Samet Biricik

Optimized Sliding Mode Control to Maximize Existence Region for Single-Phase Dynamic Voltage Restorers

This paper presents an optimized sliding mode control (SMC) strategy to maximize existence region for single-phase dynamic voltage restorers. It is shown analytically that there exists an optimum sliding coefficient which enlarges the existence region of the sliding mode to its maximum. Also, it is pointed out that the optimum sliding coefficient improves the dynamic response. In addition, a double-band hysteresis control which ensures the switching of a transistor in the voltage source inverter during a half-cycle while it remains either on or off in the other half cycle is used to mitigate the switching frequency. The theoretical considerations and analytical results are verified through computer simulations and experimental results. Simulation and experimental results show that the proposed SMC strategy not only compensates the undesired voltage disturbances and maintains the load voltage at desired level with low total harmonic distortion, but also exhibits fast dynamic response and operates at reasonably low switching frequency.

Time-Varying and Constant Switching Frequency-Based Sliding-Mode Control Methods for Transformerless DVR Employing Half-Bridge VSI

This paper presents time-varying and constant switching frequency based sliding-mode control (SMC) methods for three-phase transformerless dynamic voltage restorers (TDVRs) which employ half-bridge voltage source inverter. An equation is derived for the time-varying switching frequency. However, since the time-varying switching frequency is not desired in practice, a smoothing operation is applied to the sliding surface function within a narrow boundary layer with the aim of eliminating the chattering effect and achieving a constant switching frequency operation. The control signal obtained from the smoothing operation is compared with a triangular carrier signal to produce the pulse width modulation signals. The feasibility of both SMC methods has been validated by experimental results obtained from a TDVR operating under highly distorted grid voltages and voltage sags. The results obtained from both methods show excellent performance in terms of dynamic response and low total harmonic distortion (THD) in the load voltage. However, the constant switching frequency-based SMC method not only offers a constant switching frequency at all times and preserves the inherent advantages of the SMC, but also leads to smaller THD in the load voltage than that of time-varying switching frequency-based SMC method.

New hybrid active power filter for harmonic current suppression and reactive power compensation

ABSTRACT In the case of undistorted and balanced grid voltages, low ratio shunt active power filters (APFs) can give unity power factors and achieve current harmonic cancellation. However, this is not possible when source voltages are distorted and unbalanced. In this study, the cost-effective hybrid active power filter (HAPF) topology for satisfying the requirements of harmonic current suppression and non-active power compensation for industry is presented. An effective strategy is developed to observe the effect of the placement of power capacitors and LC filters with the shunt APF. A new method for alleviating the negative effects of a nonideal grid voltage is proposed that uses a self-tuning filter algorithm with instantaneous reactive power theory. The real-time control of the studied system was achieved with a field-programmable gate array (FPGA) architecture, which was developed using the OPAL-RT system. The performance result of the proposed HAPF system is tested and presented under nonideal supply voltage conditions.

Voltage Sensorless Control of Single-phase Active Power Filter Based on the Second-order Generalized Integrator Algorithm

Abstract—A single-phase active power filter is presented for small-scale, single-phase loads based on the second-order generalized integrator control method is presented in this article. The proposed system does not require voltage sensors on the AC and/or DC side. Only two current sensors are used to measure load and converter currents. Consequently, a proportional-integral regulator is not used, and there is no need for additional calculations for the determination of the grid-current amplitude. To obtain the correct reference grid current, the distorted load current is first processed by using the second-order generalized integrator algorithm, which does not require voltage information. A step-by-step performance study, in a real-time environment, shows that the proposed control technique is able to generate the proper compensating reference current for small-scale non-linear loads. As a result, the total harmonic distortion of the grid current is reduced from 25.33 to 3.80%, which meets the recommended IEEE 519-1992 Standard.

Control of the Dynamic Voltage Restorer to improve voltage quality

In this study a method is proposed in order to improve the voltage compensation performance of Dynamic Voltage Restorer by using Self Tuning Filter. The proposed control method gives an adequate voltage compensating even for 50% voltage sag and distorted voltage conditions. The proposed DVR control method is modelled using MATLAB/Simulink and tested both in off-line and real-time environment. Results are then presented as a verification of the proposed method.

Improved harmonic suppression efficiency of single-phase APFs in distorted distribution systems

In this study, a control method is proposed to improve the harmonic suppression efficiency of the single-phase active power filter in a distorted power system to suppress current harmonics and reactive power. The proposed method uses the self-tuning filter (STF) algorithm to process single-phase grid voltage in order to provide a uniform reference grid current, which increases the efficiency of the system. The results of the simulation study are presented to verify the effectiveness of the proposed control technique in this study.

Performance evaluation of Serhatkoy (1.2 MW) PV power plant

Solar energy continues to play vital role in the delivery of clean and affordable source of generating electricity. Photovoltaic is the most promising technology amongst the types/methods of producing electricity from solar energy. The aim of this research is to evaluate the performance of Serhatkoy PV power plant (1.2 MW). Being the first grid-connected PV plant in north Cyprus, the results of this research will be useful in expanding the existing solar park or replicate same facility in locations with favorable weather conditions, evaluate the investments made, plan maintenance and estimate the efficiency of production. PVsyst software is used to model Serhatkoy PV power plant and simulation done to determine the performance ratio using meteorological data from NASA. Also the capacity factor (CF) and performance ratio (PR) are calculated. SAM formula proposed NREL is used to calculate the PR. The paypack period of the plant is also determined using exchange rate between Turkish lira and euro.

Sliding mode control strategy for three-phase DVR employing twelve-switch voltage source converter

In this study, a new method is proposed for the suppression of voltage amplitude fluctuations on the load terminals. Moreover, the voltage harmonics on the load terminals are effectively reduced below the defined limits in the IEEE-519 standard. In the studied topology, a twelve-switch three-phase voltage source converter is used for effective control on the zero-sequence components due to the unbalanced voltages or single phase voltage sags. In order to obtain a fast dynamic response, sliding mode control strategy is used to control the system. The existence condition of the sliding mode is presented. The performance of the closed-loop system is verified with cases of voltage sag and utility voltage harmonics. The overall system is explained in detail and verified by using MATLAB/Simulink.

Back diffusion of electrons in argon subjected to uniform time invariant orthogonal electric and magnetic fields

In this study, the processes of back diffusion in Ar subjected to crossed fields are analyzed by using the Monte Carlo simulation method in the E/N range of 50 to 500 Td (1 Td = 1 × 10–17 V cm2) for 0 < B/N < 25 × 10−19 T cm3. At a given constant E/N, escape factors decrease with an increasing crossed, reduced magnetic field B/N. This reduction in the escape factor is more pronounced in the lower E/N range. Furthermore, the mean number of collisions of back scattered electrons is quite large, and at a given E/N, the mean number of collisions decreases as the crossed B/N increases.

A Self-tuning Grid Synchronization Method for Active Power Filters

Abstract This article introduces a new configuration for grid synchronization to detect the positive-sequence component of the voltage under unbalanced and distorted conditions. The proposed configuration is based on the frequency-locked loop technique and combines a self-tuning filter with a conventional second-order generalized integrator. The introduced structure is able to produce two orthogonal output signals for detecting grid voltage information. More importantly, it behaves as a high-order filter to completely remove harmonic components and still reserves benefits from the previous second-order generalized integrator methods. The grid magnitude and frequency are identified accurately and then provided to the active power filter for proper operations. Simulation and experimental results are presented to verify the concept of the introduced method. In addition, the performances of the proposed and conventional configurations are compared to recognize the significant improvements and effectiveness in the new method.