Insulation self-checking device, control method for insulation self-checking device, and power converter

Abstract

The application discloses an insulation self-checking device, a control method of the insulation self-checking device and a power converter, and belongs to the technical field of insulation detection. The power converter has a DC bus, and the insulation self-checking device comprises: an impedance unit connected with the DC bus, capable of forming an impedance between the DC bus and a grounding node in a switchable manner, and the impedance value is adjustable; an insulation detection circuit for detecting an equivalent insulation resistance value of the DC side of the power converter; a control circuit electrically connected with the impedance unit and the insulation detection circuit, and in the case that the equivalent insulation resistance value is greater than or equal to a preset insulation resistance value, the control circuit controls the impedance unit to connect an impedance element with an impedance value less than the equivalent insulation resistance value between the DC bus and the grounding node, and enables the power converter to perform a grid-connected operation based on a first impedance value and an insulation protection strategy. The scene of the DC side insulation deterioration test is actively constructed to verify whether the insulation self-checking function of the power converter is normal in the case that the DC side does not meet the insulation requirements.

Description

Technical Field

[0001] This application belongs to the field of insulation testing technology, and in particular relates to an insulation self-testing device, a control method for the insulation self-testing device, and a power converter. Background Technology

[0002] With the development of technology, automated control systems have been widely used in various fields. In power systems, power converters typically require DC insulation testing before grid connection. If the insulation requirements are met, the power converter is controlled to connect to the grid, ensuring its safe operation.

[0003] However, existing insulation resistance testing technologies mostly use passive monitoring methods to calculate the equivalent insulation resistance value, but they cannot actively simulate insulation degradation scenarios under non-fault conditions, making it difficult to fully verify whether the testing mechanism is effective under various operating conditions. Summary of the Invention

[0004] This application aims to at least solve one of the technical problems existing in the prior art. To this end, this application proposes an insulation self-test device, a control method for the insulation self-test device, and a power converter, which actively constructs a scenario for DC-side insulation degradation testing to verify whether the insulation self-test function of the power converter is normal when the DC-side insulation requirements are not met.

[0005] In a first aspect, this application provides an insulation self-testing device applied to a power converter, the power converter having a DC bus, the insulation self-testing device comprising:

[0006] An impedance unit, connected to the DC bus, is configured to switchably form an impedance between the DC bus and the grounding node, and the impedance value is adjustable.

[0007] An insulation detection circuit is electrically connected to the DC bus and is configured to detect the equivalent insulation resistance on the DC side of the power converter.

[0008] The control circuit is electrically connected to the impedance unit and the insulation detection circuit respectively. The control circuit is configured to apply a control signal to the impedance unit when the equivalent insulation resistance is greater than or equal to the preset insulation resistance, so that the impedance unit connects an impedance element with a first impedance value between the DC bus and the grounding node, and enables the power converter to perform grid connection operation based on the first impedance value and the insulation protection strategy. The first impedance value is less than the equivalent insulation resistance.

[0009] According to one embodiment of this application, the DC bus includes a positive bus and a negative bus, and the impedance unit includes:

[0010] The impedance switching circuit has its first terminal electrically connected to the positive busbar and its second terminal electrically connected to the negative busbar.

[0011] The first switching circuit has a first terminal electrically connected to the positive busbar and a second terminal electrically connected to the grounding node.

[0012] The second switching circuit has its first terminal electrically connected to the negative busbar and its second terminal electrically connected to the grounding node.

[0013] The control circuit is connected to the drive terminals of the first switch circuit and the second switch circuit respectively, and is configured to control the second switch circuit to conduct and control the first switch circuit to disconnect when calculating the equivalent insulation resistance of the positive bus; and to control the first switch circuit to conduct and control the second switch circuit to disconnect when calculating the equivalent insulation resistance of the negative bus.

[0014] According to one embodiment of this application, the impedance switching circuit includes:

[0015] Multiple impedance branches are connected in parallel and electrically connected between the positive bus and the negative bus. Each impedance branch includes a first switch and a resistor connected in series. The resistance values ​​of the resistors in at least two impedance branches are different.

[0016] The control circuit is electrically connected to the drive terminal of each first switch and is configured to control the corresponding first switch to turn on according to the equivalent insulation resistance value, so as to connect a resistor with a first impedance value between the DC bus and the grounding node.

[0017] According to one embodiment of this application, the impedance switching circuit includes:

[0018] The second switch, the first end of the second switch is electrically connected to the positive busbar;

[0019] The digital potentiometer has its first terminal electrically connected to the first terminal of the second switch, and its second terminal electrically connected to the negative busbar.

[0020] The control circuit is electrically connected to the adjustment terminal of the digital potentiometer. The control circuit is configured to control the second switch to turn on and adjust the resistance of the digital potentiometer to the first impedance value when the equivalent insulation resistance is greater than or equal to the preset insulation resistance.

[0021] According to one embodiment of this application, the DC bus includes a positive bus and a negative bus, and the impedance unit includes:

[0022] The first impedance switching circuit is electrically connected between the positive bus and the grounding node.

[0023] The second impedance switching circuit is electrically connected between the negative bus and the grounding node.

