STATCOM integrated energy storage system and fault protection method thereof

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By combining the advantages of IGBT and IGCT in the STATCOM integrated energy storage system and adopting a hybrid topology, the problems of large on-state loss of IGBT-type full-bridge submodule and lack of desaturation protection of IGCT-type full-bridge submodule are solved, and efficient fault protection and low-loss STATCOM integrated energy storage system are achieved.

CN120498273APending Publication Date: 2025-08-15CHINA THREE GORGES CORPORATION +1

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Patent Information

Application Number: CN202510810693.9
Authority / Receiving Office: CN · China
Patent Type: Applications(China)
Current Assignee / Owner
Filing Date: 2025-06-17
Publication Date: 2025-08-15

AI Technical Summary

Technical Problem

The IGBT-type full-bridge submodule has large on-state losses, while the IGCT-type full-bridge submodule does not have the ability to desaturate protection, resulting in device damage.

Method used

A new topology is adopted that combines the IGBT full-bridge submodule and the IGCT full-bridge submodule, combining the overcurrent protection and desaturation protection capabilities of the IGBT and the low-pass loss of the IGCT to form a hybrid topology. The overcurrent protection capabilities of the IGBT are used to turn off the current first in the event of a fault, and then turn off the IGCT to avoid direct short circuit.

Benefits of technology

While improving system efficiency, it has the ability to pass through the bridge arm to avoid damage to IGCT devices due to high current, reduce on-state losses and enhance fault protection.

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Abstract

The invention relates to the technical field of high-voltage large-capacity energy storage, and discloses an STATCOM (static synchronous compensator) integrated energy storage system and a fault protection method thereof, the STATCOM integrated energy storage system comprises three phases of commutation chains, and each phase of commutation chain is formed by cascading a plurality of IGBT (insulated gate bipolar transistor) type device sub-modules and a plurality of IGCT (integrated gate commutation thyristor) type device sub-modules. According to the STATCOM integrated energy storage system, an IGBT full-bridge sub-module and an IGCT full-bridge sub-module are combined to replace a novel topological structure of a pure IGBT type or IGCT type full-bridge sub-module, the advantages that an IGBT has the over-current protection and desaturation protection capacity and the advantages that an IGCT is small in on-state loss are combined, the system efficiency is improved, and meanwhile the in-bridge-arm straight-through protection capacity is achieved.

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Description

Technical Field

[0001] The present invention relates to the technical field of high-voltage and large-capacity energy storage, and in particular to a STATCOM integrated energy storage system and a fault protection method thereof. Background Art

[0002] Due to fluctuations in wind resources, wind farm power generation is characterized by random uncertainty. Large-scale wind farms typically deploy energy storage devices to regulate power generation, achieving peak-shaving and valley-filling, smoothing output. Furthermore, wind power collection systems absorb large amounts of reactive power, and this reactive power demand varies with power generation output. Therefore, dynamic reactive power compensation equipment is required to provide reactive power compensation and stabilize grid connection voltage. Combining these two application requirements, the STATCOM integrated energy storage system, based on passive filtering circuits, employs a three-phase cascaded commutation chain with either a star or delta connection for commutation. Energy storage batteries are connected to the DC side of each commutation module to achieve four-quadrant power regulation and compensation.

[0003] Fully controlled press-fit devices are the core of power conversion in STATCOM integrated energy storage systems. These devices primarily include thyristor devices, such as integrated gate commutated thyristors (IGCTs), and transistor devices, such as insulated gate bipolar transistors (IGBTs). The submodules in a STATCOM integrated energy storage system topology can be composed of full-bridge power unit submodules comprised of either all IGCTs or all IGBTs. IGBT-based full-bridge submodules exhibit high conduction losses, while IGCT-based full-bridge submodules lack the desaturation protection capabilities of IGBTs, resulting in direct short circuits within the bridge arms that can damage the devices. Summary of the Invention

[0004] In view of this, the present invention provides a STATCOM integrated energy storage system and a fault protection method thereof to solve the problem that the conduction loss of the IGBT-based full-bridge submodule is large, while the IGCT-based full-bridge submodule does not have the desaturation protection capability.

[0005] In a first aspect, the present invention provides a STATCOM integrated energy storage system, comprising: a three-phase commutation chain, wherein each phase commutation chain is composed of a cascade of multiple IGBT device submodules and multiple IGCT device submodules.

