A molten salt and electrochemical hybrid energy storage system and method of controlling the same

Abstract

The application discloses a kind of based on molten salt and electrochemical hybrid energy storage system and its control method, the system includes generator set, coordinated controller and power synthesis device;Including:1) the initial SOC of electrochemical energy storage system is C0%, SOC indicates the charge rate of electrochemical energy storage system, 50≤C0≤90, the initial electric heating power of molten salt energy storage system is 0;2) when power grid issues AGC instruction of downward adjustment power to generator set, electrochemical energy storage system is prior to molten salt energy storage system and responds;3) when power grid issues AGC instruction of upward adjustment power to generator set, molten salt energy storage system is prior to electrochemical energy storage system and responds;4) in the process that hybrid energy storage system continues to respond AGC instruction, whenever the SOC of electrochemical energy storage system is reduced to 10% and below, rebalance of electrochemical energy storage system is carried out once, adjusts the SOC of electrochemical energy storage system;5) in the process that hybrid energy storage system continues to respond AGC instruction, the ratio is calculated.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of power system energy storage, and particularly relates to a molten salt and electrochemical hybrid energy storage system and a control method thereof. BACKGROUND

[0002] The existing utility model patent "Energy storage device and control system for improving AGC frequency modulation performance of power plant" discloses an energy storage device and control system for improving AGC frequency modulation performance of power plant, wherein the energy storage device comprises a plurality of energy storage subsystems, and each energy storage subsystem comprises a PCS container and a lithium iron phosphate battery system container. This energy storage system based on lithium iron phosphate batteries has many application cases, but this energy storage system has the defects of high investment cost and short battery life.

[0003] The existing utility model patent "Energy storage device with controllable load participating in primary frequency modulation system of thermal power generating unit" discloses an energy storage device with controllable load participating in primary frequency modulation of thermal power generating unit, which can optimize the primary frequency modulation performance of the thermal power generating unit and has little change to the original thermal power generating unit. In actual application cases, the controllable load is in the form of electrically heated molten salt medium. The controllable load based on molten salt can overcome the defects of high investment cost and short life of electrochemical energy storage systems, but in actual operation, the molten salt controllable load needs to be continuously operated for a long time, resulting in high operation cost. SUMMARY

[0004] The application is based on the advantages and disadvantages of the above two energy storage forms, and provides a hybrid energy storage system based on molten salt and electrochemistry and a control method thereof. Because the control targets of the molten salt system and the electrochemical energy storage system are the difference between the AGC instruction and the unit power, the two systems will not cooperate due to different response speeds.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme:

[0006] A molten salt and electrochemical hybrid energy storage system comprises a generator unit, a coordination controller and a power synthesis device.

[0007] The high-voltage plant bus A section of the low-voltage side of the high-voltage plant transformer of the generator unit is connected to the electrochemical energy storage system, and the high-voltage plant bus B section of the low-voltage side of the high-voltage plant transformer is connected to the electric heater of the molten salt energy storage system.

[0008] The control target of the coordination controller is the difference between the AGC instruction sent by the unit DCS and the generator power, and the control object of the coordination controller is the electrochemical energy storage system and the molten salt electric heater system.

[0009] The power synthesis device is used for synthesizing the power of the electrochemical energy storage system and the power of the molten salt electric heater system by a vector synthesis method, and sending the power to the RTU device, wherein the positive direction of the power of the electrochemical energy storage system and the positive direction of the power of the molten salt electric heater system are consistent, and are both directed to the energy storage system by the high-voltage plant bus.

[0010] The further improvement of the application is that the generator set is further connected to the power grid through the main transformer.

[0011] The further improvement of the application is that the coordination controller adopts a state machine control mode.

[0012] The further improvement of the application is that the coordination controller cyclically operates among three states, and the three states are respectively obtaining AGC instructions and generator power information from the DCS, calculating power distribution data of the electrochemical energy storage system and the molten salt electric heater system, and sending power distribution signals to the electrochemical energy storage system and the molten salt electric heater system.

[0013] The further improvement of the application is that the power synthesis device realizes multi-channel parallel sampling by adopting an FPGA technology.

[0014] The further improvement of the application is that the power synthesis device sends the power synthesis signals of the electrochemical energy storage system and the molten salt electric heater system to the RTU device by a parallel data transmission mode, so as to reduce the delay in the data transmission process.

