Bharat Singh Rajpurohit

DC Grid Interconnection for Conversion Losses and Cost Optimization

The rapid increment of DC compatible appliances in the buildings, emerge the photovoltaic energy as the fastest growing source of renewable energy and expected to see continued strong growth in the immediate future. The photovoltaic power is, therefore, required to be provided with a certain reliability of supply and a certain level of stability. Motivated by the above issues, many grid operators have to develop DC micro-grids, which treat photovoltaic power generation in a special manner. The interconnection of different voltage rating distributed generation, storage and the load to the DC micro-grid requires large number of converters, which will increase the conversion power losses and the installation cost. Different types of Low Voltage Direct Current (LVDC) grid and their topologies are helpful in understanding the interconnection of distributed generation with consumers end. The connections of LVDC distribution system is discussed in this chapter. Optimization of LVDC grid voltage may reduce the conversion stage and the power loss in DC feeders. A multi-objective technique is discussed, in this chapter, to design a minimum power loss and low cost DC micro-grid.

Intelligent energy management system for PV-battery-based microgrids in future DC homes

Abstract This paper presents a novel intelligent energy management system (IEMS) for a DC microgrid connected to the public utility (PU), photovoltaic (PV) and multi-battery bank (BB). The control objectives of the proposed IEMS system are: (i) to ensure the load sharing (according to the source capacity) among sources, (ii) to reduce the power loss (high efficient) in the system, and (iii) to enhance the system reliability and power quality. The proposed IEMS is novel because it follows the ideal characteristics of the battery (with some assumptions) for the power sharing and the selection of the closest source to minimize the power losses. The IEMS allows continuous and accurate monitoring with intelligent control of distribution system operations such as battery bank energy storage (BBES) system, PV system and customer utilization of electric power. The proposed IEMS gives the better operational performance for operating conditions in terms of load sharing, loss minimization, and reliability enhancement of the DC microgrid.

Electric Grid Connection and System Operational Aspect of Wind Power Generation

Grid integration of wind power is one of the prime concerns as wind power penetration level is increasing continuously. New grid codes are being set up to specify the relevant requirements for efficient, stable, and secure operation of power system and these specifications have to be met in order to integrate wind power into the electric grid. This chapter discusses several issues of advanced grid codes relating to the wind turbines integration into power system. New grid codes for wind power integration of different countries are presented and compared. In India, share of wind power as percentage of installed generation capacity has exceeded 10% in many states and grid connection standards for wind power are in the process of establishment. Grid code requirements for wind power for Indian power sector have been suggested. System operational aspects of wind power generation with Indian experience have discussed.

Design and analysis of a DC microgrid with centralized Battery Energy Storage System

This paper presents modelling and simulation of an autonomous DC microgrid in Matlab Simulink environment. The proposed microgrid system consists of a wind turbine, solar PV array and DC loads. The wind turbine is interfaced to the microgrid with a rectifier and a buck converter which are controlled to maintain a constant DC bus voltage. While the PV array is connected via a boost converter which extracts maximum power from the circuit. The microgrid system also consists of a centralized Battery Energy Storage System (BESS) which is connected via a bidirectional buck-boost converter. The overall stability of the microgrid is maintained by the control action of the BESS. Finally, simulation study of the microgrid with the proposed control methodologies is carried out for various operating conditions.

A survey on active power filters control strategies

Due to increased level of harmonic pollution in present day power system, power quality conditioning has become indispensable, and therefore, various power conditioning techniques were introduced. Among them, active power filters appear to be the most viable device used for mitigating power quality issues. Various strategies of controlling active power filter are proposed and implemented by researchers and engineers in aim of achieving near perfect compensation. This paper presents a comprehensive review of state-of-art control strategies of active filters. Various strategies are discussed and compared in terms of implementation and performance.

