Molten salt and electrochemistry hybrid energy storage system and control method thereof

Abstract

The invention discloses a fused salt and electrochemistry-based hybrid energy storage system and a control method thereof. The system comprises a generator set, a coordination controller and a power synthesis device, comprising the steps that (1) the initial SOC of the electrochemical energy storage system is C < 0 >%, the SOC represents the charging rate of the electrochemical energy storage system, C < 0 > < = 50 and C < = 90, and the initial electric heating power of the fused salt energy storage system is 0; (2) when the power grid sends an AGC instruction for downwards adjusting the power to the generator set, the electrochemical energy storage system responds prior to the fused salt energy storage system; (3) when the power grid sends an AGC instruction for adjusting power upwards to the generator set, the fused salt energy storage system responds prior to the electrochemical energy storage system; (4) in the process that the hybrid energy storage system continuously responds to the AGC instruction, rebalancing the electrochemical energy storage system once and adjusting the SOC of the electrochemical energy storage system whenever the SOC of the electrochemical energy storage system is reduced to 10% or below, and (5) in the process that the hybrid energy storage system continuously responds to the AGC instruction, calculating the ratio # imgabs0 #.

Description

Technical Field

[0001] The present invention belongs to the field of power system energy storage, and in particular relates to a molten salt and electrochemical hybrid energy storage system and a control method thereof. Background Art

[0002] The existing utility model patent "An energy storage device and control system for improving the AGC frequency modulation performance of a power plant" discloses an energy storage device and control system for improving the AGC frequency modulation performance of a power plant, wherein the energy storage device includes several energy storage subsystems, each of which includes 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 "A controllable load energy storage device participating in the primary frequency regulation system of a thermal power unit" discloses a controllable load energy storage device participating in the primary frequency regulation of a thermal power unit. The device can optimize the primary frequency regulation performance of the thermal power unit with minor changes to the original thermal power unit. In actual application cases, the controllable load is mostly in the form of an electrically heated molten salt medium. The controllable load based on molten salt can overcome the defects of high investment cost and short life of the electrochemical energy storage system. However, in actual operation, the molten salt controllable load needs to operate continuously for a long time, resulting in higher operating costs. Summary of the invention

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

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A molten salt and electrochemical hybrid energy storage system, comprising a generator set, a coordination controller and a power synthesis device; The high-voltage plant bus section A on the low-voltage side of the high-voltage plant transformer of the generator set is connected to the electrochemical energy storage system, and the high-voltage plant bus section B on the low-voltage side of the high-voltage plant transformer is connected 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 unit 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 synthesis device is used to synthesize the power of the electrochemical energy storage system and the power of the molten salt electric heater system through a vector synthesis method, and send them 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, and both are directed to the energy storage system by the high-voltage plant bus.

[0006] A further improvement of the present invention is that the generator set is also connected to the power grid via a main transformer.

[0007] A further improvement of the present invention is that the coordination controller adopts a state machine control mode.

[0008] A further improvement of the present invention is that the coordination controller operates cyclically between three states, which are respectively obtaining AGC instructions and generator power information from 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.

[0009] A further improvement of the present invention is that the power synthesis device realizes multi-channel parallel sampling by adopting FPGA technology.

[0010] A further improvement of the present invention is that the power synthesis device sends the power synthesis signal 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.

[0011] A control method for a molten salt and electrochemical hybrid energy storage system, comprising: 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; 2) When the power grid issues an AGC instruction to the generator set to adjust the power downward, the electrochemical energy storage system responds before the molten salt energy storage system; 3) When the power grid issues an AGC instruction to the generator set to adjust the power upward, the molten salt energy storage system responds before the electrochemical energy storage system; 4) During the process of the hybrid energy storage system continuously responding to the AGC command, whenever the SOC of the electrochemical energy storage system drops to 10% or below, the electrochemical energy storage system is rebalanced and the SOC of the electrochemical energy storage system is adjusted to C n+1 %,C n+1 =C n +1, n≥0; 5) Calculate the ratio while the hybrid energy storage system continues to respond to the AGC command ,ratio The numerator is the power consumed by the electric heater in the process of the molten salt energy storage system responding to the frequency modulation command, and its unit is MWh. The denominator of is the mileage of the frequency modulation command responded by the molten salt energy storage system, and its unit is MW. When it is greater than 0.5, the electrochemical energy storage system is rebalanced and the SOC of the electrochemical energy storage system is adjusted to C n+1 %,C n+1 =C n -1, n≥0.

