High-voltage direct-hanging type energy storage system with high short-circuit current endurance capability

Abstract

The invention discloses a high-voltage direct-hanging type energy storage system with high short-circuit current endurance capability. The high-voltage direct-hanging type energy storage system is characterized in that a three-phase cascaded H-bridge type high-voltage direct-hanging type energy storage system body is connected to a high-voltage power grid; each phase body of the system is formed by cascading a plurality of power units and is used for generating alternating current high voltage; the power unit is composed of a battery cluster, a short-circuit protection circuit, a control circuit, a step-down current suppression circuit and a full-bridge inverter circuit, and the short-circuit protection circuit comprises a pre-charging device, a first circuit breaker and a second circuit breaker and is used for rapidly cutting off a loop when a fault occurs; the step-down current suppression circuit is used for reducing and outputting the direct-current voltage of the battery cluster at the early stage of a short-circuit fault to effectively suppress rise of short-circuit current; the control circuit collects electric reactor current and capacitor voltage signals and jointly controls the step-down circuit and the inverter to operate. And the full-bridge inverter circuit converts the direct-current voltage into alternating current and outputs the alternating current. According to the invention, by integrating current suppression and protection functions, the short-circuit current endurance capability of the system is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of power electronics and energy storage system research technology, and in particular to a high-voltage direct-connected energy storage system with high short-circuit current withstand capability. Background Technology

[0002] With the continued advancement of the "dual-carbon" strategy, the power system is undergoing a transformation from a traditional centralized power supply structure dominated by fossil fuels to a new type of power system characterized by distributed generation centered on new energy sources. The intermittent and fluctuating nature of new energy power generation methods such as photovoltaic and wind power places higher demands on grid regulation capabilities. Against this backdrop, grid-connected energy storage converters, with their ability to actively support grid voltage and frequency, have become key supporting equipment in the new power system.

[0003] However, in high-power energy storage system applications, high-voltage direct-connected grid-type energy storage converters face extreme operating challenges under grid short-circuit faults. Specifically, when a grid short-circuit fault occurs, the converter output current rises sharply in a very short time, forming an inrush short-circuit current that poses a serious threat to power devices and their drive systems. Although overcurrent protection units have been deployed in traditional systems, such protection typically relies on detection response and hardware delays, making it difficult to meet the current suppression requirements at the millisecond or even microsecond level. Especially in high-voltage direct-connected scenarios with extremely fast current ramp-up rates, existing protection strategies often fail to promptly block or mitigate the short-circuit current surge, leading to power module burnout or system collapse.

[0004] Against this backdrop, there is an urgent need for a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, especially one that effectively limits and mitigates short-circuit current at the circuit physical level, starting from the power module topology itself. This design concept differs from traditional methods that rely on downstream protection; instead, it introduces suppression mechanisms in the front-end power path, comprehensively designing aspects such as circuit response speed, device stress relief, and energy transfer path control. In particular, by leveraging the characteristics of DC-DC converter technology, the system's short-circuit withstand capability is significantly improved through module-level voltage and current regulation.

[0005] In summary, current technology lacks a power module topology for energy storage converters capable of actively suppressing short-circuit inrush currents in high-voltage direct-connection scenarios. Therefore, there is an urgent need to propose a novel power topology that can achieve current suppression or soft current limiting in the early stages of a short-circuit fault, thereby improving the safety and reliability of high-voltage energy storage systems. Summary of the Invention

[0006] In view of the aforementioned existing problems, the present invention is proposed.

[0007] Therefore, this invention provides a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, which solves the problems of poor safety and lagging protection mechanism of existing high-voltage direct-connected energy storage systems under high short-circuit current conditions. This system has higher safety, faster fault response speed and better system adjustability, and is suitable for high-power energy storage grid-type converter applications.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] This invention provides a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, comprising:

[0010] The three-phase cascaded H-bridge type high-voltage direct-connected energy storage system is connected to the high-voltage power grid.

