Volume 10, Issue 4

This paper proposes using an adaptive immune algorithm (AIA) for reactive power optimization. The adaptive immune algorithm automatically adjusts the parameters to achieve the balance between fast convergence and high diversity of antibodies, according to the distance between the antibodies. It leads to the reduction of the computation time, compared with other methods. The test results of several examples demonstrate that reactive power optimization based on AIA method has advantages in terms of computation speed and convergence speed.

Whether a disturbance will trigger unexpected protection operation to exacerbate the normal operation state or even lead to the unstable state depends on the transient energy that the system gains during the fault period. The paper presents a new gradient projection approach to calculate the critical energy for transient stability assessment of the power system with the protection operation. The method takes the projection of the potential energy gradient on the key protection operation surface as search direction and iteratively searches for the critical energy at the surface; in order to let the optimal point be the feasible point, the generator angles are considered as control variables of power flow equation to solve network bus voltage and angle during the searching process. Examples show that the convergence and precision of the new method proposed is much better than that of other methods, which demonstrates the validity and feasibility of the new method.

This paper summarizes international experience of significant clustered photovoltaic systems. Based on the operation experience, major system impacts and corresponding solutions have been studied. Among them, voltage raise of power distribution line due to the reverse power flow from the PV system has been one of the main problems. Therefore, this paper proposes the dynamic and steady-state simulations to evaluate the effectiveness of battery-integrated PV system on avoiding the over voltage problem. Furthermore, different types of battery control modes have been compared. In the simulations, the actual product specifications were adopted as the parameters of the component models, and the largest PV cluster system in Taiwan was chosen as the analyzed demonstration site. The simulation results reveal that the developed control algorithms could avoid voltage rise by setting appropriate control parameter values. In addition, these control algorithms could be applicable to other power grids if appropriate settings are made.

The analysis of satellite solar power station (SSPS) is carried out for some specified locations in India and consequently the performance of the system is evaluated for geostationary earth orbit (GEO)-based SSPS and low earth orbit (LEO)-based SSPS for sites located at different latitudes. The analysis of power, the received energy over a year, and the received energy during a day for the same beam intensity show better results for LEO-based SSPS system as compared to GEO-based system. However GEO-based system is advantageous in the sense that it will deliver constant energy to the load throughout a year. Thus it is concluded that GEO-based system is suitable for base load power plant. The weight of the rectenna and hence the space required for ground station for same power output for GEO-based system is greater than that for LEO-based system which will in turn increase the overall cost of the GEO-based system. These findings may help for judicious selection of orbit for placing the satellite for SSPS.

Wind energy conversion systems have become important in the research of renewable energy sources. This is in no small part due to the rapid advances in the size of wind generators as well as the development of power electronics and their applicability in wind energy extraction. However, wind energy has a drawback of having only 1/800 (gm per cubic cm) density as compared to that of water energy. Wind energy does not remain constant and wind turbine output is proportional to the cube of wind speed, which causes the generated power of the wind turbine generator (WTG) to fluctuate. In this paper, a technique is proposed for output power leveling of a wind generation system. Wind turbine blades have a large inertia compared to the inertia of a generator. The inertia of the rotor behaves like an inductor in an electrical circuit. It helps smooth the wind turbine output power, stores energy during acceleration, and restores energy during deceleration. The effectiveness of output power leveling control is verified by simulations for the wind power generation system.

Islanded power system can be formed by unexpected electric equipment failure or initiative breaking off of a main system avoiding a whole collapse. Unbalanced power between generation and load may cause an overspeed of the units and trigger the action of Overspeed Protection Controller (OPC) which is mainly designed for a load rejection condition. The mathematic model was built to simulate the islanded system stability with the effect of OPC. The simulation reproduced the power and frequency oscillation as the accidents. The results show a great impact of OPC on the stability of an islanded system. Modified OPC logic was proposed to avoid the oscillation and increase the stability.

There is an attempt to correlate the public health risk with strong magnetic fields from high voltage multiple transmission lines. The statement is based on the public perception that multiple sources of two and three tower lines can generate more radiated fields as compared to single tower. This paper evaluates the fact and figures on realistic situation cases about radiated field exposures based on measurements and simulation models of two and three transmission lines. The case study sites which consist of several towers of 132kV and 275kV lines were located in Melaka district, Malaysia. Measurement procedures of magnetic fields were conducted based on the IEEE/ANSI 644 standard while the dose exposure reference value was based on the public exposures of the ICNIRP limits. The results obtained from this analysis are then compared with the ICNIRP standard for assessing the significance of dose exposure between actual conditions in TNB systems with optimum simulated models of phase arrangements. Recommendations on the threshold value limits at both ROW for the new and existing transmission lines were also proposed in conjunction with development of TNB ELF-EMF policy guidelines.

This paper proposes the application of computational intelligence techniques to assist complex problems concerning lightning in transformers. In order to estimate the currents related to lightning in a transformer, a neural tool is presented. ATP has generated the training vectors. The input variables used in Artificial Neural Networks (ANN) were the wave front time, the wave tail time, the voltage variation rate and the output variable is the maximum current in the secondary of the transformer. These parameters can define the behavior and severity of lightning. Based on these concepts and from the results obtained, it can be verified that the overvoltages at the secondary of transformer are also affected by the discharge waveform in a similar way to the primary side. By using the tool developed, the high voltage process in the distribution transformers can be mapped and estimated with more precision aiding the transformer project process, minimizing empirics and evaluation errors, and contributing to minimize the failure rate of transformers.