[0012] A further improvement of the present invention is that, in step 2), the electrochemical energy storage system responds to such AGC instructions by charging, and when the SOC of the electrochemical energy storage system is charged to 100%, 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.

[0013] A further improvement of the present invention is 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.

[0014] A further improvement of the present invention is that in step 3), when the power of the molten salt electric heater is reduced to 0, it stops responding to such AGC instructions, 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.

[0015] Compared with the prior art, the present invention has at least the following beneficial technical effects: The present invention provides a hybrid energy storage system based on molten salt and electrochemistry and a control method thereof. The system can coordinate the order in which the electrochemical energy storage system and the molten salt energy storage system respond to the AGC instructions based on the unified control target of the AGC instructions and the generator power difference, avoid insufficient response or excessive response caused by the lack of coordination between the two systems, give full play to the synergistic effect of the molten salt energy storage system and the electrochemical energy storage system, and jointly assist the unit in responding to the AGC instructions.

[0016] Furthermore, the present invention has a self-regulating function and can adapt to different frequency modulation conditions. It can adjust the response strategy through rebalancing according to historical frequency modulation conditions, thereby adapting to the frequency modulation conditions of different power grids.

[0017] Furthermore, the present invention makes full use of the unidirectional regulation function of the molten salt energy storage system and the bidirectional regulation function of the electrochemical energy storage system, complementing each other's advantages, reducing the response frequency of the electrochemical energy storage system, thereby extending the life of the electrochemical energy storage system. At the same time, the bidirectional regulation function of the electrochemical energy storage system makes up for the deficiency of the unidirectional regulation function of the molten salt energy storage system, thereby reducing the operating cost of the molten salt energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a structural block diagram of a molten salt and electrochemical hybrid energy storage system of the present invention.

[0020] Figure 2 1 is a structural block diagram of an electrochemical energy storage system that has been built in a power plant in the embodiment. DETAILED DESCRIPTION

[0021] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0022] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0024] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0025] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0026] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0027] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0028] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0029] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0030] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] Example 1 like Figure 1 As shown, the present invention provides a molten salt and electrochemical hybrid energy storage system, including a generator set, a coordination controller and a power synthesis device; The high-voltage plant bus section A on the low-voltage side of the high-voltage plant transformer of the generator set is connected to the electrochemical energy storage system, and the high-voltage plant bus section B on the low-voltage side of the high-voltage plant transformer is connected to the electric heater of the molten salt energy storage system; The control target of the coordinated controller is the difference between the AGC command sent by the unit DCS (distributed control system) and the generator power, and its control objects are the electrochemical energy storage system and the molten salt electric heater system; The power synthesis device synthesizes the power of the electrochemical energy storage system and the power of the molten salt electric heater system through a vector synthesis method, and sends them 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, and the high-voltage plant bus points to the energy storage system.

[0032] The present invention improves energy utilization efficiency and flexibility: by combining the generator set, electrochemical energy storage system and molten salt energy storage system, the system can flexibly adjust the output power according to the grid demand or AGC (automatic generation control) instructions, effectively improving the efficiency and flexibility of energy utilization. The electrochemical energy storage system can quickly respond to the instantaneous demand of the grid, while the molten salt energy storage system can provide long-term stable energy storage. The combination of the two realizes the complementarity of short-term and long-term energy storage.

[0033] The present invention enhances system stability and reliability: 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 electrochemical energy storage and molten salt energy storage, improving the output capacity and reliability of the overall system.

