Circulating MVAR control in Rajasthan (India) transmission system

In a large scale power network, maintaining the magnitude of bus voltages within nominal operating level at all buses is a vital requirement. With such condition, the system will have an optimal transmission line performance with minimum power losses and no overloading issue. To achieve this, the power flow along transmission line ought to be properly controlled using special devices like the Unified Power Flow Controller (UPFC) - a multipurpose device which can control power flow by modifying the voltage magnitude, phase angle and impedance of transmission lines. Hence, this paper proposes a technique for mitigating voltage level and real power losses in transmission system using optimal placement of UPFC and Evolutionary Programming (EP). The implementation of the proposed technique involved IEEE 14-bus reliability test system. Experiment and analysis has justified the capability of EP-based UPFC placement for voltage stability improvement and power loss minimization as well.

Increased penetration of distributed generation in power distribution network influences voltage profile in power distribution network. As voltage is a local phenomenon, active power injection from DERs only effects voltage of buses in dose proximity. The voltage regulation problem can be solved effectively by dividing network into voltage control areas with high voltage interdependency. This paper proposes zones for voltage control through optimal reactive power dispatch for distributed generation to regulate voltage in the network. Zones were identified by using hierarchical agglomerative dustering algorithm based on voltage sensitivities to reactive power. A meta-heuristic algorithm was used for optimally determining the reactive power dispatch set points for distributed generators m each zone. Modified IEEE 37 node MV test network with distributed generation was used to evaluate the proposed voltage control scheme by using a co-simulation platform. Results showed that zone based reactive power dispatch is effective for improving voltage profile in the network.

In today's deregulated environment, there is a rapid increase in the load demand of any power system. The existing transmission network is incapable of supplying such a huge power demand. This results in voltage instability, poor voltage profile, increased system losses, system insecurity, disturbance and unreliability of the power system. The distribution network should be properly designed to enhance the system stability and loss reduction. In recent years, the power sector has experienced changes in distribution systems because of the increment in the usage of Flexible AC Transmission Systems (FACTS) and Distributed Generation (DG). By using DSTATCOM, SVC, etc. the system voltages, losses, power flow and stability are affected. Similarly with the use of DG. In this paper, an IEEE 33 bus radial distribution network has been taken into consideration. The weak buses are identified by use of stability index, namely Fast Voltage Stability Index (FVSI). The performance of the network has been assessed by optimal placement of DG & DSTATCOM in the weak area/zone. The criterion for performance assessment are Line Loss Reduction and Voltage Profile Improvement. Again a detailed comparative analysis is done between devices DG & DSTATCOM in terms of technical parameters such as enhancement in voltage profile & decrement of line losses. Further the analysis of the system is done by integration of both DG & DSTATCOM over a single bus and the results are examined and compared The working environment has been created in MIPOWER 9.0.1 and analyzed.

In large-scale power system grids, one of the most common problems is the reduced potential of the power transmission network related to voltage drop issues due to the distance between generation and loads. This paper presents an approach to analyse and overcome the voltage-profile challenges. The investigated case study of this research is the eastern region of the Libyan power system that mainly incorporates two transmission lines (dual circuits) at 220 kV level in addition to a 400 kV transmission line connecting the eastern region with the other parts of the system. In the "Green Mountain" area, the lines are more than 200 km long with no nearby power stations in this area. The Eastern Libyan power network was studied using MATLAB software. The analysis has shown that the voltages in this area are at unacceptable values (below 0.95 p.u.), as a result, the energy transported through the transmission lines are affected, which causes load shedding at peak times, especially in the winter season. In this paper, optimal placement, and sizing of static VAR Compensator in different locations are carried out with the utilization of Particle Swarm Optimization (PSO) technique. MATLAB simulation results showed a significant improvement in voltage profile with minimized cost and real power losses that were used as constraints in the optimization.

