Kamil Cagatay Bayindir

A robust control of dynamic voltage restorer using fuzzy logic

In this paper, a new control method for Dynamic Voltage Restorer (DVR) is described by combining fuzzy logic (FL) with a carrier modulated PWM inverter. The proposed control scheme is simple to design and has excellent voltage compensation capabilities. The proposed method for voltage sag/swell detection has the ability of detecting different kinds of power disturbances faster than conventional detection methods. Effectiveness of the proposed detection method is shown by the comparison with the conventional methods in the literature. Simulation results under unbalanced supply voltage are presented to evaluate the performance of the designed DVR.

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.

The Analysis and Performance Results of Bidirectional DC-DC Converter Based Dynamic Voltage Restorer under Voltage Sag/Swell Conditions

This paper presents Dynamic Voltage Restorer (DVR) based on bidirectional full-bridge dc-dc converter to compensate severe voltage sag/swell problems in medium voltage system. Voltage swell causes the continuous rise at dc-link voltage of DVR which may damage the dc-link capacitors and solid-state devices, and increase the power losses. Unidirectional dc-dc converters based DVRs do not allow power flow from dc link of inverter to battery. This condition may damage the dc-link capacitors and solid-state devices, and increase the power losses. The main contribution of this study is that bidirectional dc-dc converter permits the DVR to prevent voltage rise at DC link capacitor under severe voltage swell conditions. In this topology, power can flow both from battery to multilevel inverter and vice versa. For this propose, a control algorithm based on Proportional-Integrator (PI) control is developed for bidirectional dc-dc converter. This algorithm can keep the DC link voltage constant during voltage sag/swell. The performance results of proposed topology and control method is verified with PSCAD/EMDTC.

Design and implementation of full bridge bidirectional isolated DC-DC converter for high power applications

This paper proposes the design and implementation of a high power full bridge bidirectional isolated DC-DC converter (BIDC) which comprises of two symmetrical voltage source converters and a high frequency transformer. In the proposed BIDC, a well-known PI controller based single phase-shift (SPS) modulation technique is used in order to achieve high power transfer. Besides, different phase shift methods such as extended phase-shift (EPS) and double phase-shift (DPS) are compared with SPS. Both simulation and experimental results are caried out to verify PI controller based simple phase-shift controlled BIDC prototype that is designed for 300-V 2.4-kW and operating at 20 kHz.