Search

Lack of coordination between the operation of capacitors and OLTC to voltage control is one of the basic problems in distribution networks, which can cause problems in the control function. In this paper, a new control method is proposed to create coordination between the operation of capacitors and OLTC. The criterion of this coordination is based on fuzzy logic to determine the status of transformer and capacitor function, which reduces unnecessary switching. In this method, the control function is considered with more accuracy such that the quantity of voltage and power factor are set within the range of 0.98 to 1.02 p.u and between 0.95 lag and lead, respectively. Another advantage of the proposed method is that it is automatic and eliminates human resources to adjust the position of the transformer and capacitors. Simulation results are done on the 14-bus network by using two software MATLAB and DIGSILENT, that these results show the accuracy of the proposed method in the desired performance in distribution networks. [ABSTRACT FROM AUTHOR]

During a power swing, the measured impedance may enter the relay protection zone and cause the relay to operate incorrectly. If the relay operates during power swing, it may cause the network to become unstable. Fault detection during a power swing in compensated lines via a series capacitor is more complicated than simple lines. In compensated lines, the amount of the fault current, the series capacitor and its protection equipment, the type of fault, the fault location, the type of capacitor protection, and the compensation level of the series capacitor are the factors affecting the impedance of the fault loop. In this paper, a new method for detecting fault during power swing is presented by using the magnitude of negative sequence phasor of current with the use of the Taylor series. The proposed method is simulated on the IEEE standard network and its performance has been evaluated. This method has high-speed performance for a variety of symmetric and asymmetric faults. The PSCAD and MATLAB programs are used to simulate the proposed method. Comparing the results with other methods shows the efficiency of the method presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a control method based on model predictive control (MPC) to control the buck-type dynamic capacitor (DCAP) to improve power quality. In this method, the reference current consists of two distinct parts, i.e., reactive power compensator (RPC), and hai'monic current eliminator (HCE) and based on the load current and dynamically, it adapts itself to load changes. The proposed prediction model (PM) was extracted from the linearized differential equations of the DCAP. In the proposed method, vector decision variables in each cycle converter switching are updated only once during the prediction horizon, and the optimization problem related to predictive control is solved based on the particle swarm optimization (PSO) algorithm. This reduces the volume of calculations significantly. By considering the total harmonic distribution (THD) value and the power factor (PF) value, the prediction horizon is proposed. The proposed method, unlike the EHM method, has fewer control parameters and can be implemented more easily. The simulation results in MATLAB software showed the superiority of the proposed method in comparison with the EHM method on a single phase DCAP. [ABSTRACT FROM AUTHOR]

In this paper, a new single-stage power factor correction (PFC) converter is presented. In the input stage of this structure, a buck converter is used to correct the power factor. So, the voltage stress of bulk capacitor reduced, and one of the main problems in the single stage PFC converters is solved. Moreover, by employing a compensator circuit, the input current dead angle which is the main drawback of the existing buck type PFCs is obviated, thus the total harmonic distortion is very low. In converters with buck PFC, input current dead angle results in high THD. In the proposed converter, using an inductor coupled with the main transformer, this problem is solved. A part of input power is transmitted directly to the output that helps to improve efficiency. The proposed converter is analyzed and the validity of the proposed solution is proven in the form of theoretical analysis, simulation and practical results. [ABSTRACT FROM AUTHOR]

In this paper, a new method based on Adaptive Neuro-Fuzzy Inference System (ANFIS) is proposed for locating the switched capacitor banks in distribution systems. To train the proposed ANFIS model, an index based on current transient is introduced, which is calculated either offline by using data or online by real time simulation. The proposed method uses only current transient waveforms, immediately before and after the switching instant. Since only the current signal is used which is available in several locations, the method is simple and can be applied online. The method uses wavelet to determine the capacitor switching instant, which is needed for the ANFIS model to locate the switching capacitor. The method is simulated using PSCAD. Through various simulations, it is shown that other power quality disturbances such as voltage dip, unbalances and harmonics cannot disturb the method. Moreover, the size and connection type of the capacitor bank do not affect the method accuracy. The proposed algorithm is validated by simulating the IEEE 13-bus distribution system. According to the simulation results, the method is reliable enough to be applied to real systems. [ABSTRACT FROM AUTHOR]

In this paper, a multi-objective function is proposed for optimal placement of the capacitors in radial distribution networks considering the effect of harmonics. In addition to the voltage profile, active losses and installation cost, the resonant phenomenon caused by the harmonics is also included in proposed objective function. The PSO meta-initiative method has been employed in order to optimize the function. A novel approach has been introduced to analyze the harmonic load flow in distribution networks. The proposed method is based on four matrices that are constant during the load flow. Therefore, in this method, the repeater counters and the harmonic frequencies are the only variables. Due to the elimination of backward-forward sweeps in this approach, the calculations are fast and accurate. This method has been implemented on a standard 14-bus system and a real power distribution network in Lorestan province, Iran. Simulation results confirm the accuracy and speed of the proposed load flow method as well as the effectiveness of the proposed method for optimal placement of the capacitors in the harmonic polluted networks. [ABSTRACT FROM AUTHOR]