Page 18 - Hybrid-Renewable Energy Systems in Microgrids

Hybrid PV–wind renewable energy sources for microgrid application: an overview 3

This chapter will focus on the study of possible benefits of hybrid renewable
energy system (HRES) (PV–wind), including the optimal sizing of the hybrid system.
In addition, the chapter addresses some of the stability concerns in a HRES-based
MG. A simulation study will be carried out to show the transient stability improve-
ment by using hybrid PV–wind-generator combination in a standalone MG.

2 Hybrid renewable energy system and its benefit

The Sun, as an ultimate source of energy, provides us limitless opportunities to harness
sustainable, cost-free (fuel cost only) and pollution-free energy. However, solar power
does not come without any drawbacks. With the daily solar variation throughout the
year, the solar radiation varies a lot as the sunlight is available during the daytime only,
and low sunlight is available during winter period. Fig. 1.1 shows the solar power out-
put (W) collected from August 2016 to July 2017 at Victoria University, Melbourne,
Australia. It can be seen from Fig. 1.1 that the availability of solar radiation is low in
winter season (June to August in the southern hemisphere). In this case a MG with a
solar-only source will result in higher cost in winter because of the unavailability of
the sunlight. This can seriously impact the sizing of the conventional energy sources
and the storage system capacity if installed.
Similar nonlinear wind power output behavior is visible in the case of wind power
in relation to the hours of the day and throughout the seasons. Nearly similar range of
wind speed pattern is available throughout the year, although daily wind speed maybe
different from one day to another as seen in Fig. 1.2. The actual energy production of
a RES in a given period, that is the capacity factor of wind power, is 20%–40%, and
the PV capacity factor is 12%–15% [6]. However, the aforementioned capacity factors
always vary from location to location. Intermittent pattern of solar irradiation and wind
speed highly affects the power output production of the hybrid system. Therefore the

Figure 1.1 Solar power output (W) at Victoria University, Melbourne.