Three-phase power supply conversion circuit, circuit control method, circuit board and air conditioner
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Solution Overview
Problem
In high-efficiency variable-frequency air-conditioning systems powered by a three-phase power supply, the direct-current fan load cannot be directly powered from the high-voltage direct-current bus due to the insufficient withstand voltage of the Intelligent Power Module (IPM), leading to unbalanced three-phase currents and increased harmonics.
Innovation Solution
A three-phase power supply conversion circuit with a rectifier module, energy storage module, and control module, including a bidirectional switch assembly and capacitors, which balances phase voltages and maintains stable voltage levels, allowing direct-current loads to be powered from the capacitors and balancing three-phase currents to reduce harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an independent phase voltage is rectified to power the direct-current fan, then the withstand voltage requirement of the IPM module is met, but the three-phase currents become unbalanced and harmonics increase
Solution Approach 1:
The patent combines the power supply for the direct-current fan with the high-voltage direct-current bus, merging two previously separate power supply paths into one. This allows the fan to be powered from the same bus that supplies the variable-frequency compressor, ensuring three-phase current balance and reducing harmonics while meeting voltage requirements through proper component selection and circuit design
2Object-generated harmful factors
If the direct-current fan is powered from the high-voltage direct-current bus, then three-phase current balance is maintained, but the IPM module cannot withstand the voltage
Solution Approach 1:
The patent segments the high-voltage direct-current bus into two separate capacitor banks (first capacitor bank and second capacitor bank) with different voltage ratings. The first capacitor bank is connected to the positive terminal and the second to the negative terminal, creating distinct voltage zones that allow the IPM module to operate at safe voltage levels while still being powered from the high-voltage bus system
Solution Approach 2:
The patent introduces capacitor banks as intermediary components between the high-voltage direct-current bus and the IPM module. These capacitors act as voltage buffers and isolators, allowing the IPM module to be powered from the high-voltage bus without being directly exposed to voltages exceeding its withstand capability
3Reliability
If a two-stage series connection mode is used for the high-voltage electrolytic capacitor, then the withstand voltage reaches 900V theoretically, but the IPM module still cannot be directly powered due to derating requirements
Solution Approach 1:
The patent applies different voltage ratings to different parts of the capacitor system - the first capacitor bank is rated for higher voltage (connected to positive terminal) while the second capacitor bank is rated for lower voltage (connected to negative terminal). This local differentiation allows the system to handle high voltages where needed while protecting the IPM module in regions where it cannot withstand high voltages
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 stabilizes voltage levels for direct-current loads, balances three-phase currents, and effectively reduces harmonics, ensuring efficient operation of the air-conditioning system.
Implementation Method 1
the energy storage module includes a first capacitor and a second capacitor which are connected in series to each other
Data Source
AI summary
A three-phase power supply conversion circuit includes rectifier, energy storage, direct-current load, and control modules. The rectifier module includes a three-phase rectifier bridge including three bridge arms connected in parallel to each other, and a bidirectional switch assembly including three bidirectional switches. One ends of the three bidirectional switches are connected to midpoints of the three bridge arms, respectively. The energy storage module is connected to a direct-current output end of the rectifier module and includes first and second capacitors connected in series to each other. Other ends of the three bidirectional switches are connected between the first and second capacitors. The control module is connected to the bidirectional switch assembly and configured to control the bidirectional switches according to phase voltages of a three-phase alternating-current power supply, to maintain a voltage between two ends of the first or second capacitor at a target voltage.