Development of community grid: review of technical issues and challenges

The concept of a community grid is presented here. It involves the distribution grid and an increased use of renewable energy coming from distributed resources along with the consumers/prosumers engagement in energy trading mechanism. The possible operation and management with energy trading flexibility are briefly outlined. Under such scenario, the classical operation of the distribution grid is challenged by the issues brought by the large penetration level of the new energy resources. This paper presents a status review of the technical issues that may appear under the community grid scenario. Building upon those surveyed issues, this work also reviews and discusses approaches to solutions, which are required in order to make the community grid highly renewable and sustainable

Asset management strategies for power electronic converters in transmission networks: Application to HVdc and FACTS devices

The urgency for an increased capacity boost bounded by enhanced reliability and sustainability through operating cost reduction has become the major objective of electric utilities worldwide. Power electronics have contributed to this goal for decades by providing additional flexibility and controllability to the power systems. Among power electronic based assets, high-voltage dc (HVdc) transmission systems and flexible ac transmission systems (FACTS) controllers have played a substantial role on sustainable grid infrastructure. Recent advancements in power semiconductor devices, in particular in voltage source converter based technology, have facilitated the widespread application of HVdc systems and FACTS devices in transmission networks. Converters with larger power ratings and higher number of switches have been increasingly deployed for bulk power transfer and large scale renewable integration—increasing the need of managing power converter assets optimally and in an efficient way. To this end, this paper reviews the state-of-the-art of asset management strategies in the power industry and indicates the research challenges associated with the management of high power converter assets. Emphasis is made on the following aspects: condition monitoring, maintenance policies, and ageing and failure mechanisms. Within this context, the use of a physics-of-failure based assessment for the life-cycle management of power converter assets is introduced and discussed

Detection of Permanent Magnet DC Motor Failure Due to Brush Wear Using Parameter Estimation and Statistical Analysis

Failure detection of DC motors is a common study, and could be extremely useful in real world applications. Undiagnosed eminent motor failure could cause a range of effects, and without maintenance will inevitably occur. Motor faults can be classified as electrical or mechanical, both with wide ranges of causes. Electrical failure includes stator or rotor winding faults, inverter faults, position of sensor faults in brushless motors, bearing faults, and brush faults. Mechanical faults include bearing faults, broken rotor bar, rotor eccentricity faults, end ring faults, and load faults. The aim of this study was to observe the effect of brush fault within a permanent magnet DC (PMDC) motor. Carbon contact brushes are used in PMDC motors to transmit electrical current from the stator of the motor to the rotor of the motor, ensuring the rotation of the commutators. Over time, the carbon contact becomes worn down from commutators continually moving across them. As the contacts length is decreased, the spring holding it in place becomes more stretched out, putting in more effort to hold the brush in place. This introduces a resistance, referred to as a contact resistance, that can affect the motor speed and performance. Changes in speed and resistance can be measured and observed, and curves can be fitted to their relationship with statistical significance. We can also create a simulation method using basic differential equations that describe the motor and introducing random noise to the simulation with generation of random numbers for the motor parameters. Finally, a confidence interval is generated, and eminent motor failure can be predicted when values measured values stray from the simulated path. Erratic motor behavior can also be observed at the point of eminent motor failure

A DUAL INPUT BIDIRECTIONAL POWER CONVERTER FOR CHARGING AND DISCHARGING A PHEV BATTERY

This thesis looks at a new design for a dual input bidirectional power converter (DIBPC) for charging and discharging a PHEV battery. The design incorporates a power factor correcting rectifier aimed at optimizing the battery charging efficiency from either a 120 VAC or 240 VAC source or discharging the battery to a usable AC voltage at 120 VAC. For simplicity and cost-effectiveness, the DIBPC is constructed using a standard IGBT 6-pack intended for motor control. The DIBPC is designed specifically to provide efficient operation with 120 VAC and 240 VAC inputs while achieving a very low THDI. The DIBPC also needs to be able to provide AC output power at 120 VAC with the flexibility to output at 240 VAC in the future. The DIBPC was tested first in simulation, and then in experimentation. The DIBPC consists of two portions, an AC/DC converter and a DC/DC converter. Although both were simulated, only the AC/DC converter was constructed. Testing under various load values and in each mode of operation provided ample data to show the DIBPC can meet all design goals. When operating as a rectifier, the DIBPC produces between 7.4% and 13.35% THDI and a DC voltage ripple of 8 VP-P or less at 400 VDC. At 120 VAC and 240 VAC an efficiency of 84.5% and 94.6% was achieved, respectively. When operating as an inverter, the DIBPC produces less than 6% THDV and 7% THDI, while outputting a voltage between 114 and 128 VRMS. Overall, the THDI in the charging mode easily meets and exceeds all standards and design constraints set forth, including IEC 61000-3-4. The efficiency with a 120 VAC input, however, is less than expected - about 84%