Abstract
The electricity demand, fossil fuel depletion and environment issues increase the interest of power engineers to integrate small power generations i.e. called distributed generation (DGs) in the distribution system. The DG in distribution system has many positive effects such as it reduces the system power losses, improves the voltage profile and strengthen the voltage stability etc. The placement and sizing of DG play a major role in optimizing these parameters. Therefore, this chapter proposes a modified Particle Swarm Optimization (PSO) algorithm for finding the optimal placement and sizing of distributed generation in the radial distribution system. Two types of DGs such as an active power and reactive power DGs are tested on standard IEEE 33 radial bus system. Moreover, it can be realized that proposed method gives very effective results when both of active and reactive power DGs are integrated into the distribution system.
TopIntroduction
The urbanization, population growth, exhausting of fossil fuels and limitations on the congested transmission lines have pushed the power system to utilized the distributed generations into the distribution system. The distributed generation are a small source of power generation connected near to the load centers. The DGs are also called as a de-centralized generation, embedded generation or dispersed generation. From extensive literature survey (Paliwal, Patidar, & Nema, 2014) it can be summarized that distributed generation has generally been defined on the basis of placement, capacity and type of primary resource. According to (CIRED, 2009) DG is power generation source which is not centrally planned nor centrally dispatched, usually ranging from less than 50-100MW which is connected to the distribution system. Distributed generation is an electric power source which is directly connected to the distribution system or on the customer site of the meter (Ackermann, Andersson, & Söder, 2001). Small generating units usually 30MW or less that are connected at or near customer site to support customer and grid by the economic operation (Chambers, 2001). DG is a small source which may be electric power generation or storage ranging typically from less than few kW to 10 of MW that is not part of the central power source and is connected close to load (Dondi, Bayoumi, Haederli, Julian, & Suter, 2002). Power generating unit which is connected to a distribution network that produces power and supply locally within the network (IEA, 2002). DG refers to a system that generates electricity (and possibly heat), generally takes place close to the point where energy is actually used (Rob van Gerwent, 2006). IEEE defines the generation of electricity by facilities that are smaller than central generating plants so as to allow to interconnect at nearly any point in a power system (Pepermans, Driesen, Haeseldonckx, Belmans, & D’haeseleer, 2005). The EPRI defines DG as generation from few kilowatts up to 50MW, located at the customer site or within utility distribution grid (Electric Power Research Institute EPRI, 1998). The distributed generations are the small amount of power generation sources, which are connected directly to the distribution systems or on the site of the customer (Ackermann et al., 2001).
From last few years, many countries are taking a keen interest in their legislations for renewable and non-renewable DGs, which are most efficient technically, economically and environmentally. Technically, DGs are benefiting many electric parameters like, it reduces system power losses, improves the system voltage performance, strengthen the voltage stability, reduces the transmission capacity and provides the good service quality to the consumer appliances. Economically, it has opened a new energy marketplace for competitors and investors. DG provides an alternatives fuel sources such as renewable and non-renewable energy which further helps in reduction of peak electricity needs and it also defers the transmission lines upgradation cost. Environmentally, DGs can be operated by many of primary fuels sources, which are environments friendly such as the wind, solar, micro turbine, and fuel cell etc. The power generation from these sources are less pollutant to the environment, which ultimately reduces carbon foot prints, alleviates the global warming and provides the public awareness to promote renewable energies (Georgilakis & Hatziargyriou, 2013; Paliwal et al., 2014; Tan, Hassan, Majid, & Abdul Rahman, 2013; Viral & Khatod, 2012).
Key Terms in this Chapter
Voltage Stability: Voltage stability is referred as the ability of power system to maintain the steady voltage across all nodes of the power system, after being subject to disturbances from its initial points. Voltage stability can be observed in transmission as well as in distribution system. It actually assures the electric operator that a required electric power is being drawn to meet the load requirement. The main causes of voltage instability are increasing power demand, which reduces the voltage profile and reactive power requirement, which eventually causes the voltage stability.
Power Losses in Distribution System: There are two types of electric power losses in the distribution system. Active power losses or I2*R losses, as distribution system has radial nature, having high resistance to reactance ratio so more active power losses are observed in the distribution system. The other losses are reactive power losses or I2*X, which comes from inductive loads.
Distributed Generation Applications: Distributed generation can be used for many tasks, like DG can help to improve distribution system performance. (I.e. it can reduce system's power losses, improves voltage profile and voltage stability etc.). DG in the distribution system can be used to help in peak hours for extra energy supplies. DG in the distribution system can help to reduce transmission lines burden, or it can be the main focus to make the electric system efficient by utilizing renewable energy locally, which eventually reduces greenhouse gas emissions.
Greenhouse Gas: The greenhouse gas is generally made of any gaseous compound in the atmosphere, which could be capable of absorbing the IR radiations and results in it into heat. The greenhouse gases are the main cause of global warming. According to Environmental Protection Agency (EPA), carbon dioxides, water vapor, methane and nitrous oxides gases are the main contributor to global warming. Among the other different sources of greenhouse gases production, the production of the electric power industry is also the main source of GHG emissions. It utilizes the fossil fuel i.e. coal, oil and gas for power production. According to Environmental Protection Agency (EPA) report thirteen percent of nitrogen oxides, Forty percent of carbon di oxides and 70 percent of sulfur dioxides are emitted in the US.
Distributed Generation Technologies: The power generation in case of DG can be either renewable (like wind, solar, micro hydro or tidal etc.) or non-renewable energies (like fossil fuel based gas generators, diesel generators, small steam turbines). An active source of power, like a photovoltaic cell, fuel cell or combine heat and power etc. A reactive source of power, like capacitor banks or synchronous condensers, or STATCOM (static synchronous compensator), active-reactive power sources like synchronous machines and wind turbine generators.
Particle Swarm Optimization: PSO is an attractive stochastic optimization technique inspired by social behavior of living being such as birds flocking or fish schooling, introduced by Dr. Kennedy and Dr. Eberhart in 1995. The PSO algorithm is that population called swarm and consists of individuals called particles. The swarm is randomly generated in which particle changes their position (states) with time. In PSO each particle is moving in a multidimensional search space to adjust its position according to its own experience with the best solution it has achieved so for called pbest and the position tracked by its neighboring particle called lbest . When a particle takes all the swarm as its neighbors the best value (global best) will be called as gbest . The particle swarm optimization concept consists of, at each time step, changing the velocity of (accelerating) each particle toward its pbest and lbest locations (local version of PSO).
Distributed Generation: Distributed generation (DG) is also called as dispersed generation or dispersed power generation or de-regulated power generation or distributed power resources or small to medium scale power generation, which is installed near to consumer loads. DG is a small source which may be electric power generation or storage ranging typically from less than few kW to 10 of MW that is not part of the central power source and is connected close to load. Power generating unit which is connected to a distribution network that produces power and supply locally within the network. DG refers to a system that generates electricity (and possibly heat), generally takes place close to the point where energy is actually used. IEEE defines the generation of electricity by facilities that are smaller than central generating plants so as to allow to interconnect at nearly any point in a power system.
Electric Demand: Electric demand is the need of power for electric loads. Electric loads may resistive, inductive, capacitive or combinations of these. Its units are in kW or in KVAr.