Battery energy storage system and direct current side fault detection method of battery energy storage system

Abstract

The invention relates to the technical field of battery energy storage systems, and discloses a battery energy storage system and a direct current side fault detection method of the battery energy storage system, and the system comprises a battery pack, a circuit breaker group, an energy storage converter, a transformer, a power grid impedance, a lightning current generator and a power grid. The battery pack, the energy storage converter, the transformer, the power grid impedor and the power grid are sequentially connected, the output end of the battery pack is further connected with the circuit breaker set, the output end of the transformer is further connected with the lightning current generator, and the circuit breaker set comprises a first circuit breaker, a second circuit breaker and a third circuit breaker. The cathode output end of the battery pack is grounded through the second circuit breaker, the anode output end of the battery pack is further connected to the cathode output end of the battery pack through the third circuit breaker, and the circuit breaker group is used for simulating faults of the battery energy storage system. Therefore, fault simulation of the battery energy storage system is realized.

Description

Technical Field

[0001] This application relates to the technical field of battery energy storage systems, and particularly to a battery energy storage system and a method for detecting DC-side faults in a battery energy storage system. Background Art

[0002] The energy storage system of lithium-ion batteries is a complex system integrating battery packs, battery management systems, energy management systems, energy storage converters, and other electrical equipment. The lithium-ion battery energy storage system uses lithium batteries as energy storage carriers, can store excess power during periods of low demand, and release power during peak demand, and has wide applications in power stations, communication base stations, data rooms and other fields. The core principle of battery energy storage is to convert electrical energy into chemical energy and then convert it back into electrical energy when needed.

[0003] Lithium-ion batteries are extremely prone to thermal runaway under internal and external fault conditions, generating a large amount of heat and combustible and explosive gases, posing a great safety hazard. How to safely and effectively detect the DC-side short-circuit fault of a battery energy storage system has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the embodiments of this application is to provide a battery energy storage system and a method for detecting DC-side faults in a battery energy storage system to solve the problem in the prior art that the DC-side short-circuit fault of a battery energy storage system cannot be safely and effectively detected.

[0005] To achieve the above purpose, in the first aspect of this application, a battery energy storage system is provided. The system includes: a battery pack, a circuit breaker group, an energy storage converter, a transformer, a grid impedance, a lightning current generator, and a grid. The battery pack, the energy storage converter, the transformer, the grid impedance, and the grid are connected in sequence. The output end of the battery pack is also connected to the circuit breaker group, and the output end of the transformer is also connected to the lightning current generator. The circuit breaker group includes a first circuit breaker, a second circuit breaker, and a third circuit breaker. The positive output end of the battery pack is grounded through the first circuit breaker, the negative output end of the battery pack is grounded through the second circuit breaker, and the positive output end of the battery pack is also connected to the negative output end of the battery pack through the third circuit breaker. The circuit breaker group is used to simulate faults in the battery energy storage system.

[0006] In the embodiment of the present application, the battery pack includes a Thevenin equivalent module, a grounding module, a cable module, and a measurement module. The Thevenin equivalent module is used to simulate the equivalent internal resistance and equivalent voltage of the battery pack. The grounding module is used to simulate the grounding resistance and grounding capacitance between the outer shell of the energy storage cabin and the battery pack. The cable module is used to simulate the resistance, capacitance, and inductance of the wires in the energy storage cabin. The measurement module is used to measure the current of the battery pack, the voltage between the positive and negative electrodes of the battery pack, the voltage of the negative electrode of the battery pack with respect to the ground, and the voltage of the positive electrode of the battery pack with respect to the ground. The first end of the Thevenin equivalent module is connected to the first end of the grounding module, and the second end of the Thevenin equivalent module is connected to the second end of the grounding module. The third end of the grounding module is connected to the first end of the cable module, and the fourth end of the grounding module is connected to the second end of the cable module. The third end of the cable module is connected to the first end of the measurement module, and the fourth end of the cable module is connected to the second end of the measurement module.

[0007] In the embodiment of the present application, the Thevenin equivalent module includes a first Thevenin equivalent voltage source, a second Thevenin equivalent voltage source, a first Thevenin equivalent internal resistance, and a second Thevenin equivalent internal resistance. The positive electrode of the first Thevenin equivalent voltage source is connected to one end of the first Thevenin equivalent internal resistance. The negative electrode of the first Thevenin equivalent voltage source is connected to the positive electrode of the second Thevenin equivalent voltage source. The negative electrode of the second Thevenin equivalent voltage source is connected to one end of the second Thevenin equivalent internal resistance. The other end of the second Thevenin equivalent internal resistance serves as the first end of the Thevenin equivalent module, and the other end of the first Thevenin equivalent internal resistance serves as the second end of the Thevenin equivalent module.

[0008] In the embodiment of the present application, the grounding module includes a first positive and negative bus capacitance to ground, a second positive and negative bus capacitance to ground, and a grounding resistance. The positive electrode of the first positive and negative bus capacitance to ground is connected to the second end of the Thevenin equivalent module. The positive electrode of the second positive and negative bus capacitance to ground is connected to the first end of the Thevenin equivalent module. The negative electrodes of the first positive and negative bus capacitance to ground and the second positive and negative bus capacitance to ground are connected and grounded. The positive electrode of the second positive and negative bus capacitance to ground is further connected to one end of the grounding resistance. The positive electrode of the second positive and negative bus capacitance to ground serves as the first end of the grounding module, one end of the grounding resistance serves as the third end of the grounding module, and the positive electrode of the first positive and negative bus capacitance to ground serves as the second end and the fourth end of the grounding module.

