Test circuits and energy storage systems

Abstract

This application provides a test circuit and energy storage system. The test circuit includes a controller and a clamping circuit. The clamping circuit is electrically connected to the busbar inside the high-voltage cascaded energy storage unit to be tested. The controller is electrically connected to the busbar. The high-voltage cascaded energy storage unit includes an energy storage unit and a converter unit. When the clamping circuit is located inside the casing of the energy storage unit or converter unit to be tested and is electrically connected to the casing, the controller is used to acquire the test voltage between the casing and the busbar, and the voltage of the AC signal transmitted by the single-phase high-voltage line electrically connected to the high-voltage cascaded energy storage unit. Based on the AC component of the test voltage and the voltage of the AC signal, the insulation state between the casing and the energy storage unit or converter unit is determined, and the insulation level change state is determined accordingly. This helps staff to perceive insulation risks in advance and reduce the risk of accidents.

Description

Technical Field

[0001] Embodiments of this application relate to the field of insulation testing technology for energy storage systems, and more particularly to a test circuit and an energy storage system. Background Technology

[0002] An electrochemical energy storage system is a system that uses electrochemical cells as energy storage carriers and stores and releases cyclic electrical energy through an energy storage converter. This electrochemical energy storage system has advantages such as fast regulation rate, short response time, and high regulation accuracy, making it a high-quality resource for improving the security of new power systems.

[0003] High-voltage cascaded energy storage systems employing electrochemical energy storage can be directly connected to high-voltage three-phase power, generating 6kV / 10kV or 20kV / 35kV high voltage directly without a transformer. This not only reduces system losses and improves efficiency but also reduces the footprint of the energy storage system, lowering land construction costs and gradually becoming one of the excellent solutions for future large-scale electrochemical energy storage system applications. A high-voltage cascaded energy storage system comprises multiple high-voltage cascaded energy storage units. Each unit includes a container and a battery system and power conversion system (PCS) located inside the container and insulated from it. Due to the high operating voltage of the high-voltage cascaded energy storage system, there is a very high relative voltage between the battery system and the power conversion system (PCS) and the container shell (usually grounded) during operation. This voltage can reach up to 6kV or even 20kV, posing an insulation risk. Therefore, timely monitoring of the insulation level between the container and the energy storage units, and / or the insulation level between the container and the conversion units, is a key measure to reduce insulation risks. Staff typically use the bridge method to measure the equivalent insulation resistance corresponding to the above insulation levels. Since the resistance value of the bridge needs to be adjusted during the measurement process, there is a time interval in the measurement of the above equivalent insulation resistance. Therefore, the research focuses on quickly and efficiently detecting the insulation level between the enclosure and the energy storage unit and / or the insulation level between the enclosure and the converter unit in a high-voltage cascaded energy storage unit. Summary of the Invention

[0004] This application provides a test circuit and energy storage system to solve the technical problem of rapidly and efficiently detecting the insulation level between the enclosure and the energy storage unit in a high-voltage cascaded energy storage unit and / or the insulation level between the enclosure and the converter unit.

[0005] In a first aspect, embodiments of this application provide a test circuit, which includes a controller and a clamping circuit; the test circuit is electrically connected to a high-voltage cascaded energy storage unit, which includes an energy storage unit, a converter unit and a housing, wherein the energy storage unit is insulated from the housing and the converter unit is insulated from the housing;

[0006] The energy storage unit includes an energy storage shell and an energy storage circuit, the energy storage circuit being located inside the energy storage shell; the converter unit includes a converter shell and a converter circuit, the converter circuit being located inside the converter shell; the energy storage circuit is electrically connected to the converter circuit via a busbar, the converter circuit is electrically connected to a single-phase high-voltage line, the clamping circuit is electrically connected to the busbar, and the controller is electrically connected to the busbar;

[0007] The converter unit is used to acquire the AC signal transmitted by the single-phase high-voltage line;

[0008] The controller is used to acquire a first test voltage between the energy storage housing and the busbar and the voltage of the AC signal when the clamping circuit is located inside the energy storage housing and electrically connected to the energy storage housing, and to determine the insulation state between the enclosure and the energy storage unit based on the AC component of the first test voltage and the voltage of the AC signal.

[0009] The controller is also configured to, when the clamping circuit is located inside the converter housing and electrically connected to the converter housing, acquire the second test voltage between the converter housing and the bus and the voltage of the AC signal, and determine the insulation state between the enclosure and the energy storage unit based on the AC component of the second test voltage and the voltage of the AC signal.

[0010] In the above technical solution, for measuring the insulation status between the outer shell and the container of the converter unit in the high-voltage cascaded energy storage unit and the unit under test in the energy storage unit, which are insulated from the container body, a clamping circuit in the test circuit is electrically connected to the bus in the high-voltage cascaded energy storage unit and the outer shell of the unit under test. A loop consisting of a single-phase high-voltage line, the clamping circuit, and the insulation structure between the outer shell and the container is constructed. The controller, which is electrically connected to the clamping circuit, obtains the AC component of the test voltage clamped by the clamping circuit. Based on the relationship between this AC component and the AC signal transmitted by the single-phase high-voltage line that generates this AC component, the insulation status between the container and the unit under test is determined. This allows the test circuit consisting of the clamping circuit and the controller to obtain the insulation level between the container and the energy storage unit and / or the insulation level between the container and the converter unit in the high-voltage cascaded energy storage unit in real time, and to determine the insulation level change status accordingly. This helps staff to perceive insulation risks in advance and reduce the risk of accidents.

