Harmonic-Free Power Injection Controller for Distributed Generation
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Solution Overview
Problem
Current systems for interfacing distributed power generation, such as wind turbines and photovoltaic cells, with power distribution grids face challenges in achieving efficient and harmonic-free power injection due to complex hardware and control systems, which increase costs and reduce efficiency.
Innovation Solution
A controller system that includes a maximum power point tracker, current reference generator, and current controller with nonlinear elements and enhanced phase locked loop (EPLL) to generate harmonic-free power injection, using a micro-inverter system with an LCL filter to reduce circuit component size and enhance power quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If complex hardware and control systems are used for power injection, then power quality can be improved, but system cost and complexity increase
Solution Approach 1:
The patent changes the control parameter from traditional voltage-based control to instantaneous power-based control. The instantaneous power reference signal is generated by multiplying grid voltage and current, and the nonlinear circuit elements process this power signal directly to generate harmonic-free current references, eliminating the need for complex filtering and coordination between multiple control loops.
Solution Approach 2:
The patent extracts the harmonic generation mechanism by using nonlinear circuit elements that directly process the instantaneous power signal. Instead of trying to filter harmonics out after generation, the system extracts only the fundamental power component through nonlinear processing, inherently preventing harmonic generation at the source.
2Object-generated harmful factors
If traditional control systems are used, then system simplicity can be maintained, but harmonic rejection capability is insufficient
Solution Approach 1:
The patent replaces traditional mechanical/filter-based harmonic rejection methods with electronic nonlinear processing. Instead of using large inductors and capacitors for filtering, the system uses nonlinear circuit elements that electronically process the instantaneous power signal to eliminate harmonics, achieving the same effect with much smaller components.
3Object-generated harmful factors
If larger circuit components are used, then power quality can be improved, but system size and cost increase
Solution Approach 1:
The patent changes the control approach to instantaneous power processing, which allows the use of smaller nonlinear circuit elements instead of large traditional filter components. The instantaneous power signal contains all necessary information about harmonics, and nonlinear processing of this signal achieves harmonic rejection without requiring large physical components.
Data Source
AI summary
Described herein are methods, systems, and apparatus for a controller for a power circuit that interfaces distributed power generation with a power distribution grid, comprising: a first portion, including a maximum power point tracker, that receives signals corresponding to the distributed power generation voltage and current, and outputs to the power circuit a signal for controlling the voltage of the distributed power generation; a second portion, including a current reference generator, a current controller, and a dc voltage controller, that receives signals corresponding to a dc voltage of the power circuit, the power distribution grid voltage and current, and the inverter current, and outputs signals for controlling the power circuit output voltage; wherein the current reference generator includes nonlinear circuit elements and generates a current reference signal from the dc voltage of the power circuit and the grid voltage and current; such that substantially harmonic-free power is injected into the power distribution grid. The distributed power generation may be, for example, a photovoltaic module or a wind turbine.