[0015] A control method of a molten salt and electrochemical hybrid energy storage system, comprising:

[0016] 1) the initial SOC of the electrochemical energy storage system is C0%, SOC represents the charging rate of the electrochemical energy storage system, 50≤C0≤90, and the initial electric heating power of the molten salt energy storage system is 0;

[0017] 2) when the power grid issues an AGC instruction of downward power adjustment to the generator set, the electrochemical energy storage system is preferentially responded to than the molten salt energy storage system;

[0018] 3) when the power grid issues an AGC instruction of upward power adjustment to the generator set, the molten salt energy storage system is preferentially responded to than the electrochemical energy storage system;

[0019] 4) in the process of continuously responding to the AGC instruction by the hybrid energy storage system, whenever the SOC of the electrochemical energy storage system is reduced to 10% or below, rebalancing of the electrochemical energy storage system is performed once, and the SOC of the electrochemical energy storage system is adjusted to C n+1 %, C n+1 =C n +1, n≥0;

[0020] 5) In the process of the hybrid energy storage system continuously responding to the AGC instruction, the ratio is calculated The numerator of the ratio is the amount of electricity consumed by the molten salt energy storage system in the process of responding to the frequency modulation instruction, and the unit is MWh, and the denominator of the ratio is the distance quantity of the frequency modulation instruction responded by the molten salt energy storage system, and the unit is MW, and when is greater than 0.5, the electrochemical energy storage system is rebalanced once, and the SOC of the electrochemical energy storage system is adjusted to C n+1 %, C n+1 =C n -1, n is greater than or equal to 0.

[0021] Further improvements of the present application are that in step 2), the electrochemical energy storage system responds to such AGC instructions by charging, and when the electrochemical energy storage system SOC is charged to 100%, the charging is stopped, and then the molten salt energy storage system continues to respond to such AGC instructions; the molten salt energy storage system responds to such AGC instructions by increasing the power of the molten salt electric heater.

[0022] Further improvements of the present application are that in step 3), the molten salt energy storage system responds to such AGC instructions by reducing the power of the molten salt electric heater.

[0023] Further improvements of the present application are that in step 3), when the power of the molten salt electric heater is reduced to 0, the response to such AGC instructions is stopped, and then the electrochemical energy storage system continues to respond to such AGC instructions, and the electrochemical energy storage system responds to such AGC instructions by discharging.

[0024] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0025] The hybrid energy storage system based on molten salt and electrochemistry and the control method thereof provided by the present application can coordinate the order of the electrochemical energy storage system and the molten salt energy storage system responding to the AGC instruction based on the unified control target of the AGC instruction and the generator power difference, avoid the insufficient response or excessive response caused by the lack of cooperation between the two systems, fully play the synergistic effect of the molten salt energy storage system and the electrochemical energy storage system, and jointly assist the unit to respond to the AGC instruction.

[0026] Further, the present application has the function of self-regulation, can adapt to different frequency modulation working conditions, and can adjust the response strategy through rebalancing according to historical frequency modulation working conditions, so as to adapt to different frequency modulation working conditions of different power grids.

[0027] Further, the application makes full use of the one-way adjustment function of the molten salt energy storage system and the two-way adjustment function of the electrochemical energy storage system, complementary advantages, reduces the response frequency of the electrochemical energy storage system, thereby prolonging the service life of the electrochemical energy storage system, at the same time, through the two-way adjustment function of the electrochemical energy storage system, the deficiency of the one-way adjustment function of the molten salt energy storage system is made up, and the operation cost of the molten salt energy storage system is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the specific embodiments or technical solutions in the prior art of the present application, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.

[0029] Figure 1 The structure block diagram of the molten salt and electrochemical hybrid energy storage system of the present application.

[0030] Figure 2 The structure block diagram of the electrochemical energy storage system that has been built in a power plant in the embodiment. DETAILED DESCRIPTION

[0031] In the following, only some exemplary embodiments are simply described. As those skilled in the art can realize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0032] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0033] In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0034] In the present application, unless specifically defined otherwise, the terms "mount", "connected", "connecting", "fixed", "unfixed", and the like are to be construed in their broadest possible sense, such as, for example, fixedly connected, detachably connected, or integral; mechanically connected, electrically connected, or communicatively connected; directly connected, or connected through an intermediary; or two elements in communication with each other or interacting with each other. Those of ordinary skill in the art will appreciate the meaning of the above terms in the present application based on the specific context.

[0035] In the present application, unless specifically defined otherwise, "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above", and "over" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is higher in horizontal height than the second feature. "Under", "below", and "underneath" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is lower in horizontal height than the second feature.

