Valve hall type high-pressure cascade energy storage system based on nested power module

Abstract

The utility model relates to the technical field of high-voltage cascade energy storage systems, and discloses a valve hall type high-voltage cascade energy storage system based on nested power modules, which comprises three phases of chain type energy storage bridge arms respectively connected with three phase lines of a power grid, 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 energy storage units and an H-bridge circuit, the plurality of direct-current energy storage units are connected in parallel and then 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 DC energy storage unit comprises a battery cluster and a DCDC converter connected with the battery cluster in parallel, the DCDC converter comprises a first capacitor, a second capacitor and a power conversion unit, and the power conversion unit comprises three full-control semiconductor devices and an inductor. According to the utility model, each battery cluster is accurately controlled through the DCDC converter in the embedded power module, so that the reliability of the valve hall type high-voltage cascade energy storage system is improved.

Description

Technical Field

[0001] This utility model relates to the technical field of high-voltage cascaded energy storage systems, and in particular to a valve hall type high-voltage cascaded energy storage system based on nested power modules. Background Technology

[0002] Existing large-capacity energy storage power stations typically operate multiple energy storage PCS units in parallel on the low-voltage AC side, and then step up the voltage through transformers before connecting to the medium- and high-voltage power grid. However, an excessive number of parallel energy storage PCS units can lead to various stability issues, as well as problems with circulating current and uneven power distribution. Furthermore, the battery energy storage system described in this approach has a large footprint, complex control system, difficult coordination control, high transformer losses, and low system efficiency. In contrast, a high-voltage cascaded energy storage system based on a cascaded H-bridge converter easily achieves various high-voltage cascading and capacity expansion by introducing distributed battery modules on the DC side of each phase H-bridge. In addition, the DC-DC converter can adjust the charging and discharging current, voltage, and power of each DC energy storage unit at any time, thus achieving "one cluster, one management" and zero circulating current between battery clusters. This effectively achieves SOC balancing between battery clusters, ensuring that the available power of different battery clusters remains consistent. Simultaneously, this solution reduces battery circulating current and eliminates the need for a power frequency transformer, thereby meeting the requirements for high efficiency, high reliability, large capacity, and safety in battery energy storage power conversion.

[0003] However, existing high-voltage cascaded energy storage systems also have various problems, which are analyzed in detail below:

[0004] 1) As described in patent CN111049273A, a high-voltage cascaded energy storage device uses a high-voltage cascading scheme where an H-bridge is connected in parallel with a battery cluster and then cascaded to form a high-voltage energy storage system. However, this scheme cannot bypass the faulty battery cluster, resulting in low reliability of the high-voltage energy storage system.

[0005] 2) As described in patent CN215267793U, the integrated high-voltage cascaded energy storage system and cascaded PCS power units are based on a single battery cluster connected in parallel with an H-bridge and then cascaded. An LC filter is connected between the battery cluster and the H-bridge to suppress the 2 times harmonic ripple current of the battery cluster. Simultaneously, the H-bridge ports use parallel mechanical switches for PCS power unit bypass design. This technical solution cannot achieve fine-grained management of the battery clusters, and if a single battery cluster fails, the entire H-power unit shuts down, resulting in low system reliability.

[0006] Valve-hall type high-voltage cascaded energy storage systems, which house the high-voltage cascaded energy storage system within a valve hall, have high installation and maintenance costs and place higher demands on the reliability and stability of the high-voltage cascaded energy storage system. Therefore, improving the topology of high-voltage cascaded energy storage systems and enhancing their operational reliability has become a pressing technical challenge in this field. Utility Model Content

[0007] The purpose of this invention is to provide a valve hall type high-voltage cascaded energy storage system based on nested power modules. By precisely controlling each battery cluster through the DC-DC converter in the embedded power module, any battery cluster can be bypassed after a failure, avoiding downtime caused by local faults, reducing the failure rate of the valve hall type high-voltage cascaded energy storage system, and thus improving the reliability of the valve hall type high-voltage cascaded energy storage system.

