Optimal Design of a Wide Area Measurement System Using Hybrid Wireless Sensors and Phasor Measurement Units

Real-time monitoring of the power system by phasor measurement units (PMUs) leads to the development of such devices in a wide area measurement system (WAMS). However, the power system observability cannot be obtained by employing only PMUs. The communication infrastructure (CI) is a significant part of the WAMS that has to be optimally designed and implemented to collect data from PMUs and deliver them to control centers. In this paper, a novel hybrid wireless sensor network is proposed for the connection of PMUs throughout the system to enable convenient and low-cost communication media. The problem of observability in the communication system is checked along with the optimal placement of PMUs in the power system to reach full observability. A hybrid wireless sensor network including plug-in powered sensor nodes (PPSNs) and energy harvesting sensor nodes (EHSNs) is utilized for increasing the reliability of the communication system. In the proposed co-optimal PMU-sensor placement problem, the main objective is to minimize the total cost of PMU placement and the related communication system, considering full observability of the power system and CI. To achieve better results, the zero-injection bus (ZIB) effect and system observability redundancy index (SORI) are considered as a constraint in the objective function. A binary-coded genetic algorithm is used for solving the proposed mixed-objective optimization problem subject to different technical operating constraints. The proposed method is examined on IEEE 13-bus and IEEE 37-bus test feeder systems. The results show the applicability and effectiveness of the proposed method compared with the conventional methods in this subject area

A new approach to reduce the expected energy not supplied in a power plant located in a non-expandable transmission system

The main objective of most of power plants is to inject power as much as possible into the grid from the power plants. However, the transmission system may restrain the output capability of the power plant, especially, if the power plant is located in an area of non-expandable transmission system. In this situation, any disturbance in the nearby transmission system may force the plant to generate lower than its rated value, which disables it from selling the remaining available generated power to the costumers and also increases the cost of energy not supplied. In this paper, an efficient method is proposed to determine the maximum output capacity of the power plant, by which the avoidable cost of energy not supplied, is not burdened on the plant. The effectiveness of the proposed method has been evaluated on a three machine test system and also on the actual large Mashhad power plant in Iran

A new approach to reduce the non-linear characteristics of a stressed power system by using the normal form technique in the control design of the excitation system

In this paper, a new approach is presented to reduce the nonlinear characteristics of a stressed power system by reducing its second-order modal interaction through retuning some parameters of the generator excitation system. In order to determine the second-order modal interaction of the system, a new index on nonlinearity is developed using normal form theory. Using the proposed index of nonlinearity, a sensitivity function is formed to indicate the most effective excitation system parameters in the nonlinear behavior of the system. These dominant parameters are tuned to reduce the second-order modal interaction of the system and to reduce the index on nonlinearity. The efficiency of the proposed method is validated using a four-machine two-area test system. Simulation results show that a proper tuning of the excitation controller can reduce the second-order modal interaction of the system and can even improve the transient stability margin of the network

An analytical approach and finite element evaluation of leakage fluxes of the PMs in a non-slotted axial flux permanent magnet machine

PurposeConsideration of leakage fluxes in the preliminary design stage of a machine is important for accurate determination of machine dimensions and prediction of performance characteristics. This paper aims to obtain some equations for calculating the average air gap flux density, the flux density within the magnet and the air gap leakage flux factor.Design/methodology/approachA detailed magnetic equivalent circuit (MEC) is presented for a TORUS-type non-slotted axial flux permanent magnet (TORUS-NS AFPM) machine. In this MEC, the leakage flux occurring between two adjacent magnets and the leakage fluxes taking place between the magnet and rotor iron at the interpolar, inner and outer edges of the magnets are considered. According to the proposed MEC and by using flux division law, some equations are extracted. A three-dimensional finite element method (FEM) is used to evaluate the proposed analytical equations. The study machine is a 3.7 kW and 1,400 rpm TORUS-NS AFPM machine.FindingsThe air gap leakage flux factor, the average air gap flux density and the flux density within the magnet are calculated using the proposed equations and FEM. All the results of FEM confirm the excellent accuracy of the proposed analytical method.Originality/valueThe new equations presented in this paper can be applied for leakage flux evaluating purposes.</jats:sec