[0009] In an embodiment of the present application, the cable module includes a first cable equivalent resistance, a second cable equivalent resistance, a first cable equivalent inductance, a second cable equivalent inductance, a first cable equivalent capacitance, and a second cable equivalent capacitance. The positive electrode of the first cable equivalent capacitance is connected to the fourth terminal of the grounding module, and the negative electrode of the first cable equivalent capacitance is connected to the third terminal of the grounding module. The positive electrode of the first cable equivalent capacitance is further sequentially connected to the first cable equivalent resistance and one end of the first cable equivalent inductance. The negative electrode of the first cable equivalent capacitance is further sequentially connected to the second cable equivalent resistance and one end of the second cable equivalent inductance. The other end of the second cable equivalent inductance is connected to the negative electrode of the second cable equivalent capacitance, and the other end of the first cable equivalent inductance is connected to the positive electrode of the second cable equivalent capacitance. The connection point between the negative electrode of the first cable equivalent capacitance and the second cable equivalent resistance is used as the first terminal of the cable module. The connection point between the positive electrode of the first cable equivalent capacitance and the first cable equivalent resistance is used as the second terminal of the cable module. The connection point between the negative electrode of the second cable equivalent capacitance and the other end of the second cable equivalent inductance is used as the third terminal of the cable module. The connection point between the positive electrode of the second cable equivalent capacitance and the other end of the first cable equivalent inductance is used as the fourth terminal of the cable module.

[0010] In an embodiment of the present application, the energy storage converter includes a DC-side internal resistance, a DC-side capacitor, an inverter, a filter inductor, and a filter capacitor. The negative electrode of the DC-side capacitor is connected to the negative output terminal of the battery pack. The negative electrode of the DC-side filter capacitor is further connected to the negative electrode of the inverter. The positive electrode of the DC-side capacitor is connected to the positive electrode of the inverter through the DC-side internal resistance. The DC-side internal resistance is further connected to the positive output terminal of the battery pack. The output terminal of the inverter is sequentially connected to the filter inductor and the filter capacitor.

[0011] A second aspect of the present application provides a method for detecting a DC-side fault of a battery energy storage system. The method is implemented based on the battery energy storage system as described above. The method includes:

[0012] Controlling the circuit breaker group to simulate a DC-side fault of the battery energy storage system, where the DC side of the battery energy storage system is the output terminal of the battery pack;

[0013] Obtaining the working state of the battery pack and the grounding state of the transformer, where the working state of the battery pack includes charging and discharging, and the grounding state of the transformer includes grounded and ungrounded;

[0014] Based on the working state of the battery pack and the grounding state of the transformer, determining the type of the DC-side fault of the battery energy storage system.

[0015] In an embodiment of the present application, based on the working state of the battery pack and the grounding state of the transformer, determining the type of the DC-side fault of the battery energy storage system includes:

[0016] When the operating state of the battery pack is charging or discharging and the transformer is not grounded, determine that the battery pack has a polar fault or a short - circuit fault between the positive and negative poles of the battery pack;

[0017] When the operating state of the battery pack is charging or discharging and the transformer is grounded, determine that the battery pack has a polar fault or a short - circuit fault between the positive and negative poles of the battery pack.

[0018] In the embodiment of the present application, the method further includes:

[0019] Obtain the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground;

[0020] Based on the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground, determine the type of DC - side fault of the battery energy storage system.

[0021] In the embodiment of the present application, based on the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground, determining the type of DC - side fault of the battery energy storage system includes:

[0022] When the transformer is not grounded, when the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground both drop to the first preset threshold and the current of the battery pack remains stable, determine that the battery pack has a polar fault;

[0023] When the transformer is not grounded, when the voltage between the positive and negative poles of the battery pack drops to the second preset threshold and the current of the battery pack rises to the third preset threshold, determine that the battery pack has a short - circuit fault between the positive and negative poles;

[0024] When the transformer is grounded, when the voltage between the positive and negative poles of the battery pack fluctuates and drops to the fourth threshold, the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground instantaneously rise to the fifth preset threshold, and the current of the battery pack instantaneously rises to the sixth preset threshold, determine that the battery pack has a polar fault;

[0025] When the transformer is grounded, when the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground drop to the seventh preset threshold and no voltage greater than the eighth preset threshold is generated, determine that the battery pack has a short - circuit fault between the positive and negative poles.

[0026] Through the above technical solutions, the fault simulation of the battery energy storage system is realized, and the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground are analyzed to detect the type of DC - side fault of the battery energy storage system.

[0027] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation part. Description of the Drawings

[0028] The drawings are used to provide a further understanding of the embodiments of the present application, and constitute a part of the specification. Together with the following specific implementation, they are used to explain the embodiments of the present application, but do not constitute a limitation to the embodiments of the present application. In the drawings:

[0029] Figure 1 Schematically shows a structural diagram of a battery energy storage system according to an embodiment of the present application;

[0030] Figure 2 Schematically shows a structural diagram of a battery pack according to an embodiment of the present application;

[0031] Figure 3 Schematically shows a structural diagram of an energy storage converter according to an embodiment of the present application;

[0032] Figure 4 Schematically shows a flowchart of a method for detecting a DC-side fault of a battery energy storage system according to an embodiment of the present application;

[0033] Figure 5 Schematically shows a first schematic diagram of the voltage waveform between the positive and negative electrodes of a battery pack according to an embodiment of the present application;

