An Advanced Control Scheme for Voltage Source Inverter Based Grid-Tied PV Systems

Technological developments such as Flexible AC Transmission Systems (FACTS) can improve the power quality of the power system and can respond to the ever-increasing demand for electrical energy.Superconducting magnetic energy storage (SMES) is a FACTS device that has been used for several years at utility and industrial sites throughout the United States, Japan, Europe, and South Africa to provide both transmission voltage support and power quality to customers who are vulnerable to fluctuating power quality [1]- [3].SMES systems are classified into two groups: voltage source inverter (VSI) and current source inverter (CSI) SMES.The VSI SMES has many advantages when compared with the CSI SMES; for example, in the VSI SMES, the power rating of power electronic devices that are used in the inverter is much less than that of the CSI SMES, resulting in fewer switching and power losses.Also, the VSI SMES can be used as a Static synchronous Compensator (STATCOM) when its chopper is out of service.Moreover, for the same condition, the VSI SMES can store more energy than the CSI SMES; these advantages encouraged the authors to study VSI SMES.This type of SMES is composed of a magnetic energy storage coil with various structures and power conditioning systems that are also composed of different parts, such as AC-DC filters, a multi-level chopper, a capacitor bank, and a multi-level converter (i.e. an inverter or rectifier).These power conditioning systems are also used in many different sustainable energy systems, such as bio fuels, solar power, wind power, wave power, geothermal power, and tidal power.The converter is an interface between the power network and the capacitor bank and controls the electrical energy exchange between the two.Likewise, the chopper is also an interface between the magnetic energy storage coil and the capacitor bank, and controls electrical energy exchange between them.To store the electrical energy in the capacitor bank and the magnetic energy storage coil in the range of mega joules, it is necessary to employ high power-rating converters; to overcome the limitations of the current and voltage range of the semiconductors, multi-level converters are used.The advantages of using such converters include reducing voltage on the switches, harmonic order correction, decreasing or eliminating lateral equipment, decreasing switching frequency, decreasing total harmonic distortion (THD), decreasing switching losses, and decreasing the output current ripple.

With the development of modern technology, high quality power supply becomes more desirable in everyday life. Among problems related with the power quality, the most urgent is the voltage dip; with the application of power electronics devices, the power system is polluted by harmonics. SMES (Superconducting Magnet Energy Storage) system can not only compensate the voltage dip, but also provide a load-fluctuation compensation and active power filter. In the paper the main structure of SMES system is introduced; the necessity to use SMES are demonstrated by analyzing the problem of power quality. The analysis shows that SMES system is effective in improving the power quality.

The authors demonstrate that a superconductive magnetic energy storage (SMES) system can provide a significant positive impact on electric power transmission. By using SMES, transmission-line loadings during heavy load hours can be reduced if the SMES system is located near the major load. Transmission losses as well as the fuel cost for the losses over a 24 hr period can also be decreased. An SMES scheme, the SMES-DC link, is introduced for energy storage and control of power flow. The operation of this scheme and the benefits it provides are described. >

A new power supply which permits the independent regulation of the active and reactive power of a superconductive magnetic energy storage (SMES) system is discussed. The power supply consists of 20 units connected in parallel. Each unit contains a 24-pulse bridge converter, a thyristor switched capacitor bank. An SMES system using the power supply is capable of improving power system stability and oscillation damping, as well as performing load leveling. The power supply can be built with commercially available components using well-proven technology.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

FAST INDUCTIVELY COUPLED SUPERCONDUCTING OPENING SWITCH TRIGGERED BY SHORT LASER PULSES

Superconducting magnetic energy storage systems: Prospects and challenges for renewable energy applications

This paper presents the impact of wind energy generation system (WEGS) and superconducting magnetic energy storage (SMES) in enhancing the voltage profile for three phase unbalanced radial distribution system for 24 hours. Fixed-speed squirrel-cage induction generator (SCIG) type with a fixed capacitor connected at stator terminal to enhance the power factor is used in this work as WEGS. SMES DC-DC chopper is controlled with fuzzy logic controller (FLC) to manage the power transmitted between SMES and the grid side. FLC is analyzed for SMES able to stored/release real power from/to the distribution power system. SMES system and WEGS installed in the distribution system at worst voltage bus. In this paper enhancement of the voltage profile for radial unbalanced IEEE 34-node feeder was performed. The power-flow calculations were performed using C++ programming. A practical electricity demand in France daily load curve used to change the loading demand of 34 bus systems. By using SMES system with WEGS at the same bus in the distribution system, voltage profile of the system in all modes of operation can be improved.

