DC/AC Converter Energy Recovery Module Soft Switching
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Solution Overview
Problem
Conventional DC/AC converters for high-speed electrical machines face significant switching losses, current/voltage overruns, and electromagnetic emissions due to hard switching, while soft switching designs require energy dissipation in resistors, leading to efficiency losses.
Innovation Solution
A DC/AC converter with a voltage and current modulation circuit using coils and capacitors for soft switching, and an electrical energy recovery module that replaces the resistor to minimize energy losses and overshoots, utilizing MOSFET or IGBT switches and pulse width modulation for efficient energy conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If hard switching is used in conventional DC/AC converters, then the converter structure is simple, but switching losses are significant and incompatible with high-speed electrical machines
Solution Approach 1:
The patent introduces an intermediary circuit consisting of a capacitor connected in parallel with the switch and a coil connected in series with the switch. This intermediary circuit acts as a buffer that mediates the switching process, enabling soft switching by controlling the current and voltage transitions, thereby reducing switching losses while maintaining converter functionality.
Solution Approach 2:
The patent applies preliminary action by pre-charging the capacitor before switch closure and pre-establishing the current path through the coil. This preliminary preparation ensures that when the switch operates, the current and voltage are already in optimal states, preventing abrupt transitions and reducing switching losses.
2Device complexity
If hard switching is used, then component sizing can be reduced, but voltage and current overruns appear requiring oversized components
Solution Approach 1:
The patent applies beforehand cushioning by placing a capacitor in parallel with the switch and a coil in series with the switch before the switching event occurs. These components act as cushions that absorb and smooth out voltage and current overruns during switching, protecting the circuit from transient spikes without requiring oversized protective components.
3Productivity
If soft switching circuit is added to reduce switching losses, then switching frequency can be increased, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the capacitor and coil to serve multiple functions: the capacitor provides voltage smoothing, energy storage, and overvoltage protection; the coil provides current limiting, energy storage, and electromagnetic coupling. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity while enabling soft switching and higher switching frequencies.
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 switching losses, eliminates the need for oversized components, minimizes voltage and current overshoots, and significantly decreases energy dissipation, enhancing the efficiency and compatibility of converters for high-speed applications.
Implementation Method 1
a coil and a capacitor are added to the previous circuit. The coil modulates the di/dt current variation ('Turn-On')
Implementation Method 2
the capacitor modulates the voltage variation dv/dt ('Turn-Off')
Implementation Method 3
an electrical energy recovery module makes it possible to replace the resistance of the modulation circuit, in order to reduce energy losses
Data Source
Figure 1~2
Figure 3~5b
AI summary
The present invention relates to a DC-to-AC converter which comprises switching arms, a circuit for modulating voltage and current variations, and an electric energy recovery module. The energy recovery module is connected to the switching arms and to the modulating circuit.