Power Converter Common Mode Voltage Reduction
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Solution Overview
Problem
Current power conversion systems, particularly current source converters, face challenges in controlling common mode voltages and currents, leading to increased saturation levels in link chokes, which results in higher costs, size, and weight due to the use of space vector modulation (SVM) techniques.
Innovation Solution
The implementation of zero vector selection methods in space vector modulation (SVM) to counteract active vector common mode contributions, reducing the saturation level of SVM and optimizing the design of common mode chokes by selecting zero vectors based on computed or measured common mode contributions, and considering the operational status of the inverter as motoring or regenerating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If space vector modulation (SVM) is used for power conversion control, then the ease of operation and control simplicity is improved, but the common mode voltage and current increase causing link choke saturation
Solution Approach 1:
The patent changes the modulation parameters by selecting specific zero vectors (U7, U8, or U9) based on the sector position and operational mode (motoring or regenerating). This parameter selection modifies the common mode voltage characteristics while maintaining SVM control simplicity, thereby reducing link choke saturation without sacrificing ease of operation.
2Object-affected harmful factors
If common mode voltage control is implemented in current source converters, then the harmful effects on motors are reduced, but the device complexity increases due to additional components
Solution Approach 1:
The patent implements self-service by using the existing SVM control structure and leveraging the natural properties of zero vectors to reduce common mode voltage. The control system selectively applies zero vectors based on sector and operational mode without requiring external isolation transformers or common mode filter circuits, thereby protecting motors while avoiding additional complex components.
3Weight of stationary object
If zero vector selection is implemented to counteract common mode contributions, then the saturation level of link choke is reduced, but the manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by pre-determining the appropriate zero vector selection strategy based on the sector position and operational mode (motoring or regenerating). This pre-planned approach simplifies the control logic and reduces the precision requirements during real-time operation, as the zero vector selection follows predetermined rules rather than requiring complex real-time calculations.
Data Source
AI summary
Power conversion systems are presented with common mode reduction by space vector pulse width modulation zero vector selection to counteract common mode contribution of active vectors.