High-voltage cascade energy storage system based on nested power module and control method thereof

Abstract

The invention relates to the technical field of high-voltage cascade energy storage systems, and discloses a high-voltage cascade energy storage system based on nested power modules and a control method thereof.The high-voltage cascade energy storage system comprises three phases of chain type energy storage bridge arms connected with three phase lines of a power grid respectively, and each phase of chain type energy storage bridge arm comprises a plurality of cascaded nested power modules; each nested power module comprises a plurality of direct-current chain type energy storage units and an H-bridge circuit, the plurality of direct-current chain type energy storage units are connected in parallel and then are connected with the direct-current side of the H-bridge circuit, and the alternating-current side of the H-bridge circuit is connected with an alternating-current switch; the direct current chain type energy storage unit comprises a plurality of energy storage modules, an electric reactor and a direct current switch, the plurality of energy storage modules are cascaded and then are sequentially connected with the electric reactor and the direct current switch, each energy storage module comprises a battery pack and a half-bridge circuit connected with the battery pack, and the half-bridge circuit is used for charge state balance control of the battery pack. According to the invention, any battery pack can be bypassed after a fault, and the operation reliability of the high-voltage cascade energy storage system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage cascade energy storage systems, and in particular to a high-voltage cascade energy storage system based on a nested power module and a control method thereof. Background Art

[0002] High-voltage cascade energy storage system is an advanced energy storage technology widely used in power systems to improve the stability and reliability of the power grid. This system connects multiple battery modules or energy storage units in series to form an overall system with high voltage output.

[0003] Traditional large-capacity energy storage power stations generally operate multiple energy storage PCSs in parallel on the low-voltage AC side, and step up the voltage step by step through a step-up transformer before connecting to the medium- and high-voltage power grid. However, too many energy storage PCSs in parallel will lead to various stability problems and problems of uneven circulation and power distribution. At the same time, the battery energy storage system described in this scheme occupies a large area, has a complex control system, difficult coordinated control, large transformer losses, and low system efficiency. On top of this, the high-voltage cascade energy storage system based on the cascaded H-bridge converter easily realizes various high-voltage cascades and capacity expansions by introducing dispersed battery modules on the DC side of each phase H-bridge. At the same time, this solution reduces the battery circulation and eliminates the industrial frequency transformer, thereby achieving the high efficiency, high reliability, large capacity and safety requirements of battery energy storage power conversion. However, the existing high-voltage cascade energy storage system also has various problems, which are analyzed as follows:

[0004] 1) As described in Chinese patent CN215267793U, the integrated high-voltage cascade energy storage system includes cascaded PCS power units, which are based on a single battery pack connected in parallel with an H-bridge and then cascaded, and an LC filter is connected between the battery pack and the H-bridge to suppress the 2x frequency ripple current of the battery pack. At the same time, the H-bridge port uses a mechanical switch in parallel for the PCS power unit bypass design; this technology cannot achieve refined balancing management of the battery pack, and at the same time, when a single battery pack fails, the entire PCS power unit needs to exit, and the system reliability is low;

[0005] 2) A module fault bypass control method and device for a high-voltage cascade energy storage system as described in Chinese patent CN115513935A, wherein the cascade power module internally includes a soft start unit, an H-bridge and a port bypass semiconductor device (V1); this technology cannot achieve refined management of the battery pack and has the problem of low reliability;

[0006] 3) A high-voltage cascade energy storage device as described in Chinese patent CN111049273A, wherein the high-voltage cascade scheme is: the H-bridge and the battery pack are connected in parallel and then cascaded to form a high-voltage energy storage system; when any battery pack fails, the technical solution does not have the battery pack failure exit (or bypass) function, and the reliability of the high-voltage cascade energy storage system is low.