[0011] Each phase of the three-phase cascaded H-bridge high-voltage direct-connected energy storage system is composed of several cascaded power units used to generate AC high voltage.

[0012] The power unit consists of a battery cluster, a short-circuit protection circuit, a control circuit, a buck current suppression circuit, and a full-bridge inverter circuit, and is used to achieve the function of quickly suppressing short-circuit current.

[0013] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the short-circuit protection circuit includes a pre-charging device, a first circuit breaker, and a second circuit breaker.

[0014] The first circuit breaker and the second circuit breaker are used to quickly isolate the faulty circuit when a short circuit fault occurs; the pre-charging device is used for capacitor pre-charging operation during system startup to avoid current surges and power losses.

[0015] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the step-down current suppression circuit consists of a high-frequency switching transistor, a diode, a reactor, and a capacitor. It is used to actively convert the DC voltage output by the battery cluster into a target voltage and to realize the short-circuit current suppression function according to the control algorithm. The reactor is used to suppress the sudden change of current through its own inductive characteristics and is also reused as the main energy storage element of the step-down current suppression circuit.

[0016] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the full-bridge inverter circuit consists of a first power frequency switch, a second power frequency switch, a third power frequency switch, and a fourth power frequency switch, used to convert the output target voltage of the buck current suppression circuit into an AC output voltage.

[0017] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the control circuit detects the current signal in the reactor and the voltage signal across the capacitor, and generates a modulation signal according to a preset control algorithm to control the operation of the buck current suppression circuit and the full-bridge inverter circuit.

[0018] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the specific connection of the power unit includes:

[0019] The positive terminal of the battery cluster is connected to the first terminal of the short-circuit protection circuit; the negative terminal of the battery cluster is connected to the second terminal of the short-circuit protection circuit; the third terminal of the short-circuit protection circuit is connected to the first terminal of the buck current suppression circuit; the fourth terminal of the short-circuit protection circuit is connected to the second terminal of the buck current suppression circuit; the third terminal of the buck current suppression circuit is connected to the first terminal of the full-bridge inverter circuit; the fourth terminal of the buck current suppression circuit is connected to the second terminal of the full-bridge inverter circuit; the fifth terminal of the buck current suppression circuit is connected to the first terminal of the control circuit; the fifth terminal of the full-bridge inverter circuit is connected to the second terminal of the control circuit; the third terminal of the full-bridge inverter circuit serves as the positive output terminal of the power unit; the fourth terminal of the full-bridge inverter circuit serves as the negative output terminal of the power unit.

[0020] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the specific connection of the short-circuit protection circuit includes:

[0021] One end of the first circuit breaker serves as the first terminal of the short-circuit protection circuit; one end of the second circuit breaker serves as the second terminal of the short-circuit protection circuit; the other end of the first circuit breaker serves as the third terminal of the short-circuit protection circuit; the other end of the second circuit breaker is connected to one end of the pre-charging device; and the other end of the pre-charging device serves as the fourth terminal of the short-circuit protection circuit.

[0022] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the specific connection of the step-down current suppression circuit includes:

[0023] The drain of the high-frequency switching transistor serves as the first terminal of the buck current suppression circuit. The drain of the high-frequency switching transistor is connected to the cathode of the diode and one end of the reactor. The anode of the diode is connected to the negative terminal of the capacitor, serving as both the second and fourth terminals of the buck current suppression circuit. The other end of the reactor is connected to the positive terminal of the capacitor, serving as the third terminal of the buck current suppression circuit. The gate of the high-frequency switching transistor, the reactor current, and the capacitor voltage serve as the fifth terminal of the buck current suppression circuit, but they are not connected and operate independently without interference.

[0024] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the specific connection of the full-bridge inverter circuit includes:

[0025] The drains of the first and second power frequency switching transistors are connected, forming the first terminal of the full-bridge inverter; the source of the first power frequency switching transistor is connected to the drain of the third power frequency switching transistor, forming the third terminal of the full-bridge inverter; the source of the second power frequency switching transistor is connected to the drain of the fourth power frequency switching transistor, forming the fourth terminal of the full-bridge inverter; the sources of the third and fourth power frequency switching transistors are connected, forming the second terminal of the full-bridge inverter; the gates of the power frequency switching transistors serve as the fifth terminal of the full-bridge inverter circuit, but are not connected and are independent and do not interfere with each other.

