In this paper, a new mode of operation has been introduced for packed U-cell (PUC) inverter. A sensor-less voltage control based on redundant switching states is designed for the five-level packed U-cell (PUC5) inverter, which is integrated into switching process. The sensor-less voltage control is in charge of fixing the dc capacitor voltage at half of the dc source value results in generating symmetric five-level voltage waveform at the output with low harmonic distortion. The sensor-less voltage regulator reduces the complexity of the control system, which makes the proposed converter appealing for industrial applications. An external current controller has been applied for grid-connected application of the introduced sensor-less PUC5 to inject active and reactive power from inverter to the grid with arbitrary power factor, while the PUC auxiliary dc bus is regulated only by sensor-less controller combined with new switching pattern. Experimental results obtained in stand-alone and grid-connected operating modes of proposed PUC5 inverter prove the fast response and good dynamic performance of the designed sensor-less voltage control in balancing the dc capacitor voltage at desired level.

/pdf/sensor-less-five-level-packed-u-cell-puc5-inverter-operating-p4q0nhs9nq.pdf

Sensor-Less Five-Level Packed U-Cell (PUC5) Inverter Operating in Stand-Alone and Grid-Connected Modes

Electric power quality (PQ) in distribution system has become increasingly significant subject both for end users and power suppliers with the deregulation of the electric power market. The inadequate performance of conventional compensation devices to mitigate PQ problems has revealed the use of advanced power electronics based compensation devices. Distribution static synchronous compensator (DSTATCOM) is one of the shunt connected custom power devices used to improve PQ, voltage and reactive power support and to increase the capability of the auxiliary service for utility grid. This study presents a comprehensive review of the various DSTATCOM configurations for single-phase (two-wire) and three-phase (three or four-wire) systems and control strategies for the compensation of different PQ problems in distribution systems. In addition, comprehensive explanation, comparison and discussion on DSTATCOM technology are performed. Furthermore, latest trends, practical consideration and some future research fields on DSTATCOMs are discussed in detail. This is intended to present a broad perspective on the status of DSTATCOM technology to researchers dealing with compensation of PQ problems in distribution systems.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2014.0531

Mitigation of power quality problems using distribution static synchronous compensator: a comprehensive review

In this paper, a new cascaded nonlinear controller has been designed and implemented on the packed U-cell (PUC) seven-level inverter. The proposed controller has been designed based on a simplified model of PUC inverter and consists of a voltage controller as an outer loop and a current controller as an inner loop. The outer loop regulates the PUC inverter capacitor voltage as the second dc bus. The inner loop is in charge of controlling the flowing current, which is also used to charge and discharge that capacitor. The main goal of the whole system is to keep the dc capacitor voltage at a certain level results in generating a smooth and quasi-sine-wave seven-level voltage waveform at the output of the inverter with low switching frequency. The proposed controller performance is verified through experimental tests. Practical results prove the good dynamic performance of the controller in fixing the PUC capacitor voltage for various and variable load conditions and yet generating low-harmonic seven-level voltage waveform to deliver power to the loads. Operation as an uninterruptible power supply (UPS) or ac loads interface for photovoltaic energy conversion applications is targeted.

/pdf/real-time-implementation-of-a-seven-level-packed-u-cell-3hwvderhs0.pdf

Real-Time Implementation of a Seven-Level Packed U-Cell Inverter with a Low-Switching-Frequency Voltage Regulator

Studies about investigation of hydrogen production from wind energy and hydrogen production costs for a specific region were reviewed in this study and it was shown that these studies were rare in the world, especially in Turkey. Therefore, the costs of hydrogen, hydrogen production quantities using a wind energy conversion system were considered as a case study for 5 different locations of Nigde, Kirsehir, Develi, Sinop and Pinarbasi located in the Central Anatolia in Turkey. Annual wind energy productions and costs for different wind energy conversion systems were calculated for 50 m, 80 m and 100 m hub heights. According to wind energy costs calculations, the amounts and costs of hydrogen production were computed. Furthermore, three different scenarios were taken into account to produce much hydrogen. The results showed that the hydrogen production using a wind energy conversion system with 1300 kW rated power had a range from 1665.24 kgH2/year in Nigde at 50 m hub height to 6288.59 kgH2/year in Pinarbasi at 100 m hub height. Consequently, Pinarbasi and Sinop have remarkable wind potential and potential of hydrogen production using a wind–electrolyzer energy system.

