Matrix Converter Voltage Accuracy Using Segmented PWM
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Solution Overview
Problem
Existing matrix converters face challenges in accurately generating voltage, especially when the voltage command is low, leading to reduced efficiency and accuracy in motor drive applications.
Innovation Solution
A matrix converter with a bidirectional switch having self-arc-extinguishing capability, an input voltage detector group, a gate driver, and a controller with pulse width modulation and commutation operation units, which directly connects alternating current source phases to output phases, allowing for efficient pulse-width-modulation of output phases using all or selected input phases to improve voltage accuracy and reduce switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PWM cyclo-converter methods are used, then voltage can be generated, but voltage accuracy deteriorates when voltage command is low
Solution Approach 1:
The PWM operation is segmented into different modes based on voltage command levels. When voltage command is high, three-phase PWM is used; when voltage command is low, two-phase PWM is used. This segmentation allows optimal performance for each operating condition, improving voltage accuracy while managing switching losses effectively.
Solution Approach 2:
The converter dynamically switches between different PWM operation modes (three-phase and two-phase) based on the voltage command level. This dynamic adaptation enables the system to maintain high voltage accuracy across varying operating conditions while optimizing switching loss characteristics for each mode.
2Reliability
If three-phase PWM is used for all output phases, then voltage control is comprehensive, but switching losses increase
Solution Approach 1:
Instead of applying three-phase PWM to all output phases uniformly, the invention applies PWM control selectively: three-phase PWM for high voltage commands and two-phase PWM for low voltage commands. This partial application of the more complex control method reduces switching losses while maintaining sufficient voltage control accuracy for each operating condition.
3Device complexity
If bidirectional switches without self-arc-extinguishing capability are used, then device complexity is reduced, but reliability deteriorates due to arc extinction issues
Solution Approach 1:
The bidirectional switches are designed with self-arc-extinguishing capability, allowing them to automatically extinguish arcs without external assistance. This self-service mechanism improves reliability by ensuring consistent arc extinction behavior while avoiding the need for additional complex external arc extinction circuits or mechanisms.
Data Source
AI summary
A matrix converter includes a matrix converter main circuit, an input voltage detector group configured to detect an input voltage of an alternating current source, a gate driver configured to drive a bidirectional switch, and a controller having a pulse width modulation operation unit and a commutation operation unit. The pulse width modulation operation unit is configured to fix one output phase in a conduction state, configured to pulse-width-modulate one of remaining two output phases by using all three input phases, and configured to pulse-width-modulate the other output phase by using only two input phases of a reference input voltage and a middle input voltage.