A balanced control method and strategy for a chain energy storage system

Abstract

The present invention discloses a balanced control method and strategy for a chain energy storage system, wherein the method includes the following steps: calculating the difference between the average state of charge of the three-phase commutation chain and the average state of charge of each phase commutation chain to obtain the state of charge difference of each phase commutation chain; calculating the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain to obtain a superimposed active power reference value of each phase commutation chain; superimposing the superimposed active power reference value to the active power reference value of the corresponding commutation chain to obtain a final active power reference value of each phase commutation chain; calculating the active current reference value of each phase commutation chain based on the final active power reference value of each phase commutation chain; and regulating the instantaneous current of each phase commutation chain based on the active current reference value of each phase commutation chain. The present invention can achieve balanced state of charge control in a chain energy storage system while avoiding overmodulation.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage and reactive power compensation system control, and in particular relates to a balanced control method and strategy for a chain energy storage system. Background Art

[0002] When large-scale renewable energy is connected to the AC grid, the randomness and volatility of wind and solar energy, as well as the lack of inertia and weak damping characteristics of wind and photovoltaic units, can cause significant power and frequency disturbances in the grid. Furthermore, the interaction between the converter and the grid can lead to emerging stability issues such as broadband oscillations, which can cause unit tripping and even equipment damage, endangering the safe and stable operation of the grid. To address these issues, deploying reactive power compensation devices and large-scale energy storage devices at large-scale renewable energy stations will become the norm in future large-scale renewable energy development. Chain energy storage systems have broad application prospects in large-scale renewable energy station grid-connected systems.

[0003] Because chain-type energy storage converters consist of numerous single-phase H-bridge modules, each with independent storage cells, it is important to consider balancing the state of charge (SOC) of each cell. To address the imbalances in SOC within and between phases in chain-type energy storage systems, a balancing control strategy is urgently needed. Summary of the Invention

[0004] To address the above-mentioned issues, the present invention adopts a technical solution: a balancing control method for a chain-type energy storage system, wherein each phase of a three-phase commutation chain in the chain-type energy storage system includes a plurality of power modules connected in series, and each of the power modules includes an energy storage battery; the balancing control method includes a method for balancing the state of charge of each power module between the three-phase commutation chains, and the method for balancing the state of charge of each power module between the three-phase commutation chains includes the following steps:

[0005] Calculate the difference between the average state of charge of the three-phase commutation chain and the average state of charge of each phase commutation chain to obtain the state of charge difference of each phase commutation chain;

[0006] Calculate the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain to obtain the superimposed active power reference value of each phase commutation chain;

[0007] Superimposing the superimposed active power reference value onto the corresponding commutation chain active power reference value to obtain a final active power reference value of each phase commutation chain;

[0008] Calculating an active current reference value of each phase commutation chain according to the final active power reference value of each phase commutation chain;

[0009] The instantaneous current of each phase commutation chain is regulated according to the active current reference value of each phase commutation chain.

[0010] Optionally, after calculating the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain, the method further includes limiting the product result.

[0011] Optionally, in the calculation of the active current reference value of each phase commutation chain, specifically:

[0012] The difference between the final reference value of active power and the measured value of active power of each phase commutation chain is calculated, and PI adjustment is performed to obtain the active current reference value of the fixed active power control mode of each phase commutation chain.

[0013] Optionally, the balancing control method further includes a method for balancing the state of charge of each power module in each phase commutation chain, and the method for balancing the state of charge of each power module in each phase commutation chain includes the following steps:

[0014] Calculating the difference between the actual state of charge of each power module in the commutation chain and the average state of charge of the power modules in the commutation chain to obtain the power module state of charge difference of each power module;

[0015] The voltage modulation wave of each power module is adjusted according to the difference in the state of charge of the power modules to control the charge and discharge rate of each power module.

[0016] Optionally, the step of adjusting the voltage modulation wave of each power module according to the state of charge difference of the power modules includes the following steps:

[0017] Calculate the product of the state of charge difference of each power module, the state of charge balance coefficient in the commutation chain, and the commutation chain current to obtain the superimposed voltage reference wave of each power module;

[0018] The superimposed voltage reference wave is superimposed on the commutation chain voltage modulation wave output by the inner loop controller to adjust the voltage modulation wave of each power module.

