Wajiha Shireen

Plug-in Hybrid Electric vehicles in the smart grid environment

Plug-in hybrid electric vehicles (PHEVs) have the potential to curb emission and reduce the cost of transportation. Another unique advantage of PHEVs is their capability to integrate the onboard energy storage units with the power grid which can improve the efficiency and increase the reliability of the power grid. These concepts are still new and under development. Unlike Hybrid Electric vehicles (HEVs) a major concern in the case of PHEVs is the impact on the grid when they are plugged in for charging to the already loaded grid. In view of this, this paper presents the trends in analysis, design and evaluation of PHEVs in the future smart grid environment.

PV Integrated Smart Charging of PHEVs Based on DC Link Voltage Sensing

With the proliferation in the number of PHEVs the demand on the electric grid increases appreciably. A smart charging station is proposed in which the charging of the PHEVs is controlled in such a way that the impact of charging during peak load period is not felt on the grid. The power needed to charge the plug in hybrids comes from grid-connected photovoltaic (PV) generation or the utility or both. The three way interaction between the PV, PHEVs and the grid ensures optimal usage of available power, charging time and grid stability. The system designed to achieve the desired objective consists of a photovoltaic system, DC/DC boost converter, DC/AC bi-directional converter and DC/DC buck converter. The output of DC/DC boost converter and input of DC/AC bi-directional converter share a common DC link. A unique control strategy based on DC link voltage sensing is proposed for the above system for efficient transfer of energy.

Photovoltaic charging station for Plug-In Hybrid Electric Vehicles in a smart grid environment

It has been estimated that, there will be one million Plug-In Hybrid Electric Vehicles (PHEVs) by the end of this decade. There is a growing risk that, this proliferation in the number of PHEVs will trigger extreme surges in demand while charging them during rush hours. To mitigate this impact, a unique charging station architecture is proposed in which the rate of charging of the PHEVs is controlled in such a way that the impact of charging during peak load period is not felt on the grid. The power needed to charge the plug in hybrids comes from grid-connected photovoltaic generation or the utility or both. The three way interaction between the PV, PHEVs and the grid ensures optimal usage of available power, charging time and grid stability. The system designed to achieve the desired objective consists of a photovoltaic system, DC/DC boost converter, DC/AC bi-directional converter and DC/DC buck converter. The output of DC/DC boost converter and input of DC/AC converter share a common DC bus. A unique control strategy based on DC bus voltage sensing is proposed for the above system for efficient transfer of energy. By using the proposed control strategy, the operations of charging station can be categorized into four modes: grid-connected rectification, PV charging and grid-connected rectification, PV charging and grid-connected inversion.

Controlling multiple motors utilizing a single DSP controller

Traditionally the cost sensitive motor drive market forced designers to avoid DSP controllers for their drive design. However, several factors are rapidly changing this scenario. The prices of DSPs have dropped from hundreds of dollars to approximately three dollars since their introduction in the early 1980s. Moreover, DSPs can now integrate a variety of sophisticated peripherals. This integration of DSP core with a set of useful peripherals significantly simplifies the design. At the same time, the cost sensitive drives like heating ventilating and air conditioning (HVAC), appliances are starting to utilize variable speed drives to maximize the efficiency and comfort for the user. Many of these applications have more than one motor. For example, a typical HVAC system usually utilizes two motors. Until now, these motors were mainly operated at a fixed speed or at a set number of multiple speeds to minimize cost. This paper shows the advantages of using DSP controllers for such applications. It will be shown that these controllers provide a true single chip solution for these drives.

Grid connected residential photovoltaic energy systems with Plug-In Hybrid electric Vehicles(PHEV) as energy storage

This paper proposes an approach for the control and optimization of power flow by integrating Plug-In Hybrid Vehicles (PHEV) to an existing residential photovoltaic system. Optimization of Power flow reduces the dependency for electric power from the grid and control involves determining the source from which residential load will be catered. The system built to achieve the goal is a combination of the existing residential photovoltaic system, PHEV, Power Conditioning Unit (PCU) and a controller. The PCU involves two DC-DC Boost Converters and an inverter. This paper emphasizes on developing the controller logic and its implementation in order to accommodate the flexibility and benefits of the proposed integrated system.

