Publications

This study proposes a new pulsed charging current technique to reduce aging and capacity losses in lithium-ion battery cells. The charging techniques developed to minimize aging and capacity losses are critical for battery cells with longer life cycles and higher energy efficiency. Continuous Current – Continuous Voltage charging (CC-CV), Positive Pulsed Current (PPC), and proposed Alternating Half Wave Pulsed Current (AHWPC) techniques were tested on a 12.8V-40Ah Li-ion battery. In PPC and AHWPC techniques, the pulse frequency of the charging current is chosen as f_(i_ch )=1 Hz. The average value of the charging current for PPC and AHWPC techniques is calculated based on the CC-CV technique. The aging and capacity losses caused by the three charging techniques in the battery were measured in five different scenarios: at various temperatures, different discharge currents, and different depths of discharge (DoD). Using the AHWPC technique, improvements of 45.93%, 46.57% and 46.29% were achieved in cell aging compared to the CC-CV technique at temperatures of 20°C, 30°C and 40°C, respectively. According to the results, the proposed AHWPC technique performed better than the PPC and CC-CV techniques in all test conditions.

Abstract This paper discusses a generic design of lithium‐ion (Li‐ion) batteries and supercapacitors, which are important sources for energy storage systems (ESS). The main contribution of this study is to compare the available and experimental models for batteries and supercapacitors operating under continuous charge or discharge conditions. Even though the available models show similar behavior to the experimental ones in short‐term or pulsed discharge conditions, this situation may be different in continuous discharge conditions. For this purpose, the optimal electrical equivalent circuits of energy storage devices were constituted and modeled in the MATLAB/Simulink environment. Then, the electrical equivalent circuit parameters were approximately calculated with the help of dynamic equations. Finally, the model parameters were estimated using Nonlinear Least Squares Method (NLSM) and Trust Region Reflective Algorithm (TRRA). When the obtained results were evaluated together, it has been observed that the electrical equivalent circuit models (EECM) more accurately reveal the transient and steady states of energy storage devices compared to the available models, especially under continuous discharge conditions.

In today's energy systems, many equipment operate with Direct Current (DC) voltage. However, it is not always possible to obtain the voltage level required for the operation of these equipment from standard power supplies. For this reason DC-DC converters are used to achieve the desired voltage values for equipment with different DC voltage levels. These converters are divided into three general categories, named Buck, Boost and Buck-Boost. The most preferred converter is the Cuk converter with low output ripple voltage, which can operate in both buck and boost modes. In this study, a detailed analysis of the Cuk converter, which is frequently used in Photovoltaic (PV) Panels was performed and different control methods of the output voltage were proposed. While performing this analysis, the dynamic model of the Cuk converter was created in which, Proportional-Integral (PI) and Fuzzy Logic (FL) are used to control the output voltage of the Cuk converter. The performances of both controllers were compared with respect to performance parameters such as steady state error, settling time and rise time. When the results obtained were evaluated as a whole, it was observed that FLC achieved the desired reference with less rise and settling time. In this study, modeling and controller applications of Cuk converter are realized by using MATLAB / SIMULINK program

Abstract Energy management in hybrid energy storage systems (HESSs) consisting of battery and supercapacitor packages has an essential role in the efficient and safe use of energy storage devices. In the mentioned HESSs, with frequency separation‐based energy management, the source with slow dynamics (eg, batteries) is supported by other sources with fast dynamics (eg, supercapacitors). To realize power sharing in the battery/supercapacitor HESS, the load current is divided into low‐ and high‐frequency components and supplied/allocated from energy storage devices. This review touches on the historical development of electric vehicles and includes extensive information about the battery and supercapacitor. It also comprehensively analyzes frequency separation‐based power allocation strategies for battery/supercapacitors HESS. These strategies were investigated in detail regarding their features, advantages, and restrictions. In addition, interconnection circuit topologies and control techniques used in frequency‐based power allocation were explained comprehensively. As a result, this study will serve as a guide on frequency‐based power separation principles in HESS.

ABSTRACT The proportional‐integral‐derivative (PID) controller is an important digital control structure that is frequently used by designers in many speed, position, and temperature applications. The main problem of such control structures is that the mathematical calculation burden is high and requires precise parameter determination. In this study, the control parameters were estimated to overcome the two main problems given above for the speed control of a Permanent Magnet Direct Current (PMDC) motor produced in real time. For this process, the Nonlinear Least Squares (NLS) optimization method with the Trust‐Region‐Reflective (TRR) algorithm, the Pattern Search (PS) optimization method with the Active‐Set (AS) algorithm, and the Simplex Search (SS) optimization method with the AS algorithm have been proposed. The proposed techniques are explained in detail, and the Sum of Square Error (SSE) is chosen as the objective function for these techniques. The predicted controller values for a single reference were tested under different speed, load, and armature resistance conditions. The speed control of the PMDC motor, which was created using the parameters estimated over the specified simulation periods, was tested with different load conditions. According to the results obtained, while the NLS‐TRR technique stands out in terms of calculation time, the SS‐AS technique outperformed in terms of precise parameter estimation.

