Insulation resistance detection method and system for inverter system based on rectifier-circuit auxiliary power supply, and storage medium
By monitoring the inverter system bus voltage and rectifier circuit auxiliary power supply, the problem of photovoltaic inverters being unable to detect insulation impedance at night or on cloudy days has been solved, enabling accurate calculation of insulation impedance at low cost.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-09-05
- Publication Date
- 2026-04-02
AI Technical Summary
In photovoltaic inverters, insulation resistance cannot be properly detected at night or on cloudy days because the main circuit has a fixed potential relationship with the ground, resulting in false alarms in existing technologies.
By monitoring the inverter system bus voltage and combining it with the auxiliary power supply of the rectifier circuit, the insulation impedance of the main circuit of the inverter system to ground is calculated. The insulation impedance is calculated by sampling the resistance value in the rectifier circuit and the bus voltage.
With the main circuit having a potential relationship with the ground, normal detection of insulation impedance was achieved, reducing hardware costs and improving the product's economic efficiency.
Smart Images
Figure CN2025119302_02042026_PF_FP_ABST
Abstract
Description
Insulation impedance detection method, system and storage medium of inverter system based on auxiliary power supply of rectifier circuit TECHNICAL FIELD
[0001] The application belongs to the field of insulation impedance detection of inverter system, and particularly relates to an insulation impedance detection method, system and computer readable storage medium of inverter system based on auxiliary power supply of rectifier circuit. BACKGROUND
[0002] According to the requirements of national or industry standards (such as IEC62109), in order to ensure the safety of the human body, the insulation resistance of the system needs to be detected before the non-isolated grid-connected inverter is connected to the grid, and if the insulation impedance is less than the standard requirement, the photovoltaic inverter is not allowed to be connected to the grid.
[0003] The existing photovoltaic inverter requires that the ground and the main circuit are in a high resistance or insulated state when the insulation impedance is monitored, and if there is a fixed potential relationship between the ground voltage and the main circuit, the voltage will be clamped before and after the relay of the insulation impedance detection circuit is actuated, resulting in calculation error and false alarm. In the photovoltaic energy storage inverter, there may be only grid access at night or on cloudy days, and when the auxiliary power supply circuit is a rectifier circuit, there will be a fixed potential relationship between the main circuit of the inverter and the ground, and at this time, the normal insulation impedance cannot be monitored.
[0004] The above information disclosed in the background section is only used to strengthen the understanding of the background of the present application, and therefore it can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY
[0005] The application provides an insulation impedance detection method of inverter system based on auxiliary power supply of rectifier circuit, which is used to solve the problem that the insulation impedance cannot be normally detected when there is a potential relationship between the ground and the main circuit, and the impedance of the main circuit of the inverter system to the ground is calculated by monitoring the bus voltage of the inverter system. The application also provides an insulation impedance detection system of inverter system based on auxiliary power supply of rectifier circuit and a computer readable storage medium.
[0006] To achieve the above purpose, the application adopts the following technical scheme:
[0007] An insulation impedance detection method of inverter system based on auxiliary power supply of rectifier circuit, comprising the following steps:
[0008] Obtaining the resistance value of a first resistor connected in series between the rectifier circuit and the positive DC bus of the inverter system, and obtaining the resistance value of a second resistor connected in series between the rectifier circuit and the negative DC bus of the inverter system;
[0009] Obtaining the loss power of the inverter system;
[0010] sampling a bus voltage of the inverter system;
[0011] sampling a grid phase voltage;
[0012] calculating an insulation impedance of the inverter system to ground according to the resistance value of the first resistor, the resistance value of the second resistor, a loss power of the inverter system, the bus voltage and the grid phase voltage.
[0013] In a preferred embodiment, the system equivalent resistance is obtained according to the bus voltage and the loss power of the inverter system.