[0006] The present invention provides a STATCOM integrated energy storage system, which uses a new topology structure that replaces pure IGBT or IGCT full-bridge submodules with a combination of IGBT full-bridge submodules and IGCT full-bridge submodules. It combines the advantages of IGBT's overcurrent protection and desaturation protection capabilities with IGCT's low on-state loss, and has the ability to provide direct-through protection within the bridge arm while improving system efficiency.

[0007] In an optional embodiment, the IGBT device submodule includes: an IGBT full-bridge inverter, a first energy storage unit, and a first filter circuit, wherein the DC side of the IGBT full-bridge inverter is connected to one end of the first filter circuit, the AC side of the IGBT full-bridge inverter is connected to the power grid, and the other end of the first filter circuit is connected to the first energy storage unit.

[0008] In an optional embodiment, the IGCT device submodule includes: an IGCT full-bridge inverter, a second energy storage unit, and a second filter circuit, wherein the DC side of the IGCT full-bridge inverter is connected to one end of the second filter circuit, the AC side of the IGCT full-bridge inverter is connected to the power grid, and the other end of the second filter circuit is connected to the second energy storage unit.

[0009] In an optional implementation, each phase commutation chain further includes: a reactor, and the IGBT full-bridge inverter and the IGCT full-bridge inverter are both connected to the power grid in parallel via the reactor.

[0010] In an optional implementation, the rated voltage level of the IGBT type device submodule is the same as the rated voltage level of the IGCT type device submodule.

[0011] In an optional embodiment, both the first energy storage unit and the second energy storage unit are batteries.

[0012] In a second aspect, the present invention provides a fault protection method for a STATCOM integrated energy storage system, based on the STATCOM integrated energy storage system of the first aspect or any corresponding embodiment thereof, the method comprising:

[0013] When a through fault occurs in the commutation chain and overcurrent occurs, the protection function of the IGBT device submodule in the fault phase bridge arm is first activated to shut down the fault current, and then the IGCT device submodule in the fault phase bridge arm is shut down.

[0014] The present invention provides a fault protection method for a STATCOM integrated energy storage system that combines the advantages of IGBTs' overcurrent protection and desaturation protection capabilities with the low on-state losses of IGCTs. During normal operation, the IGCT's low on-state voltage drop reduces system losses compared to a pure IGBT full-bridge submodule topology. In the event of a direct-through fault in the commutation chain and overcurrent, the IGBT's inherent overcurrent protection or desaturation protection automatically shuts off the current, and then the IGCT shuts down. This prevents damage to the IGCT device caused by a direct-through short circuit in the commutation chain.

[0015] In an optional embodiment, the method further includes:

[0016] When the STATCOM integrated energy storage system operates normally, the voltage amplitude and phase of the AC side output of the IGBT full-bridge inverter and IGCT full-bridge inverter are controlled to absorb or emit the active power or reactive power required by the AC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 Schematic diagram of a STATCOM integrated energy storage system based on an IGBT full-bridge submodule according to an embodiment of the present invention;

[0019] Figure 2 Schematic diagram of a STATCOM integrated energy storage system based on an IGCT full-bridge submodule according to an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of a STATCOM integrated energy storage system according to an embodiment of the present invention;

[0021] Figure 4 This is a fault circuit discharge path of a STATCOM integrated energy storage system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0023] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components; wireless connections or wired connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0025] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Fully controlled press-fit devices are the core of power conversion in large-capacity power electronic equipment, mainly including thyristor devices represented by integrated gate commutated thyristor (IGCT) and transistor devices represented by insulated gate bipolar transistor (IGBT). Figure 1 The STATCOM integrated energy storage system based on IGBT full-bridge submodule is shown in the figure. Figure 2Taking the STATCOM integrated energy storage system shown above as an example, the submodules in this topology can be composed of full-bridge power unit submodules composed of either all IGCT or all IGBT devices. IGBT-based full-bridge submodules have high conduction losses, while IGCT-based full-bridge submodules lack the desaturation protection capabilities of IGBTs. A direct short circuit within the bridge arm can directly damage the device.

