Insulation Resistance Measurement Timing for Fast EV Startup
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Solution Overview
Problem
Existing methods for insulation resistance measurement in ungrounded power supply systems, particularly in electric vehicles, struggle to meet the quick-start requirements of providing a valid insulation resistance value within 5 seconds while maintaining a measuring tolerance of 0% to -50% in the range of 100 Ohm/V to 500 Ohm/V, due to residual voltages from leakage capacitances and Y-capacitors.
Innovation Solution
A method that calculates a target charging state or rate for network capacities, determining a target point in time and wait times using digital signal processing to predict the insulation state, allowing for a safe-to-start signal if the wait time is less than the specified quick-start time, thereby avoiding the need for continuous sampling of charging states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous sampling of charging states is performed to ensure measurement accuracy, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The patent applies preliminary action by calculating the target charging state in advance using the measured voltage curve and time constant. Instead of waiting for the charging process to complete naturally, the system predicts when the target state will be reached and adjusts the measurement timing accordingly. This allows the measurement to be performed at the optimal moment without requiring continuous sampling throughout the entire charging process, thus maintaining precision while reducing measurement time to meet the 5-second quick-start requirement.
2Loss of time
If the measurement is performed before the charging process is complete, then measurement time is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the measured voltage curve and using it to calculate the time constant and predict the target charging state. The system adjusts the measurement timing based on this feedback loop, performing the measurement at the precise moment when the target charging state is reached. This feedback mechanism ensures that the measurement is performed at the optimal time, maintaining high precision while enabling quick-start operation within 5 seconds.
3Measurement precision
If the charging process is allowed to complete fully before measurement, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent applies preliminary action by predicting the target charging state in advance using the measured voltage curve and calculated time constant. Instead of waiting for the charging process to complete naturally, the system determines when the target state will be reached and performs the measurement at that predicted moment. This eliminates the need to wait for full charging completion, thereby maintaining measurement precision while significantly improving system startup speed to meet the 5-second quick-start requirement.
4Productivity
If the measurement is accelerated to meet quick-start requirements, then productivity is improved, but measurement precision deteriorates
Solution Approach 1:
The patent implements feedback by continuously monitoring the measured voltage curve and using it to calculate the time constant and predict the target charging state. The system adjusts the measurement timing based on this feedback, performing the measurement at the precise moment when the target state is reached. This feedback mechanism ensures that even with accelerated timing to meet the 5-second quick-start requirement, the measurement precision is maintained by capturing the voltage at the optimal point in the charging process.
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 and rapid determination of insulation resistance, meeting quick-start requirements by predicting the charging state before the charging process is complete, reducing measurement time and improving precision.
Implementation Method 1
the leakage capacitances of the IT network (on-board network of the electric vehicle) and the Y-capacitors of a user often in conjunction with insulation monitoring according to the pulse measuring method still have a residual voltage owing to the charge reversal with the measuring impulse of a preceding measuring cycle
Implementation Method 2
a measuring voltage compiled of temporally consecutive square measuring pulses is applied between at least one active conductor of the ungrounded power supply system and ground by means of a measuring pulse generator via a coupling branch having a coupling resistance and a continuous-time curve of a voltage measured via the measuring resistance is captured
Data Source
AI summary
Methods are provided for accelerating the insulation resistance measuring for determining an insulation resistance according to a pulse measuring method in an ungrounded power supply system. After indicating a target charging state of the network capacities available, a target point in time is calculated at which the network capacities have reached the target charging state. A first wait time is calculated from the current point in time as the difference between the target charging state and the current point. Alternatively, a target charging rate reflects a sufficiently stationary charging state of the capacitors, valid for measuring the insulation resistance. The target charging rate corresponds to the derivative of the first order of the target charging voltage and thus linked to the target point in time. Using the derivatives of the first order, a time difference is calculated as a second wait time.