Electric Machine Control Device Voltage Phase Adjustment
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Solution Overview
Problem
Conventional control devices for electric rotating machines face challenges in maintaining high controllability, especially at high rotation speeds, due to discontinuous changes in voltage utilization ratios when switching between PWM and rectangular wave controls, and are not adaptable to variations in motor performance over time or due to aging.
Innovation Solution
A control device comprising a phase determining unit, a norm calculating unit, a norm correcting unit, and a torque feed-back control unit, which adjusts the phase of the controlled voltage to maintain target torque while correcting the vector norm based on actual and instructed currents, allowing smooth transitions between control modes and improving controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PWM control is used to control phase voltages in high rotation speed region, then voltage control can be achieved, but the voltage utilization ratio is limited to maximum of 1/2
Solution Approach 1:
The control device dynamically switches between PWM control and rectangular wave control based on the rotation speed and voltage requirements. In low-speed regions, PWM control provides precise voltage control, while in high-speed regions, rectangular wave control maximizes voltage utilization ratio, creating a dynamic adaptation strategy that optimizes both control precision and energy efficiency across different operating conditions
Solution Approach 2:
The invention changes the control parameter strategy by using d-q coordinate transformation to decouple voltage control into direct-axis and quadrature-axis components. This allows independent optimization of voltage magnitude and phase, enabling the system to achieve both precise voltage control and high voltage utilization ratio by adjusting the voltage vector angle and magnitude based on operating conditions
2Speed
If switching between PWM control and rectangular wave control is performed, then high rotation speed control becomes possible, but the voltage utilization ratio changes discontinuously causing torque instability
Solution Approach 1:
The control device implements dynamic control mode selection based on real-time operating conditions, smoothly transitioning between PWM and rectangular wave controls. The switching decision is made based on voltage utilization ratio thresholds and rotation speed, ensuring that transitions occur only when appropriate, thereby maintaining torque stability while enabling high-speed operation
Solution Approach 2:
The invention introduces an intermediate control strategy using d-q coordinate transformation and voltage vector control as a bridge between PWM and rectangular wave controls. This intermediary approach allows for smooth transitions by continuously adjusting the voltage vector parameters, preventing abrupt changes in voltage utilization ratio and maintaining torque stability during mode switching
3Use of energy by moving object
If pulse patterns from ROM are used to increase voltage utilization ratio, then the ratio approaches rectangular wave control values, but the pulse patterns are not appropriate for all motors due to manufacturing variations and aging
Solution Approach 1:
The control device incorporates feedback mechanisms that continuously monitor actual motor performance and adjust control parameters accordingly. By using actual current measurements and comparing them with expected values, the system adapts the voltage vector control parameters to match the specific motor characteristics, compensating for manufacturing variations and aging effects while maintaining high voltage utilization ratio
Solution Approach 2:
The invention dynamically adjusts control parameters including voltage vector angle, magnitude, and switching frequency based on real-time motor condition monitoring. This parameter adaptation allows the system to optimize voltage utilization ratio for each specific motor instance and operating condition, rather than relying on fixed pulse patterns designed for ideal motor characteristics
4Power
If maximum torque control is performed using ROM pulse patterns, then minimum current can be supplied for maximum torque, but the control cannot be performed when pulse patterns are not appropriate
Solution Approach 1:
The control device uses feedback from actual current measurements to verify whether maximum torque control is being achieved. By continuously monitoring the relationship between supplied current and generated torque, the system can detect when ROM pulse patterns are inappropriate and switch to alternative control strategies, ensuring reliable torque control while maintaining high efficiency when conditions are favorable
Data Source
AI summary
A control device has a unit for determining a controlled phase of a controlled voltage outputted from an inverter to a generator according to a difference between a target torque and an estimated torque of the generator, a unit for calculating an instructed vector norm of the controlled voltage from the target torque, an electrical angular speed of the generator and parameters indicating characteristics of the generator, a unit for correcting the instructed norm to an adjusted vector norm such that a phase of current flowing through the generator in response to the controlled voltage set at the controlled phase and the adjusted norm is controlled to a phase of an instructed current determined from the target torque, and a unit for controlling the generator by controlling the inverter to output the controlled voltage set at the controlled phase and the adjusted norm to the generator.