[0011] In one feasible implementation, the clamping circuit includes a first resistor and a second resistor, a first end of the first resistor is electrically connected to the positive terminal of the bus, a second end of the first resistor is electrically connected to the first end of the second resistor, and a second end of the second resistor is electrically connected to the negative terminal of the bus.

[0012] The resistance values ​​of the first resistor and the second resistor are equal.

[0013] In one feasible implementation, when the clamping circuit is located inside the energy storage housing, the second end of the first resistor and the first end of the second resistor are electrically connected to a single point and then electrically connected to the energy storage housing.

[0014] In one feasible implementation, the controller is used to acquire a first test voltage between the energy storage casing and the busbar, and the voltage of the AC signal. Based on the AC component of the first test voltage and the voltage of the AC signal, the controller determines the insulation state between the enclosure and the energy storage unit, specifically including:

[0015] The controller is used to acquire the first test voltage between the energy storage casing and the busbar, and the voltage of the AC signal;

[0016] The first proportional parameter is determined based on the AC component of the first test voltage and the voltage of the AC signal.

[0017] The insulation state between the enclosure and the energy storage unit is determined based on the first proportional parameter.

[0018] In one feasible implementation, the controller is used to determine the insulation state between the enclosure and the energy storage unit based on the first proportional parameter, specifically including:

[0019] The controller determines the insulation state between the enclosure and the energy storage unit based on the first proportional parameter and the first preset proportional parameter threshold.

[0020] In the above technical solution, the first and second resistors with the same resistance value in the clamping circuit are connected across the positive and negative terminals of the busbar, and the connection point of the two resistors is electrically connected to the energy storage shell. This ensures that during the operation of the high-voltage cascaded energy storage unit, regardless of the current conduction loop formed by the single-phase high-voltage line and the energy storage circuit inside the energy storage unit, there is always a resistor and the insulation device between the enclosure and the energy storage unit that divides the AC signal transmitted by the single-phase high-voltage line. The controller obtains the AC component of the first test voltage between the busbar and the energy storage shell by sampling the voltage across the resistor. The controller uses this AC component and the AC signal transmitted by the single-phase high-voltage line to determine the first proportional parameter, thereby determining the voltage division of the AC signal between the resistor and the insulation device in the clamping circuit, and thus determining the insulation state between the enclosure and the energy storage unit.

[0021] In one feasible implementation, the controller determines the insulation state between the housing and the energy storage unit based on the first proportional parameter, specifically including:

[0022] The controller calculates the equivalent insulation resistance between the energy storage unit and the housing based on the first proportional parameter and the resistance value of the first resistor.

[0023] The insulation state between the enclosure and the energy storage unit is determined based on the resistance value of the equivalent insulation resistance and the first preset insulation resistance threshold.

[0024] In the above technical solution, the controller uses the AC component of the first test voltage between the bus and the energy storage shell and the AC signal transmitted by the single-phase high-voltage line to determine the first proportional parameter, so as to determine the voltage division between a resistor and an insulation device in the clamping circuit. When the resistance value of the resistor connected between the bus and the energy storage shell is known, the equivalent insulation resistance value of the insulation device can be determined, so as to more intuitively determine the insulation state between the enclosure and the energy storage unit.

[0025] In one feasible implementation, when the clamping circuit is located inside the converter housing, the second end of the first resistor and the first end of the second resistor are electrically connected to a single point and then electrically connected to the converter housing.

[0026] In one feasible implementation, the controller is used to acquire a second test voltage between the converter housing and the busbar, and the voltage of the AC signal. Based on the AC component of the second test voltage and the voltage of the AC signal, the controller determines the insulation state between the enclosure and the energy storage unit, specifically including:

[0027] The controller is used to acquire the second test voltage between the converter housing and the bus, and the voltage of the AC signal;

[0028] The second proportional parameter is determined based on the second test voltage and the voltage of the AC signal;

[0029] The insulation state between the enclosure and the energy storage unit is determined based on the second proportional parameter.

[0030] In one feasible implementation, the controller is used to determine the insulation state between the enclosure and the converter unit based on the second proportional parameter, specifically including:

[0031] The controller determines the insulation state between the housing and the converter unit based on the second proportional parameter and the second preset proportional parameter threshold.

[0032] In the above technical solution, by placing the clamping circuit inside the converter housing and connecting the first and second resistors with the same resistance value in the clamping circuit across the positive and negative terminals of the busbar, and electrically connecting the connection point of the two resistors to the converter housing, the clamping circuit and the insulation device between the housing and the converter unit divide the AC signal transmitted by the single-phase high-voltage line. The controller obtains the AC component of the second test voltage between the busbar and the converter housing by sampling the voltage across the resistor. The controller uses this AC component and the AC signal transmitted by the single-phase high-voltage line to determine the second proportional parameter, thereby determining the voltage division of the AC signal between the clamping circuit and the insulation device, and thus determining the insulation state between the housing and the converter unit.

[0033] In one feasible implementation, the controller determines the insulation state between the housing and the converter unit based on the second proportional parameter, specifically including:

[0034] The controller calculates the equivalent insulation resistance between the converter unit and the housing based on the second proportional parameter and the resistance value of the first resistor.

[0035] The insulation state between the enclosure and the converter unit is determined based on the resistance value of the equivalent insulation resistance and the second preset insulation resistance threshold.

[0036] In the above technical solution, the controller uses the AC component of the second test voltage between the bus and the converter housing and the AC signal transmitted by the single-phase high-voltage line to determine the second proportional parameter, so as to determine the voltage division between a resistor and an insulation device in the clamping circuit. When the resistance value of the resistor connected between the bus and the converter housing is known, the equivalent insulation resistance value of the insulation device can be determined, so as to more intuitively determine the insulation state between the enclosure and the converter unit.

