Chao-Shun Chen

Optimization of Photovoltaic Penetration in Distribution Systems Considering Annual Duration Curve of Solar Irradiation

The penetration level of a photovoltaic (PV) system is often limited due to the violation of voltage variation introduced by the large intermittent power generation. This paper discusses the use of an active power curtailment strategy to reduce PV power injection during peak solar irradiation to prevent voltage violation so that the PV penetration level of a distribution feeder can be increased to fully utilize solar energy. The PV power generation is simulated according to the hourly solar irradiation and temperature data provided by the weather bureau. The voltage variation at the point of common coupling (PCC) is also derived by executing the 3-φ load flow analysis to investigate the maximum PV power injection without causing a voltage violation problem. When using the proposed voltage control scheme for limiting PV power injection into the study distribution feeder during high solar irradiation periods, the total power generation and total energy delivered by the PV system over a one-year period are determined according to the annual duration of solar irradiation. The annual cash flow from sales of PV power, the O&M cost over the system life cycle, and the capital investment in the PV system are then used to calculate the payback years and the net present value (NPV) of the PV project. With the proposed voltage control to perform the partial generation rejection of PV systems, the optimal installation capacity of PV systems can be determined by maximizing the net present value of the system so that better cost effectiveness of the PV project and better utilization of solar energy can be obtained.

Enhancement of PV Penetration With DSTATCOM in Taipower Distribution System

The PV penetration level of a distribution system is often limited by the violation of voltage variation caused by large intermittent power generation. This study investigates the use of a distribution static compensator (DSTATCOM) in reactive power compensation for system voltage control, during peak solar irradiation, in order to increase the PV installation capacity of a distribution feeder and avoid the voltage violation problem. PV power generation is simulated using hourly solar irradiation and temperature data provided by the weather bureau. The voltage variation at the point of common coupling (PCC) is also derived by executing the 3- φ load flow analysis to determine the maximum PV power injection without causing voltage violation. By applying the proposed voltage control scheme of DSTATCOM during high solar irradiation periods, the total power generation and the total energy delivered by the PV system over one year are determined according to the annual duration of solar irradiation. The annual sales of PV power, the system O&M cost, the cost of DSTATCOM installation and the initial capital investment for a PV system are then used to calculate the cash flow over the system life-cycle and the final net present value (NPV) of the PV project. With the proposed DSTATCOM voltage control to perform reactive power compensation, the optimal installation capacity of PV systems can be determined by maximizing the net present value of the system to ensure the best cost-effectiveness of the PV project and to better utilize solar energy.

Financial Analysis of a Large-Scale Photovoltaic System and Its Impact on Distribution Feeders

To promote the photovoltaic (PV) installation, a large-scale PV system installed in the Main Stadium of the 2009 World Games has been investigated for the design of selling price of PV power generation. The PV power generation is simulated according to the hourly solar irradiation and temperature provided by the weather bureau. The cash flow of annual power generation, the O&M cost, and the capital investment cost of the PV system is then used to derive the payback years and the internal rate of return for the PV system under different selling price of PV power generation. The voltage variation and the power system loss of the distribution feeder, which serves the Main Stadium, are also performed by executing the 3-φ load flow analysis for the impact analysis of the PV system. The results indicate that the reduction of voltage drop and power system loss can be obtained with the PV system installed to provide the dispersed generation for the local loads. However, the PV system penetration is limited due to the violation of voltage variation introduced by the large intermittent PV power generation. The selling price of PV generation has to be designed according to the conditions of solar irradiation and temperature so that sufficient incentives can be provided to encourage more customers to participate the PV program.

Financial Analysis of a Large Scale Photovoltaic System and Its Impact on Distribution Feeders

To promote the PV installation, a large scale photovoltaic (PV) system installed in the Main Stadium of the 2009 World Games has been investigated for the design of selling price of PV power generation. The PV power generation is simulated according to the hourly solar irradiation and temperature provided by the weather bureau. The cash flow of annual power generation, the O&M cost and the capital investment cost of the PV system is then used to derive the payback years and the internal rate of return for the PV system under different selling price of PV power generation. The voltage variation and the power system loss of the distribution feeder which serves the Main Stadium are also performed by executing the 3-φ load flow analysis for the impact analysis of the PV system. The results indicate that the reduction of voltage drop and power system loss can be obtained with the PV system installed to provide the dispersed generation for the local loads. However, the PV system penetration is limited due to the violation of voltage variation introduced by the large intermittent PV power generation. The selling price of PV generation has to be designed according to the conditions of solar irradiation and temperature so that sufficient incentives can be provided to encourage more customers to participate the PV program.

