Microgrid system, energy storage system and control method

Abstract

A microgrid system, an energy storage system and a control method are disclosed. The micro-grid system is used for being connected with a mains supply system and operating in a micro-grid mode when the mains supply system does not supply power. The micro-grid system comprises a renewable energy power generation system and an energy storage system. When the micro-grid system is operated in the micro-grid mode, the energy storage system is used for outputting a control voltage containing a control frequency to the renewable energy power generation system, so that the renewable energy power generation system adjusts renewable energy output power output by the renewable energy power generation system according to the control frequency.

Description

Technical Field

[0001] The present disclosure relates to a microgrid system, an energy storage system and a control method, and in particular to a microgrid system, an energy storage system and a control method for power dispatching. Background Art

[0002] At present, power generation technology is mainly based on centralized power generation by power companies. However, when the central power generation of the power company fails, users can only wait for power to be restored and have no electricity to use.

[0003] Many technologies have been proposed to solve the above problems, including energy storage batteries, or auxiliary power generation through solar generators or other renewable energy auxiliary power generation systems to alleviate the above problems. However, the energy storage battery will be exhausted, so a method of charging the energy storage battery through solar cells has been proposed.

[0004] However, the above method also has its problems. When the energy storage battery and the solar cell cannot communicate with each other, how to control the output power of the solar cell to achieve a balance between the solar cell, the energy storage battery and the load is one of the problems to be solved. Summary of the invention

[0005] In order to solve the above problems, the present disclosure proposes a microgrid system for connecting to a mains power system and for operating in a microgrid mode when the mains power system is not supplying power. The microgrid system includes a renewable energy generation system and an energy storage system. When the microgrid system operates in the microgrid mode, the energy storage system is used to output a control voltage including a control frequency to the renewable energy generation system, so that the renewable energy generation system adjusts the renewable energy output power output by the renewable energy generation system according to the control frequency.

[0006] The present disclosure also proposes an energy storage system, which together with a renewable energy power generation system forms a microgrid system. When the mains power system is not supplying power, the microgrid system operates in a microgrid mode. The energy storage system includes an energy storage battery and an integration device. The energy storage battery is used to output a DC voltage in the microgrid mode. The integration device is coupled to the energy storage battery. The integration device includes a DC-AC converter and a controller. The DC-AC converter is coupled to the energy storage battery to convert the DC voltage into a control voltage and transmit the control voltage to the renewable energy power generation system. The control voltage includes a control frequency. The controller is coupled to the DC-AC converter. In the microgrid mode, the controller is used to adjust the control frequency so that the renewable energy power generation system adjusts the renewable energy output power output by the renewable energy power generation system according to the control frequency.

[0007] The present disclosure also proposes a control method, which is applicable to a microgrid system, used to connect to a mains power system, and used to operate in a microgrid mode when the mains power system is not supplying power. The microgrid system includes an energy storage system and a renewable energy generation system. The control method includes the following steps: the energy storage system outputs a control voltage including a control frequency to the renewable energy generation system; and the renewable energy generation system adjusts the renewable energy output power output by the renewable energy generation system according to the control frequency, so that the microgrid system achieves power balance.

[0008] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the disclosure as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to make the above and other purposes, features, advantages and embodiments of the present disclosure more clearly understood, the following are the descriptions of the accompanying drawings:

[0010] Figure 1 is a schematic diagram of a microgrid system according to some embodiments of the present invention;

[0011] Figure 2 is a flow chart of a control method according to some embodiments of the present invention;

[0012] Figure 3 According to some embodiments of the present invention, Figure 2 A flowchart of one of the steps in ;

[0013] Figure 4 is a schematic diagram showing a relationship between a control frequency and a renewable energy output power according to some embodiments of the present invention; and

[0014] Figure 5 It is a schematic diagram showing the relationship between a control frequency and a renewable energy output power according to some embodiments of the present invention.