[0008] To achieve the above objectives, this utility model provides the following solution:

[0009] A valve hall type high-voltage cascaded energy storage system based on nested power modules includes a three-phase chain energy storage bridge arm connected to the three-phase lines of the power grid. Each phase chain energy storage bridge arm includes multiple cascaded nested power modules. Each nested power module includes several DC energy storage units and an H-bridge circuit. Several DC energy storage units are connected in parallel and connected to the DC side of the H-bridge circuit. The AC side of the H-bridge circuit is connected to an AC switch.

[0010] The DC energy storage unit includes a battery cluster and a DC-DC converter connected in parallel with the battery cluster. The DC-DC converter includes a first capacitor, a second capacitor, and a power conversion unit. The first capacitor is connected in parallel with the positive and negative terminals of the battery cluster.

[0011] The power conversion unit includes a first fully controlled semiconductor device, a second fully controlled semiconductor device, a third fully controlled semiconductor device, and an inductor. The first fully controlled semiconductor device, the second fully controlled semiconductor device, and the third fully controlled semiconductor device all adopt MOSFETs.

[0012] The drain of the first fully controllable semiconductor device is connected to the positive terminal of the battery cluster, and the source is connected to one end of the inductor; the other end of the inductor is connected to the drain of the second fully controllable semiconductor device and the source of the third fully controllable semiconductor device. The source of the second fully controllable semiconductor device is connected to the negative terminal of the battery cluster. The drain of the third fully controllable semiconductor device and one end of the second capacitor are connected to form a DC positive terminal, and the other end of the second capacitor is connected to the negative terminal of the battery cluster to form a DC negative terminal.

[0013] Furthermore, multiple power conversion units are provided, and the multiple power conversion units are arranged in parallel.

[0014] Furthermore, the H-bridge circuit includes four power semiconductor switching components. Every two power semiconductor switching 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 positive AC terminal and the negative AC terminal. The AC switch is connected in parallel between the positive AC terminal and the negative AC terminal. Each power semiconductor switching component includes a fully controllable semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel.

[0015] Furthermore, the fully controllable semiconductor device in the power semiconductor switching assembly is an IGBT, and the unidirectional uncontrollable semiconductor device is a diode.

[0016] Furthermore, after several DC energy storage units are connected in parallel, a capacitor C1 is also connected in parallel, and the capacitor C1 is located between the several parallel DC energy storage units and the H-bridge circuit.

[0017] Furthermore, the positive AC terminals of the three-phase chained energy storage bridge arm are connected to the three-phase lines of the power grid in sequence through the bridge arm reactor, the bridge arm equivalent resistance, and the grid-side reactor, while the negative AC terminals of the three-phase chained energy storage bridge arm are all connected to the common point.

[0018] According to the specific embodiments provided by this utility model, the valve hall type high-voltage cascaded energy storage system based on nested power modules provided by this utility model discloses the following technical effects:

[0019] Based on the circuit topology and application scenario, the nested power module is designed to include at least a DC-DC converter and an H-bridge circuit. The DC-DC converter is connected to the battery cluster. Each DC-DC converter can identify the consistency of the state of charge of the entire battery cluster and realize state of charge equalization control of the battery cluster.

[0020] The nested power module provided by this invention features a DC-DC converter that precisely controls the charging and discharging voltage, current, and power of the battery clusters, truly achieving non-circulating current operation and "one cluster, one management." Secondly, the nested power module can exit the system even if any battery cluster fails, ensuring the valve hall high-voltage cascaded energy storage system does not shut down, significantly reducing the failure rate and thus improving the operational reliability of the valve hall high-voltage cascaded energy storage system.

[0021] This invention addresses the low reliability and limited scalability issues of existing high-voltage cascaded energy storage systems by introducing fully controllable semiconductors and switching devices. The fully controllable semiconductor devices and AC switching devices in the nested power module described in this invention enable rapid disconnection from the valve hall high-voltage cascaded energy storage system in the event of a battery cluster failure, without affecting the normal operation of the system. Furthermore, the fully controllable / uncontrollable semiconductors and switching devices used are common and conventional components, offering significant economic advantages.

[0022] The combination of inductors and fully controlled semiconductor devices inside the nested power module described in this utility model allows DC energy storage units to be connected in parallel arbitrarily. While isolating faulty battery clusters, it also facilitates the power expansion and capacity increase of the energy storage system, thereby improving the operational reliability of the high-voltage cascaded energy storage system.

