply system throughout the process.

[0085] When f1<f t_es When <f6, the energy storage system dynamically adjusts the frequency modulation coefficient according to the output power;

[0086] When f min ≤ft_es ≤f1 or f6≤f t_es ≤f max When , the energy storage system exits frequency control;

[0087] When f1<f t_pv <f2 or f s <f t_pv When <f6, the photovoltaic power generation system participates in frequency modulation with a constant frequency modulation coefficient;

[0088] When f6≤f t_pv ≤f max When the photovoltaic power generation system is connected to the photovoltaic grid, the minimum lower limit power given value P re_pv_min Operation, the power generation is mainly used to charge the energy storage system;

[0089] When f2<f t_wp <f3 or f4 <f t_wp When <f5, the wind power generation system participates in frequency regulation with a constant frequency regulation coefficient;

[0090] When f6≤f t_wp ≤f max When the wind power generation system is connected to the wind power grid, the minimum lower limit power setting value P re_wp_min Operation, the power generation is mainly used to charge the energy storage system;

[0091] Among them, f1 is the frequency inflection point value from the hydropower system switching from single frequency regulation to the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation; f2 is the frequency inflection point value from the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation to the hydropower system, wind power generation system and energy storage system joint frequency regulation; f3 is the frequency inflection point value from the hydropower system, wind power generation system and energy storage system joint frequency regulation to the energy storage system and hydropower system joint frequency regulation; f4 is the frequency inflection point value from the energy storage system and hydropower system joint frequency regulation to the hydropower system, wind power generation system and energy storage system joint frequency regulation; f5 is the frequency inflection point value from the hydropower system, wind power generation system and energy storage system joint frequency regulation to the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation; f6 is the frequency inflection point value from the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation to the hydropower system single frequency regulation; f max is the maximum operating frequency of the wind, solar, water and storage microgrid system; f min It is the minimum operating frequency of the wind, solar, water and storage microgrid system.

[0092] Compared with the prior art, the present invention has the following beneficial effects:

[0093] A frequency control method for a wind, solar, and water storage microgrid system is a distributed control method that relies on locally measured voltage and frequency for adjustment. It does not require a central controller and a complex communication network, and can automatically distribute power according to load changes, ensuring that each power source can evenly bear the load changes and improve system stability. The method has a multi-stage Droop control mode, which can adapt to disturbances and uncertainties in the power system and has stronger stability. A minimum lower limit power output interval is added to the program of the multi-stage Droop control mode. The power generation in this interval is mainly used to charge the energy storage system, which improves the power generation utilization rate of photovoltaic and wind power. The method is easy to expand, can easily add new power sources or loads, and adapt to the access of multiple energy sources (such as solar energy, wind energy, energy storage, etc.) in a multi-energy complementary system. In summary, a frequency control method for a wind, solar, and water storage microgrid system has significant advantages in a multi-energy complementary microgrid power supply system, making the power supply system more stable, more efficient and more flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 It is a flow chart of the frequency control method of the wind-solar-water-storage microgrid system of the present invention;

[0095] Figure 2 It is a structural diagram of a wind-solar-water-storage microgrid system in an embodiment of the present invention;

[0096] Figure 3 Schematic diagram of photovoltaic power frequency zoning control in an embodiment of the present invention;

[0097] Figure 4 Schematic diagram of wind power frequency zoning control in an embodiment of the present invention;

[0098] Figure 5 Schematic diagram of power frequency partition control of energy storage system in an embodiment of the present invention;

[0099] Figure 6 Schematic diagram of power frequency zoning control of wind, solar, and water storage microgrid system in an embodiment of the present invention;

[0100] Figure 7 is an active power simulation diagram of a photovoltaic power generation system in an embodiment of the present invention;

[0101] Figure 8 is an active power simulation diagram of a wind power generation system in an embodiment of the present invention;

[0102] Fig. 9 is an active power simulation diagram of the energy storage system in an embodiment of the present invention;

[0103] Fig.10 is an active power simulation diagram of a hydroelectric power generation system in an embodiment of the present invention;

[0104] Fig.11It is a frequency simulation diagram of the wind, solar, and water storage microgrid system in an embodiment of the present invention. DETAILED DESCRIPTION

[0105] The present invention is described in detail below with reference to the accompanying drawings.