[0024] The control circuit is electrically connected to the first impedance unit and the second impedance unit respectively. The control circuit is configured to apply a first control signal to the first impedance switching circuit when the equivalent insulation resistance of the positive bus is greater than or equal to the preset insulation resistance; and / or apply a second control signal to the second impedance switching circuit when the equivalent insulation resistance of the negative bus is greater than or equal to the preset insulation resistance.

[0025] Secondly, this application provides a control method for an insulation self-testing device, applied to the aforementioned insulation self-testing device, the control method comprising:

[0026] Obtain the equivalent insulation resistance value of the DC side of the power converter;

[0027] When the equivalent insulation resistance is greater than or equal to the preset insulation resistance, a first control signal is applied to the impedance unit so that the impedance unit connects an impedance element with a first impedance value between the DC bus and the grounding node. The first impedance value is less than the equivalent insulation resistance.

[0028] The control power converter performs grid connection operation based on the first impedance value and the insulation protection strategy;

[0029] If the grid connection status feedback signal of the power converter is a signal that prohibits grid connection, the insulation self-test function of the power converter is determined to be normal.

[0030] According to one embodiment of this application, after determining that the insulation self-test function of the power converter is normal, the method further includes:

[0031] A second control signal is applied to the impedance unit so that the impedance unit connects an impedance element with a second impedance value between the DC bus and the grounding node. The second impedance value is greater than the equivalent insulation resistance value.

[0032] The control power converter performs grid-connected operation based on the second impedance value and insulation protection strategy;

[0033] If the power converter provides a signal indicating that grid connection is permitted, the power converter's grid connection function is considered to be normal.

[0034] According to one embodiment of this application, after the control power converter performs grid connection operation based on a first impedance value and an insulation protection strategy, it further includes:

[0035] If the power converter sends a signal indicating that grid connection is permitted, the insulation self-test function of the power converter is deemed abnormal, and the power converter is controlled to stop operation.

[0036] According to one embodiment of this application, after obtaining the equivalent insulation resistance value of the DC side of the power converter, the method further includes:

[0037] If the equivalent insulation resistance is less than the preset insulation resistance, the DC side of the power converter is determined to not meet the insulation requirements.

[0038] Thirdly, this application provides a power converter including the aforementioned insulation self-test device.

[0039] According to several embodiments of the present application, the insulation self-test device, the control method of the insulation self-test device, and the power converter, when the equivalent insulation resistance is greater than or equal to the preset insulation resistance, the control circuit controls the impedance unit to connect an impedance element with a resistance value less than the equivalent insulation resistance between the DC bus and the grounding node, actively constructing a scenario for DC side insulation degradation test, so as to verify whether the insulation self-test function of the power converter is normal when the insulation requirements on the DC side are not met.

[0040] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0041] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0042] Figure 1 This is a structural block diagram of the insulation self-testing device provided in the embodiments of this application;

[0043] Figure 2 This is one of the circuit diagrams of the insulation self-test device provided in the embodiments of this application;

[0044] Figure 3 This is the second circuit diagram of the insulation self-test device provided in the embodiments of this application;

[0045] Figure 4 This is the third circuit diagram of the insulation self-test device provided in the embodiments of this application;

[0046] Figure 5 This is the fourth circuit diagram of the insulation self-test device provided in the embodiments of this application;

[0047] Figure 6 This is a flowchart of the control method for the insulation self-test device provided in the embodiments of this application.

[0048] Figure label:

[0049] Insulation self-test device 100, impedance unit 110, first impedance switching circuit 111, second impedance switching circuit 112, impedance switching circuit 113, insulation detection circuit 120, control circuit 130, first switch circuit 141, second switch circuit 142, power converter 200, DC bus Ubus, positive bus Ubus+, negative bus Ubus-, grounding node GND, first to second switches K1~K2, resistor R, digital potentiometer Rd. Detailed Implementation

[0050] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0051] In the following description, a "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by an electrical or electromagnetic link. When an element or circuit is said to be "coupled to" or "connected to" another element, or when an element / circuit is said to be "coupled at" or "connected at" two nodes, it can be directly coupled to or connected to the other element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there are no intermediate elements between them.

[0052] In the description, the terms "first," "second," etc., are used to distinguish similar objects, not to describe a specific order or sequence. It should be understood that such numerical descriptors can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class, not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0053] Furthermore, the use of terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0054] Power converters are primarily used to convert electrical energy to meet the needs of different loads. The specific type of power converter can be selected based on the actual application scenario and is not limited here. For example, a power converter can be an inverter. In some applications, inverters need to connect the electrical energy stored in DC power sources (such as solar photovoltaic panels, batteries, etc.) to the AC power grid. The DC side of the inverter is connected to the DC power source. Before the inverter is officially put into grid-connected operation, the insulation condition of its DC side needs to be tested. This is because the quality of the DC side insulation directly affects the safety and reliability of the system. If there are problems with the DC side insulation, it may lead to leakage current, which will not only reduce the efficiency of the system but also pose serious safety hazards to operators and equipment.

