Multi-Phase Rotary Device Controller with Pseudo Duty Calculation
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Solution Overview
Problem
Existing controllers for multi-phase rotary devices face challenges in stabilizing control and reducing process load while ensuring sufficient current detection time, particularly due to frequent interruption processes and increased noise and vibration.
Innovation Solution
A controller with a pseudo duty calculation device that calculates update duty values at a frequency M times larger than the calculation period, using a linear compensation method to reduce calculation load and increase comparison frequency with the carrier wave, and adjusts average voltage to ensure minimum detection time for current detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the calculation cycle of the duty command value is brought closer to the cycle of the PWM carrier wave to stabilize control and reduce noise, then control stability and noise reduction are improved, but the process load increases due to frequent interruption processes
Solution Approach 1:
The patent segments the duty command value calculation into multiple update duty values generated at different timing within one control cycle. Instead of calculating all duty values at once through frequent interruptions, the system divides the calculation into smaller units that can be processed sequentially, reducing the peak process load while maintaining control stability.
Solution Approach 2:
The patent performs preliminary calculation of update duty values based on previous duty command values before the actual control execution. By pre-calculating these values and storing them, the system avoids the need for frequent high-load interruption processes during critical control moments, thereby reducing process load while maintaining stability.
2Measurement precision
If the duty command value is modified to secure sufficient current detection time, then current detection accuracy is improved, but the voltage utilization coefficient deteriorates
Solution Approach 1:
The patent dynamically adjusts the average voltage of the duty command value based on the detected on-state time of switching devices. When the on-state time is insufficient for accurate current detection, the system modifies the average voltage to extend the on-state time, ensuring adequate detection time while minimizing the impact on voltage utilization through adaptive control.
Solution Approach 2:
The patent changes the parameter of average voltage in the duty command value to control the on-state time of switching devices. By adjusting this parameter, the system ensures that the on-state time meets the minimum requirement for current detection accuracy while optimizing the overall voltage utilization efficiency of the inverter system.
3Device complexity
If multiple update duty values are generated in one control cycle to reduce process load, then process load is reduced, but current detection time may become insufficient for the updated duty values
Solution Approach 1:
The patent implements a feedback mechanism where each update duty value is evaluated based on whether its corresponding switching device maintains sufficient on-state time for current detection. If detection time is insufficient, the system provides feedback to adjust the average voltage of subsequent update duty values, ensuring that current detection accuracy is maintained even with multiple updates per cycle.
Data Source
AI summary
A controller includes: an inverter having switching devices for converting by a PWM method and supplying an electric power to a multi-phase rotary device; a duty calculator calculating a duty command value with To; a pseudo duty calculator calculating a N-th update duty value based on N-th and (N−1)-th duty command values according to a ratio of To/Tr with a linear compensation method; a comparator comparing the update duty value with a carrier wave to generate an on-off signal of each switching device; and a detector detecting current of each phase with To. The duty calculator changes an average voltage of each phase to make an on-state time of a detection side switching device equal to or longer than minimum. When the on-state time at one phase is smaller than minimum, the pseudo duty calculator outputs a pseudo duty value to detect the current of other phases.