Inverter Insulation Impedance Detection During Grid Connection
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Solution Overview
Problem
Conventional methods for detecting insulation impedance of an inverter cannot accurately measure impedance to ground when the inverter is connected to a power grid, limiting the detection to only pre-connection scenarios.
Innovation Solution
A method involving a test circuit with a test resistor and power supply connected in series, where the inverter's direct-current or alternating-current side is grounded, and different test signals are outputted by the power supply to calculate insulation impedance during grid-connected operation, using either a constant voltage or current source to disturb the power grid voltage and record corresponding voltages or currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional impedance detection method is used, then impedance to ground before inverter connection can be detected, but impedance to ground when inverter is connected to power grid cannot be detected
Solution Approach 1:
The patent applies dynamics by making the test circuit configurable to operate in different modes: before grid connection and during grid connection. The power supply can output different test signals (DC or AC) depending on the operational state, enabling the detection system to adapt dynamically to different detection scenarios without requiring separate fixed circuits.
Solution Approach 2:
The test circuit is designed with multi-functionality to perform both pre-connection insulation impedance detection and during-connection insulation impedance detection using the same hardware components. The power supply can function as either a DC voltage source or an AC voltage source, and the test circuit can be configured for different grounding scenarios (DC side grounding or AC side grounding), making it a universal detection solution.
2Adaptability or versatility
If power supply outputs different test signals to disturb power grid voltage, then insulation impedance during grid-connected operation can be detected, but detection complexity increases
Solution Approach 1:
The same test circuit hardware is used for both pre-connection and during-connection detection, with the power supply capable of outputting different types of test signals (DC or AC) based on the detection scenario. This multi-functional design avoids the need for separate dedicated circuits for each detection mode, thereby managing complexity while maintaining versatility.
Solution Approach 2:
The detection system changes parameters (test signal type, grounding configuration) rather than changing the fundamental circuit structure. By adjusting the power supply output characteristics and grounding connections, the system adapts to different detection scenarios without requiring complex additional components or circuit redesigns.
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
Enables accurate detection of insulation impedance during grid-connected operation, improving detection speed and reducing mechanical stress on components by minimizing continuous disconnections, thus enhancing system reliability and safety.
Implementation Method 1
impedance of the power grid to ground is calculated based on a impedance voltage-division principle
Data Source
AI summary
An inverter and a method for detecting insulation impedance of the inverter are provided. During grid-connected operation of the inverter, the method includes: controlling a power supply to output two different test signals, and recording voltages of a power grid to ground corresponding to the two test signals; and calculating the insulation impedance to ground of the inverter during the grid-connected operation of the inverter according to the two test signals and the voltages of the power grid to ground corresponding to the two test signals. According to the present disclosure, the power supply outputs different test signals to disturb the voltage of the power grid to ground, so as to detect insulation impedance of the inverter during grid-connected operation of the inverter.