[0034] The present invention optimizes energy allocation and reduces operating costs: the system can intelligently select electrochemical energy storage or molten salt energy storage according to the grid load and electricity price to optimize energy allocation and reduce operating costs. For example, when electricity prices are low, the electric heater of the molten salt energy storage system can be used to store energy, while when electricity prices are high or grid demand increases, energy can be released through the electrochemical energy storage system or the molten salt energy storage system, thereby reducing electricity costs.

[0035] The present invention improves the intelligence level of the system: the use of the coordinated controller reflects the intelligence and automation level of the system, reduces manual intervention, and improves the response speed and accuracy of the system. The power synthesis device realizes the precise synthesis of electrochemical energy storage and molten salt energy storage power through the vector synthesis method, further improving the intelligence level of the system.

[0036] The present invention 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. By combining with renewable energy, the system helps to promote the widespread access and utilization of renewable energy and promote the optimization and transformation of energy structure.

[0037] In this embodiment, the generator set is also connected to the grid via a main transformer.

[0038] In this embodiment, the coordination controller adopts a state machine control mode, and the coordination controller cycles between three states. The three states are obtaining AGC instructions and generator power information from 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.

[0039] In this embodiment, the power synthesis device implements multi-channel parallel sampling by adopting FPGA technology.

[0040] In this embodiment, the power synthesis device sends the power synthesis signal 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.

[0041] Example 2 The present invention provides a control method for a molten salt and electrochemical hybrid energy storage system, comprising: 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; 2) When the power grid issues an AGC instruction to the generator set to adjust the power downward, the electrochemical energy storage system responds before the molten salt energy storage system; 3) When the power grid issues an AGC instruction to the generator set to adjust the power upward, the molten salt energy storage system responds before the electrochemical energy storage system; 4) During the process of the hybrid energy storage system continuously responding to the AGC command, whenever the SOC of the electrochemical energy storage system drops to 10% or below, the electrochemical energy storage system is rebalanced and the SOC of the electrochemical energy storage system is adjusted to C n+1 %,C n+1 =Cn +1, n≥0; 5) Calculate the ratio while the hybrid energy storage system continues to respond to the AGC command ,ratio The numerator is the power consumed by the electric heater in the process of the molten salt energy storage system responding to the frequency modulation command, and its unit is MWh. The denominator of is the mileage of the frequency modulation command responded by the molten salt energy storage system, and its unit is MW. When it is greater than 0.5, the electrochemical energy storage system is rebalanced and the SOC of the electrochemical energy storage system is adjusted to C n+1 %,C n+1 =C n -1, n≥0.

[0042] In this embodiment, in step 2), the electrochemical energy storage system responds to such AGC instructions by charging, and stops charging when the SOC of the electrochemical energy storage system is charged to 100%, 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; In this embodiment, in step 3), the molten salt energy storage system responds to such AGC instructions by reducing the power of the molten salt electric heater. When the power of the molten salt electric heater is reduced to 0, the system stops responding to such AGC instructions, and then the electrochemical energy storage system continues to respond to such AGC instructions. The electrochemical energy storage system responds to such AGC instructions by discharging.

[0043] Example 3 A power plant has already built an electrochemical energy storage system, the system diagram is as follows: Figure 2 shown.

[0044] However, the existing electrochemical energy storage system has a small capacity and cannot meet the increasing frequency regulation needs of the units, so the original electrochemical energy storage system needs to be expanded or rebuilt.

[0045] At the same time, considering the unit's peak-shaving demand of 2 to 4 hours a day, if the solution of expanding the electrochemical energy storage system is adopted, the construction cost will be much higher than that of the molten salt heat storage system.

[0046] Therefore, a certain power plant adopts the scheme of the present invention, and builds a new molten salt heat storage system on the basis of the already built electrochemical energy storage system, thereby forming a molten salt and electrochemical hybrid energy storage system, in which the electrochemical energy storage system is mainly used to respond to frequency modulation instructions, and when the frequency modulation capacity is insufficient, the molten salt energy storage system is called. The molten salt energy storage system is mainly used to respond to the peak regulation demand of 2 to 4 hours per day, while taking into account the frequency modulation demand of the supplementary electrochemical energy storage system.