[0015] Description of reference numerals:

[0016] 100: Microgrid system

[0017] 110: Energy Storage System

[0018] 112: Energy storage battery

[0019] 114: Integration Device

[0020] 115: DC to AC converter

[0021] 117: Controller

[0022] 130: Renewable energy power generation system

[0023] 132: Solar Cells

[0024] 134: Solar inverter

[0025] B1, B2, B3: No fuse switch

[0026] C1, C2, C3, C4: Switcher (Relay)

[0027] VC: Control voltage

[0028] FC: Control frequency

[0029] POUT: Renewable energy output power

[0030] 900A,900B: Load

[0031] 800: Mains power system

[0032] 200: Control Methods

[0033] S210, S230: Steps

[0034] S305, S310, S320, S330, S350, S360: Steps

[0035] S370,S390: Steps

[0036] Fbuffer: buffer frequency range

[0037] FB: Basic frequency

[0038] PB: Basic Power

[0039] P1, P2: Power

[0040] F1, F2, F3, F4: Frequency

[0041] t0, t1, t2, t3, t4, t5: time points

[0042] t6,t7,t8,t9,t10,t11,t12: time points

[0043] ta1,ta2,ta3,ta4: time interval

[0044] tb1, tb2: time interval DETAILED DESCRIPTION

[0045] The following is a detailed description of the embodiments with accompanying drawings, but the embodiments provided are not intended to limit the scope of the present disclosure, and the description of the structure operation is not intended to limit the order of its execution. Any device with equal technical effects produced by the re-combination of components is within the scope of the present disclosure. In addition, the drawings are for illustrative purposes only and are not drawn in their original size. For ease of understanding, the same or similar components in the following description will be indicated by the same symbols.

[0046] Please refer to Figure 1 , Figure 1 is a schematic diagram of a microgrid system 100 according to some embodiments of the present invention. Figure 1 In the embodiment, the microgrid system 100 includes an energy storage system 110 and a renewable energy generation system 130 .

[0047] The microgrid system 100 is used to connect to the mains system 800. In some embodiments, the microgrid system 100 further includes switches (relays) C1 to C4, which are used to control the connection relationship and power supply relationship between the energy storage system 110, the renewable energy generation system 130 and the mains system 800 in conjunction with the non-fuse switches B1 to B3.

[0048] When the mains is powered, the microgrid system 100 operates in the mains mode. At this time, the mains system 800 operates as a voltage source, while the energy storage system 110 and the renewable energy generation system 130 operate as current sources, and the mains system 800 supplies power to the load 900A, while the load 900B is powered by the mains system 800 through the path of the non-fuse switch B1, the switch (relay) C1, the switch (relay) C2, the switch (relay) C3, and the non-fuse switch B3. On the other hand, when the mains is not powered, the microgrid system 100 operates in the microgrid mode, at which time the energy storage system 110 operates as a voltage source, while the renewable energy generation system 130 operates as a current source, and the energy storage system 110 and the renewable energy generation system 130 are connected in parallel to supply power to the specific attached load 900B. In one embodiment, when the output power of the renewable energy power generation system 130 is greater than the load power of the load 900B, the renewable energy power generation system 130 is further configured to supply power to the load 900B and charge the energy storage system 110 at the same time.

[0049] In some embodiments, the load 900A is a general load, and the load 900B is a specific load. In one embodiment, the specific load may be emergency power that must be used when the mains power system 800 is not supplying power, such as an emergency lighting lamp.

[0050] about Figure 1 The detailed operation of the microgrid system 100 will be described below with reference to Figure 2 Detailed description.

[0051] Please continue to refer to Figure 1 .At Figure 1 In the embodiment, the energy storage system 110 includes an energy storage battery 112 and an integrated device 114. The energy storage battery 112 and the integrated device 114 are coupled. The renewable energy generation system 130 includes a solar cell 132 and a solar inverter 134. The solar cell 132 and the solar inverter 134 are coupled.

[0052] In some embodiments, the integrated device 114 includes a DC-AC converter 115 and a controller 117. The DC-AC converter 115 and the controller 117 are coupled. The DC-AC converter 115 is also coupled to the energy storage battery 112 to convert the DC voltage output by the energy storage battery 112 in the microgrid mode into a control voltage VC. The controller 117 is used to adjust the control frequency FC included in the control voltage VC, so that the renewable energy power generation system 130 adjusts the renewable energy output power POUT output by the renewable energy power generation system 130 according to the control frequency FC.

[0053] Please refer to Figure 2 . Figure 2 is a flow chart of a control method 200 according to some embodiments of the present invention. The control method 200 is applicable to Figure 1 The microgrid system 100 is executed in the microgrid mode. The control method 200 includes steps S210 to S230.

[0054] In step S210 , the energy storage system 110 outputs a control voltage VC including a control frequency FC to the renewable energy generation system 130 .