[0037] Secondly, embodiments of this application provide an energy storage system, which includes three sets of high-voltage cascaded energy storage sets, multiple test circuits as described in any of the first aspects, and three-phase high-voltage lines. Each set of high-voltage cascaded energy storage sets includes multiple high-voltage cascaded energy storage units; each test circuit and each high-voltage cascaded energy storage unit are electrically connected in a one-to-one correspondence.

[0038] Each group of high-voltage cascaded energy storage units is electrically connected to the corresponding phase high-voltage line, and the three groups of high-voltage cascaded energy storage units are electrically connected in a star configuration.

[0039] In one feasible implementation, the converter unit in each test circuit is provided with an AC signal terminal;

[0040] In each of the high-voltage cascaded energy storage sets, the AC signal terminals of multiple high-voltage cascaded energy storage units are cascaded and electrically connected.

[0041] The test circuit and energy storage system provided in this application embodiment include a controller and a clamping circuit. The clamping circuit is electrically connected to the busbar inside the high-voltage cascaded energy storage unit to be tested. The controller is electrically connected to the busbar. The high-voltage cascaded energy storage unit includes an energy storage unit and a converter unit. The controller is used to acquire a first test voltage between the energy storage unit and the busbar and the voltage of the AC signal transmitted by the single-phase high-voltage line electrically connected to the high-voltage cascaded energy storage unit when the clamping circuit is located inside the energy storage housing of the energy storage unit and electrically connected to the energy storage housing. Based on the AC component of the first test voltage and the voltage of the AC signal, the insulation state between the housing and the energy storage unit is determined. The controller is also used to acquire a second test voltage between the converter housing and the busbar and the voltage of the AC signal when the clamping circuit is located inside the converter housing of the converter unit and electrically connected to the converter housing. Based on the AC component of the second test voltage and the voltage of the AC signal, the insulation state between the housing and the energy storage unit is determined, and the insulation level change state is determined accordingly. This helps staff to perceive insulation risks in advance and reduce the risk of accidents. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0043] Figure 1 This is a circuit diagram of a high-voltage cascaded energy storage system provided in this application according to an exemplary embodiment;

[0044] Figure 2 This is a circuit structure diagram of a high-voltage cascaded energy storage unit provided in accordance with an exemplary embodiment of this application;

[0045] Figure 3This is a circuit diagram of a high-voltage cascaded energy storage system provided in this application according to another exemplary embodiment;

[0046] Figure 4 This is a schematic diagram of the circuit connection of a high-voltage cascaded energy storage unit and a test circuit according to an exemplary embodiment of this application;

[0047] Figure 5A This is a circuit diagram for insulation measurement and analysis of a converter unit provided in accordance with an exemplary embodiment of this application;

[0048] Figure 5B This is a circuit diagram for insulation measurement and analysis of an energy storage unit provided in accordance with an exemplary embodiment of this application;

[0049] Figure 6 This is a circuit diagram of an energy storage system provided in accordance with an exemplary embodiment of this application.

[0050] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0051] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0052] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, components, features, and elements with the same names in different embodiments of this application may have the same meaning or different meanings, the specific meaning of which must be determined by its interpretation in that specific embodiment or further in conjunction with the context of that specific embodiment.

[0053] It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0054] An electrochemical energy storage system is a system that uses electrochemical cells as energy storage carriers and stores and releases cyclic electrical energy through an energy storage converter. This electrochemical energy storage system has advantages such as fast regulation rate, short response time, and high regulation accuracy, making it a high-quality resource for improving the security of new power systems.

[0055] The circuit diagram of a high-voltage cascaded energy storage system using an electrochemical energy storage system is shown below. Figure 1 As shown, the high-voltage cascaded energy storage system includes high-voltage lines of phase A, phase B and phase C and three sets of high-voltage cascaded energy storage units. The equivalent ground impedance Z of each phase high-voltage line to the ground is high impedance.

[0056] Each group of high-voltage cascaded energy storage units comprises N cascaded high-voltage energy storage units. Specifically, the first group of high-voltage cascaded energy storage units, electrically connected to the A-phase high-voltage line, includes the first A-phase high-voltage cascaded energy storage unit A1, the second A-phase high-voltage cascaded energy storage unit A2, the third A-phase high-voltage cascaded energy storage unit A3, ..., the Nth A-phase high-voltage cascaded energy storage unit AN. One end of the first A-phase high-voltage cascaded energy storage unit A1 is electrically connected to the A-phase high-voltage line, and the other high-voltage cascaded energy storage units are connected sequentially. The second group of high-voltage cascaded energy storage units, electrically connected to the B-phase high-voltage line, includes the first B-phase high-voltage cascaded energy storage unit B1 and the second B-phase high-voltage cascaded energy storage unit B2. The three high-voltage cascaded energy storage units are: B3 (phase B3), ..., BN (phase BN), with one end of B1 (phase B1) electrically connected to the phase B high-voltage line. The other high-voltage cascaded energy storage units are connected sequentially. The third high-voltage cascaded energy storage unit, electrically connected to the phase C high-voltage line, includes C1 (phase C1), C2 (phase C2), C3 (phase C3), ..., CN (phase CN), with one end of C1 electrically connected to the phase C high-voltage line. The other high-voltage cascaded energy storage units are connected sequentially. These three high-voltage cascaded energy storage units are connected in a star configuration, meaning one end of the Nth high-voltage cascaded energy storage unit AN (phase A), one end of the Nth high-voltage cascaded energy storage unit BN (phase B), and one end of the Nth high-voltage cascaded energy storage unit CN (phase C) are connected to a single point. Because high-voltage cascaded energy storage systems can be directly connected to high-voltage three-phase power without going through a transformer, directly generating 6kV / 10kV or 20kV / 35kV high voltage, they not only reduce system losses and improve efficiency, but also reduce the footprint of the energy storage system and lower land construction costs, gradually becoming one of the excellent solutions for future large-scale electrochemical energy storage system applications.