[0007] In summary, how to achieve balanced control of a high-voltage cascade energy storage system and improve the operational reliability of the high-voltage cascade energy storage system has become a technical problem that urgently needs to be solved in this field. Summary of the invention

[0008] The purpose of the present invention is to provide a high-voltage cascade energy storage system based on nested power modules and a control method thereof, which realizes balanced control of the charge state of the battery pack through the embedded power module, and can bypass any battery pack after a failure, avoiding shutdown caused by local failure, greatly reducing the failure rate of the high-voltage cascade energy storage system, thereby improving the operational reliability of the high-voltage cascade energy storage system.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] A high-voltage cascade energy storage system based on a nested power module, comprising a three-phase chain energy storage bridge arm respectively connected to the three-phase lines of a power grid, each phase chain energy storage bridge arm comprising a plurality of cascaded nested power modules, each nested power module comprising a plurality of DC chain energy storage units and an H-bridge circuit, a plurality of DC chain energy storage units being connected in parallel to the DC side of the H-bridge circuit, and an AC side of the H-bridge circuit being connected to an AC switch;

[0011] The DC chain energy storage unit includes multiple energy storage modules, a DC reactor, and a DC switch. The multiple energy storage modules are cascaded and connected to the DC reactor and the DC switch in sequence. The energy storage module includes a battery pack and a half-bridge circuit connected to the battery pack. The half-bridge circuit is used for charge state balancing control of the battery pack.

[0012] Furthermore, the half-bridge circuit includes two fully-controlled semiconductor devices, which are connected in series, and a half-bridge midpoint is formed between the two fully-controlled semiconductor devices.

[0013] Furthermore, in each of the DC chain energy storage units, the midpoint of the half bridge of the first energy storage module is connected to the DC reactor and the DC switch in sequence, the DC switch is connected to the DC positive terminal (DC+), the negative pole of the first energy storage module is connected to the midpoint of the half bridge of the second energy storage module, the negative pole of the second energy storage module is connected to the midpoint of the half bridge of the third energy storage module, and so on, the negative pole of the last energy storage module is connected to the DC negative terminal (DC-), and the DC positive terminal (DC+) and the DC negative terminal (DC-) are respectively connected to the DC side of the H-bridge circuit.

[0014] Furthermore, the two fully-controlled semiconductor devices are respectively a fully-controlled semiconductor device Q1 and a fully-controlled semiconductor device Q2. Both the fully-controlled semiconductor device Q1 and the fully-controlled semiconductor device Q2 use MOSFET. The D pole (drain) of the fully-controlled semiconductor device Q1 is connected to the positive pole of the battery pack, and the S pole (source) of the fully-controlled semiconductor device Q2 is connected to the negative pole of the battery pack.

[0015] Furthermore, a capacitor C0 is connected in parallel at both ends of the battery pack, and the capacitor C0 is located between the battery pack and the half-bridge circuit.

[0016] Furthermore, the H-bridge circuit includes four power semiconductor switch components, and every two power semiconductor switch components are connected in series in the same direction to form a bridge arm, the two bridge arms are connected in parallel, and the midpoints of the two bridge arms are respectively connected to the AC positive end and the AC negative end, and the AC switch is connected in parallel between the AC positive end and the AC negative end; each power semiconductor switch component includes a fully controlled semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel.

[0017] Furthermore, the four fully-controlled semiconductor devices all use IGBTs, and the four unidirectional uncontrollable semiconductor devices all use diodes.

[0018] Furthermore, after a number of DC link type energy storage units are connected in parallel, a capacitor C1 is also connected in parallel, and the capacitor C1 is located between the number of DC link type energy storage units connected in parallel and the H-bridge circuit.

[0019] Furthermore, the AC positive end of the three-phase chain energy storage bridge arm is connected to the three-phase line of the power grid through the bridge arm inductor L, the bridge arm equivalent resistor R, and the grid-side inductor Ls in sequence, and the AC negative end of the three-phase chain energy storage bridge arm is connected to the common point N.

[0020] The present invention also provides a control method for a high-voltage cascade energy storage system based on a nested power module, which is applied to the above-mentioned high-voltage cascade energy storage system based on a nested power module. The control method includes the following fault removal modes:

[0021] When a battery pack fails, the battery pack is short-circuited through the half-bridge circuit corresponding to the battery pack, and other battery packs in the DC chain energy storage unit operate normally;

[0022] When a DC chain energy storage unit fails, the DC switch of the DC chain energy storage unit is opened to cut out the DC chain energy storage unit, and other DC chain energy storage units in the nested power module operate normally;

[0023] When a certain nested power module fails, the AC switch in the nested power module is closed to short-circuit the nested power module, and other nested power modules in each phase chain energy storage bridge arm operate normally.

