Renewable energy sources like wind, sun, and hydro are seen as a reliable alternative to the traditional energy sources such as oil, natural gas, or coal. Distributed power generation systems (DPGSs) based on renewable energy sources experience a large development worldwide, with Germany, Denmark, Japan, and USA as leaders in the development in this field. Due to the increasing number of DPGSs connected to the utility network, new and stricter standards in respect to power quality, safe running, and islanding protection are issued. As a consequence, the control of distributed generation systems should be improved to meet the requirements for grid interconnection. This paper gives an overview of the structures for the DPGS based on fuel cell, photovoltaic, and wind turbines. In addition, control structures of the grid-side converter are presented, and the possibility of compensation for low-order harmonics is also discussed. Moreover, control strategies when running on grid faults are treated. This paper ends up with an overview of synchronization methods and a discussion about their importance in the control

/pdf/overview-of-control-and-grid-synchronization-for-distributed-2nx31ovpe9.pdf

Overview of Control and Grid Synchronization for Distributed Power Generation Systems

The science and technology of ultracapacitors are reviewed for a number of electrode materials, including carbon, mixed metal oxides, and conducting polymers. More work has been done using microporous carbons than with the other materials and most of the commercially available devices use carbon electrodes and an organic electrolytes. The energy density of these devices is 3¯5 Wh/kg with a power density of 300¯500 W/kg for high efficiency (90¯95%) charge/discharges. Projections of future developments using carbon indicate that energy densities of 10 Wh/kg or higher are likely with power densities of 1¯2 kW/kg. A key problem in the fabrication of these advanced devices is the bonding of the thin electrodes to a current collector such the contact resistance is less than 0.1 cm2. Special attention is given in the paper to comparing the power density characteristics of ultracapacitors and batteries. The comparisons should be made at the same charge/discharge efficiency.

Ultracapacitors: Why, How, and Where is the Technology

This paper reviews the current status and implementation of battery chargers, charging power levels, and infrastructure for plug-in electric vehicles and hybrids. Charger systems are categorized into off-board and on-board types with unidirectional or bidirectional power flow. Unidirectional charging limits hardware requirements and simplifies interconnection issues. Bidirectional charging supports battery energy injection back to the grid. Typical on-board chargers restrict power because of weight, space, and cost constraints. They can be integrated with the electric drive to avoid these problems. The availability of charging infrastructure reduces on-board energy storage requirements and costs. On-board charger systems can be conductive or inductive. An off-board charger can be designed for high charging rates and is less constrained by size and weight. Level 1 (convenience), Level 2 (primary), and Level 3 (fast) power levels are discussed. Future aspects such as roadbed charging are presented. Various power level chargers and infrastructure configurations are presented, compared, and evaluated based on amount of power, charging time and location, cost, equipment, and other factors.

/pdf/review-of-battery-charger-topologies-charging-power-levels-85yy2igx2w.pdf

Review of Battery Charger Topologies, Charging Power Levels, and Infrastructure for Plug-In Electric and Hybrid Vehicles

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

The aim of this paper is to present a review of current control techniques for three-phase voltage-source pulsewidth modulated converters. Various techniques, different in concept, have been described in two main groups: linear and nonlinear. The first includes proportional integral (stationary and synchronous) and state feedback controllers, and predictive techniques with constant switching frequency. The second comprises bang-bang (hysteresis, delta modulation) controllers and predictive controllers with on-line optimization. New trends in current control-neural networks and fuzzy-logic-based controllers-are discussed, as well. Selected oscillograms accompany the presentation in order to illustrate properties of the described controller groups.

Current control techniques for three-phase voltage-source PWM converters: a survey

This paper presents a simple self-commissioning algorithm to estimate various motor parameters for Rotor-Flux-Oriented (RFO) induction motor drive As the parameters are calculated from simple voltage equations and integration, it is possible for the proposed algorithm to be included in the main program with a low cost micro-controller Also, it works well under arbitrary operating condition, and it is robust to measurement noise

A simple induction motor parameter estimation method for vector control

In this paper, the effect of parameter errors to the estimation of the rotor angle in sensorless operation of a permanent magnet synchronous motor is analyzed. The angle error information which is utilized to estimate the rotor position can be classified into two factors, namely, the sign factor and the gain factor. This paper particularly focuses on parameter errors reflected in the sign factor of the angle error information which causes a deviation in the angle estimation. In this paper, mathematical expressions describing the deviation of the angle estimation due to the inductance error and the resistance error in the sensorless control are derived. The validity of the expression is verified by the computer simulations and the experimental results.

Effects of Parameter Errors on Sensorless Operation of PMSM

In this paper, the design and control aspects of a multi-span tension simulator are presented. The simulator consists of four driven rolls including unwinder, winder and two bridle rolls. Some relationships between design parameters and characteristics of the simulator are explained as a design guide of a multi-span system. A new control algorithm of continuous load balance control is proposed for the control of speed and tension in multi-span system. The strip tension is controlled by the continuous balancing of the load torque of rolls without tension sensor. The simulation and experimental results reveal conspicuous improvement of tension control performance by the proposed algorithm.

Design and control of multi-span tension simulator

New Strategy to Estimate The Rotor Flux of Induction Motor by Analyzing Observer Characteristic Function

This paper proposes a new maximum power point tracking (MPPT) scheme, based on perturb and observe concept, for a single stage PV water pump system working effectively under various environmental conditions. The selection of frequency step size is an important parameter for single stage solar water pump system. Larger step size may lead to a sudden drop in DC link voltage due to oscillations around the maximum power point. Smaller step size takes longer time to reach MPP or may get trapped at lower power point. The system may also fail under dynamic change of environmental conditions (particularly during rapid fall in solar irradiation). The proposed algorithm is able to identify the conditions under which DC link voltage may fall and operate the system at a point where it can work efficiently without halt of system. The detailed analytical, simulation and experimental results of this work under different environmental conditions are presented in this paper.

Seung-Ki Sul

Papers

A simple induction motor parameter estimation method for vector control

Effects of Parameter Errors on Sensorless Operation of PMSM

Design and control of multi-span tension simulator

New Strategy to Estimate The Rotor Flux of Induction Motor by Analyzing Observer Characteristic Function

New maximum power extraction algorithm for single stage solar water pump system working effectively for dynamically changing conditions