[0055] In related technologies, insulation impedance detection often uses passive monitoring methods to calculate the equivalent insulation resistance value, but it cannot actively simulate insulation degradation scenarios under non-fault conditions, making it difficult to fully verify whether the detection mechanism is effective under various operating conditions.

[0056] Figure 1 This is a structural block diagram of the insulation self-testing device provided in an embodiment of this application. (Refer to...) Figure 1 One embodiment of this application proposes an insulation self-test device 100, which is applied to a power converter 200. The power converter 200 has a DC bus Ubus. The insulation self-test device 100 includes an impedance unit 110, an insulation detection circuit 120, and a control circuit 130. Impedance unit 110 is connected to the DC bus Ubus. Impedance unit 110 is configured to switchably form an impedance between the DC bus Ubus and the grounding node GND, and the impedance value is adjustable. Insulation detection circuit 120 is electrically connected to the DC bus Ubus. Insulation detection circuit 120 is configured to detect the equivalent insulation resistance value on the DC side of power converter 200. Control circuit 130 is electrically connected to insulation detection circuit 120 and impedance unit 110 respectively. Control circuit 130 is configured to apply a control signal to impedance unit 110 when the equivalent insulation resistance value is greater than or equal to a preset insulation resistance value, so that impedance unit 110 connects an impedance element with a first impedance value between DC bus Ubus and grounding node GND, and causes power converter 200 to perform grid connection operation based on the first impedance value and insulation protection strategy. The first impedance value is less than the equivalent insulation resistance value.

[0057] The DC bus Ubus is the conductive path in the power converter 200 used to transmit and collect DC power. Its insulation performance directly affects the reliability and safety of the entire power converter 200.

[0058] It should be noted that the DC bus Ubus includes the positive bus Ubus+ and the negative bus Ubus-. The insulation detection circuit 120 of this application can be used to detect the equivalent insulation resistance of the positive bus Ubus+ to ground, and it can also be used to detect the equivalent insulation resistance of the negative bus Ubus- to ground. The following explanation uses the insulation self-test device 100 for detecting the equivalent insulation resistance of the positive bus Ubus+ as an example.

[0059] Impedance unit 110 is electrically connected between the positive busbar Ubus+ and the grounding node GND. Impedance unit 110 can provide different resistance values. When it receives a control signal from the control circuit 130, impedance unit 110 responds to the control signal and precisely adjusts the actual impedance value connected to the circuit.

[0060] The insulation detection circuit 120 is electrically connected to the DC bus Ubus and is mainly used to collect electrical parameters from the DC side of the power converter 200, including the voltage of the positive bus Ubus+ to ground and the current flowing through the positive bus Ubus+. Based on the collected information, it calculates the equivalent insulation resistance of the positive bus Ubus+ to ground. It should be noted that the specific method used by the insulation detection circuit 120 to calculate the equivalent insulation resistance can be selected according to the actual application scenario. For example, the equivalent insulation resistance of the bus to ground can be calculated using a balanced bridge or an unbalanced bridge. There are already relatively mature solutions for calculating the equivalent insulation resistance in related technologies, which will not be elaborated here.

[0061] After calculating the equivalent insulation resistance, the control circuit 130 compares the equivalent insulation resistance with a preset insulation resistance. The preset insulation resistance is a reference value predetermined based on the design requirements of the power converter 200 and relevant standards, representing the minimum insulation level that the DC bus Ubus should meet. When the equivalent insulation resistance is greater than or equal to the preset insulation resistance, it indicates that the equivalent insulation resistance of the positive bus Ubus+ to ground is greater than or equal to the preset insulation resistance. Therefore, the control circuit 130 determines that the positive bus Ubus+ of the power converter 200 meets the insulation requirements.

[0062] When the positive bus Ubus+ of the power converter 200 meets the insulation requirements, the control circuit 130 applies a corresponding control signal to the impedance unit 110 according to the equivalent insulation resistance value. This causes the impedance unit 110 to connect an impedance element with an impedance value less than the equivalent insulation resistance value between the DC bus and the grounding node, in order to simulate the scenario of DC side insulation degradation test.

[0063] As an example, the preset insulation resistance of the power converter 200 is 40KΩ. The insulation detection circuit 120 calculates the equivalent insulation resistance of the positive bus Ubus+ to ground based on the electrical parameters of the DC side of the power converter 200, which is 40KΩ, indicating that the positive bus Ubus+ of the power converter 200 meets the insulation requirements. The control circuit 130 applies a control signal to the impedance unit 110, causing the impedance unit 110 to connect a 35KΩ impedance element between the positive bus Ubus+ and the grounding node GND, simulating the scenario of insulation degradation test on the DC side of the power converter 200.

[0064] The insulation protection strategy refers to the insulation protection mechanism of the power converter 200 itself. That is, if the insulation requirements on the DC side are not met, the power converter 200 will not connect to the grid even if a grid connection control command is received. After connecting an impedance element with an impedance value less than the equivalent insulation resistance between the positive bus Ubus+ and the grounding node GND, the power converter 200 performs grid connection operation based on the insulation protection strategy. The grid connection status feedback signal of the power converter is then acquired. If the power converter 200 feeds back a signal prohibiting grid connection, it indicates that the power converter 200 can avoid grid connection when the insulation requirements on the DC side are not met, meaning that the insulation self-test function of the power converter 200 is normal.