[0027] In response to the above technical problems, the present invention proposes a STATCOM integrated energy storage system based on IGBT and IGCT hybrid sub-modules, which can reduce the conduction loss while achieving overcurrent protection. Figure 3 As shown in Figure 1, the STATCOM integrated energy storage system includes three phase commutation chains. Specifically, the three phase commutation chains are: Phase A commutation chain, Phase B commutation chain, and Phase C commutation chain. Each phase commutation chain is composed of a cascade of multiple IGBT device submodules and multiple IGCT device submodules.

[0028] Specifically, this embodiment Figure 1 or Figure 2 Based on this, P IGBTs and Q IGCTs of the same rated voltage are selected to replace all N existing IGBT or ICGT submodules, where P + Q = N. This configuration is applied to all three phases A, B, and C. The values of P and Q are determined based on a comprehensive assessment of the IGBT's voltage tolerance and system operating losses. Because the IGCT and IGBT devices have identical external characteristics, this hybrid topology can be essentially identical to the original topology at the same device rated voltage level, without requiring any changes to the overall structure. The control strategy remains unchanged during normal operation. That is, during normal system operation, the converter current flows through both the IGBT and IGCT submodules. If a through-fault occurs within or between phases of the commutation chain (such as insulation breakdown or multiple grounding on the battery side), resulting in overcurrent, the IGBT first shuts down the current through its own overcurrent protection or desaturation protection, followed by the IGCT. This prevents damage to the IGCT device caused by a through-fault in the commutation chain.

[0029] The present invention provides a STATCOM integrated energy storage system, which uses a new topology structure that replaces pure IGBT or IGCT full-bridge submodules with a combination of IGBT full-bridge submodules and IGCT full-bridge submodules. It combines the advantages of IGBT's overcurrent protection and desaturation protection capabilities with IGCT's low on-state loss, and has the ability to provide direct-through protection within the bridge arm while improving system efficiency.

[0030] In an optional embodiment, as Figure 3As shown, the IGBT device submodule includes: an IGBT full-bridge inverter 11, a first filter circuit 12, and a first energy storage unit 13, wherein the DC side of the IGBT full-bridge inverter 11 is connected to one end of the first filter circuit 12, the AC side of the IGBT full-bridge inverter 11 is connected to the power grid, and the other end of the first filter circuit 12 is connected to the first energy storage unit 13.

[0031] Specifically, an IGBT full-bridge inverter is connected in parallel to the grid via a reactor or intermediate transformer to convert DC power into controllable AC power. The first energy storage unit on the DC side of an IGBT full-bridge inverter is usually a battery, which provides a stable DC power supply for the inverter. The connected reactor is used to filter out high-frequency harmonics and achieve coupling between the inverter output voltage and the grid voltage. By adjusting the phase difference and amplitude relationship between the inverter AC side output voltage and the grid voltage, the control device absorbs or emits active and reactive power. IGBT device submodules generally generate the required AC voltage through carrier phase shifting technology to ensure precise control and optimization of the output voltage.

[0032] In an optional embodiment, the IGCT device submodule includes: an IGCT full-bridge inverter 21, a second filter circuit 22, and a second energy storage unit 23. The DC side of the IGCT full-bridge inverter 21 is connected to one end of the second filter circuit 22, the AC side of the IGCT full-bridge inverter 21 is connected to the power grid, and the other end of the second filter circuit 22 is connected to the second energy storage unit 23.

[0033] Specifically, the IGCT full-bridge inverter is connected in parallel to the grid through a reactor or intermediate transformer to convert DC power into controllable AC power. The second energy storage unit on the DC side of the IGCT full-bridge inverter is usually a battery, which provides a stable DC power supply for the inverter. The connected reactor is used to filter out high-frequency harmonics and achieve coupling between the inverter output voltage and the grid voltage. By adjusting the phase difference and amplitude relationship between the inverter AC side output voltage and the grid voltage, the control device absorbs or emits active and reactive power. The IGCT device submodule generally generates the required AC voltage through carrier phase shifting technology to ensure precise control and optimization of the output voltage.

[0034] The embodiment of the present invention also provides a fault protection method for a STATCOM integrated energy storage system, based on Figure 3 The fault protection method of the STATCOM integrated energy storage system shown includes: when a through fault occurs in the commutation chain and overcurrent occurs, the protection function of the IGBT device submodule in the fault phase bridge arm is first activated to shut down the fault current, and then the IGCT device submodule in the fault phase bridge arm is shut down.