[0106] Figure 2 This is a structural diagram of the wind-solar-water-storage microgrid system in an embodiment of the present invention. It can be seen from the figure that the wind-solar-water-storage microgrid system includes a photovoltaic power generation system, a wind power generation system, a hydropower generation system and an energy storage system, and each system is connected to the power grid through a grid-connected inverter. In addition, the hydropower generation system includes a turbine set and a turbine set speed governor.

[0107] Specifically, the parameters in this embodiment are as follows: the capacity of the photovoltaic generator set is 100kW, the capacity of the wind generator set is 45kW, the capacity of the energy storage unit is 20kW, the capacity of the hydroelectric generator set is 96.7kW, and the rated operating frequency of the microgrid system is fn=50Hz.

[0108] Figure 1 : is a flow chart of the frequency control method of the wind-solar-water-storage microgrid system provided by the present invention. As can be seen from the figure, the power frequency partition control method of the wind-solar-water-storage microgrid system provided by the present invention includes the following steps:

[0109] Step 1, photovoltaic power frequency partition control with lower limit power maintenance;

[0110] Step 2: Wind power frequency partition control with lower power limit maintenance;

[0111] Step 3: Power frequency partition control of energy storage system;

[0112] Step 4: Power and frequency zoning control of wind, solar, water and storage microgrid systems.

[0113] In this embodiment, the implementation process of step 1 is as follows:

[0114] First define the following parameters: t_pv is the operating frequency of the photovoltaic power generation system at time t, f min_pv is the minimum operating frequency of the photovoltaic power generation system, f 1_pv is the inflection point value of the maximum upper limit active power droop frequency of the photovoltaic power generation system, f 2_pv is the first inflection point value of the active standby power frequency of the photovoltaic power generation system, f 3_pv is the second inflection point value of the active standby power frequency of the photovoltaic power generation system, f 4_pv is the minimum lower limit power droop frequency inflection point value of the photovoltaic power generation system, f max_pv is the maximum operating frequency of the photovoltaic power generation system, f n_pv is the rated operating frequency of the photovoltaic power generation system, and f min_pv <f1_pv <f 2_pv <f n_pv <f 3_pv <f 4_pv <f max_pv .

[0115] The photovoltaic power frequency partition control with lower limit power maintenance is performed in the following manner;

[0116] When f t_pv <f min_pv When , the photovoltaic grid-connected inverter starts under-frequency protection and exits operation;

[0117] When f min_pv ≤f t_pv ≤f 1_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the maximum upper limit power setting value P re_pv_max run;

[0118] When f 1_pv <f t_pv <f 2_pv When the photovoltaic grid-connected inverter performs the first Droop mode frequency modulation, the photovoltaic power generation system uses the photovoltaic grid-connected inverter first frequency modulation active power given value P re_pv_1 run:

[0119] When f 2_pv ≤f t_pv ≤f 3_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the active standby power of the photovoltaic grid-connected inverter is set to P re_pv_st run;

[0120] When f 3_pv <f t_pv <f 4_pv When the photovoltaic grid-connected inverter performs the second frequency modulation in the Droop mode, the photovoltaic power generation system uses the second frequency modulation active power given value P of the photovoltaic grid-connected inverter. re_pv_2 run;

[0121] When f 4_pv ≤f t_pv ≤f max_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the minimum lower limit power given value P re_pv_min run;

[0122] When f t_pv >f max_pv When the over-frequency protection is activated, the photovoltaic grid-connected inverter will exit operation.

[0123] In this embodiment, the maximum upper limit power setting value P of the photovoltaic grid-connected inverter is re_pv_max The expression is:

[0124] P re_pv_max =P re_MPPT_pv

[0125] Among them, P re_MPPT_pv It is the maximum active power tracking value of the photovoltaic grid-connected inverter;

[0126] The first frequency modulation active power given value P of the photovoltaic grid-connected inverter re_pv_1 The expression is:

[0127] P re_pv_1 =P re_MPPT_pv +k pv ×P re_MPPT_pv ×(f t_pv -f 1_pv )

[0128] Among them, k pv is the power frequency droop coefficient of the photovoltaic grid-connected inverter; and when f t_pv =f 2_pv When P re_pv_1 =0.9×P re_MPPT_pv ;

[0129] The active standby power given value P of the photovoltaic grid-connected inverter re_pv_st The expression is:

[0130] P re_pv_st =0.9×P re_MPPT_pv

[0131] The second frequency modulation active power given value P of the photovoltaic grid-connected inverter re_pv_2 The expression is:

[0132] P re_pv_2 =P re_pv_st +k pv ×P re_MPPT_pv ×(f t_pv -f 3_pv )

[0133] And when f t_pv =f 4_pv When P re_pv_2 =0.1×P re_MPPT_pv ;

[0134] The minimum lower limit power given value P of the photovoltaic grid-connected inverter re_pv_min The expression is:

[0135] P re_pv_min =0.1×P re_MPPT_pv .