[0024] In summary, the present invention provides a cost-effective high-voltage cascade energy storage system based on nested power modules and a control method thereof. Each phase chain energy storage bridge arm includes multiple cascaded nested power modules, and each nested power module includes several DC chain energy storage units and H-bridge circuits. The DC chain energy storage unit includes multiple energy storage modules, DC inductors, and DC switches. The energy storage module includes a battery pack and a half-bridge circuit connected to the battery pack. The nested power module described in the present invention includes multiple half-bridge circuits and an H-bridge circuit, each half-bridge circuit is connected to a battery pack, and each half-bridge circuit can be used to realize battery charging and discharging power and charge control by controlling the on or off time of a fully controlled semiconductor device; a group of DC chain energy storage units are obtained by connecting the multiple half-bridge circuits, DC reactors, and DC switches of the nested power module in series, and each group of DC chain energy storage units can realize internal charge state balance control; the nested power module may include multiple groups of parallel DC chain energy storage units and H-bridge circuits, and multiple groups of DC chain energy storage units can realize charge state balance control by controlling the on or off time of the power semiconductor switch components in the H-bridge circuit.

[0025] The nested power module provided by the present invention not only has the above battery pack charge state balance control effect, but also has the following advantages:

[0026] 1) The half-bridge circuit can bypass any battery pack if it fails, which will not cause the DC chain energy storage unit to fail and shut down;

[0027] 2) If a battery pack failure occurs in any DC chain energy storage unit, it will exit independently without causing other DC chain energy storage units to fail and shut down;

[0028] 3) If a fault occurs in any nested power module, it will exit independently without causing the high-voltage cascade energy storage system to fail and shut down;

[0029] The above measures reduce the failure rate of the high-voltage cascade energy storage system, thereby improving the operational reliability of the high-voltage cascade energy storage system.

[0030] In addition, in the present invention, multiple DC chain energy storage units are easily connected in parallel, and multiple nested power modules are easily cascaded, so it is easy to expand the capacity and boost the voltage of the high-voltage energy storage system. The balanced control and protection measures greatly improve the operating reliability of the high-voltage cascade energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. 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 paying creative labor.

[0032] Figure 1 The hardware topology diagram of the high-voltage cascade energy storage system based on the nested power module of the present invention;

[0033] Figure 2 This is a hardware topology diagram of a nested power module according to Embodiment 1 of the present invention;

[0034] Figure 3 This is a hardware topology diagram of a nested power module according to Embodiment 2 of the present invention;

[0035] Figure 4 A hardware topology diagram of a plurality of parallel DC chain energy storage units of the present invention;

[0036] Figure 5 The hardware topology diagram of the energy storage module of the present invention;

[0037] Description of reference numerals: T1, T2, T3, T4—fully controlled semiconductor device IGBT; Q1, Q2—fully controlled semiconductor device MOSFET; D1, D2, D3, D4—unidirectional uncontrollable semiconductor device (diode);

[0038] 1. Phase-chain energy storage bridge arm; 2. Nested power module; 3. DC chain energy storage unit. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 creative work are within the scope of protection of the present invention.

[0040] The purpose of the present invention is to provide a high-voltage cascade energy storage system based on a nested power module and a control method thereof. The embedded power module can realize balanced control of battery pack current, power and battery pack charge state. The embedded power module has the function of bypassing or exiting after any battery pack fails. The high-voltage cascade energy storage system will not shut down due to failure, which greatly reduces the failure rate of the high-voltage cascade energy storage system and improves the reliability of the high-voltage cascade energy storage system.

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] like Figure 1-Figure 5 As shown, the high-voltage cascade energy storage system based on the nested power module provided by the present invention includes: a three-phase chain energy storage bridge arm (A, B, C three-phase) respectively connected to the three-phase lines of the power grid, each phase chain energy storage bridge arm 1 includes a plurality of cascaded nested power modules 2, each nested power module 2 includes a plurality of DC chain energy storage units 3 and an H-bridge circuit, a plurality of DC chain energy storage units 3 are connected in parallel to the DC side of the H-bridge circuit, and the AC side of the H-bridge circuit is connected to an AC switch; Figure 2 The nested power module 2 in Example 1 includes a DC link energy storage unit 3 and an H-bridge circuit; Figure 3 The nested power module 2 in Embodiment 2 includes a plurality of DC link energy storage units 3 and an H-bridge circuit.

