Cascaded high-voltage direct-connection DC-DC battery energy storage system and parameter design method thereof

Abstract

The application discloses a cascaded high-voltage direct-hanging DC-DC battery energy storage system and a parameter design method thereof. The cascaded high-voltage direct-hanging DC-DC battery energy storage system comprises a direct-current bus and a direct-current link, and the direct-current bus and the direct-current link are connected through a direct-current reactor; the direct-current link comprises two or more cascaded H-bridge sub-modules; any one H-bridge sub-module comprises a full-bridge unit, a battery unit and a low-pass filter; and the full-bridge unit comprises an IGBT module and an anti-parallel diode. The cascaded high-voltage direct-hanging DC-DC battery energy storage system can realize low output voltage harmonics by cascading at least two H-bridge sub-modules together, thereby reducing the switching process dv / dt in the medium and high-voltage direct-current power grid energy storage converter topology and overcoming the problem of low direct-current voltage resistance in the circuit. In addition, the modular design effectively reduces the failure rate and the cost of the direct-current energy storage converter.

Description

Technical Field

[0001] This invention relates to the field of electrical engineering, specifically to a cascaded high-voltage direct-connected DC-DC battery energy storage system and its parameter design method. Background Technology

[0002] With the development of the world economy, energy shortages and environmental pollution have become increasingly prominent issues. The large-scale development and utilization of clean and renewable energy sources is an essential path to achieving sustainable human development. The vigorous development of renewable energy has brought new challenges and opportunities to power technology. On the one hand, renewable energy sources such as wind and solar power are highly intermittent and random; large-scale integration of these energy sources affects grid operation safety and power quality. On the other hand, with the development of semiconductor devices and power equipment manufacturing technologies, DC transmission and DC grid technologies based on power electronic conversion are increasingly demonstrating their advantages in power density, economy, and control flexibility. In medium- and high-voltage power transmission, DC grid technology has evolved from point-to-point DC transmission to multi-terminal DC transmission and then to interconnected networks; in medium-voltage power aggregation, DC grid technology has also received widespread attention and research. To fully realize the market potential of battery energy storage systems and their important role in energy, power, and related industries, and to adapt to the rapid development requirements of the energy sector in recent years, embedding battery energy storage systems into DC grids for power regulation, improving DC grid reliability, and providing emergency power support has promising application prospects.

[0003] However, in the energy storage converter topology of medium- and high-voltage DC power grids, there is a large dv / dt during the switching process, which results in a low DC withstand voltage capability in the circuit. Summary of the Invention

[0004] In view of the above problems, the present invention is proposed to provide a cascaded high-voltage direct-connected DC-DC battery energy storage system and its parameter design method to overcome or at least partially solve the above problems.

[0005] According to one aspect of the present invention, a cascaded high-voltage direct-connected DC-DC battery energy storage system is provided, comprising a DC bus and a DC link, wherein the DC bus and the DC link are connected via a DC reactor. The DC link includes two or more cascaded H-bridge sub-modules, each H-bridge module comprising a full-bridge unit, a battery unit, and a low-pass filter. The full-bridge unit includes an IGBT module and an anti-parallel diode. Preferably, the full-bridge unit includes four IGBT modules. The IGBT module is a modular semiconductor product packaged by bridging and packaging an IGBT (Insulated Gate Bipolar Transistor) chip and a FWD (Freewheeling Diode) chip using a specific circuit.

[0006] According to another aspect of the present invention, a parameter design method for a battery energy storage system is provided, comprising: defining the DC-side capacitor voltage of the H-bridge as V. ba With a cascade configuration of M, the number of H-bridge submodules in steady-state operation fluctuates between N and N+1, and the output voltage of the cascaded H-bridge modules ranges between 0 and V. ba Switching between these modes, the steady-state output voltage of the entire DC link is NV. ba ~(N+1)V ba Let (N+1)V ba If the duty cycle is D, then NV ba The duty cycle is 1-D;

[0007] The triangular carrier frequency is f c The equivalent switching frequency is Mf c The current ripple frequency is Mf c .

[0008] Optionally, the DC bus voltage is defined as V. g The DC bus current is i L The DC inductance is L.

