Four Quadrant Voltage Limiter for Rotor Flux Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing control architectures for electrical inverters lose machine control and result in excessive phase current when commanded volt-seconds exceed the inverter's capability, particularly at high machine speeds or low inverter DC link voltages, leading to overcurrents and loss of torque control during motoring and regeneration.
Innovation Solution
A four-quadrant voltage limiter is implemented, which limits the phase voltage within the inverter's capability by maintaining rotor flux and folding back torque under both motoring and regeneration torque commands, enforcing an upper limit for q-axis voltage during motoring and a lower limit during regeneration to prevent overcurrents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the commanded volt-seconds exceed the inverter's capability, then the machine control is lost, but excessive phase current flows causing overcurrents
Solution Approach 1:
The voltage limiter proactively prevents overcurrent conditions by limiting the commanded phase voltage to within the inverter's capability before excessive current can flow. This preliminary action maintains machine control reliability by ensuring voltage commands never exceed what the inverter can deliver, particularly at high speeds or low DC link voltages where voltage saturation would otherwise cause control loss and harmful overcurrents.
2Power
If the q-axis voltage is not limited during motoring operation, then torque generation is maximized, but the inverter voltage capability is exceeded
Solution Approach 1:
The voltage limiter dynamically adjusts the q-axis voltage command based on the inverter's instantaneous voltage capability, which varies with operating conditions such as DC link voltage and machine speed. By continuously adapting the voltage limit rather than using a fixed constraint, the system maximizes torque generation within the available voltage headroom while preventing inverter saturation and maintaining reliable operation across the full operating range.
3Power
If the q-axis voltage is not limited during regeneration operation, then regenerative torque is maximized, but overcurrents occur
Solution Approach 1:
During regeneration, the voltage limiter applies a preliminary constraint on the q-axis voltage to prevent the inverter from entering a voltage-saturated state that would cause control loss and harmful overcurrents. By proactively limiting the voltage command to within available capability, the system maintains reliable regenerative torque generation while preventing the harmful overcurrent condition that would otherwise occur when voltage commands exceed inverter output capacity.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Methods, systems and computer readable storage devices for a four quadrant voltage limiter that limits a commanded phase voltage to within a volt second capability of an inverter by maintaining a rotor flux and folding back a torque under both motoring and regeneration torque commands. In one embodiment: (a) in a motoring operation, an upper limit for a q-axis voltage is enforced; and (b) in a regeneration operation a lower limit for the q-axis voltage is enforced.