Frequency modulation system and method for coupling electrochemical energy storage power station with super capacitor energy storage

Abstract

The invention relates to the technical field of electric power energy storage frequency modulation, in particular to a frequency modulation system and method for coupling an electrochemical energy storage power station with super capacitor energy storage, and the system comprises a lithium battery energy storage unit which is connected to a power grid through a converter cabin, an energy storage boost transformer and an energy storage grid-connected switch; the super capacitor energy storage unit is connected to a power grid through a converter bin, an energy storage boost transformer and an energy storage grid-connected switch; the lithium battery energy storage unit and the super capacitor energy storage unit are connected to a power grid in parallel and are connected to the low-voltage side of the energy storage boost transformer through independent converters. The method has the beneficial effects that the advantages of long cycle life and high charge-discharge rate of the super capacitor are adopted, and the service life and the economic benefit of the energy storage power station are remarkably improved. Meanwhile, a power grid frequency deviation signal is decomposed through first-order high-pass filtering, precise response of energy storage of the super capacitor and the lithium battery according to frequency characteristics is achieved, and the coordination control efficiency and the utilization rate of the hybrid energy storage system are optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of power energy storage and frequency modulation, and in particular to a frequency modulation system and method for coupling supercapacitor energy storage in an electrochemical energy storage power station. Background Art

[0002] At present, new energy storage power stations are mainly based on electrochemical energy storage. Electrochemical energy storage has the advantages of high energy density, mature technology, and low system cost. Therefore, it is widely used in long-term and large-capacity energy storage occasions. However, due to the randomness and volatility of new energy power generation, the frequency of energy storage power stations needs to be charged and discharged for frequency regulation. The disadvantages of electrochemical energy storage are low power density and few cycles (3000-8000 times). Therefore, when a single electrochemical energy storage participates in a frequency modulation, it will shorten the battery life, thereby reducing the reliability and economy of the system. At the same time, the high frequency of participating in a frequency modulation will cause the battery system temperature to rise too high, bringing safety risks. Summary of the invention

[0003] In view of the above problems or problems existing in the prior art, the present invention is proposed.

[0004] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0005] In the first aspect, the present invention provides the following technical solutions: a frequency modulation system and method for coupling supercapacitor energy storage in an electrochemical energy storage power station, which includes a lithium battery energy storage unit, which is connected to the power grid through a converter compartment, an energy storage boost transformer, and an energy storage grid-connected switch;

[0006] The supercapacitor energy storage unit is connected to the power grid through the converter compartment, energy storage boost transformer, and energy storage grid-connected switch;

[0007] The lithium battery energy storage unit and the supercapacitor energy storage unit are connected to the power grid in parallel, and are connected to the energy storage boost-to-low voltage side through independent converters respectively.

[0008] As a preferred solution of the frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, wherein: the lithium battery energy storage unit is composed of a plurality of first prefabricated cabin-type energy storage modules.

[0009] As a preferred solution of the frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, the supercapacitor energy storage unit is composed of a plurality of second prefabricated cabin-type energy storage modules.

[0010] In a second aspect, the present invention provides the following technical solutions: a frequency modulation method for coupling supercapacitor energy storage in an electrochemical energy storage power station, comprising transmitting a collected frequency deviation signal to a coordinated control system;

[0011] Performing feature decomposition on the frequency deviation signal to obtain a high-frequency frequency fluctuation signal and a low-frequency frequency fluctuation signal;

[0012] According to the frequency deviation signal, two sets of energy storage power instructions are calculated respectively;

[0013] The power command is sent to the energy storage converter through a coordinated control system.

[0014] As a preferred solution of the frequency modulation method of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, wherein: characteristic decomposition is to decompose the frequency deviation signal using a first-order high-pass filter.

[0015] As a preferred solution of the frequency modulation method of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, the control system calculates the power instruction according to the rated frequency of the power grid and the total rated power of the energy storage power station, as well as the primary frequency modulation difference rate.