[0019] And, a balancing control strategy for a chain energy storage system, wherein each phase commutation chain in the chain energy storage system includes a plurality of power modules connected in series, and each of the power modules includes an energy storage battery; the balancing control strategy includes an inter-commutation chain balancing control strategy, and the inter-commutation chain balancing control strategy includes:

[0020] a state of charge difference calculation unit, configured to calculate the difference between the average state of charge of the three-phase commutation chain and the average state of charge of each phase commutation chain, to obtain the state of charge difference of each phase commutation chain;

[0021] a power calculation unit, configured to calculate the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain to obtain a superimposed active power reference value of each phase commutation chain; and further configured to superimpose the superimposed active power reference value onto the active power reference value of the corresponding commutation chain to obtain a final active power reference value of each phase commutation chain;

[0022] a current calculation unit, configured to calculate an active current reference value of each phase commutation chain according to a final active power reference value of each phase commutation chain;

[0023] The current regulating unit is used to regulate the instantaneous current of each phase commutation chain according to the active current reference value of each phase commutation chain.

[0024] Optionally, when the current calculation unit calculates the active current reference value of each phase commutation chain, it is specifically as follows:

[0025] The difference between the final reference value of active power and the measured value of active power of each phase commutation chain is calculated, and PI adjustment is performed to obtain the active current reference value of the fixed active power control mode of each phase commutation chain.

[0026] Optionally, the state of charge difference calculation unit is further configured to calculate a difference between an actual state of charge value of each power module in the commutation chain and an average state of charge value of the power modules in the commutation chain, to obtain a power module state of charge difference of each power module.

[0027] Optionally, the balancing control strategy further includes a balancing control strategy within a commutation chain, and the balancing control strategy within a commutation chain includes:

[0028] The reference voltage adjustment unit is used to adjust the voltage modulation wave of each power module according to the difference in the state of charge of the power modules, so as to control the charge and discharge rate of each power module.

[0029] Optionally, the balancing control strategy within the commutation chain further includes:

[0030] The reference voltage calculation unit is used to calculate the product of the state of charge difference of each power module, the state of charge balancing coefficient in the commutation chain, and the commutation chain current to obtain the superimposed voltage reference wave of each power module; and is also used to superimpose the superimposed voltage reference wave on the commutation chain voltage modulation wave output by the inner loop controller to obtain the voltage reference wave of each power module.

[0031] Optionally, when the voltage regulating unit regulates the voltage modulation wave of each power module, specifically:

[0032] The voltage reference wave is used as a voltage modulation wave of a corresponding power module for adjustment.

[0033] By adopting the above-mentioned technical solution, the present invention has the following beneficial effects: it can realize the charge state balancing control in the chain energy storage system, ensuring the important control strategy of maximizing the output of the energy storage battery under the premise of safety, while avoiding overmodulation, thereby expanding the scope of application of the balancing control strategy.

[0034] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 The topology of the chain energy storage system according to an embodiment of the present invention is shown;

[0037] Figure 2 A schematic diagram of the charge state balancing principle of power units in a commutation chain according to an embodiment of the present invention is shown;

[0038] Figure 3 A schematic diagram illustrating a principle of balancing the state of charge of power units between commutation chains according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0040] like Figure 1 The chain energy storage system topology of the embodiment of the present invention shown in FIG1 includes three-phase commutation chains, namely phase a, phase b and phase c. Each phase commutation chain includes multiple power modules SM connected in series, and each power module includes an energy storage battery. The number of power modules in each commutation chain is set to n. X , X=a, b, c.