[0026] As a preferred embodiment of the high short-circuit current withstand capability high-voltage direct-connected energy storage system described in this invention, the specific connection of the control circuit includes:

[0027] The control signal terminal of the control circuit is connected to the gate of the switching transistor of the buck current suppression circuit and the full-bridge inverter circuit; the sampling signal terminal of the control circuit is the reactor current and the voltage across the capacitor of the buck current suppression circuit.

[0028] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a high-voltage direct-connected energy storage system with high short-circuit current withstand capability. By configuring battery clusters, short-circuit protection circuits, control circuits, buck current suppression circuits, and full-bridge inverter circuits in each power unit, it not only improves the system's short-circuit current withstand capability but also enhances the system's stability under different operating conditions. Through rapid control and coordinated protection by the control circuit, the safety and reliability of the system during high-voltage grid construction are ensured. Furthermore, the modular design of the power units facilitates system expansion and is suitable for high-voltage direct-connected scenarios of various voltage levels, possessing good engineering adaptability. The high-voltage direct-connected energy storage system provided by this invention, through structural integration and functional synergy, improves the operating performance and protection capabilities under high-power, high-voltage conditions, and has broad engineering application value and promotion prospects. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a system structure diagram of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability according to an embodiment of the present invention.

[0031] Figure 2 This is a power unit structure diagram of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention.

[0032] Figure 3 This is a charging mode diagram of the step-down current suppression circuit section of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention.

[0033] Figure 4 This is a discharge mode diagram of the step-down current suppression circuit section of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention.

[0034] Figure 5 This is a positive-level mode diagram of the full-bridge inverter circuit section of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention.

[0035] Figure 6 This is a zero-level mode diagram of the full-bridge inverter circuit section of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention.

[0036] Figure 7 This is a negative-level mode diagram of the full-bridge inverter circuit section of a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention.

[0037] Figure 8 This is a short-circuit protection control waveform diagram of two power units cascaded in a high-voltage direct-connected energy storage system with high short-circuit current withstand capability, as described in an embodiment of the present invention. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0039] Example 1, referring to Figures 1-8 As one embodiment of the present invention, a high-voltage direct-connected energy storage system with high short-circuit current withstand capability is provided, specifically including:

[0040] The three-phase cascaded H-bridge type high-voltage direct-connected energy storage system is connected to the high-voltage power grid.

[0041] Each phase of the three-phase cascaded H-bridge high-voltage direct-connected energy storage system consists of several cascaded power units used to generate AC high voltage.

[0042] The power unit consists of a battery cluster, a short-circuit protection circuit, a control circuit, a buck current suppression circuit, and a full-bridge inverter circuit, and is used to achieve the function of quickly suppressing short-circuit current.

[0043] Specifically, such as Figure 1 The system shown is connected to phases B and C via a filter inductor through an interface connected to the high-voltage power grid. The positive output terminal of power unit 1 is connected to one end of the filter inductor, and the other end of the filter inductor is connected to phase A of the high-voltage power grid. The negative output terminal of power unit 1 is connected to the positive output terminal of power unit 2. Multiple power units 1 to n are cascaded in sequence. Finally, the output of the power unit is connected to phases B and C. The high-voltage AC signal is formed through the coordinated operation of all units.