[0043] like Figure 2 As shown, taking a DC chain energy storage unit 3 as an example, the DC chain energy storage unit 3 includes multiple energy storage modules, a DC reactor L1, and a DC switch K1. The multiple energy storage modules are cascaded and connected to the DC reactor L1 and the DC switch K1 in sequence. The energy storage module includes a battery pack (such as Figure 2 BAT11, BAT12, ... BAT1n) and a half-bridge circuit connected to the battery pack, the half-bridge circuit is used for charge state balance control of the battery pack. The battery pack of the present invention includes a plurality of battery cells connected in series.

[0044] The half-bridge circuit can be controlled by a battery management system (BMS). The battery management system (BMS) can collect the voltage and current of the battery cells to control the on and off of the half-bridge circuit, so as to identify the consistency of the charge state of the corresponding battery pack and realize the charge state balance control of the battery pack. The control principle of the battery management system can be referred to the conventional technology in the field, which will not be elaborated here.

[0045] Specifically, the half-bridge circuit includes two fully-controlled semiconductor devices, which are connected in series, and a half-bridge midpoint is formed between the two fully-controlled semiconductor devices.

[0046] The fully controlled semiconductor device may be a MOSFET (power field effect transistor), an IGBT (insulated-gate bipolar transistor), a triode, a GTO (gate turn-off thyristor), or the like.

[0047] In each of the DC chain energy storage units 3, the midpoint of the half bridge of the first energy storage module is connected to the DC reactor and the DC switch in sequence, the DC switch is connected to the DC positive terminal (DC+), the negative pole of the first energy storage module is connected to the midpoint of the half bridge of the second energy storage module, the negative pole of the second energy storage module is connected to the midpoint of the half bridge of the third energy storage module, and so on, the negative pole of the last energy storage module is connected to the DC negative terminal (DC-), and the DC positive terminal (DC+) and the DC negative terminal (DC-) are respectively connected to the DC side of the H-bridge circuit. The above constitutes a complete DC chain energy storage unit.

[0048] Preferably, if Figure 5 As shown, the two fully-controlled semiconductor devices are the fully-controlled semiconductor device Q1 and the fully-controlled semiconductor device Q2. Both the fully-controlled semiconductor device Q1 and the fully-controlled semiconductor device Q2 use MOSFET. The D pole (drain) of the fully-controlled semiconductor device Q1 is connected to the positive pole of the battery pack, and the S pole (source) of the fully-controlled semiconductor device Q2 is connected to the negative pole of the battery pack.

[0049] The half-bridge circuit is connected in parallel with the battery pack. The half-bridge circuit can effectively adjust the charge and discharge current and power of the battery pack by controlling the on / off state and on-time of the fully-controlled semiconductor devices Q1 and Q2, thereby achieving balanced control of the state of charge in the battery pack.

[0050] The half-bridge circuit has an electronic bypass function and can quickly (about 1uS) bypass or exit the battery pack.

[0051] When any battery pack fails, the fully controlled semiconductor device Q2 of the corresponding half-bridge circuit can be controlled to be normally on, bypassing the battery pack without affecting the normal operation of other battery packs in the DC chain energy storage unit, thereby improving the reliability of the high-voltage cascade energy storage system.

[0052] A capacitor C0 is also connected in parallel to both ends of the battery pack, and the capacitor C0 is located between the battery pack and the half-bridge circuit.

[0053] Figure 2 In the example of the first DC chain energy storage unit, multiple energy storage modules are cascaded and connected to the DC reactor L1 and the DC switch K1 to form a DC chain energy storage unit. By controlling the charge and discharge current and time of the battery pack, the charge state balance control of the battery pack inside the DC chain energy storage unit is achieved.

[0054] Multiple DC chain energy storage units are connected in parallel. The half-bridge circuit and DC reactor are used to control the charge and discharge current and time of the battery pack, and the charge state of the battery packs in multiple groups of DC chain energy storage units is balanced. The DC switch of the DC chain energy storage unit is used to switch the DC chain energy storage unit in and out.

