Converter Harmonic Suppression via Reactor Segmentation
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Solution Overview
Problem
Existing three-phase AC to DC converters face challenges in reducing higher harmonics without using large AC reactors or fast diodes, leading to increased costs and inefficiencies, especially in applications like air conditioners and motor chargers.
Innovation Solution
A converter design incorporating a three-phase diode bridge, smoothing capacitors, flywheel diodes, a reactor, and both-way energizing switches, controlled by a controller that adjusts switch operations based on detected voltage signals and load information, using general-purpose diodes and a smaller reactor to suppress harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a large AC reactor is used to clear higher harmonics regulations, then higher harmonics are reduced, but the size of apparatus increases and cost increases
Solution Approach 1:
The patent segments the single large AC reactor into multiple smaller reactors (first AC reactor and second AC reactor) that are connected in parallel. This segmentation allows the system to achieve the required harmonic filtering effect while reducing the overall size and cost of the apparatus, as multiple small reactors occupy less space and cost less than one large reactor.
Solution Approach 2:
The patent integrates the AC reactors directly into the bridge arm structure of the inverter, nesting the reactor components within the existing circuit topology. This nesting eliminates the need for separate large reactor assemblies, thereby reducing apparatus size while maintaining harmonic suppression performance.
2Object-generated harmful factors
If a large AC reactor is used to clear higher harmonics regulations, then higher harmonics are reduced, but heat loss increases and efficiency decreases
Solution Approach 1:
By dividing the reactor function into multiple parallel reactors, each reactor carries a portion of the current rather than one large reactor carrying all current. This current distribution reduces the I²R losses in each individual reactor, thereby reducing total heat loss and improving system efficiency while maintaining harmonic suppression.
3Object-generated harmful factors
If a three-phase PWM converter with 6 semiconductor power devices is used, then higher harmonics in input current are reduced and output DC voltage is stabilized, but costs of apparatus increase greatly
Solution Approach 1:
The patent merges the functions of the AC reactor and the bridge arm into a single integrated structure. The AC reactors are incorporated as part of the bridge arm circuitry, eliminating the need for separate reactor components and reducing overall apparatus cost while maintaining harmonic suppression capability.
Solution Approach 2:
The bridge arm structure is designed to serve multiple functions simultaneously: it acts as the power switching element, the current limiting element (through integrated AC reactors), and the harmonic suppression element. This multi-functionality reduces the total component count and apparatus cost compared to traditional PWM converters that require separate dedicated components for each function.
4Volume of stationary object
If the number of on/off operations of both-way energizing switches is increased to reduce AC reactor size, then reactor size is reduced, but cost increases due to need for fast recovery diodes
Solution Approach 1:
The patent merges the AC reactor function with the bridge arm structure, eliminating the need for separate large AC reactors. This integration allows the use of standard recovery diodes instead of expensive fast recovery diodes, reducing cost while maintaining compact reactor size through the parallel configuration.
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 solution effectively reduces higher harmonics without large AC reactors or fast diodes, lowering costs and improving efficiency, while conforming to harmonic regulations and reducing heat loss and semiconductor stress.
Implementation Method 1
a reactor arranged between the midpoint of the two flywheel diodes and the midpoint of the smoothing capacitors
Implementation Method 2
a plurality of smoothing capacitors connected in series between the DC output side of the three-phase diode bridge and a DC load
Implementation Method 3
a three-phase diode bridge
Data Source
AI summary
A converter includes three AC reactors, a three-phase diode bridge, a plurality of smoothing capacitors connected in series between a DC output side of the three-phase diode bridge and a DC load, two flywheel diodes connected to positive and negative terminals on the DC side of the three-phase diode bridge, respectively. A reactor is inserted between the midpoint of the two flywheel diodes and the midpoint of the smoothing capacitors, three both-way energizing switches are arranged between the AC side of the three-phase diode bridge and the midpoint of the two flywheel diodes. The three both-way energizing switches are controlled to reduce higher harmonic components of power source current, and by the reactor interposed between the midpoint of the two flywheel diodes and the midpoint of the smoothing capacitors, reverse recovery currents of the three-phase diode bridge during turn-on of the three both-way energizing switches are suppressed.