[0023] The nested power module described in this invention can easily boost the voltage of a valve hall high-voltage energy storage system, expanding the application scenarios of valve hall high-voltage cascaded energy storage systems and greatly improving the operational reliability of valve hall high-voltage cascaded energy storage systems. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a hardware topology diagram of the valve hall type high-voltage cascaded energy storage system based on nested power modules according to this utility model.

[0026] Figure 2 This is a schematic diagram of the internal connection and control of the nested power module of this utility model;

[0027] Figure 3 This is a hardware topology diagram of Embodiment 1 of the nested power module of this utility model;

[0028] Figure 4 This is a hardware topology diagram of Embodiment 2 of the nested power module of this utility model;

[0029] Figure 5 This is a hardware topology diagram of Embodiment 1 of the DC-DC converter circuit of this utility model;

[0030] Figure 6 This is a hardware topology diagram of Embodiment 2 of the DC-DC converter circuit of this utility model;

[0031] Explanation of reference numerals in the attached diagram: T1, T2, T3, T4 - IGBT (Integrated Biological Device); Q1a, Q2a, Q3a, Q1-1, Q2-1, Q3-1, Q1-2, Q2-2, Q3-2 - MOSFET (Metallic Electron Device); D1, D2, D3, D4 - Diode (Unidirectional Uncontrollable Semiconductor Device).

[0032] 1. Phase-chained energy storage bridge arm; 2. Nested power module; 3. DC energy storage unit. Detailed Implementation

[0033] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0034] The purpose of this invention is to provide a valve hall type high-voltage cascaded energy storage system based on nested power modules. According to the circuit topology and application scenario, the nested power module is designed to include at least a DC-DC converter and an H-bridge circuit. The DC-DC converter of the nested power module is connected in parallel with the battery cluster. The DC-DC converter includes multiple fully controllable semiconductor devices, inductors and capacitors, etc., which can effectively regulate the charging and discharging voltage, current and power of the battery cluster, thereby realizing the balanced control of the state of charge of the battery cluster.

[0035] In the valve hall-type high-voltage cascaded energy storage system based on nested power modules, DC-DC converters are connected to battery clusters. Each DC-DC converter can identify the consistency of the state of charge (SOC) of the entire battery cluster and achieve SOC equalization control for the battery cluster. Connecting one DC-DC converter from the nested power module in parallel with the battery cluster yields a set of DC energy storage units. Each set of DC energy storage units can achieve SOC equalization control for a single battery cluster. The nested power module can consist of multiple sets of DC energy storage units, and can identify the consistency of the SOC of multiple sets of DC energy storage units and achieve SOC equalization control for multiple sets of DC energy storage units. The nested power module can consist of multiple sets of DC energy storage units and an H-bridge circuit. Based on the nested power module, the energy storage system controller can identify the SOC of all internal batteries and achieve SOC equalization control for each battery cluster.

[0036] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figures 1-6As shown, the valve hall-type high-voltage cascaded energy storage system based on nested power modules provided by this utility model includes a three-phase chained energy storage bridge arm 1 connected to the three-phase lines (A, B, and C phases) of the power grid. Each phase chained energy storage bridge arm 1 includes multiple cascaded nested power modules 2. Each nested power module 2 includes several DC energy storage units 3 and an H-bridge circuit. The several DC energy storage units 3 are connected in parallel and then connected to the DC side of the H-bridge circuit. The AC side of the H-bridge circuit is connected to an AC switch Ki, where i represents the number of AC switches. The DC energy storage unit 3 includes a battery cluster and a DC-DC converter connected in parallel with the battery cluster. The three-phase chained energy storage bridge arm 1 and the multiple cascaded nested power modules 2 inside it are all located in the valve hall. The valve hall is equipped with a temperature and humidity control system to ensure long-term stable operation of the equipment in an optimal environment.

[0038] The nested power module's DC-DC converter is connected in parallel with the battery cluster. The DC-DC converter includes multiple fully controllable semiconductor devices, inductors, and capacitors, effectively regulating the charging and discharging voltage, current, and power of the battery cluster, thereby achieving balanced state-of-charge control. Connecting the nested power module's DC-DC converter in parallel with the battery cluster acts as an electronic switch, allowing for rapid disconnection or (approximately 1µs) removal from the battery cluster. If any battery cluster fails, the corresponding DC-DC converter can be disconnected, removing that battery cluster from the DC energy storage unit group without affecting the normal operation of other DC energy storage units, thus improving the reliability of the valve-hall type high-voltage cascaded energy storage system.