[0009] When the battery energy storage system is in a charging state, and the DC link output voltage is NV... ba At that time, V g >NV ba i L Rise, duration is The circuit equation is

[0010]

[0011] When the DC link output voltage is (N+1)V ba At that time, V g <(N+1)V ba i L The descent lasted for a period of time. The circuit equation is

[0012]

[0013] Optionally, the DC bus voltage is defined as V. g The DC bus current is i L The DC inductance is L;

[0014] When the battery energy storage system is operating in steady state, i L A fixed rate of increase during the upward period From minimum to maximum value, the rate of decline is constant during the decreasing time period. From the maximum value to the minimum value, then

[0015]

[0016] get

[0017]

[0018] Optionally, with the initial setting D = 0.5 and the carrier amplitude value of 1, the corresponding modulated wave output is:

[0019] Optionally, when the battery energy storage system is operating in steady state, the DC current i L The peak value of the fluctuation is i LP ,but

[0020]

[0021] when i L When the maximum value is reached:

[0022] V g = (N + 0.5N) ba .

[0023] Optionally, let the system rated current be I. N If the current fluctuation rate does not exceed δ%, then the minimum value of inductance L is

[0024]

[0025] Optionally, the battery charging cutoff voltage is set to V. ba_T The discharge cutoff voltage is V. ba_D ,but

[0026] MV ba_D >V g .

[0027] Optionally, during steady-state operation of the battery energy storage system

[0028] NV ba <V g <(N+1)V ba And N+1≤M;

[0029] When V g and V ba Once determined, N satisfies the following conditions during steady-state operation of the battery energy storage system.

[0030]

[0031] Preferably, N is taken to be around 0.7M.

[0032] Optionally, the battery current I ba V is calculated based on power balance. g I ref =MV ba Iba ,but

[0033]

[0034] According to another aspect of the present invention, a control strategy for any of the above-mentioned systems is provided, comprising: defining SOC (State of Charge). ave The SOC is the average state of charge (SOC) of the battery cells in each H-bridge submodule of the DC link. i Let SOC be the state of charge (SOC) of the i-th battery cell. ave With SOC i The deviation is processed by the proportional regulator k and multiplied by the sign function to obtain the modulation wave adjustment value. The modulation wave adjustment value is superimposed on the first modulation wave to generate the final modulation wave. Then, the PWM (pulse width modulation) drive signal required by each H-bridge submodule is generated by the carrier phase shift modulation strategy.

[0035] According to another aspect of the present invention, an electronic device is provided, comprising: a memory and a processor;

[0036] The memory is used to store program instructions;

[0037] The processor is used to call program instructions in the memory to execute any of the above-mentioned parameter design methods or control strategies for the battery energy storage system.

[0038] According to another aspect of the present invention, a computer-readable storage medium is provided, wherein computer program instructions are stored therein, and when the computer program instructions are executed, the parameter design method or the control strategy of any of the above-described battery energy storage systems is implemented.

[0039] According to another aspect of the present invention, a computer program product is provided, comprising a computer program that, when executed by a processor, implements any of the above-described parameter design methods or control strategies for the battery energy storage system.

[0040] As described above, the technical solution of this invention provides a cascaded high-voltage direct-connected DC-DC battery energy storage system, including a DC bus and a DC link, which are connected via a DC reactor. The DC link includes two or more cascaded H-bridge sub-modules, each of which includes a full-bridge unit, a battery unit, and a low-pass filter. The full-bridge unit includes an IGBT module and anti-parallel diodes. The beneficial effect of this technical solution is that, by cascading at least two H-bridge sub-modules together, the cascaded high-voltage direct-connected DC-DC battery energy storage system can achieve lower output voltage harmonics, thereby reducing the switching process dv / dt in medium- and high-voltage DC grid energy storage converter topologies and overcoming the problem of low DC withstand voltage capability in the circuit. Furthermore, the modular design effectively reduces the failure rate and the cost of the DC energy storage converter. Attached Figure Description

[0041] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0042] Figure 1 A schematic diagram of a cascaded high-voltage direct-connected DC-DC battery energy storage system according to an embodiment of the present invention is shown;

[0043] Figure 2 A control strategy for a cascaded high-voltage direct-connected DC-DC battery energy storage system according to an embodiment of the present invention is shown. Detailed Implementation

[0044] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0045] Figure 1 A schematic diagram of a cascaded high-voltage direct-connected DC-DC battery energy storage system according to an embodiment of the present invention is shown.

