Energy storage system and insulation resistance detection device

Abstract

The utility model discloses an energy storage system and an insulation resistance detection device, the energy storage system comprises a plurality of energy storage converters connected in parallel, and each energy storage converter comprises an energy storage converter, a first controllable switch, a second controllable switch, an insulation resistance detection circuit and a third controllable switch; the positive direct-current end and the negative direct-current end of the energy storage converter are connected with the energy storage battery, the first controllable switch is arranged between the positive direct-current end and the energy storage battery or between the negative direct-current end and the energy storage battery, and the alternating-current end of the energy storage converter is connected with a power grid through the second controllable switch; the first end of the insulation impedance detection circuit is connected with the positive DC end, the second end is connected with the negative DC end, and the third end is connected with the ground through a third controllable switch. According to the invention, the ground insulation resistance value of the multi-machine parallel system can be greatly improved, and the national standard requirement is met; and a relatively low sampling resistance value can be used, so that the sampling precision is ensured, the model selection of the resistor and the design of the circuit are facilitated, and the feasibility is higher.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to an energy storage system and an insulation resistance detection device. Background Technology

[0002] For PCS (Power Conversion System), insulation resistance testing of the DC side (battery side) is required before startup. A test value lower than the specified value indicates an insulation abnormality in the system. According to GB / T34120, the insulation resistance of a PCS must not be lower than the ratio of the maximum DC voltage to 30mA (on the order of tens of kΩ). To test the insulation resistance, a resistor series and a switching switch are typically added between the positive and negative terminals of the battery input and the PE (protective earth) phase. By changing the switching switch state, different voltages relative to ground at the positive or negative terminals are obtained, and the impedance to ground is calculated.

[0003] For a PCS system with multiple units connected in parallel on the AC side, the number of units connected in parallel also affects the DC side insulation resistance to ground. The more units connected in parallel, the lower the insulation resistance. When the number of PCS units connected in parallel in a system is n, due to the presence of the detection circuit, the DC side insulation resistance to ground will become 1 / n of that of a single unit. The larger n is, the more difficult it is to meet the requirement that the total system impedance to ground be higher than 1MΩ.

[0004] Existing insulation impedance detection technologies mostly follow the approach of photovoltaic inverters. For insulation impedance detection of systems with independent DC side and multiple AC side units in parallel, in order to meet the insulation impedance of the system higher than 1MΩ, the sampling resistance value of the detection circuit must be increased. However, if the resistance value is too high, it will affect the sampling accuracy.

[0005] Patent application number CN202020094768.0 proposes a multi-machine parallel insulation impedance detection scheme based on an unbalanced bridge. However, the unbalanced bridge scheme has a large deviation in the calculated insulation impedance value when there is a deviation in voltage sampling (such as 1%). In contrast, the detection scheme based on a balanced bridge can significantly reduce the impedance calculation deviation. Utility Model Content

[0006] In view of this, the purpose of this application is to provide an energy storage system and an insulation resistance detection device to solve the problem that the insulation resistance of a multi-unit parallel PCS system is reduced due to the introduction of multiple insulation resistance detection circuits.

[0007] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows:

[0008] This application provides an energy storage system, which includes multiple energy storage converters connected in parallel. Each energy storage converter includes an energy storage converter, a first controllable switch, a second controllable switch, an insulation impedance detection circuit, and a third controllable switch.

[0009] The positive DC terminal and negative DC terminal of the energy storage converter are connected to the energy storage battery. The first controllable switch is disposed between the positive DC terminal and the energy storage battery or between the negative DC terminal and the energy storage battery. The AC terminal of the energy storage converter is connected to the power grid through the second controllable switch.

[0010] The first terminal of the insulation impedance detection circuit is connected to the positive DC terminal, the second terminal of the insulation impedance detection circuit is connected to the negative DC terminal, and the third terminal of the insulation impedance detection circuit is connected to ground through the third controllable switch.

[0011] In another aspect, this application provides an insulation impedance detection device, including an insulation impedance detection circuit and a third controllable switch, wherein the insulation impedance detection circuit includes a first resistance branch and a second resistance branch.

[0012] One end of the first resistor branch constitutes the first terminal of the insulation impedance detection circuit, one end of the second resistor branch constitutes the second terminal of the insulation impedance detection circuit, and the other end of the first resistor branch is connected to the other end of the second resistor branch to form the third terminal of the insulation impedance detection circuit. The third terminal is connected to ground through the third controllable switch.

