Power Conversion Device Voltage Fluctuation Compensation
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Solution Overview
Problem
Existing power conversion devices face limitations in compensating for wide voltage fluctuations and surge voltage issues, leading to increased size, cost, and inefficiency, particularly in handling asynchronous power sources and momentary voltage drops.
Innovation Solution
A power conversion device with a series circuit configuration including bidirectional switching elements, capacitors, and rectifier elements, along with a drive control unit that manages switching elements to maintain constant voltage across a load, absorbs energy during switching off, and adjusts operation modes to handle varying voltage and frequency conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bidirectional switching elements are used to compensate for AC power source voltage drop, then load voltage can be maintained, but surge voltage occurs when switching elements are cut off
Solution Approach 1:
A snubber circuit comprising a snubber capacitor and snubber resistor is introduced as an intermediary element between the bidirectional switching element and the circuit nodes. This snubber circuit absorbs the surge voltage generated when the bidirectional switching element is cut off, preventing it from affecting other components. The snubber capacitor charges during the on-state and discharges during the off-state, while the snubber resistor dissipates the stored energy, effectively suppressing voltage spikes and protecting the switching element and surrounding circuitry.
2Reliability
If voltage compensation range is widened to handle momentary voltage drops, then reliability improves, but semiconductor switching elements and inductor increase in size
Solution Approach 1:
The voltage compensation function is segmented into two independent parts: the bidirectional switching element circuit handles normal voltage fluctuations within a limited range, while the snubber circuit handles momentary voltage drops and surge conditions. This segmentation allows each component to be optimized for its specific function, preventing the need to oversize components for worst-case scenarios. The bidirectional switching element maintains load voltage under normal conditions, while the snubber circuit activates during abnormal conditions, enabling reliable operation across a wide voltage range without increasing overall device size.
3Reliability
If bidirectional switching elements are used for voltage compensation, then load voltage stability improves, but device complexity increases
Solution Approach 1:
The snubber circuit is merged with the existing bidirectional switching element circuit by sharing common nodes (anode and cathode connections). The snubber capacitor is connected in parallel with the bidirectional switching element, and the snubber resistor is series-connected with the capacitor. This merging approach allows the snubber function to be integrated into the existing circuit topology without adding separate independent circuits, thereby improving load voltage stability while minimizing the increase in device 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 enables balanced voltage regulation over a wide range of alternating current power source fluctuations while suppressing surge voltage, avoiding size and cost increases, and maintaining efficiency by minimizing the number of switching elements used.
Implementation Method 1
a second series circuit, connected in parallel to the first bidirectional switching element 6, wherein a second bidirectional switching element 5 and capacitor 3 are connected in series
Implementation Method 2
a first series circuit wherein a first inductor 4 and first bidirectional switching element 6 are connected in series
Implementation Method 3
a serial switching element wherein 2N (N being a positive integer) switching elements, in each of which a diode is connected in anti-parallel, are connected in series
Data Source
AI summary
Aspects of the invention include a step-up/step-down chopper unit, an inverter unit, a rectifier unit, first to third voltage detection means, and a drive control unit. Voltage regulation means of the drive control unit, in accordance with a detected voltage value detected by the voltage detection means, generates control signals for keeping the effective voltage value of a capacitor constant. In some aspects of the invention, the effective voltage value of the capacitor is controlled to be constant by the switching elements of the step-up/step-down chopper unit and inverter unit being driven by the control signals. The rectifier unit can suppress a surge voltage by causing energy stored in a inductor to be absorbed by storage elements when bidirectional switching elements are turned off.