Inverter Control Reducing Power Loss and Current Distortion
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Solution Overview
Problem
Existing power conversion devices face issues with power loss and distortion of AC current when there is a phase difference between AC voltage and AC current, and they struggle to maintain efficient operation without short-circuiting the output of the full-bridge circuit.
Innovation Solution
A power conversion device with a full-bridge circuit and a short-circuit section, controlled by a controller that divides the control cycle into four periods to manage switching operations and freewheeling diodes, reducing power loss and distortion by ensuring appropriate voltage application and minimizing the amplitude of pulse voltage across the AC reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a full-bridge circuit with short-circuit section is used for power conversion, then conversion efficiency is improved, but power loss and AC current distortion occur when there is a phase difference between AC voltage and AC current
Solution Approach 1:
The patent applies dynamic control by switching between two operational modes based on the phase difference condition. When phase difference exceeds a threshold, the system dynamically transitions to a second control mode that prevents short-circuiting, thereby maintaining operational stability while minimizing power loss across varying operating conditions
Solution Approach 2:
The controller changes operational parameters (switching states of full-bridge circuit and short-circuit section) based on the detected phase difference. By monitoring and responding to parameter changes in the AC voltage and current waveforms, the system adjusts its operation to prevent harmful short-circuit conditions while maintaining efficiency
2Power
If switching operation is performed to enable power conversion, then power conversion capability is improved, but switching power loss increases
Solution Approach 1:
The patent employs periodic switching operations with optimized timing. By controlling the switching frequency and duty cycle of the full-bridge circuit, the system achieves effective power conversion while minimizing switching losses through periodic operation at optimal intervals
Solution Approach 2:
The short-circuit section provides continuous current paths during freewheeling periods, maintaining useful action without requiring continuous high-frequency switching. This continuity reduces the number of switching events needed, thereby reducing switching power loss while maintaining power conversion capability
3Productivity
If short-circuit section is used to improve efficiency, then conversion efficiency is improved, but distortion of AC current occurs when phase difference exists
Solution Approach 1:
The system dynamically adjusts the operation of the short-circuit section based on phase difference detection. When phase difference is within acceptable range, the short-circuit section operates to improve efficiency. When phase difference exceeds threshold, the control mode changes to prioritize waveform accuracy, thereby dynamically balancing efficiency and current quality
Solution Approach 2:
The controller monitors AC voltage and current waveforms to detect phase difference and provides feedback to adjust the switching control. This feedback mechanism ensures that the short-circuit section operates in a manner that maintains both efficiency and AC current waveform accuracy by correcting operation when distortion is detected
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for efficient power conversion without power loss and distortion, even with a phase difference between AC voltage and AC current, by controlling the full-bridge circuit and short-circuit section to maintain appropriate voltage and reduce switching and reactor power losses.
Implementation Method 1
a freewheeling diode provided along with the full-bridge circuit and being for passing a current in a forward direction thereof
Implementation Method 2
a diode configured to block a current from the first line to the second line and existing in series with the sixth switch, and a diode configured to block a current from the second line to the first line and existing in series with the fifth switch
Implementation Method 3
an AC reactor existing between the full-bridge circuit and the AC electrical path
Data Source
AI summary
In a High Efficient and Reliable Inverter Concept power conversion device, control is performed with one cycle divided into four periods, wherein in a first period when the signs of an AC voltage and an AC current are both positive, first and fourth switches perform switching operation, second and third switches are opened, and a sixth switch is closed; in a second period when the signs are positive and negative, a current is passed through freewheeling diodes when a fifth switch is opened while the fifth switch performs switching operation; in a third period when both signs are negative, the second and third switches perform switching operation, the first and fourth switches are opened, and the fifth switch is closed; and in a fourth period when the signs are negative and positive, a current is passed through freewheeling diodes when the sixth switch is opened while the sixth switch performs switching operation.