[0034] Figure 6 Schematically shows a first schematic diagram of the current waveform of a battery pack according to an embodiment of the present application;

[0035] Figure 7 Schematically shows a first schematic diagram of the voltage waveform of the positive electrode of a battery pack with respect to ground according to an embodiment of the present application;

[0036] Figure 8 Schematically shows a first schematic diagram of the voltage waveform of the negative electrode of a battery pack with respect to ground according to an embodiment of the present application;

[0037] Figure 9 Schematically shows a second schematic diagram of the voltage waveform between the positive and negative electrodes of a battery pack according to an embodiment of the present application;

[0038] Figure 10 Schematically shows a second schematic diagram of the current waveform of a battery pack according to an embodiment of the present application;

[0039] Figure 11 Schematically shows a second schematic diagram of the voltage waveform of the positive electrode of a battery pack with respect to ground according to an embodiment of the present application;

[0040] Figure 12The second schematic diagram schematically shows the negative electrode to ground voltage waveform of the battery pack according to an embodiment of the present application;

[0041] Figure 13 The third schematic diagram schematically shows the voltage waveform between the positive electrode and the negative electrode of the battery pack according to an embodiment of the present application;

[0042] Figure 14 The third schematic diagram schematically shows the current waveform of the battery pack according to an embodiment of the present application;

[0043] Figure 15 The third schematic diagram schematically shows the positive electrode to ground voltage waveform of the battery pack according to an embodiment of the present application;

[0044] Figure 16 The third schematic diagram schematically shows the negative electrode to ground voltage waveform of the battery pack according to an embodiment of the present application;

[0045] Figure 17 The fourth schematic diagram schematically shows the voltage waveform between the positive electrode and the negative electrode of the battery pack according to an embodiment of the present application;

[0046] Figure 18 The fourth schematic diagram schematically shows the current waveform of the battery pack according to an embodiment of the present application;

[0047] Figure 19 The fourth schematic diagram schematically shows the positive electrode to ground voltage waveform of the battery pack according to an embodiment of the present application;

[0048] Figure 20 The fourth schematic diagram schematically shows the negative electrode to ground voltage waveform of the battery pack according to an embodiment of the present application. Detailed implementation manners

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. It should be understood that the specific implementation manners described herein are only for explaining and illustrating the embodiments of the present application, and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0050] It should be noted that the acquisition, transmission, storage, use, processing, etc. of data in the technical solutions of the present application all comply with the relevant regulations of national laws and regulations. In the embodiments of the present application, certain industry-existing solutions such as software, components, models, etc. may be mentioned. They should be regarded as exemplary, and their purpose is only to illustrate the feasibility in the implementation of the technical solutions of the present application, but it does not mean that the applicant has already or necessarily used this solution.

[0051] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of this application, then such directional indications are only used to explain the relative positional relationship, movement conditions, etc. between components in a certain specific posture (as shown in the drawings). If this specific posture changes, then the directional indications will also change accordingly.

[0052] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of this application, then such descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0053] Figure 1 Schematically shows a structural schematic diagram of a battery energy storage system according to an embodiment of the present application. As Figure 1 shown, the embodiments of the present application provide a battery energy storage system, which includes: a battery pack, a circuit breaker group, an energy storage converter, a transformer, a grid impedance, a lightning current generator, and a grid. The battery pack, the energy storage converter, the transformer, the grid impedance, and the grid are connected in sequence. The output terminal of the battery pack is also connected to the circuit breaker group, and the output terminal of the transformer is also connected to the lightning current generator. The circuit breaker group includes a first circuit breaker, a second circuit breaker, and a third circuit breaker. The positive output terminal of the battery pack is grounded through the first circuit breaker, the negative output terminal of the battery pack is grounded through the second circuit breaker, and the positive output terminal of the battery pack is also connected to the negative output terminal of the battery pack through the third circuit breaker. The circuit breaker group is used to simulate the faults of the battery energy storage system.

[0054] The positive output terminal of the Battery Pack is connected to the positive input terminal of the Power Conversion System (PCS), and the negative output terminal of the Battery Pack is connected to the negative input terminal of the PCS. The output Phase A of the PCS is connected to the input Phase A of the transformer, the output Phase B of the PCS is connected to the input Phase B of the transformer, and the output Phase C of the PCS is connected to the input Phase C of the transformer. The output Phase a of the transformer is connected to the input Phase A of the grid impedance (Zg), the output Phase b of the transformer is connected to the input Phase B of the grid impedance (Zg), and the output Phase c of the transformer is connected to the input Phase C of the grid impedance (Zg). The output Phase a of the transformer is also connected to the input Phase A of the lightning current generator, the output Phase b of the transformer is also connected to the input Phase B of the lightning current generator, and the output Phase c of the transformer is also connected to the input Phase C of the lightning current generator. The output Phase a of the grid impedance (Zg) is connected to the input Phase A of the Grid, the output Phase b of the grid impedance (Zg) is connected to the input Phase B of the Grid, and the output Phase c of the grid impedance (Zg) is connected to the input Phase C of the Grid. The output terminal of the Grid is grounded. Schematically, the grid impedance can be 15.7 mΩ, and the rated voltage of the Grid can be 10 kV.

[0055] In the embodiment of the present application, a battery energy storage system is implemented by building on a simulation software, and by setting a circuit breaker group at the output terminal of the battery pack, the faults on the DC side of the battery energy storage system can be accurately simulated.