A voltage source converter (VSC) based high temperature superconducting (HTS) magnetic energy storage system (SMES) has been optimal designed and constructed by China Electric Power Research Institute (CEPRI). This SMES uses two kinds of high temperature superconductors, YBCO and BSCCO tapes for the first time. The application planning of SMES with the equivalent capacity in a practical renewable power system at Zhangbei wind power test base in China is evaluated by a simulation analysis based on the PSCAD/EMTDC. An optimal switch time of the SMES in Zhangbei wind farm is presented using the real transmission parameters of Zhangbei power grid. This study can provide a demonstration of large-scale SMES systems in a renewable power system.

Throughout the past several years, the renewable energy contribution and particularly the contribution of wind energy to electrical grid systems increased significantly, along with the problem of keeping the systems stable. This article presents a new optimization technique entitled the Archimedes optimization algorithm (AOA) that enhances the wind energy conversion system’s stability, integrated with a superconducting magnetic energy storage (SMES) system that uses a proportional integral (PI) controller. The AOA is a modern population technique based on Archimedes’ law of physics. The SMES system has a big impact in integrating wind generators with the electrical grid by regulating the output of wind generators and strengthening the power system’s performance. In this study, the AOA was employed to determine the optimum conditions of the PI controller that regulates the charging and discharging of the SMES system. The simulation outcomes of the AOA, the genetic algorithm (GA), and particle swarm optimization (PSO) were compared to ensure the efficacy of the introduced optimization algorithm. The simulation results showed the effectiveness of the optimally controlled SMES system, using the AOA in smoothing the output power variations and increasing the stability of the system under various operating conditions.

Analysis of magnetic field distribution and AC losses of a 600 kJ SMES

Superconducting Magnetic Energy Storage (SMES) systems are one of the superconducting technologies with envisaged applications in power systems. The flexibility of these systems allows a utilization as Energy Storage Systems (ESS) but also as power devices, for power quality applications. In the actual context of electric grids, with the emergence of the paradigm of Smart Grids, the possible applications of SMES systems are discussed, considering the actual state of the art in superconducting materials. Main envisaged applications are presented and a short comparison with other ESS is also performed, as a way to integrate SMES systems into the actual and upcoming context of power systems. Main already running or finished projects using not only standalone SMES systems but also a combination of multiple superconducting devices are also presented. Finally, a short description of concept projects using SMES systems is also given.

Integrated design method for superconducting magnetic energy storage considering the high frequency pulse width modulation pulse voltage on magnet

Superconducting magnetic energy storage (SMES) and superconducting fault current limiters (SFCL) can be used to stabilize the wind generator system. While both SMES and SFCL use superconducting coils for their operations, this paper makes a comparative study of these two devices in case of their applications in the wind generator system. The comparison is done on the basis of transient stability enhancement, controller complexity, and cost. In order to analyze the effect of the SMES and SFCL on wind generator stabilization in more detail, several performance indices are considered. Simulation results show that both the SMES and SFCL can stabilize the wind generator system during a severe fault. However, the performance of the SMES is better than that of the SFCL. Also, from the controller viewpoint, the SMES system is more complex than the SFCL system. Moreover, from the perspective of cost, the SMES might be costlier than the SFCL. As a whole, this study would help the readers understand the relative effectiveness of the SMES and SFCL methods, and then select a suitable method for wind generator stabilization.

Keeping in the mind of pulsed power applications, especially in defence sectors, the Superconducting Magnetic Energy Storage (SMES) system is proposed for a smooth and reliable power flow in the grid. Power Converter Unit (PCU) of the SMES system consists of a DC-DC converter and a three-phase voltage source converter along with a DC-link capacitor which couples both the converters. Particularly, the voltage across the DC-link capacitor is tightly regulated using a dynamic evolution based control strategy in the DC-DC converter. Consequently, the DC-link voltage is maintained almost constant with a voltage regulation of ± 5.26% during pulsed power load condition. Moreover, an effective pulsed power load compensation, and uniform voltage distribution across the SMES coil are achieved due to the precise solid-state control. Nevertheless, the performance of the proposed SMES system is conducted in the MATLAB software.

Applications of superconducting magnetic energy storage (SMES) technology have been progressed actively. Principal application schemes of sole SMES, hybrid energy storage system (HESS) consisting of small-scale SMES and other energy storage systems (ESSs), distributed SMES (DSMES), and distributed HESS (DHESS) have been presented and compared to develop smart energy managements. The results obtained demonstrate that SMES has the significant potential to combine with, even replace the conventional ESSs in future smart grids (SGs). The integrated SMES application prospects have been discussed using a sample case of a DC power distribution network.