[0055] When the number of faulty battery packs in a single group of DC chain energy storage units is greater than a certain value, the faulty DC chain energy storage unit can be removed (or isolated) by disconnecting the DC switch of the DC chain energy storage unit without affecting the normal operation of other DC chain energy storage units, thereby improving the reliability of the high-voltage cascade energy storage system.

[0056] The nested power module includes three output voltage levels: V-, 0, and V+, which can effectively adjust the output voltage and realize voltage balancing control of a single battery pack. The corresponding logical relationship between the on-off control of the switch device of the H-bridge circuit and the output voltage is as follows:

[0057] The fully controlled semiconductor devices T1 and T4 are turned on, and the output voltage is V+;

[0058] The fully controlled semiconductor devices T1 and T3 are turned on, and the output voltage is 0;

[0059] The fully controlled semiconductor devices T2 and T3 are turned on, and the output voltage is V-;

[0060] The fully controlled semiconductor devices T2 and T4 are turned on and the output voltage is 0.

[0061] Specifically, the H-bridge circuit includes four power semiconductor switch components, and every two power semiconductor switch components are connected in series in the same direction to form a bridge arm. The two bridge arms are connected in parallel, and the midpoints of the two bridge arms are respectively connected to the AC positive terminal (M+) and the AC negative terminal (M-), and the AC switch is connected in parallel between the AC positive terminal and the AC negative terminal; each power semiconductor switch component includes a fully controlled semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel.

[0062] The H-bridge circuit can achieve more refined control and realize bidirectional power flow. It can absorb energy from the power grid to charge the battery, discharge the battery to release energy to the power grid, and provide reactive power compensation for the power grid. The nested power module is cut in and out through the AC switch of the nested power module.

[0063] When multiple battery packs of the nested power modules fail, the AC switch K1n can be closed through the nested power modules to effectively bypass the nested power modules. The nested power modules exit the high-voltage cascade energy storage system without affecting the normal operation of the high-voltage cascade energy storage system, thereby improving the reliability of the high-voltage cascade energy storage system.

[0064] Preferably, the four fully-controlled semiconductor devices T1 , T2 , T3 , and T4 are all IGBTs, and the four unidirectional uncontrollable semiconductor devices D1 , D2 , D3 , and D4 are all diodes.

[0065] By controlling the on and off timing and on time of the fully controlled semiconductor devices T1, T2, T3, and T4 of the H-bridge circuit, the charge and discharge currents of multiple groups of DC chain energy storage units of the nested power module can be effectively adjusted.

[0066] After a number of DC link type energy storage units are connected in parallel, a capacitor C1 is also connected in parallel. The capacitor C1 is located between the number of DC link type energy storage units connected in parallel and the H-bridge circuit.

[0067] The fully controlled semiconductor devices T1 and T2, T3 and T4 are connected in series to form two sets of half-bridge circuits. The C poles (collectors) of T1 and T3 are connected to the DC positive terminal (DC+), and the E poles (emitters) of T2 and T4 are connected to the DC negative terminal (DC-). The above circuit connection forms a complete H-bridge circuit. The capacitor C1 is connected in parallel to the DC positive terminal (DC+) and the DC negative terminal (DC-). The midpoints M+ and M- of the two sets of half-bridge circuits are respectively led out. The above DC chain energy storage unit and H-bridge circuit are collectively referred to as nested power modules.

[0068] In addition, the AC positive end of the three-phase chain energy storage bridge arm is connected to the three-phase line of the power grid through the bridge arm reactor L, the bridge arm equivalent resistor R, and the grid-side reactor Ls in sequence, and the AC negative end of the three-phase chain energy storage bridge arm is connected to the common point N.

[0069] The working process of the high-voltage cascade energy storage system based on nested power modules is as follows:

[0070] 1. Battery charging process:

[0071] In a set of DC chain energy storage units, the phase current of the high-voltage cascade energy storage system flows into the M+ of the embedded power module, and completes the charging of the DC side (flowing out from M-) through the unidirectional uncontrollable semiconductor device D1 and the unidirectional uncontrollable semiconductor device D4. When K1 is closed, the positive end of the DC side (DC+) charges the battery pack through the DC switch K1, the DC inductor L1 and the fully controlled semiconductor device Q1 of each half-bridge circuit, and finally the charging current flows into the negative end of the DC side (DC-).

