DC Link Of Voltage Source Converter Research Articles

Multi-functional Microgrid’s Transient-Free Connection: Disconnection with Grid

A wind–solar microgrid synchronization is realized in this work. Such microgrid has the capability to serve the loads in islanded mode, and to connect and disconnect itself with the main grid smoothly using synchronization control. It feeds excess renewable power to the AC mains during high renewable energy generation, and also the power is supplied from the grid to the loads at low renewable generation. The voltage source converter (VSC) of microgrid operates with the voltage control and the current control algorithms. At the DC link of VSC, a battery is attached to provide power leveling. Microgrid multi-functioning aspects (voltage–frequency regulation, power balance, harmonics elimination, synchronization, de-synchronization) under isolated and grid-connected modes with variety of test results are demonstrated. A laboratory prototype of wind–solar microgrid is built to validate the performance through test results.

Three-Phase Grid-Interactive Solar PV-Battery Microgrid Control Based on Normalized Gradient Adaptive Regularization Factor Neural Filter

In this article, a normalized gradient adaptive regularization factor neural filter based control is presented for a three-phase grid interfaced solar photovoltaic (PV)-battery energy storage microgrid system. An incremental conductance (INC) technique is utilized for the peak power extraction of a solar PV array. A battery is connected through a bidirectional converter at dc-link of voltage-source converter (VSC), and it charges and discharges as per load variation and enhances the reliability of the system. This dc–dc converter also regulates the dc-link voltage for maximum power point tracking (MPPT). This neural filter based current controller improves the dynamic behavior of the proposed system and feeds active power to the utility grid by utilizing the feed-forward term of solar PV power under variable atmospheric scenarios. A power electronics switch is used for VSC mode shifting operation between current control in the grid-connected mode and voltage control in an islanded mode to ensure continuous and adequate power to the nonlinear load. The discrete proportional and resonant (PR) controller is used for the voltage control in an islanded mode to reduce the steady-state error between sensed and reference load voltages. The voltage controller also regulates the frequency. Simulations of the microgrid system are carried out by utilizing MATLAB/Simulink software to show the effectiveness of control technique. The performance of the system is found satisfactory for various operating conditions such as load variation, load unbalancing, and solar insolation change, and validated through test results on a developed laboratory prototype.

Seamless Transfer of Renewable-Based Microgrid Between Utility Grid and Diesel Generator

This paper deals with the renewable energy-based microgrid (MG) to feed the community loads. It has the capability to synchronize with the utility as well as with the diesel generator (DG) set. During healthy grid condition at high renewable power generation and when load demand is less, it feeds power to the grid while at low renewable generation power is taken from the grid. During outage and low renewable power generation, it synchronizes with the DG set to meet the load demand and forms a hybrid microgrid. In islanding, the voltage source converter (VSC) operates in a voltage control mode for realizing a renewable MG and operates in the current control mode for implementing a hybrid MG and switching to the grid-connected mode. An incremental conductance and perturb & observe approaches with a boost converter are implemented for the maximum power extraction of the renewables. A battery bank is connected at the dc link of VSC. The multifunctional MG synchronization and de-synchronization with ac mains/DG set are discussed in conjunction with variety of test results. In this topology, a single bidirectional converter is implemented and controlled using various control algorithms to manage MG power among generation, storage, and load units. A MATLAB/Simulink model is developed for a wind–solar–diesel based MG. Simulated results are validated with test results on a developed laboratory prototype.

Multi-Objective Control Algorithm for Small Hydro and SPV Generation-Based Dual Mode Reconfigurable System

This paper proposes a small hydro (ac) and solar photo-voltaic (SPV) generation (dc)-based dual mode multi-functional reconfigurable system. The small hydro system is connected to the point of common coupling (PCC) directly. The SPV system is connected to ac side (PCC) through a boost converter and a voltage source converter (VSC). A storage system is integrated across dc link of VSC through a bidirectional converter to balance the generation and the loads in an islanded mode. The distinguished feature of proposed system is that it operates either in grid connected mode or an islanded mode depending on grid availability. It supplies uninterruptable power to emergency loads. An important aspect of control strategy is that it automatically synchronizes the system to the grid when the grid is available in an islanded mode. It also disconnects the system from the grid when a fault occurs on the grid feeder in grid connected mode. In an islanded mode, it regulates voltage and frequency of hydro generator across PCC. In grid connected mode, it regulates the current fed by VSC. It also improves the power quality of the hydro generator and the grid by elimination of current harmonics, load balancing, and compensation of reactive power under nonlinear loads. The performance of proposed system is found satisfactory in transient modes and in dynamic conditions. The interruption time in the load end voltage and resynchronization time are well within an IEEE 1547 standard. The total harmonic distortion of grid current, hydro generator current and load voltage is also well under IEEE 519 standard even at nonlinear loads.

Power Quality Enhancement Using DSTATCOM in Distributed Power Generation System

In this paper, a distribution static compensator (DSTATCOM) is implemented for controlling a distributed power generating system using a proposed composite observer based control technique. The proposed control technique is employed for the fundamental components extraction of distorted load currents. These extracted components are used in the estimation of reference source currents to generate gating signals of DSTATCOM. The proposed control technique is implemented for the mitigation of reactive power, distortion in term of harmonics, and load balancing under linear/nonlinear loads. The performance of DSTATCOM is observed satisfactory for these consumer loads with regulated generator voltage at point of common coupling and self-supported dc link of voltage-source converter of DSTATCOM.

Back-Propagation Algorithm-Based Controller for Autonomous Wind–DG Microgrid

This paper deals with a wind–diesel generator hybrid configuration of the microgrid using a voltage source converter (VSC) as a voltage and frequency (VF) controller. The wind power generated by permanent magnet brushless dc generator, and the maximum power is captured by a maximum power point technique using a boost converter with an incremental conductance approach. This power is supplied to the consumer loads and surplus power is stored into battery system (BS). BS is attached at dc link of VSC, which provides load leveling during less or no wind conditions. With such combination of energy resources, a reduced rating, diesel engine-driven squirrel cage induction generator feeds loads, and VSC at point of common coupling (PCC) supports the system when the wind generation is unable to meet out the load demand. Back-propagation feed-forward control algorithm is used for VF control of VSC. This controller provides harmonics elimination, load leveling, and reactive power compensation, and also regulates the voltage at PCC. This microgrid is modeled in MATLAB Sim power tools, and simulation results are produced to verify the appropriate working of both the converters and the overall system. A prototype of the microgrid is also developed to validate the design and model through test results. A comparative study of simulated and experimental work is given in detail.