Inverter Insulation Resistance Measurement via Zero Sequence
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Solution Overview
Problem
Current insulation resistance measurement methods for electrical systems, particularly in high-voltage applications like electric powertrains, are not integrated and require system shutdown, limiting their effectiveness in real-time monitoring and fault location.
Innovation Solution
A method and system for determining equivalent insulation resistances in an electrical system by measuring voltages during zero sequence states of the inverter's controlled switches, using a measurement circuit with a shunt resistor, allowing for online and real-time monitoring without modifying the inverter control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If permanent insulation monitors (PICs) are used to measure insulation resistance, then insulation resistance measurement is possible, but the electrical system must be shut down for installation and measurement
Solution Approach 1:
The measurement circuit is pre-integrated into the electrical system during manufacturing, so that insulation resistance measurements can be performed immediately during operation without requiring shutdown for installation. The circuit is prepared in advance with all components in place, enabling seamless online monitoring.
Solution Approach 2:
The insulation resistance measurement process is designed to continue during system operation by utilizing zero-sequence voltage periods naturally occurring in the AC cycle. The measurement takes place continuously without interrupting the electrical system's useful action, maintaining both measurement capability and system operation simultaneously.
2Measurement precision
If system-independent permanent insulation monitors are used, then insulation resistance can be measured, but the measurement process is not integrated into the electrical system
Solution Approach 1:
The measurement circuit is merged with the existing electrical system components, sharing the same physical space and electrical connections. The measurement circuit integrates the voltage source, measurement switches, and signal processing units within the system's existing structure, eliminating separate external monitoring equipment and reducing overall device complexity.
3Productivity
If insulation resistance measurement is performed during operation using zero sequence state, then real-time monitoring is enabled, but the measurement must wait for specific switching states
Solution Approach 1:
The measurement process is synchronized with the periodic zero-sequence voltage states that occur naturally during AC operation. By triggering measurements during these periodic intervals, the system achieves real-time monitoring capability without requiring continuous interruption of normal operation, effectively utilizing the rhythmic nature of AC power cycles.
Solution Approach 2:
The control unit continuously monitors the electrical system state and automatically triggers measurements when zero-sequence conditions are detected. This feedback mechanism ensures measurements are taken at optimal moments without manual intervention or system shutdown, maintaining continuous monitoring while adapting to real-time system conditions.
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 precise, real-time determination of insulation resistances and fault location within the electrical system, enhancing safety and reducing downtime by integrating the measurement process into the system's operation.
Implementation Method 1
a method for determining at least two equivalent insulation resistances of an electrical system
Data Source
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AI summary
The invention relates to a method for determining at least two equivalent insulation resistances for an electrical system comprising an electrical source (2), an inverter (11), an electrical load (3), and a measuring circuit (5). The measurements are carried out during the operation of the electrical system, when the controlled switches of the inverter (11) are in a zero sequence. The present invention also relates to a control system for implementing such a method.