AC Motor Inverter Restart Control After All-Phase Short Circuit
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Solution Overview
Problem
Existing AC rotary electric machine controllers face issues with control accuracy and torque fluctuation when switching from an all-phase short circuit state to switching control, due to the influence of currents flowing during the short circuit state not being considered, leading to deteriorated current control accuracy and rotational angle estimation.
Innovation Solution
A controller for AC rotary electric machines that includes a current detection unit, a current command value calculation unit, and an inverter control unit, which sets current command values to switching current values corresponding to currents flowing during the all-phase short circuit state, thereby minimizing current deviations and torque fluctuations during the transition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the inverter is restarted from the three-phase short circuit state without considering the influence of short circuit currents, then the restarting operation is simple, but the control accuracy of current deteriorates and torque fluctuation occurs
Solution Approach 1:
The patent applies preliminary action by calculating and setting the current command values to switching current values before restarting the inverter from the three-phase short circuit state. This preliminary setting of current command values based on the short circuit state prevents current deviations and torque fluctuations during the transition, thereby maintaining current control accuracy while enabling simple restarting operation.
2Reliability
If the inverter is stopped after windings are short-circuited to prevent regenerative current, then overcharge of the battery is prevented, but the system cannot handle systems where induced voltage exceeds power source voltage
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the switching state of the inverter based on the relationship between induced voltage and power source voltage. When the induced voltage is lower than the power source voltage, the inverter is stopped to prevent regenerative current and battery overcharge. When the induced voltage exceeds the power source voltage, the inverter is restarted with appropriately set current command values to handle the higher voltage condition. This parameter-based conditional control enables both battery protection and system versatility.
Data Source
AI summary
To provide a controller for AC rotary electric machine which can suppress that the control accuracy of current is deteriorated, when switching from the all phase short circuit state to the switching control. A controller for AC rotary electric machine calculates voltage command values based on current command values and current detection values; carries out switching between a switching control that turns on and off plural switching devices provided in the inverter based on the voltage command values, and all phase short circuit control that turns on and off the plural switching devices so that the plural-phase windings are short-circuited mutually; and when switching from the all the phase short circuit control to the switching control, sets the current command values to switching current values which are current values corresponding to currents which flow in executing the all phase short circuit control.