Analysis and Recommendations for LED Catastrophic Failure Due to Voltage Stress

Light-emitting diode (LED) lighting has, compared to other types of lighting, a significantly lower energy consumption. However, the perceived service life is also important for customer satisfaction and here there is a discrepancy between customers’ experience and manufacturers’ statements. Many customers experience a significantly shorter service life than claimed by the manufacturers. An experiment was carried out in the Pehr Högström Laboratory at Luleå University of Technology in Skellefteå, Sweden to investigate whether voltage disturbances could explain this discrepancy. Over 1000 LED lamps were exposed to high levels of voltage disturbances for more than 6000 h; the failure rate from this experiment was similar to the one from previous experiments in which lamps were exposed to normal voltage. The discrepancy thus remains, even though some possible explanations have emerged from the project’s results. The lamps were exposed to five different types of voltage disturbances: short interruptions; transients; overvoltage; undervoltage; and harmonics. Only overvoltage resulted in failure of the lamps, and only for a single topology of lamp. A detailed analysis has been made of the topology of lamps that failed. This lamp type contains a different internal electronics circuit than the other lamp types. Failures of the lamps when exposed to overvoltage are due to the heat development in the control circuit increasing sharply when the lamps are exposed to a higher voltage. Hence, it is concluded that there are lamps that are significantly more sensitive to voltage disturbances than other lamp types. Manufactures need to consider the voltage quality that can be expected at the terminal of the lamp to prevent failure of lamps due to voltage disturbances. This paper therefore contains recommendations for manufacturers of lighting; the recommendations describe which voltage disturbances lamps should cope with.

PRINCIPLES OF IMPROVEMENT OF MULTILEVEL AUTONOMOUS VOLTAGE INVERTERS

The article considers the properties of the most commonly used two-and multilevel inverter topologies used in systems for converting electricity from several primary power sources into the required high-quality output voltage for low-voltage networks and high-voltage consumers. However, a common disadvantage of most known multilevel converters is the increasing complexity of power structures, an increase in the number of primary power sources, power elements, and the cost of devices as the number of their voltage levels increases. Two schemes of alternative three-level autonomous voltage inverters with a high-frequency autotransformer with a midpoint and an example of constructing their digital control system are proposed. The analysis of their work on PSpice models in the OrCAD design system is carried out. The possibility of obtaining six voltage sublevels with fewer power elements and increased output voltage quality is shown, compared to the corresponding cascade multilevel inverters. The advantages and applications of autotransformer bridge voltage inverters in terms of energy and functionality compared to well-known multilevel inverters are presented. Ref. 8, fig. 7.

Spatial Model of Optimization Applied in the Distributed Generation Photovoltaic to Adjust Voltage Levels

The main objective of this work is to develop a methodology for analyzing the quality of the voltage level in the distribution power grid to identify and reduce the violations of voltage limits through the proposition of optimal points for the allocation of photovoltaic distributed generation. The methodology uses the geographic location of the power grid and its consumers to perform the grouping and classification in spatial grids of 100×100 m using the average annual consumption profile. The generated profiles, including the grid information, are sent to the photovoltaic distributed generation allocation algorithm, which, using an optimization process, identifies the geographic location, the required installed capacity, and the minimum number of photovoltaic generation units that must be inserted to minimize the violations of voltage limits, respecting the necessary restrictions. The entire proposal is applied in a real feeder with thousands of bars, whose model is validated with measurements carried out in the field. Different violations of voltage limits scenarios are used to validate the methodology, obtaining grids with better voltage quality after the optimized allocation of photovoltaic distributed generation. The proposal presents itself as a new tool in the work of adapting the voltage of the distribution power grid using photovoltaic distributed generation.

Real Time Simulation of Power Electronics Medium Voltage DC-Grid Simulator

Power electronics medium-voltage (MV) systems must comply with the requirements defined in grid codes. These systems’ compatibility with the standards can be validated by specialized testing equipment: grid simulators. This paper presents a hardware in the loop (HiL) implementation and the simulation results of a MV multiphase DC/DC converter designed for MV DC grid emulation. By using ABB’s reliable, patented power converter hardware topology (US 10978948 B2) and by applying advanced control algorithms, the presented system can be used for special purposes, such as the emulation of fault events in a DC-grid used for the certification of other devices, or for other research goals. The presented concept of a power electronics DC-grid simulator (PEGS-DC) is characterized by high power capability and high voltage quality. In this paper, the general idea of a power electronics grid simulator applied for the testing of MV electrical systems is discussed. Then, details related to the PEGS-DC, such as its hardware topology and the applied modulation method are presented. Subsequently, the HiL setup is described. The main scope of this article focuses on model the description and presenting recorded HiL simulations.

