DC Bus Voltage Current Estimation Without Efficiency Tables
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Solution Overview
Problem
Existing methods for calculating DC current in motor controllers require extensive tables of MCU efficiency at various DC bus voltages, leading to a significant measurement workload.
Innovation Solution
A DC current estimation method based on DC bus voltage, which involves calibrating loss powers in a test environment, calculating AC current-related loss powers, and then applying these calculations to estimate DC current in actual operation environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If extensive tables of MCU efficiency at various DC bus voltages are used to calculate DC current, then measurement workload increases, but calculation accuracy is maintained
Solution Approach 1:
The patent extracts the voltage-dependent efficiency characteristics from the extensive multi-voltage tables and isolates them into a separate calibration process. By measuring efficiency at only one operating point and then mathematically separating the voltage-dependent components, the solution removes the need for extensive tables while maintaining calculation accuracy.
Solution Approach 2:
The patent changes the parameter approach from storing multiple efficiency values across different voltages to calculating a single efficiency value with explicit voltage dependency. By modeling efficiency as a function of voltage rather than storing discrete values for each voltage level, the system reduces measurement workload while preserving accuracy.
2Measurement precision
If extensive tables of MCU efficiency at various DC bus voltages are used to calculate DC current, then data storage requirements increase, but DC current calculation remains accurate
Solution Approach 1:
The patent extracts the essential efficiency characteristics from large data tables and stores only the critical calibration parameters. By separating the voltage-dependent efficiency components into a compact mathematical model, the solution dramatically reduces data storage requirements while maintaining calculation accuracy.
Solution Approach 2:
Instead of storing extensive measured efficiency tables, the patent creates a simplified mathematical representation (copy) of the efficiency characteristics. This copied model uses far less storage space but reproduces the essential behavior needed for accurate DC current calculation across different voltage conditions.
3Adaptability or versatility
If multiple efficiency tables corresponding to multiple voltages are called during vehicle driving, then calculation speed decreases, but comprehensive coverage of operating conditions is achieved
Solution Approach 1:
The patent creates a universal efficiency model that functions across all DC bus voltage conditions using a single set of calibration parameters. This multi-functional approach eliminates the need to switch between multiple voltage-specific tables, thereby maintaining comprehensive operating condition coverage while significantly improving calculation speed.
Solution Approach 2:
The patent implements a dynamic efficiency calculation that adapts to changing voltage conditions in real-time using mathematical relationships rather than static table lookups. This dynamic approach allows the system to respond quickly to varying operating conditions without being constrained by pre-defined voltage thresholds or multiple discrete tables.
Data Source
Figure 1
AI summary
The present invention provides a DC current estimation method and system based on DC bus voltage. The DC current estimation method includes outputting a DC bus voltage V0 of a motor controller in a test environment, and calibrating a loss power Ploss(V0)under the DC bus voltage V0; calibrating and measuring a switch loss power Psw(V0) of the power module of the motor controller; calculating an AC current-related loss power Piacloss(V0) based on the loss power Ploss(V0) and the switch loss power Psw(V0); in the actual operation environment of the motor and motor controller, obtaining an actual DC bus voltage Vdc, and calculating a current switch loss power Psw′Vdc; calculating a current loss power Ploss′Vdc based on the current switch loss power Psw′Vdc and the AC current-related loss power Piacloss(V0); and calculating a current DC power Pdc based on the current loss power Ploss′Vdc and a current AC power Pac, and then calculating a DC current idc according to the DC bus voltage Vdc. The above solution enables accurate estimation to DC current.