[0057] The circuit structure of each high-voltage cascaded energy storage unit is as follows: Figure 2As shown, the container includes a container body 10, a power converter unit 30, and an energy storage unit 40. The container body 10 has a partition 101 that divides the internal space of the container body 10 into a power converter compartment 201 and a battery compartment 202. The power converter unit 30 is located inside the power converter compartment 201, and the energy storage unit 40 is located inside the battery compartment 202. The power converter unit 30 is insulated from the container body of the power converter compartment 201, and the energy storage unit 40 is insulated from the container body of the battery compartment 202.

[0058] The converter unit 30 includes a converter housing and a converter circuit. The converter circuit is located inside the converter housing and includes a single-phase bridge arm circuit, a capacitor C, a first filter inductor L1, and a second filter inductor L2. The single-phase bridge arm circuit includes a first bridge arm circuit 301 and a second bridge arm circuit 302. The first end of the first bridge arm circuit 301, the first end of the second bridge arm circuit 302, and the first end of the capacitor C are electrically connected to a point and then electrically connected to the first end of the first filter inductor L1. The second end of the first bridge arm circuit 301, the second end of the second bridge arm circuit 302, and the second end of the capacitor C are electrically connected to a point and then electrically connected to the first end of the second filter inductor L2. The second end of the first filter inductor L1 is electrically connected to the positive terminal P+ of the bus, and the second end of the second filter inductor L2 is electrically connected to the negative terminal P- of the bus. The positive terminal P+ and the negative terminal P- of the bus form the branch terminal of the converter unit 30. The first bridge arm circuit 301 has a first bridge arm midpoint 303, and the second bridge arm circuit 302 has a second bridge arm midpoint 304. The first bridge arm midpoint 303 serves as the first AC signal transmission terminal InP, and the second bridge arm midpoint 304 serves as the second AC signal transmission terminal InN. The first AC signal transmission terminal InP and the second bridge arm midpoint 304 serve as the second AC signal transmission terminal InN to form the AC terminal of the converter unit 30.

[0059] The energy storage unit 40 includes an energy storage shell and an energy storage circuit. The energy storage circuit is located inside the energy storage shell and includes a fuse F1 and an energy storage battery BT. The first end of the fuse F1 is electrically connected to the positive terminal P+ of the busbar, the second end of the fuse F1 is electrically connected to the positive terminal of the energy storage battery BT, and the negative terminal of the energy storage battery BT is electrically connected to the negative terminal P- of the busbar.

[0060] The converter unit 30 is used to obtain the AC signal transmitted by the single-phase high-voltage line from its AC terminal, rectify the AC signal into a DC signal, and output the DC signal from its DC terminal; the converter unit 30 is also used to obtain the DC signal transmitted by the energy storage unit 40 from its DC terminal, invert the DC signal into an AC signal, and output the AC signal from its AC terminal.

[0061] The energy storage unit 40 is used to store the electrical energy corresponding to the DC signal it obtains from the bus into the energy storage battery BT, and also to output a DC signal to the bus when the energy storage battery BT releases electrical energy. A high-voltage cascaded energy storage unit can be regarded as a controllable voltage source.

[0062] based on Figure 2 The circuit structure shown is Figure 1 The circuit connection structure of the high-voltage cascaded energy storage system shown is as follows: Figure 3 As shown below, the cascading connection method of multiple A-phase high-voltage cascaded energy storage units within the first group of high-voltage cascaded energy storage units electrically connected to the A-phase high-voltage line is explained. The first AC signal transmission terminal InP of the first A-phase high-voltage cascaded energy storage unit A1 is electrically connected to the A-phase high-voltage line. The second AC signal transmission terminal InN of the first A-phase high-voltage cascaded energy storage unit A1 is electrically connected to the first AC signal transmission terminal InP of the second A-phase high-voltage cascaded energy storage unit A2. The second AC signal transmission terminal InN of the second A-phase high-voltage cascaded energy storage unit A2 is electrically connected to the first AC signal transmission terminal InP of the third A-phase high-voltage cascaded energy storage unit A3, and so on, until the second AC signal transmission terminal InN of the (N-1)th A-phase high-voltage cascaded energy storage unit AN-1 is electrically connected to the first AC signal transmission terminal InP of the Nth A-phase high-voltage cascaded energy storage unit AN. The connection method of each high-voltage cascaded energy storage unit in the second and third high-voltage cascaded energy storage sets is the same as that in the first high-voltage cascaded energy storage set, and will not be repeated here. Furthermore, the second AC signal transmission terminal InN of the Nth high-voltage cascaded energy storage unit AN in phase A, the second AC signal transmission terminal InN of the Nth high-voltage cascaded energy storage unit BN in phase B, and the second AC signal transmission terminal InN of the Nth high-voltage cascaded energy storage unit CN in phase C are electrically connected to a single point, thus forming a star connection between the three high-voltage cascaded energy storage sets.