[0016] As a preferred solution of the frequency modulation method of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, the calculation formula of the power instruction is:

[0017]

[0018] Among them, δ% is the frequency modulation error rate, △f is the frequency deviation, and f n is the rated frequency of the power grid, P n is the total rated power of the energy storage power station.

[0019] As a preferred solution of the frequency modulation method of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, it also includes monitoring the state of charge (SOC) of the energy storage system and adjusting the frequency modulation droop control coefficient based on the real-time energy storage SOC.

[0020] As a preferred solution of the frequency modulation method of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, the droop control coefficient is adjusted by dynamically adjusting the primary frequency modulation difference rate δ% of the two energy storage units.

[0021] As a preferred solution of the frequency modulation method of the electrochemical energy storage power station coupled with supercapacitor energy storage of the present invention, the energy storage converter includes at least one converter serving supercapacitor energy storage and one converter serving lithium battery energy storage.

[0022] Beneficial effects of the present invention: By taking advantage of the long cycle life and high charge and discharge rate of supercapacitors, the life and economic benefits of energy storage power stations are significantly improved. At the same time, by decomposing the grid frequency deviation signal through first-order high-pass filtering, the precise response of supercapacitor and lithium battery energy storage according to frequency characteristics is achieved, and the coordinated control efficiency and utilization rate of the hybrid energy storage system are optimized. In addition, a variable droop coefficient control method is adopted to dynamically adjust the output according to the real-time state of charge (SOC) of the energy storage unit, ensuring the safety and reliability of the energy storage system when responding to the primary frequency modulation of the grid, effectively avoiding overcharging and over-discharging, and further improving the stability and reliability of the system. These innovations work together to provide the grid with a more efficient, stable and safe frequency modulation service, which has significant social benefits and market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0024] Figure 1 It is the primary system structure of supercapacitor hybrid lithium battery energy storage.

[0025] Figure 2 This is a diagram of a supercapacitor hybrid lithium battery energy storage primary frequency modulation system.

[0026] Figure 3 This is a flow chart of the primary frequency modulation method for supercapacitor hybrid lithium battery energy storage. DETAILED DESCRIPTION

[0027] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0028] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0029] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0030] Example 1

[0031] Reference Figure 1 , which is the first embodiment of the present invention, and which provides a frequency modulation system for coupling supercapacitor energy storage to an electrochemical energy storage power station, which includes a lithium battery energy storage unit, and is connected to the power grid through a converter compartment, an energy storage boost transformer, and an energy storage grid-connected switch;

[0032] The supercapacitor energy storage unit is connected to the power grid through the converter compartment, energy storage boost transformer, and energy storage grid-connected switch;

[0033] The lithium battery energy storage unit and the supercapacitor energy storage unit are connected to the power grid in parallel, and are connected to the energy storage boost-to-low voltage side through independent converters respectively.

[0034] Furthermore, the lithium battery energy storage unit is composed of a plurality of first prefabricated cabin-type energy storage modules.

[0035] It should be noted that the battery cells are cascaded to form a PACK, and then multiple groups of PACKs are cascaded to form a cluster, and multiple clusters of batteries are cascaded to eventually form a first prefabricated cabin-type energy storage module.

[0036] It should be further explained that, in conjunction with the Figure 1 , each energy storage battery cluster is connected to a set of converters (#nPCS, where n is the number of battery clusters), and then collected and connected in parallel to the #1 energy storage boost-to-low voltage side. Further, the lithium battery energy storage is connected to the energy storage power station system through the energy storage grid-connected switch 601 after being boosted to low voltage.

[0037] Furthermore, the supercapacitor energy storage unit is composed of a plurality of second prefabricated cabin-type energy storage modules.

[0038] It should be noted that the supercapacitor cells are cascaded to form a PACK, and then multiple groups of PACKs are cascaded to form a cluster, and multiple clusters of supercapacitors are cascaded to eventually form a second prefabricated cabin-type energy storage module.