[0136] Figure 3 It is a schematic diagram of photovoltaic power frequency zoning control in an embodiment of the present invention.

[0137] In this embodiment, the implementation process of step 2 is as follows:

[0138] First define the following parameters: t_wp is the operating frequency of the wind power generation system at time t, f min_wp is the minimum operating frequency of the wind power generation system, f 1_wp is the inflection point value of the maximum upper limit active power droop frequency of the wind power grid-connected inverter, f 2_wp is the first inflection point value of the active standby power frequency of the wind power grid-connected inverter, f 3_wp is the second inflection point value of the active standby power frequency of the wind power grid-connected inverter, f 4_wp is the frequency inflection point value of the minimum lower limit power mode of the wind power grid-connected inverter, f max_wp is the maximum operating frequency of the wind power generation system, f n is the rated operating frequency of the wind power generation system, and f min_wp <f 1_wp <f 2_wp <f n_wp <f 3_wp <f 4_wp <f max_wp .

[0139] The wind power generation system comprises a wind power generator set;

[0140] The wind power frequency partition control with lower power limit maintenance is performed in the following manner:

[0141] When f t_wp <f min_wp When the wind power grid-connected inverter starts under-frequency protection and exits operation;

[0142] When f min_wp ≤f t_wp ≤f 1_wp When the wind turbine generator set is connected to the wind power grid, the maximum upper limit power setting value P re_wp_max run;

[0143] When f 1_wp <f t_wp <f 2_wp When the wind power grid-connected inverter performs the first Droop mode frequency modulation, the wind turbine generator set uses the wind power grid-connected inverter first frequency modulation active power given value P re_wp_1 run:

[0144] When f 2_wp ≤f t_wp ≤f 3_wp When the wind turbine generator set is connected to the wind power grid, the active reserve power of the inverter is set to P re_wp_strun:

[0145] When f 3_wp <f t_wp <f 4_wp When the wind power grid-connected inverter performs the second frequency modulation in the Droop mode, the wind turbine generator set uses the second frequency modulation active power given value P of the wind power grid-connected inverter. re_wp_2 run:

[0146] When f 4_wp f t_wp ≤f max_wp When the wind turbine generator set is connected to the wind power grid, the minimum lower limit power setting value P re_wp_min run:

[0147] When f t_wp >f max_wp When the wind power grid-connected inverter starts over-frequency protection and exits operation.

[0148] In this embodiment, the maximum upper limit power setting value P of the wind power grid-connected inverter is re_wp_max The expression is:

[0149] P re_wp_max =P re_MPPT_wp

[0150] Among them, P re_MPPT_wp It is the maximum active power tracking value of the wind power grid-connected inverter;

[0151] The first frequency modulation active power given value P of the wind power grid-connected inverter re_wp_1 The expression is:

[0152] P re_wp_t =P re_MPPT_wp +k wp ×P re_MPPT_wp ×(f t_wp -f 1_wp )

[0153] where k wp is the power frequency droop coefficient of the wind power grid-connected inverter;

[0154] And when f t_wp =f 2_wp When P re_wp_t =0.9×P re_MPPT_wp ;

[0155] The active standby power given value P of the wind power grid-connected inverter re_wp_st The expression is:

[0156] P re_wp_st =0.9×P re_MPPT_wp

[0157] The second frequency modulation active power given value P of the wind power grid-connected inverter re_wp_2 The expression is:

[0158] P re_wp_2 =P re_wp_st +k wp ×P re_MPPT_wp ×(f t_wp -f 3_wp )

[0159] And when f t_wp =f 4_wp When P re_wp_2 =0.1×P re_MPPT_wp ;

[0160] The minimum lower limit power given value P of the wind power grid-connected inverter re_wp_min The expression is:

[0161] P re_wp_min =0.1×P re_MPPT_wp .

[0162] Figure 4 It is a schematic diagram of wind power frequency zoning control in an embodiment of the present invention.

