Electrical Converter Common Mode Voltage Cancellation
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Solution Overview
Problem
The existing electrical converter systems face limitations in torque output due to insulation stress caused by common mode voltages, which restrict the maximal torque generation and are not efficiently managed by current methods.
Innovation Solution
The method involves generating synchronized first and second common mode voltages with opposite phases, allowing them to cancel each other out, thereby reducing the overall common mode voltage stress on the converter system and enabling higher torque output without exceeding insulation capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If common mode voltage is added to phase voltages for better voltage utilization and overmodulation, then voltage utilization is improved, but insulation stress increases and maximal torque is limited
Solution Approach 1:
The patent applies overmodulation to generate common mode voltage, which normally causes insulation stress, but converts this harmful effect into a beneficial one by using the common mode voltage to increase the magnitude of phase voltages. This enables better voltage utilization and higher torque generation, transforming the typically harmful common mode voltage into a useful resource for improving converter performance
2Power
If common mode voltage is increased to generate higher torque, then torque output is improved, but insulation capabilities are exceeded
Solution Approach 1:
The patent changes the parameter of common mode voltage magnitude and timing by implementing synchronized switching between rectifier and inverter. By controlling the switching sequences and synchronizing switching points, the system generates common mode voltage with specific characteristics that enable higher torque while maintaining insulation stress within acceptable limits through precise parameter control
3Object-affected harmful factors
If switching sequences are synchronized to eliminate common mode voltage pulses, then common mode voltage is reduced, but torque generation capability is decreased
Solution Approach 1:
The patent applies partial overmodulation to generate a controlled amount of common mode voltage rather than completely eliminating it. By using partial action (controlled common mode voltage instead of complete elimination), the system achieves a balance where sufficient common mode voltage is present to enable high torque generation while keeping insulation stress within acceptable limits
Data Source
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AI summary
A converter (12) comprises a first inverter (18) for converting a first multi-phase AC voltage (30) into a DC voltage and a second inverter (20) for converting the DC voltage into a second multi-phase AC voltage (32). A method for controlling the electrical converter (12) comprises: switching the first inverter (18) such that a first common mode voltage (60) is generated in the first multi-phase AC voltage (30); switching the second inverter such that a second common mode voltage (62) is generated in the second multi-phase AC voltage (32), wherein the first common mode voltage (60) and the second common mode voltage (62) are synchronized such that the first common mode voltage (60) and the second common mode voltage (62) cancel each other at least partially.