Voltage-Vector Dual-Inverter Control for Open-End Winding Motors
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Solution Overview
Problem
In motor driving systems using the open end winding method, circulating currents caused by common mode voltage differences between inverters lead to losses such as copper and iron losses, reducing motor efficiency.
Innovation Solution
A motor driving apparatus with a controller that combines switching vectors to eliminate common mode voltage differences between two inverters, preventing circulating currents by using specific switching states and coefficients to generate a voltage command vector for pulse width modulation control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the open end winding method is used to improve voltage utilization rate, then output power is increased, but circulating current is generated due to common mode voltage difference
Solution Approach 1:
The patent changes the control parameters by selecting specific switching vectors that satisfy the common mode voltage balance condition. By modifying the switching state parameters of the two inverters to meet the equation Vcm1 - Vcm2 = 0, the circulating current is eliminated while maintaining the open end winding configuration's power output benefits.
Solution Approach 2:
The patent converts the potentially harmful common mode voltage difference into a beneficial control constraint. By using the common mode voltage difference condition as a selection criterion for switching vectors, the method eliminates circulating current losses while preserving the high voltage utilization advantage of the open end winding method.
2Power
If the open end winding method is used to increase phase voltage, then voltage utilization rate is improved, but motor efficiency is reduced due to circulating current
Solution Approach 1:
The patent modifies the control parameters by imposing the common mode voltage balance condition on the switching vector selection. This parameter change ensures that while high phase voltage is maintained for improved voltage utilization, the circulating current that reduces motor efficiency is eliminated through coordinated switching of both inverters.
3Ease of operation
If switching vectors are selected without considering common mode voltage difference, then control is simplified, but circulating current is generated causing copper and iron losses
Solution Approach 1:
The patent changes the selection criteria for switching vectors by incorporating the common mode voltage balance condition. While this adds a constraint to the selection process, it eliminates circulating current and associated losses. The control remains relatively simple by using pre-defined switching vector tables that satisfy the balance condition.
Data Source
AI summary
A motor driving apparatus which drives a motor including a plurality of windings corresponding to a plurality of phases, respectively, includes: a first inverter including a plurality of first switching elements and connected to a first end of each of the windings; a second inverter including a plurality of second switching elements and connected to a second end of each of the windings; and a controller obtaining a vector corresponding to a voltage command of the motor by combining switching vectors which cause difference between a common mode voltage of the first inverter and a common mode voltage of the second inverter to be zero and configured to control the plurality of first switching elements and the plurality of second switching elements in a pulse width modulation method based on the obtained vector.