[0163] In this embodiment, the implementation process of step 3 is as follows:

[0164] First define the following parameters: t_es is the operating frequency of the energy storage system at time t, P t_es is the active power of the energy storage system at time t, f min_es is the minimum operating frequency of the energy storage system, f 1_es is the inflection point value of the maximum upper limit active power droop frequency of the energy storage system, f 2_es is the first frequency inflection point value of the variable droop coefficient of the energy storage system, f 3_es is the second frequency inflection point value of the variable droop coefficient of the energy storage system, f 4_es is the inflection point value of the minimum lower limit active power droop frequency of the energy storage system, f max_es is the maximum operating frequency of the energy storage system, f n_es is the rated operating frequency of the energy storage system, P es_m ax is the maximum upper limit power given value of the energy storage grid-connected inverter, and has f min_es <f 1_es <f 2_es <f n_es <f 3_es <f 4_es <f max_es relationship.

[0165] The power frequency partition control of the energy storage grid-connected inverter is performed in the following manner:

[0166] When f t_es <f min_es When the inverter is connected to the energy storage grid, the under-frequency protection is activated and the inverter exits operation;

[0167] When f min_es ≤f t_es ≤f 1_es When the energy storage system is connected to the grid, the maximum upper limit power of the energy storage inverter is given by P re_es_max run;

[0168] When f 1_es <f t_es <f 2_es When the energy storage grid-connected inverter performs the first Droop mode frequency modulation, the energy storage system uses the energy storage grid-connected inverter first frequency modulation active power given value P re_es_1 run;

[0169] When f 2_es <f t_es <f 3_es When the energy storage grid-connected inverter performs the second frequency modulation in the Droop mode, the energy storage system uses the second frequency modulation active power given value P of the energy storage grid-connected inverter. re_es_2 run;

[0170] When f 3_es <f t_es <f 4_es When the energy storage grid-connected inverter performs the third frequency modulation in the Droop mode, the energy storage system uses the third frequency modulation active power given value P of the energy storage grid-connected inverter. re_es_3 run;

[0171] When f 4_es ≤f t_es ≤f max_es When the energy storage system is connected to the grid, the minimum lower limit power of the energy storage inverter is given by P re_es_min run;

[0172] When the frequency f t_es >f max_es When the over-frequency protection is activated, the energy storage grid-connected inverter will exit operation.

[0173] In this embodiment, the maximum upper limit power setting value P of the energy storage grid-connected inverter re_es_max The expression is:

[0174] P re_es_max =P s1

[0175] Among them, P s1 is the maximum output power of the energy storage system;

[0176] The first frequency modulation active power given value P of the energy storage grid-connected inverter re_es_1 The expression is:

[0177] P re_es_1 =P s1 +k es1 ×P s1 ×(f t_es -f 1_es )

[0178] Among them, k es1 is the first power frequency droop coefficient of the energy storage grid-connected inverter;

[0179] The second frequency modulation active power given value P of the energy storage grid-connected inverter re_es_2 The expression is:

[0180] P re_es_2 =P s2 +k es2 ×P s1 ×(f t_es -f 2_es )

[0181] Among them, k es2 is the second power frequency droop coefficient of the energy storage grid-connected inverter, P s2 The first power inflection point value of the variable droop coefficient of the energy storage grid-connected inverter;

[0182] The third frequency modulation active power given value P of the energy storage grid-connected inverter re_es_3 The expression is:

[0183] P re_es_3 =-P s2 +k es1 ×P s1 ×(f t_es -f 3_es )

[0184] The minimum lower limit power setting value P of the energy storage grid-connected inverter re_es_min The expression is:

[0185] P re_es_min =-P s1 .

[0186] Figure 5 It is a schematic diagram of power frequency zoning control of the energy storage system in an embodiment of the present invention.

[0187] In this embodiment, the power frequency partition control of the wind-solar-water-storage microgrid system described in step 4 includes the following situations:

[0188] The turbine speed governor controls the turbine opening to control the turbine output power frequency. The hydropower generation system participates in the frequency control of the wind, solar, and water storage power supply system throughout the process.