[0039] For example, such as Figure 3 As shown, each nested power module 2 includes a DC energy storage unit 3 and an H-bridge circuit. The DC energy storage unit 3 is also connected in parallel with a capacitor C1, which is located between the DC energy storage unit 3 and the H-bridge circuit.

[0040] For example, such as Figure 4 As shown, each nested power module 2 includes N DC energy storage units 3 and an H-bridge circuit. After the N DC energy storage units are connected in parallel, a capacitor C1 (preferably a thin-film capacitor) is also connected in parallel. The capacitor C1 is located between the several parallel DC energy storage units and the H-bridge circuit; wherein, N is greater than or equal to 3.

[0041] like Figure 5 As shown, the structure of a first DC-DC converter is disclosed: the DC-DC converter includes a first capacitor Cin1, a second capacitor Co1 and a power conversion unit, wherein the first capacitor Cin1 is connected in parallel with the positive and negative terminals of the battery cluster;

[0042] The power conversion unit is provided with one unit, including a first fully controlled semiconductor device Q1a, a second fully controlled semiconductor device Q1-1, a third fully controlled semiconductor device Q1-2, and an inductor L1. The first fully controlled semiconductor device Q1a, the second fully controlled semiconductor device Q1-1, and the third fully controlled semiconductor device Q1-2 are all MOSFETs.

[0043] The drain (D) of the first fully controllable semiconductor device Q1a is connected to the positive terminal (BAT1+) of the battery cluster. The source (S) of Q1a is connected to one end of the inductor L1. The other end of the inductor L1 is connected to the drain (D) of the second fully controllable semiconductor device Q1-1 and the source (S) of the third fully controllable semiconductor device Q1-2. The source (S) of the second fully controllable semiconductor device Q1-1 is connected to the negative terminal (BAT1-) of the battery cluster. The drain (D) of the third fully controllable semiconductor device Q1-2 is connected to one end of the second capacitor Co1 to form the positive DC terminal DC+. The other end of the second capacitor Co1 is connected to the negative terminal (BAT1-) of the battery cluster to form the negative DC terminal DC-.

[0044] Inductor L1 is used for energy storage and release during the switching process of fully controllable semiconductor devices, thereby achieving buck or boost control. Capacitors Cin1 and Co1 are used for input and output DC-side filtering in power electronic DC-DC converters.

[0045] The battery cluster and the first type of DC-DC converter are connected as described above, forming a DC positive terminal (DC+) and a DC negative terminal (DC-) externally, which together constitute a complete DC energy storage unit.

[0046] like Figure 6 The diagram shows the structure of a second type of DC-DC converter: a three-phase interleaved parallel DC-DC converter, which has three identical power conversion units inside. Each power conversion unit includes: fully controlled semiconductor devices Q1a, Q1-1, and Q1-2, and inductors L1, Cin1, and Co1 connected as follows: capacitor Cin1 is connected in parallel with the positive and negative terminals of the battery cluster; the drain of Q1a is connected to the positive terminal (BAT1+) of the battery cluster; the source of Q1a is connected to one end of inductor L1; the other end of inductor L1 is connected to the drain of Q1-1 and the source of Q1-2; the source of Q1-1 is connected to the negative terminal (BAT1-) of the battery cluster; the drain of Q1-2 is connected to one end of capacitor Co1 to form the positive DC terminal DC+; and the other end of capacitor Co1 is connected to the negative terminal (BAT1-) of the battery cluster to form the negative DC terminal DC-. The input terminals of the three power conversion units are connected in parallel to the positive terminal (BAT1+) and the negative terminal (BAT1-) of the battery, and the output terminals of the three power conversion units are connected in parallel to the positive DC terminal (DC+) and the negative DC terminal (DC-).

[0047] The three power conversion units can significantly reduce the ripple voltage and current of the output and input capacitors, which is very beneficial for lithium batteries; in addition, the three power conversion units have lower cost and lower control complexity.

