Isolated Bidirectional DC-DC Converter Fault Control for Soft Switching
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Solution Overview
Problem
Existing bidirectional isolated DC-DC converters face challenges in achieving fault-tolerant operation with high efficiency without additional components, as they often experience efficiency deterioration due to soft switching failure and increased transformer current during component faults.
Innovation Solution
A bidirectional isolated DC-DC converter with a controller that dynamically adjusts the operation of primary and secondary inverters based on fault states, using a limiter to control phase difference and generate gate signals to maintain optimal switching modes, reducing voltage applied to transformer leakage inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter operates in half-bridge operation due to a fault, then fault-tolerant operation is achieved, but efficiency deteriorates due to soft switching failure and increased transformer current
Solution Approach 1:
The patent dynamically adjusts the switching operation mode based on fault conditions. During normal operation, full-bridge mode is used for high efficiency. When a fault is detected, the system transitions to half-bridge operation to maintain reliability, and further transitions to quarter-bridge operation if needed, optimizing the balance between reliability and efficiency in real-time
Solution Approach 2:
The patent changes the switching parameters (which switches are ON/OFF) based on the fault state. By selectively activating different switch combinations (full-bridge, half-bridge, or quarter-bridge modes), the system adapts its electrical parameters to maintain efficient operation even under fault conditions
2Reliability
If additional components are added to achieve high-efficiency and fault-tolerant operation, then reliability and efficiency are improved, but device complexity increases
Solution Approach 1:
The patent uses the existing switching devices (S1-S8) and transformer to achieve fault-tolerant operation without adding extra components. The system reconfigures the existing components through different switching patterns (full-bridge, half-bridge, quarter-bridge modes) to handle faults, making the system self-sufficient in fault management
Solution Approach 2:
The existing switching devices serve multiple functions: during normal operation they perform standard power conversion, and during fault conditions they reconfigure to provide fault tolerance. The same hardware infrastructure supports multiple operation modes, eliminating the need for dedicated fault-handling components
Data Source
AI summary
A bidirectional isolated DC-DC converter includes a primary-side inverter; a first DC cut capacitor connected to the AC side of the primary-side inverter; a secondary-side inverter; a second DC cut capacitor connected to the AC side of the secondary-side inverter; a transformer having a primary winding connected to the AC side of the primary-side inverter, and a secondary winding connected to the AC side of the secondary-side inverter; and a control unit that controls switching devices of the primary-side inverter and the secondary-side inverter. The control unit determines an operation of the primary-side inverter and an operation of the secondary-side inverter so as to reduce an increase in voltage to be applied to leakage inductances of the transformer, in accordance with failure states of the switching devices.