Te-Tien Ku

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.

Loading Balance of Distribution Feeders With Loop Power Controllers Considering Photovoltaic Generation

For the operation of distribution systems, loading balance of distribution feeders is important for reducing power loss and mitigating power flow overloading. In this paper, a loop power controller (LPC) is applied for the control of real power and reactive power flows by adjusting voltage ratio and phase shift so that the loading balance of distribution feeders can be obtained. To incorporate photovoltaic (PV) power generation in feeder loading balance, a Taipower distribution feeder with large PV installation is selected for computer simulation. Daily loading unbalance is determined by analyzing PV power generation recorded by the SCADA system and by constructing daily power load profiles based on distribution automation system (DAS) data. The load transfer required to achieve loading balance and the line impedance of distribution feeders are used to derive the voltage ratio and phase shift of the LPC. Computer simulations indicated that loading balance can be achieved in distribution feeders with large PV system installation by using loop power controllers according to the variation of solar energy and power loading of study feeders. The system power loss reduction resulting from feeder loading balance by LPC is also investigated in this paper.

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.

Design of PLC-Based Identifier to Support Transformer Load Management in Taipower

To support transformer load management, a narrow-band power line carrier (PLC)-based identifier has been designed and developed for the determination of customers served by each distribution transformer. The transmission characteristics of a PLC signal over low-voltage distribution lines is simulated by using the mathematical model of distribution transformers, line conductors, and customer loading at high frequencies of the carrier signal. After completing the development of PLC-based identifier, a field test has been executed to verify the performance of the identifier to determine the connectivity of the distribution transformer and the customers served without requiring power service interruption. With the customer account numbers updated by the PLC identifier, the monthly energy consumption and the service type of customers served by each distribution transformer are retrieved from the customer information system. The daily power profile and peak loading of the distribution transformers are then derived according to the energy consumption and the typical load patterns of the customers served.

Applications of FANP and BOCR in renewable energy - Study on the choice of the sites for wind farms

As the consciousness of human beings in preserving the world increases, the demand of alternative energy resources has been expanding exponentially in recent years, and wind power is one of the most promising renewable energy resources. Taiwan, with its abundant coastal wind resources and good geographical conditions, is very suitable for developing wind farms. The development and implementation of renewable energy regulations have defined a direction for future renewable energy development in Taiwan. This also shows Taiwans determination to follow the footsteps of the developed countries and the commitment to environmental protection. Therefore, the decision making of wind farms has become the most important link for the construction of wind farms in the future. This paper proposed a fuzzy analytic network process with benefit-opportunity-cost-risk approach to systemize the complicated decision making of wind farm site selection. A case study is carried out to examine the proposed approach and to evaluate the performance of several existing wind farms in Taiwan. By adopting the systematic analysis method, the most suitable wind farm can be determined, and the results can be references for planning and development of wind power industry in the future.

Impact of PV generation to voltage variation and power losses of distribution systems

To promote the PV installation in Taiwan, a large scale photovoltaic (PV) system with total capacity of 1000kWp has been installed in a sporting complex in Kaohsiung, which is connected to the Taiwan Power Company (Taipower) distribution feeder. This paper is to investigate the impact of large PV system to the operation of distribution feeders. The PV power generation is simulated according to the hourly solar irradiation and temperature provided by the weather bureau. The voltage variation and the power system loss of the study distribution feeder are simulated by executing the three-phase 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.

Identification of customers served by distribution transformer using power line carrier technology

In this paper, a narrow-band power line carrier (PLC) based identifier has been designed and developed to support the on line identification of customers served by each distribution transformer. To investigate the transmission characteristics of power line carrier signal over low voltage distribution lines, the mathematical model of distribution components such as transformers, low voltage conductors, customer appliances, etc. at PLC carrier frequency are derived and included in the computer simulation. The two port network is used to represent the low voltage distribution systems and Matlab/Simulink is applied for the analysis of PLC signal attenuation from the secondary side of transformer to the customer locations. After completing the development of PLC based identifier, the field test of a commercial building has been executed. The PLC signal strength and the noise level have been measured to verify the effectiveness of the identifier to determine the connectivity of distribution transformer and the customers served without requiring power service interruption.