M. Davari

A new nonlinear controller design using average state space model of the inverter-based Distributed Generation to mitigate power quality problems

The controller of Voltage Source Inverter (VSI) is the essential part of Distributed Generation (DG) system as an interface in solving the power quality problems. In this paper, a new controller (Based on Feedback Linearization) has been proposed due to achieving some prescribed behavior to mitigate the power quality problems. The new controller has been designed base on the average state space model of VSI and network which is nonlinear. The real time simulation of the proposed system shows precise tracing the load requirements and good mitigating the power quality problems rather than previous studies.

Determination of mean and variance of LMP using probabilistic DCOPF and T-PEM

The Locational Marginal Pricing (LMP), calculated based on deterministic load flow and Optimal Power Flow (OPF), is used in power markets studies. In this paper, an algorithm has been proposed to calculate the mean and variance of LMP. The proposed method is based on Two Point Estimate Method (T-PEM). The probabilistic LMP can be used to have a good estimation for LMP.

Multifunction current controller for inverter-based distributed generation using combined pi-sliding mode controller via Sigma-Delta Modulation

The fast changes in the reactive power consumption can cause considerable variations at the load-side and can influence on the operation of other power consumers which and Point of Common Coupling (PCC) voltage. In this paper, a current control strategy based on Sigma Delta Modulation (ΣΔM) is presented for the interfacing DG inverter. The inverter is called Sigma-Delta based Current Controlled Voltage Source Inverter (ΣΔ_CC_VSI). It controls active and reactive powers independently with fast voltage regulation. It is shown that the ΣΔM generates sliding mode regime. As a result, it is possible to combine the Proportional-Integral (PI) with sliding mode controllers. It is shown that the proposed ΣΔ_CC_VSI reduces the harmonics amplitude variations of the unfiltered voltage. Therefore, it reduces the ElectroMagnetic Interference (EMI) problems.

Using Fuzzy ARTmap neural network for determination of partial discharge location in power transformers

Techniques for locating a partial discharge source are of major importance in both the maintenance and repair of a transformer. This paper presents a novel approach to identify partial discharge locations in transformer winding using neural network. In this paper for simulation and detection of partial discharge, detail model of transformer is used. With modeling of partial discharge impulse source in EMTP software, this phenomenon is implemented in different points of transformer winding. Then produced current in both ends of winding is measured and use for training and test of neural network. In actual, obtained current signals is with noise. Thus in this paper the performance of the Fuzzy ARTmap neural network for correct determination of partial discharge location in power transformer with considering different noises on simulated current signals for simulation of actual conditions is surveyed. The most important characteristics of neural networks are capabilities to learning and predict the various patterns and other is capability to provide a fast responsible for input patterns. The neural network used here for simulation patterns trainings and testing of the partial discharge in power transformer winding is Fuzzy ARTmap.

Analysis and comparison of the lightning overvoltage in the AC connected and VSC based HVDC connected wind farms

As Wind Turbine (WT) generation has been explosively introduced worldwide, the problems in the wind farm has been brought up. In this paper any kind of wind farm configurations and connections, include AC transmission system and VSC based HVDC transmission system are considered and the general tendency in lightning overvoltage at wind farm and lightning overvoltages of valve in VSC based HVDC based wind farm are analyzed and discussed. Also the dv/dt protection of valve is considered. For overvoltage simulation EMTP software is used. This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.

A novel approach to VFTO analysis of power transformers including FVL based on Detailed Model

There are two physical models to analyze Very Fast Transient Overvoltage (VFTO) on transformers. These models are multiconductor transmission-line model and Detailed Model. The modeling of windings by the lumped RLCM network (the detailed model) enables the calculation of the currents and voltages using common electrical network analyzing tools (e.g., ATP, Pspice, etc.). In addition, it is possible to consider nonlinearities (e.g., hysteresis, saturation) and frequency dependent effects (e.g., eddy current, dielectric losses). Complex windings can be modeled with several coils, which is not possible for the multi-phase transmission line model. This paper is proposed a complete Detailed Model (DM) that is consisting of Frequency Variable Losses (FVL) and comparison of its results with experimentally results shows that it can be used to analyze the VFTO on transformer easily.

Optimal tuning of multifunction current controller for Sigma Delta Modulation inverter-based distributed generation using PSO method

There are many consumers and equipments in Distributed Generation (DG) systems and distributed networks which have rapid changes in the reactive power consumption. These changes can result in large variations in the load-side voltage that may affect the operation of other power consumers which are fed from Point of Common Coupling (PCC). In this paper a current control strategy for inverters, based on Sigma Delta Modulation (SDM), interfacing with DG systems is proposed. The proposed interface is called Sigma-Delta based Current Controlled Voltage Source Inverter (ΣΔ_CC_VSI). Due to existing number of proportional integral (PI) controller, a particle-swarm optimization (PSO) method has been employed for best tuning the controllers. The proposed ΣΔ_CC_VSI reduces the harmonics contents of the unfiltered voltage. So it is effective in reducing the ElectroMagnetic Interference (EMI) which is important for some consumers.

Modeling the combination of UPQC and photovoltaic arrays with Multi-Input Single-Output DC-DC converter

In this paper analysis results of a cooperation of the Unified Power Quality Conditioner (UPQC) with the photovoltaic system are presented. The proposed system consists of a series inverter, a shunt inverter, and some photovoltaic arrays connected in the dc link through the Multi-Input Single-Output (MISO) DC-DC converter. A numerical formulation of the proposed control schemes, which are based on the instantaneous power theory, is presented. The proposed system can improve the power quality at the Point of Common Coupling (PCC) on power distribution systems. The performance of the proposed system was analyzed using simulations with Power System Computer Aided Design/ElectroMagnetic Transients DC (PSCAD/EMTDC) analysis program.