Decentralize Power System
Electric energy is kind of energy should be used immediately, or it must be stored if we want to use it for the future used. In a nutshell, the overall power system that enables you to get electricity access is simply consists of 3 main parts, which are generation, transmission + distribution, and the load (the electricity customer). This electric power was designed so that it will transport the power top down from generation unit, through transmission and distribution networks, and finally ends up to electricity customer, known as centralized system. As the demand for electrical energy will always increase in future, by looking at the mechanism how this electric power arrives at customer side, it is clear that we have to increase the generation unit as well in order to offset the demand.
Today, we have the technology called “distributed generation”. This is basically just generation unit that placed near customer side, and we can call it decentralized system. The concept of distributed generation is to install and operate small electricity generator connected directly to distribution network, with rated power typically less than 10 MW. There are different kind of distributed generation that can be used:
· Fossil Fuel, like diesel and gas engine, fuel cells, these technologies are often used in combined heat
· Renewable Energy, like solar, wind, biomass, micro hydro turbines, or geothermal energy
· Storage System, like batteries, flywheels, and supercapacitor
By using the distributed generation scheme, we try to avoid how the conventional centralized power system works. The power will not need to be transported via long transmission and distribution line, but this power directly can reach the customer using distributed generation scheme. The idea behind this type of generation is that the scheme offered electricity to be delivered to customer with reduced costs and more efficient since we will have lower losses compared to traditional scheme involving transmission and distribution losses.
In order to serve the power to customer, distributed generation must be operated in parallel with the distribution system. Hence, terms interconnection is generally used in order to emphasize that there will be another generation unit that will operate in parallel condition with existing network. As we know, the most widely used power system around the world is AC power system. It means that before a distributed generation scheme can work and injecting power to distribution system, it must be synchronized at first place. This interconnection process called “synchronization” is necessary since when we are talking about AC power system. At least there are 4 parameters that the parallel system must exhibit, or this parallel operation isn’t permitted (it is possible actually, but have the chance to damage the system). These parameters are voltage magnitude, phase angle, phase sequence and the frequency. Thanks to advance of technology, this synchronization process get easier and automated, that make sure all of those 4 parameters are in synchronism, so then this distributed generation can connect and work in parallel with existing distribution system.
Besides synchronism, distributed generation may also have significant effect on power flow, voltage profile, stability phenomenon and harmonics that will experienced both by customer and utility company. Used of renewable energy such solar and wind as source of energy produce intermittent power leading to voltage fluctuations. Distributed generation that utilize grid connected inverter will inject harmonics to existing distribution system leading to power quality problem due to non-sinusoidal currents injected to network. In order to save fuel, fossil fuel based distribution system will have the on-off scheme for economic reason leading to voltage dip.
In this era, especially due to rapid increase in ICT (Information, Communication and Technology), electricity remains one of the basic backbone of all of these things. The distributed generation offers the solution to provide electricity to customer with reduced costs and with more efficient and effective ways. But, there will be several challenges ahead, such interconnection process, stability and power quality problems. In the end, it is our duty to figure out how we can maximize the utilization of distributed generation technology as much as possible and find a way to minimize the negative impact of such technology to existing distribution system.
 “Handbook of Power Quality”, Angelo Baggini