Multi-Sampling SVM for Power Converter Harmonic Control
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Solution Overview
Problem
Current power conversion systems, particularly in motor drives, face challenges in controlling low order harmonic distortion while allowing modulation index control, as conventional modulation techniques like SVM and TPWM suffer from high levels of 5th and 7th harmonics, which are not effectively filtered by AC filters.
Innovation Solution
The implementation of multi-sampling Space Vector Modulation (MS-SVM) techniques, where dwell time values are updated multiple times per SVM cycle, reduces low order harmonic distortion and allows for modulation index control, similar to Selective Harmonic Elimination (SHE) while maintaining control flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional SVM or TPWM modulation techniques are used, then modulation index control flexibility is achieved, but low order harmonic distortion (particularly 5th and 7th harmonics) increases significantly
Solution Approach 1:
The patent applies dynamics by making the modulation technique adaptive rather than static. The control system dynamically selects between different modulation strategies (SVM, TPWM, or hybrid) based on real-time operating conditions such as modulation index value and load requirements. This allows the system to maintain low harmonic distortion across the full range of modulation indices while preserving control flexibility, resolving the contradiction between adaptability and harmonic performance.
Solution Approach 2:
The patent changes the modulation approach parameters based on operating conditions. By adjusting the modulation technique and dwell time calculations according to the modulation index range and harmonic requirements, the system achieves low harmonic distortion at all modulation levels. The control algorithm modifies switching patterns and dwell times dynamically to eliminate specific harmonic orders while maintaining modulation flexibility.
2Object-generated harmful factors
If Selective Harmonic Elimination (SHE) is used, then low order harmonic distortion is reduced, but modulation index control flexibility is lost due to fixed modulation index requirements
Solution Approach 1:
The patent implements multi-functionality by creating a universal control system that can perform multiple modulation techniques within a single framework. The controller is designed to execute SVM, TPWM, or hybrid modulation strategies depending on conditions, making the system as versatile as conventional methods while achieving the harmonic performance of SHE. This resolves the contradiction by making the control system adaptable to different operating requirements without sacrificing flexibility.
Solution Approach 2:
The system dynamically adapts its modulation strategy based on real-time conditions rather than being fixed like traditional SHE. The control algorithm continuously evaluates operating parameters and adjusts the modulation technique accordingly, enabling both low harmonic distortion and modulation index control flexibility simultaneously through dynamic rather than static operation.
3Loss of energy
If device switching frequency is reduced to several hundred hertz or less, then device switching loss and thermal operating conditions are improved, but low order harmonic distortion increases
Solution Approach 1:
The patent changes the modulation parameters and switching patterns to eliminate low order harmonics specifically. By using advanced modulation techniques that calculate and eliminate specific harmonic orders (5th, 7th, 11th, 13th) while maintaining low switching frequencies, the system achieves both low switching loss and low harmonic distortion. The dwell time calculations and switching patterns are optimized to target specific harmonic frequencies without increasing overall switching frequency.
4Object-generated harmful factors
If AC filters are added to filter out 5th and 7th harmonics, then harmonic distortion is reduced, but device complexity and system cost increase
Solution Approach 1:
The patent converts the harmful harmonics into a controllable parameter through advanced modulation techniques. Instead of passively filtering harmonics with complex AC filters, the control system actively eliminates specific harmonic orders through intelligent switching patterns and dwell time calculations. This approach transforms the harmonic problem into a controllable aspect of the modulation strategy, reducing the need for complex filtering hardware while achieving the same harmonic reduction效果.
Solution Approach 2:
The patent replaces the mechanical/filter-based harmonic reduction approach with a control-based electronic solution. Instead of using physical AC filters to passively attenuate harmonics, the system uses intelligent control algorithms and switching patterns to actively eliminate harmonics at their source. This substitution of control electronics for passive filtering components reduces system complexity and cost while achieving superior harmonic performance.
Data Source
AI summary
Control systems, methods and power conversion systems are presented for controlling harmonic distortion, in which multi-sampling space vector modulation (SVM) is employed for controlling power converter switching devices, with a reference vector being sampled two or more times during each SVM period to update the SVM dwell times more than once during each SVM cycle.