جستجوی مقالات مرتبط با کلیدواژه « load shedding » در نشریات گروه « برق »

The phenomenon of Fault-Induced Delayed Voltage Recovery (FIDVR) appears in networks with high penetration of induction motor loads because the increase in requested reactive powers of motor loads after clearing the fault prevents the rapid return of the bus voltage to the pre-fault level. Load shedding is one of the effective ways to deal with the FIDVR phenomenon, which causes the amount of demand to approach the production of reactive power. In this paper, a wide-area load-shedding method is presented, which performs based on network conditions and loads. Since the introduced indicators for determining the locations and amounts of loads to be shed are based on the values of bus voltages, loads currents, and network impedance matrix; therefore, the proposed method can effectively shed the loads and deal effectively with FIDVR. The voltage estimation process is an important tool to predict the voltages at future moments and is defined based on the modified Gauss-Seidel load flow and the three-order model of the induction motor. This tool enables the proposed method to understand the effect of applying load shedding on voltage recovery and prevents the application of unnecessary ones.

This paper proposes a new voltage stability assessment method based on vector analysis method. This index extraction process relies on measurements of active and reactive powers from connected buses to the generator buses. Therefore, a limit for beginning of voltage collapse is determined based on the maximum power transfer theory. On the other hand, when the system requires load shedding, a new voltage-frequency load shedding has been employed. This load shedding makes voltage and frequency stabilities be guaranteed via clustering of all loads as allowable and unallowable, and prioritizing allowable cases. Simulation results in DIGSILENT Power Factory software on IEEE-39 bus dynamic test system demonstrate the efficiency of proposed approach with respect to other methods.

Dou to penetration of stochastic resources in the microgrids, the need for new control and scheduling method is essential. Reconfiguration strategy can be considered as a practical solution for network performance improvement. Therefore, in this paper the scheduling of reconfigurable microgrid (RMG) in the normal and emergency conditions are analyzed. It is assumed that microgrid consists of several small neighboring microgrids, so in addition to the microgrid scheduling in the normal condition, the problem of neighboring microgrid management will be solved in the emergency condition. In the first condition, microgrid total cost minimization is considered as an objective while in the emergency condition, the microgrid divided to several neighboring microgrids and the proposed method tries to find the optimal structure for neighboring connection and minimizes the total load shedding, until the return to the normal condition. The results show the effectiveness of proposed method from the cost and load shedding minimization point of view.

This paper presents a reliability assessment algorithm for radial distribution systems such as microgrids and distributed generation units. The effects of these units and system reconfigurations on distribution system reliability can be evaluated by using the proposed algorithm. The impacts of the location and capacity of the distributed energy resources of microgrids and sectionalizing switches on reliability indices are determined. Moreover, proper location is determined by the classification of load points in distribution system. An approach to identifying the out of the service section after a fault event is presented based on the adjacency matrices. The classification of nodes is obtained by identifying different adjacency matrices based on protective devices. At last, the reliability indices of radial distribution system are calculated.

Nowadays, distributed generation (DG) is widely used in power systems. However, the use of DGs has caused new challenges in different aspects of power system operation, one of which is the effect of DGs on the optimal load shedding. Load shedding is a remedial action triggered after disturbances such line tripping. In fact, due to the line outage, the power flowing through other lines will increase which may cause protection systems to operate to trip the overloaded lines and in severe cases result in the system collapse. In this paper, a general load shedding method is proposed to prohibit the system from moving toward collapsing and helping the system to restore in the presence of DGs. In the proposed method, firstly the most critical line whose outage leads to the minimum values of stability indices is determined. Then, after putting this line out of service, harmony search algorithm is used to find the minimum amount of load shedding as well as the optimal location of DGs so that the loadability of the system is maximized preventing the system to collapse. The efficacy of the proposed methodology is demonstrated through applying it on IEEE 14 and 30-bus systems using various scenarios.