The voltage profile in the distribution network is very important so that the power system is reliable and delivered with good quality. If the voltage profile in the power system does not meet the applicable standards, this will cause poor quality and continuity of the distribution network. If not resolved quickly, this can result in system failure. One of the causes of a poor voltage profile in a system is too long distribution lines. Long distribution networks can also cause large capacitance in the lines with air as the medium. With the capacitance in the line, reactive current will flow along the line and cause a drop in voltage and power losses in the system. In this paper, we will discuss improving the voltage profile on distribution lines that have end voltages that do not comply with PLN standards by planning the construction of a new 20 kV distribution line from the substation and installing capacitors as reactive power compensators in the system. These repair options will be compared by considering the profile of the system, savings, and financial feasibility when the repair options are implemented.

Wavelet based feature extraction of voltage profile for online voltage stability assessment using RBF neural network

As the cost of photovoltaic (PV) generation systems reduces, more consumers will add grid-tied roof-top PV systems to low-voltage (LV) distribution networks in a widespread manner. Transmission-line impedance and load variations will influence the power transfer capability and voltage profile of the system. This chapter describes the influence of line impedance and load change on the voltage profile in the distribution network. An analysis on the voltage profile due to the variation of load change and line impedance is investigated in a representative LV distribution network and a new control strategy-based on Artificial Neural Network (ANN) is introduced for mitigating the voltage-rise issue in the system. The system is simulated using a MATLAB/SIMULINK platform.

Distribution Electric power system is the largest and the most complex system made by the mankind. The distribution network power system is being encountered by quickly rising load demand and it is detected that under certain critical loading circumstances, the distribution system poses maximum power losses and poor voltage profile and collapse in convinced areas. To overcome these problems integrating distributed generation (DGs) on the grid near to the load center is the better solution as compared to others. Though, for the DG to serve its purpose, its location and size have to be determined optimally. In this paper, Grid-Based Multi-Objective Harmony Search Algorithm (GrMHSA) has been utilized to determine the size and location of DG in the distribution system in Debre Markos town. By placing DG optimally, in addition to the reduction of the power loss in the distribution network, the proposed mechanism improves the node (bus) voltage profile of the system under consideration. A MATLAB program is developed to mitigate power losses and improve the voltage profile by optimally sizing and placing a DG in the distribution network. After sizing and placing the DG in the network, the total voltage deviation, active and reactive power losses are reduced by 93.42%, 81.63% and 82.45% for Debre Markos Feeder 3 and 85.20%, 84.94% and 85.73% for Debre Markos Feeder 4 respectively. The performance comparison of GrMHSA and MOPSO has been made and GrMHSA has been found better in terms of reducing voltage deviation and power losses in the system.

Multi-Agent Model-Based Optimization for Future Electrical Grids

Research carried contains analysis of test network over the inclination of authority towards providing var compensation at higher voltage with respect to distributed pattern of reactive compensation made available at load end. Sectionalized scenario of 39 bus network (a part of North-Regional Indian Grid) having two 400 kV, five 220 KV and sixteen 132 KV stepping down to sixteen 33 kV Grid substations are modeled. Analytics of reactive power penetration at different voltage level is carried out. Because currently utilities are hampered by jumbled way of network compensation during peak hours causing the role of voltage-controlled devices questionable. Exactly now substation run the equipment's as guided from load dispatch centers. Large grid investments unable to identify the desired amount of reactive power penetration to compensate from the utility end. These untracked observations are collected as vulnerable results at utility end, as it causes poor voltage profile, raised losses, abrupt tripping and unnecessary heating of elements. Thus, load flow studies to judge the Capacitive/Inductive needs at the component end by placing fictious generator is carried out. Peak and off-peak studies for a load of 370 MW is underlined hereby to judge the variance in var behavior for different amount of compensation made. Also, to build a program for var assessment important markups for static and dynamic var compensation planning are suggested. Its impact on power system elements is carried out with different proposals.

