Surachai Chaitusaney

Maximum-Allowable Distributed Generation Considering Fault Ride-Through Requirement And Reach Reduction of Utility Relay

Distribution systems are changing from a one-source supplying structure into a multisource supplying structure with participations of distributed generations (DGs). These changes face problems caused by DGs. This paper considers typical problems, such as system operating limits, reach reduction of utility relay, and the fault ride-through requirement from distribution system operators (DSOs) in order to maximize DG installation. A new fault calculation technique for a system with inverter-based DGs is revised and employed in an algorithm proposed for maximizing DGs. The IEEE 34-Node Test Feeder is then used to illustrate the effectiveness of the algorithm to determine the maximum-allowable DG installed in this system.

AC power flow sensitivities for transmission cost allocation

Under competitive environment of electric supply industry, customers will have options to purchase energy and services from different sources. For this implementation, transmission cost allocation is an important issue to be considered. This paper proposes a method for allocating transmission costs to all participants based on the ratio of incremental power flow caused by each participant and the transmission line capacity. The proposed method employs full AC power flow sensitivity analysis, which provides more accurate results than the ones derived from DC or decoupled power flow. In addition, it can also manage the reactive power transaction. The proposed method has been applied with the case studies of IEEE 30-bus test system. Encouraging results have been obtained.

Coordination of dispatchable distributed generation and voltage control devices for improving voltage profile by Tabu Search

Distributed Generation (DG) may bring about voltage violation, especially the ones that are powered by renewable energy resources. In order to cope with this problem, this paper proposes a method to coordinate the dispatchable DG with voltage control devices by using Tabu Search (TS) algorithm. In addition, probabilistic load flow calculation based on Monte Carlo simulations is performed for thorough evaluation of the uncertainties from renewable DG and loads. The proposed method is demonstrated in IEEE 34-bus distribution test system.

Linear Least-Squares Method for Conservation Voltage Reduction in Distribution Systems With Photovoltaic Inverters

Considering photovoltaic inverters (PVs) as controllable VAr sources pave the way for an effective implementation of conservation voltage reduction (CVR) in distribution systems with multiple voltage regulating devices, this paper proposes some acceptable approximations to formulate a linear least-squares problem for optimizing a CVR implementation on the smart grid platform. The optimization problem is solved by using a built-in solver of the MATLAB software embedded in an iterative-based algorithm. The proposed algorithm is well verified by comparing its generated result with a trustful solution obtained from examining all possibly coordinating combinations of voltage regulating devices and PVs in the simplified Maehongson test system in Thailand. Effectiveness of the algorithm is also illustrated on that test system with a consideration of time-variant load and PV generation. All revealed features exhibit the high ability of applying the proposed method for implementing a closed-loop CVR functionality in distribution systems.

Impacts of inverter-based distributed generation control modes on short-circuit currents in distribution systems

With the rapid increase in using New/Renewable Energy Resources, Inverter-based Distributed Generations (IBDG) are more and more widely installed in electric power systems. However, the limited short-circuit current contributed from these generators should be noted for the operation of the protection systems. This paper analyzes the changes of short-circuit currents in distribution system with the penetration of IBDG and illustrates how the inverter control modes affect the response of the IBDG. Then, an adaptive algorithm is proposed for short-circuit currents calculation. A simulation in Matlab/Simulink environment comprehensively compares the changes of short-circuit current in the system before and after installing IBDG as well as verifies the proposed algorithm.

Maintaining the reach of protective devices in distribution system with penetration of distributed generation

Protection schemes of distribution system are designed conventionally for radial feeder structure with one source supplying. The presence of distributed generation as the second source causes the protection schemes to be confused in operations. This paper evaluates the reach of protective relays after distributed generation has been installed into the system. All types of faults are analyzed with the consideration of system grounding methods and connection transformer which connects distributed generation to power system. Then, an approach is proposed to maintain the protected areas of protective devices.

Maximization of Distributed Generation with consideration of Fuse-Recloser coordination

Distributed Generation (DG) is more and more widely used in power system. However, the installation of DG increases the short circuit level and may affect the Fuse-Recloser coordination. As a result, it can bring about the reduction of system reliability. The impact depends on sizes, locations, and control modes of DG. Therefore, this paper presents a procedure to determine the maximum capacity of DG in order to maintain the Fuse-Recloser coordination. In addition, the comparison of system reliability with and without using the proposed maximum capacity of DG is presented via three reliability indices, i.e. SAIFI, SAIDI, and ENS. The performance of the proposed method is tested in the reliability test system RBTS bus 2.

Integration of battery for attenuating frequency fluctuation due to wind turbine generation

Wind turbine generation has been in operation for both on-site and commercial uses. However, one major obstruction of the wind turbine generation is its uncertainty. As known, the wind power is dependent on the cube of wind speed, which varies over time. To obtain the maximum wind power, variable-speed Wind Turbine Generators (WTGs) are operated. As a result, fluctuation of power output occurs. Inevitably, this brings about the fluctuation of system frequency. This paper proposes a method of integrating storage battery system to the Load Frequency Control (LFC). The proposed model - comprising of WTGs, hydro power plants, battery system, loads, and control systems - shows that the frequency fluctuation is attenuated effectively. In addition, the impact of battery time constant and storage capacity has been investigated.

An approach for evaluating the impact of an intermittent renewable energy source on transmission expansion planning

We propose a new robust optimization approach to evaluate the impact of an intermittent renewable energy source on transmission expansion planning (TEP). The objective function of TEP is composed of the investment cost of the transmission line and the operating cost of conventional generators. A method to select suitable scenarios representing the intermittent renewable energy generation and loads is proposed to obtain robust expansion planning for all possible scenarios. A meta-heuristic algorithm called adaptive tabu search (ATS) is employed in the proposed TEP. ATS iterates between the main problem, which minimizes the investment and operating costs, and the subproblem, which minimizes the cost of power generation from conventional generators and curtailments of renewable energy generation and loads. The subproblem is solved by nonlinear programming (NLP) based on an interior point method. Moreover, the impact of an intermittent renewable energy source on TEP was evaluated by comparing expansion planning with and without consideration of a renewable energy source. The IEEE Reliability Test System 79 (RTS 79) was used for testing the proposed method and evaluating the impact of an intermittent renewable energy source on TEP. The results show that the proposed robust optimization approach provides a more robust solution than other methods and that the impact of an intermittent renewable energy source on TEP should be considered.

Model of Power Factor Charge for Photovoltaic Generation System Based on its Contribution to Power Systems

This paper proposes a power factor charge model, which considers the operation of photovoltaic generation system (PVGS). The proposed model is aimed to encourage Very Small Power Producer (VSPP) to have contribution, by its operation, to voltage regulation in the connecting power system. The proposed model allows PVGS has to either consume or supply reactive power for maintaining system voltages to be within an acceptable range. In the financial part, consuming or supplying reactive power may cause the power factor charge to be increased while the opportunity for generating active power (PVGS income) to be reduced. The proposed model is tested in impact of PVGS to utility grid, and the results show that PVGS can have contribution to grid support.