[0013] The energy storage system and insulation impedance detection device provided above can significantly improve the ground insulation impedance value of multi-machine parallel systems, meeting national standards. Compared with the solution of simply increasing the sampling resistance value of the insulation impedance detection circuit, a relatively low sampling resistance value can be used to ensure sampling accuracy, and it is also convenient for resistor selection and circuit design, making it more feasible. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the insulation resistance detection principle provided in the embodiments of this application;

[0015] Figure 2 A schematic diagram illustrating the insulation impedance detection principle of a multi-machine parallel system with AC side parallel connection provided in this application embodiment;

[0016] Figure 3 A schematic diagram illustrating the insulation impedance detection principle of a multi-machine parallel system connected in parallel on the DC side, provided in an embodiment of this application;

[0017] Figure 4 This is a schematic diagram illustrating the insulation impedance detection principle of a multi-machine parallel system with AC and DC sides provided in an embodiment of this application.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer and more understandable, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0020] like Figure 1 The schematic diagram of the insulation impedance detection principle shown shows that Rx and Ry are the impedances of the positive and negative terminals of the battery side bus to ground, respectively. R1, Rt1, R2, and Rt2 form a bridge for insulation impedance testing. K1 and K2 are controllable switches for the detection resistors. K3 is the main switch of the detection circuit to PE. Once K3 is opened, the insulation impedance detection circuit is completely disconnected from PE, and the whole machine presents an extremely high resistance value to ground.

[0021] Both K1 and K2 can be switched, forming a balanced bridge detection scheme. A balanced bridge circuit is used to achieve higher accuracy in detecting the insulation resistance of the positive and negative busbars. For single-unit insulation resistance detection, when K1 is on and K2 is off, the following formula (1) can be obtained:

[0022]

[0023] When K1 is on and K2 is off, the following formula (2) can be obtained:

[0024]

[0025] By combining formulas (1) and (2), the values ​​of Rx and Ry can be obtained.

[0026] Based on the above insulation impedance detection principle, one embodiment of this application provides an energy storage system, which includes multiple energy storage converters connected in parallel. Each energy storage converter includes an energy storage converter, a first controllable switch, a second controllable switch, an insulation impedance detection circuit, and a third controllable switch.

[0027] The positive DC terminal and negative DC terminal of the energy storage converter are connected to the energy storage battery. The first controllable switch is disposed between the positive DC terminal and the energy storage battery or between the negative DC terminal and the energy storage battery. The AC terminal of the energy storage converter is connected to the power grid through the second controllable switch.

[0028] The first terminal of the insulation impedance detection circuit is connected to the positive DC terminal, the second terminal of the insulation impedance detection circuit is connected to the negative DC terminal, and the third terminal of the insulation impedance detection circuit is connected to ground through the third controllable switch.

[0029] In one example, each energy storage converter also includes a voltage detection circuit, one end of which is connected to the negative DC terminal and the other end of which is grounded.

[0030] In one example, the insulation impedance detection circuit includes a first resistor branch and a second resistor branch;

[0031] One end of the first resistor branch is connected to the positive DC terminal, one end of the second resistor branch is connected to the negative DC terminal, and the other end of the first resistor branch and the other end of the second resistor branch are connected together and then connected to ground through the third controllable switch.

[0032] The first resistor branch includes a first resistor, a second resistor, and a fourth controllable switch, and the second resistor branch includes a third resistor, a fourth resistor, and a fifth controllable switch.

[0033] One end of the first resistor is connected to the third controllable switch, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is connected to the positive DC terminal, and the fourth controllable switch is connected in parallel with the first resistor;

[0034] One end of the third resistor is connected to the third controllable switch, the other end of the third resistor is connected to one end of the fourth resistor, the other end of the fourth resistor is connected to the negative DC terminal, and the fifth controllable switch is connected in parallel with the fourth resistor.

[0035] In one example, the positive DC terminal of any one energy storage converter is connected to the positive DC terminal of other energy storage converters, and the corresponding negative DC terminal is connected to the negative DC terminal of other energy storage converters.

[0036] Taking two energy storage converters connected in parallel on the AC side as an example:

[0037] like Figure 2 As shown, the first energy storage converter includes an energy storage converter T1, a controllable switch Q1, and a controllable switch Q. ac-1 and controllable switch K 3-1 The positive DC terminal BUS+ and negative DC terminal BUS- of the energy storage converter T1 are connected to the energy storage battery BAT1. A controllable switch Q1 is positioned between the positive DC terminal BUS+ and the energy storage battery BAT1. The AC terminal of the energy storage converter T1 is connected to the controllable switch Q1. ac-1It is connected to the power grid. The energy storage converter T1 includes a bidirectional converter, which consists of multiple power semiconductor switches.

