Power Conversion Device Eliminating Commercial Transformers
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Solution Overview
Problem
Existing power conversion devices experience significant power loss due to conduction and switching losses in converter and inverter circuits, and require a commercial frequency transformer for voltage compensation, leading to increased size and voltage disturbance during alternating current power supply fluctuations or interruptions.
Innovation Solution
A power conversion device with an inverter circuit using a switching element series circuit and bidirectional switches, where the control circuit generates pulse width modulated signals to manage switching elements and bidirectional switches, allowing for efficient voltage output without commercial frequency transformers, reducing switching losses, and maintaining stable output voltage during power supply fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If converter circuit and inverter circuit are used to convert AC voltage to DC voltage and then back to AC voltage, then voltage can be supplied to load, but conduction loss and switching loss occur in the switching elements
Solution Approach 1:
The patent extracts and eliminates the converter circuit from the system. By directly connecting the AC power supply to the inverter circuit through a reactor, the intermediate DC conversion stage is removed, thereby eliminating conduction loss and switching loss associated with the converter circuit's switching elements while maintaining voltage conversion capability through the inverter circuit alone
Solution Approach 2:
The patent merges the functions of voltage compensation and voltage conversion into a single inverter circuit. The inverter circuit directly processes AC input voltage and outputs compensated AC voltage to the load, combining multiple functions into one circuit to reduce the number of switching elements and associated losses
2Power
If converter circuit and inverter circuit are used for voltage conversion, then alternating current voltage can be supplied to load, but the device complexity increases due to multiple circuits and switching elements
Solution Approach 1:
The patent extracts and removes the converter circuit from the system configuration. By eliminating this intermediate circuit stage and its associated switching elements (Qp, Qn, Cp, Cn), the overall device complexity is reduced while the inverter circuit maintains the necessary voltage conversion functionality
Solution Approach 2:
The inverter circuit is designed to perform multiple functions: it converts AC input voltage, compensates for voltage drops, and supplies power to the load. This multi-functional design eliminates the need for separate converter and inverter circuits, thereby reducing device complexity
3Reliability
If commercial frequency transformer is used for voltage compensation, then voltage fluctuation can be compensated, but the device size increases
Solution Approach 1:
The patent replaces the mechanical/commercial frequency transformer with an electronic inverter circuit that uses switching elements to generate compensating voltage. This substitution eliminates the need for large commercial frequency transformers while maintaining voltage compensation capability through electronic control
Solution Approach 2:
The patent changes the operating frequency from commercial frequency to high-frequency switching operation. By using high-frequency switching elements in the inverter circuit, voltage compensation is achieved without requiring the large physical size associated with commercial frequency transformers
4Reliability
If converter circuit and inverter circuit are used for power conversion, then voltage can be supplied during power supply interruption, but switching loss occurs in each switching element
Solution Approach 1:
The patent extracts and eliminates the converter circuit from the system. By removing this intermediate stage with its switching elements (Qp, Qn), switching loss is reduced while the inverter circuit maintains the ability to supply power during interruptions through direct AC input processing
Solution Approach 2:
The inverter circuit is designed to continuously process AC input voltage and provide output to the load without interruption. By eliminating the converter circuit's switching elements that cause loss, the system maintains continuous useful action with reduced energy loss in the switching components
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 reduces power loss and eliminates the need for commercial frequency transformers, providing stable alternating current voltage output with reduced switching losses and no disturbance during voltage fluctuations or interruptions.
Implementation Method 1
The converter circuit causes the switching elements Qp and Qn to be turned on and off, thereby rectifying the voltage of the alternating current power supply 1
Implementation Method 2
The inverter circuit 4 causes the switching elements Q1 and Q2 to be turned on and off, thereby converting the voltage of the direct current power supply formed of the capacitors Cp and Cn into alternating current voltage
Implementation Method 3
The filter circuit 5 removes the high frequency contents from the alternating current voltage output by the inverter circuit 4
Implementation Method 4
compensating voltage for compensating for the drop in the voltage of the alternating current power supply 1 is generated on the primary side of the transformer 8
Implementation Method 5
the control circuit generates control signals for causing the positive side and negative side switching elements and first to fourth switch elements to carry out on-off operations. The control circuit divides the cycle of a voltage command into a plurality of control periods when generating the control signal for each element.
Data Source
Figure 1
Figure 2(a)~2(c)
Figure 3
AI summary
Provided is a power conversion device such that a constant voltage can be supplied to a load even when the voltage of an alternating current power supply fluctuates. A series circuit of a switching element Q1 and switching element Q2 connected to both ends of a direct current power supply series circuit 30 is formed, a connection point of a direct current power supply Psp and direct current power supply Psn is adopted as a neutral point terminal O, a connection point of the switching element Q1 and switching element Q2 is adopted as an output terminal U, switch elements S1 and S2 are connected in anti-parallel between the output terminal U and neutral point terminal O, switch elements S3 and S4 are connected in anti-parallel between a terminal R of an alternating current power supply, of which a terminal S is connected to the neutral point terminal O, and the output terminal U, and a first element and second element selected from among the switching elements Q1 and Q2 and switch elements S1 to S4 are turned on and off in a complementary way either side of an idle period.