[0055] In step S230, the renewable energy power generation system 130 adjusts the renewable energy output power POUT output by the renewable energy power generation system 130 according to the control frequency FC. By adjusting the renewable energy output power POUT output by the renewable energy power generation system 130, power balance can be achieved among the renewable energy power generation system 130, the load 900B and the energy storage system 110.

[0056] Please refer to Figure 3 . Figure 3 According to some embodiments of the present invention, Figure 2 Flowchart of step S210 in FIG. Step S210 includes steps S305 to S390. Figure 1 Provide explanation.

[0057] In step S305 , the energy storage system 110 operates in the microgrid mode and outputs a control voltage VC whose control frequency FC is the basic frequency FB to the renewable energy generation system 130 , so that the renewable energy generation system 130 outputs the renewable energy output power POUT according to the basic frequency FB of the control voltage VC.

[0058] Please refer to Figure 4 . Figure 4 FIG. 1 is a schematic diagram showing a relationship P(f) between a control frequency FC and a renewable energy output power POUT according to some embodiments of the present invention. Figure 4 As shown in the figure, the basic frequency FB is a frequency in the buffer frequency interval Fbuffer. When the control frequency FC is higher than the buffer frequency interval Fbuffer, as the control frequency FC increases, the output power POUT of the renewable energy gradually decreases.

[0059] It should be noted that if Figure 4 The relationship between the control frequency FC and the renewable energy output power POUT shown is linear, however, the embodiments of the present disclosure are not limited thereto. In some other embodiments, the relationship between the control frequency FC and the renewable energy output power POUT may be a step-down relationship.

[0060] Please refer back Figure 3 In step S305 , when the control frequency FC is the basic frequency FB, the renewable energy output power POUT is the maximum power that the renewable energy power generation system 130 can output, that is, 100% of the power.

[0061] Please also read Figure 5 . Figure 5 FIG. 1 is a schematic diagram showing the relationship between a control frequency FC and a renewable energy output power POUT according to some embodiments of the present invention. Figure 5 As shown, at time point t0, the control frequency FC is the basic frequency FB, and the output power POUT of the renewable energy is the basic power PB. In one embodiment, the basic power PB corresponds to Figure 4 100% power shown.

[0062] In some embodiments, when the microgrid system 100 is operated in the microgrid mode, the controller 117 of the energy storage system 110 is further used to adjust the control frequency FC so that the control frequency FC periodically decreases from the first frequency to the second frequency and then increases to the first frequency. Figure 5As shown, at time point t1, the controller 117 adjusts the control frequency FC so that the control frequency FC gradually decreases from the basic frequency FB to the frequency F1 within the time interval ta1, and reaches the frequency F1 at time point t2. Then, at time point t2, the controller 117 adjusts the control frequency FC so that the control frequency FC gradually increases from the frequency F1 to the basic frequency FB within the time interval ta2, and reaches the frequency basic FB at time point t3. In the time interval tb1 between time point t3 and time point t4, the control frequency FC is maintained at the basic frequency FB. Then, at time point t4, the controller 117 adjusts the control frequency FC so that the control frequency FC gradually decreases from the frequency F1 within the time interval ta3, and reaches the frequency F1 at time point t5. Then, at time point t5, the controller 117 adjusts the control frequency FC so that the control frequency FC gradually increases from the frequency F1 to the frequency FB within the time interval ta4, and reaches the frequency FB at time point t6.

[0063] In one embodiment, Figure 5 The time intervals ta1, ta2, ta3, and ta4 shown in FIG. 1 have the same time length, and the time intervals tb1 and tb2 have the same time length.

[0064] The control frequency FC described above periodically decreases from the first frequency to the second frequency and then increases to the first frequency, which can be regarded as a password in the control frequency FB. Through the password, the renewable energy generation system 130 can know that the current microgrid system 100 is operating in the microgrid mode. When the renewable energy generation system 130 does not receive the password described above within a certain period of time, the renewable energy generation system 130 determines that the current microgrid system 100 is operating in the mains mode.

[0065] In step S310, the controller 117 of the energy storage system 110 determines whether the output power POUT of the renewable energy is greater than the load power of the load 900B. If the output power POUT of the renewable energy is not greater than the load power of the load 900B, step S320 is executed. If the output power POUT of the renewable energy is greater than the load power of the load 900B, step S330 is executed.