[0041] The balanced control method of the chain energy storage system according to the embodiment of the present invention includes a balanced control method for the state of charge of each power module in each phase commutation chain and a balanced control method for the state of charge of each power module between three-phase commutation chains, which are specifically as follows:

[0042] 1. When controlling the charge state balance of each power module in each phase commutation chain, if Figure 2 The schematic diagram of the charge state balancing principle of the power units in the commutation chain according to the embodiment of the present invention includes the following steps:

[0043] S11: Calculate the average state of charge of each power module in the commutation chain As a reference value for the state of charge of each power module in the commutation chain, the formula is as follows:

[0044]

[0045] Where X represents the commutation chain of each phase, X=a, b, c, SOC Xi Indicates the charge state of the i-th power module in the X-phase commutation chain, i = 1, 2...n X ;

[0046] S12: Calculate the difference between the actual state of charge value of each power module in the commutation chain and the reference state of charge value of the power module in the commutation chain, that is, Denote as the power module state of charge difference of each power module;

[0047] S13: According to the state of charge difference of the power modules, the voltage modulation wave of each power module is adjusted to control the charge and discharge rate of each power module. Xi Less than the state of charge reference value When the active power of the power module needs to be increased, the state of charge value of the power module is increased; when the state of charge value SOC Xi Greater than the state of charge reference value , it is necessary to reduce the active power of the power module, thereby reducing the state of charge value of the power module;

[0048] In step S13, specifically, the following steps are included:

[0049] S131: By calculating the state of charge difference of each power module and the charge state balance coefficient K in the commutation chain (the K value of each commutation chain is the same, K is generally very small, and is an adjustable coefficient that can be dynamically adjusted) and the commutation chain current i X The product of Obtain the superimposed voltage reference wave of each power module and perform amplitude limiting to limit the superimposed voltage reference wave to prevent overmodulation;

[0050] S132: Superimpose the superimposed voltage reference wave on the commutation chain voltage modulation wave u output by the inner loop controller X-ref , get the voltage reference wave u of each power module Xi-ref , the formula is as follows:

[0051]

[0052] Through u Xi-ref The voltage modulation wave of each power module is adjusted to control the charge and discharge rate of each power module so that the charge state of each power module gradually tends to be consistent.

[0053] In summary, for phases a, b, and c, the overall formulas are:

[0054]

[0055]

[0056]

[0057] Where n a 、n b 、n c Respectively represent the number of power modules of phases a, b, and c. Generally, n a =n b =n c .

[0058] 2. When controlling the charge state balance of each power module between the three-phase commutation chains, if Figure 3 The schematic diagram of the charge state balancing principle of power units between commutation chains according to an embodiment of the present invention includes the following steps:

[0059] S21: Calculate the average state of charge of the three-phase commutation chain Average state of charge of each phase commutation chain

[0060]

[0061] S22: Calculate the average state of charge of the three-phase commutation chain The average state of charge of each phase commutation chain The difference, that is Obtain the state of charge difference of each phase commutation chain;

[0062] S23: Calculate the state of charge difference of each phase commutation chain and the charge state balance coefficient C1 between commutation chains and the corresponding commutation chain active power reference value P ref The product of the absolute values ​​of Figure 3ABS is the absolute value function); and limit the active power output of each phase commutation chain to not exceed the power range of a single phase, and obtain the superimposed active power reference value P of each phase commutation chain refSOC , the formula is as follows:

[0063]

[0064] S24: superimpose the active power reference value P refSOC Added to the corresponding commutation chain active power reference value P ref , and obtain the final reference value P of active power of each phase commutation chain x-ref ,Right now

[0065] P x-ref =P refSOC +P ref ;

[0066] S25: Calculate the active current reference value of each phase commutation chain according to the final active power reference value of each phase commutation chain; specifically:

[0067] Calculate the final reference value P of active power of each phase commutation chain x-ref and active power measurement value P dcx The difference between the two is calculated and PI adjustment is performed to obtain the active current reference value I of each phase commutation chain in the active power control mode. x-dref , the formula is as follows:

[0068]

[0069] Where, is the PI adjustment formula, K p is the proportional coefficient, T is the integration time constant, and s is the Laplace transform constant;

[0070] S26: According to the active current reference value I of each phase commutation chain x-dref The instantaneous current of each phase commutation chain is adjusted, so that the charge state of power units between different commutation chains can be balanced by adopting phase-split instantaneous current tracking control.

