Insulation Detection for Electric Vehicle High Voltage Circuits
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Solution Overview
Problem
Conventional insulation detection schemes only assess the insulation state within the switch unit, failing to detect insulation faults outside the switch unit, which can lead to dangerous insulation failures in high-voltage circuits of electric vehicle battery packs.
Innovation Solution
An insulation detection method utilizing a circuit with a battery pack, switch unit, load, controller, sampling points, and reference resistance units to calculate and compare equivalent resistances, determining insulation resistance on both sides of the switch unit and load, and transmitting alerts for abnormal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional insulation detection schemes are used, then the detection process is simple, but only the insulation state within the switch unit can be assessed, failing to detect insulation faults outside the switch unit
Solution Approach 1:
The detection method segments the high-voltage circuit into two distinct zones: the battery pack side (first high-voltage circuit) and the load side (second high-voltage circuit). By calculating equivalent resistances for each zone separately and comparing them against threshold values, the system achieves comprehensive insulation monitoring across the entire circuit while maintaining a relatively simple detection implementation approach.
Solution Approach 2:
The switch unit serves as an intermediary element that enables the detection method to assess insulation on both sides of the circuit. By utilizing the switch unit's connection between the battery pack and load, the system can perform sequential measurements that reveal insulation states in both zones without requiring separate detection systems for each side.
2Reliability
If insulation detection is performed only within the switch unit, then the detection method is simple, but insulation faults outside the switch unit cannot be detected, leading to dangerous failures
Solution Approach 1:
The detection method performs preliminary assessment of insulation resistance in both the battery pack side and load side before actual operation or fault occurrence. By calculating equivalent resistances and comparing them against predetermined threshold values, the system proactively identifies potential insulation degradation or faults, enabling preventive maintenance before dangerous failures occur.
3Measurement precision
If equivalent resistance calculation method is used, then insulation resistance can be determined, but the detection process requires multiple calculation steps
Solution Approach 1:
The detection system performs periodic insulation resistance measurements by sequentially closing different switches in the switch unit. Each switching action triggers a measurement cycle where equivalent resistances are calculated and compared against thresholds. This periodic detection approach ensures continuous monitoring of insulation status in both circuit zones while using efficient calculation methods to minimize measurement time.
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
Effectively detects insulation states on both sides of the battery pack and load, preventing insulation faults by determining and addressing insulation failures in high-voltage circuits, enhancing safety in electric vehicle power systems.
Implementation Method 1
a first equivalent resistance and a second equivalent resistance are calculated; the first equivalent resistance is an equivalent resistance of the positive electrode of the battery pack relative to a reference potential terminal
Implementation Method 2
when the first insulation resistance is normal, the switch unit is closed, and a second insulation resistance is calculated according to the first equivalent resistance, the second equivalent resistance, a voltage of the first sampling point and a voltage of the second sampling point when the switch unit is closed
Data Source
AI summary
An insulation detection method includes: a first and second equivalent resistances are calculated; the less one of the first and second equivalent resistances is taken as a first insulation resistance, which is an insulation resistance of the high voltage circuit on the side where the battery pack locates relative to the reference potential terminal; when the first insulation resistance is normal, the switch unit is closed, and a second insulation resistance is calculated according to the first and second equivalent resistances, voltages of a first and second sampling point when the switch unit is closed; the second insulation resistance is an insulation resistance of the high voltage circuit on the side where the load locates relative to the reference potential terminal; the insulation state of the high voltage circuit on the side where the load locates is determined according to the second insulation resistance.