Rotary Device Control Unit Reducing Switching Frequency
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Solution Overview
Problem
Existing control units for rotary devices, such as motor generators, face challenges in optimizing the switching frequency of power converting circuits to minimize deviation between predictive and command currents, leading to increased switching frequency and power loss.
Innovation Solution
A control unit that includes a relative rate predicting section, a determining section, and an operating section, which temporarily sets operation states of the power converting circuit, predicts the relative rate of control amounts, determines the optimal operation state based on this prediction, and operates the circuit to reduce the time required to separate the control amount from the command value, thereby decreasing the switching frequency of the switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If model predictive control is used to minimize deviation between predictive current and command current in each time, then followability to command current in transient time is improved, but switching frequency of the power converting circuit increases
Solution Approach 1:
The control method dynamically adjusts the evaluation criteria for selecting operation states based on the current situation. When the control amount is close to the command value, the system evaluates not only the deviation magnitude but also the rate of change, dynamically switching between different control priorities to minimize unnecessary switching while maintaining accuracy.
Solution Approach 2:
The invention changes the control parameter from simply minimizing current deviation to minimizing a composite metric that includes both deviation magnitude and rate of change. This parameter transformation allows the system to select operation states that reduce switching frequency while maintaining control accuracy.
2Measurement precision
If operation state is frequently changed to minimize deviation between predictive current and command current, then control accuracy is improved, but switching frequency increases
Solution Approach 1:
The system uses feedback from the relative rate calculation to adjust operation state selection. By continuously monitoring whether the control amount is approaching or diverging from the command value, the controller can make informed decisions about when to change operation states, avoiding unnecessary switching while maintaining control accuracy.
Solution Approach 2:
The control method performs preliminary evaluation of the relative rate before selecting the next operation state. By predicting the trend of deviation change, the system can proactively select operation states that will maintain accuracy without requiring frequent switching, thus reducing switching frequency in advance.
3Speed
If switching elements are turned on and off frequently to optimize control, then response speed is improved, but power loss increases
Solution Approach 1:
The system applies partial switching action by using the relative rate information to determine when full switching optimization is necessary versus when maintaining the current state is sufficient. This partial action approach reduces unnecessary switching events while maintaining adequate response speed for critical control situations.
Data Source
AI summary
In a control unit that controls a control amount of a rotary device by controlling on and off states of switching elements of a power converting circuit, a relative rate predicting section temporally sets operation states of the power converting circuit and predicts a relative rate of a control amount according to each of the temporally set operation states relative to a command value thereof. Each of the operation states is indicated by a voltage vector defined by the on and off states of the switching elements. A determining section determines an operation state of the power converting circuit based on the relative rate predicted by the relative rate predicting section. An operating section operates the power converting circuit to the operation state determined by the determining section.