[0071] In summary, for phases a, b, and c, the overall formulas are:

[0072]

[0073]

[0074]

[0075] Furthermore, based on the chain energy storage system topology structure and the balanced control method of the chain energy storage system in the above-mentioned embodiment of the present invention, the embodiment of the present invention also provides a balanced control strategy for the chain energy storage system, and each module unit of the balanced control strategy corresponds to the steps of the balanced control method in the above-mentioned embodiment. Specifically, the balanced control strategy includes an inter-commutation chain balanced control strategy and an intra-commutation chain balanced control strategy. The inter-commutation chain balanced control strategy includes a power calculation unit, a current calculation unit, and a current regulation unit. The intra-commutation chain balanced control strategy includes a reference voltage calculation unit and a reference voltage regulation unit. In addition, the state of charge difference calculation unit is a shared unit of the inter-commutation chain balanced control strategy and the intra-commutation chain balanced control strategy. The functions of each unit are as follows:

[0076] In the inter-commutation chain balancing control strategy:

[0077] a state of charge difference calculation unit, configured to calculate the difference between the average state of charge of the three-phase commutation chain and the average state of charge of each phase commutation chain, to obtain the state of charge difference of each phase commutation chain;

[0078] a power calculation unit, configured to calculate the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain to obtain a superimposed active power reference value of each phase commutation chain; and further configured to superimpose the superimposed active power reference value onto the active power reference value of the corresponding commutation chain to obtain a final active power reference value of each phase commutation chain;

[0079] a current calculation unit, configured to calculate an active current reference value of each phase commutation chain according to the final active power reference value of each phase commutation chain, specifically by calculating the difference between the final active power reference value and the active power measurement value of each phase commutation chain, and performing PI adjustment to obtain an active current reference value of each phase commutation chain in a fixed active power control mode;

[0080] The current regulating unit is used to regulate the instantaneous current of each phase commutation chain according to the active current reference value of each phase commutation chain.

[0081] In the balancing control strategy within the commutation chain:

[0082] a state of charge difference calculation unit, configured to calculate the difference between the actual state of charge value of each power module in the commutation chain and the average state of charge value of the power modules in the commutation chain, and obtain the power module state of charge difference value of each power module;

[0083] a reference voltage calculation unit, configured to calculate the product of the state-of-charge difference of each power module, the state-of-charge balancing coefficient within the commutation chain, and the commutation chain current to obtain a superimposed voltage reference wave for each power module; and further configured to superimpose the superimposed voltage reference wave onto the commutation chain voltage modulation wave output by the inner loop controller to obtain a voltage reference wave for each power module;

[0084] The reference voltage adjustment unit is used to adjust the voltage modulation wave of each power module according to the difference in the charge state of the power modules to control the charge and discharge rate of each power module; specifically, the reference voltage adjustment unit adjusts the voltage modulation wave of the corresponding power module based on the voltage reference wave calculated by the reference voltage calculation unit.

[0085] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for balancing control of a chain energy storage system, wherein each phase of a three-phase commutation chain in the chain energy storage system comprises a plurality of power modules connected in series, and each of the power modules comprises an energy storage battery; characterized in that: The balancing control method includes a method for balancing the state of charge of each power module between three-phase commutation chains, and the method for balancing the state of charge of each power module between three-phase commutation chains includes the following steps: Calculate the difference between the average state of charge of the three-phase commutation chain and the average state of charge of each phase commutation chain to obtain the state of charge difference of each phase commutation chain; Calculate the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain to obtain the superimposed active power reference value of each phase commutation chain; Superimposing the superimposed active power reference value onto the corresponding commutation chain active power reference value to obtain a final active power reference value of each phase commutation chain; According to the final reference value of active power of each phase commutation chain, the reference value of active current of each phase commutation chain is calculated, specifically: Calculate the difference between the final reference value of active power and the measured value of active power of each phase commutation chain, and perform PI adjustment to obtain the active current reference value of the active power control mode of each phase commutation chain , ， Where, is the final reference value of active power of each phase commutation chain, is the measured active power value of each phase commutation chain, is the PI adjustment formula, is the proportional coefficient, T is the integration time constant, and s is the Laplace transform constant; The instantaneous current of each phase commutation chain is regulated according to the active current reference value of each phase commutation chain.

