Switched Reluctance Motor Torque Ripple Suppression
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Solution Overview
Problem
Conventional direct torque control of switch reluctance motors faces challenges in achieving smooth torque output due to the strict requirements of the turn-off angle of the main switch, making it difficult to maintain maximum smooth torque without generating negative torque, and existing methods are impractical.
Innovation Solution
A method for torque pulsation two-level suppression in four-phase switch reluctance motors is introduced, where two groups of torque thresholds and excitation states are set for adjacent phases, allowing them to switch between positive and negative supply excitation voltages, controlling the total torque within specific ranges without relying on the turn-off angle of the main switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the turn-off angle of the main switch is advanced to establish current quickly, then the current increases at maximum rate, but the torque is lower than expected and the output torque smoothness deteriorates
Solution Approach 1:
The commutation process is divided into two distinct intervals: current buildup interval (where phase A is excited to establish current quickly) and current decay interval (where phase A is de-excited to avoid negative torque). This segmentation allows each interval to be optimized independently for its specific function, resolving the contradiction between fast current rise and precise torque control.
Solution Approach 2:
The method determines the turn-off angle of phase A in advance based on the conduction angle of phase B, before the actual commutation occurs. This preliminary determination ensures that phase A is turned off at the optimal moment to maintain positive torque while allowing phase B to build current at maximum rate, thus pre-resolving the timing conflict between current establishment and torque maintenance.
2Reliability
If the turn-off angle of the main switch is lagged to avoid negative torque, then the current decreases at maximum rate, but the current cannot reach the specified level and torque is lower than expected
Solution Approach 1:
The method dynamically adjusts the turn-off angle of phase A based on the actual conduction angle of phase B and the instantaneous torque requirements. Rather than using a fixed turn-off angle, the system adaptively determines the optimal turn-off moment, allowing phase A to remain excited longer when needed to maintain torque positivity while still ensuring current decay before negative torque region entry.
Solution Approach 2:
The method uses feedback from the conduction angle detection of phase B to determine the appropriate turn-off angle for phase A. The control system continuously monitors phase B's conduction state and uses this information to adjust phase A's turn-off timing, creating a closed-loop control that maintains both torque positivity and adequate torque output level.
3Manufacturing precision
If offline calculation or online adjustment is used to determine the turn-off angle, then torque smoothness can be improved, but the system complexity and control difficulty increase
Solution Approach 1:
The system uses the naturally occurring commutation process between phases to automatically determine the turn-off angle of phase A based on the conduction angle of phase B. The control method leverages the inherent timing relationships in the multi-phase commutation sequence, allowing the system to self-regulate the turn-off angle without requiring complex external calculation or adjustment mechanisms, thus achieving torque smoothness with minimal added complexity.
4Manufacturing precision
If a strict turn-off angle requirement is imposed on the main switch, then torque control precision can be maintained, but the method practicability deteriorates
Solution Approach 1:
The method changes the control parameter from a fixed, strict turn-off angle requirement to a flexible, dynamically determined turn-off angle based on phase B's conduction angle. By transforming the control parameter from a static specification to a dynamic variable that adapts to operating conditions, the system maintains torque control precision while significantly improving practicability and ease of implementation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables smooth control of instantaneous torque, inhibits torque pulsation, and matches actual excitation voltage and current waveforms with expected waveforms, improving practicability and applicability across different switch reluctance motor systems.
Implementation Method 1
Four-phase switch reluctance motor torque ripple two-level suppression method
Data Source
AI summary
A four-phase switched reluctance motor torque ripple two-level suppression method in which power is supplied to adjacent phase A and phase B for excitation. The power supplied for excitation to phase A leads the power supplied for excitation to phase B by θr/4. An entire commutation process from phase A to phase B is divided into two intervals, phase A which uses the second set of torque thresholds while phase B uses the first set of torque thresholds. Critical position θ1 automatically appears in the commutation process, thus obviating the need for additional calculations. Total torque is controlled between [Te+th2low and Te+th2up]. In rotor position interval [θ1, θr/4], phase A continues to use the second set of torque thresholds, phase B continues to use the first set of torque thresholds, and the total torque is controlled between [Te+th1low and Te+th1up].