Series-Connected Power Converter Cell Efficiency Control
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Solution Overview
Problem
Power conversion devices with outputs connected in series are not considered in existing configurations, leading to inefficiencies in light load modes, as stopping a converter results in no output.
Innovation Solution
A power conversion device with a controller that manages a series-connected configuration of power converter cells, where some cells' converters are stopped based on power supply or load power, allowing the inverter to continue operating using a DC link capacitor, thereby maintaining efficiency in light load modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a converter is stopped in a series-connected power conversion device to improve efficiency in light load mode, then efficiency is improved, but output is lost because the series connection requires all converters to operate
Solution Approach 1:
The power conversion device is divided into multiple independent power converter cells, each with its own converter and inverter. The converters are connected in series while inverters are connected in parallel, allowing individual cell isolation. This segmentation enables selective operation of converters without affecting the entire system output.
Solution Approach 2:
A DC link capacitor is introduced as an intermediary energy storage element between the converter and inverter in each cell. This capacitor allows the inverter to continue operating using stored energy when the converter is stopped, decoupling the operation of the converter from the inverter and enabling efficiency improvement without output loss.
2Power
If all converters operate in series connection to maintain output, then output is maintained, but efficiency deteriorates due to fixed losses in light load mode
Solution Approach 1:
The system dynamically adjusts the number of operating converters based on load conditions. In light load modes, fewer converters are operated while maintaining the same output through the parallel inverter configuration and DC link capacitor energy storage, thereby reducing fixed losses dynamically according to actual power requirements.
Solution Approach 2:
The operational parameters of the power conversion device are changed by selectively activating or deactivating specific converter-inverter cells based on load demands. This parameter change allows the system to optimize efficiency by matching the number of active converters to the actual power conversion requirements, reducing unnecessary fixed losses.
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
Improves efficiency in light load modes by strategically stopping converters and maintaining output through DC link capacitors, eliminating fixed losses and optimizing power conversion.
Implementation Method 1
The inverter continues to operate using a DC link capacitor as a power supply
Data Source
AI summary
In a power conversion device in a configuration in which a plurality of power converter cells has serially connected outputs and includes a converter and an inverter as components, when a load is light, the cells also operate with a light load, and efficiency is reduced. A power conversion device has a plurality of power converter cells. The outputs of the cells are connected in series. The device has a controller that controls the cells. The cells each have a converter that converts an externally inputted power supply voltage and generates a DC link voltage and an inverter that converts the DC link voltage into an alternating current voltage and outputs the current. The controller stops a converter in some of the cells depending on power supply electric power or load electric power. The inverter continues to operate using a link capacitor as a power supply.