Three-Phase Three-Winding Transformer Power Conversion Device
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Solution Overview
Problem
Conventional power conversion devices require large and expensive filters and reactors to suppress harmonic currents and short-circuit currents, leading to increased size and cost, which counteracts the benefits of eliminating harmonic filters and transformers.
Innovation Solution
A power conversion device utilizing a three-phase and three-winding transformer with delta-connected secondary and tertiary windings, along with unit modules and capacitors, to suppress harmonic currents and short-circuit currents without the need for large-size reactors, achieving sinusoidal waveforms and constant capacitor voltage control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a filter including reactor and capacitor is inserted to suppress harmonic components, then harmonic suppression performance is improved, but device cost and weight increase
Solution Approach 1:
The invention extracts and eliminates the filter components (reactor and capacitor) from the system by using a three-phase and three-winding transformer with delta-connected secondary and tertiary windings. The transformer structure itself provides the necessary harmonic suppression functionality, making separate filter components unnecessary.
Solution Approach 2:
The three-phase and three-winding transformer performs multiple functions: power conversion, voltage transformation, and harmonic suppression. The delta-connected windings provide a circulation path for harmonic currents, enabling the transformer to suppress harmonics while performing its primary power conversion function, eliminating the need for separate filter components.
2Object-affected harmful factors
If a filter including reactor and capacitor is inserted to suppress harmonic components, then harmonic suppression performance is improved, but device cost increases
Solution Approach 1:
The invention extracts and eliminates the filter components (reactor and capacitor) from the system by using a three-phase and three-winding transformer with delta-connected secondary and tertiary windings. The transformer structure itself provides the necessary harmonic suppression functionality, making separate filter components unnecessary.
Solution Approach 2:
The three-phase and three-winding transformer performs multiple functions: power conversion, voltage transformation, and harmonic suppression. The delta-connected windings provide a circulation path for harmonic currents, enabling the transformer to suppress harmonics while performing its primary power conversion function, eliminating the need for separate filter components.
3Object-affected harmful factors
If large-size reactor is used to restrict short-circuit current, then short-circuit current suppression is improved, but device size and cost increase
Solution Approach 1:
The invention extracts and eliminates the need for large-size buffer reactors by utilizing the inherent impedance characteristics of the three-phase and three-winding transformer. The transformer's winding structure and magnetic circuit provide natural current limiting without requiring additional large-volume reactor components.
Solution Approach 2:
The three-phase and three-winding transformer performs multiple functions including power conversion, voltage transformation, and short-circuit current limitation. The transformer's design inherently provides impedance that limits short-circuit currents, eliminating the need for separate buffer reactor components.
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 enables low-harmonic voltage and current waveforms without harmonic filters and large reactors, reducing device size and cost while maintaining high reliability and sinusoidal system voltage.
Implementation Method 1
A power conversion device utilizing a three-phase and three-winding transformer with delta-connected secondary and tertiary windings, along with unit modules and capacitors, to suppress harmonic currents and short-circuit currents
Implementation Method 2
A power conversion device utilizing a three-phase and three-winding transformer with delta-connected secondary and tertiary windings, along with unit modules and capacitors, to suppress harmonic currents and short-circuit currents
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
An inexpensive, compact, and highly reliable power conversion device that eliminates a harmonic current which is to be output accidentally and which strains a power system is provided. A three-phase and three-winding transformer A has a neutral point of a secondary winding in each phase connected to that of a tertiary winding in the same phase. A leg including two self-extinguishing switching elements connected in series is connected in parallel with a capacitor to form a unit module C, and positive-side unit arms Up, Vp, and Wp, and negative-side unit arms Un, Vn, and Wn each have the two unit modules C connected in series. The positive-side unit arm has one end connected to the positive side of the DC power supply B, and the other end connected to the output terminal of the secondary winding of the three-phase and three-winding transformer A in each phase. The negative-side unit arm has one end connected to the negative side of the DC power supply B, and has the other end connected to the output terminal of the tertiary winding of the three-phase and three-winding transformer A in each phase.