Cascade Series Resonant Converter with ZVS Assistance Networks
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Solution Overview
Problem
High voltage power conversion systems face challenges with voltage imbalance, complex control requirements, and excessive circulating currents in multilevel converters, particularly in diode-clamped and capacitor-clamped topologies, which become unwieldy beyond five levels, and cascaded converters require multiple isolated DC sources, limiting their application.
Innovation Solution
A dual series resonant converter (SRC) with zero voltage switching (ZVS) and controllable impedance assistance networks is used in a cascade connection, enabling equal power distribution and voltage balancing across series-connected converters, reducing switching losses and alleviating cross-conduction issues through ZVS assistance networks with controllable inductors and sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If diode-clamped or capacitor-clamped multilevel converters are used, then high output voltage is achieved, but voltage imbalance and complex control requirements occur
Solution Approach 1:
The converter is divided into multiple independent series resonant converter cells connected in cascade, where each cell operates autonomously with its own control. This segmentation eliminates the need for complex inter-cell control coordination required in diode-clamped or capacitor-clamped topologies, while still achieving high output voltage through series connection of cell outputs.
Solution Approach 2:
Instead of using clamping diodes or capacitors to limit switch voltages (conventional approach), the invention uses series resonant converter cells with inherent voltage balancing capability. The inversion lies in achieving voltage balance not through active control of clamping elements, but through the natural operating characteristics of series resonant converters with ZVS assistance.
2Power
If diode-clamped or capacitor-clamped converters are used, then high output voltage is achieved, but excessive circulating currents occur
Solution Approach 1:
By segmenting the converter into multiple series resonant cells, circulating currents are confined to individual cells rather than flowing through the entire system. Each cell's resonant inductor limits circulating current locally, reducing overall energy losses compared to clamped topologies where circulating currents traverse the full converter structure.
3Stability of the object's composition
If cascaded converters with separate DC sources are used, then voltage balance is achieved, but device complexity increases due to multiple isolated sources
Solution Approach 1:
Multiple series resonant converter cells share a common DC voltage source instead of requiring separate isolated DC sources for each cell. The cells are connected in cascade with series switching devices, and voltage balance is achieved through the inherent operating characteristics of series resonant converters with ZVS assistance, eliminating the need for multiple isolated sources while maintaining stable voltage distribution.
4Power
If conventional switching is used in high voltage environments, then power conversion is achieved, but cross-conduction and spurious turn-on occur
Solution Approach 1:
ZVS assistance networks are implemented to pre-charge or pre-discharge the output capacitances of switching devices before they switch. This preliminary action ensures that switches turn on when their voltage is already zero, preventing cross-conduction and spurious turn-on caused by high dV/dt in hard switching environments. The assistance networks are activated in advance of the main switching event.
Solution Approach 2:
ZVS assistance networks act as intermediary circuits between the main power switching devices and the load. These networks provide a controlled path for capacitive discharge and voltage equalization, mediating the high-stress switching transitions and preventing direct cross-conduction between series-connected switches. The assistance networks absorb the harmful dV/dt effects before they reach the main switching devices.
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 ensures reliable and efficient high voltage power conversion with equal voltage and power sharing between individual converters, reducing circulating currents and enhancing reliability by maintaining ZVS under all load conditions, thus improving the robustness and efficiency of high voltage switching environments.
Implementation Method 1
dual series resonant converter (SRC) with zero voltage switching (ZVS)
Implementation Method 2
first and second zero voltage switching (ZVS)-assistance networks are operably coupled between the first SRC and the second SRC
Data Source
AI summary
A method of providing power to a load is provided. A first series resonant converter is provided. A second SRC is operably coupled to the first SRC in a cascade connected arrangement. First and second zero voltage switching (ZVS)-assistance networks are operably coupled between the first SRC and the second SRC, such that the first and second ZVS-assistance networks are providing first and second ZVS-assistant currents flowing from each ZVS-assistance network to the cascade connected arrangement of SRCs. Power from a power source is received at the cascade connected arrangement of first and second SRCs, power from a power source. The cascade connected arrangement of first and second SRCs supplies an output voltage to the load in response to receiving power from the power source.