[0072] When there are multiple groups of DC chain energy storage units, the first group of DC chain energy storage units is charged, the DC switch K2 of the second group of DC chain energy storage units is closed, and the DC positive terminal (DC+) charges the battery pack through K2, L2 and the fully controlled semiconductor device Q1 of the second group of DC chain energy storage units, and finally the charging current flows into the DC negative terminal (DC-). Until the DC switch Kn of the nth group of DC chain energy storage units is closed, the DC positive terminal (DC+) charges the battery pack through Kn, Ln and the fully controlled semiconductor device Q1 of the half-bridge circuit of the nth group of DC chain energy storage units, and finally the charging current flows into the DC negative terminal (DC-).

[0073] The phase current of the high-voltage cascade energy storage system can also flow in from the M- of the embedded power module, and complete the charging of the DC side (flowing out from M+) through the unidirectional uncontrollable semiconductor device D3 and the unidirectional uncontrollable semiconductor device D2. K1 is closed, and the positive end of the DC side (DC+) charges the battery pack through K1, L1 and the fully controlled semiconductor device Q1 of each half-bridge circuit. Finally, the charging current flows into the negative end of the DC side (DC-).

[0074] Similarly, in this case, when there are multiple groups of DC chain energy storage units, the first group of DC chain energy storage units is charged, the DC switch K2 of the second group of DC chain energy storage units is closed, and the DC positive terminal (DC+) charges the battery pack through K2, L2 and the fully controlled semiconductor device Q1 of the second group of DC chain energy storage units, and finally the charging current flows into the DC negative terminal (DC-). Until the DC switch Kn of the nth group of DC chain energy storage units is closed, the DC positive terminal (DC+) charges the battery pack through Kn, Ln and the fully controlled semiconductor device Q1 of the nth group of DC chain energy storage units, and finally the charging current flows into the DC negative terminal (DC-).

[0075] In the above process, the fully controlled semiconductor device Q1 operates in a normally on mode or a pulse width modulation (PWM) mode to accurately control the charge and discharge current of the battery pack, thereby achieving balanced control of the state of charge in the battery pack.

[0076] 2. Battery pack discharge process:

[0077] In a set of DC chain energy storage units, the battery packs inside the embedded power module are connected in series through the fully-controlled semiconductor device Q1. The first battery pack passes through the corresponding fully-controlled semiconductor device Q1, connects the inductor L1 and the DC switch K1 (closed state), until it is connected to the positive terminal (DC+) of the DC side, and finally realizes AC output through the H bridge to realize the discharge of the energy storage system.

[0078] When there are multiple groups of DC chain energy storage units, the batteries of the first group of DC chain energy storage units pass through the fully controlled semiconductor device Q1, connected to the DC reactor L1 and the DC switch K1 (closed state), until they are connected to the DC side positive terminal (DC+), the batteries of the second group of DC chain energy storage units pass through the fully controlled semiconductor device Q1, connected to the reactor L2 and the DC switch K2 (closed state), until the batteries of the nth group of DC chain energy storage units pass through the fully controlled semiconductor device Q1, connected to the reactor Ln and the DC switch Kn (closed state), until they are connected to the DC side positive terminal (DC+), and finally the AC output (discharge) is realized through the H bridge.

[0079] In the above process, Q1 works in the normal mode or pulse width modulation (PWM) mode to accurately control the charge and discharge current of the battery pack, thereby achieving balanced control of the state of charge in the battery pack. T1, T2, T3, and T4 inside the H-bridge work in pulse width modulation (PWM) mode to achieve AC output and power regulation.

[0080] 3. Bypass or exit process after battery pack failure:

[0081] If the battery pack of the high-voltage cascade energy storage system fails, such as overcharge, over-discharge, overtemperature, overvoltage, undervoltage, etc., the half-bridge circuit of the nested power module can be used to exit or bypass the faulty battery pack. When the battery pack of the nested power module fails, the control system (such as the BMS system) can quickly capture the fault signal, turn off the fully controlled semiconductor device Q1, and turn on the fully controlled semiconductor device Q2. Kick the battery pack out of the group of DC chain energy storage units without affecting the normal operation of the DC chain energy storage units. This process takes microseconds, and the nested power module will not shut down due to failure.

