Voltage Command Modification for Electric Machine Fault Response
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Solution Overview
Problem
Existing electric machine drive systems face inefficiencies and oscillations in torque and current during fault conditions, particularly in the field-weakening region, where short-circuit fault responses lead to undesirable stator current and torque oscillations, and phase current overshoot.
Innovation Solution
A method for generating voltage command signals that involves a current regulator module, a voltage command modification module, and a timer to adjust voltage commands based on transient stator voltage conditions, allowing for smooth transitions and reduced oscillations by outputting modified or held voltage commands during specific timer intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a short-circuit fault response is applied at the inverter module during field-weakening region operation, then the machine can respond quickly to fault conditions, but stator current and torque oscillations occur
Solution Approach 1:
The control system determines in advance whether to apply open-circuit or short-circuit fault response based on the machine's operating speed. For medium to high speeds in the field-weakening region, short-circuit response is pre-determined as the appropriate fault handling method, allowing immediate application without delay while avoiding current oscillations through proper timing control.
Solution Approach 2:
The invention changes the control parameter by switching between different fault response modes (open-circuit vs. short-circuit) based on the machine's speed parameter. This parameter-based control strategy optimizes fault response by selecting the appropriate mode for the current operating conditions, preventing current oscillations in the field-weakening region while maintaining fast response capability.
2Speed
If voltage command signals are updated rapidly during fault conditions, then control responsiveness is improved, but current regulation robustness deteriorates due to oscillations
Solution Approach 1:
The invention dynamically adjusts the voltage command update strategy based on operating parameters. During fault conditions in the field-weakening region, the system modifies how voltage commands are updated and applied, changing the control parameters to prevent current oscillations while maintaining appropriate responsiveness to the fault condition.
3Reliability
If all switches in the multi-phase inverter are controlled to be open during open-circuit fault response, then uncontrolled regeneration is avoided, but torque response is minimized excessively
Solution Approach 1:
Instead of applying the traditional open-circuit fault response (all switches open) during field-weakening region operation, the invention inverts the approach by applying short-circuit fault response. This reverses the conventional fault handling strategy, connecting all phases to a single bus instead of opening all switches, thereby avoiding excessive torque minimization while still preventing uncontrolled regeneration through proper control.
Data Source
AI summary
Embodiments of the present disclosure relate to methods, systems and apparatus for generating voltage command signals for controlling operation of an electric machine. The disclosed embodiments can reduce current and torque oscillation, which can in turn improve machine efficiency and performance, as well as utilization of the DC voltage source.