Parallel Power Conversion System Zero-Crossover Distortion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
When power conversion devices operating in parallel use the clamping method, zero-crossover distortion increases in the output voltage during the zero-crossover period, affecting load synchronization and efficiency, especially as the number of units increases.
Innovation Solution
Implementing a power conversion system where at least one device operates in a first mode outputting three voltage levels and the remaining devices operate in a second mode outputting two voltage levels, using a bridge circuit and clamping circuit configuration, to inhibit zero-crossover distortion and enhance efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If all power conversion devices operate in clamping mode (first mode) to achieve high efficiency, then power conversion efficiency is improved, but zero-crossover distortion increases and affects load synchronization
Solution Approach 1:
The power conversion system is segmented into two groups: at least one device operates in first mode (clamping method with three voltage levels) while remaining devices operate in second mode (bipolar PWM with two voltage levels). This segmentation allows the system to distribute the distortion burden and maintain synchronization accuracy while preserving high efficiency benefits.
Solution Approach 2:
The operating mode parameter is changed dynamically based on synchronization requirements. By switching between first mode (clamping) and second mode (bipolar PWM), the system can adjust output voltage characteristics to minimize zero-crossover distortion during critical synchronization periods while maintaining high efficiency during other operation phases.
2Device complexity
If all power conversion devices operate in bipolar PWM mode (second mode) to simplify control, then device complexity is reduced, but power conversion efficiency decreases
Solution Approach 1:
The system segments devices into different operational roles: some devices use the simpler second mode (bipolar PWM) while at least one device uses the more efficient but complex first mode (clamping). This allows the system to achieve high overall efficiency without requiring all devices to implement complex control logic.
Solution Approach 2:
The power conversion system is designed with multi-functionality to support both first mode (clamping) and second mode (bipolar PWM) operations. This universal design allows flexible configuration where devices can operate in different modes based on system requirements, combining the simplicity of bipolar PWM with the efficiency of clamping method.
3Productivity
If the number of power conversion devices operating in parallel is increased to meet higher load demands, then productivity is improved, but zero-crossover distortion increases significantly
Solution Approach 1:
When multiple devices operate in parallel, the system segments their operational modes: at least one device operates in first mode (clamping) while others operate in second mode (bipolar PWM). This segmentation strategy allows the system to scale productivity by adding more devices while maintaining output voltage accuracy through the presence of devices operating in distortion-minimizing mode.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A bridge circuit (21) converts input direct-current voltage and outputs alternating-current voltage. A filter circuit (23) attenuates a high-frequency component of the alternating-current voltage output from the bridge circuit (21). A clamping circuit (22) is disposed between the bridge circuit (21) and the filter circuit (23), and is capable of short-circuiting the output side of the bridge circuit (21). A control circuit (24) has a first mode in which a switching element causes the alternating-current voltage to be output to the filter circuit (23) at three or more voltage levels, and a second mode in which the switching element causes the alternating-current voltage to be output to the filter circuit (23) at two voltage levels. When power conversion devices (20) have their alternating-current side output paths connected and operate in parallel, at least one of the power conversion devices (20) operating in parallel operates in the second mode.