Single-Phase Multiplex Converter Harmonic Suppression
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Solution Overview
Problem
Conventional active filters require large-scale filter circuits to suppress harmonic currents, making it difficult to manufacture a compact active filter system.
Innovation Solution
A power converting device with a single-phase multiplex converter, composed of series-connected single-phase inverters, which uses gradational output voltage control to generate harmonic compensation currents, reducing the need for a large-scale filter circuit and enabling high-speed, high-precision current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional active filter employs a high-frequency PWM inverter, then the active filter can generate harmonic compensation current, but a large-scale filter circuit is required, making it difficult to manufacture a compact system
Solution Approach 1:
The patent divides the single-phase inverter into multiple half-bridge circuits connected in series. Each half-bridge circuit includes switching elements and capacitors that work independently but contribute to the overall output voltage. This segmentation allows the inverter to generate multiple voltage levels (positive, negative, and zero) without requiring a large-scale filter circuit, thereby resolving the contradiction between harmonic compensation capability and filter circuit size.
Solution Approach 2:
The patent employs pulse width modulation (PWM) control to dynamically adjust the switching states of the half-bridge circuits. By dynamically changing the duty ratios of the switching elements, the inverter can generate a quasi-sinusoidal output voltage with reduced harmonic content. This dynamic control eliminates the need for large passive filter circuits while maintaining reliable harmonic compensation capability.
2Object-generated harmful factors
If a large-scale filter circuit is used to suppress harmonic currents, then harmonic suppression is effective, but the device becomes complex and difficult to manufacture in a compact structure
Solution Approach 1:
The patent replaces the traditional mechanical/passive filter circuit approach with an active electronic control system. Instead of using large inductors and capacitors to passively filter harmonics, the system uses PWM-controlled switching elements to actively generate compensation currents that cancel harmonics. This substitution dramatically reduces device complexity and enables compact manufacturing while maintaining effective harmonic suppression.
Solution Approach 2:
The patent changes the operating parameters of the inverter by controlling the switching frequency and duty ratios of the half-bridge circuits. By adjusting these parameters dynamically, the system can adapt to different load conditions and maintain optimal harmonic suppression performance without requiring complex fixed-parameter filter circuits. This parameter flexibility simplifies the overall device design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for a compact and simple design while maintaining high-speed, high-precision output current control, effectively suppressing harmonic currents without the need for a large-scale filter circuit.
Implementation Method 1
a high-frequency pulse width modulation (PWM) inverter which is characterized by low loss
Implementation Method 2
connected to a load via a reactor
Data Source
AI summary
A power converting device includes a single-phase multiplex converter used as an active filter and a control device. The single-phase multiplex converter includes multiple single-phase inverters connected in series at AC output sides. Each of the single-phase inverters converts DC power fed from a DC power supply into AC power. The control device includes hysteresis comparators and controls output voltage of the single-phase multiplex converter by gradational output voltage control, based on the sum of selectively combined output voltages of the multiple single-phase inverters. The control device controls the single-phase multiplex converter so that an output current follows a harmonic compensation reference current, canceling harmonics leaking from a load to which the power converting device is connected.