Soft Switching Solid State Transformers Using Auxiliary Resonant Circuits
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Solution Overview
Problem
Conventional solid state transformers and converters face inefficiencies and reliability issues due to hard-switching transitions, high device stress, and electromagnetic interference, particularly in high-frequency isolation applications, which limits their practical application in power conversion and isolation.
Innovation Solution
The introduction of soft-switching solid state transformers and converters that utilize high-frequency transformers, current-source inverter bridges with reverse blocking switch assemblies, and auxiliary resonant circuits to achieve zero-voltage switching, reducing switching losses and mitigating electromagnetic interference, while simplifying converter operation and eliminating the need for complex leakage management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If hard-switching transitions are used in conventional solid state transformers, then the device structure is simpler, but switching losses increase and reliability decreases due to high device stress and electromagnetic interference
Solution Approach 1:
An auxiliary resonant circuit is introduced as an intermediary component between the main power circuit and the switching devices. This resonant circuit includes resonant inductors and capacitors that create a soft-switching environment, enabling zero-voltage or zero-current switching transitions and significantly reducing switching losses and electromagnetic interference.
Solution Approach 2:
The patent employs periodic resonant oscillations through the auxiliary resonant circuit to achieve soft-switching conditions. By timing the switching operations to coincide with specific phases of the resonant waveform, the converter achieves zero-voltage switching (ZVS) or zero-current switching (ZCS), eliminating hard-switching losses while maintaining a practical circuit structure.
2Volume of moving object
If high frequency isolation is implemented, then volume and weight of magnetic materials are reduced, but electromagnetic interference and device stress increase
Solution Approach 1:
The patent converts the potentially harmful high-frequency electromagnetic interference into a beneficial soft-switching resonant waveform. The auxiliary resonant circuit transforms the abrupt hard-switching transitions into smooth periodic resonant oscillations, maintaining the volume and weight benefits of high-frequency operation while eliminating the harmful EMI effects through controlled resonant waveforms.
3Productivity
If soft switching is implemented to reduce switching losses, then converter efficiency improves, but device complexity increases due to auxiliary resonant circuits
Solution Approach 1:
The auxiliary resonant circuit is designed to serve multiple functions simultaneously: it provides soft-switching conditions for reduced losses, enables bi-directional power flow control, supports voltage regulation, and facilitates harmonic suppression. This multi-functionality justifies the additional circuit elements by delivering multiple performance benefits from a single integrated structure.
4Adaptability or versatility
If reverse blocking switch assemblies are used, then bi-directional power flow control is achieved, but device stress and manufacturing complexity increase
Solution Approach 1:
The reverse blocking switch assemblies are configured to automatically handle bi-directional power flow without requiring complex external control circuits. The intrinsic reverse blocking capability of the switches, combined with the resonant circuit topology, enables self-commutation and automatic adaptation to power flow direction, simplifying the control architecture and reducing manufacturing complexity despite the specialized switch requirements.
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 solution enhances converter efficiency, reliability, and immunity to layout parasitic elements, allowing for bi-directional power flow, voltage regulation, and harmonic suppression across a full load range with reduced device stress and electromagnetic interference.
Implementation Method 1
an auxiliary resonant circuit coupled to a winding connection of the HF transformer, the auxiliary resonant circuit comprising a resonant capacitor coupled across the winding connection
Data Source
AI summary
Various examples are provided for soft switching solid state transformers and converters, and their operation and application. In one example, a soft switching solid state power transformer includes a high frequency (HF) transformer; first and second auxiliary resonant circuits coupled to the HF transformer; and first and second current-source inverter (CSI) bridges coupled to the corresponding first auxiliary resonant circuits. The first and second CSI bridges include reverse blocking switch assemblies that conduct current in one direction and block voltage in both directions. In another example, a reactive power compensator includes a high frequency (HF) transformer, first, second and third auxiliary resonant circuits coupled to the HF transformer, and first, second and third current-source inverter (CSI) bridges coupled to the corresponding first auxiliary resonant circuits. In another example, a converter includes an auxiliary resonant circuit coupled across an inductor and first and second CSI bridges coupled across the inductor.