[0065] According to the insulation self-test device 100 of this application, when the equivalent insulation resistance is greater than or equal to the preset insulation resistance, the control circuit 130 controls the impedance unit 110 to connect an impedance element with a resistance value less than the equivalent insulation resistance between the DC bus and the grounding node, actively constructing a scenario for DC side insulation degradation test, so as to verify whether the insulation self-test function of the power converter 200 is normal when the insulation requirements on the DC side are not met.

[0066] Figure 2 This is a circuit diagram of the insulation self-test device 100 provided in an embodiment of this application. (Refer to...) Figure 2In some embodiments, the DC bus Ubus includes a positive bus Ubus+ and a negative bus Ubus-, and the impedance unit 110 includes an impedance switching circuit 113, a first switching circuit 141 and a second switching circuit 142. The first terminal of the impedance switching circuit 113 is electrically connected to the positive bus Ubus+, and the second terminal of the impedance switching circuit is electrically connected to the negative bus Ubus-. The first terminal of the first switching circuit 141 is electrically connected to the positive bus Ubus+, and the second terminal of the first switching circuit 141 is electrically connected to the grounding node GND. The first terminal of the second switching circuit 142 is electrically connected to the negative bus Ubus-, and the second terminal of the second switching circuit 142 is electrically connected to the grounding node GND. The control circuit 130 is connected to the drive terminals of the first switching circuit 141 and the second switching circuit 142 respectively, and is configured to control the second switching circuit 142 to conduct and control the first switching circuit 141 to disconnect when the equivalent insulation resistance of the positive bus Ubus+ is calculated, and to control the first switching circuit 141 to conduct and control the second switching circuit 142 to disconnect when the equivalent insulation resistance of the negative bus Ubus- is calculated.

[0067] Impedance switching circuit 113 is electrically connected between the positive bus Ubus+ and the negative bus Ubus-. The first switching circuit 141 and the second switching circuit 142 can switch between on and off modes.

[0068] The first switching circuit 141 is electrically connected between the positive busbar Ubus+ and the grounding node GND. When the first switching circuit 141 is turned on and the second switching circuit 142 is turned off, the positive busbar Ubus+ and the grounding node GND are connected. The impedance switching circuit 113 is equivalent to being connected between the negative busbar Ubus- and the grounding node GND. The insulation detection circuit 120 calculates the equivalent insulation resistance of the negative busbar Ubus-.

[0069] The second switching circuit 142 is electrically connected between the negative busbar Ubus- and the grounding node GND. When the first switching circuit 141 is open and the second switching circuit 142 is on, the negative busbar Ubus- and the grounding node GND are connected. The impedance switching circuit 113 is equivalent to being connected between the positive busbar Ubus+ and the grounding node GND. The insulation detection circuit 120 calculates the equivalent insulation resistance of the positive busbar Ubus+.

[0070] The specific structure of the first switching circuit 141 and the second switching circuit 142 can be determined according to the actual application scenario, and is not limited here. For example, the first switching circuit 141 may include a first relay, and the second switching circuit 142 may include a second relay.

[0071] By controlling the first switching circuit 141 and the second switching circuit 142 to switch between the on mode and the off mode, it is possible to detect whether the positive bus Ubus+ and the negative bus Ubus- meet the insulation requirements respectively, and only one calculation is needed to calculate the equivalent insulation resistance value of the negative bus Ubus-, which can reduce costs.

[0072] Furthermore, when both the first switching circuit 141 and the second switching circuit 142 are disconnected, the insulation detection circuit 120 can calculate the equivalent insulation resistance between the positive busbar Ubus+ and the negative busbar Ubus- based on the electrical parameters detected by the insulation detection circuit 120. According to the aforementioned insulation detection principle, it is possible to detect whether the insulation requirements between the positive busbar Ubus+ and the negative busbar Ubus- are met.

[0073] Figure 3 This is a circuit diagram of the insulation self-test device 100 provided in an embodiment of this application. (Refer to...) Figure 3 In some embodiments, the impedance switching circuit 113 includes multiple impedance branches, each impedance branch is connected in parallel and electrically connected between the positive bus Ubus+ and the negative bus Ubus-. Each impedance branch includes a first switch K1 and a resistor R connected in series, and the resistance values ​​of the resistor R are different in at least two impedance branches. The control circuit 130 is electrically connected to the drive terminal of each first switch K1 and is configured to control the corresponding first switch K1 to conduct according to the equivalent insulation resistance value, so as to connect a resistor with a first impedance value between the DC bus Ubus and the ground node GND.

[0074] Multiple impedance branches are connected in parallel and are electrically connected together between the DC bus Ubus and the grounding node GND, so that each impedance branch can be independently connected to the electrical loop between the DC bus Ubus and the ground.

