Polyphase Current Supplying Circuit Voltage Stabilization
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Solution Overview
Problem
In polyphase current supplying circuits with a significantly reduced smoothing capacitor, the high harmonic content and unstable ac power supply lead to increased peak values of rectified voltage, which can trigger overvoltage protection and violate harmonic regulations.
Innovation Solution
Incorporating a reactor and a peak-value suppressing device, including a diode, capacitor, resistor, and switch, to form a series resonant circuit that reduces harmonic content and suppresses peak rectified voltage by consuming charge and dissipating energy, thereby stabilizing the voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the smoothing capacitor capacitance is significantly reduced, then the size of the smoothing capacitor is reduced, but the rectified voltage develops large pulsating components and harmonic content increases
Solution Approach 1:
The patent introduces a series reactor as an intermediary component between the diode bridge and the reduced smoothing capacitor. This reactor acts as a mediator that filters harmonic currents while allowing the capacitor to remain small, thus resolving the contradiction between capacitor size reduction and harmonic suppression.
Solution Approach 2:
The patent creates a composite filtering system by combining the series reactor and the reduced smoothing capacitor into a hybrid configuration. This composite structure leverages the inductive filtering capability of the reactor and the capacitive filtering of the smaller capacitor to achieve effective harmonic reduction without requiring a large capacitor.
2Volume of moving object
If the smoothing capacitor capacitance is significantly reduced, then the size of the smoothing capacitor is reduced, but the rectified voltage pulsation increases
Solution Approach 1:
The series reactor serves as an intermediary that smooths the interaction between the rectifier and the reduced capacitor, filtering out high-frequency pulsations while allowing the capacitor to maintain DC voltage with reduced size.
3Object-generated harmful factors
If a series reactor is added to reduce harmonic content, then harmonic content is reduced, but the circuit complexity increases
Solution Approach 1:
The series reactor is designed to perform multiple functions simultaneously: it filters harmonic currents, limits inrush current to the capacitor, and works synergistically with the reduced capacitor to maintain voltage stability. This multi-functionality justifies the added component by providing several benefits from a single element.
4Reliability
If the rectified voltage peak value is suppressed using a peak-value suppressing device, then overvoltage protection is prevented, but the device complexity increases
Solution Approach 1:
The peak-value suppressing function is merged into the existing series reactor and capacitor configuration. The same reactive components that filter harmonics also naturally limit voltage peaks through their impedance characteristics, eliminating the need for separate active voltage clamping circuits and reducing overall complexity.
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 effectively reduces harmonic content and stabilizes the rectified voltage, preventing overvoltage protection activation while adhering to harmonic regulations, thus ensuring efficient operation of the polyphase current supplying circuit.
Implementation Method 1
a series resonant circuit constituted of them corresponds to harmonics of very high order
Implementation Method 2
a diode bridge 11. However, an inductance parasitic to the power supply system is shown as an inductor 22 connected in series with the ac power supply 21
Implementation Method 3
The smoothing circuit 12 is composed only of a smoothing capacitor C having a small capacitance
Implementation Method 4
a peak-value suppressing device (Ds, Rs, Cs, Rc, S1; RL, S2; RB, Q; ZD) suppressing a peak value of the rectified voltage
Data Source
AI summary
This invention is to reduce a voltage across a smoothing capacitor in a single-phase capacitorless inverter. A smoothing circuit (15) has a smoothing capacitor (C) connected between a pair of power supply lines (L1, L2). A diode (Ds) has its anode connected to one of the power supply lines (L1) and has its cathode connected to an end of a resistor (Rs), the other end of the resistor is connected to an end of a capacitor (Cs), the other end of the capacitor is connected to the other of the power supply lines (L2). In this way, the magnitude of a rectified voltage (Vdc) across the smoothing capacitor (C) can be reduced as compared with an absence of the series connection of diode (Ds), resistor (Rs) and capacitor (Cs).