[0046] like Figure 1As shown, the system includes a DC bus and a DC link, which are connected via a DC reactor. The DC link comprises two or more cascaded H-bridge submodules. Each H-bridge submodule includes a full-bridge unit, a battery unit, and a low-pass filter. The full-bridge unit includes an IGBT module and anti-parallel diodes. Preferably, the DC link is formed by cascading multiple identical H-bridge submodules. By adopting a cascaded high-voltage direct-connection structure, it has higher withstand voltage capability, adapting to various medium- and high-voltage DC grid energy storage scenarios. Embedding the battery unit in each H-bridge submodule provides good power regulation capability. Furthermore, the modular design effectively reduces the failure rate and the cost of the DC energy storage converter.

[0047] In one embodiment of the present invention, a parameter design method for a battery energy storage system is provided, including: defining the DC-side capacitor voltage of the H-bridge as V. ba With a cascade configuration of M, the number of H-bridge submodules in steady-state operation fluctuates between N and N+1, and the output voltage of the cascaded H-bridge modules ranges between 0 and V. ba Switching between these modes, the steady-state output voltage of the entire DC link is NV. ba ~(N+1)V ba Let (N+1)V ba If the duty cycle is D, then NV ba The duty cycle is 1-D; the triangular carrier frequency is f. c The equivalent switching frequency is Mf c The current ripple frequency is Mf c .

[0048] In one embodiment of the present invention, in the above method, the DC bus voltage is defined as V. g The DC bus current is i L The DC inductance is L.

[0049] When the battery energy storage system is in a charging state, and the DC link output voltage is NV... ba At that time, V g >NV ba i L Rise, duration is The circuit equation is

[0050]

[0051] When the DC link output voltage is (N+1)V ba At that time, V g <(N+1)V ba i L The descent lasted for a period of time. The circuit equation is

[0052]

[0053] In one embodiment of the present invention, in the above method, the DC bus voltage is defined as V. g The DC bus current is i L The DC inductance is L;

[0054] When the battery energy storage system is operating in steady state, i L A fixed rate of increase during the upward period From minimum to maximum value, the rate of decline is constant during the decreasing time period. From the maximum value to the minimum value, then

[0055]

[0056] get

[0057]

[0058] Furthermore, with the initial setting D = 0.5 and the carrier amplitude value of 1, the corresponding modulated wave output is:

[0059] Furthermore, when the battery energy storage system is operating in steady state, the DC current i L The peak value of the fluctuation is i Lp ,but

[0060]

[0061] when i L When the maximum value is reached:

[0062] V g = (N+0.5)V ba .

[0063] Let the rated current of the system be I. N If the current fluctuation rate does not exceed δ%, then the minimum value of inductance L is

[0064]

[0065] Furthermore, the battery charging cutoff voltage is set to V. ba_T The discharge cutoff voltage is V. ba_D ,but

[0066] MV ba_D >V g .

[0067] Furthermore, during steady-state operation of the battery energy storage system

[0068] NV ba <V g <(N+1)V baAnd N+1≤M;

[0069] When V g and V ba Once determined, N satisfies the following conditions during steady-state operation of the battery energy storage system.

[0070]

[0071] Preferably, N is taken as a value around 0.7M. N is a variable value in actual operation. When the battery energy storage system is in steady state, the battery nominal voltage is calculated to be around 0.7M. It should be noted that M and N are both integer values. The value of N should be taken to ensure that the battery can still discharge when the voltage drops due to low battery power, and at the same time ensure that it can still charge with a certain power when the voltage rises due to high battery power.

[0072] Furthermore, the battery current I ba V is calculated based on power balance. g I ref =MV ba I ba ,but

[0073]

[0074] For example, design a 2MW / 4MWh DC battery energy storage system suitable for a 10kV DC grid, with specific parameter configurations as shown in Table 1.