Rajasthan power system has extensively grown in last 10 years due to potential of wind & solar power projects, construction of transmission system for formation of National Grid and for evacuation of large thermal power plants. Large number of 765 kV and 400 kV transmission lines have been constructed. Due to variability of wind and solar power generation, quantum and also direction of power flow on transmission lines is significantly changed. State Load Dispatch Center has instructed to switch off shunt capacitors from 6 pm to 6 am to control high voltage. This paper presents a comparative case study to control high voltage in power system by switching ON shunt reactors vs switching OFF shunt capacitors. Rajasthan power system has four 765 kV GSS, twenty-seven 400 kV GSS, one twenty-two 220 kV GSS and four fifty-two 132 kV GSS is selected to carry out simulation-based case study in MiPower software. Simulation model consists of 943 buses including 85 generator buses, 1142 transmission lines and 201 transformers. The daily routine grid operations without assessing the outcome or achievement level lead to create problems in power network. Shunt reactors are switched OFF at seven 400 kV grid sub stations where as to reduce high voltage shunt capacitor banks have been switched OFF. Case studies are carried out to observe the effect of switching ON shunt reactors to control high voltage instead of switching OFF shunt capacitors. Test network loading is about 10000 MW. The impact on voltage profile of buses, system losses, financial analysis, loadings of system elements is presented at last.

Configuration, operation and management of existing distribution networks are based on passive networks, whereby the role of such networks is confined to transferring electricity from generation and transmission system to load centres. Under this situation, the main function of distribution network is delivering good quality electricity with minimum amount of network control to the load centres at different voltage level regardless of the most critical case. Most distribution networks are designed to operate in radial mode without having generation unit accommodate on them. Continued increase of distributed generation (DG) penetration into existing distribution networks in recent years has resulted in bi-directional power flow and changes in network voltage profile. These in turn caused important impact on the operation of conventional feeder protection schemes that are originally designed based on radial network operation assumption. The protection issues that had been identified in the presence of DG include (i) malfunction of protective devices due to increase of network fault current level, (ii) unnecessary tripping of non- directional relays due to significant fault contribution by DG, (iii) reduction of fault detection sensitivity of overcurrent relays due to fault contribution of DG, (iv) fault clearing time of graded overcurrent relays is affected and (v) operation of re-closer is affected with introduction of LOM relay. It has been reported that future distribution networks are likely to be operated in ring mode rather than radial in order to optimise the integrated capacity of DG. There are advantages in adopting ring mode operation but it could complicate the protection systems of networks with integrated DG. This paper reports an investigation into the impact of distributed generation on the setting of protective devices of distribution networks that originally operated in radial mode and then switched to ring mode and to compare the protection requirements for the two modes of operations.

This paper proposes a unified multi-objective fuzzy optimal power flow (UMOPF) considering total operating cost, power plants emissions, and total real power loss, with transmission line and transformer loading limits, generators ramp-rate limits, and voltage margins constraints. In the proposed UMOPF algorithm, the total system operating cost, total system emissions, including SO 2 , NO x , and CO 2 , fuzzy minimization objectives are solved simultaneously considering fuzzy line flow limit and transformer loading and generator ramp-rate limit constraints, using fuzzy linear programming (FLP). Meanwhile, the total real power loss fuzzy minimization subproblem is solved considering fuzzy bus voltage magnitude limit constraints, which is also solved by FLP. The proposed UMOPF is tested with the IEEE 30 bus system. The simulation results shown that the proposed UMOPF can efficiently and effectively trade off among total system operating cost and power plants emissions considering transmission line and transformer loading limits, and generators ramp-rate limits, with real power loss minimization considering voltage margins, in a fuzzy reasoning sense.

The increasing electricity demand in transmission system has caused the power transmission system experiencing stress condition. This phenomenon has forced the system to need urgent additional supply to maintain system adequacy, in particular the de-regulated power system environment. Distributed generation (DG) has been identified as one of the possible solutions to address this issue. DG installation has the capability to reduce transmission loss and improve the voltage profile. This paper presents evolutionary programming (EP) technique for optimizing the sizing and locations in DG installation. In this study, several DGs have been installed to address the voltage profile improvement and loss minimization; implemented on the IEEE 30-Bus Reliability Test System (RTS). Results obtained from the study revealed that, installation of multi-DGs in a transmission system has significantly minimized the transmission loss along with voltage profile improvement.

A competitive decentralized framework for Volt-VAr optimization of transmission and distribution systems with high penetration of distributed energy resources