[0063] Due to the high operating voltage of the high-voltage cascaded energy storage system, there is a high relative voltage between the converter unit 30 and the energy storage unit 40 and the container body 10 during operation. In the 10kV system, the phase voltage of each single-phase high-voltage line is 10 / 1.732 = 5.774kV, with a peak value of 8.164kV; in the 35kV system, the effective value is 35 / 1.732 = 20.2kV, with a peak value of 28.574kV. Since the first AC signal transmission terminal InP of each phase's first high-voltage cascaded energy storage unit is electrically connected to the corresponding phase's high-voltage line, the effective value of the voltage obtained by each phase's first high-voltage cascaded energy storage unit in the 10kV system is 5.774kV, with a peak value of 8.164kV; in the 35kV system, the effective value of the voltage obtained by each phase's first high-voltage cascaded energy storage unit is 20.2kV, with a peak value of 28.574kV. Furthermore, according to... Figure 2It can be seen that during the alternating conduction of the bridge arm circuit, the positive and negative terminals of the energy storage battery will alternately connect to the first AC signal transmission terminal InP. Ignoring the turn-on voltage drop of the transistors in the bridge arm circuit and the voltage drops of the first filter inductor L1 and the second filter inductor L2, the voltages to ground of the positive and negative terminals of the energy storage battery are equal to the voltages to ground of the first AC signal transmission terminal InP. That is, in a 10kV system, the effective value is 10 / 1.732 = 5.774kV, and the peak value is 8.164kV; in a 35kV system, the effective value is 35 / 1.732 = 20.2kV, and the peak value is 28.574kV. Therefore, the insulation level of the converter unit and energy storage unit of the high-voltage cascaded energy storage unit to ground needs to be designed according to the requirements of a 10kV system or a 35kV system, and a good insulation level must be maintained throughout its lifespan to avoid insulation breakdown and short circuit to ground faults. Therefore, timely monitoring of the insulation levels between the enclosure 10 and the energy storage unit 40, and / or between the enclosure 10 and the converter unit 30, is a key measure to reduce insulation risks. Workers typically use the bridge method to measure the equivalent insulation resistance corresponding to these insulation levels. However, because the resistance value within the bridge needs to be adjusted during the measurement process, there is a time interval between these measurements. Therefore, rapidly and efficiently detecting the insulation levels between the enclosure and the energy storage unit, and / or between the enclosure and the converter unit in a high-voltage cascaded energy storage unit, is a key research focus.

[0064] To address the aforementioned problems, this application provides a test circuit and energy storage system to solve the technical problem of rapidly and efficiently detecting the insulation level between the enclosure and the energy storage unit in a high-voltage cascaded energy storage unit and / or the insulation level between the enclosure and the converter unit. The technical concept of this application is as follows: For measuring the insulation state between the energy storage unit and / or converter unit under test and the container body, the clamping circuit in the test circuit is electrically connected to the bus in the high-voltage cascaded energy storage unit and the outer shell of the unit under test, constructing a loop consisting of a single-phase high-voltage line, the clamping circuit, and the insulation structure between the outer shell and the container. The controller, which is electrically connected to the clamping circuit, acquires the AC component of the test voltage clamped by the clamping circuit. Based on the relationship between this AC component and the AC signal transmitted by the single-phase high-voltage line that generates the AC component, the insulation state between the container and the unit under test is determined. This allows the test circuit, consisting of the clamping circuit and the controller, to acquire in real time the insulation level between the container and the energy storage unit and / or the insulation level between the container and the converter unit in the high-voltage cascaded energy storage unit, and to determine the insulation level change state accordingly. This helps personnel to perceive insulation risks in advance and reduce the risk of accidents.

[0065] The circuit structure of the test circuit and the process of measuring the insulation state of the high-voltage cascaded energy storage circuit using this test circuit are explained in detail below.

[0066] Figure 4This is a circuit connection diagram of a high-voltage cascaded energy storage unit and a test circuit provided according to an exemplary embodiment of this application, as shown below. Figure 4 As shown, the test circuit includes a controller 50 and a clamping circuit 60, with the clamping circuit 60 electrically connected to the busbar. When the test circuit measures the insulation state between the enclosure 10 and the converter unit 30, it is placed inside the energy storage enclosure and electrically connected to it. The controller 50 obtains a first test voltage between the energy storage enclosure and the busbar through a voltage sampling device. The controller 50 also obtains the voltage value of the AC signal. Based on the AC component of the first test voltage and the voltage of the AC signal, the insulation state between the enclosure and the energy storage unit is determined. In one embodiment, the controller 50 can obtain the first test voltage through a sampling resistor connected between the energy storage enclosure and the busbar, and the controller 50 can obtain the voltage value of the AC signal through a monitoring device. In another embodiment, the controller 50 can determine the voltage value of the AC signal by the position of the high-voltage cascaded energy storage unit in its high-voltage cascaded energy storage set. More specifically, it determines the voltage value of the first AC signal transmission terminal InP, that is, the voltages shared between the first AC signal transmission terminal InP and the second AC signal transmission terminal InN of each high-voltage cascaded energy storage unit in a high-voltage cascaded energy storage set are the same. The controller 50 divides the voltage value transmitted by the single-phase high-voltage line by N, and then multiplies the quotient by the product of the number of high-voltage cascaded energy storage units relative to the neutral point to determine the voltage value of the first AC signal transmission terminal InP of the high-voltage cascaded energy storage unit, where N is the number of high-voltage cascaded energy storage units in a high-voltage cascaded energy storage set. Figure 1 Taking the energy storage system shown as an example, if the line voltage of the high-voltage line is 10KV, and the A-phase high-voltage cascaded energy storage system includes 10 high-voltage cascaded energy storage units, when calculating the voltage value of the first AC signal transmission terminal InP of the first high-voltage cascaded energy storage unit A1 in phase A, the position value of A1 relative to the neutral point is 10, and the voltage value is... When determining the voltage value of the first AC signal transmission terminal InP of the fifth high-voltage cascaded energy storage unit A5 in phase A, the position of A5 relative to the neutral point is 6, and the voltage value is...

