EV Motor Neutral Charging Control Using Dual Voltage Sensing
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Solution Overview
Problem
Existing battery charging systems inaccurately measure supply voltage using a single voltage sensor, leading to a lower current command value and extended charging times due to the need for a larger margin in voltage measurement, which results in power exceeding the battery's capacity.
Innovation Solution
Utilizing two voltage sensors to measure supply voltage accurately, calculating a current command value based on the smaller of the two values with added margins, ensuring the power supplied does not exceed the battery's permissible power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single voltage sensor is used to measure supply voltage, then the measurement system is simple, but the measurement accuracy is insufficient requiring a larger margin which reduces the current command value and extends charging time
Solution Approach 1:
The voltage measurement function is segmented into two separate measurement paths: one through the booster circuit voltage sensor and another through the battery voltage sensor. Each sensor measures the same supply voltage from different points in the circuit, and the controller selects the appropriate measurement value based on which path has lower current flow, thereby achieving higher measurement accuracy without extending charging time.
2Reliability
If a larger margin is added to the voltage measurement value, then the battery is protected from overcharging, but the calculated supply power becomes smaller than actual supply power resulting in a lower current command value
Solution Approach 1:
The controller continuously monitors both voltage sensor readings and their corresponding current values, using feedback to dynamically select the most accurate voltage measurement. By comparing the product of voltage and current from both measurement paths, the controller identifies which path has lower current flow and selects that voltage measurement, thereby maintaining battery protection while maximizing charging speed through accurate real-time feedback.
3Reliability
If the current command value is reduced to ensure power does not exceed battery capacity, then battery safety is maintained, but charging time is unnecessarily extended
Solution Approach 1:
The voltage measurement selection is made dynamic rather than static. The controller continuously evaluates both voltage sensor readings and selects the one corresponding to the lower current flow path at each moment in time. This dynamic adaptation allows the system to maintain battery safety while maximizing charging speed by always using the most accurate voltage measurement available, rather than consistently using a conservative estimate that would limit charging power.
Data Source
AI summary
An electric vehicle may include a battery; an inverter; a motor; a first and second terminal configured to connect to an external power supply; a first wire connecting the first terminal to a neutral point; a second wire connecting the second terminal to the battery, a first relay disposed on the first wire; a first and second voltage sensor configured to measure a potential difference; and a controller. The controller may be configured to: calculate permissible power of the battery; calculate a first voltage value obtained by adding a first margin to a detected value by the first voltage sensor; calculate a second voltage value obtained by adding a second margin to a detected value by the second voltage sensor; and calculate a current command value to the external power supply based on the permissible power and a smaller value of the first voltage value and the second voltage value.