EV Charging Power Measurement Before AC/DC Conversion Loss
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Solution Overview
Problem
Existing electric power systems face challenges in accurately measuring charging and discharging power in vehicles due to power conversion losses when converting between AC and DC power, which affects the calculation of energy transfer in vehicle-to-grid applications.
Innovation Solution
The system includes vehicles and charging stands equipped with converters and detectors that measure electric power before conversion, allowing for accurate calculation of charging and discharging power by transmitting measurement values to a server, thereby accounting for no power conversion losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric power is measured after conversion from AC to DC, then the measurement is performed at the battery side, but the measurement accuracy deteriorates due to power conversion loss
Solution Approach 1:
The patent applies preliminary action by measuring the AC power input to the charger before it is converted to DC power. The detector measures the input power at the AC side of the charger, which is the power before conversion. This preliminary measurement avoids the power conversion loss that would occur if measurement were performed after DC conversion, thereby accurately capturing the total charging power supplied to the vehicle.
2Loss of information
If both AC power measurement and DC power measurement are performed, then comprehensive data is obtained, but the calculation accuracy of charging power deteriorates due to double counting of conversion loss
Solution Approach 1:
The patent extracts only the necessary measurement data by measuring solely the AC input power to the charger. Instead of performing both AC and DC measurements and then attempting to calculate the difference, the system extracts the single critical measurement point at the AC input side. This eliminates the complexity of handling conversion loss calculations and prevents double counting errors, while still providing complete information about the charging power supplied.
3Adaptability or versatility
If power conversion is performed in the vehicle, then the vehicle can charge from AC supply, but the vehicle complexity increases due to onboard charger requirements
Solution Approach 1:
The patent uses the charger as an intermediary device that handles the AC to DC conversion externally. The charger is positioned as a separate component that converts AC power to DC power before it reaches the vehicle's battery. This intermediary approach allows the vehicle to maintain charging flexibility while reducing onboard complexity, as the conversion function is performed by the external charger rather than requiring complex onboard conversion equipment.
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
This approach enables precise calculation and management of charging and discharging power, reducing errors and operational costs by directly measuring power before conversion, ensuring accurate energy transfer and management in electric power systems.
Implementation Method 1
a first detector that detects electric power input to and output from the first charger
Implementation Method 2
a second detector that detects electric power input to and output from the second charger
Data Source
AI summary
An electric power system includes a vehicle, a vehicle management server, an AC charging stand, a DC charging stand, and a charging stand management server. During AC charging and AC discharging, the AC charging stand is connected to the vehicle. An amount of charging power during AC charging and an amount of discharging power during AC discharging are calculated by the vehicle. The vehicle measures electric power before power conversion by an on-board charger, and calculates an amount of charging power and an amount of discharging power. An amount of charging power during DC charging and an amount of discharging power during DC discharging are calculated by the DC charging stand. The DC charging stand measures electric power before power conversion by a charger, and calculates an amount of charging power and an amount of discharging power.