This paper investigates a novel pulse width modulation (PWM) scheme for two-phase interleaved boost converter with voltage multiplier for fuel cell power system by combining alternating phase shift (APS) control and traditional interleaving PWM control. The APS control is used to reduce the voltage stress on switches in light load while the traditional interleaving control is used to keep better performance in heavy load. The boundary condition for swapping between APS and traditional interleaving PWM control is derived. Based on the aforementioned analysis, a full power range control combining APS and traditional interleaving control is proposed. Loss breakdown analysis is also given to explore the efficiency of the converter. Finally, it is verified by experimental results.
KEYWORDS: Boost converter, Fuel cell, Interleaved, Loss breakdown, Voltage multiplier.
Fig. 1. Grid-connected power system based on fuel cell.
Fig. 2. Main theoretical waveforms at boundary condition.
Fig.3 Experimental results at boundary condition with traditional interleaving control (L = 1158 μH, R = 2023 Ω, and D = 0.448). (a) CH1-S1 Driver Voltage, CH2 − L1 Current, CH3-S1 Voltage Stress, CH4-Output Voltage, (b) CH1-S1 Driver Voltage, CH2 − C1 Current, CH3-S1 Voltage Stress, CH4-OutputVoltage, (c) CH1-S1 DriverVoltage,CH2 − D1 Current,CH3-S1 Voltage Stress, CH4-Output Voltage, (d) CH1-S1 Driver Voltage, CH2 −DM1 Current, CH3-S1 Voltage Stress, CH4-Output Voltage.
Fig. 4. Traditional interleaving control at nominal load (L = 1158 μH and R = 478 Ω).]
Fig. 5. Traditional interleaving control in Zone A (L = 1158 μH and R = 1658 Ω).
The boundary condition is derived after stage analysis in this paper. The boundary condition classifies the operating states into two zones, i.e., Zone A and Zone B. The traditional interleaving control is used in Zone A while APS control is used in Zone B. And the swapping function is achieved by a logic unit. With the proposed control scheme, the converter can achieve low voltage stress on switches in all power range of the load, which is verified by experimental results.
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