[0075] Each impedance branch consists of a first switch K1 and a resistor R connected in series. The first switch K1 is mainly used to control the connection or disconnection of the impedance branch from the electrical circuit between the DC bus Ubus and ground. When the first switch K1 is on, the resistor R connected in series with it is connected to the electrical circuit between the DC bus Ubus and ground. When the first switch K1 is off, the resistor R connected in series with it is disconnected from the electrical circuit between the DC bus Ubus and ground.

[0076] The specific type of the first switch K1 can be selected according to the actual application scenario, and is not limited here. For example, the first switch K1 can be a power switching device such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or IGBT (Insulated-Gate Bipolar Transistor), or it can be a relay or contactor.

[0077] The resistance R determines the value of the impedance branch. At least two impedance branches must have different values ​​of R, so that the impedance branch with a resistance value less than the equivalent insulation resistance can be selected for conduction according to the actual insulation testing requirements.

[0078] In some embodiments, the resistance values ​​of resistors R in different impedance branches are different. This allows each impedance branch to provide a different impedance value, thereby providing the control circuit 130 with more options and the ability to flexibly adjust the impedance value connected to the circuit.

[0079] In some embodiments, the resistance R in some impedance branches has the same value. When one impedance branch fails, the first switch K1 in the impedance branch with the same resistance value can be turned on, thereby improving the reliability of the insulation self-test device.

[0080] It is understandable that the number of resistors R in an impedance branch can be selected according to the actual application scenario, and there is no limitation here. For example, an impedance branch may include one resistor R, which is connected in series with the first switch K1; an impedance branch may also include two or three resistors R connected in series, each resistor R being connected in series with each other and connected in series with the first switch K1.

[0081] The control circuit 130 is electrically connected to the drive terminal of each first switch K1, and achieves flexible switching of each impedance branch by controlling the conduction state of the first switch K1. During the insulation detection process, the control circuit 130 selects and controls the corresponding first switch K1 to conduct based on the calculated equivalent insulation resistance value.

[0082] The impedance branches are connected in parallel with different resistance values, which enhances the redundancy and reliability of the insulation self-testing device 100. Even if one impedance branch fails, the other impedance branches can still work normally, ensuring the continuity and stability of the insulation testing process.

[0083] Furthermore, this structural design of the impedance switching circuit 113 facilitates system expansion and maintenance. When more impedance branches need to be added to meet higher detection requirements, the new impedance branches can simply be connected in parallel without requiring large-scale modifications to the entire system. Similarly, when an impedance branch fails and requires repair, it can be easily isolated from the circuit for individual inspection and replacement without affecting the normal operation of other impedance branches.

[0084] Figure 4 This is a circuit diagram of the insulation self-test device 100 provided in an embodiment of this application. (Refer to...) Figure 4 In some embodiments, the impedance unit 110 includes a second switch K2 and a digital potentiometer Rd. The first terminal of the second switch K2 is electrically connected to the positive bus Ubus+; the first terminal of the digital potentiometer Rd is electrically connected to the first terminal of the second switch K2, and the second terminal of the digital potentiometer Rd is electrically connected to the negative bus Ubus-; the control circuit 130 is electrically connected to the adjustment terminal of the digital potentiometer Rd, and the control circuit 130 is configured to control the second switch K2 to conduct and adjust the resistance of the digital potentiometer Rd to a first impedance value when the equivalent insulation resistance is greater than or equal to a preset insulation resistance value.

[0085] The second switch K2 and the digital potentiometer Rd are connected in series between the positive bus Ubus+ and the negative bus Ubus-. The second switch K2 is mainly used to control the connection or disconnection of the digital potentiometer Rd from the electrical circuit between the positive bus Ubus+ and the negative bus Ubus-. When the second switch K2 is on, the digital potentiometer Rd is connected to the electrical circuit between the positive bus Ubus+ and the negative bus Ubus-; when the second switch K2 is off, the digital potentiometer Rd is disconnected from the electrical circuit between the positive bus Ubus+ and the negative bus Ubus-.

[0086] The specific type of the second switch K2 can be selected according to the actual application scenario, and is not limited here. For example, the second switch K2 can be a power switching device such as MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) or IGBT (Insulated-Gate Bipolar Transistor), or it can be a relay or contactor.

[0087] When the second switch K2 is turned on, the digital potentiometer Rd can be directly connected between the positive bus Ubus+ and the negative bus Ubus-. The digital potentiometer Rd has an adjustable resistance value, which can be adjusted by the control signal applied by the control circuit 130.

[0088] Control circuit 130 is electrically connected to the adjustment terminal of digital potentiometer Rd. Control circuit 130 can directly adjust the resistance value of digital potentiometer Rd by applying a control signal. Control circuit 130 controls the second switch K2 to conduct based on the equivalent insulation resistance value calculated by insulation detection circuit 120, thus connecting digital potentiometer Rd to the electrical loop between positive busbar Ubus+ and negative busbar Ubus-. Control circuit 130 can precisely adjust the resistance value of digital potentiometer Rd according to the equivalent insulation resistance value to achieve the desired first impedance value. The use of digital potentiometer Rd simplifies the circuit structure and improves the reliability and stability of the system.

