Yasin Kabalci

On the Nakagami-m Inverse Cumulative Distribution Function: Closed-Form Expression and Its Optimization by Backtracking Search Optimization Algorithm

The inverse cumulative distribution function (CDF) is utilized in several areas such as statistical applications, Monte Carlo methods and communication systems. In wireless communications, the Nakagami-m inverse CDF is widely used to obtain outage probabilities of systems. However, calculation of the Nakagami-m inverse CDF is troublesome and there is no a closed-form expression. Simpler and more accurate approximation for the Nakagami-m inverse CDF is derived in this paper. Moreover, coefficients of the proposed approximation are optimized by using backtracking search optimization algorithm which is a new evolutionary algorithm to solve optimization problems. The obtained results show that the proposed approximation and exact values of the Nakagami-m inverse CDF are in well agreement for all cases.

The low cost voltage and current measurement device design for power converters

The sensing circuits are very important devices to measure for both current and voltage magnitudes of the systems. This paper presents a new sensing circuit design with significant advantages for DC voltage systems. The proposed sensing circuit is capable to measure currents and voltages by means of one current transducer and resistor network of voltage measurement. The accuracy and reliability of the proposed circuit are ensured by employing operational amplifier that can detect μV-level voltage variations at the differential inputs. Moreover, the proposed system is checked against to the previously one reported by authors in terms of overall cost, superiorities and drawbacks. The performed experimental studies showed that the proposed sensing circuit offers several significant advantages such as very low cost, very high accuracy and very low power supply requirements with respect to the formerly designed system.

A low cost smart metering system design for smart grid applications

The most important parts of the smart meters are the sensing devices that are utilized to measure for both current and voltage magnitudes of the systems. Therefore, several investigations have to be carried out to improve practical applications of the smart metering systems. This paper presents a novel sensing device design for AC measurement systems. The proposed sensing system is firstly designed by means of the computer simulation tools and then the printed circuit board of the designed metering system is implemented. Afterwards, the practical circuit is tested under different conditions. In addition, the proposed system is compared with the previously designed sensing circuit by authors in terms of cost, advantages and disadvantages. The obtained results emphasized that the proposed new sensing circuit is capable of very low cost and very high accuracy.

Dual DC-DC converter and monitoring interface for asymmetrical string inverters

This paper proposes monitoring of the dual dc-dc converters that independently operate of each other in the same topology (Buck-Boost). The dual converter structure is proposed to implement asymmetrical string inverter that is intended to be used variously arranged PV strings. The converters are operated by independently running MPPT algorithms. The converters are supplied by programmed dc sources emulating freely arranged solar arrays, and different loads are connected to each converter output. The converters allow using independent power sources like hybrid power techniques owing to these features. Current and voltage sensors measure the output powers of each converter, where the obtained values are evaluated by P&O algorithm on MCU and the PWM signals are generated. At the same time, obtained values are transmitted to computer by a microcontroller on optically isolated UART to USB unit. The received values are saved in a database to enable historical and instant analyse capability of the converters.

A single-axis solar tracking system and monitoring software

In this paper, the application of a portable solar tracking system is implemented to increase energy generation of the photovoltaic (PV) panels. While this portable system provides the monitoring of the maximum solar radiation values, the creation of more efficient solar tracking system is also another significant contribution. Thus, a system which continuously records and monitors the generated voltage, solar irradiation value and the panel position is proposed. The voltage, actual panel direction and irradiation data is continuously read by the improved control circuit and transmitted via Radio Frequency (RF) communication to the data collection card connected to the computer. The data received by the data acquisition cards is sent to the computer via Universal Serial Bus (USB) communication protocol. These data are monitored through the interface coded in computer and also recorded in the database. Thus, the retrospective irradiation and voltage information obtained by monitoring system performance can be monitored by the proposed system.

Dual DC-DC converter design for string inverters used in solar plants

This study deals with the design of a dual buck converter where both of them are simultaneously operated to regulate photovoltaic (PV) string inputs. The proposed control and converter structure is intended to improve the dc-bus interface for solar arrays and to control the dc bus voltage of a commercial grid-tie inverter that is generated by four PV arrays. The control algorithm is improved by including PI control to the regular perturb-and-observe algorithm. Regarding to the international standards on single-phase commercial string inverters such as AS4777-2013, IEC62109, and IEC61727, the maximum power of each solar array is allowed to be 1.2 kWp while the maximum total input power is limited to 4.8 kWp. Individual MPPT controllers that are improved in this study control each one of the dc converters handling dual solar arrays at the input connection. The dc interface voltages regulated by converters are coupled on a unique dc bus to generate the supply voltage of inverter section. The controllers perform a robust operation against the freely fluctuating irradiation values of each solar arrays.

