An Improved MPPT Converter Using Current Compensation Method
for Small Scaled PV-Applications
Abstract-
An improved MPPT converter with current
compensation method for small-scaled PV-applications is
presented in this paper. The proposed method implements
maximum power point tracking (MPPT) by variable
reference current which is continuously changed during
one sampling period. Therefore, the proposed MPPT
converter with current compensation method increases
the power transferred to the load above 9%. As a result,
the utilization efficiency of Photovoltaic (PV)-module can
be increased. In addition, as it doesn’t use digital signal
processor (DSP), this MPPT method has the merits of
both a cost efficiency and a simple control circuit design.
Therefore, it is considered that the proposed MPPT
method is proper to low power, low cost PV-applications.
The concept and control principles of this improved
MPPT method are explained in detail and the validity of
the proposed method is verified through several simulated
results.
Keywords: Current compensation method, maximum
power point tracking (MPPT), photovoltaic module, digital
signal processor (DSP), utilization efficiency
Ⅰ . INTRODUCTION
Recently, as the fossil fuel exhaustion and environmental
pollution are aggravated, the concern of the development of
alternative energy systems, which are renewable and
pollution free, has been increased continuously. Among them,
the photovoltaic (PV) power generation systems stand out as
an important solution because they produce electric power
without inducing environmental pollution, by directly
transforming solar irradiation into electricity. Although PVcell
was expensive at the beginning, it is considered that PVpower
systems can compete with the fossil fuel systems due
to the development of the semiconductor technology and
manufacturing process. Under changing atmospheric
conditions, the output characteristics of PV-module are varied
nonlinearly. So, to effectively use PV-module, the PV-power
system has to track the maximum power point (MPP) of PVmodule
under changing atmospheric conditions. Thereby,
many researchers and designers have actively done
researches to track MPP of PV-module [1]-[10].
Among them, typical MPPT methods can be largely
classified into two groups such as the large scaled PV-power
systems based on digital signal processor (DSP) [1]-[6] and
the small-scaled PV-power systems without using DSP [7]-
[10].
MPPT systems based on DSP include the hill-climbing
methods [1]- [5] and the MPPT method using short circuit
current of PV-module [6]. Between the hill-climbing methods,
P&O method tracks MPP of PV-module by repeatedly
increasing or decreasing the output voltage at MPP of PVmodule.
This method not only has relatively simple control
algorithm but also tracks MPP of PV-module well. However,
when atmospheric conditions are constant or slowly changed,
P&O method is oscillated close to MPP. Especially, when
those are rapidly changed, this method fails to track MPP.
The incremental conductance method developed to improve
these problems of P&O method tracks MPP of PV-module by
comparing incremental conductance with instantaneous one.
As a result, under rapidly changing atmospheric conditions,
this method tracks MPP very well, but the response speed of
finding MPP is declined because the calculation time of DSP
is increased by relatively complicated control algorithm.
On the contrary, the MPP tracking method using short
circuit current of PV-module uses the fact that the operating
current at MPP of PV-module is linearly proportional to short
circuit current of PV-module [6]. Then, under rapidly
changing atmospheric condition, this method has the fast
response speed of tracking MPP, but the control circuit is
complicated and the conduction loss and the cost of MPPT
converter is increased due to added switch and diode to
sample the short circuit current of PV-module.
Although the MPPT methods based on DSP, above
mentioned, are applicable to above 1KW large scaled PVsystems,
to use DSP loses cost efficiency in 50-150W smallscaled
PV-applications. Therefore, the MPPT methods
without using DSP in small-scaled PV-system have been
many developed [7]-[10].
Among them, the MPPT method using open circuit
voltage of PV-module [10] uses the fact that the operating
voltage at MPP of PV-module is near linearly proportional to
open circuit voltage at MPP of PV-module. This method has a
cost efficiency as well as a very simple control circuit
because it does not use the DSP. However, in this method, the
reference voltage is not changed until the next sampling
occurs. As a result, this method always occurs the
considerable error power because the output voltage of PVmodule
only follows the unchanged reference voltage during
one sampling period.

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