[0082] If a single DC chain energy storage unit has a large number of faulty battery packs, the fault of the single DC chain energy storage unit can be isolated by disconnecting the DC switch without affecting the normal operation of other DC chain energy storage units.

[0083] At the same time, the nested power module port is connected in parallel with an AC switch. If there are a large number of faulty battery packs, the high-voltage cascade energy storage system can remove the faulty module after the AC switch is closed, which does not affect the normal operation of the entire energy storage system, greatly reducing the failure rate of the high-voltage cascade energy storage system, thereby improving the reliability of the high-voltage cascade energy storage system.

[0084] The present invention also provides a control method for a high-voltage cascade energy storage system based on a nested power module, which is applied to the above-mentioned high-voltage cascade energy storage system based on a nested power module. The control method includes the following fault removal modes:

[0085] When a battery pack fails, the battery pack is short-circuited through the half-bridge circuit corresponding to the battery pack, and other battery packs in the DC chain energy storage unit operate normally;

[0086] When a DC chain energy storage unit fails, the DC switch of the DC chain energy storage unit is opened to cut out the DC chain energy storage unit, and other DC chain energy storage units in the nested power module operate normally;

[0087] When a certain nested power module fails, the AC switch in the nested power module is closed to short-circuit the nested power module, and other nested power modules in each phase chain energy storage bridge arm operate normally.

[0088] In summary, the present invention discloses a topological structure of a high-voltage cascade energy storage system based on nested power modules, including fully nested power modules, bridge arm reactors L, bridge arm equivalent resistances R, grid-side reactors Ls and power grids. The nested power modules of each phase in this high-voltage cascade energy storage system are connected in series in this manner, the M-end of the bottom nested power module is connected to the M-ends of the bottom nested power modules of the other two phases, and is connected to the power grid N, and the M+ of the bottom nested power module is connected in series with the M-end of the adjacent nested power modules of the same phase. According to such a connection method, multiple nested power modules are connected in sequence, and the M+ end of the last nested power module is connected in series with each reactor and then connected to the power grid A phase. The connection method of the power grid phase B and phase C is consistent with that of phase A, which will not be repeated here.

[0089] The present invention is based on a high-voltage cascade energy storage system of nested power modules. The nested power modules of the described high-voltage cascade energy storage system can accurately control the charge and discharge current of the battery pack and realize the balanced control of the charge state of the battery pack in the energy storage module. The nested power module semiconductor series design provided by the present invention, each submodule can be connected in parallel with two battery packs, the nested power module has the ability to bypass or exit after any one or two groups of battery packs fail, the high-voltage cascade energy storage system will not fail and shut down, greatly reducing the failure rate of the high-voltage cascade energy storage system, thereby improving the operational reliability of the high-voltage cascade energy storage system.

[0090] The present invention can solve the problems of low reliability and difficulty in expansion of existing high-voltage cascade energy storage systems by introducing fully controlled semiconductors and switch devices. The fully controlled semiconductor device Q2, DC switch and AC switch in the half-bridge circuit of the nested power module described in the present invention have the ability to bypass or exit the high-voltage cascade energy storage system in the event of a battery pack failure, which does not affect the normal operation of the high-voltage cascade energy storage system at all, and the fully controlled / half-controlled semiconductors and switch devices used are commonly used and conventional devices, with high economic advantages.

[0091] The design of independently setting a reactor and a DC switching device for each DC chain energy storage unit of the high-voltage cascade energy storage system described in the present invention makes it easy to realize multiple groups of parallel connection of DC chain energy storage units, and conveniently realize the power expansion and capacity expansion of the energy storage system while isolating the faulty battery pack, thereby improving the operational reliability of the high-voltage cascade energy storage system.

[0092] The nested power module described in the present invention can easily realize voltage boosting of a high-voltage energy storage system, expand the application scenarios of the high-voltage cascade energy storage system, and greatly improve the operational reliability of the high-voltage cascade energy storage system.