2. The balanced control method of the chain energy storage system according to claim 1, characterized in that: After calculating the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain, the method further includes limiting the product result.

3. The balanced control method of the chain energy storage system according to claim 1, characterized in that: The balancing control method further includes a method for balancing the state of charge of each power module in each phase commutation chain. The method for balancing the state of charge of each power module in each phase commutation chain includes the following steps: Calculating the difference between the actual state of charge of each power module in the commutation chain and the average state of charge of the power modules in the commutation chain to obtain the power module state of charge difference of each power module; The voltage modulation wave of each power module is adjusted according to the difference in the state of charge of the power modules to control the charge and discharge rate of each power module.

4. The balanced control method of the chain energy storage system according to claim 3, characterized in that: In the aforementioned step of adjusting the voltage modulation wave of each power module according to the difference in the state of charge of the power modules, the following steps are included: Calculate the product of the state of charge difference of each power module, the state of charge balance coefficient in the commutation chain, and the commutation chain current to obtain the superimposed voltage reference wave of each power module; The superimposed voltage reference wave is superimposed on the commutation chain voltage modulation wave output by the inner loop controller to adjust the voltage modulation wave of each power module.

5. A balancing control strategy for a chain energy storage system, wherein each phase commutation chain in the chain energy storage system comprises a plurality of power modules connected in series, and each of the power modules comprises an energy storage battery; characterized in that: The balancing control strategy includes an inter-commutation chain balancing control strategy, and the inter-commutation chain balancing control strategy includes: a state of charge difference calculation unit, configured to calculate the difference between the average state of charge of the three-phase commutation chain and the average state of charge of each phase commutation chain, to obtain the state of charge difference of each phase commutation chain; a power calculation unit, configured to calculate the product of the state of charge difference of each phase commutation chain, the state of charge balancing coefficient between the commutation chains, and the absolute value of the active power reference value of the corresponding commutation chain to obtain a superimposed active power reference value of each phase commutation chain; and further configured to superimpose the superimposed active power reference value onto the active power reference value of the corresponding commutation chain to obtain a final active power reference value of each phase commutation chain; The current calculation unit is used to calculate the active current reference value of each phase commutation chain according to the final active power reference value of each phase commutation chain, specifically: Calculate the difference between the final reference value of active power and the measured value of active power of each phase commutation chain, and perform PI adjustment to obtain the active current reference value of the active power control mode of each phase commutation chain , ， Where, is the final reference value of active power of each phase commutation chain, is the measured active power value of each phase commutation chain, is the PI adjustment formula, is the proportional coefficient, T is the integration time constant, and s is the Laplace transform constant; The current regulating unit is used to regulate the instantaneous current of each phase commutation chain according to the active current reference value of each phase commutation chain.

6. The balanced control strategy of the chain energy storage system according to claim 5, characterized in that: The state of charge difference calculation unit is further used to calculate the difference between the actual state of charge value of each power module in the commutation chain and the average state of charge value of the power modules in the commutation chain, so as to obtain the power module state of charge difference of each power module.

7. The balanced control strategy of the chain energy storage system according to claim 6, characterized in that: The balancing control strategy also includes a balancing control strategy within the commutation chain, and the balancing control strategy within the commutation chain includes: The reference voltage adjustment unit is used to adjust the voltage modulation wave of each power module according to the difference in the state of charge of the power modules, so as to control the charge and discharge rate of each power module.

8. The balanced control strategy of the chain energy storage system according to claim 7, characterized in that: The balancing control strategy within the commutation chain also includes: The reference voltage calculation unit is used to calculate the product of the state of charge difference of each power module, the state of charge balancing coefficient in the commutation chain, and the commutation chain current to obtain the superimposed voltage reference wave of each power module; and is also used to superimpose the superimposed voltage reference wave on the commutation chain voltage modulation wave output by the inner loop controller to obtain the voltage reference wave of each power module.

9. The balanced control strategy of the chain energy storage system according to claim 8, characterized in that: When the voltage regulating unit regulates the voltage modulation wave of each power module, specifically: The voltage reference wave is used as a voltage modulation wave of a corresponding power module for adjustment.

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