[0036] It should be understood that the terms "comprise" and "comprising" as used in the specification and the appended claims indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0037] It should also be understood that the terms used in the present specification and the appended claims are intended to be interpreted broadly and in a manner similar to commonly used dictionaries, such as Webster's Third New International Dictionary, and not in an overly limited or restricted manner unless specifically defined otherwise in the present specification.

[0038] It should further be understood that the term "and / or" as used in the present specification and the appended claims is intended to mean any one of the associated listed items, or any combination of one or more of the associated listed items, and all possible combinations thereof.

[0039] Various structural diagrams according to the disclosed embodiments of the present application are shown in the drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for clarity and others omitted. The shapes of various regions, layers shown in the drawings and their relative sizes and positional relationships are merely exemplary, and in actuality may deviate due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes, relative positions can be additionally designed according to actual needs by those skilled in the art.

[0040] The embodiments of the present application are described in detail below with reference to the drawings.

[0041] Embodiment 1

[0042] As shown in Figure 1 , the present application provides a molten salt and electrochemical hybrid energy storage system, including a generator set, a coordination controller and a power synthesis device;

[0043] The high-voltage auxiliary bus A section of the low-voltage side of the high-voltage auxiliary transformer of the generator set is connected to the electrochemical energy storage system, and the high-voltage auxiliary bus B section of the low-voltage side of the high-voltage auxiliary transformer is connected to the electric heater of the molten salt energy storage system;

[0044] The control target of the coordination controller is the difference between the AGC instruction sent by the unit DCS (distributed control system) and the generator power, and the control object is the electrochemical energy storage system and the molten salt electric heater system;

[0045] The power synthesis device synthesizes the power of the electrochemical energy storage system and the power of the molten salt electric heater system by vector synthesis method, and sends it to the RTU device, wherein the positive direction of the power of the electrochemical energy storage system and the positive direction of the power of the molten salt electric heater system are consistent, and both point to the energy storage system of the high-voltage auxiliary bus.

[0046] The present application improves energy utilization efficiency and flexibility: by combining the generator set, the electrochemical energy storage system and the molten salt energy storage system, the system can flexibly adjust the output power according to the grid demand or the AGC (automatic generation control) instruction, effectively improving the efficiency and flexibility of energy utilization. The electrochemical energy storage system can quickly respond to the instantaneous demand of the power grid, while the molten salt energy storage system can provide long-term stable energy storage, and the combination of the two realizes the complementation of short-term and long-term energy storage.

[0047] The present application enhances the stability and reliability of the system: the introduction of the coordination controller enables the system to monitor and adjust the difference between the generator power and the AGC instruction in real time, ensuring the stable operation of the power system. Through the power synthesis device, the system can effectively synthesize the power of the electrochemical energy storage and the molten salt energy storage, improving the output capacity and reliability of the overall system.

[0048] The present application optimizes energy allocation and reduces operating costs: the system can intelligently select electrochemical energy storage or molten salt energy storage according to grid load and electricity price to optimize energy allocation and reduce operating costs. For example, at the low electricity price, the electric heater of the molten salt energy storage system can be used for energy storage, and at the peak electricity price or increased grid demand, the energy can be released through the electrochemical energy storage system or the molten salt energy storage system to reduce the cost of electricity.

[0049] The present application improves the intelligent level of the system: the use of the coordination controller reflects the intelligent and automated level of the system, reduces manual intervention, and improves the response speed and accuracy of the system. The power synthesis device realizes the accurate synthesis of the power of the electrochemical energy storage and the molten salt energy storage through the vector synthesis method, further improving the intelligent level of the system.

[0050] The present application promotes the access and utilization of renewable energy: the hybrid energy storage system can provide stable energy storage and output support for renewable energy (such as wind energy and solar energy), which helps to solve the intermittent and unstable problems of renewable energy. Through the combination with renewable energy, the system helps to promote the widespread access and utilization of renewable energy, and promotes the optimization and transformation of energy structure.

[0051] In this embodiment, the generator set is also connected to the power grid through the main transformer.

[0052] In this embodiment, the coordination controller adopts a state machine control mode, and the coordination controller runs in a loop among three states, which are obtaining AGC instructions and generator power information from the DCS, calculating power allocation data of the electrochemical energy storage system and the molten salt electric heater system, and sending power allocation signals to the electrochemical energy storage system and the molten salt electric heater system.

