AC-DC Converter Reactor Size Reduction via Line-Frequency Switching
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Solution Overview
Problem
Existing AC to DC converter technologies face challenges in suppressing harmonic currents while improving power factor, often resulting in large reactors, high power consumption, and increased costs due to high-frequency PWM control, which complicates circuit configurations and increases costs.
Innovation Solution
An AC to DC converter design that includes a reactor, rectifier, series-connected capacitors, and bi-directional switching means, where the ON/OFF timing of the switching means is controlled based on a virtual AC source's phase angle and amplitude, allowing for sinusoidal converter voltage output and reduced reactor size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If high-frequency PWM control is used to suppress harmonic currents and improve power factor, then harmonic suppression performance is improved, but power consumption increases and circuit complexity increases
Solution Approach 1:
The invention changes the control parameter from high-frequency PWM to low-frequency switching synchronized with the AC power source period. The switching means performs opening and closing operations at least twice in half a cycle of the power source, synchronizing with the power source period, which fundamentally alters the operating frequency parameter from high-frequency PWM to line-frequency synchronized switching.
Solution Approach 2:
The invention replaces the complex high-frequency PWM control mechanism with a simpler control mechanism that synchronizes switching with the AC power source period. This substitution eliminates the need for complex PWM generation and processing while achieving harmonic suppression through synchronized switching at lower frequencies.
2Object-generated harmful factors
If high-frequency PWM control is used to suppress harmonic currents, then power factor is improved, but power consumption increases
Solution Approach 1:
The invention changes the switching frequency parameter from high-frequency PWM to low-frequency switching synchronized with the AC power source period. By performing switching operations at least twice in half a cycle of the power source, the system operates at line-frequency synchronized rates rather than high-frequency PWM rates, significantly reducing power consumption while maintaining harmonic suppression effectiveness.
3Ease of manufacture
If reactor size is reduced to lower cost, then manufacturing cost is reduced, but harmonic suppression performance deteriorates
Solution Approach 1:
The invention changes the switching frequency parameter to low-frequency operation synchronized with the AC power source period. This parameter change allows the reactor to operate effectively at lower frequencies, enabling the use of smaller, less expensive reactors while maintaining adequate harmonic suppression performance through the synchronized switching mechanism.
4Ease of manufacture
If switching frequency is reduced to lower cost and prevent high-frequency noise, then manufacturing cost is reduced, but control processing speed decreases
Solution Approach 1:
The invention changes the switching frequency parameter to low-frequency operation synchronized with the AC power source period, performing switching operations at least twice in half a cycle. This parameter change reduces manufacturing cost and eliminates high-frequency noise while the synchronous control mechanism maintains adequate processing speed by coordinating with the fixed power source frequency.
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 enables the suppression of harmonic currents, reduces reactor size, and lowers switching frequencies, thereby decreasing costs and preventing high-frequency noise issues, allowing for practical implementation at a lower cost.
Implementation Method 1
a rectifier (2) connected with an AC source (1) through a reactor (5)
Implementation Method 2
a plurality of capacitors (6, 7) having a voltage polarity connected between output terminals of the rectifier (2) in series
Data Source
Figure 1~2(c)
Figure 3~4
Figure 5(a)~5(h)
AI summary
To improve power factor by suppressing harmonics current at low cost and at the same time downsize a reactor. A rectifier (2) connected with an AC source through a reactor (5), a plurality of capacitors (6, 7) connected in series between output terminals of the rectifier (2), first switching means (3) connected between one input terminal of the rectifier (2) and a connection point of a plurality of capacitors, second switching means (4) connected between other input terminal of the rectifier (2) and the connection point of a plurality of capacitors, and a plurality of diodes (10, 11) connected with the plurality of capacitors in inverse-parallel are provided.