Inclusion Of Distributed Generation Research Articles

Effective Communication-Based Reactive Power Sharing Scheme for Meshed Microgrid in an Islanded Mode

Microgrids (MGs) are the most sought out and feasible solution for the present energy crisis. MG is a group of Distributed Generators (DGs) interacting with each other to provide energy to a defined local area. The inclusion of DGs into the conventional power system at various voltage levels has altered the topology of the power system and their control techniques. Hence, the MGs can no longer be considered as a traditional radial network but rather a meshed network. The control and operation of such practical MGs become a challenge, especially when operated in the islanded mode. This research paper considers a realistic meshed MG operating in an islanded mode for study. In an islanded MG, the issues of real and reactive power sharing among DGs are addressed so that the power contribution of each DG is proportional to its rating, thus preventing overload and ensuring reliable operation. A communication-based virtual impedance estimation is proposed in addition to the droop controller for proportionate real and reactive power sharing among DGs in a meshed MG. With the increased complexity of meshed MG, the proposed communication-based control scheme offers an efficient reactive power sharing between DGs without the feeder and network impedance requirements. A MATLAB simulation study proves the effectiveness of the proposed control strategy for a meshed MG with equal DG ratings and unequal DG ratings under changing load conditions.

Key Aspects and Trends of Distributed Generation and Energy Decentralization in Russia

Distributed Generation (DG) is a global trend and it is actively spreading in Russia. In contrast to Western countries, the main incentive for the spread of DG in Russia is the desire of industrial owners to reduce the final cost of electricity. DG in Russia can successfully meet the challenge of supplying electricity to isolated and inaccessible areas and replacing outdated and inefficient generation. The widespread use of DG, including those based on renewable energy sources (RES) makes it necessary to create promising models for the inclusion of DG in the Unified Energy System (UES) of Russia. The paper deals with the efficiency of DG, analyses the application of this technology in Russia formulates the prospects for the development of DG in Russia and gives recommendations for the integration of DG.

Optimum Location and Size of DG Using GA with Sensitivity Analysis for a Real Time Radial Distribution System

Distributed Generation (DG) must be of appropriate size and location for getting the benefits in the distribution system. Most of the renewable generation is directly grid to a distribution substation to fulfill the load demand; this may not give techno-economic benefit to the utility. A radial distribution system is identified where the wind generation DG is connected at substation bus to fulfill the load requirements. From the study, it is observed that the system does not have any effect on loss as well as voltage profile with the inclusion of DG. This paper discusses a technique to reduce active and reactive power losses in an existing radial distribution system with wind generation connected to the grid. For obtaining minimum loss the evolutionary technique Genetic Algorithm (GA) is implemented. GA includes some parameters which have to be adjusted for getting reliable results. This work is part of the answer to this approach addressing this connective problem. The proposed methodologies being tested on practical radial system representing load with constant impedance models. The optimal size and location of DG in a radial distribution feeder obtained through the techniques with variation in options for GA operators for different values of population size, crossover fraction, and generation. After having a set of optimal location and size of DG by this methodology, with the available generation, the only location of DG changed as per optimal location, and afterward, both optimal location and size are implemented to observe the effect on active and reactive power loss. Test results prove that utilizing available generation at an optimal location reduction in a power loss of 47.81%and 83.66%with an optimum size of DG at an optimal location obtained by the proposed methodology can be obtained. Also, exceptional improvement in voltage at the bus is observed.

Power Flow Analysis of Weakly Meshed Distribution Network Including DG

Power flow is one of the essential studies in power system operation and planning. All steady-state parameters for power distribution systems, such as bus voltage magnitudes, angles, power flows, and power losses, can be calculated by conducting power flow analysis. Distribution system features differ from those of transmission system, rendering conventional load flow algorithms inapplicable. In this paper, three distribution power flow techniques are presented and tested to evaluate their performance when applied to a networked distribution system including distributed generation (DG). These are the distribution load flow (DLF) matrix, the enhanced Newton Raphson (ENR), and the robust decoupled (RD) method. IEEE 33-bus system is adopted for implementing the above methods. Radial and weakly meshed configurations are applied to the tested system with DG inclusion to investigate their influence on the power flow study findings.