[0044] Specifically, within power unit 1, the positive terminal of the battery cluster is connected to the first terminal of the short-circuit protection circuit; the negative terminal of the battery cluster is connected to the second terminal of the short-circuit protection circuit; the third terminal of the short-circuit protection circuit is connected to the first terminal of the buck current suppression circuit; the fourth terminal of the short-circuit protection circuit is connected to the second terminal of the buck current suppression circuit; the third terminal of the buck current suppression circuit is connected to the first terminal of the full-bridge inverter circuit; the fourth terminal of the buck current suppression circuit is connected to the second terminal of the full-bridge inverter circuit; the fifth terminal of the buck current suppression circuit is connected to the first terminal of the control circuit; the fifth terminal of the full-bridge inverter circuit is connected to the second terminal of the control circuit; the third terminal of the full-bridge inverter circuit serves as the positive output terminal of the power unit; and the fourth terminal of the full-bridge inverter circuit serves as the negative output terminal of the power unit.

[0045] In the embodiments of this application, such as Figure 2 The diagram shown is a power unit structure diagram. The power unit consists of a battery cluster, a short-circuit protection circuit, a control circuit, a buck current suppression circuit, and a full-bridge inverter circuit.

[0046] In this embodiment, the short-circuit protection circuit is used to cut off the power supply circuit in time after a short-circuit fault is detected and to prevent excessive charging current during startup. It includes a first circuit breaker CB1, a second circuit breaker CB2, and a pre-charging device.

[0047] The first circuit breaker CB1 and the second circuit breaker CB2 are used to quickly isolate the faulty circuit when a short-circuit fault occurs; the pre-charging device is used for capacitor pre-charging during system startup to avoid current surges and power losses.

[0048] Specifically, the short-circuit protection circuit is connected as follows: one end of the first circuit breaker CB1 serves as the first terminal of the short-circuit protection circuit; one end of the second circuit breaker CB2 serves as the second terminal of the short-circuit protection circuit; the other end of the first circuit breaker CB1 serves as the third terminal of the short-circuit protection circuit; the other end of the second circuit breaker CB2 is connected to one end of the pre-charging device; and the other end of the pre-charging device serves as the fourth terminal of the short-circuit protection circuit.

[0049] In this embodiment, the step-down current suppression circuit consists of a high-frequency switch S, a diode D, an inductor L, and a capacitor C. It is used to actively convert the DC voltage output by the battery cluster into the target voltage and to realize the short-circuit current suppression function according to the control algorithm.

[0050] Among them, the reactor L is used to suppress sudden current changes through its own inductive characteristics, and is also reused as the main energy storage element in the buck current suppression circuit. The capacitor C is used to regulate the output DC bus voltage V. bus It acts as a filter to remove noise and ensure stable output voltage.

[0051] Specifically, the connection of the buck current suppression circuit includes: the drain of the high-frequency switch S serves as the first terminal of the buck current suppression circuit; the drain of the high-frequency switch S is connected to the cathode of the diode D and one end of the reactor L; the anode of the diode D is connected to the cathode of the capacitor C, serving as both the second and fourth terminals of the buck current suppression circuit; the other end of the reactor L is connected to the anode of the capacitor C, serving as the third terminal of the buck current suppression circuit; the gate of the high-frequency switch S and the reactor current i... L and capacitor voltage v C It serves as the fifth terminal of the step-down current suppression circuit, but it is not connected to any other terminal and they operate independently without interference.

[0052] In this embodiment, the full-bridge inverter circuit consists of a first power frequency switch Q1, a second power frequency switch Q2, a third power frequency switch Q3, and a fourth power frequency switch Q4, used to convert the DC bus voltage V of the buck current suppression circuit. bus It is converted into AC output voltage.

[0053] Specifically, the full-bridge inverter circuit is connected as follows: the drains of the first power frequency switch Q1 and the second power frequency switch Q2 are connected, forming the first terminal of the full-bridge inverter circuit; the source of the first power frequency switch Q1 and the drain of the third power frequency switch Q3 are connected, forming the third terminal of the full-bridge inverter circuit and serving as the positive output V+ of the power unit; the source of the second power frequency switch Q2 and the drain of the fourth power frequency switch Q4 are connected, forming the fourth terminal of the full-bridge inverter circuit and serving as the negative output V- of the power unit; the output voltage v o The difference between the positive output V+ and the negative output V- is used. The source of the third power frequency switch Q3 and the source of the fourth power frequency switch Q4 are connected to form the second terminal of the full-bridge inverter circuit. The gates of the power frequency switches Q1, Q2, Q3, and Q4 serve as the fifth terminal of the full-bridge inverter circuit, but they are not connected and operate independently without interference.

