Ahmet Mete Vural

Steady state analysis of unified power flow controller: mathematical modeling and simulation studies

This paper presents an improved steady state mathematical model for unified power flow controller (UPFC), which is necessary for the analysis of the steady state operation of this device embedded in a power system. The model is based on the concept of injected powers in which the operational losses can be taken into account. The model is quite suitable in load flow studies, since it accepts employing conventional techniques such as Newton-Raphson method and even commercial software. The model is verified through a number of simulation examples, carried out on IEEE 14-bus and IEEE 30-bus systems by commercial software in which the model is adapted by means of user-defined modeling technique. The results of load flow analysis show the effectiveness of the model. Also the effects of UPFC location on different power system parameters are entirely investigated.

Optimization of parameter set for STATCOM control system

STATCOM controlled power system shows highly non-linear characteristics. In such a structure, linear controllers are easy to apply but difficult to tune. Fine tuning of controller parameters is necessary to meet transient performance requirements. In this paper, control system parameters of a STATCOM which is constructed from two six-pulse voltage source based converters are optimized by Simplex algorithm which is a non-linear and non-gradient method. System objective function to be minimized is based on a performance index and expressed in terms of measured and desired values of system variables. After optimization, performance of STATCOM control system consisting of two PI controllers and two leag/lag compensators has been tested and verified through a number of simulation studies investigating step-response performance. Precise and quick responses have been observed with optimized parameters.

Quasi-multi-pulse voltage source converter design with two control degrees of freedom

In this article, the design details of a quasi-multi-pulse voltage source converter (VSC) switched at line frequency of 50 Hz are given in a step-by-step process. The proposed converter is comprised of four 12-pulse converter units, which is suitable for the simulation of single-/multi-converter flexible alternating current transmission system devices as well as high voltage direct current systems operating at the transmission level. The magnetic interface of the converter is originally designed with given all parameters for 100 MVA operation. The so-called two-angle control method is adopted to control the voltage magnitude and the phase angle of the converter independently. PSCAD simulation results verify both four-quadrant converter operation and closed-loop control of the converter operated as static synchronous compensator (STATCOM).

Hybrid Fuzzy PI-Control Scheme for Quasi Multi-Pulse Interline Power Flow Controllers Including the P-Q Decoupling Feature

Real and reactive power flows on a transmission line interact inherently. This situation degrades power flow controller performance when independent real and reactive power flow regulation is required. In this study, a quasi multi-pulse interline power flow controller (IPFC), consisting of eight six-pulse voltage source converters (VSC) switched at the fundamental frequency is proposed to control real and reactive power flows dynamically on a transmission line in response to a sequence of set-point changes formed by unit-step reference values. It is shown that the proposed hybrid fuzzy-PI commanded IPFC shows better decoupling performance than the parameter optimized PI controllers with analytically calculated feed-forward gains for decoupling. Comparative simulation studies are carried out on a 4-machine 4-bus test power system through a number of case studies. While only the fuzzy inference of the proposed control scheme has been modeled in MATLAB, the power system, converter power circuit, control and calculation blocks have been simulated in PSCAD/EMTDC by interfacing these two packages on-line.

Modeling and intelligent control of a stand-alone PV-Wind-Diesel-Battery hybrid system

This paper presents a study of the modelling and intelligent control of a stand-alone hybrid energy system based on solar-wind-diesel with battery. In this study as the proposed system operate in a standalone mode the power quality is expected to decrease by the fluctuations from each of the voltage and frequency with varying loads and each of the two renewable sources which have depended on the wind speed, and solar radiation and temperature. This can be solved, by controlling the Pulse Width Modulation (PWM) of Voltage Source Converter (VSC) as modelled with Battery Energy Storage System (BESS). Consequently, it is of great interest the operation and intelligent control of the aforementioned systems for certain normal, and abnormal operating conditions. Furthermore, the other aim of this work is to design this control by soft computing techniques such as fuzzy logic and PI controllers have been adopted in Matlab/Simulink to simulate the outcomes, and choosing a suitable controller with proposed modelling hybrid system, as more as robustness; By compare the dynamic performances of PI and the fuzzy controllers through the study of the voltage and frequency control of the micro-grid under disturbances, moreover, to express and verify a much more capable, precise and robustness between these two types of controllers to quickly repair and stabilize the micro-grid during events such as the islanding.

STATCOM Estimation Using Back-Propagation, PSO, Shuffled Frog Leap Algorithm, and Genetic Algorithm Based Neural Networks

Different optimization techniques are used for the training and fine-tuning of feed forward neural networks, for the estimation of STATCOM voltages and reactive powers. In the first part, the paper presents the voltage regulation in IEEE buses using the Static Compensator (STATIC) and discusses efficient ways to solve the power systems featuring STATCOM by load flow equations. The load flow equations are solved using iterative algorithms such as Newton-Raphson method. In the second part, the paper focuses on the use of estimation techniques based on Artificial Neural Networks as an alternative to the iterative methods. Different training algorithms have been used for training the weights of Artificial Neural Networks; these methods include Back-Propagation, Particle Swarm Optimization, Shuffled Frog Leap Algorithm, and Genetic Algorithm. A performance analysis of each of these methods is done on the IEEE bus data to examine the efficiency of each algorithm. The results show that SFLA outperforms other techniques in training of ANN, seconded by PSO.

Modeling and simulation of Bazyan Gas Power Plant

This paper presents a study about the modeling and simulation of Bazyan Gas Power Plant. The request of energy in the developing regions of the world has testify pronounced increase in the recent past. Thus, it is important to use power generations that have high efficiency and specific power output, low emissions of pollutants, and low operating and maintenance cost for a possible use of available fuels. Industrial gas turbines are one of the well-established technologies for power generation. Therefore, the gas turbine power plant has guaranteed a notable place in electric utility systems. Power system stability studies need the exact models of power system elements. Exciter, speed control, and gas turbine are important components of the generating units. First, each part of the turbine is described by its transfer function, and then block model is built thoroughly. In addition to the turbine, excitation system is of IEEE AC7B type with power system stabilizer (PSS2B), a synchronous generator and Transformer are considered in emulate modeling. This model is then adapted to the newly installed Gas Power Station in north of Iraq called Bazyan Gas Power Plant (BGPP), using real data from the datasheets of BGPP manufactures. For the simulation, the station is connected to a load. Simulation studies are performed under small signal disturbance such as a step change in governor input, as well as large disturbance conditions such as line-to-ground and three-phase faults. At each step, various system variables such as rotor angle, acceleration power, terminal voltage and rotor speed are recorded and plotted. Based on the results, appropriate recommendations are made.

Modeling of modular multilevel converter based high voltage direct current transmission system

The modular multilevel converter (MMC) is a trending topology that has revolutionized voltage source converter (VSC) based high voltage direct current (HVDC) transmission. In this paper a MMC based VSC-HVDC transmission system has been modeled, designed and simulated under balanced three-phase operation in semiconductor based time-domain simulation environment. MMC based VSC-HVDC transmission system has been positioned between two separate large generation centers to provide real power flow control and reactive power/voltage control at AC terminals of both converters. MMC has been preliminary designed using five half-bridges at each arm. An efficient modulation strategy for the switching of IGBT switches has been decided and verified. The dynamic responses of the controllers of the MMC based VSC-HVDC transmission system have been evaluated to draw some conclusions at the end of the study.