[0056] Figure 2 Schematically shows a structural schematic diagram of a battery pack according to an embodiment of the present application. As Figure 2 shown, the embodiment of the present application provides a battery pack. In an embodiment of the present application, the battery pack includes a Thevenin equivalent module, a grounding module, a cable module, and a measurement module. The Thevenin equivalent module is used to simulate the equivalent internal resistance and equivalent voltage of the battery pack. The grounding module is used to simulate the grounding resistance and grounding capacitance between the outer shell of the energy storage cabin and the battery pack. The cable module is used to simulate the resistance, capacitance, and inductance of the wires in the energy storage cabin. The measurement module is used to measure the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground. The first end of the Thevenin equivalent module is connected to the first end of the grounding module, the second end of the Thevenin equivalent module is connected to the second end of the grounding module, the third end of the grounding module is connected to the first end of the cable module, the fourth end of the grounding module is connected to the second end of the cable module, the third end of the cable module is connected to the first end of the measurement module, and the fourth end of the cable module is connected to the second end of the measurement module.

[0057] Among them, the rated voltage between the poles of the battery pack is 1 kV - 5 kV, and the rated charge-discharge power of the battery pack is 100 KW - 300 kW. Preferably, the rated voltage of the battery pack in this embodiment is 1.5 kV, and the rated charge-discharge power of the battery pack is 200 kW.

[0058] In an embodiment of the present application, the Thevenin equivalent module includes a first Thevenin equivalent voltage source, a second Thevenin equivalent voltage source, a first Thevenin equivalent internal resistance, and a second Thevenin equivalent internal resistance. The positive pole of the first Thevenin equivalent voltage source is connected to one end of the first Thevenin equivalent internal resistance. The negative pole of the first Thevenin equivalent voltage source is connected to the positive pole of the second Thevenin equivalent voltage source. The negative pole of the second Thevenin equivalent voltage source is connected to one end of the second Thevenin equivalent internal resistance. The other end of the second Thevenin equivalent internal resistance serves as the first end of the Thevenin equivalent module, and the other end of the first Thevenin equivalent internal resistance serves as the second end of the Thevenin equivalent module.

[0059] Among them, the Thevenin equivalent module (Battery Model) includes a first Thevenin equivalent voltage source Vbat1, a second Thevenin equivalent voltage source Vbat2, a first Thevenin equivalent internal resistance Rbat1, and a second Thevenin equivalent internal resistance Rbat2.

[0060] In an embodiment of the present application, the grounding module includes a first positive and negative bus capacitance to ground, a second positive and negative bus capacitance to ground, and a grounding resistance. The positive pole of the first positive and negative bus capacitance to ground is connected to the second end of the Thevenin equivalent module. The positive pole of the second positive and negative bus capacitance to ground is connected to the first end of the Thevenin equivalent module. The negative poles of the first positive and negative bus capacitance to ground and the second positive and negative bus capacitance to ground are connected and grounded. The positive pole of the second positive and negative bus capacitance to ground is further connected to one end of the grounding resistance. The positive pole of the second positive and negative bus capacitance to ground serves as the first end of the grounding module, one end of the grounding resistance serves as the third end of the grounding module, and the positive pole of the first positive and negative bus capacitance to ground serves as the second end and the fourth end of the grounding module.

[0061] Among them, the grounding (Grounding) module includes a first positive and negative bus capacitance to ground Cg1, a second positive and negative bus capacitance to ground Cg2, and a grounding resistance Rg. The capacitance of the positive and negative buses to ground refers to the capacitance formed between the positive and negative buses and the ground due to the electric field effect.

[0062] In one embodiment of the present application, the cable module includes a first cable equivalent resistance, a second cable equivalent resistance, a first cable equivalent inductance, a second cable equivalent inductance, a first cable equivalent capacitance, and a second cable equivalent capacitance. The positive electrode of the first cable equivalent capacitance is connected to the fourth terminal of the grounding module, and the negative electrode of the first cable equivalent capacitance is connected to the third terminal of the grounding module. The positive electrode of the first cable equivalent capacitance is further connected in sequence to the first cable equivalent resistance and one end of the first cable equivalent inductance. The negative electrode of the first cable equivalent capacitance is further connected in sequence to the second cable equivalent resistance and one end of the second cable equivalent inductance. The other end of the second cable equivalent inductance is connected to the negative electrode of the second cable equivalent capacitance, and the other end of the first cable equivalent inductance is connected to the positive electrode of the second cable equivalent capacitance. The connection point between the negative electrode of the first cable equivalent capacitance and the second cable equivalent resistance serves as the first terminal of the cable module. The connection point between the positive electrode of the first cable equivalent capacitance and the first cable equivalent resistance serves as the second terminal of the cable module. The connection point between the negative electrode of the second cable equivalent capacitance and the other end of the second cable equivalent inductance serves as the third terminal of the cable module. The connection point between the positive electrode of the second cable equivalent capacitance and the other end of the first cable equivalent inductance serves as the fourth terminal of the cable module.

[0063] Among them, the cable module includes a first cable equivalent resistance Rcab1, a second cable equivalent resistance Rcab2, a first cable equivalent inductance Lcab1, a second cable equivalent inductance Lcab2, a first cable equivalent capacitance Ccab1, and a second cable equivalent capacitance Ccab2.