This paper deals with the determination of the relationship between the power factor and the harmonic distortion in a single-phase AC (SPAC) voltage controller. The aim of this study is to investigate the change of power factor (PF) and total harmonic distortion (THD) during different phase triggering angles (PTA). Firstly, the advantages of using thyristor instead of triac in single-phase AC voltage controllers operating at high frequencies are mentioned. Secondly, the power factor and total harmonic distortions for single-phase AC voltage controllers are theoretically examined. Finally, the relationship between power factor and total harmonic distortion are demonstrated by both simulation and experimental studies. However, it is monitored that, at lower output voltages, the power factor (PF) is pretty much reduced and total harmonic distortion (THD) is significantly increased.

In this study, performance analysis of speed control of PMDC (Permanent Magnet Direct Current) motor using fuzzy logic controller was realized in Matlab/SIMULINK environment. Firstly, the mathematical model was obtained using the mechanical and electrical values of electrical equivalent circuit of the DC motor. Then, the fuzzy logic and PI controller structures was designed. Different references speeds were applied to the systems controlled by the FL and the PI controller. Additionally, in this study, the effect of varying armature resistance of the PMDC motor on the controller structures used in simulations and on the speed of the PMDC motor was also investigated. Comparisons were made for both controllers considering the same conditions. According to the results obtained by using the data in this study, it is observed that the fuzzy logic controller has a better performance than the PI controller.

This paper discusses comparative analysis of Buck-Boost and SEPIC (Single Ended Primary Inductance) converters used in DC link voltage control technique to reduce torque ripple in Brushless Direct Current Motors (BLDCM). The aim of this study is to prove the efficiency of the aforementioned two converters, which have been adopted in many studies to reduce torque ripples caused by commutation, on the same motor parameters. Although BLDCM has many advantages, ripples in the generated torque have limited the use of these motors in applications requiring precise speed and torque. In this study, BLDCM was analyzed exhaustive mathematically and electrically and the problem that caused commutation torque ripples was explained in detail. The DC link voltage control has been proposed to suppressing torque ripples in the BLDCM. In addition, the link voltages required for reducing the torque ripples were obtained separately via both the Buck-Boost and the SEPIC converters. These converter topologies are examined under certain speed and torque conditions and the results were compared. When the results are evaluated together, it was observed that both converters performed the very closely performance each other. However, the Buck-Boost converter produced the desired voltage levels with less oscillation than the SEPIC converter.

This paper proposes a new energy management strategy (EMS) for electric vehicles (EVs) with battery/supercapacitor hybrid energy storage systems (HESS). Firstly, the battery/supercapacitor HESS configuration and obtaining the load current from the driving cycle are comprehensively explained. Secondly, fixed and adaptive frequency-based (AFB) EMS are discussed in detail. In the proposed method, the current demanded by the load is separated into low and high-frequency components with the help of an adaptive low-pass filter (A-LPF). In addition, adaptive battery current (ABC) is generated according to the supercapacitor (SC) state of charge (SoC), and a double adaptive power allocation strategy is performed. The proposed method is compared with the AFB-EMS for load currents, load powers, DC link voltages, filter cut-off frequencies, battery, and SC SoCs on the UDDS driving cycle. When the obtained results were evaluated together, it was observed that the proposed method completed the driving cycle with a higher battery SoC and realized the adaptive cut-off frequency in a narrower band.

In the near future, seeing more than one energy storage device in mobile device power systems will be possible. Although Lithium-ion (Li-ion) battery cells in today's technology stand out with their high energy density and superior cell voltage advantages, they suffer from limited cycle lives. When high-power density ultracapacitors (UC) are combined with battery cells, a highly efficient hybrid power system can be created. However, since the cell voltages and power densities of these two energy storage devices are not equal, both the charge voltages and charge currents will be different from each other. This study proposes a single-input, multi-output cascade buck converter structure to charge battery and ultracapacitor cells synchronously. Converter parameters are calculated according to the charge powers of energy storage devices, and a cascade controller structure is designed for separate control of charge currents and cell voltages. The proposed synchronous charging system is tested using two different procedures: continuous current (CC) mode, where reference currents are closely monitored, and continuous voltage (CV) mode, where the charge voltage is limited. According to the results obtained, it was observed that the proposed system closely followed the reference currents in a short time of 6ms with a slight overshoot rate of approximately 8% in all tests.

The fluctuations in both speed and torque magnitudes during operation are among the major disadvantages of brushless DC motors. These fluctuations occur due to both the commutation of the inverter switches and the phase winding inductances. This case can lead to major problems, especially in applications which are required constant speed and constant torque. In this work, it was aimed to reduce speed fluctuations that occur in brushless DC motors. Firstly, the Matlab/SIMULINK model was created by using the dynamic equations of the brushless DC motor. Secondly, a region selective circuit was designed for use in commutation times. Finally, the commutation signals were generated from the magnitude of the torque produced by the motor. Consequently, the proposed technique was controlled under different speed conditions and was shown that the speed fluctuations can be reduced without the difficult calculations of the commutation time. According to the results obtained, it was observed that the speed fluctuations were significantly reduced.