Adaptive Current Regulator for AC Motor Stability
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Solution Overview
Problem
Current regulators for AC motors face instability and performance degradation at low sampling frequencies, particularly in hybrid electric vehicles, due to limitations in switching and sampling frequencies, leading to sub-optimal current regulation and torque production.
Innovation Solution
A current regulator architecture that dynamically switches between complex vector current regulator (CVCR) and state feedback decoupling (SFbD) configurations based on motor speed, enabling cross-coupling gain blocks and decoupling voltage adjustments to optimize performance across varying operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If synchronous frame current regulators are used for current control of AC motors, then dynamic control over a wide frequency range is achieved, but stability decreases as the ratio of sampling frequency to fundamental frequency decreases
Solution Approach 1:
The patent applies dynamics by making the current regulator configuration adaptive to operating conditions. The system dynamically switches between different regulator configurations (e.g., synchronous frame current regulator with virtual damping resistance versus alternative configurations) based on the ratio of sampling frequency to fundamental frequency. This allows the system to maintain stability across a wide frequency range by selecting the appropriate configuration for each operating condition, rather than using a fixed configuration that would compromise stability at certain frequencies.
2Power
If a high pole-count electric motor is used to produce high torque within a limited volume, then torque density increases, but the fundamental frequency increases which reduces the sampling frequency to fundamental frequency ratio
Solution Approach 1:
The patent applies parameter changes by modifying the current regulator configuration parameters based on operating conditions. When the fundamental frequency increases (due to high pole-count motor operation), the system adjusts parameters such as virtual damping resistance values or switches to alternative regulator configurations that are stable at higher frequency ratios. This allows the high pole-count motor to operate effectively while maintaining current regulator stability across the extended frequency range.
3Reliability
If virtual damping resistance is set to a constant value to reduce parameter sensitivity, then disturbance rejection improves, but the maximum achievable virtual damping resistance is limited by minimum sampling frequency condition
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant virtual damping resistance to a dynamic adaptive approach. The system adjusts the virtual damping resistance value or switches between different regulator configurations based on the operating condition, specifically the ratio of sampling frequency to fundamental frequency. This allows the system to achieve high disturbance rejection when conditions permit while maintaining stability across the full operating range, overcoming the limitation of constant virtual damping resistance.
Data Source
AI summary
A current regulator is provided for an electric machine drive system for driving an electric machine. The current regulator is configurable to operate in a first configuration or a second configuration depending on a synchronous speed of the electric machine. A controller can configure an operational mode of the current regulator by selecting, based on the synchronous speed of the electric machine, either the first configuration of the current regulator or the second configuration of the current regulator as a currently active configuration, and can then execute the current regulator in accordance with the currently active configuration. The first configuration of the current regulator comprises a first set of elements and cross-coupling gain blocks, whereas the second configuration of the current regulator can include the first set of elements without the cross-coupling gain blocks. The first set elements can vary depending on the implementation, but can generally include: summing junctions, integrators, and gain blocks. In one embodiment, the current regulator is configured to operate as a complex vector current regulator when configured in the first configuration, and is configured to operate as a state feedback decoupling (SFbD) current regulator when configured in the second configuration.