[0064] Figure 3 Schematically shows a structural diagram of an energy storage converter according to an embodiment of the present application. An embodiment of the present application provides an energy storage converter. In one embodiment of the present application, the energy storage converter includes a DC-side internal resistance, a DC-side capacitance, an inverter, a filter inductor, and a filter capacitor. The negative electrode of the DC-side capacitance is connected to the negative output terminal of the battery pack, and the negative electrode of the DC-side filter capacitor is further connected to the negative electrode of the inverter. The positive electrode of the DC-side capacitance is connected to the positive electrode of the inverter through the DC-side internal resistance. The DC-side internal resistance is further connected to the positive output terminal of the battery pack. The output terminal of the inverter is connected in sequence to the filter inductor and the filter capacitor.

[0065] Among them, the energy storage converter module is used to simulate the bidirectional power flow in the energy storage power station. The energy storage converter includes a DC-side internal resistance Rdc, a DC-side capacitor Cdc, an inverter, a filter inductor Lf, and a filter capacitor Cf. The DC-side capacitor Cdc of the energy storage converter is composed of several dry-type DC filter capacitors connected in series and parallel. The capacitance value of the DC-side capacitor Cdc of the energy storage converter is 2200 - 5000 μF, and the resistance value of the DC-side internal resistance Rdc is 2 - 5 mΩ. Preferably, the capacitance value of the DC-side capacitor Cdc of the energy storage converter in this embodiment is 2200 μF, and the resistance value of the DC-side internal resistance Rdc is 2 mΩ. The DC-side internal resistance Rdc and the DC-side capacitor Cdc are used to smooth the DC voltage and reduce the ripple. The inverter consists of multiple IGBTs to form a rectifier bridge to achieve DC / AC conversion. The transformer is a three-phase double-winding transformer. A phase-locked loop in the synchronous reference coordinate system is used to track the grid voltage, and it operates in the constant active power and constant reactive power modes. The rated capacity of the inverter is 2.5 MVA - 3 MVA, the rated voltage of the primary side is 0.69 kV, the rated voltage of the secondary side is 10 kV, and the per-unit value of the leakage reactance parameter is 0.06 - 0.1. Preferably, the rated capacity of the inverter is 2.5 MVA, and the per-unit value of the leakage reactance parameter is taken as 0.06. In order to meet the requirements of voltage fault ride-through, limiters are added to both the current control inner loop and the phase-locked loop of the inverter. The filter inductor Lf is used as the output filter inductor to limit the current ripple and smooth the output AC current. The filter inductor Lf and the filter capacitor Cf form an LC filter current to achieve harmonic filtering of the AC current and voltage. Idc represents the DC-side output current measurement point, which is used to monitor the DC-side output current in real time. Vdc represents the DC-side voltage measurement point, which is used to monitor the DC-side voltage in real time. g represents the PWM drive signal of the IGBT, vCabc represents the capacitor-side voltage, iLabc represents the AC-side inductor current, and igbabc represents the AC-side grid-connected current.

[0066] Figure 4 Schematically shows a flowchart of a method for detecting DC-side faults in a battery energy storage system according to an embodiment of the present application. As Figure 4 shown, an embodiment of the present application also provides a method for detecting DC-side faults in a battery energy storage system. The method is implemented based on the above battery energy storage system, and the method may include the following steps.

[0067] Step S410: Control the breaker group to simulate a DC-side fault of the battery energy storage system, where the DC side of the battery energy storage system is the output end of the battery pack;

[0068] Step S420: Obtain the working state of the battery pack and the grounding state of the transformer, where the working state of the battery pack includes charging and discharging, and the grounding state of the transformer includes grounded and ungrounded;

[0069] Step S430: Determine the type of DC-side fault of the battery energy storage system based on the operating state of the battery pack and the grounding state of the transformer.

[0070] In step S410, control the opening and closing of the first circuit breaker, the second circuit breaker, or the third circuit breaker to simulate a DC-side fault of the battery energy storage system.

[0071] In step S420, when the operating state of the battery pack is charging, the current value of the battery pack is less than 0, and when the operating state of the battery pack is discharging, the current value of the battery pack is greater than 0.

[0072] In step S430, determine the type of DC-side fault of the battery energy storage system according to the operating state of the battery pack and the grounding state of the transformer.

[0073] In an alternative embodiment, step S430 includes:

[0074] Step S431: When the operating state of the battery pack is charging or discharging and the transformer is not grounded, determine that the battery pack has a polar fault or a short circuit fault between the positive and negative poles of the battery pack;

[0075] Step S432: When the operating state of the battery pack is charging or discharging and the transformer is grounded, determine that the battery pack has a polar fault or a short circuit fault between the positive and negative poles of the battery pack.

[0076] Among them, the charging or discharging of the battery pack is based on the same principle to judge the type of DC-side fault of the battery energy storage system. Under the condition that other conditions are the same, whether the battery pack is charging or discharging, the type of DC-side fault of the battery energy storage system is the same. Therefore, it is only necessary to expand for one operating state of the battery pack. This embodiment expands and discusses based on the charging of the battery pack.

[0077] In an alternative embodiment, the method includes:

[0078] Step S510: Obtain the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground;

[0079] Step S520: Based on the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground, determine the type of DC-side fault of the battery energy storage system.

[0080] In step S510, obtain the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground measured by the measurement module.

[0081] In step S520, based only on the operating state of the battery pack and the grounding state of the transformer, it is impossible to specifically know the type of DC-side fault of the specific battery energy storage system. Therefore, it is necessary to further determine the type of DC-side fault of the specific battery energy storage system through the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage of the negative pole of the battery pack to the ground, and the voltage of the positive pole of the battery pack to the ground.