[0038] resistor R t1-1 Resistance R 1-1 Controllable switch K 1-1 Resistance R 2-1 Resistance R t2-1 and controllable switch K 2-1 This constitutes the insulation impedance detection circuit for the first energy storage converter. Specifically, the resistor R... t1-1 Resistance R 1-1 and controllable switch K 1-1 This forms the first resistor branch, with resistor R. t1-1 One end is connected to the controllable switch K 3-1 One end is connected to resistor R t1-1 The other end is connected to resistor R 1-1 One end is connected to resistor R 1-1 The other end is connected to the positive DC terminal BUS+, and the controllable switch K 1-1 With resistance R t1-1 Parallel connection. Resistor R 2-1 Resistance R t2-1 and controllable switch K 2-1 This forms the second resistor branch, with resistor R. 2-1 One end is connected to resistor R t1-1 One end and controllable switch K 3-1 One end is connected to resistor R 2-1 The other end is connected to resistor R t2-1 One end is connected to resistor R t2-1 The other end is connected to the negative DC terminal BUS-, and the controllable switch K 2-1 With resistance R t2-1 Parallel connection. Controllable switch K 3-1 The other end is grounded.

[0039] The voltage detection circuit of the first energy storage converter has one end connected to the negative DC terminal BUS-, and the other end connected to a controllable switch K. 3-1 Connected to the ground.

[0040] Similar to the first energy storage converter, the second energy storage converter includes an energy storage converter T2, a controllable switch Q2, and a controllable switch Q. ac-2 and controllable switch K 3-2 The positive DC terminal BUS+ and negative DC terminal BUS- of the energy storage converter T2 are connected to the energy storage battery BAT2. A controllable switch Q2 is positioned between the positive DC terminal BUS+ and the energy storage battery BAT2. The AC terminal of the energy storage converter T2 is connected via the controllable switch Q. ac-2 With controllable switch Q ac-1And grid connection, thus forming AC side parallel connection. Energy storage converter T2 includes a bidirectional converter, which is composed of multiple power semiconductor switches.

[0041] resistor R t1-2 Resistance R 1-2 Controllable switch K 1-2 Resistance R 2-2 Resistance R t2-2 and controllable switch K 2-2 This constitutes the insulation impedance detection circuit for the second energy storage converter. Specifically, the resistor R... t1-2 Resistance R 1-2 and controllable switch K 1-2 This forms the first resistor branch, with resistor R. t1-2 One end is connected to the controllable switch K 3-2 One end is connected to resistor R t1-2 The other end is connected to resistor R 1-2 One end is connected to resistor R 1-2 The other end is connected to the positive DC terminal BUS+, and the controllable switch K 1-2 With resistance R t1-2 Parallel connection. Resistor R 2-2 Resistance R t2-2 and controllable switch K 2-2 This forms the second resistor branch, with resistor R. 2-2 One end is connected to resistor R t1-2 One end and controllable switch K 3-2 One end is connected to resistor R 2-2 The other end is connected to resistor R t2-2 One end is connected to resistor R t2-2 The other end is connected to the negative DC terminal BUS-, and the controllable switch K 2-2 With resistance R t2-2 Parallel connection. Controllable switch K 3-2 The other end is grounded.

[0042] The voltage detection circuit of the second energy storage converter has one end connected to the negative DC terminal BUS-, and the other end connected to a controllable switch K. 3-2 Connected to the ground.

[0043] Before the machine is powered on, controllable switches Q1 and Q2 are open, and controllable switch K is closed. 3-1 and controllable switch K 3-2 With both circuits closed, the two energy storage converters can perform insulation resistance testing on their respective battery sides (BAT1 and BAT2). The specific testing principle and process are as follows: Figure 1 Similarly. When both energy storage converters are connected to the grid, controllable switch Q1 and controllable switch Q... ac-1 Controllable switch Q2 and controllable switch Q ac-2Both are in the closed state, and the two energy storage converters are connected in parallel through the AC side. At this time, if one of the energy storage converters is selected as the master (taking the first energy storage converter as an example), then the controllable switch K... 3-1 Keep closed, while the controllable switch K 3-2 Disconnecting the circuit means that only the insulation impedance detection circuit of the first energy storage converter is connected to the PE, and the total impedance of the parallel system to the PE is only equivalent to the impedance value of one energy storage converter to the PE.

[0044] In this way, the problem of low system-to-ground impedance caused by multiple machines in parallel can be effectively avoided; the insulation resistance to ground of the multi-machine parallel system can be significantly improved to meet the national standard requirements; compared with the solution of simply increasing the sampling resistance value of the insulation resistance detection circuit, a relatively low sampling resistance value can be used to ensure the sampling accuracy, and it is also convenient for resistor selection and circuit design, which has higher feasibility.

