Three Phase PWM Cycloconverter Mode Switching
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Solution Overview
Problem
Conventional matrix converters face issues with output voltage and current distortions due to reduced PWM pulse width, voltage drops, and complex control methods, which hinder efficient power conversion and vector control.
Innovation Solution
A power converter employing a mode switching mechanism between one-phase fixing and full phase switching modes, along with a space vector-based calculation method, to manage PWM pulse patterns and reduce distortions, utilizing a bidirectional switch with self-extinction capability for efficient AC power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PWM pulse width is reduced to stop one-phase switching, then switching loss is reduced, but output voltage and current distortions increase
Solution Approach 1:
The patent dynamically switches between one-phase fixing switching mode and full phase switching mode based on operating conditions. When output voltage is high, one-phase fixing mode is used to reduce switching loss. When output voltage is low, full phase switching mode is used to maintain adequate PWM pulse width and reduce distortion. This dynamic adaptation resolves the contradiction between switching loss and output quality.
Solution Approach 2:
The patent changes the switching mode parameter based on output voltage level. By monitoring output voltage and switching between different modes (one-phase fixing vs full phase), the system adapts to maintain optimal performance across different operating conditions, reducing distortion when needed while minimizing switching loss when possible.
2Device complexity
If commutating sequence is created based on voltage polarity signal, then switching control is simplified, but error between voltage command value and output voltage increases
Solution Approach 1:
The patent uses feedback from output voltage detection to correct the commutating sequence. By detecting actual output voltage and comparing it with command values, the system adjusts timing and switching signals to compensate for errors introduced by simplified voltage polarity-based control, thereby maintaining accuracy while keeping control relatively simple.
Solution Approach 2:
The patent pre-calculates and stores optimal commutating sequences for different operating conditions. By preparing switching sequences in advance based on expected voltage polarities and output requirements, the system reduces real-time computational complexity while maintaining precision through pre-optimized control strategies.
3Device complexity
If bidirectional switch is used for AC power conversion, then circuit structure is simplified, but voltage drop occurs due to semiconductor device characteristics
Solution Approach 1:
The patent changes operating parameters including switching frequency and duty cycle to compensate for voltage drops in bidirectional switches. By adjusting PWM parameters dynamically, the system compensates for semiconductor on-resistance effects while maintaining the simplified bidirectional switch circuit structure.
4Ease of operation
If space vector calculation method is used, then control processing becomes reliable and easy, but computational requirements increase
Solution Approach 1:
The patent segments the control calculation into modular space vector components that can be processed systematically. By dividing the complex control task into standardized space vector calculations for different switching modes, the system achieves reliable and easy control processing while managing computational requirements through structured methodology.
Data Source
AI summary
A power conversion method comprising detecting a three-phase source voltage of the three-phase AC power supply every control sampling cycle. The three-phase source voltage is allocated to a maximum voltage, an intermediate voltage and a minimum voltage as seen from a virtual neutral point voltage. A one-phase fixing switching mode is detected for fixing one of output phases into a predetermined state without switching and switching the other phases during a PWM cycle or a full phase switching mode for switching all of the phases during the PWM cycle based on an output voltage command and the three-phase source voltage. ON/OFF pattern of a bidirectional switch is determined from the switching mode thus selected, the output voltage command and the three-phase source voltage. The bidirectional switch is turned ON/OFF based on the ON/OFF pattern.