Microcontroller Based Sinusoidal PWM Inverter for
Photovoltaic Application
S. M. Mohaiminul Islam, Gazi Mohammad Sharif
School of Engineering and Computer Science, Independent University, Bangladesh.
e-mail: safimohammadm@gmail.com
Abstract: This paper represents the microcontroller based
sinusoidal PWM inverter for photovoltaic application. The
advantage of this inverter is the use of a low cost
microcontroller that has built in PWM modules.
Microcontroller PIC 18F4431 is able to store the required
commands to generate the necessary PWM waveforms. The
required dead time has been implemented low cost. The
application of this inverter is to be either for stand-alone or
for grid connected from a direct supply of photovoltaic (PV)
Cells. In this paper how SPWM signal is generated by
microcontroller and what are the features of described
microcontroller is reviewed. Subsequently hardware
configuration of the microcontroller, algorithm, flowchart,
gate driver and isolation system are discussed. Finally the
experimental results are shown in this paper.
1. Introduction
Sinusoidal pulse width modulation (SPWM) is widely
used in power electronics to digitize the power so that a
sequence of voltage pulses can be generated by the on and
off of the power switches. The pulse width modulation
inverter has been the main choice in power electronic for
decades, because of its circuit simplicity and rugged
control scheme. SPWM switching technique is commonly
used in industrial applications or solar electric vehicle
applications [1]. SPWM techniques are characterized by
constant amplitude pulses with different duty cycle for
each period. The width of this pulses are modulated to
obtain inverter output voltage control and to reduce its
harmonic content. Sinusoidal pulse width modulation is
the mostly used method in motor control and inverter
application [1, 2, 4]. To generate this signal, triangular
wave is used as a carrier signal is compared with
sinusoidal wave, whose frequency is the desired
frequency.
The proposed alternative approach is to replace the
conventional method with the use of microcontroller. The
use of PIC18F4431 microcontroller brings the flexibility
to change the real-time control algorithms without further
changes in hardware. It is also low cost and has a small
size of control circuit for the single phase full bridge
inverter. The microcontroller has the built in dead time
control circuit [3].
2. System overview
The basic schematic diagram of the photovoltaic inverter
is shown in Fig. 1. It consists of many blocks, emphasis is
given only on Sinusoidal PWM generation.
Fig. 1 Block diagram of the inverter [5]
The single phase full bridge inverter circuit is shown in
Fig. 2.
Fig. 2 Single phase full bridge inverter circuit [5]
The heart of the system is a PIC Microcontroller. This
microcontroller is specially developed for the generation
of Sinusoidal PWM (SPWM) with dead time controller.
The dead time controller circuit is useful to make the
design simpler, more reliable and the most important thing
is to reduce the cost and components. The Microcontroller:
PIC18F4431generates four Sinusoidal PWM signals. Fig.
3 shows the pin diagram of PIC18F4431 connected with
external oscillator. RB0 to RB3 pins are output for
Sinusoidal PWM signals. RB0 and RB2 pins are
independent which go to gate driver ICs. The name of the
IC is IR2110. RB1 and RB3 pins are complementary
which go to another same gate driver IC. The output
voltage of the gate driver IC is 10V - 20V. The output