This study develops a newly designed, patented, bidirectional dc/dc converter (BDC) that interfaces a main energy storage (ES1), an auxiliary energy storage (ES2), and dc-bus of different voltage levels, for application in hybrid electric vehicle systems. The proposed converter can operate in a step-up mode (i.e., low-voltage dual-source-powering mode) and a step-down (i.e., high-voltage dc-link energy-regenerating mode), both with bidirectional power flow control. In addition, the model can independently control power flow between any two low-voltage sources (i.e., low-voltage dual-source buck/boost mode). Herein, the circuit configuration, operation, steady-state analysis, and closed-loop control of the proposed BDC are discussed according to its three modes of power transfer. Moreover, the simulation and experimental results for a 1 kW prototype system are provided to validate the proposed converter.
- Bidirectional dc/dc converter (BDC)
- Dual battery storage
- Hybrid electric vehicle
Fig. 1. Typical functional diagram for a FCV/HEV power system.
EXPECTED SIMULATION RESULTS
Fig.2. Measured waveforms for low-voltage dual-source-powering mode: (a) gate signals; (b) output voltage and inductor currents.
Fig.3. Measured waveforms for high-voltage dc-bus energy-regenerating mode: (a) gate signals; (b) output voltage and inductor currents.
Fig. 4. Measured waveforms of gate signals, output voltage and inductor currents for the low-voltage dual-source buck/boost mode: (a) buck mode; (b) boost mode.
Fig. 5. Waveforms of controlled current step change in the low-voltage dual-source-powering mode: (a) by simulation; and (b) by measurement. (iH is changed from 0 to 0.85 A; iL1 is changed from 0 to 2.5 A; Time/Div=20 ms/Div)
Fig. 6. Waveforms of controlled current step change in the low-voltage dual-source boost mode: (a) by simulation; and (b) by measurement. (iES1 is changed from 0 to -6 A; iL2 is changed from 0 to 12 A; Time/Div=20 ms/Div)
Fig. 7. Waveforms of controlled current step change in the low-voltage dual- source buck mode: (a) by simulation; and (b) by measurement. (iES1 is changed from 0 to 6 A; iL2 is changed from 0 to 12 A; Time/Div=20 ms/Div)
A new BDC topology was presented to interface dual battery energy sources and high-voltage dc bus of different voltage levels. The circuit configuration, operation principles, analyses, and static voltage gains of the proposed BDC were discussed on the basis of different modes of power transfer. Simulation and experimental waveforms for a 1 kW prototype system highlighted the performance and feasibility of this proposed BDC topology. The highest conversion efficiencies were 97.25%, 95.32%, 95.76%, and 92.67% for the high-voltage dc-bus energy-regenerative buck mode, low-voltage dual-source-powering mode, low-voltage dual-source boost mode (ES2 to ES1), and low-voltage dual-source buck mode (ES1 to ES2), respectively. The results demonstrate that the proposed BDC can be successfully applied in FC/HEV systems to produce hybrid power architecture (has been patented ).
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