[0014] In a more preferred embodiment, the equivalent resistance R of the system loss is obtained according to the following formula: load
[0015] wherein U represents the bus voltage, P represents the loss power of the inverter system, and R represents the loss equivalent resistance of the inverter system. bus load load
[0016] In a preferred embodiment, the insulation impedance R is calculated according to the following formula: iso
[0017] wherein P represents the loss power of the inverter system, U represents the bus voltage of the inverter system, R1 represents the resistance value of the first resistor, R2 represents the resistance value of the second resistor, and U represents the grid phase voltage. load bus ac
[0018] In a preferred embodiment, the rectifier circuit comprises a plurality of rectifier diodes, the first resistor is connected in series between a positive output end of the rectifier circuit and a positive DC bus of a main circuit of the inverter system, and the second resistor is connected in series between a negative output end of the rectifier circuit and a negative DC bus of the main circuit, so as to convert AC power from the grid into DC power supplied to the main circuit through the rectifier circuit.
[0019] In a preferred embodiment, the grid phase voltage is a phase voltage of a three-phase grid.
[0020] In a preferred embodiment, the inverter system comprises a photovoltaic inverter, an energy storage inverter or a photovoltaic energy storage inverter.
[0021] Another technical solution adopted by the present application is as follows:
[0022] An insulation impedance detection system of an inverter system based on auxiliary power supply of a rectifier circuit, comprising a memory and a processor, the memory stores a computer program, and the processor implements the insulation impedance detection method when executing the computer program.
[0023] Another technical solution adopted by the present application is as follows:
[0024] A computer readable storage medium stores a computer program, and the program implements the insulation impedance detection method when executed by a processor.
[0025] The above solution adopted by the present application has the following advantages:
[0026] The insulation impedance detection method of the inverter system based on auxiliary power supply of a rectifier circuit of the present application, in the case of only grid access at night or on cloudy days, takes the rectifier circuit as the auxiliary power supply circuit of the inverter system, and provides low-voltage power for the control and driving components of the power main loop of the inverter system. In this case, the insulation impedance detection method of the present application calculates the insulation impedance of the main loop of the inverter system to the ground by detecting the bus voltage of the inverter system. In the case of potential relationship between the ground voltage and the main circuit, the normal detection of the insulation impedance can be realized. In addition, through the analysis of the circuit, the insulation impedance is calculated based on the system hardware sampling circuit, without the need to increase additional hardware circuit to monitor the insulation impedance, which can reduce the hardware cost of the system and improve the economy of the product. BRIEF DESCRIPTION OF DRAWINGS
[0027] In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.
[0028] Fig. 1 is a circuit diagram of an inverter system applying the insulation impedance detection method according to an embodiment of the present application. DETAILED DESCRIPTION
[0029] The preferred embodiments of the present application will be described in detail below with reference to the drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present application, but does not constitute a limitation of the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
[0030] Referring to FIG. 1, in an inverter system, when using uncontrolled rectification current 2 to supply power to main circuit 3, due to the TN-S connection mode of power grid 1, the neutral point of the three-phase winding of the distribution transformer is grounded, and there is a potential relationship between main circuit 3 and the ground, and the midpoint potential of the DC voltage after three-phase voltage passing through uncontrolled rectification is equal to the potential of the ground. As shown in FIG. 1, the output end of rectification circuit 2 is connected in series with resistors R1 and R2 to prevent damage to rectification diodes D1 to D6 caused by short circuit of the BUS bus, and the latter is connected to the DC bus BUS+ and BUS- of the inverter system, and the power supply of the inverter system is provided by the BUS voltage, and the equivalent resistance of the system loss is R load . iso is the insulation impedance of the inverter system to the ground.
[0031] The inverter system can include a photovoltaic inverter, an energy storage inverter, or a photovoltaic energy storage inverter. The main circuit described above includes an inverter circuit, a control circuit, and the like.
[0032] When the system impedance to the ground is infinite, the bus voltage is obtained by voltage division of R load , R1 and R2, and the specific relationship is shown in the following formula (1).
[0033] Formula (1):
[0034] In the inverter system, there may be a situation that the photovoltaic cable is damaged, at this time, the impedance of the inverter system to the ground is relatively low, even at night, although the photovoltaic panel has no voltage, but the cable of the string is connected with the main circuit of the inverter, which will cause the system impedance to the ground to decrease. At this time, R iso will have an impact on the circuit. The ground voltage at both ends of R2 is shown in the following formula (2).
