Active Harmonic Reduction in Inverter Output Current
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Solution Overview
Problem
Power conversion modules, such as solar inverter systems, generate undesirable harmonics in output current, which are costly and bulky to filter using traditional passive filtering methods, necessitating a more efficient harmonic reduction technique.
Innovation Solution
Active harmonic reduction techniques are employed by pre-distorting the commanded inverter output current waveform with predetermined harmonic components, using predictive methods and control modules to inject compensation currents, reducing harmonics to levels compliant with regulatory standards without requiring feedback from inverter output current or voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If passive filtering is used to reduce inverter output current harmonic distortion, then harmonic reduction is achieved, but the filter components become bulky and expensive, increasing inverter size and cost
Solution Approach 1:
The patent replaces the mechanical/passive filtering system with an active control system using power electronics. Instead of using bulky passive filter components (inductors, capacitors, resistors), the invention uses active power conversion stages and control algorithms to synthesize clean output current, substituting mechanical filtering with electronic control
Solution Approach 2:
The invention changes the operating parameters of the power conversion system by using variable switching frequencies and pulse width modulation (PWM) techniques. By dynamically adjusting switching parameters and modulation indices, the system can control harmonic content without requiring physical filter components, thus reducing inverter size while maintaining harmonic compliance
2Object-affected harmful factors
If passive filtering is used to reduce inverter output current harmonic distortion, then harmonic reduction is achieved, but the filter components become expensive, increasing inverter cost
Solution Approach 1:
The patent replaces expensive passive filter components with cost-effective power electronic switches and control circuitry. The active power conversion approach uses semiconductor devices (IGBTs, MOSFETs) and simple RC filters instead of large, expensive passive filters, significantly reducing material costs and manufacturing complexity
Solution Approach 2:
The invention uses inexpensive RC filter components and standard power electronic devices rather than expensive passive filter components. The control system uses software-based harmonic compensation algorithms that are cost-effective to implement, reducing overall inverter cost while achieving the required harmonic performance
Data Source
AI summary
Method and apparatus for reducing harmonic distortion. In one embodiment, the method comprises determining an inverter output current waveform; determining a plurality of harmonic components of the inverter output current waveform; determining, based on the plurality of harmonic components, a plurality of harmonic compensation components; and generating a compensating current comprising the plurality of harmonic compensation components.