[0075] Table 1 MMDDC Simulation Parameters

[0076]

[0077] Figure 2 A control strategy for a cascaded high-voltage direct-connected DC-DC battery energy storage system according to an embodiment of the present invention is shown.

[0078] like Figure 2 As shown, sgn is the sign function, I ref i is the reference value for the DC link current. L The DC link current is sampled, and the deviation between the two is used by a PI regulator to generate the first modulation wave, which is the main control strategy of the energy storage system; specifically, the above control strategy includes defining the SOC. ave The SOC is the average state of charge (SOC) of the battery cells in each H-bridge submodule of the DC link. i Let SOC be the state of charge (SOC) of the i-th battery cell. ave With SOC i The deviation is processed by the proportional regulator k and multiplied by the sign function to obtain the modulation wave adjustment value. The modulation wave adjustment value is superimposed on the first modulation wave to generate the final modulation wave. Then, the PWM drive signal required by each H-bridge submodule is generated by the carrier phase shift modulation strategy.

[0079] SOC balancing strategy working principle: During the operation of an energy storage system, if the SOC of the battery cells in the system is inconsistent, when the system is in a charging state, the sign function result is 1. At this time, if the SOC... i SOC ave This reduces the modulation wave, allowing battery cells with a large SOC to have a shorter deployment time; if the SOC... i <SOC ave This increases the modulation wave, extending the activation time of battery cells with low State of Charge (SOC). When the system is in discharge mode, the modulation wave changes in the opposite direction due to the sign function, thus achieving SOC equalization. The proportional gain k, also known as the SOC equalization rate coefficient, increases the equalization speed. However, since the modulation wave itself reaches approximately 0.7 during system operation, k cannot be chosen to prevent the system from being in an over-modulated and uncontrollable state, nor can it be too small, leading to a low equalization rate. Therefore, the selection of k must be a compromise based on specific circumstances. It is evident that this control strategy is simple, and other control strategies can be modified based on it.

[0080] In one embodiment of the present invention, an electronic device is provided, including: a memory and a processor;

[0081] The memory is used to store program instructions;

[0082] The processor is used to call program instructions in the memory to execute any of the above-mentioned parameter design methods or control strategies for the battery energy storage system.

[0083] In one embodiment of the present invention, a computer-readable storage medium is provided, wherein computer program instructions are stored in the computer-readable storage medium, and when the computer program instructions are executed, the parameter design method or the control strategy of any of the above-described battery energy storage systems is implemented.

[0084] In one embodiment of the present invention, a computer program product is provided, including a computer program that, when executed by a processor, implements any of the above-described parameter design methods or control strategies for the battery energy storage system.

[0085] It should be noted that:

[0086] The algorithms and displays provided herein are not inherently related to any particular computer, virtual device, or other equipment. Various general-purpose devices can also be used in conjunction with the teachings herein. The required structure for constructing such devices is apparent from the above description. Furthermore, this invention is not directed to any particular programming language. It should be understood that the contents of the invention described herein can be implemented using various programming languages, and the above description of specific languages ​​is for the purpose of disclosing the best mode of implementation of the invention.

[0087] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0088] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim itself is a separate embodiment of the invention.

[0089] Those skilled in the art will understand that modules in the device of the embodiments can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiments can be combined into a single module, unit, or component, and further, they can be divided into multiple H-bridge sub-modules, sub-units, or sub-components. Except where at least some of such features and / or processes or units are mutually exclusive, any combination of all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or units of any method or device so disclosed can be employed. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0090] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0091] The various component embodiments of the present invention can be implemented in hardware, or as software modules running on one or more processors, or a combination thereof. Those skilled in the art will understand that microprocessors or digital signal processors (DSPs) can be used in practice to implement some or all of the functions of some or all of the components in the cascaded high-voltage direct-connected DC-DC battery energy storage system according to embodiments of the present invention. The present invention can also be implemented as a device or apparatus program (e.g., a computer program and computer program product) for performing part or all of the methods described herein. Such programs implementing the present invention can be stored on a computer-readable medium or can be in the form of one or more signals. Such signals can be downloaded from an Internet website, provided on a carrier signal, or provided in any other form.

