Power-Management
Strategies for a Grid-Connected PV-FC Hybrid System
ABSTRACT:
This paper presents a method to operate a grid connected
hybrid system. The hybrid system composed of a Photovoltaic (PV) array and a
Proton exchange membrane fuel cell (PEMFC) is considered. The PV array normally
uses a maximum power point tracking (MPPT) technique to continuously deliver the
highest power to the load when variations in irradiation and temperature occur,
which make it become an uncontrollable source. In coordination with PEMFC, the
hybrid system output power becomes controllable. Two operation modes, the
unit-power control (UPC) mode and the feeder-flow control (FFC) mode, can be
applied to the hybrid system. The coordination of two control modes, the
coordination of the PV array and the PEMFC in the hybrid system, and the
determination of reference parameters are presented. The proposed operating
strategy with a flexible operation mode change always operates the PV array at
maximum output power and the PEMFC in its high efficiency performance band,
thus improving the performance of system operation, enhancing system stability,
and decreasing the number of operating mode changes.
KEYWORDS:
1. Distributed generation
2. Fuel cell
3. Mybrid system
4. Microgrid
5. Photovoltaic
6. Power management.
SOFTWARE: MATLAB/SIMULINK
BLOCK
DIAGRAM:
Fig.
1. Grid-connected PV-FC hybrid system
CONCLUSION:
This
paper has presented an available method to operate a hybrid grid-connected
system. The hybrid system, composed of a PV array and PEMFC, was considered.
The operating strategy of the system is based on the UPC mode and FFC mode. The
purposes of the proposed operating strategy presented in this paper are to
determine the control mode, to minimize the number of mode changes, to operate
PV at the maximum power point, and to operate the FC output in its
high-efficiency performance band. The main operating strategy, shown in Fig. 7,
is to specify the control mode; the algorithm shown in Fig. 4 is to determine in
the UPC mode.With the operating algorithm, PV always operates at maximum output
power, PEMFC operates within the high-efficiency range , and feeder power flow
is always less than its maximum value . The change of
the
operating mode depends on the current load demand, the PV output, and the
constraints of PEMFC and feeder power. With the proposed operating algorithm,
the system works flexibly, exploiting maximum solar energy; PEMFC works within
a high-efficiency band and, hence, improves the performance of the system’s
operation.
The system can maximize the generated power when
load is heavy and minimizes the load shedding area. When load is light, the UPC
mode is selected and, thus, the hybrid source works more stably. The changes in
operating mode only occur when the load demand is at the boundary of mode
change ; otherwise, the operating mode is either UPC mode or FFC mode. Besides,
the variation of hybrid source reference power is eliminated by means of
hysteresis. In addition, the number of mode changes is reduced. As a
consequence, the system works more stably due to the minimization of mode
changes and reference value variation. In brief, the proposed operating
algorithm is a simplified and flexible method to operate a hybrid source in a
grid-connected microgrid. It can improve the performance of the system’s
operation; the system works more stably while maximizing the PV output power.
For
further research, the operating algorithm, taking the operation of the battery
into account to enhance operation performance of the system, will be
considered. Moreover, the application of the operating algorithm to a microgrid
with multiple feeders and DGs will also be studied in detail.
REFERENCES:
[1]
T. Bocklisch, W. Schufft, and S. Bocklisch, “Predictive and optimizing energy
management of photovoltaic fuel cell hybrid systems with shorttime energy
storage,” in Proc. 4th Eur. Conf. PV-Hybrid and Mini- Grid, 2008,
pp. 8–15.
[2]
J. Larmine and A. Dicks, Fuel Cell Systems Explained. New York: Wiley,
2003.
[3]
W. Xiao, W. Dunford, and A. Capel, “A novel modeling method for photovoltaic
cells,” in Proc. IEEE 35th Annu. Power Electronics Specialists Conf.,
Jun. 2004, vol. 3, pp. 1950–1956.
[4]
D. Sera, R. Teodorescu, and P. Rodriguez, “PV panel model based on datasheet
values,” in Proc. IEEE Int. Symp. Industrial Electronics, Jun. 4–7,
2007, pp. 2392–2396.
[5]
C. Wang, M. H. Nehrir, and S. R. Shaw, “Dynamic models and model validation for
PEM fuel cells using electrical circuits,” IEEE Trans. Energy
Convers., vol. 20, no. 2, pp. 442–451, Jun. 2005.