[0189] When f1<f t_es When <f6, the energy storage system dynamically adjusts the frequency modulation coefficient according to the output power;

[0190] When f min ≤f t_es ≤f1 or f6≤f t_es ≤f max When , the energy storage system exits frequency control;

[0191] When f1<f t_pv <f2 or f s <f t_pv When <f6, the photovoltaic power generation system participates in frequency modulation with a constant frequency modulation coefficient;

[0192] When f6≤f t_pv ≤f max When the photovoltaic power generation system is connected to the photovoltaic grid, the minimum lower limit power given value P re_pv_min Operation, the power generation is mainly used to charge the energy storage system;

[0193] When f2<f t_wp <f3 or f4 <f t_wp When <f5, the wind power generation system participates in frequency regulation with a constant frequency regulation coefficient;

[0194] When f6≤f t_wp ≤f max When the wind power generation system is connected to the wind power grid, the minimum lower limit power setting value P re_wp_min Operation, the power generation is mainly used to charge the energy storage system;

[0195] Among them, f1 is the frequency inflection point value from the hydropower system switching from single frequency regulation to the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation; f2 is the frequency inflection point value from the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation to the hydropower system, wind power generation system and energy storage system joint frequency regulation; f3 is the frequency inflection point value from the hydropower system, wind power generation system and energy storage system joint frequency regulation to the energy storage system and hydropower system joint frequency regulation; f4 is the frequency inflection point value from the energy storage system and hydropower system joint frequency regulation to the hydropower system, wind power generation system and energy storage system joint frequency regulation; f5 is the frequency inflection point value from the hydropower system, wind power generation system and energy storage system joint frequency regulation to the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation; f6 is the frequency inflection point value from the hydropower system, photovoltaic power generation system and energy storage system joint frequency regulation to the hydropower system single frequency regulation; f maxis the maximum operating frequency of the wind, solar, water and storage microgrid system; f min It is the minimum operating frequency of the wind, solar, water and storage microgrid system.

[0196] Figure 6 Schematic diagram of power frequency zoning control of wind, solar, and water storage microgrid system in an embodiment of the present invention;

[0197] To demonstrate the beneficial effects, simulations were performed.

[0198] The rated operating frequency of the microgrid system is fn=50Hz. The frequency of the microgrid begins to drop at 1s and drops to 49.5Hz at 6s (indicating an increase in load). The inverters of each subsystem adjust the output power according to the frequency change. Figure 7 , Figure 8 , Fig. 9 , Fig.10 and Fig.11 They are the active power waveform of the photovoltaic power generation system, the active power waveform of the wind power generation system, the active power waveform of the energy storage system, the active power waveform of the hydropower generation system and the simulated waveform of the frequency of the wind, solar, water and storage microgrid system when the frequency of the wind, solar, water and storage microgrid system drops from 50Hz to 49.5Hz.

[0199] In the simulation, the states of each system are as follows:

[0200] Photovoltaic grid-connected inverter: P re_pv_max =100kW, k pv =-0.5, P re_pv1 =0.9×100kW+0.5×100kW×(49.8Hz-49.6Hz), P re_pv2 =90kW+10kW=100kW, and the increased value of photovoltaic grid-connected power ΔP is obtained re_pv =10kW.

[0201] Wind power grid-connected inverter: P re_wp_max =45kW, k wp =-1, P re_wp1 =0.9×45kW+1×45kW×(49.6Hz-49.5Hz), P re_wp2 =40.5kW+4.5kW=45kW, and the wind power grid-connected power increase value ΔP is obtained re_wp =4.5kW.

[0202] Energy storage grid-connected inverter: P re_es =20kW, k es1 =-4, k es2 =-2 / 3, and the energy storage grid-connected power increase value ΔP is obtained re_es=4×20kW×(50Hz-49.8Hz)+2 / 3×20kW×(49.8Hz-49.5Hz)=20kW.

[0203] Hydropower grid-connected inverter: Maximum active power P of hydropower generator set re_hp_max =96.7kW, power frequency droop coefficient k of the hydroelectric generator set hp =-0.345, the grid-connected active power output value P of the hydroelectric generator set re_hp =0.83×96.7kW+0.345×96.7kW×(50Hz-49.5Hz), P re_hp =80kW+16.7kW=96.7kW, and the increased power of hydropower grid connection ΔP is obtained re_hp =16.7kW.

[0204] The total output power increases: ΔP = 10 kW + 4.5 kW + 20 kW + 16.7 kW = 51.2 kW.

[0205] It can be seen that by controlling the frequency modulation through power frequency partitioning, the inverter module effectively distributes the load changes and ensures the stability of the system frequency.

