Multi agent system based voltage regulation for electrical distribution system

Technological developments and the increase in the human population are increasing the need for energy day by day. Due to the ever-increasing need for energy, work on energy power plants has also become more frequent. As a result of the efforts to meet energy needs from different sources, the structure of the electricity networks is undergoing change. While the energy need only available from centralized generation facilities with large-scale installed capacities connected to the transmission system, in recent years small scale distributed generations have contributed considerably to meet the energy need. Renewable energy or fossil fuel-based distributed productions can be connected almost anywhere in the distribution network. Distributed productions become more popular in Turkey as it is in the world. Electrical networks that are not designed for generation integrations made from distribution levels and bidirectional energy flows at the installation stage may cause some problems with distributed generation integrations. Distributed generation integration reveals the issues that need to be addressed, such as the increase in short-circuit currents in the network, the risk of islanding, and irregularities in steady-state voltages. The integration of distributed production into the network has become an area that needs to be examined in detail within the criteria specified in international standards and local regulations. This thesis has been specifically introduced to the traditional and modern equipment used to prevent voltage violations in the distribution system such as on load tap changer (OLTC), shunt capacitor, shunt reactor, step voltage regulator, static VAR compensators, synchronous compensator, static synchronous compensator. In order to remove the voltage violations originating from distributed generation, multi-agent system (MAS) based voltage regulation method studied in detail. MAS based technology found a place at power engineering in recent years. MAS is used in power engineering four different area such as distributed control, modelling and simulation, monitoring and diagnostics, protection. Researches show that MAS technology can be an effective way to make dynamic operations in future distribution network. Voltage control equipment is used to keep the voltage level within the permissible limits in the distribution system. In addition, modern distributed generations have the ability to inject or absorb reactive power into the system in a controlled way from the point where they are connected to the network due to the nature. Most of the distributed generation connected to the grid trough power electronic converters. Distributed generation can provide reactive power to the grid by means of converter structure. For wind turbines with this structure can provide maximum reactive power even under the lowest wind speed condition or maximum generation. The connection of distributed generation can affect the voltage level. For this reason, making the voltage regulation in the distribution systems a phenomenon that can be realized by the coordinated operation of many factors. As a result of the literature studies, the autonomous control technique that aiming voltage regulation with an algorithm based on multi-agent system architecture is modelled on the Simulink interface of Matlab software. In addition, the test system modelled as a radial medium voltage network on Simulink. In the modelled system, there are four wind power plants, loads, step-up/down transformers, OLTC, shunt capacitor, overhead lines and underground cables. Wind turbine which was modeled in wind power plant was chosen doubly fed induction generator based (DFIG) one. DFIG type of wind turbine has wound rotor induction generator and AC/DC/AC converter installed between rotor windings and grid. Active and reactive power generation of DFIG wind turbines can be controlled. In order to disturb the steady-state voltage some changes made in the system the effects of the voltage regulation with the multi-agent system were observed. Simulation studies have been carried out for three different cases with the effect of changing the generation amount of the distributed generation with different wind speeds, the failure of the power plants due to faults or trip due to excessive wind speed. In the first case, due to the change of the wind speed from 8 m/s to 25 m/s, causes trip at all wind farms to protect mechanical equipment. Under this circumstances undervoltage issue observed. Load agent of related bus detects this violation and regulates voltage by switching on shunt capacitor. In the same case also the demand load rise effects simulated. In this situation voltage regulation made by OLTC operation. Second case simulated to observe voltage regulation by distributed generation reactive power support capabilities. In this case one of the wind farm trips and load demands of the system increase. Load agent of MAS detects undervoltage problem and sends message the related reactive power control agent to regulate voltage. System voltages are brought to permissible range by wind turbines reactive power support. At the last case, voltage rise reaction of the MAS simulated. The wind speed changes from 8 m/s to 12 m/s. As expected, this is also increases active power generation of wind farms. At the same time demand load of the system decreases. As seen in the case 2 distributed generation can regulate voltage with reactive power support capability. In case 3, after the violation detection load agent sends message to the related agent to reduce voltage, unlike the case 2. Voltage regulate by absorbing reactive power from the network at the connection point of wind farm. Simulation studies show that changes in the wind power plant generation values and demand load quantities in the network can increase or decrease bus voltages. In cases where the voltage exceeded the limit values, the multi-agent system could perceive the violation due to the load agents and successfully regulate the voltage to the permissible value range by communicating with the related agents. In this respect, the system voltages kept within the limits specified in the regulations, and the equipment in the system was prevent from being damaged or disabled due to voltage violations. Shunt capacitors, on load tap changers and reactive power capabilities of wind power plants, which are included in the test system during the regulation of the voltage, have been utilized. Voltage control equipment is operated in a coordinated manner and minimizing these equipment switching operations.