[0092] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A parameter design method for a cascaded high-voltage direct-connected DC-DC battery energy storage system, characterized in that, The cascaded high-voltage direct-connected DC-DC battery energy storage system includes a DC bus and a DC link, and the DC bus and the DC link are connected by a DC inductor. The DC link includes two or more cascaded H-bridge sub-modules. Any H-bridge module includes a full-bridge unit, a battery unit, and a low-pass filter. The full-bridge unit includes an IGBT module and an anti-parallel diode. The method includes: defining the DC-side capacitor voltage of the H-bridge as V. ba Configure the number of cascaded nodes to be M. During steady-state operation, the number of H-bridge submodules connected fluctuates between N and N+1, and the output voltage of the cascaded H-bridge submodules ranges between 0 and V. ba Switching between these modes, the steady-state output voltage of the entire DC link is NV. ba ~(N+1)V ba Let (N+1)V ba If the duty cycle is D, then NV ba The duty cycle is 1-D; The triangular carrier frequency is f c The equivalent switching frequency is Mf c The current ripple frequency is Mf c ; Define the DC bus voltage as V g The DC bus current is i L The DC inductance is L; When the battery energy storage system is operating in steady state, i L A fixed rate of increase during the upward period From minimum to maximum value, the rate of decline is constant during the decreasing time period. From the maximum value to the minimum value, then ， get 。 2. The parameter design method according to claim 1, characterized in that: Define the DC bus voltage as V g The DC bus current is i L The DC inductance is L. When the battery energy storage system is in a charging state, and the DC link output voltage is NV... ba At that time, V g >NV ba i L Rise, duration is The circuit equation is ； When the DC link output voltage is (N+1)V ba At that time, V g <(N+1)V ba i L The descent lasted for a period of time. The circuit equation is 。 3. The parameter design method according to claim 1, characterized in that: With the initial setting D=0.5 and the carrier amplitude value of 1, the corresponding modulated wave output is: .

4. The parameter design method according to claim 1, characterized in that: When the battery energy storage system is operating in steady state, the DC bus current i L The peak value of the fluctuation is ,but ； when i L When the maximum value is reached: 。 5. The parameter design method according to claim 4, characterized in that: Let the rated current of the system be I. N Current fluctuation rate does not exceed Then the minimum value of DC inductance L is 。 6. The parameter design method according to claim 1, characterized in that: Set the discharge cutoff voltage to V ba_D ,but 。 7. The parameter design method according to claim 1, characterized in that: When the battery energy storage system is in steady state operation And N+1≤M; When V g and V ba Once determined, N satisfies the following conditions during steady-state operation of the battery energy storage system. 。 8. The parameter design method according to claim 7, characterized in that: N is set to 0.7M.

9. The parameter design method according to claim 1, characterized in that: Battery current I ba Based on power balance calculations ,but ， Among them, I ref This is a reference value for the DC link current.

10. The parameter design method according to claim 1, characterized in that: The full-bridge unit includes four IGBT modules.

11. The parameter design method according to any one of claims 1 or 10, characterized in that, include: Define SOC ave The SOC is the average state of charge (SOC) of the battery cells in each H-bridge submodule of the DC link. i Let SOC be the state of charge (SOC) of the i-th battery cell. ave With SOC i The deviation is processed by the proportional regulator k and multiplied by the sign function to obtain the modulation wave adjustment value. The modulation wave adjustment value is superimposed on the first modulation wave to generate the final modulation wave. Then, the PWM drive signal required by each H-bridge submodule is generated by the carrier phase shift modulation strategy. The first modulated wave is derived from the DC link current reference value I. ref With DC bus current i L The deviation between them is generated by the PI controller.

12. An electronic device, characterized in that, include: Memory and processor; The memory is used to store program instructions; The processor is used to invoke program instructions in the memory to execute the parameter design method as described in any one of claims 1-11.

13. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions, which, when executed, implement the parameter design method according to any one of claims 1-11.

14. A computer program product, comprising a computer program, characterized in that: When the computer program is executed by a processor, it implements the parameter design method as described in any one of claims 1-11.

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