[0067] When the test circuit measures the insulation state between the housing 10 and the energy storage unit 40, the test circuit is placed inside the converter housing and electrically connected to the converter housing. The controller 50 obtains a second test voltage between the converter housing and the busbar through a voltage sampling device. The controller 50 also obtains the voltage value of the AC signal. Based on the AC component of the second test voltage and the voltage of the AC signal, the insulation state between the housing and the converter unit is determined. In one embodiment, the controller 50 can obtain the second test voltage through a sampling resistor connected between the converter housing and the busbar, and the controller 50 can obtain the voltage value of the AC signal through a monitoring device. In another embodiment, the controller 50 can determine the voltage value of the AC signal through the position of the high-voltage cascaded energy storage unit in its high-voltage cascaded energy storage array.

[0068] In the above technical solution, for measuring the insulation status between the outer shell and the container of the converter unit in the high-voltage cascaded energy storage unit and the unit under test in the energy storage unit, which are insulated from the container body, a clamping circuit in the test circuit is electrically connected to the bus in the high-voltage cascaded energy storage unit and the outer shell of the unit under test. A loop consisting of a single-phase high-voltage line, the clamping circuit, and the insulation structure between the outer shell and the container is constructed. The controller, which is electrically connected to the clamping circuit, obtains the AC component of the test voltage clamped by the clamping circuit. Based on the relationship between this AC component and the AC signal transmitted by the single-phase high-voltage line that generates this AC component, the insulation status between the container and the unit under test is determined. This allows the test circuit consisting of the clamping circuit and the controller to obtain the insulation level between the container and the energy storage unit and / or the insulation level between the container and the converter unit in the high-voltage cascaded energy storage unit in real time, and to determine the insulation level change status accordingly. This helps staff to perceive insulation risks in advance and reduce the risk of accidents.

[0069] In one application scenario, the clamping circuit 60 includes two resistors, such as Figure 4 As shown, when the clamping circuit 60 is located inside the converter housing, the clamping circuit includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 is electrically connected to the positive terminal P+ of the busbar, the second end of the first resistor R1 is electrically connected to the first end of the second resistor R2, the second end of the second resistor R2 is electrically connected to the negative terminal P- of the busbar, and the second end of the first resistor R1 and the first end of the second resistor R2 are electrically connected to a point and then electrically connected to the energy storage housing. The resistance values ​​of the first resistor R1 and the second resistor R2 are equal.

[0070] The insulation measurement and analysis circuit diagram of converter unit 30 is as follows: Figure 5AAs shown. The voltage obtained at the first AC signal transmission terminal InP can be equivalent to the power supply S. The first bridge arm circuit and the second bridge arm circuit can be equivalent to two switches that are not closed at the same time. The first resistor R1 and the second resistor R2 are connected in series and then connected in parallel to the positive and negative terminals of the energy storage point BT. The first resistor R1 and the second resistor R2 are electrically connected to the converter housing. When the container body is grounded, the equivalent insulation resistance of the insulation device between the converter housing and the container body is R5.

[0071] According to Thevenin's theorem in circuit theory, the voltages between the positive and negative terminals and the battery pack casing can be calculated as the superposition of DC and AC voltages. The voltage across the first resistor R1 is u. t , Among them, u DC u represents the voltage between the positive and negative terminals of the energy storage battery BT. S This represents the AC voltage obtained at the first AC signal transmission terminal InP. If R5 >> R1, the voltage across the first resistor R1 is u. t It can be represented as Therefore, the controller 50 can obtain the voltage value across the first resistor R1, and use the ratio of the AC component in the voltage value to the AC signal output by the power supply S to determine the voltage division state of the AC signal by the equivalent insulation resistance R5 between the converter unit 30 and the enclosure and the first resistor R1, so as to determine the insulation state between the converter unit 30 and the enclosure.

[0072] When determining the insulation state between the enclosure and the converter unit 30, the controller 50 acquires the second test voltage and the AC signal voltage between the converter enclosure and the bus. Based on the AC component of the second test voltage and the AC signal voltage, it determines a second proportional parameter and, based on the second proportional parameter, determines the insulation state between the enclosure and the converter unit 30. The second proportional parameter is the quotient of the AC component divided by the AC signal voltage.

[0073] More specifically, the controller 50 acquires the second test voltage and the AC signal voltage between the converter housing and the positive terminal P+ of the bus. Based on the AC component of the second test voltage and the AC signal voltage, it calculates a second proportional parameter. In one embodiment, the controller 50 determines the insulation state between the housing and the converter unit 30 based on the second proportional parameter and a second preset proportional parameter threshold. That is, when the second proportional parameter is greater than or equal to the second preset proportional parameter threshold, the insulation state difference between the housing and the converter unit 30 is considered; when the second proportional parameter is less than the second preset proportional parameter threshold, the insulation state difference between the housing and the converter unit is considered. The insulation between the converter unit 30 and the housing is good. In another embodiment, the controller 50 calculates the equivalent insulation resistance between the converter unit 30 and the housing based on the second proportional parameter and the resistance value of the first resistor R1. Based on the resistance value of the equivalent insulation resistance and the second preset insulation resistance threshold, the controller determines the insulation state between the housing and the converter unit 30. That is, when the resistance value of the equivalent insulation resistance is greater than the second preset insulation resistance threshold, the insulation state between the housing and the converter unit 30 is good; when the resistance value of the equivalent insulation resistance is less than or equal to the second preset insulation resistance threshold, the insulation state between the housing and the converter unit 30 is good.

