Parallel Inverter Control for High-Power Converter Harmonic Reduction
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Solution Overview
Problem
Current high-power electronic power converters for transmission and distribution lines face challenges in achieving high voltage with optimal waveform quality while being cost and size efficient, often requiring complex configurations and multiple magnetic components.
Innovation Solution
The method involves converting DC voltage into alternating voltage using multiple inverters with phase-shifted output waveforms, combined in parallel to achieve high-power output with reduced magnetic components and harmonic content, using interphase transformers and zero-sequence blocking transformers to eliminate common-mode voltages and enhance power quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple inverters are connected in parallel with intermediate magnetic elements or transformers to increase output voltage and power, then the converter power and output voltage are improved, but the device complexity and number of magnetic components increase
Solution Approach 1:
The converter is divided into multiple independent inverter modules (first inverter, second inverter, third inverter, fourth inverter) that can be connected in parallel. Each inverter processes a portion of the power conversion independently, allowing the system to achieve high power output while maintaining modular simplicity and reducing the need for complex intermediate magnetic coupling elements.
2Manufacturing precision
If the number of inverter levels is increased to improve output voltage quality and reduce harmonics, then the waveform quality is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
Multiple three-level inverter modules are combined in parallel to achieve the benefits of higher voltage quality and reduced harmonics. By merging the outputs of multiple simpler three-level inverters rather than using a single complex multi-level inverter, the system achieves superior waveform quality while avoiding the exponential complexity increase that would result from implementing a single high-level multi-level inverter topology.
3Power
If conventional solutions use intermediate magnetic elements or transformers to combine inverters, then the output voltage and power are increased, but the converter size and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for intermediate magnetic coupling elements and transformers that are traditionally required to combine parallel inverters. By directly paralleling the inverter modules through intelligent control and circuit configuration, the system achieves high power output without the bulky magnetic components, significantly reducing converter volume and associated costs.
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
This approach results in a more economical and compact converter with improved waveform quality and power efficiency, reducing the need for additional magnetic components and high-voltage switchgear, while allowing for increased output power and reduced harmonic distortion.
Implementation Method 1
Inverters in electronic power converters comprise static semiconductor-type switches. The switching characteristics of the semiconductor devices currently available on the market enable the most suitable semiconductor for each type of application to be chosen.
Implementation Method 2
The most commonly used solution in the manufacture of high-power converters for FACTS applications, for example, is the connection of three-phase inverters of two or three levels to each other by means of intermediate magnetic elements or transformers
Implementation Method 3
the zero sequence currents induced in the secondary are blocked
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5
AI summary
Control method for converting power in which a DC voltage is converted into alternating voltage, a first alternating voltage (AC1) and a second alternating voltage (AC2) being obtained by means of a first inverter (1) and a second inverter (2) respectively. Said alternating voltages (AC1, AC2) are combined in parallel, a resulting alternating voltage (AC12) being obtained. An additional resulting alternating voltage (AC34) is also generated, converting the DC voltage into alternating voltage, an additional alternating voltage (AC3) and another additional alternating voltage (AC4) being obtained by means of a first additional inverter (3) and a second additional inverter (4) respectively, and combining in parallel said additional alternating voltages (AC3, AC4). The additional resulting alternating voltage (AC34) is displaced in phase approximately 180° in relation to the resulting alternating voltage (AC12). Thanks to said method the common-mode voltages are also eliminated from at least one of the alternating voltages.