Soumyadeep Ray

A Comprehensive Review on Cascaded H-bridge Inverter-Based Large-Scale Grid-Connected Photovoltaic

ABSTRACT Large-scale grid-connected photovoltaic (PV) systems are facing issues like increment of efficiency, minimization of cost, and robustness of the total system. PV strings should operate at maximum power point in all weather conditions to make an efficient system. Inverter is one of the main components along with PV string in grid-connected PV system. Two-level inverters are normally used for practical implementation; however, multilevel inverters, especially cascaded H-bridge (CHB) inverter is one of the best alternative solutions available for large-scale PV plants keeping cost and efficiency in mind. CHB inverters generate a higher voltage output based on series connection of lower voltage H-bridge cells and also having features like higher modularity in structure. High-quality input current and output voltage can be obtained with lower rating devices in CHB-based system. CHB inverters are successfully used in high-power medium voltage drives, STATCOM, and active filter, but CHB-based PV system is facing great challenges in DC voltage balancing, active and reactive power control. This paper presents a comprehensive review on CHB-based large-scale grid-connected PV system. Different topologies and control techniques are reviewed thoroughly to justify potential of CHB-based PV inverters to replace conventional two-level grid-tied large-scale PV inverter. A list of 88 research papers is appended based on advancement, various topologies, and control technique on this area and classified for reference.

Reactive power compensation and power factor improvement using fast active switching technique

Power factor improvement for nonlinear loads is the point of interest for researchers in recent scenario. Power factor plays a major role in efficiency of electrical system. The Purpose of this paper is to show the effectiveness of Magnetic Energy Recovery Switch (MERS) for power factor improvement by using proper control strategy. The MERS is characterized by simple configuration of four active switching devices with one DC capacitor, per phase. The three modes of operation are discussed. Simulation on MATLAB/ Simulink environment is conducted with resistive inductive load and results are compared with and without MERS to show the effectiveness of proposed switch for power factor improvement.

Performance comparison of PI and fuzzy controller for indirect current control based shunt active power filter

The rise of non-linear type of loads, industrial automation has drawn attention towards mitigation of power quality problems and lead to power quality awareness. In this context Shunt active filters efficiently resolve problems caused by current harmonics, improve power factor and compensate reactive power. This paper presents a shunt active power filter which reduces current harmonics in three-phase three-wire system. The performance of conventional PI controller is compared with fuzzy logic controller. The PWM current controlled Voltage Source Converter (VSC) is used as shunt active power filter with hysteresis controller for generating switching pattern. It is observed that the performance of shunt active power filter is superior with indirect current control using active-reactive power theory using fuzzy logic controller. The effective simulation results have been shown for steady state as well as transient conditions.

A Novel Non-Linear Control for Three-Phase Five-Level Cascaded H-Bridge Inverter Based Shunt Active Power Filter

Abstract Cascaded H-Bridge multilevel inverter (CHB-MLI) based shunt active power filter (SAPF) provides a cost-worthy and realistic solution for mitigating current related power quality problems in case of medium-voltage and high-power grid. Mitigation of current harmonic component, reactive power minimization and power factor correction depend on accuracy of control technique applied to the CHB-MLI based SAPF unit. Switching technique dynamics is not considered by most of the researchers while designing control techniques applied to SAPF unit and hence it is assumed linear in order to make system simpler. A limited amount of literature is available which considers the non-linearity of CHB-MLI switching pattern while designing control theory for MLI based SAPF. Therefore, a novel non-linear control is proposed in this paper to enhance system steady-state and dynamic performance. This non-linear control is based on dynamic mathematical modeling of five-level CHB-MLI tied SAPF. Stability of proposed control strategy applied to CHB-MLI based SAPF is rigorously checked by using Lyapunov’s direct method. Proportional-Integral controller is used for stabilizing DC-link voltages to its proper reference value. This proposed control exhibits excellent dynamic performance and compensation criteria in comparison to conventional control techniques available in the literature. The effectiveness of the proposed control theory is tested rigorously in MATLAB/Simulink and verified through hardware prototype under steady-state and transient operating conditions. Rigorous analysis from hardware and simulation results confirms that source current waveform is in compliance with IEEE-519 standard defined THD limit.

Performance comparison of reference current extraction techniques for indirect current control based shunt active filter

The shunt active filters play a dominant role for eradication of power quality problems in modern era, where the majority of load has non-linear nature. It is very important for an active filter to acquire accurate reference current extraction technique as the inaccuracy leads to incorrect compensation and lost control over the DC link. In this paper, three significantapproachesnamely the instantaneous power theory (IPT), unit vector control (UVT) and synchronous reference frame theory (SRF) for reference current extraction have been assessed, evaluated and compared. Thesecontrol schemes are based on indirect current control technique (ICC) and in all methods PI controller is used for stabilization of the DC-link voltage. The advantages and limitations of reference current extraction methods found in literature have been also discussed and justified on the basis of MATLAB simulations for current source type of load, voltage source type of load and transient load conditions.

Comparative analysis of different Controllers on two area interconnected power system model using Gravitational Search Algorithm

This paper presents the effect of different controllers on Load Frequency Control (LFC) of a two area interconnected thermal power system for the advancement of dynamic performance. Time domain simulations are performed to investigate the performance of the system in the presence of generation rate constraint (GRC). The Controller consists of I, PI and PID compensator where the gain setting of proportional (P), integral (I) and derivative (D) constants are optimizes using Gravitational Search Algorithm (GSA) and the objective function used for minimization is Integral of Time multiplied with Absolute value of Error (ITAE). Results reveal that for a step load disturbance, PID controller gives the better dynamic performance of LFC on I and PI compensator and keep the frequency and tie-line power within the range; hence, it proves the effectiveness of GSA based PID compensator in two area interconnected thermal system.