Reduced Control Cycle Current Regulator for IPM Motor
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Solution Overview
Problem
Existing current regulators for vehicle electric traction motors with interior permanent magnet (IPM) motors require multiple control cycles to achieve current commands, leading to overshoot, lag, and vibration due to operating point-dependent parameters and saturation effects, which are not effectively addressed by prior discrete control strategies.
Innovation Solution
A reduced control cycle current regulator that uses a model inverse method with parameter lookup tables or polynomial functions to adjust transfer function parameters based on feedback, enabling accurate current injection in one or two control cycles by accounting for operating point dependence and saturation, employing a forward prediction filter, differentiator, and look-up tables to mitigate speed-dependent errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional current regulator is used for IPM motor control, then the control system can operate, but it requires multiple control cycles to achieve current commands, causing overshoot, lag, and vibration
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing transfer function parameters (inductance and resistance values) in lookup tables before operation. During control cycles, the system retrieves pre-computed parameters based on operating conditions (current magnitude and shaft speed) rather than calculating them in real-time. This preparation in advance enables the current regulator to achieve accurate current commands in one or two control cycles, eliminating overshoot and lag without requiring multiple iterative adjustments.
2Ease of manufacture
If discrete control strategies are used, then the control implementation is simple, but they cannot effectively address operating point-dependent parameters and saturation effects
Solution Approach 1:
The patent implements parameter changes by dynamically adjusting transfer function parameters (inductance Ld, Lq and resistance Rs) based on operating conditions. Lookup tables store pre-computed parameter values corresponding to different current magnitudes and shaft speeds. The system selects appropriate parameters based on real-time operating point feedback, enabling accurate control across varying conditions including saturation effects. This approach maintains implementation simplicity through table lookup while achieving high precision by adapting parameters to actual operating conditions.
Solution Approach 2:
The system employs feedback mechanisms where the actual current magnitude and shaft speed are continuously measured and fed back to the current regulator. This feedback enables the system to identify the current operating point and select appropriate transfer function parameters from lookup tables. The feedback loop ensures that parameter changes are synchronized with actual motor conditions, maintaining control precision across the entire operating range while keeping the control structure manageable through systematic parameter selection.
3Device complexity
If fixed transfer function parameters are used, then the control algorithm is simple, but speed-dependent errors occur in direct-axis and quadrature-axis current control
Solution Approach 1:
The patent applies dynamics by transitioning from fixed transfer function parameters to dynamic parameters that adapt to changing operating conditions. Lookup tables store transfer function parameters (inductance and resistance) corresponding to different shaft speeds and current magnitudes. The system dynamically selects appropriate parameters based on real-time feedback of actual operating conditions. This dynamic parameter adaptation eliminates speed-dependent errors in direct-axis and quadrature-axis current control while maintaining algorithm simplicity through systematic table lookup and parameter selection based on operating point.
Data Source
AI summary
A system in a vehicle includes a current regulator to obtain current commands from a controller based on a torque input and provide voltage commands and an inverter to use the voltage commands from the current regulator and direct current (DC) supplied by a battery to provide alternating current (AC). The system also includes an electric traction motor to provide drive power to a transmission of the vehicle based on injection of the AC from the inverter. The current regulator adjusts parameters of a transfer function implemented by the current regulator, based on feedback of an input to and an output from the electric traction motor to achieve the AC corresponding with the torque input in no more than two control cycles.