Open-End Winding Inverter Control for Zero-Phase Voltage Balance
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Solution Overview
Problem
The open end winding type motor driving technique struggles with controlling zero-phase component voltage, leading to the generation of common mode current, which causes losses and potential damage due to the difference in zero-phase component voltages between inverters connected to both ends of a motor winding.
Innovation Solution
A motor driving apparatus is designed with a controller that synchronizes the zero-phase component voltage between two inverters by determining an effective vector closest to the voltage command and using remote state pulse width modulation (RSPWM) to control the switching elements, ensuring the zero-phase component voltage is maintained at zero on average, thereby minimizing switching losses and common mode current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If open end winding type motor driving technique is used to increase phase voltage and improve voltage utilization rate, then power output is improved, but zero-phase component voltage cannot be controlled to become zero on average, causing common mode current generation
Solution Approach 1:
The patent applies dynamics by making the switching patterns of the two inverters time-varying and complementary. The first inverter switches during the first half of the switching period while the second inverter switches during the second half, creating a dynamic switching scheme that maintains zero-phase voltage balance while enabling high power output through open end winding configuration
Solution Approach 2:
The patent implements periodic action through synchronized switching patterns that repeat every switching period. The first and second inverters operate in complementary half-cycles within each period, ensuring that the zero-phase component voltage averages to zero while maintaining continuous high-power delivery to the motor
2Power
If inverters are connected to both ends of motor windings to increase maximum torque, then voltage utilization rate improves, but the section with high voltage utilization rate moves away from low torque region, deteriorating fuel efficiency
Solution Approach 1:
The patent enables dynamic operation across the entire torque-speed range by using two inverters that can be independently controlled. This allows the system to operate at high voltage utilization rates during high-torque conditions while maintaining fuel efficiency during low-torque conditions, as the complementary switching scheme adapts to varying load requirements
Solution Approach 2:
The patent changes the operational parameters by distributing switching actions between two inverters with complementary duty cycles. This parameter distribution allows the system to maintain optimal voltage utilization across different operating points, improving both maximum torque capability and fuel efficiency simultaneously
3Power
If common mode current is generated due to zero-phase component voltage difference, then motor efficiency decreases due to copper loss and iron loss, but in severe cases motor system damage occurs
Solution Approach 1:
The patent achieves equipotentiality by ensuring that the zero-phase component voltage of both inverters averages to zero over each switching period. This is accomplished through complementary switching patterns where the first inverter operates during the first half-cycle and the second inverter operates during the second half-cycle, eliminating potential differences that would drive common mode current
Solution Approach 2:
The patent converts the potential harm of zero-phase voltage imbalance into a benefit by deliberately designing complementary switching patterns. The switching patterns are specifically crafted to ensure that when one inverter is active, the other is inactive, and vice versa, transforming what could be a source of common mode current into a mechanism for eliminating it
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 solution effectively controls the zero-phase component voltage, reducing motor losses and preventing damage by eliminating common mode current, while also improving motor efficiency and power output.
Implementation Method 1
a switching element in the inverter is turned ON/OFF according to pulse width modulation control and applies a phase-to-phase voltage to the Y-connected windings of the motor to generate an alternating current
Implementation Method 2
using remote state pulse width modulation (RSPWM) to control the switching elements, ensuring the zero-phase component voltage is maintained at zero on average
Implementation Method 3
applies a phase-to-phase voltage to the Y-connected windings of the motor to generate an alternating current. As a result, torque is generated
Data Source
AI summary
A motor driving apparatus of driving a motor including a plurality of windings respectively corresponding to a plurality of phases is disclosed The motor driving apparatus 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 connected to the first switching elements and the second switching elements and configured to determine an effective vector closest to a voltage vector corresponding to a preset voltage command of the motor as a duty of the plurality of second switching elements and to control pulse width modulation of the first switching elements using a value obtained by adding the effective vector corresponding to the duty of the second switching elements to the voltage command of the motor as a voltage command of the first inverter.