Claims

1. A frequency control method for a wind-solar-water-storage microgrid system, wherein the wind-solar-water-storage microgrid system comprises a photovoltaic power generation system, a wind power generation system, a hydropower generation system and an energy storage system, and each system is connected to the power grid through a grid-connected inverter, and the hydropower generation system comprises a turbine set and a turbine set speed governor, characterized in that: The control method comprises the following steps: Step 1, photovoltaic power frequency partition control with lower limit power maintenance; Step 2: Wind power frequency partition control with lower power limit maintenance; Step 3: Power frequency partition control of energy storage system; Step 4: Power and frequency zoning control of wind, solar, water and storage microgrid systems.

2. A wind-solar-water-storage microgrid system frequency control method according to claim 1, characterized in that: The implementation process of step 1 is as follows: First define the following parameters: t_pv is the operating frequency of the photovoltaic power generation system at time t, f min_pv is the minimum operating frequency of the photovoltaic power generation system, f 1_pv is the inflection point value of the maximum upper limit active power droop frequency of the photovoltaic power generation system, f 2_pv is the first inflection point value of the active standby power frequency of the photovoltaic power generation system, f 3_pv is the second inflection point value of the active standby power frequency of the photovoltaic power generation system, f 4_pv is the minimum lower limit power droop frequency inflection point value of the photovoltaic power generation system, f max_pv is the maximum operating frequency of the photovoltaic power generation system, f n_pv is the rated operating frequency of the photovoltaic power generation system, and f min_pv <f 1_pv <f 2_pv <f n_pv <f 3_pv <f 4_pv <f max_pv ; The photovoltaic power frequency partition control with lower limit power maintenance is performed in the following manner; When f t_pv <f min_pv When , the photovoltaic grid-connected inverter starts under-frequency protection and exits operation; When f min_pv ≤f t_pv ≤f 1_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the maximum upper limit power setting value P re_pv_max run; When f 1_pv <f t_pv <f 2_pv When the photovoltaic grid-connected inverter performs the first Droop mode frequency modulation, the photovoltaic power generation system uses the photovoltaic grid-connected inverter first frequency modulation active power given value P re_pv_1 run: When f 2_pv ≤f t_pv ≤f 3_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the active standby power of the photovoltaic grid-connected inverter is set to P re_pv_st run; When f 3_pv <f t_pv <f 4_pv When the photovoltaic grid-connected inverter performs the second frequency modulation in the Droop mode, the photovoltaic power generation system uses the second frequency modulation active power given value P of the photovoltaic grid-connected inverter. re_pv_2 run; When f 4_pv ≤f t_pv ≤f max_pv When the photovoltaic power generation system is connected to the photovoltaic grid, the minimum lower limit power given value P re_pv_min run; When f t_pv >f max_pv When the over-frequency protection is activated, the photovoltaic grid-connected inverter will exit operation.