[0045] In one example, the second controllable switch corresponding to any one energy storage converter is connected together with the second controllable switches corresponding to other energy storage converters.

[0046] Taking two energy storage converters connected in parallel on the DC side as an example:

[0047] like Figure 3 As shown, with Figure 2 Similarly, the first energy storage converter includes an energy storage converter T1, a controllable switch Q1, and a controllable switch Q. ac-1 and controllable switch K 3-1 The corresponding insulation resistance detection circuit and voltage detection circuit; the second energy storage converter includes energy storage converter T2, controllable switch Q2, and controllable switch Q. ac-2 and controllable switch K 3-2 The corresponding insulation resistance detection circuit and voltage detection circuit.

[0048] The connection relationship of the above devices and Figure 2 Similarly, but with a difference: the system only includes the energy storage battery BAT. The positive DC terminal BUS+ and negative DC terminal BUS- of the energy storage converter T1 are connected to the energy storage battery BAT. The positive DC terminal BUS+ of the energy storage converter T2 is connected to the positive DC terminal BUS+ of the energy storage converter T1. The negative DC terminal BUS- of the energy storage converter T2 is connected to the negative DC terminal BUS- of the energy storage converter T1, thus forming a parallel DC connection.

[0049] for Figure 3 In a multi-machine parallel system, one energy storage converter is directly selected as the master (taking the first energy storage converter as an example). The controllable switch K of this master is... 3-1 Closed, and the slave's controllable switch K 3-2Disconnect. In this way, whether before power-on or during operation, only the insulation impedance detection circuit of the first energy storage converter in the system is connected to PE, and the total impedance of the parallel system to PE is only equivalent to the impedance value of one energy storage converter to PE.

[0050] In one example, the positive DC terminal of any one energy storage converter is connected to the positive DC terminal of other energy storage converters, and the corresponding negative DC terminal is connected to the negative DC terminal of other energy storage converters. The second controllable switch of any one energy storage converter is connected to the second controllable switch of other energy storage converters.

[0051] Taking two energy storage converters connected in parallel on both AC and DC sides as an example:

[0052] like Figure 4 As shown, with Figure 2 Similarly, the first energy storage converter includes an energy storage converter T1, a controllable switch Q1, and a controllable switch Q. ac-1 and controllable switch K 3-1 The corresponding insulation resistance detection circuit and voltage detection circuit; the second energy storage converter includes energy storage converter T2, controllable switch Q2, and controllable switch Q. ac-2 and controllable switch K 3-2 The corresponding insulation resistance detection circuit and voltage detection circuit.

[0053] The connection relationship of the above devices and Figure 2 Similarly, the parallel connection relationship on the DC side can be referenced. Figure 3 .

[0054] for Figure 4 Multi-machine parallel system, processing method and Figure 3 Similarly, one of the energy storage converters is directly selected as the master (taking the first energy storage converter as an example), and the controllable switch K of the master is... 3-1 Closed, and the slave's controllable switch K 3-2 disconnect.

[0055] Another embodiment of this application provides an insulation impedance detection device, including an insulation impedance detection circuit and a third controllable switch, wherein the insulation impedance detection circuit includes a first resistance branch and a second resistance branch.

[0056] One end of the first resistor branch constitutes the first terminal of the insulation impedance detection circuit, one end of the second resistor branch constitutes the second terminal of the insulation impedance detection circuit, and the other end of the first resistor branch is connected to the other end of the second resistor branch to form the third terminal of the insulation impedance detection circuit. The third terminal is connected to ground through the third controllable switch.

[0057] In one example, the first resistor branch includes a first resistor, a second resistor, and a fourth controllable switch, and the second resistor branch includes a third resistor, a fourth resistor, and a fifth controllable switch;

[0058] One end of the first resistor is connected to one end of the third resistor to form the third end, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor forms the first end of the insulation impedance detection circuit, and the fourth controllable switch is connected in parallel with the first resistor.

[0059] The other end of the third resistor is connected to one end of the fourth resistor, and the other end of the fourth resistor constitutes the second end of the insulation impedance detection circuit. The fifth controllable switch is connected in parallel with the fourth resistor.

[0060] In one example, the insulation impedance detection device further includes a voltage detection circuit for detecting the voltage of the first resistor branch or the second resistor branch.