[0089] Figure 5 This is a circuit diagram of the insulation self-test device 100 provided in an embodiment of this application. (Refer to...) Figure 5 In some embodiments, the DC bus Ubus includes a positive bus Ubus+ and a negative bus Ubus-, and the impedance unit 110 includes a first impedance switching circuit 111 and a second impedance switching circuit 112. The first impedance switching circuit 111 is electrically connected between the positive bus Ubus+ and the ground node GND; the second impedance switching circuit 112 is electrically connected between the negative bus Ubus- and the ground node GND; the main control unit is electrically connected to both the first impedance switching circuit 111 and the second impedance switching circuit 112, and is configured to apply a first control signal to the first impedance switching circuit 111 when the equivalent insulation resistance of the positive bus Ubus+ is greater than or equal to a preset insulation resistance value; and / or apply a second control signal to the second impedance switching circuit 112 when the equivalent insulation resistance of the negative bus Ubus- is greater than or equal to the preset insulation resistance value.

[0090] The first impedance switching circuit 111 is electrically connected between the positive bus Ubus+ and the grounding node GND. The insulation detection circuit 120 can calculate the first equivalent insulation resistance value of the positive bus Ubus+ and control the first impedance switching circuit 111 to provide an impedance element that is less than the first equivalent insulation resistance value to simulate the scenario of insulation degradation of the positive bus Ubus+.

[0091] The second impedance switching circuit 112 is electrically connected between the negative bus Ubus- and the grounding node GND. The insulation detection circuit 120 can calculate the second equivalent insulation resistance value of the negative bus Ubus- and control the second impedance switching circuit 112 to provide an impedance element that is less than the second equivalent insulation resistance value to simulate the scenario of insulation degradation of the negative bus Ubus-.

[0092] Impedance switching circuits are installed between the positive busbar Ubus+ and the grounding node GND, and between the negative busbar Ubus- and the grounding node GND, respectively. This allows for a comprehensive evaluation of the insulation performance of the entire DC busbar Ubus. Furthermore, the impedance switching circuits between the positive and negative busesbar Ubus- are independent and can be controlled and adjusted separately, reducing interference between the two busesbars and improving the accuracy and reliability of the detection.

[0093] Figure 6 This is a flowchart of the control method for the insulation self-testing device 100 provided in an embodiment of this application. (Refer to...) Figure 6 One embodiment of this application proposes a control method for an insulation self-test device 100, which is applied to the aforementioned insulation self-test device 100. The control method includes steps 10, 20, 30, 40 and 50.

[0094] Step 10: Obtain the equivalent insulation resistance value of the DC side of the power converter 200;

[0095] Step 20: When the equivalent insulation resistance is greater than or equal to the preset insulation resistance, apply a first control signal to the impedance unit 110 so that the impedance unit 110 connects an impedance element with a first impedance value between the DC bus Ubus and the grounding node GND. The first impedance value is less than the equivalent insulation resistance.

[0096] Step 30: Control the power converter 200 to perform grid connection operation based on the first impedance value and insulation protection strategy;

[0097] Step 40: If the grid connection status feedback signal of the power converter 200 is a signal that prohibits grid connection, it is determined that the insulation self-test function of the power converter 200 is normal.

[0098] The execution subject of the control method of the insulation self-test device 100 provided in the embodiments of this application can be the aforementioned control circuit 130 or a functional module or functional entity in the control circuit 130 that can implement the control method. The control method of the insulation self-test device 100 provided in the embodiments of this application will be described below with the control circuit 130 as the execution subject as an example.

[0099] The DC bus Ubus includes the positive bus Ubus+ and the negative bus Ubus-. The calculation of the equivalent insulation resistance between the DC bus Ubus and the grounding node GND includes the calculation of the equivalent insulation resistance between the positive bus Ubus+ and the grounding node GND, as well as the calculation of the equivalent insulation resistance between the negative bus Ubus- and the grounding node GND, and may also include the calculation of the equivalent insulation resistance between the positive bus Ubus+ and the negative bus Ubus-. The following explanation uses the calculation of the equivalent insulation resistance between the positive bus Ubus+ and the grounding node GND, simulating a scenario of insulation degradation of the positive bus Ubus+, as an example. There are already relatively mature technologies for calculating the equivalent insulation resistance, which will not be elaborated upon here.

[0100] After calculating the equivalent insulation resistance of the positive bus Ubus+, the control circuit 130 compares the equivalent insulation resistance with a preset insulation resistance value. The preset insulation resistance value is a reference value predetermined based on the design requirements of the power converter 200 and relevant standards; it represents the minimum insulation level that the DC bus Ubus should meet. Once the type and specifications of the power converter 200 are determined, its preset insulation resistance value is also fixed. When the equivalent insulation resistance value is greater than or equal to the preset insulation resistance value, it indicates that the equivalent insulation resistance of the positive bus Ubus+ to ground is greater than or equal to the preset insulation resistance value. Therefore, the control circuit 130 determines that the positive bus Ubus+ of the power converter 200 meets the insulation requirements.

[0101] The control circuit 130 controls the impedance unit 110 to connect an impedance element with an equivalent insulation resistance value smaller than that of the positive busbar Ubus+ between the positive busbar Ubus+ and the grounding node GND, thereby simulating the scenario of insulation degradation of the positive busbar Ubus+.

