15-06-2012, 11:28 AM
Development of a Microcontroller-Based Boost Converter for
Photovoltaic System
Development of a Microcontroller.pdf (Size: 338.78 KB / Downloads: 64)
Introduction
In recent years, attention towards renewable energy such as wind and solar power has increased
dramatically. As more people are concerned with the power generation using fossil fuel which brings
environmental problems, societies and conferences are being held to find solutions to slow down the
world climate change caused by power generation.
Photovoltaic (PV) sources are used today in many applications such as satellite power systems,
battery charging, home appliances and many more. PV is becoming more famous in the world of
power generation because they have the advantages of free pollution, low maintenance, and no noise
and wear due to the absence of moving parts.
Boost Converter Analysis
A simple boost converter consists of an inductor, a switch, a diode, and a capacitor as shown in Figure
4 (Wu et al., 1998). Boost converter circuit can be divided into two modes. Mode 1 begins when the
switch SW is turned on at t = Ton as shown in Figure 5. The input current which rises flows through
inductor L and switch SW. During this mode, energy is stored in the inductor. Mode 2 begins when the
switch is turned off at t = Toff. The current that was flowing through the switch would now flow
through inductor L, diode D, capacitor C, and load R as shown in Figure 6. The inductor current falls
until the switch is turned on again in the next cycle. Energy stored in the inductor is then transferred to
the load. Therefore, the output voltage is greater than the input voltage and is expressed as (Mohan et
al., 2003)
Control Approach
A simple control technique is proposed in this paper. It uses voltage-feedback control technique where
the output voltage of the boost converter is tracked continuously and compared with a reference
voltage. The voltage difference is then used as a parameter for the microcontroller to produce a PWM
signal with a set of duty cycle. PWM signal is used to control the switch SW in the boost converter.
Figure 8 shows the flow chart of the voltage-feedback control technique whereas Figure 9 shows the
tracking process of the desired constant output voltage. With this control technique, any changes of the
solar panel voltage will produce a constant output voltage at the end of the converter.
Proposed System
As mentioned earlier, the proposed boost converter is implemented in between a solar panel and load
as shown in Figure 10. This system is able to deliver power with a constant output voltage of 24V
without storage elements such as battery. Therefore, the converter is small and light weight. In addition
to that, the system is able to attach directly to the solar panel as a single unit.
Experimental Results
Experimental measurements are being carried out in order to verify the performance of the boost
converter proposed in this paper. A power supply representing solar panels is connected to Vin and a
load resistance is connected to Vout as shown in Figure 10. Figure 13 shows the experimental results.