[0048] The battery cluster and the second type of DC-DC converter are connected as described above, forming a DC positive terminal (DC+) and a DC negative terminal (DC-) externally, which together constitute a complete DC energy storage unit.

[0049] The positive DC terminal (DC+) and negative DC terminal (DC-) of multiple DC energy storage units are connected respectively.

[0050] The H-bridge circuit includes four power semiconductor switching components. Each pair of power semiconductor switching components is connected in series in the same direction to form a bridge arm. The two bridge arms are connected in parallel, with their midpoints connected to the AC positive and negative terminals, respectively. An AC switch is connected in parallel between the AC positive and negative terminals. Each power semiconductor switching component includes a fully controllable semiconductor device and a unidirectional uncontrollable semiconductor device arranged in parallel. The fully controllable semiconductor devices T1 and T2, T3 and T4 in the power semiconductor switching components are IGBTs, and the unidirectional uncontrollable semiconductor devices D1, D2, D3, and D4 are diodes.

[0051] Two DC-DC converters are formed by connecting fully controlled semiconductor devices T1 and T2, and T3 and T4 in series. The collectors (C) of T1 and T3 are connected to the positive DC terminal (DC+), and the emitters (E) of T2 and T4 are connected to the negative DC terminal (DC-). A capacitor C is connected in parallel between the positive DC terminal (DC+) and the negative DC terminal (DC-). The midpoints M+ and M- of the two DC-DC converters are brought out.

[0052] The above-mentioned modules containing multiple DC energy storage units and H-bridge circuits are collectively referred to as nested power modules.

[0053] Multiple DC energy storage units are connected in parallel and then connected to the DC side of an H-bridge circuit. The H-bridge circuit allows for finer control and enables bidirectional power flow. It can absorb energy from the grid to charge the batteries of the multiple DC energy storage units, and it can also discharge the batteries to release energy back to the grid, providing reactive power compensation. The nested power modules are switched on and off via AC switches.

[0054] The positive AC terminals of the three-phase chained energy storage bridge arm are connected to the three-phase lines of the power grid in sequence through the bridge arm reactor L, the bridge arm equivalent resistance R, and the grid-side reactor Ls. The negative AC terminals of the three-phase chained energy storage bridge arm are all connected to the common point.

[0055] In the above embodiments, the battery cluster (such as...) Figure 4BAT11, BAT12, ... BAT1n can also be supercapacitor packs or other energy storage units, such as lead-acid batteries, sodium-sulfur batteries, flow batteries and lithium-ion battery clusters.

[0056] This invention relates to a high-voltage cascaded energy storage system based on nested power modules. The nested power modules of the described high-voltage cascaded energy storage system can precisely control the charging and discharging current of each battery cluster and achieve balanced state of charge control among the battery clusters. The DC-DC converter inside the nested power module provided by this invention has multiple solutions, including but not limited to the first and second DC-DC converter technologies shown in this patent. The DC-DC converter described in this patent can precisely control the charging and discharging voltage, current, and power, truly achieving non-circulating current operation and 'one cluster, one management'. Furthermore, the nested power modules can exit the system after any battery cluster fails, preventing the valve hall high-voltage cascaded energy storage system from shutting down, greatly reducing the failure rate of the valve hall high-voltage cascaded energy storage system and thus improving its operational reliability.

[0057] This invention addresses the low reliability and limited scalability issues of existing high-voltage cascaded energy storage systems by introducing fully controllable semiconductors and switching devices. The fully controllable semiconductor devices and AC switching devices Ki in the nested power module described in this invention enable rapid disconnection from the valve hall high-voltage cascaded energy storage system in the event of a battery cluster failure, without affecting the normal operation of the valve hall high-voltage cascaded energy storage system. Furthermore, the fully controllable / uncontrollable semiconductors and switching devices used are common and conventional components, offering significant economic advantages.

[0058] The combination of inductors and fully controlled semiconductor devices inside the nested power module described in this utility model allows DC energy storage units to be connected in parallel arbitrarily. While isolating faulty battery clusters, it also facilitates the power expansion and capacity increase of the energy storage system, thereby improving the operational reliability of the high-voltage cascaded energy storage system.