[0053] In this embodiment, the power synthesis device realizes multi-channel parallel sampling by using FPGA technology.

[0054] In this embodiment, the power synthesis device sends the power synthesis signals of the electrochemical energy storage system and the molten salt electric heater system to the RTU device through a parallel data transmission method, reducing the delay in the data transmission process.

[0055] Embodiment 2

[0056] The present application provides a control method for a molten salt and electrochemical hybrid energy storage system, which comprises:

[0057] 1) The initial SOC of the electrochemical energy storage system is C0%, SOC represents the charging rate of the electrochemical energy storage system, 50≤C0≤90, and the initial electric heating power of the molten salt energy storage system is 0;

[0058] 2) When the power grid issues AGC instructions to the generator set to adjust power downward, the electrochemical energy storage system responds in preference to the molten salt energy storage system;

[0059] 3) When the power grid issues AGC instructions to the generator set to adjust power upward, the molten salt energy storage system responds in preference to the electrochemical energy storage system;

[0060] 4) During the process of the hybrid energy storage system continuously responding to AGC instructions, whenever the SOC of the electrochemical energy storage system is reduced to 10% and below, rebalancing of the electrochemical energy storage system is performed to adjust the SOC of the electrochemical energy storage system to C n+1 %, C n+1 =C n +1, n≥0;

[0061] 5) During the process of the hybrid energy storage system continuously responding to AGC instructions, the ratio is calculated, the numerator part of the ratio is the amount of electricity consumed by the electric heater of the molten salt energy storage system in the process of responding to frequency adjustment instructions, with the unit of MWh, and the denominator part of the ratio is the distance quantity of the frequency adjustment instructions responded to by the molten salt energy storage system, with the unit of MW, and whenever is greater than 0.5, rebalancing of the electrochemical energy storage system is performed to adjust the SOC of the electrochemical energy storage system to C n+1 %, C n+1 =C n -1, n≥0.

[0062] In this embodiment, in step 2), the manner in which the electrochemical energy storage system responds to such AGC instructions is to charge, and when the electrochemical energy storage system SOC is charged to 100%, charging is stopped, and then the molten salt energy storage system continues to respond to such AGC instructions; the manner in which the molten salt energy storage system responds to such AGC instructions is to increase the power of the molten salt electric heater.

[0063] In this embodiment, in step 3), the manner in which the molten salt energy storage system responds to such AGC instructions is to reduce the power of the molten salt electric heater, and when the power of the molten salt electric heater is reduced to 0, responding to such AGC instructions is stopped, and then the electrochemical energy storage system continues to respond to such AGC instructions, and the manner in which the electrochemical energy storage system responds to such AGC instructions is to discharge.

[0064] Embodiment 3

[0065] A certain power plant has already built an electrochemical energy storage system, and the system diagram is as shown in Figure 2 .

[0066] However, the built electrochemical energy storage system has small capacity and cannot meet the increasing frequency modulation demand of the unit, and needs to expand or rebuild the original electrochemical energy storage system.

[0067] Meanwhile, considering the daily peak regulation demand of the unit for 2-4 hours, if the expansion scheme of the electrochemical energy storage system is adopted, the construction cost is much higher than that of the molten salt thermal storage system.

[0068] Therefore, the scheme of the application is adopted in a certain power plant, a molten salt thermal storage system is newly built on the basis of the built electrochemical energy storage system, thereby forming a molten salt and electrochemical hybrid energy storage system, wherein the electrochemical energy storage system is mainly used to respond to the frequency modulation instruction, and the molten salt energy storage system is called again in the case of insufficient frequency modulation capacity. The molten salt energy storage system is mainly used to respond to the daily peak regulation demand for 2-4 hours, and simultaneously meets the frequency modulation demand of the electrochemical energy storage system.

[0069] For the molten salt and electrochemical hybrid energy storage system, the power synthesis device and the coordination controller are introduced on the basis of the current energy storage system, and an electrical system diagram is formed as shown in Figure 1 .

[0070] Through the method of the application, on the one hand, the synergistic effect of the molten salt energy storage system and the electrochemical energy storage system is fully utilized to jointly assist the unit to respond to the AGC instruction, and on the other hand, the one-way regulation function of the molten salt energy storage system and the bidirectional regulation function of the electrochemical energy storage system are fully utilized, the advantages are complementary, the response frequency of the electrochemical energy storage system is reduced, thereby prolonging the service life of the electrochemical energy storage system, and simultaneously, the deficiency of the one-way regulation function of the molten salt energy storage system is made up by the bidirectional regulation function of the electrochemical energy storage system, thereby reducing the operation cost of the molten salt energy storage system.

