Ayhan Ozdemir

A digital adaptive filter for detecting harmonic, active and reactive currents

There have been a number of harmonic and reactive current-detecting methods for active power filters. All of these methods suffer from limitations such as being computationally costly or being sensitive to environmental changes. In this study, a computationally simple digital adaptive detecting filter that is insensitive to environmental changes is proposed. First, some digital and analogue adaptive methods developed recently are reviewed, comparing their abilities. Second, a digital adaptive filter is proposed that overcomes the limitations of the previous methods. Third, the transfer function of the filter is obtained, and its validity is illustrated via computer simulations. Finally, the feasibility of the filter is also demonstrated in the time domain. The simplicity of the proposed approach makes it suitable for real-time applications by using a digital signal processor or a mixed-signal microcontroller.

Hardware-based simple, fast and accurate measurement of power system frequency using a hybrid system

All digital methods developed for frequency measurement suffer from one or more factors such as superimposed noise, non-linear static characteristics, high-order harmonics and slow response because of complex computations. The measurement speed of conventional analogue methods is constant and depends on the input signal frequency. Additionally, as a result of deviated and/or spurious zero-crossings caused by the DC component, noise and high-order harmonics in the AC waveform, it is hard to attain the desired accuracy with conventional analogue methods. In this study, a phase-locked loop and microcontroller-based hybrid frequency measurement method developed by the modification of conventional zero-crossing is presented. The input signal, with harmonics and noise, and the frequency can be measured in a fast and accurate way with the proposed method, whose real-time application is extremely simple; this is demonstrated in a comparable manner to the studies in the literature. The measurement method presented in this study is fast, cheap, reliable, accurate and suitable for real-time applications.

An application study about SMPS design and reduction of common mode noises

A switched-mode power supply (also called as switching-mode power supply, SMPS, or simply switcher) is an electronic power supply unit (PSU) that incorporates a switching regulator. This paper investigates SMPS design and a filter solution for common mode noises. At first, the design of an SMPS which has three outputs has been presented after that common mode noises have been determined and then these noises have been tried to be reduced by the filter. The experimental studies have shown that there is a considerable reduction in common mode noises thanks to designed filter.

Design of model-refence discrete-time sliding mode power system stabilizer

Power system stabilizers (PSSs) improve the dynamic stability of power systems by increasing the damping torque of the synchronous machines in the system. Over the last four decades, various approaches for the design of PSSs have been reported in the literature. Sliding mode controller is one of these approaches which has some advantages, such as the parameter insensitivity and the realization simplicity, over the other approaches. In this paper, as a new approach for design of the PSS, a model reference discrete time sliding mode controller (MRDSMC) is presented. The effectiveness and the robustness of the proposed MRDSMC based PSS is demonstrated by a number of studies. Similation results show that the proposed PSS performs better for less overshoot and less settling time compared with the conventional and LQR based stabilizers under normal load operation and the significant system parameter variation conditions.

Double-loop PI controller design of the DC-DC boost converter with a proposed approach for calculation of the controller parameters:

Parameters of digital proportional–integral/proportional–integral–derivative controllers are usually calculated using commonly known conventional methods or solution of discrete-time equations. In literature, a model-based compact form formulation for calculation of discrete-time proportional–integral/proportional–integral–derivative controller parameters has not been come across yet. The proposed model-based compact form formulations are introduced to calculate the proportional–integral parameters in discrete time as a new approach. Generally, different types of control techniques are chosen in similar studies for double-loop control for direct current–direct current boost converter control except proportional–integral/proportional–integral. In this study, double-loop proportional–integral controller is used as a different control method from literature. By this way, the most important advantages of the proposed study are to reduce different design methods to a unique proportional–integral design method and shorten all calculations. The accuracy of the double-loop proportional–integral controller’s parameters calculated using the model-based compact form formulations is validated both in simulation and experimental studies under various disturbance effects. Satisfactory performance of the proposed controller under model uncertainty and other cases are comparatively shown with the predefined performance criteria.

Real time implementation of a digital controlled boost converter

This paper presents real time implementation of a digital controlled conventional boost converter works on the fixed frequency driven by the duty cycle control techniques. The digital controller, implemented using ADUC841 microcontroller, monitors the output voltage and calculate the error to determine the next duty cycle value. Simulation and experimental results indicates that the constructed PI controlled boost converter have good transient response as well as stable and accurate steady-state response during the drastically changes occur in input voltage and output load.

Real time implementation of hybrid sine wave reference generator based on PLL and DLT

A sine signal synchronous to the power system voltage signal is required in most power electronics based industrial applications. In this study, a phase locked loop (PLL) and direct look-up table (DLT) based hybrid sine oscillator is developed, and sinusoidal signals of the desired frequency that is synchronous to the reference input signal is generated in real time applications carried out with the developed oscillator.