[0054] In this embodiment, the control circuit detects the current signal in the reactor and the voltage signal across the capacitor, and generates a modulation signal according to a preset control algorithm to control the operation of the buck current suppression circuit and the full-bridge inverter circuit.

[0055] Specifically, the connection of the control circuit includes: the control signal terminal of the control circuit is connected to the gate of the switching transistor of the buck current suppression circuit and the full-bridge inverter circuit; the sampling signal terminal of the control circuit is the reactor current and the voltage across the capacitor of the buck current suppression circuit.

[0056] Specifically, the control circuit is used to collect the reactor current i L and capacitor voltage v C The short-circuit current fault is predicted based on the control algorithm, and a control signal v is generated. S Control the high-frequency switching transistor S, and v Q1 v Q2 v Q3 v Q4 These control the first power frequency switch Q1, the second power frequency switch Q2, the third power frequency switch Q3, and the fourth power frequency switch Q4, respectively. The first terminal signal of the control circuit includes v. S i L and v C The second terminal signal of the control circuit includes v Q1 v Q2 v Q3 v Q4 .

[0057] Specifically, when no short-circuit fault occurs, the high-frequency switching transistor is normally on, and the power frequency switching transistor is turned on in sequence to achieve AC inversion; when a short-circuit fault is detected, the control circuit controls the switching of the high-frequency switching transistor, so that the DC bus voltage V busThis reduces the current and helps to suppress short-circuit current in a timely manner.

[0058] It should be noted that the high-voltage direct-connected energy storage system with high short-circuit current withstand capability provided by the present invention overcomes the technical problems of poor safety and lagging protection mechanism of existing high-voltage direct-connected energy storage systems under high short-circuit current conditions. It has higher safety, faster fault response speed and better system adjustability, and is suitable for high-power energy storage grid-type converter applications.

[0059] Furthermore, such as Figure 3 and Figure 4 The diagram shows two operating modes of the buck current suppression circuit in the power unit. The following is a detailed description of these two operating modes:

[0060] ① Charging mode of the buck current suppression circuit section;

[0061] like Figure 3 As shown, when the high-frequency switch S is turned on, the reactor L and capacitor C of the buck current suppression circuit are charged by the battery cluster through the high-frequency switch S, and the battery cluster also supplies power to the full-bridge inverter circuit; diode D is turned off due to reverse voltage. This mode continues until the high-frequency switch S is turned off.

[0062] ② Discharge modes of the step-down current suppression circuit section;

[0063] like Figure 4 As shown, when the high-frequency switch S is turned off, in the freewheeling mode, diode D conducts, providing a freewheeling path for reactor L. Reactor L and capacitor C simultaneously supply power to the full-bridge inverter circuit. This mode continues until the high-frequency switch S is turned on.

[0064] It should be noted that when the two operating modes of the buck current suppression circuit in the power unit are switched alternately, the high DC voltage of the battery pack can be converted into a lower DC bus voltage output V. bus .

[0065] Furthermore, such as Figure 5 , Figure 6 and Figure 7 The diagram shows the three operating modes of the full-bridge inverter circuit in the power unit. The following is a detailed description of these three operating modes:

[0066] ① Positive level mode of the full-bridge inverter circuit;

[0067] like Figure 5 As shown, when the first power frequency switch Q1 and the fourth power frequency switch Q4 are simultaneously turned on, and the second power frequency switch Q2 and the third power frequency switch Q3 are simultaneously turned on, the bus voltage V busA closed loop is formed by supplying power to the load through Q1 and Q4. At this time, the output of the full-bridge inverter is at a positive level +V. bus .

