Adaptive control design for a synchronous generator

The operating point of a power system changes to an unknown point with an unknown change in the mechanical input power. In this paper, a nonlinear adaptive controller is designed for excitation system of the generator based on the backstepping control technique, in order to achieve transient stability enhancement, in the presence of uncertainties in mechanical power. The designed controller guarantees the convergence of system states to new desired values corresponding to unknown mechanical power. A power system consisting of a synchronous generator connected to an infinite bus through a double circuit transmission line is used in control design and the simulation studies. Computer simulation verifies the effectiveness and the validity of the proposed control, considering faulted system with a clearance and change in network topology. © 2014, Editura Academiei Romane. All rights reserved

Improving the stability of the DFIG power system in the presence of SSSC in a nonlinear manner

In this paper, the problem of improving the stability of the power system with DFIG and in the presence of SSSC using nonlinear method is discussed. The nonlinear controller is designed by the multi-input backstepping method with a sliding mode observer. This controller is applied simultaneously to the excitation system of synchronous generators and the rotor side converter in DFIG and SSSC in a way that improves the stability of the power system compared to the linear and nonlinear methods described in this paper. The control coefficient matrices are adjusted using intelligent algorithms in such a way that the stability of the system is more optimized. Practical constraints on the system are considered in selecting the control inputs. The designed controller is robust to changes in the operating point and the location of the disturbance. The performance of the designed controller in a 39-bus, 10 machines NEW ENGLAND network including DFIG generators and in the presence of SSSC is simulated and investigated using MATLAB software

Optimal Load Shedding in Deregulated System and Consideration of Effective Factors by Using a Predictor-Corrector Interior-Point Method (IPM)

In this paper, intifially an introduction is presented about Electric Power market in deregulated system and load shedding by interior-point method in these systems. Then, predictor-corrector of IPM is considered and by consideration of the IEEE 6 busbar network, distribution of load by using software (PSAT) will be considered. Then, with introduction of bilateral contracts in organized renewal system, the proposed method is applied to make optimal load shedding in the IEEE 30 busbar network. In this direction, the effective factors on changes of load- shedding model are analyzed completely. Some of factors are price changes, congestion lines (result from emitting of one or more lines) and maximum load-shedding limit in each bus bar

Coordination of overcurrent relays in microgrids according to the input and output of resources

In this paper, the directional overcurrent relays are adjusted according to the input and output of resources in the microgrid. Changes in the network structure will change the performance of the relays, so they will cause interruptions and thus reduce the reliability of the network. In the method used, by considering the injection of a virtual current according to the source isolated from the system, an attempt has been made not to change the initial settings of the directional overcurrent relays. Accordingly, using a telecommunication platform, all the required information is sent to the relays, and the relays, due to the presence or absence of sources, have a virtual value equal to the amount of short-circuit current of the separated or added sources in a soft way. They receive hardware, and this prevents the relay settings from changing to the original state where all resources are in service. The method used in an IEC microgrid with different generation types and in different operating modes and with respect to the presence or absence of short circuit power supplies, has been investigated

Optimized implementation of intelligent controller based on the Lyapunov energy function of FACTS devices for improving transient stability

In this paper, improvement of the transient stability of power systems using the Flexible AC Transmission Systems (FACTS) parallel devices (ASVC and SVC) has been analyzed. Control methods that have been used in this paper, based on Lyapunov theory and Transient Energy Function (TEF) is used. Controls the damping system ensures However, in order to improve the damping rate of the intelligent optimization methods are used. In this direction, a new optimization method Shuffled Frog Leaping (SFL) was used. The objective function considered in this way, which tends to be the dominant attenuation due to practical constraints. Simulation results show the effectiveness of the proposed optimal control method

Modulation of Current Source Inverter

Direct torque control with Current Source Inverter (CSI) instead of voltage source inverter is so appropriate because of determining the torque of induction motor with machine current and air gap flux. In addition, Space-Vector Modulation (SVM) is a more proper method for CSI because of low order harmonics reduction, lower switching frequency and easier implementation. This paper introduces the SVM method for CSI and uses the proposed inverter for vector control of an induction motor. The simulation results illustrate fast dynamic response and desirable torque and speed output. Fast and accurate response to changes of speed and load torque reference completely proves the prominence of this method