Rotary Machine Control Reducing Harmonic Currents
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling rotary machines do not effectively cancel harmonic current components in phase currents using on-off switching patterns, leading to torque variations and iron loss.
Innovation Solution
An apparatus that sets the phase of the output voltage vector in a rotating coordinate system, selects appropriate on-off switching patterns based on the amplitude of the output voltage vector, and superimposes a fluctuating signal to induce counteracting harmonic current components, reducing the target harmonic current component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional PWM control or basic on-off switching patterns are used, then the control system is simple, but harmonic current components cannot be effectively cancelled leading to torque variations and iron loss
Solution Approach 1:
The patent segments the control approach by dividing the switching pattern selection into multiple discrete amplitude levels (first amplitude level, second amplitude level, etc.). Each amplitude level has predetermined on-off switching patterns stored in memory, allowing the system to select appropriate patterns based on the current output voltage amplitude without requiring complex real-time calculations.
Solution Approach 2:
The patent changes the control parameter from continuous PWM duty cycle adjustment to discrete switching pattern selection based on amplitude levels. The phase setter determines the phase of the output voltage vector, and based on this phase and the current amplitude level, the system selects from predetermined switching patterns. This parameter change simplifies the control logic while enabling effective harmonic cancellation through proper phase alignment of switching patterns.
2Ease of operation
If on-off switching patterns are used without phase adjustment, then the control method is simple, but harmonic current components in phase current cannot be cancelled
Solution Approach 1:
The patent implements feedback control through the phase setter, which continuously determines the phase of the output voltage vector based on the actual operating conditions. This phase information is fed back to the switching unit, which selects and shifts switching patterns accordingly. The feedback mechanism ensures that the switching patterns remain synchronized with the actual voltage vector phase, enabling effective harmonic current cancellation while maintaining operational simplicity.
Solution Approach 2:
The patent applies preliminary action by pre-calculating and storing multiple on-off switching patterns in memory for different amplitude levels before operation. These patterns are predetermined based on expected operating conditions and are ready for immediate selection. The phase setter determines the appropriate phase shift in advance, and the switching unit simply retrieves and applies the pre-prepared patterns with the calculated phase shift, eliminating the need for complex real-time pattern generation.
3Object-generated harmful factors
If PWM control with duty cycle adjustment is used, then harmonic current components can be controlled, but the control system becomes more complex
Solution Approach 1:
The patent replaces the complex, continuous PWM duty cycle adjustment mechanism with simpler, discrete switching pattern selection. Instead of continuously varying duty cycles and performing complex real-time calculations, the system uses predetermined switching patterns that are selected and applied in discrete steps based on amplitude levels. This approach achieves harmonic current control with significantly reduced computational complexity and simpler control logic.
Data Source
AI summary
In a control apparatus, a target harmonic current obtainer obtains, according to a phase current flowing through at least one phase winding of a stator, a target harmonic current component flowing in a rotary machine. The target harmonic current component is included in a fundamental current component of the phase current. An inducing unit superimposes, on the phase information, a fluctuating signal that changes at an angular velocity identical to an angular velocity of the target harmonic current component, to induce a counteracting harmonic current component in the at least one phase winding. The counteracting harmonic current component counteracts the target harmonic current component.