Motor Inverter Short-Circuit Sequencing to Limit D-Axis Current
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Solution Overview
Problem
Existing control apparatuses for rotating electric machines face challenges in suppressing demagnetization of permanent magnets during all-phase short-circuit control, as the operating point converges to a final arrival point along a spiral trajectory, leading to intermittent increases in d-axis current on the field-weakening side.
Innovation Solution
The proposed control apparatus performs single-phase short-circuit control prior to all-phase short-circuit control in a regenerative drive state, forming closed circuits that allow flyback current to flow, reducing the magnitude of transient d-axis current and thereby suppressing demagnetization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If all-phase short-circuit control is performed by turning on all switches of one arm group and turning off all switches of the other arm group, then the control structure is simple, but transient d-axis current increases intermittently causing demagnetization of permanent magnets
Solution Approach 1:
The patent applies preliminary action by performing single-phase short-circuit control before all-phase short-circuit control. The single-phase short-circuit control is executed in advance to reduce the magnitude of transient d-axis current that will occur during subsequent all-phase short-circuit control, thereby preventing demagnetization while maintaining the simplicity of the all-phase control structure.
Solution Approach 2:
The patent segments the short-circuit control into two distinct phases: single-phase short-circuit control and all-phase short-circuit control. This segmentation allows the system to first execute a preparatory single-phase control that reduces transient current magnitude, followed by the main all-phase control, thus resolving the contradiction between control simplicity and magnet protection.
2Reliability
If single-phase short-circuit control is performed prior to all-phase short-circuit control, then transient d-axis current magnitude is reduced suppressing demagnetization, but control process becomes more complex
Solution Approach 1:
The single-phase short-circuit control serves as a preliminary action that prepares the system for the subsequent all-phase short-circuit control. By reducing the transient d-axis current magnitude in advance, it enables the all-phase control to be executed safely without demagnetization, while the control complexity is managed through systematic sequencing of the two control phases.
Data Source
AI summary
A control apparatus is applied to a system that includes a rotating electric machine and an inverter. The inverter has, for each of a plurality of phases, upper-arm and lower-arm switches each of which has a diode connected in antiparallel thereto. The control apparatus includes an all-phase short-circuiting unit and a single-phase short-circuiting unit. The all-phase short-circuiting unit performs all-phase short-circuit control of turning on, for example, all the upper-arm switches of the plurality of phases while turning off all the lower-arm switches of the plurality of phases. The single-phase short-circuiting unit performs, in a regenerative drive state of the rotating electric machine and prior to execution of the all-phase short-circuit control, single-phase short-circuit control of turning on one of the upper-arm and lower-arm switches of one of the plurality of phases, turning off the other switch of the phase and turning off all the switches of the remaining phases.