[0068] ② Zero-level mode of the full-bridge inverter circuit;

[0069] like Figure 6 As shown, when the third power frequency switch Q3 and the fourth power frequency switch Q4 are simultaneously turned on, while the first power frequency switch Q1 and the second power frequency switch Q2 are simultaneously turned off, the bus voltage V bus No power is supplied to the load. At this time, the output of the full-bridge inverter is at zero level (0).

[0070] ③ The negative level mode of the full-bridge inverter circuit;

[0071] like Figure 7 As shown, when the second power frequency switch Q2 and the third power frequency switch Q3 are simultaneously turned on, while the first power frequency switch Q1 and the fourth power frequency switch Q4 are simultaneously turned off, the bus voltage V bus A closed loop is formed by supplying power to the load through Q2 and Q3. At this time, the output of the full-bridge inverter is at a negative level -V. bus .

[0072] It should be noted that when the three operating modes of the full-bridge inverter circuit in the power unit are switched in turn, the DC bus voltage V can be adjusted. bus Convert AC bus voltage to +V bus , 0, -V bus .

[0073] It should be noted that, in the specific implementation process, the control circuit collects the reactor current i L and capacitor voltage v C The gates of the high-frequency switch S, the first power frequency switch Q1, the second power frequency switch Q2, the third power frequency switch Q3, and the fourth power frequency switch Q4 are controlled according to the control algorithm to achieve the above-mentioned functions. Figures 3 to 7 The operating mode is configured to achieve adjustable AC output voltage. Therefore, the power unit provided by this invention detects the reactor current i. L and capacitor voltage v C The system can predict short-circuit faults in a timely manner and output a low AC output to achieve short-circuit current suppression protection. Therefore, this invention has a simple and reliable structure and strong practicality.

[0074] Furthermore, such as Figure 8As shown, under normal operating conditions, the high-frequency switch S in the step-down current suppression circuit is in a normally on state, with a constant duty cycle d of 1. When the load current suddenly increases and approaches a short-circuit state, the control circuit promptly activates to limit the current after detecting a 40A overcurrent through the sampling circuit. It can be seen that the control circuit reduces the output voltage and gradually limits the current back to around 10A by controlling the duty cycle d of the high-frequency switch S to 0.11, thus verifying the feasibility of the system provided in this embodiment.

[0075] Therefore, this invention provides a high-voltage direct-connected energy storage system with high short-circuit current withstand capability. By configuring battery clusters, short-circuit protection circuits, control circuits, buck current suppression circuits, and full-bridge inverter circuits in each power unit, it not only improves the system's short-circuit current withstand capability but also enhances the system's stability under different operating conditions. Through rapid control and coordinated protection by the control circuit, the safety and reliability of the system during high-voltage grid construction are ensured. Furthermore, the modular design of the power units facilitates system expansion and is suitable for high-voltage direct-connected scenarios of various voltage levels, exhibiting good engineering adaptability. The high-voltage direct-connected energy storage system provided by this invention, through structural integration and functional synergy, improves the operating performance and protection capabilities under high-power, high-voltage conditions, possessing broad engineering application value and promising prospects for widespread adoption.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability, characterized in that, include: The three-phase cascaded H-bridge type high-voltage direct-connected energy storage system is connected to the high-voltage power grid. Each phase of the three-phase cascaded H-bridge high-voltage direct-connected energy storage system is composed of several cascaded power units used to generate AC high voltage. The power unit consists of a battery cluster, a short-circuit protection circuit, a control circuit, a buck current suppression circuit, and a full-bridge inverter circuit, and is used to achieve the function of quickly suppressing short-circuit current.

2. The high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 1, characterized in that, The short-circuit protection circuit includes a pre-charging device, a first circuit breaker, and a second circuit breaker. The first circuit breaker and the second circuit breaker are used to quickly isolate the faulty circuit when a short circuit fault occurs; the pre-charging device is used for capacitor pre-charging operation during system startup to avoid current surges and power losses.