[0059] The nested power module described in this invention can easily boost the voltage of a valve hall high-voltage energy storage system, expanding the application scenarios of valve hall high-voltage cascaded energy storage systems and greatly improving the operational reliability of valve hall high-voltage cascaded energy storage systems.

[0060] This utility model also discloses a control method for a valve hall-type high-voltage cascaded energy storage system based on nested power modules:

[0061] 1. Battery charging process:

[0062] In the valve hall type high-voltage cascaded energy storage system, the phase current flows in from the M+ of the embedded power module, and completes the DC side charging (flowing out from M-) through the unidirectional uncontrollable semiconductor devices D1 and D4. The charging current charges the battery cluster through the positive terminal (DC+) and Q1-2, L1, and Q1a on the DC side. Finally, the charging current flows into the negative terminal (DC-) and then flows out from the M- port through D4 of the H-bridge circuit.

[0063] The phase current of the valve hall type high voltage cascaded energy storage system can also flow in from M- of the embedded power module, and complete the DC side charging (flowing out from M+) through unidirectional uncontrollable semiconductor device D3 and unidirectional uncontrollable semiconductor device D2. The charging DC flows from the positive terminal (DC+) through Q1-2, L1, and Q1a to charge the battery cluster. Finally, the charging current flows into the DC negative terminal (DC-) and then flows out from the M- port through D2 of the H-bridge circuit.

[0064] In the above process, the first type of DC-DC converter operates in Buck mode, where Q1-2 operates in either normally-on mode or Pulse Width Modulation (PWM) mode to precisely control the charging current of the battery cluster, thereby achieving balanced state of charge control within the battery cluster. Q1-1 is in the off state, and Q1a is in the on state.

[0065] In the above process, the second type of DC-DC converter operates in Buck mode, where Q1-2, Q2-2, and Q3-2 operate in either normally-on mode or pulse width modulation (PWM) mode to precisely control the charging current of the battery cluster, thereby achieving balanced state of charge control within the battery cluster. Q1-1, Q2-1, and Q3-1 are in the off state, while Q1a, Q2a, and Q3a are in the on state.

[0066] During the above process, circuits T1, T2, T3, and T4 of the H-bridge circuit operate in SPWM mode.

[0067] 2. Battery pack discharge process:

[0068] If the battery voltage is high, the discharge current of the battery cluster inside the embedded power module flows through Q1a, inductor L, and Q1-2 into the DC positive terminal DC+, and finally achieves AC output through the H-bridge to discharge the energy storage system. If the battery voltage is low, the discharge current of the battery cluster inside the embedded power module flows through Q1a, inductor L, and Q1-1. First, inductor L stores energy. When Q1-1 is off, the energy stored in inductor L is released through Q1-2 and flows into the DC positive terminal DC+, and finally achieves AC output through the H-bridge circuit to discharge the energy storage system.

[0069] In the above process, the first type of DC-DC converter operates in either normally-on mode or BOOST mode. Q1-1 operates in pulse width modulation (PWM) mode to precisely control the discharge current of the battery cluster, thereby achieving balanced state of charge control within the battery cluster. Q1-2 is in the off state, and Q1a is in the on state.

[0070] In the above process, the second type of DC-DC converter operates in either normally-on mode or BOOST mode. Q1-1, Q2-1, and Q3-1 operate in pulse width modulation (PWM) mode to precisely control the discharge current of the battery cluster, thereby achieving balanced state of charge control within the battery cluster. Q1-2, Q2-2, and Q3-2 are in the off state, while Q1a, Q2a, and Q3a are in the on state.

[0071] During the above process, circuits T1, T2, T3, and T4 of the H-bridge circuit operate in SPWM mode.

[0072] 3. Exit process after battery pack failure:

[0073] If a battery cluster in a valve hall-type high-voltage cascaded energy storage system malfunctions, such as overcharging, over-discharging, over-temperature, over-voltage, or under-voltage, the faulty battery cluster can be deactivated by adjusting the charging and discharging voltage, current, and power of the DC-DC converter in the nested power module. When a battery cluster in the nested power module malfunctions, the control system can quickly detect the fault signal and shut down the first type of DC-DC converter (i.e., simultaneously shut down the fully controlled semiconductor device Q1a and the fully controlled semiconductor device Q1-2) and the second type of DC-DC converter (i.e., simultaneously shut down the fully controlled semiconductor devices Q1a, Q2a, Q3a and the fully controlled semiconductor devices Q1-2, Q2-2, Q3-2).