[0066] In step S320, when the renewable energy output power POUT is less than the load power of the load 900B, the renewable energy power generation system 130 and the energy storage system 110 are connected in parallel to supply power to the load 900B, so as to simultaneously output power to the load 900B, so as to supply power to the load 900B. When the renewable energy output power POUT is equal to the load power of the load 900B, the renewable energy power generation system 130 outputs the renewable energy output power POUT to the load 900B, so as to supply power to the load 900B.

[0067] In step S330, the renewable energy power generation system 130 provides load power to the load 900B while charging the energy storage battery 112 in the energy storage system 110 with charging power. In some embodiments, the charging power is the power at which the renewable energy output power POUT is greater than the load power of the load 900B. That is, the charging power is the renewable energy output power POUT minus the load power of the load 900B.

[0068] In step S350, the controller 117 of the energy storage system 110 determines whether the renewable energy output power POUT is greater than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112. In other words, it determines whether the charging power of the energy storage battery 112 is greater than the charging power capacity of the energy storage battery 112.

[0069] If the output power POUT of the renewable energy source is greater than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112, that is, the charging power is greater than the charging power capacity, step S360 is executed. If the output power POUT of the renewable energy source is not greater than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112, that is, the charging power is not greater than the charging power capacity, step S370 is executed.

[0070] In step S360 , the controller 117 of the energy storage system 110 increases the control frequency FC to reduce the renewable energy output power POUT output by the renewable energy power generation system 130 until the renewable energy output power POUT is equal to the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112 .

[0071] In some embodiments, in step S360, the controller 117 of the energy storage system 110 is further used to increase the control frequency FC to a point where the renewable energy output power POUT is slightly lower than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112, and then reduce the control frequency FC to a point where the renewable energy output power POUT is equal to the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112.

[0072] Please also read Figure 5 At time point t8, the controller 117 of the energy storage system 110 gradually increases the control frequency FC from the frequency FB to the frequency F3. As the control frequency FC gradually increases from the frequency FB to the frequency F3, the output power POUT of the renewable energy gradually decreases from the power PB to the power P1.

[0073] At time point t9, the renewable energy output power POUT is P1. At this time, the renewable energy output power POUT is slightly lower than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112. That is, at time point t9, the charging power is slightly less than the charging power capacity. At this time, the controller 117 of the energy storage system 110 gradually reduces the control frequency FC from frequency F3 to frequency F2. As the control frequency FC gradually decreases from frequency F3 to frequency F2, the renewable energy output power POUT gradually increases from power P1 to power P2. At time point t10, the control frequency FC is frequency F2, and the renewable energy output power POUT is power P2. At this time, the renewable energy output power POUT is equal to the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112. That is, at time point t10, the charging power is equal to the charging power capacity.

[0074] like Figure 5 As shown in the figure, after time point t10, since the charging power is equal to the charging power capacity, the control frequency FC does not need to be adjusted up or down at this time, and the controller 117 of the energy storage system 110 adjusts the control frequency FC again, so that the control frequency FC periodically decreases from frequency F2 to frequency F4, and then increases from frequency F4 to frequency F2. That is, the controller 117 of the energy storage system 110 adjusts the control frequency FC again, so that the control frequency FC outputs the password to the renewable energy power generation system 130, so that the renewable energy power generation system 130 knows that the current microgrid system 100 is operating in the microgrid mode.

[0075] In step S370, the controller 117 of the energy storage system 110 determines whether the renewable energy output power POUT is less than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112. In other words, it determines whether the charging power of the energy storage battery 112 is less than the charging power capacity of the energy storage battery 112.

[0076] If the output power POUT of the renewable energy source is not less than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112, that is, the charging power is not less than the charging power capacity, return to step S330. The load power is output to the load 900B at the same time with the current output power POUT of the renewable energy source and the energy storage battery 112 is charged with the charging power. On the other hand, if the output power POUT of the renewable energy source is less than the sum of the load power of the load 900B and the charging power capacity of the energy storage battery 112, that is, the charging power is less than the charging power capacity, return to step S330.

[0077] In step S390 , the controller 117 of the energy storage system 110 reduces the control frequency FC to the basic frequency FB, so that the renewable energy output power POUT output by the renewable energy power generation system 130 increases to the basic power PB.

[0078] Please also read Figure 5 At time point t11, the controller 117 of the energy storage system 110 gradually reduces the control frequency FC from the frequency F2 to the frequency FB, so that the renewable energy output power POUT gradually increases from the power P2 to the basic power PB. At time point t12, the control frequency FC is the basic frequency FB, and the renewable energy output power POUT is the basic power PB. After step S390, return to step S310.