[0082] In an optional implementation manner, step S520 includes:

[0083] Step S521: When the transformer is not grounded, when the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground both drop to the first preset threshold and the current of the battery pack remains stable, it is determined that the battery pack has a polar fault;

[0084] Step S522: When the transformer is not grounded, when the voltage between the positive and negative poles of the battery pack drops to the second preset threshold and the current of the battery pack rises to the third preset threshold, it is determined that there is a short circuit fault between the positive and negative poles of the battery pack;

[0085] Step S523: When the transformer is grounded, when the voltage between the positive and negative poles of the battery pack fluctuates and drops to the fourth threshold, the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground instantaneously rise to the fifth preset threshold, and the current of the battery pack instantaneously rises to the sixth preset threshold, it is determined that the battery pack has a polar fault;

[0086] Step S524: When the transformer is grounded, when the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground drop to the seventh preset threshold and no voltage greater than the eighth preset threshold is generated, it is determined that there is a short circuit fault between the positive and negative poles of the battery pack.

[0087] In step S521, Figure 5 A first schematic diagram showing the voltage waveform between the positive and negative poles of the battery pack according to an embodiment of the present application is schematically shown. Figure 6 A first schematic diagram showing the current waveform of the battery pack according to an embodiment of the present application is schematically shown. Figure 7 A first schematic diagram showing the voltage waveform of the positive pole of the battery pack to the ground according to an embodiment of the present application is schematically shown. Figure 8 A first schematic diagram showing the voltage waveform of the negative pole of the battery pack to the ground according to an embodiment of the present application is schematically shown. As Figures 5 - 8 shown, when the transformer is not grounded, the current of the battery pack and the voltage between the positive and negative poles of the battery pack both remain basically stable. When the voltage of the positive pole of the battery pack to the ground and the voltage of the negative pole of the battery pack to the ground both drop to about 1288V - 1290V at the same time, it is determined that the battery pack has a polar fault. Because there is no path for the fault current, it has little impact on the normal operation of the battery pack.

[0088] In step S522, Figure 9 The second schematic diagram schematically shows the voltage waveform between the positive electrode and the negative electrode of the battery pack according to an embodiment of the present application. Figure 10 The second schematic diagram schematically shows the current waveform of the battery pack according to an embodiment of the present application. Figure 11 The second schematic diagram schematically shows the voltage waveform of the positive electrode of the battery pack with respect to the ground according to an embodiment of the present application. Figure 12 The second schematic diagram schematically shows the voltage waveform of the negative electrode of the battery pack with respect to the ground according to an embodiment of the present application. As Figures 9 - 12 shown, when the transformer is not grounded, when the voltage between the positive electrode and the negative electrode of the battery pack drops to about 200V and the current of the battery pack rises to about 20000A, it is determined that the battery pack has a short - circuit fault between the positive electrode and the negative electrode. After the fault is removed, since the energy storage converter does not adopt a constant - voltage operation mode, the current of the battery pack, the voltage between the positive electrode and the negative electrode of the battery pack, the voltage of the negative electrode of the battery pack with respect to the ground, and the voltage of the positive electrode of the battery pack with respect to the ground will also show a low - frequency oscillation phenomenon in amplitude.

[0089] In step S523, Figure 13 The third schematic diagram schematically shows the voltage waveform between the positive electrode and the negative electrode of the battery pack according to an embodiment of the present application. Figure 14 The third schematic diagram schematically shows the current waveform of the battery pack according to an embodiment of the present application. Figure 15 The third schematic diagram schematically shows the voltage waveform of the positive electrode of the battery pack with respect to the ground according to an embodiment of the present application. Figure 16 The third schematic diagram schematically shows the voltage waveform of the negative electrode of the battery pack with respect to the ground according to an embodiment of the present application. As Figures 13 - 16 shown, when the transformer is grounded, when the voltage between the positive electrode and the negative electrode of the battery pack fluctuates and drops to about 500V, the voltage of the positive electrode of the battery pack with respect to the ground and the voltage of the negative electrode of the battery pack with respect to the ground instantaneously rise to about 400×10 4 V, and the current of the battery pack instantaneously rises to about 25×10 4 V, it is determined that the battery pack has a pole - to - ground fault. When the battery pack has a pole - to - ground fault, it is very likely to break down the battery pack, resulting in a risk of thermal runaway of the battery pack. When a DC - side pole - to - ground fault occurs, the fault current has no path on the DC side of the battery energy storage system, but the pole - to - ground fault on the DC side of the battery energy storage system will affect the AC - side voltage through the energy storage converter. The neutral - point - grounded AC system has poor anti - interference ability and weak power supply reliability, and the AC - side voltage fluctuation will in turn affect the voltage between the positive electrode and the negative electrode of the battery pack through the converter feedback. At the moment when the fault is removed, the first positive and negative bus - bar distributed capacitances with respect to the ground discharge instantaneously, and all the energy is released through the transformer neutral point.