[0071] The above shows and describes the basic principles and main features of the application and the advantages of the application, and for those skilled in the art, it is obvious that the application is not limited to the details of the above exemplary embodiments, and the application can be realized in other specific forms without departing from the spirit or basic characteristics of the application. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting, the scope of the application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0072] Furthermore, it should be understood that although the specification is described in terms of embodiments, each of which contains only one independent technical solution, the specification is described in this way only for the sake of clarity, and the skilled person should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that the skilled person can understand. The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made on the basis of the technical solutions according to the technical idea of the present application falls within the protection scope of the claims of the present application.

Claims

1. A control method for a molten salt and electrochemical hybrid energy storage system, characterized in that, This control method is based on a hybrid molten salt and electrochemical energy storage system, including a generator set, a coordination controller, and a power combining device. The high-voltage busbar A on the low-voltage side of the generator set's high-voltage station service transformer connects to the electrochemical energy storage system, and the high-voltage busbar B on the low-voltage side of the high-voltage station service transformer connects to the electric heater of the molten salt energy storage system. The control target of the coordination controller is the difference between the AGC command sent by the generator set's DCS and the generator power. The control objects of the coordination controller are the electrochemical energy storage system and the molten salt electric heater system. The power combining device is used to combine the power of the electrochemical energy storage system and the power of the molten salt electric heater system using a vector synthesis method and send the result to the RTU device. The positive direction of the power of the electrochemical energy storage system is consistent with the positive direction of the power of the molten salt electric heater system, both pointing from the high-voltage station service busbar towards the energy storage system. The control method includes: 1) The initial SOC of the electrochemical energy storage system is C0%, where SOC represents the charging rate of the electrochemical energy storage system, 50≤C0≤90, and the initial electric heating power of the molten salt energy storage system is 0. 2) When the power grid issues an AGC command to the generator set to adjust the power downward, the electrochemical energy storage system responds preferentially over the molten salt energy storage system; 3) When the power grid issues an AGC command to the generator set to increase the power output, the molten salt energy storage system responds preferentially over the electrochemical energy storage system; 4) During the continuous response of the hybrid energy storage system to AGC commands, whenever the SOC of the electrochemical energy storage system drops to 10% or below, a rebalancing of the electrochemical energy storage system is performed to adjust its SOC to C. n+1 %, C n+1 =C n +1, n≥0; 5) Calculate the ratio during the continuous response of the hybrid energy storage system to AGC commands. ,ratio The numerator represents the amount of electricity consumed by the electric heater in the molten salt energy storage system during the frequency modulation command response process, measured in MWh, and the ratio is... The denominator is the mileage of the frequency regulation command responded to by the molten salt energy storage system, in MW. When the value is greater than 0.5, a rebalancing of the electrochemical energy storage system is performed to adjust the SOC of the electrochemical energy storage system to C. n+1 %, C n+1 =C n -1, n≥0.

2. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that, In step 2), the electrochemical energy storage system responds to this type of AGC command by charging. When the electrochemical energy storage system's SOC is charged to 100%, charging stops, and then the molten salt energy storage system continues to respond to this type of AGC command. The molten salt energy storage system responds to this type of AGC command by increasing the power of the molten salt electric heater.

3. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that, In step 3), the molten salt energy storage system responds to such AGC commands by reducing the power of the molten salt electric heater.

4. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 3, characterized in that, In step 3), when the power of the molten salt electric heater drops to 0, it stops responding to such AGC commands, and then the electrochemical energy storage system continues to respond to such AGC commands by discharging.

5. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that, The generator set is also connected to the power grid via a main transformer.

6. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that, The coordination controller adopts a state machine control mode.

7. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 6, characterized in that, The coordinating controller operates in a cycle between three states: acquiring AGC commands and generator power information from the DCS, calculating power allocation data for the electrochemical energy storage system and the molten salt electric heater system, and sending power allocation signals to the electrochemical energy storage system and the molten salt electric heater system.

8. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 7, characterized in that, The power combining device uses FPGA technology to achieve parallel sampling of multiple channels.

9. The control method for a molten salt and electrochemical hybrid energy storage system according to claim 8, characterized in that, The power combining device transmits the power combining signals of the electrochemical energy storage system and the molten salt electric heater system to the RTU device through parallel data transmission, thereby reducing the delay in the data transmission process.

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