[0074] After receiving commands such as power and current, the nested power module sends the current value of each DC energy storage unit to the H-bridge controller through control signals. The DC-DC converters inside the DC energy storage units control the current and power of each DC-DC converter by controlling the turn-on and turn-off times of the fully controlled semiconductor devices.

[0075] This process takes approximately microseconds. The nested power module will not shut down due to a fault, truly achieving "one cluster, one management" and preventing inter-cluster circulating currents, thus improving the overall efficiency of the DC energy storage unit.

[0076] Meanwhile, the nested power module port is connected in parallel with AC connection switch K11. In the event of a major fault, K11 will close, and the valve hall high-voltage cascaded energy storage system can simply remove the faulty battery cluster without affecting the normal operation of the entire valve hall energy storage system. This greatly reduces the failure rate of the valve hall high-voltage cascaded energy storage system and thus improves its reliability.

[0077] In the above embodiments, the nested power module includes three output voltage levels: V-, 0, and V+, which can effectively adjust the output voltage and achieve voltage balance control of a single battery pack. The logical relationship between the switching device control of the H-bridge circuit and the output voltage is as follows:

[0078] When the fully controlled semiconductor devices T1 and T4 are turned on, the output voltage V+ is achieved.

[0079] When the fully controlled semiconductor devices T1 and T3 are turned on, the output voltage is 0.

[0080] When the fully controlled semiconductor devices T2 and T3 are turned on, the output voltage V- is achieved.

[0081] When the fully controlled semiconductor devices T2 and T4 are turned on, the output voltage is 0.

[0082] By controlling the turn-on and turn-off timing and turn-on time of the fully controllable semiconductor devices T1, T2, T3, and T4 in the H-bridge circuit, the charging and discharging current of multiple DC energy storage units in the nested power module can be effectively adjusted.

[0083] The valve hall-type high-voltage cascaded energy storage system based on nested power modules provided by this utility model not only has battery cluster state-of-charge equalization control, but also has the following advantages:

[0084] 1) The DC-DC converter can disconnect any one group of battery clusters without causing other DC energy storage units to fail and shut down; when the SOC imbalance of a single DC energy storage unit exceeds a certain value, the faulty DC energy storage unit can be removed (or isolated) by disconnecting the DC-DC converter of the DC energy storage unit without affecting the normal operation of other DC energy storage units, thereby improving the reliability of the valve hall type high-voltage cascaded energy storage system.

[0085] 2) The DC-DC converter has current regulation and power regulation capabilities, and can quickly respond to the power commands of the corresponding valve hall high-voltage cascaded energy storage system to achieve stable grid voltage and frequency.

[0086] 3) If multiple battery clusters in a DC energy storage unit fail and exit, it will not cause other DC energy storage units to fail and shut down; when multiple battery clusters in a nested power module fail, the nested power module can be bypassed by closing the AC switch Ki through the nested power module. The nested power module will exit the valve hall high-voltage cascaded energy storage system without affecting the normal operation of the valve hall high-voltage cascaded energy storage system, thereby improving the reliability of the valve hall high-voltage cascaded energy storage system.

[0087] 4) The nested power module will exit after multiple faults, which will not cause the valve hall type high-voltage cascaded energy storage system to fail and shut down.

[0088] 5) The nested power module provides the current and power of each DC energy storage unit according to the current and power commands and the battery SOC. The DC-DC converter receives the current and power commands and realizes DC side voltage regulation and stable power output.

[0089] The above measures reduced the failure rate of the valve hall high-voltage cascaded energy storage system, thereby improving its operational reliability.

[0090] Multiple DC energy storage units can be easily connected in parallel, and multiple nested power modules can be easily cascaded, thus facilitating the expansion and voltage boosting of valve hall high-voltage energy storage systems. Balanced control and protection measures greatly improve the operational reliability of valve hall high-voltage cascaded energy storage systems.