Single phase multilevel string inverter for solar applications

The proposed study deals with modeling and implementation of a multilevel string inverter with non-isolated dc-dc converter design. The modeled system is intended to be used for solar applications that the photovoltaic panels are connected in string structure. However, the dc-dc converter and multilevel inverter are capable to be used in distributed energy generation applications owing to the proposed control infrastructure. The entire design includes dual buck converter at the dc coupling input where both of the converters simultaneously operate to regulate photovoltaic string voltages. Each dc converter is capable to manage a string comprised of two photovoltaic arrays at the input. The maximum power of each solar array is allowed to be 1.2 kWp while the maximum value of total input power is limited to 4.8 kWp regarding to the related international standards such as AS4777-2013, IEC62109, and IEC61727. The output voltages of dc converters are set to 120V by the proportional-integral controller and are coupled over dc busbar to supply 9-level string inverter. The multilevel string inverter is comprised of two H-bridges in symmetrical topology where it is arranged according to regular 5-level symmetrical inverter. Furthermore, the regular sinusoidal pulse width modulator is enhanced to increase voltage level of inverter to nine instead of regular 5-level output. The inverter provides unity power factor with 0.63% total harmonic distortion ratio.

Introduction to Smart Grid Architecture

The smart grid that is a new concept introduced at the beginning of the 2000s intends to include bidirectional communication infrastructure to conventional grids in order to enable information and communication technologies (ICTs) at any stage of generation, transmission, distribution, and even consumption sections of utility grids. This chapter introduces essential components and novel technologies of smart grids such as sensor networks, smart metering and monitoring systems, smart management systems, wired and wireless communication technologies, security requirements, and standards and regulations for this concept. First of all, this chapter focuses on the main components of smart grids such as smart sensors and sensor networks, phasor measurement unit (PMU), smart meters (SMs), and wireless sensor networks (WSNs). Then, smart grid applications and main requirements are explained on the basis of advanced metering infrastructure (AMI), demand response (DR), station and substation automation, and demand-side management (DSM). Later, communication systems of smart grid are presented in which the communication systems are classified into two groups as wired and wireless communication systems, and they are comprehensively analyzed. Furthermore, the area networks related to smart grid concept such as home area network (HAN), building area network (BAN), industrial area network (IAN), neighborhood area network (NAN), field area network (FAN), and wide-area network (WAN) are presented in a logical way beginning from generation systems to the user side.

A new approach based on differential evolution algorithm for harmonic estimation problems

Electrical harmonic is an important issue affecting power quality of electrical systems. Estimation of power harmonics are essential to design filters to be utilized in electrical power systems for reducing harmonics and their effects on the electrical power systems. In this study, a harmonic estimator based on differential evolution algorithm is proposed for harmonic estimation problems shown in power systems. Analyses of designed estimator are performed for two different experiments. In addition, performances of proposed estimator are compared with available results of the literature. The achieved results of this study showed that the proposed harmonic estimator in this paper is superior among previously reported ones.

Remote monitoring system design for photovoltaic panels

The design and implementation studies of a remote monitoring system are presented in this study. The proposed design is improved in terms of smart metering infrastructure based on current, voltage, and power measurements. The communication among the photovoltaic (PV) panels and host PC is performed by designed ZigBee transceiver system. Sensing circuits are very important devices to measure for both current and voltage magnitudes of electrical systems. The measured data are processed by the microcontroller unit (MCU) and are modulated after signal processing operations for wireless transmission. Although the transceiver is configured to execute bi-directional communication, unidirectional data flow is performed where the smart metering system transmits data to monitoring substructure. The monitoring software is also implemented in the context of the presented study. The Visual Studio.Net software development kit is used to design and to code the software. The performed experimental studies showed that the proposed real time monitoring and smart metering system could be exploited to monitor current, voltage and power magnitudes of the PV panels in an efficient way.