3. A frequency control method for a wind-solar-water-storage microgrid system according to claim 2, characterized in that: The maximum upper limit power setting value P of the photovoltaic grid-connected inverter re_pv_max The expression is: P re_pv_max =P re_MPPT_p v Among them, P re_MPPT_pv It is the maximum active power tracking value of the photovoltaic grid-connected inverter; The first frequency modulation active power given value P of the photovoltaic grid-connected inverter re_pv_1 The expression is: P re_pv_1 =P re_MPPI_pv +k pv ×P re_MPPT_pv ×(f t_pv -f 1_pv ) Among them, kpv is the power frequency droop coefficient of the photovoltaic grid-connected inverter; The active standby power given value P of the photovoltaic grid-connected inverter re_pv_st The expression is: P re_pv_st =0.9×P re _ MPPT_pv The second frequency modulation active power given value P of the photovoltaic grid-connected inverter re_pv_2 The expression is: P re_pv_2 =P re_pv_st +k pv ×P re_MPPT_pv ×(f t_pv -f 3_pv ) The minimum lower limit power given value P of the photovoltaic grid-connected inverter re_pv_min The expression is: P re_pv_min =0.1×P re_MPPT_pv 。 4. A frequency control method for a wind, solar, and water storage microgrid system according to claim 2, characterized in that: The implementation process of step 2 is as follows: First define the following parameters: t_wp is the operating frequency of the wind power generation system at time t, f mi n _wp is the minimum operating frequency of the wind power generation system, f 1_wp is the inflection point value of the maximum upper limit active power droop frequency of the wind power grid-connected inverter, f 2_wp is the first inflection point value of the active standby power frequency of the wind power grid-connected inverter, f 3_wp is the second inflection point value of the active standby power frequency of the wind power grid-connected inverter, f4_ wp is the frequency inflection point value of the minimum lower limit power mode of the wind power grid-connected inverter, f max_wp is the maximum operating frequency of the wind power generation system, f n is the rated operating frequency of the wind power generation system, and f min_wp <f 1_wp <f 2_wp <f n_wp <f 3_wp <f 4_wp <f max_wp ; The wind power generation system comprises a wind power generator set; The wind power frequency partition control with lower power limit maintenance is performed in the following manner: When f t_wp <f min_wp When the wind power grid-connected inverter starts under-frequency protection and exits operation; When f min_wp ≤f t_wp ≤f 1_wp When the wind turbine generator set is connected to the wind power grid, the maximum upper limit power setting value P re_wp_max run; When f 1_wp <f t_wp <f 2_wp When the wind power grid-connected inverter performs the first Droop mode frequency modulation, the wind turbine generator set uses the wind power grid-connected inverter first frequency modulation active power given value P re_wp_1 run: When f 2_wp ≤f t_wp ≤f 3_wp When the wind turbine generator set is connected to the wind power grid, the active reserve power of the inverter is set to P re_wp_st run: When f 3_wp <f t_wp <f 4_wp When the wind power grid-connected inverter performs the second frequency modulation in the Droop mode, the wind turbine generator set uses the second frequency modulation active power given value P of the wind power grid-connected inverter. re_wp_2 run: When f 4_wp ≤f t_wp ≤f max_wp When the wind turbine generator set is connected to the wind power grid, the minimum lower limit power setting value P re_wp_min run: When f t_wp >f max_wp When the wind power grid-connected inverter starts over-frequency protection and exits operation.

5. A frequency control method for a wind-solar-water-storage microgrid system according to claim 4, characterized in that: The maximum upper limit power given value P of the wind power grid-connected inverter re_wp_max The expression is: P re_wp_max =P re_MPPT_wp Among them, P re_MPPT_wp It is the maximum active power tracking value of the wind power grid-connected inverter; The first frequency modulation active power given value P of the wind power grid-connected inverter re_wp_1 The expression is: P re_wp _ t =P re_MPPT_wp +k wp ×P re_MPPT_wp ×(f t_wp -f 1_wp ) where k wp is the power frequency droop coefficient of the wind power grid-connected inverter; The active standby power given value P of the wind power grid-connected inverter re_wp_st The expression is: P re_wp_st =0.9×P re_MPPT_wp The second frequency modulation active power given value P of the wind power grid-connected inverter re_wp_2 The expression is: P re_wp_2 =P re_wp_st +k wp ×P re_MPPT_wp ×(f t_wp -f 3_wp ) The minimum lower limit power given value P of the wind power grid-connected inverter re_wp_min The expression is: P re_wp_min =0.1×P re_MPPT_wp 。 6. A wind-solar-water-storage microgrid system frequency control method according to claim 4, characterized in that: The implementation process of step 3 is as follows: First define the following parameters: t_es is the operating frequency of the energy storage system at time t, P t_es is the active power of the energy storage system at time t, f min_es is the minimum operating frequency of the energy storage system, f 1_es is the inflection point value of the maximum upper limit active power droop frequency of the energy storage system, f2_ es is the first frequency inflection point value of the variable droop coefficient of the energy storage system, f 3_es is the second frequency inflection point value of the variable droop coefficient of the energy storage system, f 4_es is the inflection point value of the minimum lower limit active power droop frequency of the energy storage system, f max_es is the maximum operating frequency of the energy storage system, f n_es is the rated operating frequency of the energy storage system, P es_max is the maximum upper limit power given value of the energy storage grid-connected inverter, and has f min_es <f 1_es <f 2_es <f n_es <f 3_es <f 4_es <f max_es relationship; The power frequency partition control of the energy storage grid-connected inverter is performed in the following manner: When f t_es <f min_es When the inverter is connected to the energy storage grid, the under-frequency protection is activated and the inverter exits operation; When f min_es ≤f t_es ≤f 1_es When the energy storage system is connected to the grid, the maximum upper limit power of the energy storage inverter is given by P re_es_max run; When f 1_es <f t_es <f 2_es When the energy storage grid-connected inverter performs the first Droop mode frequency modulation, the energy storage system uses the energy storage grid-connected inverter first frequency modulation active power given value P re_es_1 run; When f 2_es <f t_es <f 3_es When the energy storage grid-connected inverter performs the second frequency modulation in the Droop mode, the energy storage system uses the second frequency modulation active power given value P of the energy storage grid-connected inverter. re_es_2 run; When f 3_es <f t_es <f 4_es When the energy storage grid-connected inverter performs the third frequency modulation in the Droop mode, the energy storage system uses the third frequency modulation active power given value P of the energy storage grid-connected inverter. re_es_3 run; When f 4_es ≤f t_es ≤f max_es When the energy storage system is connected to the grid, the minimum lower limit power of the energy storage inverter is given by P re_es_min run; When the frequency f t_es >f max_es When the over-frequency protection is activated, the energy storage grid-connected inverter will exit operation.