[0035] Formula (2):
[0036] In the inverter system, the BUS voltage is measurable, which can be obtained by sampling. According to Kirchhoff's law, the following formulas (3) to (5) can be obtained.
[0037] Formula (3):
[0038] Formula (4):
[0039] Formula (5):
[0040] In the above formula, U bus is the BUS voltage sampling value of the inverter system, R1 and R2 are fixed resistance values, U ac is the phase voltage of the power grid, which can be obtained by sampling the inverter system. The loss equivalent resistance R load is calculated by the following formula:
[0041] The insulation impedance of the inverter system is calculated according to the relationship (5), and it can be seen from the formula that the calculation of the ISO resistance requires sampling the BUS voltage, and the resistance values of the resistors R1 and R2 are stable. For two-phase (U, V phase) input, this method is still applicable.
[0042] Therefore, the insulation impedance detection method of the inverter system based on the auxiliary power supply of the rectifier circuit in the embodiment comprises the following steps:
[0043] The resistance value of the first resistor R1 connected between the rectifier circuit and the positive DC bus of the inverter system is obtained, and the resistance value of the second resistor R2 connected between the rectifier circuit and the negative DC bus of the inverter system is obtained;
[0044] The loss power P of the inverter system is obtained load .
[0045] The bus voltage U bus of the inverter system is sampled;
[0046] The grid phase voltage U ac is sampled;
[0047] The insulation impedance of the inverter system to the ground is calculated according to the resistance value of the first resistor R1, the resistance value of the second resistor R2, the loss power P load of the inverter system, the bus voltage U bus and the grid phase voltage U ac . Specifically, it is calculated according to the following formula:
[0048] Example:
[0049] Suppose the grid phase voltage U ac is 230Vac, the standby loss P load of the inverter is 10W, and R1=R2=600Ω.
[0050] When the entire inverter system has infinite impedance to the ground, according to the above relationship (1), the bus bus satisfies the following relationship:
[0051] U bus =541.2
[0052] When the inverter system is short-circuited to the ground, the midpoint V-PE voltage output by the rectifier circuit is equal to the negative bus voltage:
[0053] U PE-PV- =0
[0054] Therefore, according to the above relationship (1), the bus voltage satisfies the following relationship:
[0055] U bus = 258.5V
[0056] From the above, when the photovoltaic system impedance to ground is infinite and short circuit, the corresponding BUS voltage is between the normal bus voltage and 1 / 2 of it.
[0057] When the monitored BUS voltage is 530V,
[0058] Therefore:
[0059] When the monitored BUS voltage is 350V,
[0060] Therefore:
[0061] From the above, the lower the inverter system impedance to ground, the closer the BUS voltage to 1 / 2 of the grid rectified voltage, verifying the effectiveness of the insulation impedance detection method of the embodiment.
[0062] The embodiment also provides an insulation impedance detection system of an inverter system based on a rectifier auxiliary power supply, comprising a memory and a processor, the memory stores a computer program, and the processor realizes the insulation impedance detection method when executing the computer program.
[0063] The embodiment also provides a computer readable storage medium, which stores a computer program, and the program realizes the insulation impedance detection method when executed by a processor. The computer readable storage medium includes but is not limited to a read-only memory, a magnetic disk or an optical disk.
[0064] The embodiment aims at the case that only the grid is connected at night or on a cloudy day, and uses the rectifier circuit as an auxiliary power supply circuit of the inverter system to provide low-voltage power for the control and driving components of the power main loop of the inverter system. In this case, the insulation impedance detection method of the embodiment calculates the insulation impedance of the main loop of the inverter system to ground by detecting the bus voltage of the inverter system, and can realize normal detection of the insulation impedance in the case that the ground voltage and the main circuit exist a potential relationship. In addition, the insulation impedance is calculated based on the system hardware sampling circuit through the analysis of the circuit, and no additional hardware circuit is needed to monitor the insulation impedance, which can reduce the hardware cost of the system and improve the economy of the product.