[0090] In step S524, Figure 17 The fourth schematic diagram schematically shows the voltage waveform between the positive electrode and the negative electrode of the battery pack according to an embodiment of the present application. Figure 18 The fourth schematic diagram schematically shows the current waveform of the battery pack according to an embodiment of the present application. Figure 19 The fourth schematic diagram schematically shows the voltage waveform of the positive electrode of the battery pack with respect to the ground according to an embodiment of the present application. Figure 20 The fourth schematic diagram schematically shows the voltage waveform of the negative electrode of the battery pack with respect to the ground according to an embodiment of the present application. As Figures 17 - 20 shown, when the transformer is grounded, when the voltage of the positive electrode of the battery pack with respect to the ground and the voltage of the negative electrode of the battery pack with respect to the ground drop to about 100V and no voltage greater than the eighth preset threshold is generated, it is determined that the battery pack has a short-circuit fault between the positive electrode and the negative electrode. After the fault is removed, the voltage of the positive electrode of the battery pack with respect to the ground and the voltage of the negative electrode of the battery pack with respect to the ground oscillate abnormally and the oscillation shows an increasing trend.

[0091] By analyzing the current of the battery pack, the voltage between the positive electrode and the negative electrode of the battery pack, the voltage of the negative electrode of the battery pack with respect to the ground, and the voltage of the positive electrode of the battery pack with respect to the ground, the embodiment of the present application accurately identifies the type of DC-side fault of the battery energy storage system. When a short-circuit fault inside the battery pack is found, the fault circuit can be quickly cut off to prevent the further expansion of the fault and protect the safe operation of the battery energy storage system.

[0092] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0093] The present application is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, and the combination of processes and / or blocks in the flowchart and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one process or multiple processes and / or blocks Figure 1 one block or multiple blocks.

[0094] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction means that implements the functions specified in one or more of the processes and / or blocks Figure 1 in one or more of the processes and / or blocks Figure 1 specified in the block or blocks.

[0095] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one or more of the processes and / or blocks Figure 1 in one or more of the processes and / or blocks Figure 1 specified in the block or blocks.

[0096] In a typical configuration, a computing device includes one or more processors (CPUs), an input / output interface, a network interface, and memory.

[0097] The memory may include non-permanent memory in the form of computer-readable media, random access memory (RAM) and / or non-volatile memory such as read-only memory (ROM) or flash memory (flash RAM). Memory is an example of computer-readable media.

[0098] Computer-readable media includes both permanent and non-permanent, removable and non-removable media implemented by any method or technology for storing information. The information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile discs (DVD) or other optical storage, magnetic cassettes, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory media such as modulated data signals and carrier waves.

[0099] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising the element.

[0100] The above are only embodiments of the present application and are not used to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A battery energy storage system, characterized in that: The system includes: a battery pack, a circuit breaker group, an energy storage inverter, a transformer, a grid impedance, a lightning current generator and a grid. The battery pack, the energy storage inverter, the transformer, the grid impedance and the grid are connected in sequence. The output end of the battery pack is also connected to the circuit breaker group, and the output end of the transformer is also connected to the lightning current generator. The circuit breaker group includes a first circuit breaker, a second circuit breaker and a third circuit breaker. The positive output end of the battery pack is grounded through the first circuit breaker, and the negative output end of the battery pack is grounded through the second circuit breaker. The positive output end of the battery pack is also connected to the negative output end of the battery pack through the third circuit breaker. The circuit breaker group is used to simulate the fault of the battery energy storage system.

2. The battery energy storage system according to claim 1, characterized in that: The battery pack includes a Thevenin equivalent module, a grounding module, a cable module and a measurement module. The Thevenin equivalent module is used to simulate the equivalent internal resistance and equivalent voltage of the battery pack. The grounding module is used to simulate the grounding resistance and grounding capacitance between the energy storage compartment shell and the battery pack. The cable module is used to simulate the resistance, capacitance and inductance of the wires in the energy storage compartment. The measurement module is used to measure the current of the battery pack, the voltage between the positive and negative poles of the battery pack, the voltage between the negative pole of the battery pack and the ground, and the voltage between the positive pole of the battery pack and the ground. The first end of the Thevenin equivalent module is connected to the first end of the grounding module, the second end of the Thevenin equivalent module is connected to the second end of the grounding module, the third end of the grounding module is connected to the first end of the cable module, the fourth end of the grounding module is connected to the second end of the cable module, the third end of the cable module is connected to the first end of the measurement module, and the fourth end of the cable module is connected to the second end of the measurement module.

3. The battery energy storage system according to claim 2, characterized in that: The Thevenin equivalent module includes a first Thevenin equivalent voltage source, a second Thevenin equivalent voltage source, a first Thevenin equivalent internal resistance and a second Thevenin equivalent internal resistance, the positive pole of the first Thevenin equivalent voltage source is connected to one end of the first Thevenin equivalent internal resistance, the negative pole of the first Thevenin equivalent voltage source is connected to the positive pole of the second Thevenin equivalent voltage source, the negative pole of the second Thevenin equivalent voltage source is connected to one end of the second Thevenin equivalent internal resistance, the other end of the second Thevenin equivalent internal resistance serves as the first end of the Thevenin equivalent module, and the other end of the first Thevenin equivalent internal resistance serves as the second end of the Thevenin equivalent module.

4. The battery energy storage system according to claim 2, characterized in that: The grounding module includes a first positive and negative bus distributed capacitor to ground, a second positive and negative bus distributed capacitor to ground and a grounding resistor, the positive electrode of the first positive and negative bus distributed capacitor to ground is connected to the second end of the Thevenin equivalent module, the positive electrode of the second positive and negative bus distributed capacitor to ground is connected to the first end of the Thevenin equivalent module, the negative electrode of the first positive and negative bus distributed capacitor to ground is connected to the negative electrode of the second positive and negative bus distributed capacitor to ground and is grounded, the positive electrode of the second positive and negative bus distributed capacitor to ground is also connected to one end of the grounding resistor, the positive electrode of the second positive and negative bus distributed capacitor to ground serves as the first end of the grounding module, one end of the grounding resistor serves as the third end of the grounding module, and the positive electrode of the first positive and negative bus distributed capacitor to ground serves as the second end and the fourth end of the grounding module.

