**9. Conclusion**

62 Modeling and Optimization of Renewable Energy Systems

C.B Status for DG1

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 .

C.B status for DG4 and DG5

C.B DG4 C.B DG5

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 .

. .

> . .

. .

(b) (a)

Fig. 5. Fault occurs in DG1. (a) DG1 C.B status. (b) Other DG's and zones C.B status.

. .

(b) (a) Fig. 6. Fault occurs in zone 4. (a) DG4 and DG5 C.B status. (b) Reclosing on zone4 C.B.

In the proposed method, only the faulted zone and DG's in that zone are disconnected from network and therefore the other zones can continue their normal operation. In order that the faulted zone returns to network as soon as possible, it must been detected precisely so that the fault could be cleared from the zone. Figure 7 shows the adaptive relay operation in

Finally, adaptive relay operation in case of transient fault in system has been investigated. The fault duration is considered in three cases so that we can study the adaptive relay operation at three stages of reclosing. In this simulation, first stage of reclosing is done 0.4 s after the fault occurrence, second stage of reclosing in done 0.8 s after the first reclosing and

Fault Location

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

The fault location is in bus 32 in zone 3, fault duration is 0.3 s, time to apply fault is t=2 s. As it seen in figure 8, adaptive relay sends the trip command to zone 3 and DG3 circuit breakers. After 0.4 s, a reclosing operation is done on zone 3 circuit breaker. As the fault duration is 0.3 s, after the first reclosing, adaptive relay doesn't sense the short circuit



Status

C.B DG1

Status

C.B status for DG's and zones

C.B Zone1 C.B Zone2 C.B Zone3 C.B Zone4 C.B DG2 C.B DG3 C.B DG4 C.B DG5

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 .

C.B status for Zone 4

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 5.50 6.00 .

third stage of reclosing in done 1.2 s after the second reclosing.

Faulted Bus

Fig. 7. Fault location determination in case of permanent fault

41

Bus Number

precise fault location determination.


C.B zone4


Status

Status

Distributed generations have possible characteristics for system operation enhancement. Using DG's in distribution systems has many benefits such as system reliability improvement, power loss reduction, development costs decrease, power quality

**4** 

*Iran* 

**Exergoeconomic Analysis and Optimization of** 

*Mechanical Engineering School, Mechanical Engineering School, Shiraz University,* 

There is a growing demand for electricity in the developing countries. The conventional approaches to meet this need are through the construction of fossil-fuel power plants. The operation of these plants, however, releases carbon dioxide and contributes to the problem of climate change. Furthermore, many of these countries rely on imports for their energy needs and the purchase of fossil fuel weakens their financial potential. Unlike hydrocarbon energies, renewable energy can be developed from resources which are constantly

 Solar Power which utilizes the energy from sunlight either indirectly or directly. It can be used for heating and cooling, generating electricity, lighting, water desalination, and

 Biomass Energy which uses the energy from plants and plant-derived materials, such as wood, food crops, grassy and woody plants, residues from agriculture or forestry, and

Geothermal Energy which utilizes the heat from the earth, drawn from hot water or

Ocean Energy which traps thermal energy from the sun's heat and mechanical energy

Hydropower which captures the energy from flowing water to power machinery and

Many developing countries have an abundance of a natural energy source: solar radiation. Operation of solar thermal power plants (STPP) would reduce their reliance on fossil fuels. Regions that could make use of these systems include Southern Africa, Middle East and North Africa (MENA) India, Northern Mexico and parts of South America. The developed

In this chapter attempt is made to have a brief introduction of solar thermal power plant (STPP) systems and cycles. To develop new approaches to exergoeconomic analysis of such plants, the main elements of exergy and economic analysis are explained. Various methods of optimization from single objective to multi objectives applicable to STPP are developed. Finally application of the developed optimization methods for a sample integrated solar

Wind Power which captures the energy of the wind through wind turbines.

steam reservoirs in the earth's mantle located near the earth's surface.

regions of Southwest U.S. and Australia could also benefit from this technology.

the organic component of municipal and industrial wastes.

replenished and will never run out. These energies include:

many other commercial and industrial uses.

from the tides, underwater currents and waves.

produce electricity

**1. Introduction** 

**Solar Thermal Power Plants** 

Ali Baghernejad and Mahmood Yaghoubi

improvement and load peak clipping. Also using DG's in systems has disadvantages such as interaction with protective systems, voltage control problems and DG islanding.

While a DG is inserted in distribution system, some parts of system lose their radial characteristics and protective devices coordination is lost. If the influence of DG be intensive, then coordination of protective devices with usual method is impossible. The proposed adaptive protection scheme does short circuit analysis online and whenever system configuration varies, this analysis execution is done and a look up table is conformed. The adaptive scheme diagnoses fault location, faulted bus and faulted zone by the discussed method.

If the fault is permanent, adaptive relay disconnected only the faulted zone and DG's in that zone and other zones continue their normal operation. If the fault is transient, adaptive relay sends trip command to faulted zone and its DG's circuit breakers and then does a reclosing operation in three time stage. If the fault be cleared in each stage, relay sends close command to zone circuit breaker and sends close command to DG circuit breaker after 2 s or 3 s for synchronization operation. Adaptive relay disconnects DG's in faulted zone wether the fault is permanent or transient.

#### **10. References**

