Single-Phase Power Filter Using High-Frequency Switched Converters
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Solution Overview
Problem
High-power electric conversion systems face challenges in reducing volume, weight, and material usage, particularly due to bulky electrolytic capacitors required for power factor correction, which also suffer from reliability issues and generate unwanted reactive power and harmonics.
Innovation Solution
A system comprising a single-phase AC input, a first AC/AC switched converter increasing the frequency, a DC electrical energy storage element in series with the output, and a second DC/AC switched converter to filter fluctuating power, reducing the need for large capacitors and minimizing reactive power and harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bulky electrolytic storage capacitor is used for power factor correction in single-phase line, then the fluctuating power can be compensated, but the volume, weight and reliability of the system deteriorate
Solution Approach 1:
The invention changes the operating frequency parameter from grid frequency (50/60Hz) to high frequency (kHz range). This frequency transformation allows the use of much smaller capacitors and inductors while achieving the same power factor correction function, thereby reducing weight and improving reliability without sacrificing performance
Solution Approach 2:
The invention replaces the traditional mechanical/electrical power factor correction approach using large electrolytic capacitors with an active power electronic converter system. This substitution uses controlled switching devices to synthesize the correction current, eliminating the need for bulky passive components and their associated reliability issues
2Volume of moving object
If the frequency of operation is increased to reduce volume of magnetic elements, then the power density increases, but the system complexity and difficulty of control increase
Solution Approach 1:
The invention segments the power conversion function into two independent high-frequency converters: a first converter for power factor correction and a second converter for power transfer. This segmentation allows each converter to operate optimally at high frequency with reduced magnetic component sizes, while the modular structure manages system complexity through functional decomposition
Solution Approach 2:
The first high-frequency converter serves multiple functions simultaneously: it performs power factor correction by injecting compensating current, transfers power to the second converter, and operates at high frequency to minimize magnetic element volumes. This multi-functionality reduces overall system complexity despite the high operating frequency
3Power
If non-resistive loads are connected to the electrical distribution grid, then the power demand is met, but reactive power and current harmonics are generated causing penalties
Solution Approach 1:
The invention implements feedback control in the first high-frequency converter to continuously monitor and compensate for reactive power and harmonics. The converter adjusts its switching pattern based on detected grid conditions to inject compensating current that cancels harmful factors, enabling full power delivery to non-resistive loads without generating penalties
Solution Approach 2:
The invention converts the harmful reactive power and harmonics generated by non-resistive loads into beneficial effects by using the first high-frequency converter to actively inject compensating waveforms. The converter transforms the problem of power factor correction into an opportunity to deliver full power to the load while eliminating harmonics and reactive power penalties through controlled switching
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 configuration reduces the size and weight of capacitors, enhances reliability, and minimizes reactive power and harmonics, achieving efficient power processing and transfer while maintaining constant power delivery.
Implementation Method 1
a DC electrical energy storage element in series with the output of the first switched converter with the interposition of a second DC/AC switched converter
Data Source
Figure 1A~1B
Figure 1C~2
Figure 1D
AI summary
The present invention is embodied as a system for filtering fluctuant power generated in a single-phase line operating as power factor correction when feeding an inductive element, the system comprising a first AC/AC switched converter, preferably for increasing the frequency of the input signal for feeding the inductive element. The system is characterized in that it further comprises a DC electrical energy storage element in series with the output of the first switched converter with the interposition of a second DC/AC switched converter. The second switched converter compensates the fluctuations of the power outputted in the first switched converter causing that the fluctuating power is not transferred to the load. In a preferred embodiment the inductive element is the primary in a transformer wherein the output may be rectified by a third switched AC/DC converter.