[0102] After connecting an impedance element with an impedance value less than the equivalent insulation resistance between the positive busbar Ubus+ and the grounding node GND, the power converter 200 performs grid connection operation based on the insulation protection strategy. The grid connection status feedback signal of the power converter is then acquired. If the power converter 200 feeds back a signal prohibiting grid connection, it indicates that the power converter 200 can avoid grid connection when the insulation requirements on the DC side are not met, meaning that the insulation self-test function of the power converter 200 is normal.

[0103] According to the control method of the insulation self-test device 100 of this application, when the equivalent insulation resistance is greater than or equal to the preset insulation resistance, the control circuit 130 controls the impedance unit 110 to connect an impedance element with a resistance value less than the equivalent insulation resistance between the DC bus and the grounding node, actively constructing a scenario for DC side insulation degradation test, so as to verify whether the insulation self-test function of the power converter 200 is normal when the insulation requirements on the DC side are not met.

[0104] In some embodiments, after determining that the insulation self-test function of the power converter 200 is normal, the method further includes: applying a second control signal to the impedance unit 110 to connect an impedance element with a second impedance value between the DC bus Ubus and the grounding node GND, the second impedance value being greater than the equivalent insulation resistance value; controlling the power converter 200 to perform grid connection operation based on the second impedance value and the insulation protection strategy; and determining that the grid connection function of the power converter 200 is normal when the power converter 200 provides a signal that allows grid connection.

[0105] After confirming that the insulation self-test function of the power converter is normal, an impedance element with a resistance greater than the equivalent insulation resistance is connected between the DC bus Ubus and the grounding node GND. Under these conditions, the DC side of the power converter 200 meets the insulation requirements. At this point, the power converter is controlled to perform grid connection operation. If the power converter feeds back a grid connection permission signal, it further verifies that the insulation self-test function is normal and indicates that the power converter 200 has the capability for normal grid connection. Controlling the power converter 200 to connect to the grid at this time improves its safety and reliability.

[0106] In some embodiments, after the power converter 200 performs grid connection operation based on the first impedance value and the insulation protection strategy, the method further includes: if the power converter 200 feeds back a signal that allows grid connection, determining that the insulation self-test function of the power converter 200 is abnormal, and controlling the power converter 200 to stop operating.

[0107] When the equivalent insulation impedance on the DC side of the power converter 200 is the first impedance value, it indicates that the power converter 200 is in an insulation degradation scenario. If the power converter 200 is allowed to connect to the grid at this time, it indicates that the insulation self-test function of the power converter 200 is abnormal. At this time, the power converter 200 should be stopped and repaired in time to reduce the risk of further damage to the power converter 200.

[0108] In some embodiments, after obtaining the equivalent insulation resistance value of the DC side of the power converter 200, the method further includes: if the equivalent insulation resistance value is less than a preset insulation resistance value, determining that the DC side of the power converter 200 does not meet the insulation requirements.

[0109] The calculated equivalent insulation resistance reflects the insulation status of the DC side during the operation of the power converter 200. If the equivalent insulation resistance is less than the preset insulation resistance, it indicates that the DC side of the power converter 200 does not meet the insulation requirements. If either the positive bus Ubus+ or the negative bus Ubus- fails to meet the insulation requirements, or if both Ubus+ and Ubus- fail to meet the insulation requirements, serious faults such as short circuits and leakage may occur, posing a threat to the safety of electrical equipment and personnel. Upon determining that the DC side does not meet the insulation requirements, the control circuit 130 will quickly respond by generating a fault signal.

[0110] In some embodiments, the power converter 200 also includes a host computer. The control signals generated by the control circuit 130 can transmit fault signals to the host computer through a dedicated communication channel, such as RS485 communication protocol or CAN bus, to facilitate quick location and identification of faults by staff.

[0111] While generating a fault signal, the control circuit 130 controls the power switching devices in the power converter 200 to disconnect, cutting off the input and output circuits, so that the power converter 200 can stop operating safely and smoothly, reducing the risk of further deterioration of the fault.

[0112] One embodiment of this application provides a power converter 200, which includes the aforementioned insulation self-test device 100.

[0113] The specific structure and working principle of the insulation self-test device 100 can be referred to the aforementioned embodiments, and will not be repeated here.

[0114] According to the power converter 200 of this application, when the equivalent insulation resistance is greater than or equal to the preset insulation resistance, the control circuit 130 controls the impedance unit 110 to connect an impedance element with a resistance value less than the equivalent insulation resistance between the DC bus and the grounding node, actively constructing a scenario for DC side insulation degradation test, so as to verify whether the insulation self-test function of the power converter 200 is normal when the insulation requirements on the DC side are not met.