[0093] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A high-voltage cascade energy storage system based on a nested power module, comprising a three-phase chain energy storage bridge arm respectively connected to the three-phase lines of a power grid, characterized in that: Each phase chain energy storage bridge arm includes a plurality of cascaded nested power modules, each nested power module includes a plurality of DC chain energy storage units and an H-bridge circuit, a plurality of DC chain energy storage units are connected in parallel to the DC side of the H-bridge circuit, and the AC side of the H-bridge circuit is connected to an AC switch; The DC chain energy storage unit includes multiple energy storage modules, a DC reactor, and a DC switch. The multiple energy storage modules are cascaded and connected to the DC reactor and the DC switch in sequence. The energy storage module includes a battery pack and a half-bridge circuit connected to the battery pack. The half-bridge circuit is used for charge state balancing control of the battery pack.

2. The high-voltage cascade energy storage system based on nested power modules according to claim 1, characterized in that: The half-bridge circuit comprises two fully-controlled semiconductor devices, which are connected in series, and a half-bridge midpoint is formed between the two fully-controlled semiconductor devices.

3. The high-voltage cascade energy storage system based on nested power modules according to claim 2, characterized in that: In each of the DC chain energy storage units, the midpoint of the half bridge of the first energy storage module is connected to the DC reactor and the DC switch in sequence, the DC switch is connected to the DC positive terminal, the negative pole of the first energy storage module is connected to the midpoint of the half bridge of the second energy storage module, the negative pole of the second energy storage module is connected to the midpoint of the half bridge of the third energy storage module, and so on, the negative pole of the last energy storage module is connected to the DC negative terminal, and the DC positive terminal and the DC negative terminal are respectively connected to the DC side of the H-bridge circuit.

4. The high-voltage cascade energy storage system based on nested power modules according to claim 2, characterized in that: The two fully-controlled semiconductor devices are the fully-controlled semiconductor device Q1 and the fully-controlled semiconductor device Q2. Both the fully-controlled semiconductor device Q1 and the fully-controlled semiconductor device Q2 use MOSFET. The drain of the fully-controlled semiconductor device Q1 is connected to the positive electrode of the battery pack, and the source of the fully-controlled semiconductor device Q2 is connected to the negative electrode of the battery pack.

5. The high-voltage cascade energy storage system based on nested power modules according to claim 1, characterized in that: A capacitor C0 is also connected in parallel to both ends of the battery pack, and the capacitor C0 is located between the battery pack and the half-bridge circuit.

6. The high-voltage cascade energy storage system based on nested power modules according to claim 1, characterized in that: The H-bridge circuit includes four power semiconductor switch components, each two power semiconductor switch components are connected in series in the same direction to form a bridge arm, the two bridge arms are connected in parallel, and the midpoints of the two bridge arms are respectively connected to the AC positive end and the AC negative end, and the AC switch is connected in parallel between the AC positive end and the AC negative end; each power semiconductor switch component includes a fully controlled semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel.

7. The high-voltage cascade energy storage system based on nested power modules according to claim 6, characterized in that: The four fully-controlled semiconductor devices all adopt IGBTs, and the four unidirectional uncontrollable semiconductor devices all adopt diodes.

8. The high-voltage cascade energy storage system based on nested power modules according to claim 1, characterized in that: After a number of DC link type energy storage units are connected in parallel, a capacitor C1 is also connected in parallel. The capacitor C1 is located between the number of DC link type energy storage units connected in parallel and the H-bridge circuit.

9. The high-voltage cascade energy storage system based on nested power modules according to claim 1, characterized in that: The AC positive end of the three-phase chain energy storage bridge arm is connected to the three-phase line of the power grid through the bridge arm reactor, the bridge arm equivalent resistor, and the grid-side reactor in sequence, and the AC negative end of the three-phase chain energy storage bridge arm is connected to a common point.

10. A control method for a high-voltage cascade energy storage system based on a nested power module, applied to the high-voltage cascade energy storage system based on a nested power module according to any one of claims 1 to 9, characterized in that: The control method includes the following fault removal modes: When a battery pack fails, the battery pack is short-circuited through the half-bridge circuit corresponding to the battery pack, and other battery packs in the DC chain energy storage unit operate normally; When a DC chain energy storage unit fails, the DC switch of the DC chain energy storage unit is opened to cut out the DC chain energy storage unit, and other DC chain energy storage units in the nested power module operate normally; When a certain nested power module fails, the AC switch in the nested power module is closed to short-circuit the nested power module, and other nested power modules in each phase chain energy storage bridge arm operate normally.

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