Three-Phase Inverter Control via Rotating Reference Frame Synchronization
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Solution Overview
Problem
Conventional Phase Locked Loop (PLL) algorithms are inefficient for synchronizing the output current of three-phase inverters with grid voltage, particularly when dealing with renewable energy sources like fuel cells and photovoltaic solar panels, which have non-constant characteristics.
Innovation Solution
A method involving the transformation of three-phase voltages and currents into rotating reference systems to determine error signals, allowing for precise control of the inverter to synchronize with grid voltage, using Clarke transformations and scalar products to generate PWM signals for phase synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Phase Locked Loop (PLL) algorithms are used to synchronize inverter output current with grid voltage, then synchronization is achieved, but the efficiency and reliability are insufficient when dealing with non-constant characteristics from renewable energy sources
Solution Approach 1:
The patent transforms the synchronization approach by changing the reference frame parameters from stationary to rotating. By using a rotating reference frame synchronized with grid voltage, the method adapts to non-constant characteristics of renewable energy sources while maintaining reliable synchronization. The transformation of current and voltage phasors into the rotating reference frame allows dynamic adaptation to varying conditions.
2Productivity
If conventional PLL algorithms are used for synchronization, then the control system is relatively simple, but the efficiency and precision of power transfer are insufficient
Solution Approach 1:
The patent replaces conventional PLL algorithms with a rotating reference frame transformation method. This substitution involves transforming three-phase voltages and currents into a rotating reference frame using Clarke and Park transformations, then comparing phasor components to generate error signals for PWM control. This approach improves power transfer efficiency while maintaining manageable control system complexity through systematic mathematical transformations.
3Measurement precision
If the inverter directly transfers power from renewable sources with non-constant characteristics to the grid, then the system is simple, but the grid voltage synchronization is imprecise
Solution Approach 1:
The patent introduces a rotating reference frame dimension to achieve precise synchronization. By transforming the control problem from the stationary three-phase domain to a rotating two-axis (d-q) reference frame, the method enables precise comparison of voltage and current phasors. This dimensional transformation allows accurate synchronization while managing control complexity through structured transformation algorithms.
Data Source
AI summary
A method of controlling an inverter to includes determining the components of a phasor representing the output current from the inverter in a fixed reference system; determining the components of the current phasor in a reference system rotating at a velocity equal to the velocity of rotation of the phasor representing the grid voltage; and comparing the components of the current phasor in the rotating reference system with a reference, again expressed in the rotating reference system, to determine an error signal, by means of which the inverter is controlled.