Simulation and Implementation of Interleaved Boost DC-DC Converter for Fuel Cell Application



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Introduction

The fuel cell is drawing the attention by researchers as one of the most promising power supply in the
future. Due to high efficiency, high stability, low energy consumed and friendly to environment, this technology is
in the progress to commercialize. Fuel cell has higher energy storage capability thus enhancing the range of
operation for automobile and is a clean energy source [1-4]. Fuel cells also have the additional advantage of using
hydrogen as fuel that will reduce the world dependence on non-renewable hydrocarbon resources [3]. A Fuel Cell
Electric Vehicles (FCEV) has higher efficiency and lower emissions compared with the internal combustion engine
vehicles [1]. So, FCEV is providing a much better promising performance [4].
In FCEV application, the power supply system is composed of Fuel Cell Engine (FCE), Boost DC-DC
Converter, energy storage element, and bidirectional dc-dc converter [1-4], as show as in Fig. 1. In this system, a
high power dc-dc converter is needed to adjust the output voltage, current and power of FCE to meet the vehicle
requirements [2].


Interleaved Boost converter Operation

the schematic of the dual interleaved boost dc-dc converter. The interleaved boost dc-dc
converter consists of two parallel connected boost converter units, which are controlled by a phase-shifted switching
function (interleaved operation).
To illustrate interleaving operation, Fig. 3 shows the timing diagram of control signals to the switches.
Since this converter has two parallel units, the duty cycle for each unit is equal to (Vout-Vin)/Vout, and it is same
for each unit due to parallel configuration. A phase shift should be implemented between the timing signals of the
first and the second switch. Since there are two units parallel in this converter, the phase shift value is 180O.


PWM Signals Generation Technique

The pwm duty cycle signals are generated by comparing a level control signal (Vc) with a constant peak
repetitive triangle signal (Vst). The frequency of the repetitive triangle signal establishes the switching frequency.
Since the interleaved boost converter requires two pwm signals to drive both of switches, the additional work
necessary to generate two of pwm signals from single duty cycle formula. Fig. 4 shows the pwm signals generation
technique. The first pwm signal is produce when the control signal V1 is less than Vst and the second pwm signal is
produce when the control signal V2 is greater than Vst.
The value of the desired level control signal (Vc) is got from controller output. The values of control signal
V1 and V2 are given in (1) and (2), while the PWM signals are generated by (3).


Simulink Model and Simulation

An interleaved boost dc-dc converter system has been modeled using MATLAB SIMULINK. A
comprehensive simulation was conducted to verify the performance of interleaved boost dc-dc converter system.
Fig. 5 illustrated the Simulink model of the interleaved boost dc-dc converter scheme. The model parameters are
listed in Table 1. The simulation waveform of inteleaved boost dc-dc converter input current, inductor currents and
PWM signals


Hardware Prototype and Experiment Results

In order to validate the actual performance of the presented interleaved boost dc-dc converter, a hardware
prototype was designed and built. Fig. 9 shows the hardware prototype of the interleaved boost dc-dc converter.
Each switch in this interleaved boost dc-dc converter is running at 20 khz switching frequency. In this work, the
prototype have three of main circuit part. The First circuit is the power circuit. The power circuit build using two of
power IGBT HGTG20N60B, two of ultra fast diode 60EPU04P, two of 470mH power inductor and 100 uF
electrolyte capacitor. The second circuit is the gate drive circuit. The HCPL 3120 gate drive IC is choose as the gate
driver in this work. Two of HCPL 3120 IC are used to drive both of Power IGBT. The last but not less is the
controller circuit. The Microchip PIC 16F877A microcontroller is use as the main controller. The PIC 16F877A
have 8 ADC input onchip and two PWM output.