Rotating Electrical Machine Control Device Modulation Switching
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Solution Overview
Problem
Existing rotating electrical machine control devices experience transient currents when switching between asynchronous and synchronous modulation methods, leading to increased alternating current values due to pulsation components, which destabilize waveforms and require semiconductor switching elements with high resistance, hindering inverter size reduction and cost optimization.
Innovation Solution
A rotating electrical machine control device that switches between asynchronous and synchronous modulation methods using high frequency asynchronous modulation with a carrier frequency higher than the initial frequency, improving DC-to-AC conversion resolution and stabilizing alternating current waveforms by reducing pulsations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor switching elements with high resistance characteristics are selected to withstand transient current, then reliability is improved, but inverter size increases and cost increases
Solution Approach 1:
The control device performs preliminary action by detecting the switching state and rotational speed before the transient current occurs, and preemptively switches to synchronous modulation method or adjusts PWM duty cycle to prevent the transient current from exceeding the semiconductor elements' current rating, thereby eliminating the need for oversized high-resistance components
Solution Approach 2:
The control device changes the modulation method parameter from asynchronous to synchronous based on operating conditions (switching state and rotational speed), which fundamentally alters the current waveform characteristics and prevents the harmful transient current peaks that would require larger semiconductor elements
2Ease of operation
If asynchronous modulation method is used, then ease of operation is improved, but alternating current waveform stability deteriorates due to pulsation components
Solution Approach 1:
The control device implements feedback by continuously detecting the switching state and rotational speed, and using this information to dynamically select the appropriate modulation method, thereby maintaining stable alternating current waveforms while preserving the ease of asynchronous modulation operation during suitable conditions
3Adaptability or versatility
If modulation method switching is performed, then adaptability is improved, but transient current is generated increasing alternating current maximum value
Solution Approach 1:
The control device detects the switching state and rotational speed in advance, and before the modulation method switching occurs, it prepares by switching to synchronous modulation method or adjusting PWM duty cycle to ensure the transient current remains within acceptable limits, thus maintaining adaptability while preventing harmful current peaks
Solution Approach 2:
The control device changes the modulation method parameter based on detected operating conditions, and by carefully controlling this parameter change (switching to synchronous method or adjusting duty cycle), it minimizes the transient current generation while maintaining system adaptability
Data Source
AI summary
A rotating electrical machine control device with an electronic control unit that is programmed to: switch a modulation method between asynchronous modulation in which switching of the inverter is controlled by modulated pulses generated based on a carrier having a first carrier frequency which is not synchronous with rotation of the rotating electrical machine and synchronous modulation in which switching of the inverter is controlled by modulated pulses generated in synchronization with rotation of the rotating electrical machine, the switching of the modulation method between the asynchronous modulation and the synchronous modulation being performed according to an operating condition of the rotating electrical machine which includes at least a rotational speed of the rotating electrical machine.