Artificial Neural Network Based Adaptive Load Shedding for an Industrial Cogeneration Facility

This paper presents the design of adaptive load shedding strategy by executing the artificial neural network (ANN) and transient stability analysis for an Industrial cogeneration facility. To prepare the training data set for ANN, the transient stability analysis has been performed to solve the minimum load shedding for various operation scenarios without causing tripping problem of cogeneration units. Various training algorithms have been adopted and incorporated into the back- propagation learning algorithm for the feed-forward neural networks. By selecting the total power generation, total load demand and frequency decay rate as the input neurons of the ANN, the minimum amount of load shedding is determined to maintain the stability of power system. To demonstrate the effectiveness of the ANN minimum load-shedding scheme, the traditional method and the present load shedding schemes of the selected cogeneration system are also applied for comparison and verification of the proposed methodology.

Adaptive relay setting for distribution systems considering operation scenarios of wind generators

This paper presents a method for an adaptive relay setting for distribution systems with wind generators (WGs). The advanced distribution automation system (ADAS) is applied to monitor the operational status of WGs and line switches. For the change of operational status of WGs or network reconfiguration of distribution systems because of the operation of line switches, the function of the adaptive relay setting is activated by the ADAS control master station. Short-circuit analysis is performed to solve the magnitude and direction of fault-current flows. The protective relay settings are then accordingly revised and loaded to the protective relays along the feeder to achieve the adaptive fault protection. Sample distribution feeders with open- and closed-loop configurations are used to demonstrate the adaptive relay setting for distribution systems with various operational scenarios of WGs. It is concluded that the fault currents contributed by WGs must be included in the design of the tap/level settings of protective relays by the ADAS to achieve good protection of smart distribution systems.

Load profile synthesis and wind power generation prediction for an isolated power system

This paper investigates the power load composition of an isolated power system using a load survey study and estimates wind power generation with a probabilistic network. The typical load pattern of various customer classes is derived, which are then used to derive the total power consumption of all customers within each class. A probabilistic neural network is used to solve the wind power generation based on the wind speed for an offshore island in Taiwan. With the hourly wind speed and load composition, the power generation of diesel generators was obtained. Results of this paper demonstrate that wind power generation can economically and effectively replace the power generation of the islands diesel power plant and provide partial power-supply capability for the net peak load requirement.

Design of phase identification system to support three-phase loading balance of distribution feeders

In this paper, a phase identification system (PIS) is designed to incorporate a fuzzy microprocessor-based controller for phase measurement of underground transformers. The proposed fuzzy calibration algorithm used in the controller aims to solve the offset and gain of frequency deviation of the real-time clock, which was generated by a voltage-controlled crystal oscillator (VCXO) to maintain the timing lock with respect to the 1 pulse per second signal of the global positioning system before phase measurement is executed. According to the field test of the PIS design, the phase deviation of the real-time clock with embedded VCXO can be improved from 46.27° to 0.98° by applying the fuzzy calibration algorithm. The PIS has been applied for field measurement of underground distribution transformers to identify their phases and correct the corresponding attributes of the automated mapping faulty management (AM/FM) system in Taipower. By retrieving the information of the line segments and transformers from the AM/FM, the network modeling of distribution feeders is derived to analyze the three-phase unbalance. The rephasing strategy of laterals and distribution transformers has been derived and executed by Taipower engineers. By comparing the phase currents and neutral current of a test feeder before and after rephasing, the three-phase balance of the distribution system can be significantly enhanced with the PIS to identify the phasing of distribution transformers for deriving the rephasing strategy of the distribution feeders.

Electric Power System Analysis and Design of an Expanding Steel Cogeneration Plant

This paper presents the electric power system analysis and design of an expanding steel cogeneration plant. The site and capacity of shunt capacitor banks as well as the tap position of transformers are determined according to the power flow analysis. Also, to comply with the restriction of circuit breaker capacity, the high-impedance transformers are designed. In addition, the voltage fluctuation resulted from the dramatic reactive power variation of hot strip rolling mill can be greatly reduced if proper static var compensator is installed. The significant voltage sag due to the starting of induction motor can be effectively improved by applying wye-delta transformer starter. Furthermore, the total voltage harmonic distortion and the total current demand distortion are both acceptable if the proper filters are installed. It is also found that the cogeneration system can keep stable operation in autonomous mode by applying the governor control action and the load-shedding scheme after tie line tripping. It is concluded that the power system analyses are important for the steel plant with cogeneration unit to identify hidden problems and remedy strategy to ensure the system power quality and operation performance.

Design of Optimal Coasting Speed for MRT Systems Using ANN Models

An artificial neural network (ANN) has been proposed in this paper to determine the optimal coasting speed of train operation for the Kaohsiung Mass Rapid Transit (KMRT) system to achieve the cost minimization of energy consumption and passenger traveling time. A train performance simulation (TPS) is applied to solve the energy consumption and the traveling time required to complete the journey between stations with various riderships to create the data set for ANN training. The ANN model for the determination of the optimal coasting speed is then derived by performing the ANN training. To demonstrate the effectiveness of the proposed ANN model, the annual ridership forecast of the KMRT system over the project concession period from 2007 to 2035 has been used to determine the optimal coasting speed of train sets for each study year according to the distance between stations and the passenger ridership. The power consumption profile of train sets and the traveling time of passengers have been solved by TPS to verify the reduction of social cost for KMRT system operation with the optimal coasting speed derived.