An insulation impedance detection device for a photovoltaic inverter

Abstract

The application provides an insulation impedance detection device for a photovoltaic inverter, which comprises a main circuit voltage Ubus of a photovoltaic array DC / DC rectification, a first measuring resistor R1, a second measuring resistor R2, a third measuring resistor R3, a fourth measuring resistor R4 and a fifth measuring resistor R5 which are connected in series in sequence, a negative electrode of the main circuit voltage Ubus is connected with a GND ground, and the second measuring resistor R2 and the third measuring resistor R3 are connected with a PE ground; a branch comprising a sixth measuring resistor R6, a seventh measuring resistor R7 and an eighth measuring resistor R8 is connected in parallel between the GND ground and the PE ground; an equivalent impedance Rp is connected in parallel between a positive electrode of the main circuit voltage Ubus and the PE ground, and an equivalent impedance Rn is connected in parallel between the GND ground and the PE ground; and a short-circuit switch K1 is arranged at two ends of the second measuring resistor R2. The application can realize insulation impedance detection of the photovoltaic inverter by alternately measuring voltage on the voltage terminal twice, and has the beneficial effects of using fewer components, simple insulation impedance detection and accurate results.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic inverter testing equipment, and more specifically to an insulation impedance testing device for photovoltaic inverters. Background Technology

[0002] Against the backdrop of global energy shortages and environmental degradation, the utilization of new clean energy sources is of paramount importance, with solar energy being widely developed and applied due to its renewable and abundant nature. With the increasing prevalence of grid-connected photovoltaic (PV) power generation, the safety of PV grid-connected power generation systems is receiving growing attention.

[0003] like Figure 1 As shown, the photovoltaic array is rectified by a DC / DC rectifier circuit and then connected to the grid via a DC / AC photovoltaic inverter system. However, since the photovoltaic array is placed outdoors, it is affected by factors such as dust, rain, snow, and fog, which may cause changes in the insulation resistance of the positive and negative terminals to ground. This not only affects the safe operation of the photovoltaic grid-connected inverter but also threatens personal safety. Therefore, it is necessary to test the DC-side insulation resistance of each inverter unit (i.e., the insulation resistance of the positive and negative terminals of the photovoltaic array connected to the DC side of the inverter unit to ground) using an insulation resistance detection device before and after grid connection, in order to promptly detect and eliminate potential safety hazards. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an insulation impedance detection device for photovoltaic inverters. This invention alternately closes the DC-side switch of the photovoltaic inverter, alternately feeding the DC-side voltage into the insulation impedance detection device. Insulation impedance detection of the photovoltaic inverter can be achieved by simply measuring the voltage twice alternately at the voltage terminals. Furthermore, it has the advantages of using fewer components, simple insulation impedance detection, and accurate results.

[0005] To achieve the aforementioned technical objective, the technical solution of the present invention is: an insulation impedance detection device for a photovoltaic inverter, comprising a circuit in which the main circuit voltage Ubus after DC / DC rectification of the photovoltaic array, a first measuring resistor R1, a second measuring resistor R2, a third measuring resistor R3, a fourth measuring resistor R4, and a fifth measuring resistor R5 are connected in series, the negative terminal of the main circuit voltage Ubus is connected to GND, and the second measuring resistor R2 and the third measuring resistor R3 are connected to PE ground;

[0006] A branch consisting of the sixth measuring resistor R6, the seventh measuring resistor R7, and the eighth measuring resistor R8 is connected in parallel between the GND ground and the PE ground.

[0007] An equivalent impedance Rp is connected in parallel between the positive terminal of the main circuit voltage Ubus and the PE ground, and an equivalent impedance Rn is connected in parallel between the GND ground and the PE ground.

[0008] A short-circuit switch K1 is set across the second measuring resistor R2.

[0009] Furthermore, a voltage measurement terminal Ui is provided between the fourth measuring resistor R4 and the fifth measuring resistor R5.

[0010] Furthermore, an operational amplifier, resistors R9 and R10 are configured. The non-inverting input of the operational amplifier is connected to the voltage measurement terminal Ui through resistor R9, and the inverting input is connected to the output terminal Uo through R10.

[0011] Furthermore, a single-chip microcomputer is electrically connected to the output terminal Uo.

[0012] Preferably, a second switch K2 is provided, and the second switch K2 is located in the branch.