Induction machine efficiency estimation using population based algorithm

There has been a tremendous pressure to predict the in situ efficiency of induction machine (IM) with limited level of intrusion so as to improve IMs performance. Least research work is carried out to make IM efficiency evaluation methods compatible to unbalanced supply and varying load conditions. This paper proposes a novel approach using cuckoo search algorithm (CSA) to obtain efficiency estimation of an IM operating as a motor working with unbalanced supply having under or over voltage issues. CSA improves the searching ability and has capability to adapt to complex optimization problems. Here, CSA optimizes the IM positive sequence parameters at various loading levels. The parameters optimization is done with the use of positive sequence input currents and electrical powers which have been obtained earlier at various operating loading points. Using the optimized parameters, the negative sequence parameters can be evaluated. So, the efficiency of IM can be estimated at different loading levels. The proposed approach is implemented on the MATLAB platform. The effectiveness of the novel approach is established by comparing the results obtained with genetic algorithm (GA).

Optimization of DC microgrid for rural applications in India

This paper presents planning and optimization of DC microgrid for rural applications in India. Load profile of a village in Chhattisgarh state of India is considered for the study. Hourly data of solar irradiation & wind speeds and prices of the various components of the microgrid are also obtained. Using these data, a model of DC microgrid is constructed in Homer Energy™ software. Simulations are then carried out to determine the optimal system configuration which has the lowest life cycle cost for autonomous operation. A special case study for with a partial connectivity to the grid is also conducted. The study also gives a detailed analysis of the various cost components, energy productions, power management and emissions.

Optimal structure of a Smart DC micro-grid for a cluster of zero net energy buildings

A decarbonized society involves people living and working in low-energy and low-emission buildings. A smart multi-Terminal DC micro-grids interconnecting several autonomous zero-net energy buildings (ZNEBs) allow the transition to a decarbonized economy, however, involves several challenges. This paper evaluates the problem of an optimal topology for a cluster of several ZNEBs and it takes several advantages related to the holistic operation and planning. A high-resolution electricity demand model is used together with several scenarios of stochasticity (weather, human behaviour, etc.) in order to create several credible scenarios of electricity demand at each ZNEB and then solve the constrained optimization problem of two network topologies for the cluster of interacting ZNEB. This paper has demonstrated the appropriate performance of the proposed approach using a verys simple, demonstrative/illustrative, example, a cluster of three DC-Houses.

Analysis of position and speed control of sensorless BLDC motor using zero crossing back-EMF technique

Motor is the heart of many industrial automation and motion control applications. Brushless DC (BLDC) motor drives are widely used in a many applications, ranging from low to high power applications, because of their high efficiency, low maintenance, require small space, salient operation and high torque to power ratio, etc. The rotor position must be acquired in order to drive a BLDC motor. The position of the rotor is known by hall sensors and encoders, but when these types of sensors are used to drive BLDC motor, the circuits become very complex and large. Therefore accuracy and performance of BLDC motor drivers should be enhanced through sensorless technology. Many sensorless methods are existing in literature to sense the rotor position of motor, but this paper explain and proposed zero crossing back-EMF detection method. This paper work on analysis of sensorless techniques to sense the rotor position and PWM based speed control of inverter-fed sensorless BLDC motor. Modeling and simulation of three-phase star connected sensorless BLDC motor is done in MATLAB/Simulink environment. An accurate speed estimation has been achieved by using back EMF zero crossing speed estimation method. Fast response with negligible settling time has been obtained by this method of sensorless speed estimation of BLDC motor.

Performance Analysis of Unified Doubly-Fed Induction Generator for Wind Power Application

Increasing penetration of the large wind farm in the system has forced the power system policy makers to develop new electricity grid codes which are required for the wind power generator to fulfill the same requirements as conventional power plants. This paper introduces a new solution for doubly fed induction generators (DFIG) to stay connected to the grid during abnormal conditions. The main idea is to provide a series connected grid side converter (SGSC) with conventional DFIG scheme. A new control scheme is then described and analyzed, which allows relatively low-energy ratings in the SGSC, thereby significantly lowering the overall system cost. Analysis is carried out to explore the grid code requirements (GCR) during static and dynamic conditions for the performance of the system along with the controller for abnormal conditions. Reactive power support capability of series converter during steady state condition is also demonstrated. A detailed small-signal analysis carried out which provides the insight of oscillatory behavior of DFIG. Extensive simulation and analytical results have demonstrated the enhanced performances resulting from the application of the control scheme and in compliance with the new grid codes.