Power Converter Segmentation for Loss Reduction
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Solution Overview
Problem
Conventional power converters face issues with increased power loss and noise due to the need for large short-circuit switches and complex circuit structures when trying to improve input power factor, especially when the output voltage is increased, and they require large current-limiting circuits.
Innovation Solution
A power converter design that includes a PWM-controlled DC voltage source, reactors for current limiting, and a control circuit system to manage short-circuit switches and rectification modes, allowing for efficient control of the inverter circuit based on current commands to maintain a target output voltage and improve the input power factor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output voltage is increased, then the power conversion capability is improved, but the turn-on time of the short-circuit switch increases causing increased power loss
Solution Approach 1:
The patent divides the single large smoothing capacitor into multiple smaller capacitors connected in series. This segmentation allows the short-circuit switch to operate at lower voltage levels during charging, reducing the turn-on time and power loss while still achieving the required total output voltage through the series connection of multiple capacitors.
Solution Approach 2:
The patent changes the voltage distribution parameters by introducing multiple capacitors with different voltage ratings in series. Each capacitor operates at a lower voltage level, which enables the short-circuit switch to charge them more quickly with reduced power loss, while the cumulative voltage meets the required output specification.
2Power
If the DC voltage of the inverter circuit is increased, then the power output capability is improved, but the current control precision reduces and noise increases
Solution Approach 1:
The patent segments the DC voltage source into multiple smaller voltage sources connected in series. This segmentation allows each individual voltage source to operate at lower voltage levels with better current control precision and lower noise, while the total power output capability is maintained through the series connection.
3Loss of energy
If the number of single-phase inverters connected in series is increased, then the power loss and noise problems are avoided, but the circuit structure and control become complicated
Solution Approach 1:
The patent combines multiple capacitor charging operations into a single unified circuit structure with one short-circuit switch that can charge multiple series-connected capacitors. This merging approach achieves the power loss and noise benefits of multiple inverters without the complexity of having separate inverter circuits for each capacitor.
4Reliability
If a current-limiting reactor is increased in size, then the current limiting capability is improved, but the circuit size increases
Solution Approach 1:
The patent segments the current limiting function across multiple series-connected capacitors rather than relying on a single large reactor. Each capacitor inherently limits current based on its voltage and capacitance, providing effective current limiting capability without requiring a large physical reactor.
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 design reduces power loss and noise, eliminates the need for large current-limiting circuits, and simplifies the device structure, promoting a more compact and efficient power conversion process.
Implementation Method 1
a reactor (L) connected in series in one of a preceding stage and a subsequent stage of the inverter circuit (5), for limiting a current
Implementation Method 2
a first smoothing capacitor (22) and a second smoothing capacitor (23) which are connected in series with each other between the first DC output terminal and the second DC output terminal of the rectifying circuit
Implementation Method 3
the inverter circuit (5) superimposing a generated voltage, which is a discharge voltage of the DC voltage source (10), on an AC input voltage of the AC input power supply
Data Source
AI summary
A power converter includes an inverter circuit for superimposing a generated voltage on an AC input voltage, a diode bridge full-wave rectifying circuit connected to the inverter circuit, smoothing capacitors connected between DC output terminals of the rectifying circuit, short-circuit switches connected to the rectifying circuit, a rectification mode changing circuit connected to the rectifying circuit, a short-circuit switch control circuit for maintaining the short-circuit switches in an on state in a short-circuit phase range, a rectification mode control circuit for maintaining the rectification mode changing circuit in an off state in the short-circuit phase range and an inverter control circuit for PWM-controlling the inverter circuit so that an output voltage of the rectifying circuit follows a target output voltage when the rectification mode changing circuit is in the off state.