[0065] As shown in the specification and claims, the terms "comprising" and "including" are used only to indicate the inclusion of one or more recited steps or elements and do not exclude other steps or elements. The term "and / or" as used in the specification and claims includes any and all combinations of one or more of the associated listed items.
[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In the event of a contradiction between the definitions as used in this document and those set forth in other documents, the definitions as used in this document shall control.
[0067] As shown in the specification and claims, the terms "comprising" and "including" are used only to indicate the inclusion of one or more recited steps or elements and do not exclude other steps or elements. The term "and / or" as used in the specification and claims includes any and all combinations of one or more of the associated listed items.
[0068] It should be understood that each of the steps of the present application can be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented by any one or a combination of the following technologies known in the art: discrete logic circuit with logic gate circuit for implementing logic functions on data signals, application specific integrated circuit with suitable combination logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA), etc.
[0069] Those of ordinary skill in the art can understand that all or part of the steps carried out by the above-described embodiments can be completed by programs instructing relevant hardware, and the programs can be stored in a computer readable storage medium, and when executed, include one or a combination of steps of the method embodiments.
[0070] In addition, each functional unit in the embodiments can be integrated into one processing module, or each unit can exist physically separately, or two or more units can be integrated into one module. The above integrated module can be realized in the form of hardware or in the form of a software functional module. When the integrated module is realized in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer readable storage medium.
[0071] The above examples are only for illustrating the technical concept and characteristics of the present application, and are a preferred embodiment, and the purpose is that the person skilled in the art can understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent transformation or modification according to the principle of the present application should be covered in the protection scope of the present application.
Claims
1. A method for detecting insulation impedance of an inverter system based on auxiliary power supply of a rectifier circuit, characterized by, The method comprises the following steps: obtaining a resistance value of a first resistor connected between a positive DC bus of a rectifier circuit and an inverter system, and obtaining a resistance value of a second resistor connected between a negative DC bus of the rectifier circuit and the inverter system; obtaining a loss power of the inverter system; sampling a bus voltage of the inverter system; sampling a grid phase voltage; calculating an insulation impedance of the inverter system to ground according to the resistance value of the first resistor, the resistance value of the second resistor, the loss power of the inverter system, the bus voltage and the grid phase voltage.
2. The insulation impedance detection method according to claim 1, characterized by, obtaining a loss equivalent resistor according to the bus voltage and the loss power of the inverter system.
3. The insulation impedance detection method according to claim 2, characterized by, The loss equivalent resistance R is obtained according to the following formula load : wherein U bus represents the bus voltage, P load represents the loss power of the inverter system, R load represents the loss equivalent resistance of the inverter system.
4. The insulation impedance detection method according to any one of claims 1 to 3, characterized in that, The insulation resistance R is calculated according to the following formula iso : where P load represents the inverter system loss power, U bus represents the bus voltage of the inverter system, R1 represents the resistance value of the first resistor, R2 represents the resistance value of the second resistor, U ac represents the grid phase voltage.
5. The insulation impedance detection method according to claim 1, characterized by, The rectifier circuit comprises a plurality of rectifier diodes, the first resistor is connected between a positive output end of the rectifier circuit and a positive DC bus of a main circuit of the inverter system, and the second resistor is connected between a negative output end of the rectifier circuit and a negative DC bus of the main circuit, so as to convert AC power from a grid into DC power supplied to the main circuit through the rectifier circuit.
6. The insulation impedance detection method according to claim 1, characterized by, The grid phase voltage is a phase voltage of a three-phase grid.
7. The insulation impedance detection method according to claim 1, characterized by, The inverter system comprises a photovoltaic inverter, an energy storage inverter or a photovoltaic energy storage inverter.
8. An insulation impedance detection system for an inverter system based on a rectifier auxiliary power supply, comprising a memory and a processor, the memory storing a computer program, characterized in that, The processor executes the computer program to realize the insulation impedance detection method according to any one of claims 1 to 7.
9. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the program is executed by the processor to realize the insulation impedance detection method according to any one of claims 1 to 7.