5. The battery energy storage system according to claim 2, characterized in that: The cable module includes a first cable equivalent resistor, a second cable equivalent resistor, a first cable equivalent inductor, a second cable equivalent inductor, a first cable equivalent capacitor and a second cable equivalent capacitor. The positive electrode of the first cable equivalent capacitor is connected to the fourth end of the grounding module, the negative electrode of the first cable equivalent capacitor is connected to the third end of the grounding module, the positive electrode of the first cable equivalent capacitor is also connected to one end of the first cable equivalent resistor and the first cable equivalent inductor in sequence, the negative electrode of the first cable equivalent capacitor is also connected to one end of the second cable equivalent resistor and the second cable equivalent inductor in sequence, and the other end of the second cable equivalent inductor is connected to the The negative electrode of the second cable equivalent capacitor is connected, the other end of the first cable equivalent inductor is connected to the positive electrode of the second cable equivalent capacitor, the connection between the negative electrode of the first cable equivalent capacitor and the second cable equivalent resistor serves as the first end of the cable module, the connection between the positive electrode of the first cable equivalent capacitor and the first cable equivalent resistor serves as the second end of the cable module, the connection between the negative electrode of the second cable equivalent capacitor and the other end of the second cable equivalent inductor serves as the third end of the cable module, and the connection between the positive electrode of the second cable equivalent capacitor and the other end of the first cable equivalent inductor serves as the fourth end of the cable module.

6. The battery energy storage system according to claim 1, characterized in that: The energy storage converter includes a DC side internal resistor, a DC side capacitor, an inverter, a filter inductor and a filter capacitor. The negative electrode of the DC side capacitor is connected to the negative output terminal of the battery pack, and the negative electrode of the DC side filter capacitor is also connected to the negative electrode of the inverter. The positive electrode of the DC side capacitor is connected to the positive electrode of the inverter through the DC side internal resistor, and the DC side internal resistor is also connected to the positive output terminal of the battery pack. The output terminal of the inverter is connected to the filter inductor and the filter capacitor in sequence.

7. A DC side fault detection method for a battery energy storage system, characterized in that: The method is implemented based on the battery energy storage system according to claims 1-6, and the method includes: Controlling the circuit breaker group to simulate a DC side fault of the battery energy storage system, wherein the DC side of the battery energy storage system is an output end of the battery group; Acquire the working state of the battery pack and the grounding state of the transformer, wherein the working state of the battery pack includes charging and discharging, and the grounding state of the transformer includes grounding and not grounding; Based on the working state of the battery pack and the grounding state of the transformer, the type of the DC side fault of the battery energy storage system is determined.

8. The method according to claim 7, characterized in that The determining the type of the DC side fault of the battery energy storage system based on the working state of the battery pack and the grounding state of the transformer includes: When the working state of the battery pack is charging or discharging and the transformer is not grounded, determining that the battery pack has a polarity fault or a short circuit fault between the positive and negative electrodes of the battery pack; When the working state of the battery pack is charging or discharging and the transformer is grounded, it is determined that the battery pack has a polarity fault or a short circuit fault between the positive electrode and the negative electrode of the battery pack.

9. The method according to claim 7, characterized in that: The method further comprises: Obtaining the current of the battery pack, the voltage between the positive electrode and the negative electrode of the battery pack, the voltage of the negative electrode of the battery pack to ground, and the voltage of the positive electrode of the battery pack to ground; The type of DC side fault of the battery energy storage system is determined based on the current of the battery pack, the voltage between the positive and negative electrodes of the battery pack, the voltage between the negative electrode of the battery pack and the ground, and the voltage between the positive electrode of the battery pack and the ground.

10. The method according to claim 9, characterized in that The determining the type of the DC side fault of the battery energy storage system based on the current of the battery pack, the voltage between the positive and negative electrodes of the battery pack, the negative electrode-to-ground voltage of the battery pack, and the positive electrode-to-ground voltage of the battery pack includes: When the transformer is not grounded, when the voltage of the positive electrode of the battery pack to ground and the voltage of the negative electrode of the battery pack to ground are both reduced to a first preset threshold and the current of the battery pack remains stable, it is determined that the battery pack is a polarity fault; When the transformer is not grounded, when the voltage between the positive electrode and the negative electrode of the battery pack decreases to a second preset threshold value, and the current of the battery pack increases to a third preset threshold value, it is determined that the battery pack has a short circuit fault between the positive electrode and the negative electrode; When the transformer is grounded, the voltage between the positive and negative electrodes of the battery pack fluctuates and decreases to a fourth threshold value, the voltage between the positive electrode of the battery pack and the voltage between the negative electrode of the battery pack and the ground instantaneously increases to a fifth preset threshold value, and the current of the battery pack instantaneously increases to a sixth preset threshold value, and it is determined that the battery pack is a polarity fault; When the transformer is grounded, when the voltage between the positive electrode of the battery pack and the voltage between the negative electrode of the battery pack and the ground are both reduced to the seventh preset threshold value, and no voltage greater than the eighth preset threshold value is generated, it is determined that the battery pack has a short circuit fault between the positive electrode and the negative electrode.

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