[0047] For the molten salt and electrochemical hybrid energy storage system, based on the current energy storage system, a power synthesis device and a coordinated controller are introduced to form an electrical system diagram as shown in the figure below. Figure 1 shown.

[0048] Through the method of the present invention, 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 in responding to the AGC instruction, and on the other hand, the unidirectional regulation function of the molten salt energy storage system and the bidirectional regulation function of the electrochemical energy storage system are fully utilized to complement each other's advantages, thereby reducing the response frequency of the electrochemical energy storage system, thereby extending the life of the electrochemical energy storage system. At the same time, the bidirectional regulation function of the electrochemical energy storage system makes up for the deficiency of the unidirectional regulation function of the molten salt energy storage system, thereby reducing the operating cost of the molten salt energy storage system.

[0049] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0050] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A molten salt and electrochemical hybrid energy storage system, characterized in that: It includes a generator set, a coordination controller and a power synthesis device; The high-voltage plant bus section A on the low-voltage side of the high-voltage plant transformer of the generator set is connected to the electrochemical energy storage system, and the high-voltage plant bus section B on the low-voltage side of the high-voltage plant transformer is connected 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 unit 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 synthesis device is used to synthesize the power of the electrochemical energy storage system and the power of the molten salt electric heater system through a vector synthesis method, and send them 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, and both are directed to the energy storage system by the high-voltage plant bus.

2. A molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that: The generator sets are also connected to the grid via the main transformer.

3. A molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that: The coordination controller adopts the state machine control mode.

4. A molten salt and electrochemical hybrid energy storage system according to claim 3, characterized in that: The coordination controller operates in a cycle between three states, which are obtaining AGC instructions and generator power information from 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.

5. A molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that: The power synthesis device realizes multi-channel parallel sampling by adopting FPGA technology.

6. A molten salt and electrochemical hybrid energy storage system according to claim 5, characterized in that: The power synthesis device sends the power synthesis signal 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.

7. The control method of a molten salt and electrochemical hybrid energy storage system according to claim 1, characterized in that: include: 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; 2) When the power grid issues an AGC instruction to the generator set to adjust the power downward, the electrochemical energy storage system responds before the molten salt energy storage system; 3) When the power grid issues an AGC instruction to the generator set to adjust the power upward, the molten salt energy storage system responds before the electrochemical energy storage system; 4) During the process of the hybrid energy storage system continuously responding to the AGC command, whenever the SOC of the electrochemical energy storage system drops to 10% or below, the electrochemical energy storage system is rebalanced and the SOC of the electrochemical energy storage system is adjusted to C n+1 %,C n+1 =C n +1, n≥0; 5) Calculate the ratio while the hybrid energy storage system continues to respond to the AGC command ,ratio The numerator is the power consumed by the electric heater in the process of the molten salt energy storage system responding to the frequency modulation command, and its unit is MWh. The denominator of is the mileage of the frequency modulation command responded by the molten salt energy storage system, and its unit is MW. When it is greater than 0.5, the electrochemical energy storage system is rebalanced and the SOC of the electrochemical energy storage system is adjusted to C n+1 %,C n+1 =C n -1, n≥0.

8. The control method of a molten salt and electrochemical hybrid energy storage system according to claim 7, characterized in that: In step 2), the electrochemical energy storage system responds to such AGC instructions by charging. When the SOC of the electrochemical energy storage system is charged to 100%, 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.

9. The control method of a molten salt and electrochemical hybrid energy storage system according to claim 7, characterized in 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.

10. A control method for a molten salt and electrochemical hybrid energy storage system according to claim 9, characterized in that: In step 3), when the power of the molten salt electric heater is reduced to 0, it stops responding to such AGC instructions, and then the electrochemical energy storage system continues to respond to such AGC instructions. The electrochemical energy storage system responds to such AGC instructions by discharging.

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