Improvement of power supply to rural customers through grid-interactive distributed generation

The integration of Distributed Generation (DG) into distribution grid systems introduces problems in network operation, control and protection. Key issues associated with DG inclusion are voltage or current control, cost-effective operation, protection coordination and network transients. Better understanding of these issues and finding solutions to these problems are important to power industries. This paper has addressed the general issues and problems of DG implementation, and presented solutions for effective operation and control of the DG system. The impact of DG on distribution protection has been investigated and the level of fault contribution by DG during a fault has been determined. The contribution of DG to the improvement of power quality and reliability has been examined. Mitigation of voltage dip transients and reduction of harmonics in the network by DG have been analysed through modelling and simulations. Also, criteria to select DG technology and safety issues with DG integration have been discussed.

Distributed Generation Opportunity under Availability Based Tariff and Reliability Considerations

Availability Based Tariff (ABT) has been implemented in all the regional grids of India for improving grid discipline by frequency dependent pricing. Currently it is limited to short-term energy transactions between the beneficiary States and Central generating stations without the need for negotiations on price or quantum in real time. In the present scenario, Independent Power Producers (IPP), Captive Power Plants (CPP), small Distributed Generation (DG) like mini-turbine, fuel cell, etc., are not considered under ABT. DG units are normally modular in size and they can be placed close to consumers so as to reduce the T&D costs and losses. Hence, they need to be encouraged so as to meet the ever-increasing electricity demands of Indian power sector within the financial constraints. In this paper, impact of IPPs, CPPs and DGs on intra-State ABT is studied. This paper also proposes to study the impact of grid connected DG on network availability and reliability. The improvement in system reliability is studied after evaluating reliability indices like SAIFI, SAIDI, etc., with the inclusion of DG.

Distributed Generation as Voltage Support for Single Wire Earth Return Systems

Key issues for distributed generation (DG) inclusion in a distribution system include operation, control, protection, harmonics, and transients. This paper analyzes two of the main issues: operation and control for DG installation. Inclusion of DG in distribution networks has the potential to adversely affect the control of voltage. Both DG and tap changers aim to improve voltage profile of the network, and hence they can interact causing unstable operation or increased losses. Simulations show that a fast responding DG with appropriate voltage references is capable of reduction of such problems in the network. A DG control model is developed based on voltage sensitivity of lines and evaluated on a single wire earth return (SWER) system. An investigation of voltage interaction between DG controllers is conducted and interaction-index is developed to predict the degree of interaction. From the simulation it is found that the best power factor for DG injection to achieve voltage correction becomes higher for high resistance lines. A drastic reduction in power losses can be achieved in SWER systems if DG is installed. Multiple DG can aid voltage profile of feeder and should provide higher reliability. Setting the voltage references of separate DGs can provide a graduated response to voltage correction.

Impact of distributed generation on protection of single wire earth return lines

Distributed generation (DG) inclusion within the grid system potentially introduces problems related to control, protection, harmonics, and network transients. This paper analyses one of the key issues: protection of the network, by ascertaining the impact of rotary DG inclusion on existing protection system of SWER (single wire earth return) lines and the DG sensitivity during faults. The analysis is carried out by estimating fault-sensitivity for the worst-case situation, determining the DG impact on the existing protection scheme, and comparing the network situation with and without DG during the fault. A model of arc voltage is used to represent a fault on a SWER scheme. The size of DG is selected based on the SWER capacity and SWER load. The study is conducted on an example SWER system by considering the SWER lines with and without DG and faults on the SWER backbone and laterals, and simulation results are reported. In every case studied, the fault current from the DG significantly exceeded the DG rating and the DG would have tripped. Thus the system reverts to the case with no DG. Even if DG did not trip, the fault current from the source would be largely independent of the DG, and thus the original feeder protection would continue to provide the same quality of performance. Hence, net sensitivity and existing protection system will not be adversely affected by DG inclusion in SWER lines.