[0035] Specifically, when the STATCOM integrated energy storage system operates normally, the voltage amplitude and phase of the AC side output of the IGBT full-bridge inverter and the IGCT full-bridge inverter are controlled to absorb or emit the active power or reactive power required by the AC system.

[0036] Furthermore, when the system is unlocked and running, if multiple insulation breakdown occurs between the battery and the ground, e.g. Figure 4 As shown, insulation breakdown occurs at the fault point in phase B, causing a direct short-circuit fault on the AC side of multiple H-bridge modules within the commutation chain. In this scenario, direct discharge occurs in the phase B commutation chain through the black path. Because there is virtually no impedance in the loop, the fault current rapidly increases. At this point, the energy storage batteries and support capacitors within the modules continue to discharge toward the fault point. If these H-bridge modules fail to quickly identify the fault and shut down, overcurrent damage to the power devices will occur. Existing IGCT modules typically monitor the commutation chain current using current sensors. When the current exceeds a protection threshold, the module actively locks out. However, due to the extremely rapid current rise rate during a direct fault, the response time after current acquisition and lockout is long, making it ineffective in protecting the devices. To address this fault condition, this embodiment employs the following approach: When a short-circuit fault occurs, the IGBT full-bridge modules within each arm first automatically shut down the current using their own overcurrent protection or desaturation protection capabilities, followed by the IGCT shutdown. This measure effectively prevents the commutation chain direct short-circuit from causing high current damage to the IGCT devices.

[0037] The present invention provides a fault protection method for a STATCOM integrated energy storage system that combines the advantages of IGBTs' overcurrent protection and desaturation protection capabilities with the low on-state losses of IGCTs. During normal operation, the IGCT's low on-state voltage drop reduces system losses compared to a pure IGBT full-bridge submodule topology. In the event of a direct-through fault in the commutation chain and overcurrent, the IGBT's inherent overcurrent protection or desaturation protection automatically shuts off the current, and then the IGCT shuts down. This prevents damage to the IGCT device caused by a direct-through short circuit in the commutation chain.

[0038] Although the embodiments of the present invention have been described with reference to the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention. Such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A STATCOM integrated energy storage system, characterized in that: The system comprises: a three-phase commutation chain, wherein each phase commutation chain is composed of a plurality of IGBT type device submodules and a plurality of IGCT type device submodules connected in cascade.

2. The STATCOM integrated energy storage system according to claim 1, characterized in that: The IGBT device submodule includes: an IGBT full-bridge inverter, a first energy storage unit, and a first filter circuit, wherein the DC side of the IGBT full-bridge inverter is connected to one end of the first filter circuit, the AC side of the IGBT full-bridge inverter is connected to the power grid, and the other end of the first filter circuit is connected to the first energy storage unit.

3. The STATCOM integrated energy storage system according to claim 2, characterized in that: The IGCT device submodule includes: an IGCT full-bridge inverter, a second energy storage unit, and a second filter circuit, wherein the DC side of the IGCT full-bridge inverter is connected to one end of the second filter circuit, the AC side of the IGCT full-bridge inverter is connected to the power grid, and the other end of the second filter circuit is connected to the second energy storage unit.

4. The STATCOM integrated energy storage system according to claim 3, characterized in that: Each phase commutation chain further includes: a reactor, and the IGBT full-bridge inverter and the IGCT full-bridge inverter are both connected to the power grid in parallel via the reactor.

5. The STATCOM integrated energy storage system according to claim 3, characterized in that: The rated voltage level of the IGBT type device submodule is the same as the rated voltage level of the IGCT type device submodule.

6. The STATCOM integrated energy storage system according to claim 3, characterized in that: The first energy storage unit and the second energy storage unit are both batteries.

7. A fault protection method for a STATCOM integrated energy storage system, characterized in that: Based on the STATCOM integrated energy storage system according to any one of claims 1 to 6, the method comprises: When a through fault occurs in the commutation chain and overcurrent occurs, the protection function of the IGBT device submodule in the fault phase bridge arm is first activated to shut down the fault current, and then the IGCT device submodule in the fault phase bridge arm is shut down.

8. The fault protection method for a STATCOM integrated energy storage system according to claim 7, characterized in that: The method further comprises: When the STATCOM integrated energy storage system operates normally, the voltage amplitude and phase of the AC side output of the IGBT full-bridge inverter and IGCT full-bridge inverter are controlled to absorb or emit the active power or reactive power required by the AC system.