7. A frequency control method for a wind-solar-water-storage microgrid system according to claim 6, characterized in that: The maximum upper limit power setting value P of the energy storage grid-connected inverter re_es_max The expression is: P re_es_max =P s1 Among them, P s1 is the maximum output power of the energy storage system; The first frequency modulation active power given value P of the energy storage grid-connected inverter re_es_1 The expression is: P re_es_1 =P s1 +k es1 ×P s1 ×(f t_es -f 1_es ) Among them, k es1 is the first power frequency droop coefficient of the energy storage grid-connected inverter; The second frequency modulation active power given value P of the energy storage grid-connected inverter re_es_2 The expression is: P re_es_2 =P s2 +k es2 ×P s1 ×(f t_es -f 2_es ) Among them, k es2 is the second power frequency droop coefficient of the energy storage grid-connected inverter, P s2 The first power inflection point value of the variable droop coefficient of the energy storage grid-connected inverter; The third frequency modulation active power given value P of the energy storage grid-connected inverter re_es_3 The expression is: P re_es_3 =-P s2 +k es1 ×P s1 ×(f t_es -f 3_es ) The minimum lower limit power setting value P of the energy storage grid-connected inverter re_es_min The expression is: P re_es_min =-P s1 。 8. A wind-solar-water-storage microgrid system frequency control method according to claim 6, characterized in that: The power frequency partition control of the wind, solar, and water storage microgrid system described in step 4 includes the following situations: The turbine speed governor controls the turbine opening to control the turbine output power frequency. The hydropower generation system participates in the frequency control of the wind, solar, and water storage power supply system throughout the process. When f1<f t_es When <f6, the energy storage system dynamically adjusts the frequency modulation coefficient according to the output power; When f min ≤f t_es ≤f1 or f6≤f t_es ≤f max When , the energy storage system exits frequency control; When f1<f t_pv <f2 or f5 <f t_pv When <f6, the photovoltaic power generation system participates in frequency modulation with a constant frequency modulation coefficient; When f6≤f t_pv ≤f max When the photovoltaic power generation system is connected to the photovoltaic grid, the minimum lower limit power given value P re_pv_min Operation, the power generation is mainly used to charge the energy storage system; When f2 <f t_wp <f3 or f4 <f t_wp When <f5, the wind power generation system participates in frequency regulation with a constant frequency regulation coefficient; When f6≤f t_wp ≤f max When the wind power generation system is connected to the wind power grid, the minimum lower limit power given value P re_wp_min Operation, the power generation is mainly used to charge the energy storage system; Among them, f1 is the frequency inflection point value from the hydropower system switching from single frequency regulation to the hydropower system, photovoltaic system and energy storage system joint frequency regulation; f2 is the frequency inflection point value from the hydropower system, photovoltaic system and energy storage system joint frequency regulation to the hydropower system, wind power system and energy storage system joint frequency regulation; f3 is the frequency inflection point value from the hydropower system, wind power system and energy storage system joint frequency regulation to the energy storage system and hydropower system joint frequency regulation; f4 is the frequency inflection point value from the energy storage system and hydropower system joint frequency regulation to the hydropower system, wind power system and energy storage system joint frequency regulation; f5 is the frequency inflection point value from the hydropower system, wind power system and energy storage system joint frequency regulation to the hydropower system, photovoltaic system and energy storage system joint frequency regulation; f6 is the frequency inflection point value from the hydropower system, photovoltaic system and energy storage system joint frequency regulation to the hydropower system single frequency regulation; f max is the maximum operating frequency of the wind, solar, water and storage microgrid system; f min It is the minimum operating frequency of the wind, solar, water and storage microgrid system.

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