Impact Of DG On Harmonics

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According to [40], locating DG units to minimize losses is similar to locating capacitor banks to reduce losses. The main difference between both situations is that DG may contribute with active power and reactive power (P and Q). On the other hand, capacitor banks only contribute with reactive power flow (Q). Mainly, generators in the system operate with a power factor range between 0.85 lagging and unity, but the presence of inverters and synchronous generators provides a contribution to reactive power compensation [49].

The optimum location of DG can be obtained using load flow analysis software, which is able to investigate the suitable location of DG within the system in order to reduce the losses. For instance: if feeders have high losses, adding a number of small capacity DGs will show an important positive effect on the losses and have a great benefit to the system. On the other hand, if larger units are added, they must be installed considering the feeder capacity boundaries [3].

3.6.3 Impact of DG on Harmonics
A wave that does not follow a “pure” sinusoidal wave is regarded as harmonically distorted. This is shown in Fig. 2.6.

Harmonics are always present in power systems to some extent. They can be caused by for instance: non-linearity in transformer exciting impedance or loads such as fluorescent lights, AC to DC conversion equipment, variable-speed drives, switch mode power equipment, arc furnaces, and other equipment.

Fig. 3.7 Comparison between pure sinusoidal wave and distorted wave [17]

Harmonic order
Allowed Level Relative to fundamental
(odd harmonics) *
< 11th 4%
< 11th to < 17th 2%
< 17th to 23...

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...Q types. The most commonly used DG model is the PQ model [38]. In this work, the PQ-DG units are represented as a negative PQ load model delivering active and reactive power to a distribution system. The DG reactive power can be calculated by the following equation:

Q_DGi=P_DGi ×tan⁡(cos^(-1) (PF_DGi )) (4.21)

In this chapter emphasis is laid so as how to locate the DG in the distribution system. The main problem here is that the system is already designed therefore we cannot design a new system, a new grid cannot be designed. For this purpose we used optimization techniques which are run in the software of MATLAB version 2012a. In this software we made a coding and we simulate the program to get result.

Figure 4.1 Methodology to solve the problem
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