[0039] It should be further explained that, in conjunction with the Figure 1 Each supercapacitor cluster is connected to a set of converters (#nPCS, where n is the number of battery clusters), and then collected and connected in parallel to the #2 energy storage boost-to-low voltage side. Further, after the supercapacitor energy storage is boosted to low voltage, it is connected to the energy storage power station system through the energy storage grid-connected switch 602.

[0040] Preferably, supercapacitors have the advantages of high cycle number, fast charge and discharge speed, and high charge and discharge power in a short time. Frequent charging and discharging will not affect their life and safety. At the same time, supercapacitor hybrid battery energy storage can achieve complementary advantages, improve the safety and life of the battery energy storage system, and effectively improve the effect of photovoltaic participation in primary frequency modulation.

[0041] In summary, the beneficial effect of the frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage in the present invention is that the lithium battery energy storage unit is combined with the supercapacitor energy storage unit, and the characteristics of the supercapacitor are long cycle life and high charge and discharge rate, which reduces the number of frequency modulation actions of the lithium battery at one time, and effectively improves the life of the energy storage power station.

[0042] Example 2

[0043] Reference Figure 2-3 , which is the second embodiment of the present invention, provides a frequency modulation method for coupling supercapacitor energy storage in an electrochemical energy storage power station, which includes.

[0044] S1. Transmit the collected frequency deviation signal to the coordinated control system.

[0045] It should be noted that the frequency regulation control procedure will only begin when the grid frequency acquisition device detects a frequency signal deviation and the deviation value exceeds the regulation dead zone of the energy storage power station.

[0046] S2. Perform feature decomposition on the frequency deviation signal to obtain a high-frequency frequency fluctuation signal and a low-frequency frequency fluctuation signal.

[0047] It should be noted that, considering the long cycle life of supercapacitors, high-frequency frequency fluctuations are responded to by supercapacitors, and low-frequency frequency fluctuations are responded to by lithium batteries.

[0048] Furthermore, the characteristic decomposition is to decompose the frequency deviation signal using a first-order high-pass filter.

[0049] It should be noted that the grid frequency deviation △f is decomposed by first-order high-pass filtering to obtain high-frequency frequency fluctuation signals △f H and low frequency fluctuation signal △f L The frequency deviation signal after further decomposition passes through a frequency modulation dead zone, and the dead zone for both energy storage is set to 0.05Hz.

[0050] S3. According to the frequency deviation signal, two sets of energy storage power instructions are calculated respectively.

[0051] It should be noted that the two sets of energy storage power instructions are the power control instructions △P of the supercapacitor and lithium battery energy storage units. SC_ref and △P LI_ref .

[0052] It should be further explained that when the lithium battery energy storage unit responds to a frequency modulation, if the power limit is reached, the power deviation part is responded by the supercapacitor, and this part of the power instruction is △P LI _ SC。

[0053] Furthermore, the control system calculates the power command according to the rated frequency of the power grid and the total rated power of the energy storage power station, as well as the primary frequency regulation rate.

[0054] Furthermore, the calculation formula of the power command is:

[0055]

[0056] Among them, δ% is the frequency modulation error rate, △f is the frequency deviation, and f n is the rated frequency of the power grid, P n is the total rated power of the energy storage power station.

[0057] It should be noted that the primary frequency modulation droop coefficients of supercapacitor and lithium battery energy storage are:

[0058]

[0059] Among them, δ1% and δ2% are the primary frequency modulation rates of supercapacitor and lithium battery energy storage respectively.

[0060] S4. Send the power command to the energy storage converter through the coordinated control system.

[0061] Furthermore, the energy storage converter includes at least one converter serving supercapacitor energy storage and one converter serving lithium battery energy storage.

[0062] Furthermore, it also includes monitoring the state of charge (SOC) of the energy storage system and adjusting the frequency droop control coefficient based on the real-time energy storage SOC.

[0063] It should be noted that if the capacity of the energy storage system is not monitored and managed, the energy storage system is prone to overcharging and over-discharging when responding to long-term primary frequency modulation. Therefore, it is necessary to monitor the energy storage SOC and adjust the primary frequency modulation droop control coefficient based on the real-time energy storage SOC to keep the energy storage capacity in a healthy state.

