SPWM Control for Multilevel Converter Voltage Balancing
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Solution Overview
Problem
Multilevel converters, particularly nested neutral point clamped (NNPC) designs, face complexity in control systems due to the need for numerous calculations in space vector modulation (SVM) techniques, leading to computational delays and performance deterioration, especially at low modulation index operations.
Innovation Solution
The implementation of sinusoidal pulse width modulation (SPWM) techniques to simplify the control system complexity by selectively choosing redundant switching states based on control objectives, such as regulating flying capacitor voltages, thereby reducing computational intensity and maintaining the benefits of NNPC and other multilevel converter configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If space vector modulation (SVM) techniques are used to control and balance flying capacitor voltages, then capacitor voltage regulation is achieved, but control system complexity increases due to numerous calculations required in each switching period
Solution Approach 1:
The patent extracts the essential control function from complex SVM by identifying and implementing only the critical comparison operations needed for SPWM. This reduces the control algorithm to basic carrier-reference signal comparisons, eliminating the numerous calculations inherent in SVM while maintaining the core functionality of capacitor voltage regulation through selective switching state selection.
Solution Approach 2:
The patent changes the modulation approach from SVM's complex vector calculations to SPWM's simpler sinusoidal carrier comparisons. By transforming the control parameter space from vector-based switching sequences to sinusoidal pulse comparisons, the system achieves the same regulatory function with significantly reduced computational complexity.
2Reliability
If space vector modulation (SVM) techniques are used for flying capacitor voltage control, then voltage balancing is achieved, but computational delays occur that deteriorate control system performance
Solution Approach 1:
The patent extracts only the essential timing-critical comparison operations from SVM, removing the computationally intensive vector calculations. This leaves a streamlined SPWM implementation that performs only the necessary carrier-signal comparisons, dramatically reducing computational delay while preserving the voltage balancing function through selective redundant switching state utilization.
Solution Approach 2:
The patent skips the intermediate complex calculation steps of SVM by directly implementing sinusoidal pulse width modulation. This allows the control system to rush through the essential comparison and switching decisions without the computational overhead of full SVM processing, thereby reducing latency and improving real-time control performance.
3Measurement precision
If redundant switching states are utilized for capacitor voltage regulation, then voltage control precision is improved, but control algorithm complexity increases
Solution Approach 1:
The patent applies local quality by selectively utilizing redundant switching states only when needed for capacitor voltage regulation, rather than processing all possible switching combinations. The control algorithm examines the specific voltage balance requirements and activates redundant state selection locally, maintaining precision where needed while avoiding unnecessary complexity elsewhere in the control system.
Data Source
AI summary
Sinusoidal pulse width modulation (SPWM) control techniques, computer readable mediums, and apparatus are presented for operating a multilevel converter, in which a desired AC node voltage level is determined through comparison of a plurality of carrier signals or values to at least one reference signal or value, and a switching state is selected from a plurality of redundant switching states corresponding to the desired AC node voltage level for generating switching control signals based at least partially on a switched capacitor voltage balancing goal or other control objective.