A review on wind energy and wind–hydrogen production in Turkey: A case study of hydrogen production via electrolysis system supplied by wind energy conversion system in Central Anatolian Turkey

Over the last decade, energy demand from the power grid has increased significantly due to the increasing number of users and the emergence of high-power industries. This has led to a significant increase in global emissions with conventional energy generation. Therefore, the penetration of renewable energy resources into the power grid has increased significantly. Photovoltaic systems have become the most popular resources as their protentional is enormous, thus, the worldwide installed PV capacity has increased to more than 635 gigawatts (GW), covering approximately 2% of the global electricity demand. Power electronics are an essential part of photovoltaic generation; the drive for efficient power electronic converters is gaining more and more momentum. Presently, multilevel inverters (MLI) have become more attractive to researchers compared to two-level inverters due to their abilities to provide lower electromagnetic interference, higher efficiency, and larger DC link voltages. This paper reviews multilevel inverters based on their classifications, development, and challenges with practical recommendations in utilizing them in renewable energy systems. Moreover, PV systems with various maximum power point tracking (MPPT) methods have been extensively considered in this paper as well. The importance and the development of a modified multilevel inverter are also highlighted in this review. In general, this paper focuses on utilizing multilevel inverters for PV systems to motivate and guide society to focus on inventing an efficient and economical multilevel inverter that has the combined capabilities of these converters reported in the literature.

https://www.mdpi.com/1996-1073/14/6/1585/pdf

Review of Multilevel Inverters for PV Energy System Applications

Power quality analysis of wind farm connected to Alaçatı substation in Turkey

In low-power applications of photovoltaic (PV) systems, the transformerless grid-connected inverters have been preferred to increase the efficiency and reduce the cost, size, and power losses when they are compared to the ones with the transformer. A transformerless single-phase inverter topology with a single dc-link capacitor for the grid-connected PV systems is proposed in this paper. The proposed inverter has been simulated by using a cooperation process of the MATLAB and SPICE package programs and it has been implemented for experimental verification. The proposed inverter reduces the high-frequency common-mode leakage current caused by parasitic capacitances of PV panels, whereas it is controlled with the unipolar sinusoidal pulsewidth modulation. Also, the results show that the common-mode voltage remains constant. The efficiency of the proposed inverter has been compared to that of the most common topologies having the dc-link decoupling during the zero voltage states. This paper is accompanied by a video file demonstrating the power loss distribution in the inverter.

Single-Phase Transformerless Photovoltaic Inverter With Suppressing Resonance in Improved H6

A multilevel converter with reduced number of switches in STATCOM for load balancing

This paper presents state space model of singlephase STATCOM based on continues switching function. Continues switching functions for bipolar voltage source inverter (VSI) have been used to derive the transfer function for complete controller. Two proportional integral (PI) controllers which are a DC PI for DC link voltage control and an AC PI for alternating current control are implemented in cascade topology in reactive power compensation. Proposed control method has been analyzed in simulation by using MATLAB. Root locus technique is used to design AC PI controller parameters.

Cascade PI controller for single-phase STATCOM

In this paper, a three-phase, Y-connected, five-level static synchronous compensator with reduced number of switches is proposed for single phase and unbalanced three-phase loads. The level shifted carrier based sinusoidal pulse width modulation method is used for switching. The active and reactive powers demanded by the load are estimated for each phase independently to compensate the reactive power supplied from the power system. The simulation results obtained from Matlab are compared with the results of experimental work and dedicated model of the proposed system. The system is implemented in the laboratory by using DSP TMS320F28335.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-pel.2013.0535

Abdul Balikci

Papers

Power quality analysis of wind farm connected to Alaçatı substation in Turkey

Single-Phase Transformerless Photovoltaic Inverter With Suppressing Resonance in Improved H6

A multilevel converter with reduced number of switches in STATCOM for load balancing

Cascade PI controller for single-phase STATCOM

A three-phase four-wire static synchronous compensator with reduced number of switches for unbalanced loads