[0079] In some embodiments, the integrated device 114 and the solar inverter device 134 may include a central processing unit (CPU), a microprocessor (MCU), a server, or other computing circuits or elements with data access, data calculation, data storage, data transmission and reception, or similar functions, and may be used to execute the control method 200.

[0080] In some embodiments, the integrated device 114 and the solar inverter device 134 may further include other components required for operation and application. For example, the integrated device 114 and the solar inverter device 134 may also include an output interface (for example, a display panel for displaying information), an input interface (for example, a touch panel, a keyboard, a scanner, or a flash memory reader) and an internal communication circuit (for example, a WiFi communication model, a Bluetooth communication model, a wireless telecommunications network communication model, etc.), a DC-to-DC converter, a switch, a switch driving circuit, a power detection circuit, a feedback circuit, a storage element, etc.

[0081] In some embodiments, the integrated device 114 further includes a battery management circuit for managing the state of the energy storage battery 112 and charging and discharging the energy storage battery 112 .

[0082] In summary, the disclosed embodiments provide a microgrid system, an energy storage system, and a control method, which controls the renewable energy output power POUT of the renewable energy power generation system 130 by changing the control frequency FC input to the renewable energy power generation system 130, so as to achieve power balance between the energy storage system 110, the renewable energy power generation system 130, and the load 900B. In addition, by setting a password in the control frequency FC, the renewable energy power generation system 130 can know whether the microgrid 100 is currently operating in a microgrid mode or a mains mode without a communication connection with the energy storage system 110. In this way, the renewable energy power generation system 130 can operate in different island parameters, power boost parameters, P(F) parameters, etc. in the microgrid mode and the mains mode, respectively, and is more flexible in operation.

[0083] In addition, it should be noted that, in the steps of the control method 200, there is no special order requirement unless otherwise specified. In addition, these steps can also be executed simultaneously, or their execution time can at least partially overlap.

[0084] Regarding the terms used in this article, unless otherwise specified, they generally have the ordinary meaning of each term used in this field, in the content of this disclosure and in the special content. Certain terms used to describe the present disclosure will be discussed elsewhere in this specification to provide additional guidance to those skilled in the art on the description of the present disclosure.

[0085] Although specific embodiments of the present disclosure have been disclosed with respect to the above-mentioned embodiments, these embodiments are not intended to limit the present disclosure. Various substitutions and improvements can be performed in the present disclosure by a person of ordinary skill in the relevant art without departing from the principles and concepts of the present disclosure. Therefore, the scope of protection of the present disclosure is determined by the appended claims.

Claims

1. A microgrid system, for connecting to a mains power system and for operating in a microgrid mode when the mains power system is not supplying power, wherein the microgrid system comprises: A renewable energy power generation system; and An energy storage system, wherein when the microgrid system operates in the microgrid mode, the energy storage system is used to output a control voltage including a control frequency to the renewable energy power generation system, so that the renewable energy power generation system adjusts a renewable energy output power output by the renewable energy power generation system according to the control frequency.

2. The microgrid system as described in claim 1, wherein when the renewable energy output power output by the renewable energy power generation system is greater than a load power, the renewable energy power generation system charges a storage battery of the energy storage system with a charging power, wherein the charging power is the difference between the renewable energy output power and the load power.

3. The microgrid system as described in claim 2, wherein when the charging power is greater than a charging power capacity of the energy storage battery, the energy storage system increases the control frequency from a first frequency to a second frequency, so that the renewable energy output power output by the renewable energy power generation system decreases from a first power to a second power, so that the renewable energy output power is equal to the charging power plus the load power.

4. The microgrid system as described in claim 3, wherein when the charging power is greater than the charging power capacity of the energy storage battery, the energy storage system is further used to increase the control frequency from the first frequency to a third frequency until the output power of the renewable energy is less than the charging power capacity plus the load power, and then reduce the control frequency from the third frequency to the second frequency.

5. The microgrid system as claimed in claim 2, wherein when the charging power is less than a charging power capacity of the energy storage battery, the energy storage system is further configured to reduce the control frequency to a basic frequency.

6. The microgrid system as claimed in claim 1, wherein when the renewable energy output power output by the renewable energy power generation system is greater than a load power, the energy storage system is further used to supply power in parallel with the renewable energy power generation system.