[0013] The beneficial effects of this invention are as follows:

[0014] This invention involves alternating closing of the DC-side switch of a photovoltaic inverter to alternately send the DC-side voltage to the insulation impedance detection device. The insulation impedance detection of the photovoltaic inverter can be achieved by simply measuring the voltage twice at the voltage terminals. It has the advantages of using fewer components, simple insulation impedance detection, and accurate results. Attached Figure Description

[0015] Figure 1 This is a schematic diagram illustrating the insulation impedance detection principle of a photovoltaic inverter.

[0016] Figure 2 This is a circuit diagram of the insulation resistance detection device of the present invention;

[0017] Figure 3 This is a schematic diagram of another implementation of the insulation impedance detection device of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below.

[0019] An insulation impedance detection device for photovoltaic inverters, such as Figure 2 As shown, the circuit includes the main circuit voltage Ubus after DC / DC rectification of the photovoltaic array, the first measuring resistor R1, the second measuring resistor R2, the third measuring resistor R3, the fourth measuring resistor R4, and the fifth measuring resistor R5 connected in series. The negative terminal of the main circuit voltage Ubus is connected to GND, and the second measuring resistor R2 and the third measuring resistor R3 are connected to PE ground.

[0020] A branch consisting of the sixth measuring resistor R6, the seventh measuring resistor R7, and the eighth measuring resistor R8 is connected in parallel between the GND ground and the PE ground.

[0021] An equivalent impedance Rp (i.e., the equivalent impedance of PE to the positive terminal of the main circuit voltage Ubus) is connected in parallel between the positive terminal of the main circuit voltage Ubus and the PE ground, and an equivalent impedance Rn (the equivalent impedance of PE to GND) is connected in parallel between the GND ground and the PE ground.

[0022] A short-circuit switch K1 is set across the second measuring resistor R2.

[0023] Furthermore, a voltage measurement terminal Ui is set between the fourth measuring resistor R4 and the fifth measuring resistor R5. During detection, the short-circuit switch K1 is opened to read the Ui sample value once as Ui1, and the short-circuit switch K1 is closed to read the Ui sample value again as Ui2. The equivalent resistance Rx of the system to ground, which is the sum of Rp and Rn, can be calculated using the following formula.

[0024]

[0025] in,

[0026] Furthermore, an operational amplifier, resistors R9 and R10 are configured. The non-inverting input of the operational amplifier is connected to the voltage measurement terminal Ui through resistor R9, and the inverting input is connected to the output terminal Uo through R10.

[0027] Furthermore, by electrically connecting a single-chip microcomputer to the output terminal Uo, electronic reading can be achieved.

[0028] Preferably, by electrically connecting a wireless remote voltmeter to the voltage measurement terminal Ui, remote monitoring of insulation impedance can be achieved.

[0029] As a preferred embodiment of the present invention, such as Figure 3 As shown, a second switch K2 is installed at one end of the branch circuit, with the PE ground located between the second switch K2 and the sixth measuring resistor R6. The second switch K2 isolates the PE ground measuring terminal from the main circuit during non-operating times, reducing interference.

[0030] For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this invention, and these all fall within the protection scope of this invention.

Claims

1. An insulation impedance detection device for photovoltaic inverters, characterized in that... The circuit consists of the main circuit voltage Ubus after DC / DC rectification of the photovoltaic array, the first measuring resistor R1, the second measuring resistor R2, the third measuring resistor R3, the fourth measuring resistor R4, and the fifth measuring resistor R5 connected in series. The negative terminal of the main circuit voltage Ubus is connected to GND, and the second measuring resistor R2 and the third measuring resistor R3 are connected to PE ground. A branch consisting of the sixth measuring resistor R6, the seventh measuring resistor R7, and the eighth measuring resistor R8 connected in series is connected between the GND ground and the PE ground. An equivalent impedance Rp is connected in parallel between the positive terminal of the main circuit voltage Ubus and the PE ground, and an equivalent impedance Rn is connected in parallel between the GND ground and the PE ground. A short-circuit switch K1 is installed across the second measuring resistor R2; A voltage measurement terminal Ui is provided between the fourth measuring resistor R4 and the fifth measuring resistor R5; Set up an operational amplifier, resistors R9 and R10. The non-inverting input of the operational amplifier is connected to the voltage measurement terminal Ui through resistor R9, and the inverting input is connected to the output terminal Uo through resistor R10. The microcontroller is electrically connected to the output terminal Uo; A second switch K2 is set at one end of the branch. The second switch K2 is located between the second measuring resistor R2 and the sixth measuring resistor R6. The PE ground is located between the second switch K2 and the sixth measuring resistor R6.

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