Journal of Power Electronics

The Korean Institute of Power Electronics (전력전자학회)
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Design Methodology of a Three-Phase Dual Active Bridge Converter for Low Voltage Direct Current Applications

  • Lee, Won-Bin (School of Electrical Engineering, Ulsan National Institute of Science and Technology) ;
  • Choi, Hyun-Jun (School of Electrical Engineering, Ulsan National Institute of Science and Technology) ;
  • Cho, Young-Pyo (Smart-Grid Group Power Distribution Lab, KEPCO Research Institute) ;
  • Ryu, Myung-Hyo (Power Conversion and Control Research Center, HVDC Research Division, KERI) ;
  • Jung, Jee-Hoon (School of Electrical Engineering, Ulsan National Institute of Science and Technology)
  • Received : 2017.07.26
  • Accepted : 2017.12.30
  • Published : 2018.03.20
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Abstract

The practical design methodology of a three-phase dual active bridge (3ph-DAB) converter applied to low voltage direct current (LVDC) applications is proposed by using a mathematical model based on the steady-state operation. An analysis of the small-signal model (SSM) is important for the design of a proper controller to improve the stability and dynamics of the converter. The proposed lead-lag controller for the 3ph-DAB converter is designed with a simplified SSM analysis including an equivalent series resistor (ESR) for the output capacitor. The proposed controller can compensate the effects of the ESR zero of the output capacitor in the control-to-output voltage transfer function that can cause high-frequency noises. In addition, the performance of the power converter can be improved by using a controller designed by a SSM analysis without additional cost. The accuracy of the simplified SSM including the ESR zero of the output capacitor is verified by simulation software (PSIM). The design methodology of the 3ph-DAB converter and the performance of the proposed controller are verified by experimental results obtained with a 5-kW prototype 3ph-DAB converter.

Keywords

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Fig. 1. Conceptual diagram of a LVDC system.

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Fig. 2. Schematic of three-phase DAB converter.

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Fig. 3. Theoretical waveforms of a three-phase DAB converter inthe forward power flow.

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Fig. 4. Comparison of the RMS current and reactive powerbetween the Y-Y windings and Y-？ windings.

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Fig. 5. Loss comparisons between the Y-Y and Y-Δ connections.

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Fig. 6. Control-to-output voltage transfer function of a three-phase DAB converter from 0 Hz to 100 kHz.

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Fig. 7. Magnitude and phase Bode plots of a transfer functionaccording to output capacitance increments.

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Fig. 8. Closed-loop gain with a PI controller.

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Fig. 9. Closed-loop gain with a 2P1Z controller.

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Fig. 10. Comparison of the output impedances using a PI and a2P1Z controller in the s-domain.

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Fig. 11. Comparison of the transient performance using a PI anda 2P1Z controller in the time-domain.

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Fig. 12. 5 kW prototype of the three-phase DAB converter.

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Fig. 13. Experimental waveforms during steady-state operation: (a) 500 W; (b) 1.5 kW; (c) 3.5 kW; (d) 5 kW.

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Fig. 14. Comparison of the controller performance: (a) PIcontroller (7A？14A); (b) 2P1Z controller (7A？14A).

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Fig. 15. Bi-directional experimental waveform (3.5 kW ？ -3.5 kW).

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Fig. 16. Efficiency graphs of the proposed converter using a PIand a 2P1Z controller.

TABLE I DESIGN SPECIFICATIONS

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TABLE II PERFORMANCE COMPARISON

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