7. The microgrid system as described in claim 1, wherein the energy storage system is further used to periodically reduce the control frequency from a first frequency to a second frequency, and then increase from the second frequency to the first frequency, so that the renewable energy generation system knows that it is currently operating in the microgrid mode.

8. An energy storage system, together with a renewable energy power generation system, forms a microgrid system, wherein when a mains power system is not supplying power, the microgrid system operates in a microgrid mode, wherein the energy storage system comprises: an energy storage battery for outputting a DC voltage in the microgrid mode; and An integrated device, coupled to the energy storage battery, comprising: a DC-AC converter, coupled to the energy storage battery, for converting the DC voltage into a control voltage and transmitting the control voltage to the renewable energy generation system, wherein the control voltage includes a control frequency; and A controller is coupled to the DC-AC converter, wherein in the microgrid mode, the controller is used to adjust the control frequency so that the renewable energy power generation system adjusts a renewable energy output power output by the renewable energy power generation system according to the control frequency.

9. The energy storage system as described in claim 8, wherein when the renewable energy output power output by the renewable energy power generation system is greater than a load power, the renewable energy power generation system charges a storage battery of the energy storage system with a charging power, wherein the charging power is the difference between the renewable energy output power and the load power, and when the charging power is greater than a charging power capacity of the energy storage battery, the controller is further used to increase the control frequency from a first frequency to a second frequency, so that the renewable energy output power output by the renewable energy power generation system decreases from a first power to a second power, so that the renewable energy output power is equal to the charging power plus the load power.

10. The energy storage system as claimed in claim 9, wherein when the charging power is greater than the charging power capacity of the energy storage battery, the controller is further configured to increase the control frequency from the first frequency to a third frequency until the output power of the renewable energy is less than the charging power capacity plus the load power, and then reduce the control frequency from the third frequency to the second frequency. 11 . The energy storage system as claimed in claim 9 , wherein when the charging power is less than a charging power capability of the energy storage battery, the controller is further configured to reduce the control frequency to a basic frequency. 12 . The energy storage system as claimed in claim 8 , wherein when the renewable energy output power output by the renewable energy power generation system is greater than a load power, the controller is further configured to supply power in parallel with the renewable energy power generation system.

13. The energy storage system as claimed in claim 8, wherein the controller is further used to periodically reduce the control frequency from a first frequency to a second frequency, and then increase from the second frequency to the first frequency, so that the renewable energy power generation system knows that it is currently operating in the microgrid mode.

14. A control method, applicable to a microgrid system, used to connect to a mains power system and to operate in a microgrid mode when the mains power system is not supplying power, wherein the microgrid system includes an energy storage system and a renewable energy generation system, wherein the control method includes: Outputting a control voltage including a control frequency from the energy storage system to the renewable energy power generation system; and The renewable energy power generation system adjusts a renewable energy output power output by the renewable energy power generation system according to the control frequency, so that the microgrid system achieves power balance.

15. The control method according to claim 14, further comprising: When the renewable energy output power output by the renewable energy power generation system is greater than a load power, the renewable energy power generation system charges an energy storage battery of the energy storage system with a charging power; The charging power is the difference between the output power of the renewable energy and the load power.

16. The control method according to claim 15, further comprising: When the charging power is greater than a charging power capacity of the energy storage battery, the energy storage system increases the control frequency from a first frequency to a second frequency; The renewable energy power generation system adjusts the renewable energy output power from a first power to a second power according to the control frequency, so that the renewable energy output power is equal to the charging power plus the load power.

17. The control method according to claim 16, further comprising: When the charging power is greater than the charging power capacity of the energy storage battery, the energy storage system increases the control frequency from the first frequency to a third frequency until the output power of the renewable energy is less than the charging power capacity plus the load power, and then reduces the control frequency from the third frequency to the second frequency.

18. The control method according to claim 15, further comprising: When the charging power is less than a charging power capacity of the energy storage battery, the energy storage system adjusts the control frequency down to a basic frequency.

19. The control method according to claim 14, further comprising: When the renewable energy output power output by the renewable energy power generation system is greater than a load power, the energy storage system and the renewable energy power generation system are connected in parallel to supply power.

20. The control method of claim 14, further comprising: The energy storage system adjusts the control frequency so that the control frequency periodically decreases from a first frequency to a second frequency and then increases from the second frequency to the first frequency, so that the renewable energy generation system knows that it is currently operating in the microgrid mode.

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