PV Ground Insulation Impedance Detection Using Harmonic Injection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photovoltaic energy storage systems face challenges in accurately detecting ground insulation impedance due to the impact of parasitic capacitance, leading to low detection accuracy and potential safety risks.
Innovation Solution
A photovoltaic energy storage system with a detection circuit that uses harmonic injection to determine ground insulation impedance, excluding parasitic capacitance effects, by outputting harmonic signals of different frequencies and using a control circuit to calculate impedance based on collected voltages and phases, thereby improving detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional insulation resistance detection circuit is used in photovoltaic energy storage system, then the detection can be performed, but the detection accuracy is low due to parasitic capacitance impact
Solution Approach 1:
The patent extracts and eliminates the harmful parasitic capacitance effect from the detection system by using harmonic injection method. The detection circuit injects harmonic signals and processes the response to obtain insulation impedance values that are not affected by parasitic capacitance, effectively removing the interference factor from the measurement system.
Solution Approach 2:
The patent changes the detection parameter from direct insulation resistance measurement to harmonic impedance measurement. By injecting harmonic signals and measuring the system's frequency response, the detection method transforms the measurement parameter to one that is insensitive to parasitic capacitance, thereby improving measurement accuracy.
2Power
If conversion circuits with high voltage class are used in photovoltaic energy storage system, then power conversion capability is improved, but insulation safety requirements become more stringent
Solution Approach 1:
The patent implements preliminary detection of ground insulation impedance before fault occurrence. The detection circuit continuously monitors insulation status using harmonic injection, enabling early warning and preventive maintenance, thus ensuring reliability of high-power conversion circuits before insulation degradation leads to safety issues.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the accuracy of ground insulation impedance detection, ensuring the safety and reliability of the photovoltaic energy storage system by accurately determining the insulation status without including parasitic capacitance in the calculation.
Implementation Method 1
The control circuit is configured to control the alternating current signal source to output harmonic signals of a first frequency and a second frequency
Implementation Method 2
determine, based on the harmonic signals of the first frequency and the second frequency, the first voltage, and the second voltage, a ground insulation impedance
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
This application provides a photovoltaic energy storage system and a method for detecting a ground insulation impedance, to improve accuracy of detecting a ground insulation impedance after one or more conversion circuits are connected in parallel. The photovoltaic energy storage system includes one or more conversion circuits and a detection circuit. The detection circuit includes an alternating current signal source and a sampling resistor that are connected in series, a first sampling circuit, and a control circuit. The control circuit is configured to control the alternating current signal source to output harmonic signals of a first frequency and a second frequency. The first sampling circuit is configured to: when the alternating current signal source outputs the harmonic signal of the first frequency, collect a voltage at both terminals of the sampling resistor to obtain a first voltage; when the alternating current signal source outputs the harmonic signal of the second frequency, collect a voltage at both terminals of the sampling resistor to obtain a second voltage; and send the first voltage and the second voltage to the control circuit. The control circuit is further configured to determine, based on the harmonic signals of the first frequency and the second frequency, the first voltage, and the second voltage, a ground insulation impedance obtained after the one or more conversion circuits are connected in parallel.