Three-Phase Inverter Control With VSG Harmonic Compensation
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Solution Overview
Problem
Grid-connected inverters with virtual synchronous generator capabilities lack effective suppression measures for harmonic components in output currents and voltages, particularly under asymmetric and non-linear loads, leading to deviations in amplitude and frequency of output voltage.
Innovation Solution
A control method and device for a three-phase AC system that includes an inverter and a filter unit, where the system receives output signals, extracts harmonic components, and generates error signals to obtain harmonic compensation electric potentials, which are superimposed with fundamental electric potentials to control the inverter switching signals, effectively suppressing harmonics in both grid-connected and off-grid operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual synchronous generator control is implemented to simulate inertia and damping characteristics, then grid stability is improved, but harmonic components in output current and voltage are not suppressed
Solution Approach 1:
The patent combines virtual synchronous generator control with harmonic suppression control into a unified control system. The VSG control module simulates inertia and damping characteristics for grid stability, while the harmonic suppression module extracts and eliminates harmonic components from output current and voltage, allowing both functions to operate simultaneously without conflict.
Solution Approach 2:
The control device is designed to perform multiple functions: it provides virtual synchronous generator capabilities for grid stability support while simultaneously suppressing harmonic components in both grid-connected and off-grid operations. This multi-functional approach eliminates the need for separate control systems.
2Manufacturing precision
If harmonic control is added to suppress harmonic components, then output current and voltage quality is improved, but control system complexity increases
Solution Approach 1:
The control system is divided into distinct functional modules: a VSG control module for simulating synchronous generator characteristics, a harmonic extraction module for identifying harmonic components, and a harmonic suppression module for eliminating harmonics. This modular segmentation makes the complex control system more manageable and implementable.
Solution Approach 2:
The patent introduces an intermediary processing stage that extracts harmonic components from the output signals before applying suppression control. This intermediary step separates the harmonic analysis function from the main control loop, simplifying the overall control architecture while maintaining effective harmonic suppression.
3Adaptability or versatility
If the inverter operates in off-grid mode with asymmetric and non-linear loads, then adaptability is improved, but output voltage amplitude and frequency deviate from rated values due to harmonics
Solution Approach 1:
The control system dynamically adapts to different operating modes (grid-connected and off-grid) and load conditions (asymmetric and non-linear loads). The harmonic suppression control continuously adjusts based on real-time extraction of harmonic components, maintaining output voltage quality despite varying operational conditions.
Data Source
AI summary
The present disclosure provides a three-phase AC system and a control method thereof. The method includes: receiving an output signal of the three-phase AC system and obtaining a characteristic value of the output signal according to the output signal; performing virtual synchronous generator control on the inverter to obtain a fundamental electric potential; extracting a harmonic component from the output signal and obtaining an error signal according to the harmonic component and a reference value of the harmonic component; controlling the error signal to obtain a harmonic compensation electric potential; obtaining a control electric potential by superimposing the harmonic compensation electric potential with the fundamental electric potential; obtaining a pulse signal by modulating the control electric potential, and obtaining a switching signal of the inverter according to the pulse signal.