Page 307 - Advances in Renewable Energies and Power Technologies

280 CHAPTER 8 Hybrid PV/Batteries Bank/Diesel Generator

Bus DC Bus AC

Load
DC/DC

Photovoltaic Panel
DC/AC
Batteries DC/DC
Diesel
Generator

Control System
FIGURE 8.18
Hybrid PV/batteries bank/diesel generator renewable energy system block diagram.

4.2.1 Batteries Bank Depth of Discharge Control
Lead-acid batteries are used in the hybrid renewable energy system to store electrical
power. Typically, batteries maximum dod value is set to 80% to protect batteries from
over discharging, which affect the batteries lifetime. On the other hand, the minimum
dod value at which the DG is turned OFF needs to be adjusted to achieve the best
cost/pollution results [7]. Thus, the dod value must be in the range defined as:

dod min < dod < dod max (8.29)
The battery dod value is computed using Eq. (8.6).

4.2.2 AC Load Prediction
The load used in this management scheme represents a typical house in Tunisia as
described in Section 3. The required load power can be supplied during the night by
the DG through the AC bus or by the batteries storage bank through a DC/AC
inverter as shown in Fig. 8.18. An autoregressive moving average (ARMA) scheme
associated with a Kalman filter is adopted in this management process to forecast the
load every 2 min ahead of the actual load value. During the day, the actual measured
load at each 2 min are used as input to the ARMA algorithm. The obtained modeled
values and actual load values are used in Kalman filter to predict the load every
2 min ahead of operation. Fig. 8.19 describes the steps of the ARMA prediction
algorithm.

4.2.3 Energy Management Process
PSO algorithm is used for sizing the investigated hybrid renewable energy system as
described above [9]. The achieved optimal system sizing for minimum overall sys-
tem cost and emitted pollution corresponds to 10 batteries with total capacity of