[0074] In the above technical solution, the controller uses the AC component of the second test voltage between the busbar and the transformer housing and the AC signal transmitted by the single-phase high-voltage line to determine the second proportional parameter. This parameter determines the voltage division of the AC signal between a resistor and the insulation device in the clamping circuit. When the resistance value of the resistor connected between the busbar and the transformer housing is known, the equivalent insulation resistance value of the insulation device can be determined. This allows for a more intuitive determination of the insulation status between the enclosure and the transformer unit, helping staff to perceive insulation risks in advance and reduce the risk of accidents.

[0075] In another application scenario, the clamping circuit 60 includes two resistors, such as Figure 4 As shown, when the clamping circuit 60 is located inside the energy storage casing, the clamping circuit includes a first resistor R3 and a second resistor R4. The first end of the first resistor R3 is electrically connected to the positive terminal P+ of the busbar, the second end of the first resistor R3 is electrically connected to the first end of the second resistor R4, the second end of the second resistor R4 is electrically connected to the negative terminal P- of the busbar, and the second end of the first resistor R3 and the first end of the second resistor R4 are electrically connected to a point and then electrically connected to the energy storage casing. The resistance values ​​of the first resistor R3 and the second resistor R4 are equal.

[0076] The insulation measurement and analysis circuit diagram of energy storage unit 40 is as follows: Figure 5B As shown, and Figure 5AThe difference lies in the fact that the equivalent insulation resistance of the insulation device between the energy storage unit 40 and the enclosure is R6. The controller 50 can obtain the voltage value across the first resistor R3, and use the ratio of the AC component in this voltage value to the AC signal output by the power supply S to determine the voltage division state of the AC signal by the equivalent insulation resistance R6 and the first resistor R3 between the energy storage unit 40 and the enclosure, thereby determining the insulation state between the energy storage unit 40 and the enclosure.

[0077] When determining the insulation state between the enclosure and the energy storage unit 40, the controller 50 acquires the first test voltage and the voltage of the AC signal between the energy storage enclosure and the busbar. Based on the AC component of the first test voltage and the voltage of the AC signal, it determines a first proportional parameter and, based on the first proportional parameter, determines the insulation state between the enclosure and the energy storage unit 40. The first proportional parameter is the quotient of the AC component divided by the voltage of the AC signal.

[0078] More specifically, the controller 50 acquires the first test voltage and the voltage of the AC signal between the energy storage casing and the positive terminal P+ of the busbar. Based on the AC component of the first test voltage and the voltage of the AC signal, it calculates a first proportional parameter. In one embodiment, the controller 50 determines the insulation state between the casing and the energy storage unit 40 based on the first proportional parameter and a first preset proportional parameter threshold. That is, when the first proportional parameter is greater than or equal to the first preset proportional parameter threshold, the insulation state between the casing and the energy storage unit 40 is poor; when the first proportional parameter is less than the first preset proportional parameter threshold, the insulation state between the casing and the energy storage unit 40 is good. In another embodiment, the controller 50 calculates the equivalent insulation resistance between the energy storage unit 40 and the casing based on the first proportional parameter and the resistance value of the first resistor R3, so as to more intuitively determine the insulation state between the casing and the energy storage unit. More specifically, the controller 50 determines the insulation state between the enclosure and the energy storage unit 40 based on the value of the insulation equivalent resistance and the first preset insulation resistance threshold. That is, when the value of the insulation equivalent resistance is greater than the first preset insulation resistance threshold, the insulation state between the enclosure and the energy storage unit 40 is good; when the value of the insulation equivalent resistance is less than or equal to the first preset insulation resistance threshold, the insulation state between the enclosure and the energy storage unit 40 is good.

[0079] In the above technical solution, the first and second resistors with the same resistance value in the clamping circuit are connected across the positive and negative terminals of the busbar, and the connection point of the two resistors is electrically connected to the energy storage shell. This ensures that during the operation of the high-voltage cascaded energy storage unit, regardless of the current conduction loop formed by the single-phase high-voltage line and the energy storage circuit inside the energy storage unit, there is always a resistor and the insulation device between the enclosure and the energy storage unit that divides the AC signal transmitted by the single-phase high-voltage line. The controller obtains the AC component of the first test voltage between the busbar and the energy storage shell by sampling the voltage across the resistor. The controller uses this AC component and the AC signal transmitted by the single-phase high-voltage line to determine the first proportional parameter, thereby determining the voltage division of the AC signal between the resistor and the insulation device in the clamping circuit, and thus determining the insulation state between the enclosure and the energy storage unit.

[0080] Figure 6 This is a circuit diagram of an energy storage system provided in an exemplary embodiment of this application, such as... Figure 6 As shown, it includes three sets of high-voltage cascaded energy storage units, multiple test circuits, and three-phase high-voltage lines. Each set of high-voltage cascaded energy storage units includes multiple high-voltage cascaded energy storage units. Each test circuit and each high-voltage cascaded energy storage unit is electrically connected to the ground in a one-to-one correspondence. The connection method is similar to... Figure 4 The circuit connections shown are the same, so they will not be described again here.

[0081] Each group of high-voltage cascaded energy storage units is electrically connected to its corresponding high-voltage line. The three groups of high-voltage cascaded energy storage units are connected in a star configuration. Within each high-voltage cascaded energy storage unit, the converter unit is equipped with an AC signal terminal. In each group of high-voltage cascaded energy storage units, the AC signal terminals of multiple high-voltage cascaded energy storage units are cascaded and electrically connected. More specifically, the connection method between each group of high-voltage cascaded energy storage units and its corresponding high-voltage line, as well as the connection method of each high-voltage cascaded energy storage unit within each group of high-voltage cascaded energy storage units, are described in detail below. Figure 3 The connection methods are the same, so they will not be described again here.

