Harmonic Controller for Rotating Electrical Machine Torque Ripple
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Solution Overview
Problem
Existing control devices for rotating electrical machines experience delays in responding to torque fluctuations, leading to steady-state deviations and inadequate damping of torque ripples, and are prone to noise interference in transient responses.
Innovation Solution
A control device utilizing a two-axis rotating coordinate system to compute current commands and feedback control units that include harmonic controllers to calculate voltage commands based on the transfer function of torque fluctuation frequencies, reducing steady-state deviations and noise influence by synchronizing with the rotating electrical machine's frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a proportional-plus-integral (PI) controller is used to track DC current commands, then the control system is simple to implement, but there occurs a delay in response to fluctuating commands resulting in steady state deviations
Solution Approach 1:
The patent changes the control parameters by introducing harmonic components at the torque fluctuation frequency into the current commands. This allows the controller to anticipate and compensate for periodic fluctuations, reducing steady state deviations while maintaining the simple PI controller structure.
Solution Approach 2:
The patent applies periodic action by adding current commands that fluctuate at the same frequency as the torque fluctuations from the internal combustion engine. This periodic compensation signal enables the system to counteract the regular torque variations, improving tracking accuracy without increasing controller complexity.
2Manufacturing precision
If a high-pass filter is used to extract fluctuating command components, then the technique can reduce torque ripple, but the transient response becomes weak and noise increases
Solution Approach 1:
Instead of using a high-pass filter to extract fluctuating components, the patent directly generates harmonic current commands based on the known torque fluctuation frequency. This approach avoids the noise amplification and transient response degradation associated with high-pass filtering while still achieving effective torque ripple reduction.
Solution Approach 2:
The patent introduces an intermediary calculation step that computes harmonic current commands using the transfer function characteristic, serving as a mediator between the torque command and the actual current control. This intermediary approach provides smooth transient response while effectively reducing torque ripple.
3Ease of operation
If the current feedback control system uses standard PI control, then the system is stable and easy to implement, but the actual output torque and currents cannot accurately track fluctuating commands
Solution Approach 1:
The patent merges the standard PI control with an additional harmonic control component. The total current command becomes the sum of the DC component from PI control and the AC harmonic component for fluctuation compensation. This combination maintains the simplicity and stability of PI control while adding the capability to accurately track fluctuating commands.
Solution Approach 2:
The patent modifies the current command parameters by superimposing harmonic components at the torque fluctuation frequency onto the standard DC current commands. This parameter enhancement allows the system to maintain simple PI controller implementation while achieving accurate tracking of fluctuating torque commands.
Data Source
AI summary
A control device for a rotating electrical machine, which is able to reduce a tracking delay of an actual output torque and actual currents with respect to a fluctuating torque command and fluctuating current commands and to reduce steady state deviations, is obtained. The control device includes a torque current computing unit; an actual current computing unit; a current feedback control unit; and a voltage control unit that controls voltages on the basis of the two-phase voltage commands. The torque command includes a fluctuation cancellation torque command for cancelling transmission torque fluctuations transmitted from the internal combustion engine, and the current feedback control unit includes a harmonic controller that calculates the two-phase voltage commands by using a characteristic of a transfer function corresponding to a periodic function of a frequency of the transmission torque fluctuations.