[0064] Furthermore, the droop control coefficient is adjusted by dynamically adjusting the primary frequency modulation difference rate δ% of the two energy storage units.

[0065] It should be noted that the larger the droop coefficient value, the greater the energy storage output under the same frequency deviation. However, if the power system experiences long-term frequency fluctuations, an excessively large droop coefficient can easily cause the energy storage system SOC to reach the limit. Therefore, the droop coefficient is changed by dynamically adjusting the adjustment rate δ% of the two energy storage units.

[0066] It should be further explained that the output of the supercapacitor and lithium battery energy storage is finally superimposed on the energy storage PMU (phasor measurement and control unit) and sent to the grid.

[0067] In summary, the beneficial effect of the frequency modulation method of an electrochemical energy storage power station coupled with supercapacitor energy storage in the present invention is to decompose the grid frequency deviation signal through a first-order high-pass filter, realize the precise response of supercapacitor and lithium battery energy storage according to the frequency characteristics, and optimize the coordinated control efficiency and utilization rate of the hybrid energy storage system. In addition, a variable droop coefficient control method is adopted to dynamically adjust the output according to the real-time state of charge (SOC) of the energy storage unit, thereby ensuring the safety and reliability of the energy storage system in response to the primary frequency modulation of the grid, effectively avoiding overcharging and over-discharging, and further improving the stability and reliability of the system. These innovative points work together to provide the power grid with a more efficient, stable and safe frequency modulation service, which has significant social benefits and market application prospects.

[0068] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A frequency modulation system for electrochemical energy storage power station coupled with supercapacitor energy storage, characterized in that: include, The lithium battery energy storage unit is connected to the power grid through the converter compartment, energy storage boost transformer, and energy storage grid-connected switch; The supercapacitor energy storage unit is connected to the power grid through the converter compartment, energy storage boost transformer, and energy storage grid-connected switch; The lithium battery energy storage unit and the supercapacitor energy storage unit are connected to the power grid in parallel, and are connected to the energy storage boost-to-low voltage side through independent converters respectively.

2. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 1, characterized in that: The lithium battery energy storage unit is composed of a plurality of first prefabricated cabin-type energy storage modules.

3. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 2, characterized in that: The supercapacitor energy storage unit is composed of a plurality of second prefabricated cabin-type energy storage modules.

4. A frequency modulation method for electrochemical energy storage power station coupled with supercapacitor energy storage, applied to the frequency modulation system for electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in any one of claims 1 to 3, characterized in that: Transmitting the collected frequency deviation signal to the coordinated control system; Performing feature decomposition on the frequency deviation signal to obtain a high-frequency frequency fluctuation signal and a low-frequency frequency fluctuation signal; According to the frequency deviation signal, two sets of energy storage power instructions are calculated respectively; The power command is sent to the energy storage converter through a coordinated control system.

5. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 4, characterized in that: The characteristic decomposition is to decompose the frequency deviation signal using a first-order high-pass filter.

6. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 5, characterized in that: The control system calculates the power instruction according to the rated frequency of the power grid, the total rated power of the energy storage power station, and the primary frequency regulation rate.

7. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 6, characterized in that: The calculation formula of the power command is: Among them, δ% is the frequency modulation error rate, △f is the frequency deviation, f n is the rated frequency of the power grid, P n is the total rated power of the energy storage power station.

8. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 7, characterized in that: It also includes monitoring the state of charge (SOC) of the energy storage system and adjusting the frequency droop control coefficient based on the real-time energy storage SOC.

9. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage as claimed in claim 8, characterized in that: The droop control coefficient is adjusted by dynamically adjusting the primary frequency modulation difference rate δ% of the two energy storage units.

10. The frequency modulation system of the electrochemical energy storage power station coupled with supercapacitor energy storage according to any one of claims 5 to 9, characterized in that: The energy storage converter includes at least one converter serving supercapacitor energy storage and one converter serving lithium battery energy storage.

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