[0082] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0083] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A test circuit, characterized in that, The test circuit includes a controller and a clamping circuit; the test circuit is electrically connected to the high-voltage cascaded energy storage unit, which includes an energy storage unit, a converter unit and a housing, wherein the energy storage unit is insulated from the housing and the converter unit is insulated from the housing. The energy storage unit includes an energy storage shell and an energy storage circuit, the energy storage circuit being located inside the energy storage shell; the converter unit includes a converter shell and a converter circuit, the converter circuit being located inside the converter shell; the energy storage circuit is electrically connected to the converter circuit via a busbar, the converter circuit is electrically connected to a single-phase high-voltage line, the clamping circuit is electrically connected to the busbar, and the controller is electrically connected to the busbar; The converter unit is used to acquire the AC signal transmitted by the single-phase high-voltage line; The controller is used to acquire a first test voltage between the energy storage housing and the busbar and the voltage of the AC signal when the clamping circuit is located inside the energy storage housing and electrically connected to the energy storage housing, and to determine the insulation state between the enclosure and the energy storage unit based on the AC component of the first test voltage and the voltage of the AC signal. The controller is also configured to, when the clamping circuit is located inside the converter housing and electrically connected to the converter housing, acquire a second test voltage between the converter housing and the bus, and the voltage of the AC signal, and determine the insulation state between the housing and the converter unit based on the AC component of the second test voltage and the voltage of the AC signal.

2. The test circuit according to claim 1, characterized in that, The clamping circuit includes a first resistor and a second resistor. The first end of the first resistor is electrically connected to the positive terminal of the busbar, the second end of the first resistor is electrically connected to the first end of the second resistor, and the second end of the second resistor is electrically connected to the negative terminal of the busbar. The resistance values ​​of the first resistor and the second resistor are equal.

3. The test circuit according to claim 2, characterized in that, When the clamping circuit is located inside the energy storage housing, the second end of the first resistor and the first end of the second resistor are electrically connected to a single point and then electrically connected to the energy storage housing.

4. The test circuit according to claim 3, characterized in that, The controller is used to acquire a first test voltage between the energy storage casing and the busbar, and the voltage of the AC signal. Based on the AC component of the first test voltage and the voltage of the AC signal, it determines the insulation state between the enclosure and the energy storage unit, specifically including: The controller is used to acquire the first test voltage between the energy storage casing and the busbar, and the voltage of the AC signal; The first proportional parameter is determined based on the AC component of the first test voltage and the voltage of the AC signal. The insulation state between the enclosure and the energy storage unit is determined based on the first proportional parameter.

5. The test circuit according to claim 4, characterized in that, The controller is used to determine the insulation state between the housing and the energy storage unit based on the first proportional parameter, specifically including: The controller determines the insulation state between the enclosure and the energy storage unit based on the first proportional parameter and the first preset proportional parameter threshold.

6. The test circuit according to claim 4, characterized in that, The controller determines the insulation state between the enclosure and the energy storage unit based on the first proportional parameter, specifically including: The controller calculates the equivalent insulation resistance between the energy storage unit and the housing based on the first proportional parameter and the resistance value of the first resistor. The insulation state between the enclosure and the energy storage unit is determined based on the resistance value of the equivalent insulation resistance and the first preset insulation resistance threshold.

7. The test circuit according to claim 2, characterized in that, When the clamping circuit is located inside the converter housing, the second end of the first resistor and the first end of the second resistor are electrically connected to a single point and then electrically connected to the converter housing.

8. The test circuit according to claim 7, characterized in that, The controller is used to acquire the second test voltage between the converter housing and the busbar, and the voltage of the AC signal. Based on the AC component of the second test voltage and the voltage of the AC signal, it determines the insulation state between the housing and the converter unit, specifically including: The controller is used to acquire the second test voltage between the converter housing and the bus, and the voltage of the AC signal; The second proportional parameter is determined based on the second test voltage and the voltage of the AC signal; The insulation state between the housing and the converter unit is determined based on the second proportional parameter.

9. The test circuit according to claim 8, characterized in that, The controller is used to determine the insulation state between the enclosure and the converter unit based on the second proportional parameter, specifically including: The controller determines the insulation state between the housing and the converter unit based on the second proportional parameter and the second preset proportional parameter threshold.

10. The test circuit according to claim 8, characterized in that, The controller determines the insulation state between the housing and the converter unit based on the second proportional parameter, specifically including: The controller calculates the equivalent insulation resistance between the converter unit and the housing based on the second proportional parameter and the resistance value of the first resistor. The insulation state between the enclosure and the converter unit is determined based on the resistance value of the equivalent insulation resistance and the second preset insulation resistance threshold.

11. An energy storage system, characterized in that, The energy storage system includes three sets of high-voltage cascaded energy storage units, multiple test circuits as described in any one of claims 1 to 10, and three-phase high-voltage lines. Each set of high-voltage cascaded energy storage units includes multiple high-voltage cascaded energy storage units. Each test circuit and each high-voltage cascaded energy storage unit are electrically connected in a one-to-one correspondence. Each group of high-voltage cascaded energy storage units is electrically connected to the corresponding phase high-voltage line, and the three groups of high-voltage cascaded energy storage units are electrically connected in a star configuration.

12. The energy storage system according to claim 11, characterized in that, In each high-voltage cascaded energy storage unit, the converter unit is equipped with an AC signal terminal; In each of the high-voltage cascaded energy storage sets, the AC signal terminals of multiple high-voltage cascaded energy storage units are cascaded and electrically connected.

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