[0115] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. An insulation self-testing device, characterized in that, The insulation self-test device is applied to a power converter having a DC bus and includes: An impedance unit is connected to the DC bus, and the impedance unit is configured to switchably form an impedance between the DC bus and the grounding node, and the impedance value is adjustable. An insulation detection circuit is electrically connected to the DC bus, and the insulation detection circuit is configured to detect the equivalent insulation resistance value of the DC side of the power converter; A control circuit is electrically connected to the impedance unit and the insulation detection circuit, respectively. The control circuit is configured to apply a control signal to the impedance unit when the equivalent insulation resistance is greater than or equal to a preset insulation resistance, so that the impedance unit connects an impedance element with a first impedance value between the DC bus and the grounding node, and causes the power converter to perform grid connection operation based on the first impedance value and the insulation protection strategy, wherein the first impedance value is less than the equivalent insulation resistance.

2. The insulation self-testing device according to claim 1, characterized in that, The DC bus includes a positive bus and a negative bus, and the impedance unit includes: An impedance switching circuit is provided, wherein a first terminal of the impedance switching circuit is electrically connected to the positive busbar, and a second terminal of the impedance switching circuit is electrically connected to the negative busbar. A first switching circuit, wherein a first terminal of the first switching circuit is electrically connected to the positive busbar, and a second terminal of the first switching circuit is electrically connected to the grounding node; The second switching circuit has a first terminal electrically connected to the negative busbar and a second terminal electrically connected to the grounding node. The control circuit is connected to the drive terminals of the first switch circuit and the second switch circuit respectively, and is configured to control the second switch circuit to conduct and control the first switch circuit to disconnect when calculating the equivalent insulation resistance of the positive bus; and to control the first switch circuit to conduct and control the second switch circuit to disconnect when calculating the equivalent insulation resistance of the negative bus.

3. The insulation self-testing device according to claim 2, characterized in that, The impedance switching circuit includes: Multiple impedance branches are connected in parallel and electrically connected between the positive bus and the negative bus. Each impedance branch includes a first switch and a resistor connected in series, and the resistance values ​​of the resistors in at least two of the impedance branches are different. The control circuit is electrically connected to the drive terminal of each of the first switches and is configured to control the corresponding first switch to turn on according to the equivalent insulation resistance value, so as to connect the resistor with the first impedance value between the DC bus and the grounding node.

4. The insulation self-testing device according to claim 2, characterized in that, The impedance unit includes: The second switch, the first end of which is electrically connected to the positive busbar; A digital potentiometer, wherein the first terminal of the digital potentiometer is electrically connected to the first terminal of the second switch, and the second terminal of the digital potentiometer is electrically connected to the negative busbar; The control circuit is electrically connected to the adjustment terminal of the digital potentiometer. The control circuit is configured to control the second switch to be turned on and adjust the resistance of the digital potentiometer to the first impedance value when the equivalent insulation resistance is greater than or equal to the preset insulation resistance value.

5. The insulation self-testing device according to claim 1, characterized in that, The DC bus includes a positive bus and a negative bus, and the impedance unit includes: A first impedance switching circuit is electrically connected between the positive busbar and the grounding node; The second impedance switching circuit is electrically connected between the negative busbar and the grounding node; The control circuit is electrically connected to the first impedance unit and the second impedance unit respectively. The control circuit is configured to apply a first control signal to the first impedance switching circuit when the equivalent insulation resistance of the positive bus is greater than or equal to a preset insulation resistance; and / or apply a second control signal to the second impedance switching circuit when the equivalent insulation resistance of the negative bus is greater than or equal to a preset insulation resistance.

6. A control method for an insulation self-testing device, characterized in that, The control method, applied to the insulation self-testing device according to any one of claims 1-5, comprises: Obtain the equivalent insulation resistance value of the DC side of the power converter; When the equivalent insulation resistance is greater than or equal to the preset insulation resistance, a first control signal is applied to the impedance unit so that the impedance unit connects an impedance element with a first impedance value between the DC bus and the grounding node, and the first impedance value is less than the equivalent insulation resistance. The power converter is controlled to perform grid connection operation based on the first impedance value and the insulation protection strategy; If the grid connection status feedback signal of the power converter is a signal that prohibits grid connection, it is determined that the insulation self-test function of the power converter is normal.

7. The control method according to claim 6, characterized in that, After determining that the insulation self-test function of the power converter is normal, the method further includes: A second control signal is applied to the impedance unit to connect an impedance element with a second impedance value between the DC bus and the grounding node, the second impedance value being greater than the equivalent insulation resistance value. The power converter is controlled to perform grid connection operation based on the second impedance value and the insulation protection strategy; If the power converter provides a signal indicating that grid connection is permitted, the power converter's grid connection function is deemed to be normal.

8. The control method according to claim 6, characterized in that, After controlling the power converter to perform grid connection operation based on the first impedance value and insulation protection strategy, the method further includes: If the power converter sends a signal indicating that grid connection is permitted, the insulation self-test function of the power converter is determined to be abnormal, and the power converter is controlled to stop operating.

9. The control method according to claim 6, characterized in that, After obtaining the equivalent insulation resistance value of the DC side of the power converter, the method further includes: If the equivalent insulation resistance is less than the preset insulation resistance, it is determined that the DC side of the power converter does not meet the insulation requirements.

10. A power converter, characterized in that, Including the insulation self-testing device according to any one of claims 1-5.

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