Multilevel AC/DC Power Converter Segmentation Strategy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional AC/DC power converters suffer from harmonic distortion, low power factor, and high switching power loss due to high-frequency PWM, which complicates the circuit and increases manufacturing costs.
Innovation Solution
A multilevel AC/DC power converter device is formed by serially connecting a high-frequency power converter and a low-frequency power converter, with the low-frequency converter operating at the same frequency as the AC power source and the high-frequency converter using high-frequency PWM to generate a multilevel AC voltage, reducing switching losses and simplifying the circuit by eliminating the need for additional power conversion circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-frequency PWM is used to control power electronic switches, then input current approaches sinusoidal waveform and power factor approaches unity, but switching power loss increases due to higher voltage change in each switching operation
Solution Approach 1:
The patent divides the single high-frequency switching operation into multiple lower-voltage switching stages using a cascade bridge structure. Each H-bridge module operates at a reduced voltage level, segmenting the total voltage change into smaller increments. This segmentation reduces the voltage change per switching operation, thereby reducing switching power loss while maintaining the ability to control input current waveform and power factor through coordinated control of multiple modules.
Solution Approach 2:
The patent changes the switching frequency parameter differently across multiple H-bridge modules. Some modules operate at high frequency for precise waveform control, while others operate at lower frequencies to reduce switching losses. This differential parameter change allows the system to achieve both sinusoidal input current and reduced overall switching power loss by optimizing the frequency parameter for each module's specific function.
2Device complexity
If conventional cascade bridge-type AC/DC power converter device is used, then the least number of power electronic switches is required, but each power converter must be controlled by high-frequency PWM which results in complication of the driving circuit and higher degree of switching power loss
Solution Approach 1:
The patent segments the cascade bridge structure into multiple independent H-bridge modules, each with its own control strategy. This segmentation allows different modules to operate at different switching frequencies, with some modules using high-frequency PWM for waveform control and others using lower-frequency switching to reduce power loss. The segmentation enables optimized control for each module while maintaining the overall efficiency of the cascade structure.
Solution Approach 2:
The patent applies different control qualities to different parts of the cascade bridge system. Certain H-bridge modules near the AC input side use high-frequency PWM control to shape the input current waveform, while modules closer to the DC output side use lower-frequency control with reduced voltage transitions. This local quality differentiation optimizes the trade-off between waveform control and switching loss reduction in different regions of the converter.
3Device complexity
If conventional cascade bridge-type AC/DC power converter device is used, then each power converter must output a DC power, but several separate DC outputs are formed with no common connection point which requires additional power conversion circuit to integrate all separate DC outputs
Solution Approach 1:
The patent merges all DC output terminals of the cascade bridge modules into a single common DC output terminal. All H-bridge modules share a common DC bus and a single DC output, eliminating the need for separate power conversion circuits to integrate multiple DC outputs. This merging approach simplifies the overall power circuit structure and reduces additional switching operations that would be required for integration, thereby reducing overall switching power loss.
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
This configuration increases power conversion efficiency, reduces electromagnetic interference, and lowers manufacturing costs by simplifying the structure and eliminating the need for additional power conversion circuits.
Implementation Method 1
The power electronic switches of the high-frequency power converter are controlled by high-frequency PWM (Pulse Width Modulation) to adjust an input current approaching to a sinusoidal waveform
Implementation Method 2
The voltage change in each switching operation of the power electronic switch of the multilevel AC/DC converter device is reduced and generates a multilevel AC voltage at an input terminal
Data Source
AI summary
A multilevel AC/DC power converter device includes a high-frequency power converter including a first AC port and a low-frequency power converter including a second AC port and a DC port. A power converting method includes: serially connecting the first AC port of the high-frequency power converter and the second AC port of the low-frequency power converter; operating frequency of the low-frequency power converter synchronized with frequency of an AC power source and operating the high-frequency power converter with high-frequency PWM to generate a multilevel AC voltage; and controlling the multilevel AC voltage to obtain a current of an input AC port being sinusoidal and in a same phase with a voltage of the AC power source. Accordingly, the input power factor approaches unity and the low-frequency power converter supplies a DC voltage to a load via a DC output port.