Hasen, Suud Ademnur; Aydın, Ömer; Ayasun, Saffet; Sönmez, Şahin

The utilization of communication linkages generates delays that degrade system dynamic performance and cause fluctuations in the system frequency while the extensive integration of renewable energy sources may cause further increase in the frequency oscillations owing to low inertia. By considering the inclusion of the virtual inertia and damping (VID) control in load frequency control (LFC) systems with time delays, this article investigates the impacts of the VID control on the stability delay margins (SDMs) of two-area LFC systems. For this purpose, an exact method, which is based on recursively removing exponential terms from the characteristic equation, is first implemented to compute SDMs of the two-area LFC system enhanced by VID control for a wide range of controller gains. Secondly, the effect of the VID parameters on the SDMs is investigated by employing the exact method. Theoretical results clearly illustrate that SDMs significantly increase as VID parameters increase. Furthermore, simulation analysis elucidates that with the VID incorporation, the performance of the LFC system with low inertia is enhanced and the rate of change of the frequency and frequency nadir are remarkably decreased, improving the stability of time-delayed LFC systems.

Yesilyurt, Huseyin; Sahin, Yakup; Ting, Naim Suleyman

This paper proposes a soft-switching (SS) active snubber cell for half-bridge (HB) DC–DC converters, which are utilized in hybrid vehicle battery charge applications. The proposed converter has an advantage over conventional HB DC–DC converters, which suffer from transformer leakage inductance issues. The new snubber cell performs SS operation using the energy stored in the leakage inductance. Thus, the leakage inductance, which creates troubles for HS DC–DC converters, is beneficial to the proposed converter. The proposed SS HB DC–DC converter is compared with the conventional HB DC–DC converter under 100 kHz and 110 W output power operating conditions. The efficiency of the proposed converter is 7.3% and 4.8% higher than the conventional HB converter at light and heavy loads, respectively. The proposed active snubber cell provides complete SS for the main and auxiliary semiconductor switches. The new snubber cell has a basic structure, low-cost, ease of application, and simple control features.

Bodur, Haci; Yesilyurt, Huseyin; Akboy, Erdem; Ting, Naim Suleyman

This paper introduces a novel modular active snubber cell for isolated half-bridge converters with ease of control. The novel snubber cell can achieved soft switching for all semiconductors at the proposed converter. The switches in the converter are derived simultaneously by the normal pulse-width modulation signals. The introduced snubber cell has a quite simple structure and ease of control. In this converter, the main switches turn on with zero current switching and turn off with zero voltage switching. Besides, there is no extra voltage stresses on the power elements. The proposed half-bridge DC–DC converter is analyzed in detail and its theoretical analysis is verified with a prototype having 50 A–25 V output values at 80 kHz frequency.

Ting, Naim Suleyman; Sahin, Yakup; Yetgin, Halil

Interleaved boost converter (IBC) is equal to two-boost converter operating in parallel. IBCs are more advantageous than conventional boost converters. Input current of the interleaved converter is less fluctuated compared to that of the boost converter. In this paper, a new IBC structure is introduced unlike the conventional IBC structure. In the presented converter, the place of output filter capacitor is changed unlike the conventional IBC and thus, the voltage across the output filter capacitor is reduced about Vi. The proposed IBC performs similar experimental results compared to that of the conventional IBC. Besides, the proposed IBC enables the utilization of an output filter capacitor even with lower voltage, and thus the cost of IBC is reduced. The analysis of operating stages of the presented converter is conducted for D < 50% and D > 50% modes. Finally, an experimental setup of the presented converter is realized along with the parameters of 640 W and 20 kHz.

Sahin, Yakup; Ting, Naim Suleyman

In this paper, a novel soft switching passive snubber cell for family of isolated/non-isolated pulse width modulation DC–DC converter is proposed. In this proposed converter, the switch is turned on with zero current switching (ZCS) and is turned off with zero voltage switching (ZVS). Besides, the main diode is turned on and off with ZVS and ZCS, respectively. In addition, the reverse recovery losses of main diode are minimized. The auxiliary diodes in the snubber cell are operated with soft switching. The proposed converter has a simple structure, low cost and ease of application. The detailed theoretical analysis of new converter is made, and a 200-W laboratory prototype is implemented. The theoretical analysis is confirmed with the experimental results. Finally, the proposed passive snubber cell is applied to family of other isolated/non-isolated DC–DC converter in order to provide soft switching.

Can, Erol; Sayan, H. Hüseyin

In the paper, Step sinus pulse width modulation (SSPWM) three phase inverter is tested on a nonlinear device which can produce harmonics. There are 12 switches on active and passive cases. On the inverter, operations of switches are provided by arranged SSPWM which can be calculated with similarity rules of triangles. A mathematical model of inverter is obtained with operating characteristics of the switches determined. SSPWM technique is used to control non-linear devices as thyristor and rectifiers which are widely used in electronic systems. So, single phase alternating voltage is converted to direct voltage with rectifier circuit to provide input voltage of inverter. After that, Six switches of common three phase inverter model are connected to six thyristors controlling inputs and outputs of three phase loads so that performance of SSPWM can be investigated on high level harmonic of loads. The inverter load of resistive (R) and inductive (L) are performed at the MATLAB Simulink so that SSPWM technique could be showed the reducing effect of the harmonic on loads. So, SSPWM and SPWM controlling inverter are performed on frequencies. Then, performances of common SPWM and SSPWM running nonlinear loads are compared with results.

Can, Erol

This paper presents a novel high multilevel inverter topology which is based on the created DC voltage levels at loads of the inverter. The circuit model is demonstrated by explaining the relationship between switches, sources and loads. According to the proposed inverter topology, the number of power switches connected to negative side of DC source is constant on inverter, while the number of power switches connected to positive side of DC sources is increasing. Therefore, linear pulse-width modulation (LPWM) is described for operating switches after pulse-width modulation method is developed to generate the PWM signals. Then, mathematical equations are given when resistive (R), inductive (L) and capacitive (C) loads are connected in series on a 9-level inverter. Finally, the performances of the proposed inverters are observed through MATLAB/SIMULINK simulations after the designed multilevel inverters are simulated. So, 6-level, 9-level and 11-level inverters are compared with voltages, currents and harmonic distortions. Harmonic distortions reduce with increasing level of inverter, while three multilevel inverters are investigated on different modulation indexes. The results demonstrate the satisfactory performance of the inverter and verify the effectiveness of a novel high multilevel inverter topology.