[0061] The above insulation resistance testing devices can be combined with Figure 1 To understand, for example, resistor R1, resistor R t1 The first resistor branch is formed by controllable switch K1 (fourth controllable switch), and resistors R2 and R... t2 The second resistor branch is formed by the controllable switch K2 (the fifth controllable switch). The voltage of the first resistor branch or the second resistor branch can be detected by a voltage detection circuit, and the values ​​of Rx and Ry can be obtained according to the aforementioned formulas (1) and (2).

[0062] The above insulation resistance detection device can be used in a single energy storage converter or in multiple energy storage converters connected in parallel.

[0063] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An energy storage system, characterized in that, The energy storage system includes multiple energy storage converters connected in parallel. Each energy storage converter includes an energy storage converter, a first controllable switch, a second controllable switch, an insulation impedance detection circuit, and a third controllable switch. The positive DC terminal and negative DC terminal of the energy storage converter are connected to the energy storage battery. The first controllable switch is disposed between the positive DC terminal and the energy storage battery or between the negative DC terminal and the energy storage battery. The AC terminal of the energy storage converter is connected to the power grid through the second controllable switch. The first terminal of the insulation impedance detection circuit is connected to the positive DC terminal, the second terminal of the insulation impedance detection circuit is connected to the negative DC terminal, and the third terminal of the insulation impedance detection circuit is connected to ground through the third controllable switch.

2. The energy storage system according to claim 1, characterized in that, Each energy storage converter also includes a voltage detection circuit, one end of which is connected to the negative DC terminal, and the other end of which is connected to ground through the third controllable switch.

3. The energy storage system according to claim 1, characterized in that, The insulation impedance detection circuit includes a first resistor branch and a second resistor branch. One end of the first resistor branch is connected to the positive DC terminal, one end of the second resistor branch is connected to the negative DC terminal, and the other end of the first resistor branch and the other end of the second resistor branch are connected together and then connected to ground through the third controllable switch.

4. The energy storage system according to claim 3, characterized in that, The first resistor branch includes a first resistor, a second resistor, and a fourth controllable switch; the second resistor branch includes a third resistor, a fourth resistor, and a fifth controllable switch. One end of the first resistor is connected to the third controllable switch, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor is connected to the positive DC terminal, and the fourth controllable switch is connected in parallel with the first resistor; One end of the third resistor is connected to the third controllable switch, the other end of the third resistor is connected to one end of the fourth resistor, the other end of the fourth resistor is connected to the negative DC terminal, and the fifth controllable switch is connected in parallel with the fourth resistor.

5. The energy storage system according to claim 1, characterized in that, The positive DC terminal of any one energy storage converter is connected to the positive DC terminal of other energy storage converters, and the corresponding negative DC terminal is connected to the negative DC terminal of other energy storage converters.

6. The energy storage system according to claim 1, characterized in that, The second controllable switch corresponding to any one energy storage converter is connected together with the second controllable switches corresponding to other energy storage converters.

7. The energy storage system according to claim 1, characterized in that, The positive DC terminal of any one energy storage converter is connected to the positive DC terminal of other energy storage converters, and the corresponding negative DC terminal is connected to the negative DC terminal of other energy storage converters. The second controllable switch of any one energy storage converter is connected to the second controllable switch of other energy storage converters.

8. An insulation resistance detection device, characterized in that, It includes an insulation impedance detection circuit and a third controllable switch, wherein the insulation impedance detection circuit includes a first resistance branch and a second resistance branch; One end of the first resistor branch constitutes the first terminal of the insulation impedance detection circuit, one end of the second resistor branch constitutes the second terminal of the insulation impedance detection circuit, and the other end of the first resistor branch is connected to the other end of the second resistor branch to form the third terminal of the insulation impedance detection circuit. The third terminal is connected to ground through the third controllable switch.

9. The insulation resistance detection device according to claim 8, characterized in that, The first resistor branch includes a first resistor, a second resistor, and a fourth controllable switch; the second resistor branch includes a third resistor, a fourth resistor, and a fifth controllable switch. One end of the first resistor is connected to one end of the third resistor to form the third end, the other end of the first resistor is connected to one end of the second resistor, the other end of the second resistor forms the first end of the insulation impedance detection circuit, and the fourth controllable switch is connected in parallel with the first resistor. The other end of the third resistor is connected to one end of the fourth resistor, and the other end of the fourth resistor constitutes the second end of the insulation impedance detection circuit. The fifth controllable switch is connected in parallel with the fourth resistor.

10. The insulation resistance detection device according to claim 8, characterized in that, The insulation impedance detection device further includes a voltage detection circuit for detecting the voltage of the first resistor branch or the second resistor branch.

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