Power Conditioner Switch Control for Waveform Distortion
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Solution Overview
Problem
Conventional power conditioners for photovoltaic systems experience high switching losses and waveform distortion during DC to AC power conversion, leading to low power conversion efficiency and sinusoidal voltage distortion.
Innovation Solution
A power conditioner with multiple switch circuits and a control system that alternately turns on and off switch elements at different frequencies, using deadtime control to adjust the on/off duty of switch elements and generate sinusoidal voltage by combining pulse voltage series and difference voltages, thereby suppressing waveform distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-frequency PWM switching is used to convert DC power to AC power, then power conversion speed is improved, but switching losses increase and power conversion efficiency decreases
Solution Approach 1:
The patent divides the power conversion process into two separate stages: a chopper circuit that operates at low frequency to perform coarse power conversion, and a PWM inverter that operates at high frequency for fine power conversion. This segmentation allows each circuit to operate at its optimal frequency, reducing overall switching losses while maintaining fast response capability.
2Productivity
If high-frequency PWM switching is used for power conversion, then power conversion efficiency is improved, but waveform distortion increases
Solution Approach 1:
The patent segments the power conversion function into a chopper circuit for coarse conversion and a PWM inverter for fine conversion. The chopper circuit handles the bulk power conversion at low frequency with minimal distortion, while the PWM inverter refines the waveform at high frequency, achieving both high efficiency and low distortion.
Solution Approach 2:
The chopper circuit acts as an intermediary between the DC power source and the PWM inverter. It pre-processes the power at low frequency, providing a stable intermediate output that reduces the burden on the PWM inverter, thereby minimizing waveform distortion while maintaining high conversion efficiency.
3Reliability
If deadtime is provided in switch element control, then reliability is improved, but waveform distortion increases due to effective on drive during deadtime
Solution Approach 1:
The control circuit monitors the effective on drive during deadtime periods and provides feedback to adjust the switching signals. When a diode conducts during deadtime, the control circuit detects this condition and modifies subsequent switching commands to compensate for the distortion, maintaining both reliability and waveform quality.
Solution Approach 2:
The patent dynamically changes switching parameters based on operating conditions. During deadtime periods when diode conduction occurs, the control circuit adjusts duty cycles and timing parameters to compensate for the effective on drive, thereby minimizing waveform distortion while preserving the protective deadtime functionality.
Data Source
AI summary
A power conditioner that suppresses distortion in a waveform of a sinusoidal generated voltage includes a first and second group including two switches each connected in inverse parallel and in series. The power conditioner alternately turns on and off both switches in the first group at a prescribed chopping frequency and alternately turns on and off both switches in the second group at a PWM frequency higher than the chopping frequency. If control is performed with a dead-time provided in the on/off timing for both switches in each group, the power conditioner adjusts and controls the on/off duty for the second group switches to correspond to the effective on drive in one switch by each diode during the dead-time for each switch in the first group.