UPS Inverter Harmonic Control With Repetitive Current Compensation
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Solution Overview
Problem
Existing uninterruptible power supplies (UPS) suffer from waveform distortion and system instability due to non-linear load factors, with control methods having low response speed, poor stability, and a narrow adaptation range.
Innovation Solution
A harmonic reduce control system for inverters, incorporating a phase-locked loop controller, voltage sum loop controller, repetitive controller, and current loop controller, to generate an inverter current reference value and control transistors to limit harmonics, using decoupled dual synchronous reference frame phase-locked loop and feed-forward transfer functions for improved stability and adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional control method is used for waveform distortion, then the system structure is simple, but the response speed is low and stability is poor
Solution Approach 1:
The control system is segmented into multiple specialized controllers: a phase-locked loop controller for frequency tracking, a voltage sum loop controller for voltage regulation, a repetitive controller for harmonic compensation, and a current loop controller for current control. Each controller handles a specific aspect of the waveform distortion problem, enabling high response speed and stability while maintaining manageable complexity through functional decomposition.
2Adaptability or versatility
If a conventional control method is used for waveform distortion, then the device complexity is low, but the adaptation range is narrow
Solution Approach 1:
The control system is designed with multi-functional controllers that can handle various types of waveform distortions and operating conditions. The phase-locked loop controller adapts to different frequency variations, the voltage sum loop controller handles different voltage levels, and the repetitive controller compensates for various harmonic components. This universal design enables wide adaptation range while the modular structure keeps complexity manageable.
3Loss of energy
If the inverter operates in bypass mode to reduce losses, then energy efficiency is improved, but harmonic pollution increases on the power grid
Solution Approach 1:
The inverter acts as an intermediary between the power grid and the load in bypass mode. Instead of directly connecting the load to the grid, the inverter is inserted as a mediating device that actively compensates for harmonic currents. The control system generates compensation currents that cancel out the harmonics generated by non-linear loads, allowing the system to operate in efficient bypass mode while maintaining power quality through the inverter's harmonic mitigation function.
Data Source
AI summary
The present invention provides a harmonic reduce control system for controlling an inverter, including a phase-locked loop controller, a voltage sum loop controller, a repetitive controller, a current loop controller, and a harmonic obtaining module. The harmonic obtaining module detects a harmonic value of a load current. The control system generates an inverter current reference value based on a first current value output by the voltage sum loop controller and the harmonic value, calculates a real-time frequency value based on a voltage of the power grid, obtains, through calculation, a repetitive controller output value based on the inverter current reference value, the inverter output current, and the real-time frequency value, and outputs a first duty cycle based on the repetitive controller output value. The control system limits the inverter output current based on the first duty cycle.