3. The high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 1, characterized in that, The buck current suppression circuit consists of a high-frequency switch, a diode, a reactor, and a capacitor. It is used to actively convert the DC voltage output by the battery cluster into a target voltage and to realize the short-circuit current suppression function according to the control algorithm. The reactor is used to suppress the sudden change of current through its own inductance characteristics, and is also reused as the main energy storage element of the buck current suppression circuit.

4. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 1, characterized in that, The full-bridge inverter circuit consists of a first power frequency switch, a second power frequency switch, a third power frequency switch, and a fourth power frequency switch, and is used to convert the output target voltage of the buck current suppression circuit into an AC output voltage.

5. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 1, characterized in that, The control circuit detects the current signal in the reactor and the voltage signal across the capacitor, and generates a modulation signal according to a preset control algorithm to control the operation of the buck current suppression circuit and the full-bridge inverter circuit.

6. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 1, characterized in that, The specific connections of the power unit include: The positive terminal of the battery cluster is connected to the first terminal of the short-circuit protection circuit; the negative terminal of the battery cluster is connected to the second terminal of the short-circuit protection circuit; the third terminal of the short-circuit protection circuit is connected to the first terminal of the buck current suppression circuit; the fourth terminal of the short-circuit protection circuit is connected to the second terminal of the buck current suppression circuit; the third terminal of the buck current suppression circuit is connected to the first terminal of the full-bridge inverter circuit; the fourth terminal of the buck current suppression circuit is connected to the second terminal of the full-bridge inverter circuit; the fifth terminal of the buck current suppression circuit is connected to the first terminal of the control circuit; the fifth terminal of the full-bridge inverter circuit is connected to the second terminal of the control circuit; the third terminal of the full-bridge inverter circuit serves as the positive output terminal of the power unit; the fourth terminal of the full-bridge inverter circuit serves as the negative output terminal of the power unit.

7. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 6, characterized in that, The specific connection of the short-circuit protection circuit includes: One end of the first circuit breaker serves as the first terminal of the short-circuit protection circuit; one end of the second circuit breaker serves as the second terminal of the short-circuit protection circuit; the other end of the first circuit breaker serves as the third terminal of the short-circuit protection circuit; the other end of the second circuit breaker is connected to one end of the pre-charging device; and the other end of the pre-charging device serves as the fourth terminal of the short-circuit protection circuit.

8. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 6, characterized in that, The specific connection of the buck current suppression circuit includes: The drain of the high-frequency switching transistor serves as the first terminal of the buck current suppression circuit. The drain of the high-frequency switching transistor is connected to the cathode of the diode and one end of the reactor. The anode of the diode is connected to the negative terminal of the capacitor, serving as both the second and fourth terminals of the buck current suppression circuit. The other end of the reactor is connected to the positive terminal of the capacitor, serving as the third terminal of the buck current suppression circuit. The gate of the high-frequency switching transistor, the reactor current, and the capacitor voltage serve as the fifth terminal of the buck current suppression circuit, but they are not connected and operate independently without interference.

9. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 6, characterized in that, The specific connections of the full-bridge inverter circuit include: The drains of the first and second power frequency switching transistors are connected, forming the first terminal of the full-bridge inverter; the source of the first power frequency switching transistor is connected to the drain of the third power frequency switching transistor, forming the third terminal of the full-bridge inverter; the source of the second power frequency switching transistor is connected to the drain of the fourth power frequency switching transistor, forming the fourth terminal of the full-bridge inverter; the sources of the third and fourth power frequency switching transistors are connected, forming the second terminal of the full-bridge inverter; the gates of the power frequency switching transistors serve as the fifth terminal of the full-bridge inverter circuit, but are not connected and are independent and do not interfere with each other.

10. A high-voltage direct-connected energy storage system with high short-circuit current withstand capability as described in claim 6, characterized in that, The specific connections of the control circuit include: The control signal terminal of the control circuit is connected to the gate of the switching transistor of the buck current suppression circuit and the full-bridge inverter circuit; the sampling signal terminal of the control circuit is the reactor current and the voltage across the capacitor of the buck current suppression circuit.

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