Three-Level Inverter Dynamic Half-Bridge Mode Switching
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Solution Overview
Problem
Existing single phase three-level inverters operate in full bridge mode regardless of output voltage amplitude, resulting in conduction and switching losses in all switch elements and diodes, which is inefficient.
Innovation Solution
A power conversion device that switches to half bridge mode when the alternating current output voltage amplitude is lower than the direct current power source voltage, using a controller with dual PWM controllers and a gate signal switching unit to generate appropriate gate signals, reducing the number of switching elements and thereby minimizing losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inverter operates in full bridge mode regardless of output voltage amplitude, then the output voltage can be maintained at any level, but conduction and switching losses occur in all switch elements and diodes, reducing efficiency
Solution Approach 1:
The inverter dynamically switches between full bridge mode and half bridge mode based on the amplitude of the fundamental wave of the alternating current output voltage. When the amplitude is lower than the direct current power source voltage, the system transitions to half bridge mode to reduce losses. This dynamic adaptation resolves the contradiction by adjusting the operating mode according to actual output requirements, thereby reducing energy losses while maintaining the ability to provide various output voltage levels.
Solution Approach 2:
The system changes the operating parameter (bridge mode) based on the output voltage amplitude condition. By detecting when the fundamental wave amplitude is lower than the DC power source voltage, the controller changes the switching configuration from full bridge to half bridge, altering the electrical parameters of the circuit to minimize conduction and switching losses in switch elements and diodes.
2Loss of energy
If the inverter operates in full bridge mode, then all switch elements and diodes are utilized, but the number of elements carrying out switching action is excessive, increasing loss
Solution Approach 1:
The invention extracts or removes half of the bridge (either first half bridge or second half bridge) from active switching operation when operating in half bridge mode. By taking out one half-bridge from the switching action, the system reduces the number of switch elements and diodes that need to perform switching operations, thereby reducing switching losses and conduction losses while maintaining the necessary output voltage capability.
3Loss of energy
If the inverter operates in half bridge mode, then losses are reduced by half, but the output voltage amplitude is limited to below the direct current power source voltage
Solution Approach 1:
The system dynamically adjusts the operating mode based on power requirements. When high output voltage amplitude (equal to or greater than DC power source voltage) is needed, full bridge mode is used. When lower output voltage amplitude is sufficient, half bridge mode is activated to reduce losses. This dynamic switching between modes resolves the contradiction by matching the operating mode to the actual power delivery requirements.
Solution Approach 2:
The controller changes the operating parameter (bridge configuration) based on the detected output voltage amplitude. When the fundamental wave amplitude is detected to be lower than the DC power source voltage, the system changes from full bridge configuration to half bridge configuration, adjusting the electrical parameters to optimize efficiency for the current power level.
Data Source
AI summary
A single phase three-level power converter can include a first half bridge and a second half bridge. A half bridge operation is implemented in either the first half bridge or second half bridge when outputting a single phase alternating current voltage having an amplitude a half or less than that of a direct current input voltage, and also, by alternately switching between the bridges carrying out the half bridge operation. In certain configurations, the power converter can convert a direct current input voltage into alternating current phase voltages having three levels of potential, which are positive, negative, and intermediate voltages, by controlling on-off conditions of a plurality of switch elements, and a controller that, by supplying gate signals to the switch elements configuring the first half bridge and second half bridge, controls the related on-off conditions.