Inverter Pulse Mode Control for Efficiency and Harmonic Reduction
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Solution Overview
Problem
Inverters used for converting DC power from alternative energy sources like photovoltaic cells face efficiency challenges, particularly at lower output power levels, and existing methods like burst mode can cause harmonic distortion and are restricted to light loads.
Innovation Solution
The method involves determining an output frequency and pulse width value for the inverter's output waveform, which is less than a half-wave period, and adjusting it based on output power, allowing the inverter to operate in pulse mode to conserve energy and reduce harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If burst mode technique is implemented to improve efficiency at light loads, then efficiency is improved, but harmonic distortion increases and regulatory compliance deteriorates
Solution Approach 1:
The patent implements periodic pulsed output cycles instead of continuous operation, where the inverter operates in discrete on/off cycles. This periodic action allows the system to achieve light-load efficiency by concentrating power delivery into specific time windows while maintaining regulatory compliance through controlled pulse characteristics that minimize harmonic distortion.
Solution Approach 2:
The patent dynamically adjusts the pulse width modulation (PWM) duty cycle and pulse frequency based on real-time load conditions and grid requirements. This dynamic control enables the inverter to optimize efficiency at light loads while automatically adapting to maintain harmonic distortion within regulatory limits, resolving the contradiction between efficiency improvement and harmonic control.
2Loss of energy
If burst mode is used to concentrate power output, then efficiency improves, but output waveform quality deteriorates due to subharmonics
Solution Approach 1:
The patent incorporates feedback control mechanisms that continuously monitor the output waveform quality and adjust the pulse generation parameters accordingly. This feedback loop detects waveform distortions and subharmonics in real-time, automatically modifying the PWM duty cycle and pulse timing to maintain high-quality output waveforms while preserving the efficiency benefits of pulsed operation.
Solution Approach 2:
The patent changes key operational parameters such as pulse width, pulse frequency, and duty cycle based on operating conditions. By dynamically adjusting these parameters, the system maintains efficient pulsed operation at light loads while ensuring output waveform quality remains within acceptable standards, preventing the generation of harmful subharmonics.
3Loss of energy
If pulse mode control is implemented to improve light-load efficiency, then energy loss is reduced, but device complexity increases
Solution Approach 1:
The patent implements a universal control architecture that handles both full-load continuous operation and light-load pulsed operation through a single integrated controller. This multi-functional approach eliminates the need for separate control circuits for different operating modes, reducing overall device complexity while maintaining the efficiency benefits of pulse mode control at light loads.
Solution Approach 2:
The patent merges the pulse generation, PWM control, and output regulation functions into a unified control mechanism. By combining these functions that could otherwise require separate circuitry, the system achieves light-load efficiency through pulse mode control while minimizing the increase in device complexity through functional integration.
Data Source
AI summary
A method and apparatus for controlling an inverter includes operating the inverter in a one of a normal run mode or a pulse mode depending on one or more criteria. When operating in the pulse mode, the inverter generates a sinusoidal output pulse waveform including a plurality of pulses having a determined pulse width. The pulse width is less than a half-wave period of a full-cycle sinusoidal waveform and may be determined as function of, for example, the output power of the inverter, a grid voltage, and/or other criteria.