Battery Charger Current Setpoint Control for Voltage Imbalance
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Solution Overview
Problem
Existing electric and hybrid vehicle battery charging systems face challenges in managing instantaneous active power setpoints and voltage imbalances in three-phase electrical networks, leading to inefficiencies and unbalanced current absorption.
Innovation Solution
A method is developed to determine current setpoints at the input of a rectifier with reactive power compensation, using line-to-line voltage measurements to generate filtered current setpoints that compensate for network imbalances, involving a series of calculations and filtering steps to achieve stable and balanced power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional rectifiers are used in three-phase electrical networks, then power delivery is provided, but voltage imbalances and harmonic distortions occur due to unbalanced current absorption
Solution Approach 1:
The control system continuously monitors the three-phase voltages and uses this feedback to dynamically adjust the current setpoints. By measuring the actual voltage conditions and comparing them with ideal balanced conditions, the system generates compensating current references that actively counteract the voltage imbalances and prevent harmonic distortions at the point of common coupling.
Solution Approach 2:
The system changes the current setpoint parameters based on the detected voltage conditions. By calculating adjusted current references that account for the instantaneous voltage imbalances, the rectifier adapts its operating parameters to maintain balanced power flow and eliminate harmful harmonics while delivering reliable power.
2Productivity
If current setpoints are generated without filtering, then power delivery is achieved, but instantaneous variations and imbalances are not compensated
Solution Approach 1:
The control system performs preliminary calculations to generate filtered current setpoints before the rectifier operates. By pre-processing the voltage measurements and computing the adjusted current references in advance, the system ensures that the rectifier receives stable, balanced current setpoints that already account for voltage imbalances, maintaining both productivity and stability.
3Ease of operation
If additional quantities such as rotating marker phase are used to control the rectifier, then current setpoints can be generated, but device complexity increases
Solution Approach 1:
The invention extracts only the essential information needed for control by directly using the three-phase voltage measurements to generate current setpoints. By eliminating the need for additional quantities like rotating marker phase and focusing solely on the voltage inputs, the system achieves effective rectifier control with reduced complexity, removing unnecessary intermediate variables and control steps.
Data Source
Figure 1~2
AI summary
This method for determining at least one current setpoint (I * a , I * b , I * c ) from at least one voltage measurement (U ab ,U bc ,U ca ) from a rectifier (6) and at least one instantaneous active power setpoint (P req ) comprises a first calculation step (I) of the at least one current setpoint (I * a , I * b , I * c ); a second step (II) of adaptive filtration of the at least one current setpoint, and a third step (III) of limiting the variation rate of the at least one current setpoint (I * a , I * b , I * c ). The invention applies to battery chargers for electric or hybrid vehicles.