An Evaluation of Flicker Emissions from Small Wind Turbines

It is well known that the output power from small wind turbines (SWTs) fluctuates noticeably more when compared to that from other types of dispersed generators, such as residential photovoltaic (PV) power generation systems. Thus, the degradation of voltage quality, such as flicker emissions, when numerous SWTs are installed in a low-voltage distribution system is a particular concern. Nevertheless, practical examples of flicker emissions from small wind power facilities have not been made public. This paper aims to clarify the characteristics of flicker emissions by SWTs and their severity. The measurement results at the two selected sites indicate that the flicker emissions solely caused by variable-speed SWTs with a total power rating of ~20 kW are notably lower than the upper limit, and they are at their highest when the mean total output power is approximately 3/4 of the total power rating of small wind power facilities.

Enhanced power quality using unified power flow controller systems

Electrical system frequently finds and issue due to unstable nature and power quality because of, in relation to great number of nonlinear charges. So, there is need to limit inside of these difficulties and produce fine voltage quality concerns. The Flexible Alternate Flow Transmission Systems (FACTS) are the framework made out of static gear works for the AC transmission of electrical energy. Unified_Power_Flow Controls (UPFC) are the excellent FACTS tools to attach series and shunt together and it could use for framing Power transmission sensitive and active power. Here in the paper, Unified Power Flow Control (UPFC) used to clear the voltage sink and Surge. Unified Control was developed and engineered using amplifiers and rectifiers. The real and reactive modifications in congruous control orientations at the receiver side. Use of Simulink of MATLAB checks quality of energy in the use of Unified Control.

Assessment of influence of rolling mill FC-AR electric drive operation mode on 10kV supply network voltage quality

Advanced rolling mill electric drives are based on frequency converters (FC) with active rectifiers (AR). Operation of such converters has negative impact on the in-plant power supply system. To improve the voltage quality of active rectifiers, special algorithms of pulse-width modulation algorithms are used. As a rule, the study of the effect of electric drives with FC-AR on the supply network are carried out based on simplified mathematical models that do not consider possible resonance phenomena in the power supply system and operating mode of electric drives. Thus, the aim of the paper is to assess the acceptability of such an approach. The trends of the main parameters of the rolling mill electric drives have been recorded during the rolling cycle using the IBA PDA software. The obtained dependencies values have been approximated and applied in a complex simulation model of the in-plant power supply system. It considers the parameters of the supply network, cable lines, step-down transformers, rolling mill electric drives and other electrical receivers of the shop substations. The main assumption in simulation modeling is to consider the loads of other electrical receivers in the form of constant values. The authors have studied the effect of the operating modes of the rolling mill electric drive on the electric power quality in the 10 kV distribution network of the in-plant power supply system of a metallurgical enterprise. It is found that the total harmonic distortion KU at 10 kV sections of the main step-down substation of a metallurgical enterprise is changing in a nonlinear manner in the dynamic modes of acceleration and deceleration of electric drives. The nature of the coefficient KU also depends on the presence of resonance phenomena in the frequency response of the medium voltage supply network. The obtained results prove the need to consider the operating modes of electric drives when studying the influence of electric drives with FC-AR on the quality of the supply network voltage. in case we conduct experimental research using the equipment of the enterprises, as well as during theoretical research using mathematical models. The adequacy of the simulation model has previously been confirmed by experimental data and previous studies.

Comparative study of Different Topologies of Solar Photovoltaic fed Impedance-Source Inverter based Dynamic Voltage Restorer

All customers require quality voltage, quality current and quality power from the utility, but usage of nonlinear loads generates voltage sag, swell and harmonics. This work examines the solar energy based various topologies like 3-Leg, 4-Leg, and 6-Leg Dynamic Voltage Restorer (DVR) for minimizing the voltage swell. To get most prominent power from the solar system Perturb & Observe (P&O) scheme is also used. The most famous topologies are approved utilizing MATLAB/SIMULINK programming to limiting voltage swell. The gained results are comparable nonetheless even possibly better in 6-leg PV-ZSI-DVR diverged from 3-leg and 4-leg PV-ZSI based DVRs.