[0091] In summary, the valve hall type high-voltage cascaded energy storage system and its control method based on nested power modules described in this utility model include fully nested power modules, bridge arm reactors L, bridge arm equivalent resistance R, grid-side reactors Ls, and the power grid. In this high-voltage cascaded energy storage system, the nested power modules of each phase are connected in series. The M-terminal of the bottom nested power module is connected to the M-terminals of the nested power modules at the bottom of the other two phases, and is connected to the power grid N. The M+terminal of the bottom nested power module is connected in series with the M-terminal of the adjacent nested power module in the same phase. Multiple nested power modules are connected sequentially in this manner. The M+ terminal of the last nested power module is connected in series with each reactor and then connected to phase A of the power grid. The connection methods for phases B and C of the power grid are the same as for phase A, and will not be described further here.

[0092] If there are many faulty battery clusters inside the nested power module, an AC connection switch Ki is connected in parallel to the port of the nested power module. After Ki is closed, the high-voltage cascaded energy storage system removes the faulty module without affecting the normal operation of the entire energy storage system. This greatly reduces the failure rate of the valve hall type high-voltage cascaded energy storage system, thereby improving the reliability of the valve hall type high-voltage cascaded energy storage system.

[0093] This document uses specific examples to illustrate the principles and implementation methods of this utility model. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this utility model. Furthermore, those skilled in the art will recognize that, based on the ideas of this utility model, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A valve hall type high voltage cascaded energy storage system based on nested power modules, comprising three phase chain-link energy storage bridge arms connected to three phase lines of a power grid respectively, characterized in that, Each phase chain energy storage bridge arm comprises a plurality of cascaded nested power modules, each of which comprises a plurality of DC energy storage units and an H-bridge circuit, the plurality of DC 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 energy storage unit comprises a battery cluster and a DC / DC converter connected in parallel with the battery cluster, the DC / DC converter comprises a first capacitor, a second capacitor and a power conversion unit, and the first capacitor is connected in parallel with the positive and negative electrodes of the battery cluster; The power conversion unit comprises a first fully-controlled semiconductor device, a second fully-controlled semiconductor device, a third fully-controlled semiconductor device and an inductor, and the first, second and third fully-controlled semiconductor devices are MOSFETs; The drain electrode of the first fully-controlled semiconductor device is connected to the positive electrode of the battery cluster, and the source electrode is connected to one end of the inductor; the other end of the inductor is connected to the drain electrode of the second fully-controlled semiconductor device and the source electrode of the third fully-controlled semiconductor device, the source electrode of the second fully-controlled semiconductor device is connected to the negative electrode of the battery cluster, the drain electrode of the third fully-controlled semiconductor device and one end of the second capacitor constitute a DC positive terminal, and the other end of the second capacitor is connected to the negative electrode of the battery cluster to constitute a DC negative terminal.

2. The nested power module based valve hall high voltage cascaded energy storage system of claim 1, wherein, The power conversion unit is provided with a plurality of power conversion units connected in parallel.

3. The nested power module based valve hall high voltage cascaded energy storage system of claim 1, wherein, The H-bridge circuit comprises four power semiconductor switch assemblies, each two power semiconductor switch assemblies are connected in series in the same direction to form a bridge arm, two bridge arms are connected in parallel, and the midpoints of the two bridge arms are connected to an AC positive terminal and an AC negative terminal respectively, and the AC switch is connected in parallel between the AC positive terminal and the AC negative terminal; each power semiconductor switch assembly comprises a fully-controlled semiconductor device and a unidirectional non-controllable semiconductor device connected in parallel.

4. The nested power module based valve hall high voltage cascaded energy storage system of claim 3, wherein, The fully-controlled semiconductor device in the power semiconductor switch assembly is an IGBT, and the unidirectional non-controllable semiconductor device is a diode.

5. The nested power module based valve hall high voltage cascaded energy storage system in accordance with claim 1, wherein, The plurality of DC energy storage units are also connected in parallel with a capacitor C1, and the capacitor C1 is located between the plurality of parallel DC energy storage units and the H-bridge circuit.

6. The nested power module based valve hall high voltage cascaded energy storage system in accordance with claim 1, wherein, The AC positive terminals of the three-phase chain energy storage bridge arms are sequentially connected to the three-phase lines of the power grid through a bridge arm reactor, a bridge arm equivalent resistance and a network-side reactor, and the AC negative terminals of the three-phase chain energy storage bridge arms are connected to a common point.

Images