A DSP based SVPWM control for utility interactive inverters used in alternate energy systems

This paper presents a DSP based algorithm to control inverters used in interfacing alternate energy systems with the electric utility. Since a constant and ripple free DC bus voltage is not ensured at the output of alternate energy sources, the main aim of the proposed algorithm is to make the output of the inverter immune to the fluctuations in the DC input voltage. In this paper a modified space vector pulse width modulation (SVPWM) technique is proposed which will maintain the quality of the AC output of the inverter, regardless of the ripple present at the inverter input. The principle is explained qualitatively and extensive experiments have been carried out to verify and validate the proposed algorithm. A 16-bit fixed-point C2000 family DSP from Texas Instruments was used as the controller to implement the proposed control algorithm.

Implementation of a DSP based active power filter for electric power distribution systems supplying nonlinear loads

The use of nonlinear loads, which inject undesired harmonic currents into low voltage distribution systems, is increasing rapidly. Active power filters are being considered as a potential candidate for solving harmonic problems in order to meet harmonic standards and guidelines. A new digital signal processor (DSP) based control method for a single phase active power filter (APF) is presented in this paper. Compared to conventional analog and microprocessor based methods the DSP based solution provides a flexible and cheaper method to control the APF. The proposed scheme employs a carrier based control that requires less feedback information compared to other reported solutions. Only one current sensor is used to sense the nonlinear load current and two voltage sensors to sense the input supply voltage and the DC bus voltage. It also reduces the total chip count of the system using on-chip power electronics peripherals of the DSP controller (TMS320F240). The proposed method provides both harmonic elimination and power factor correction. The PSpice simulation and experiments using the DSP controller are made to verify the feasibility of the method.

Control for grid connected PMSG Wind turbine with DC link capacitance reduction

An enhanced control is presented that effectively cancels the noise in torque, and currents in a wind turbine Permanent Magnet Synchronous Generator. The proposed control also allows the reduction of the DC-Link capacitance. Simulations succeed on Three Phase and Single Phase grid connection, through a Back to Back converter. The grid side converter switching function was modified with an algorithm that represents the noise from grid frequency. The DC Link ripple due to capacitor reduction was canceled, and as a consequence there were no noise frequencies on electromagnetic torque, stator and grid currents after the algorithm was implemented. Remarkable reduction in DC Link capacitor was possible, making the system more reliable and economical. The PMSG is protected from core saturation, because stator currents consist of only the fundamental frequency component. This results in a constant torque, preventing mechanical stress.

Fast converging MPPT control of photovoltaic systems under partial shading conditions

A novel high performance control to track the maximum power point (MPP) of a photovoltaic (PV) module under rapidly fluctuating operating conditions like irradiation change and partial shading has been developed. A DC-DC boost converter is selected as the Power Conditioning Unit (P.C.U) to coordinate the operating point of the system with the maximum power point of the PV array. The proposed algorithm uses a scanning technique to measure the maximum power delivering capacity of the panel and the proposed control makes the system to operate at the MPP, even under rapidly changing operating conditions. The algorithm is simple to implement and easy to execute with high tracking efficiency. The proposed method is successfully implemented, analyzed and verified in Mat-lab/Simulink software. The results obtained for rapid change in irradiation conditions verify that the proposed MPPT control provides an efficient tracking within 15ms. The results also verify that the proposed control algorithm guarantees convergence to the global MPP even under partial shading.

Active Filtering of Input Ripple Current to Obtain Efficient and Reliable Power from Fuel Cell Sources

Fuel cells are one of the cleanest and most efficient technologies for generating electricity. In most cases, the fuel cell associated power conditioning system must include a DC-DC converter and a DC to AC inverter. Inverter input ripple current has been reported to possibly degrade fuel cell performance and reduce operating life if ripple currents are not adequately controlled. This paper proposes an active filtering method to cancel the 2nd harmonic current ripple drawn from the fuel cell source in a typical single phase fuel cell system. The proposed active harmonic filter provides an alternate path for the 120 Hz ripple, thereby, preventing the ripple from circulating through the source. The proposed system was simulated using PSpice and the results are presented. Experimental results from a laboratory prototype are also included to validate the proposed approach