What Causes Time Delay In Uninterruptible Power Supply?
What Are The Impacts Of Time Delay In Uninterruptible Power Supply?
How Can Time Delay In Uninterruptible Power Supply Be Reduced?
What Is The Existing Knowledge And Achievement As Far As Reducing Time Delay In Uninterruptible Power Supply Is Concerned?
Applications of modern power electronics handle a wide range of power processing and control that emanate from the milliwatt level of management of power on chip to megawatt level of utility power system. In as much as the analog control still dominates at lower level power which is power below hundreds of watts and the frequencies of switching being higher than hundreds of kilohertz, the development and advancements in the digital signal processors and programmable logic devices have provided great capability and control flexibility, offering attractive characteristics more specifically for those applications which involve sophisticated tasks [Abdennadher et al. 2012].
Uninterruptible Power Supplies are broadly used in the supply of high quality alternating current power which is continuous and free from disturbance to critical loads among them computers, medical equipment and systems used in communication. A fast transient response during the loading step change is as important as excellent steady state performances with regard to the regulation of the voltage and the total harmonics distortions which does not depend on the disturbances from the unknown load [Wu, Rangan and Zhang 2016]. Numerous techniques for high performance feedback control among them predictive control, dead-beat control as well as multi-loop feedback control have been offered for discussion and in-depth elaborations have been carried out. These techniques have been used in the illustration of fast dynamic response and high quality output voltage. However, the disadvantages below play a role in limiting the benefits of the techniques mentioned:
The demand of numerous state variables inclusive of both currents and voltages for sensing in order to stabilized the close loop system as well as attains dynamic stiffness. The use of more high resolution sensors lead to higher costs of the supplies systems [Alotto, Guarnieri and Moro, 2014, pp. 325-335].
Minimized chances of elimination of the high order harmonic distortions that result from non-linearity and unbalance-There is intrinsic limitation of the controller bandwidth as a result of digital implementation.
The notion that every individual can individually be compensated forms the basis of the working of selective harmonic compensation. Such a method is aimed at excellent steady state output and can be implemented either in the synchronous rotating frames or in the stationery frame [Jiang et al. 2012, pp. 4711-4722]. Furthermore, the controller costs is increased by the excessive computation besides making its practicality less achievable especially in cases where the harmonics are more than the 13th order and need to be compensated.
The repetitive controller which comes from the internal model principle has been described as an ideal solution that can be used in the rejection of periodic errors that can be found in a dynamic system. The main mechanism of such a technique is the integration of modified internal model through proper construction of the feedback loops or one of very few time units of delay. This results in the elimination of the periodic errors [Bajpai and Dash 2012, pp. 2926-2939].
Numerous repetitive control strategies have been set in place for use in UPS inverters also called voltage constant frequency inverters, grid connected inverters, active power filters, PMW rectifiers and boost DC-DC converters. Of all these methods, the conventional RC structure that is based on the positive feedback loop of a fundamental period unit of delay has become the most popular owing to its straightforwardness and ideal capability in the rejection of harmonics in which each and every harmonic is individually compensated. This is despite the fact that the control action is pushed forward by a single fundamental period in a corresponding manner which tends to slow down the dynamic response in an unavoidable manner [Mohod and Aware, 2012, pp. 118-125].
Two main reasons are attributed to the rapid growth in the demand for Uninterruptible Power Systems: the need of integrity of the supply of power to an equipment has increased due to the need to protect it from damaging of the components as well as corruption of the data which may culminate into complete failure of the supply of power and the second reason being that the equipment may itself serve as source of interference for example the case of harmonic currents that are produced by for example thyristor regulators. Moreover, there os a trend that has been developed and aims at lowering the level of operating voltage in digital systems from 5V to about 3.3V so as minimise the consumption of power [Rodriguez et al. 2013, pp. 1003-1016]. This leads to a much greater sensitivity to the interference that may occur to the systems of power supply.
There are various main types of disturbances namely overvoltage surges, under voltage surges and outages or called blackouts among other as discussed below:
Outages or blackouts are a type of disturbance that have been found to takes between about 5000 to 6000 times a year with most of the current computers being found to be in a position up challenge outages of 20mses or even higher while others are still less tolerant. A number of the failures that have not statistically been registered lie between 20 msec and 10 msec. these failures can have as much devastating impacts as the longer outages should they take place [Serban and Marinescu, 2014, pp. 5010-5020]. Furthermore, there are outages that are generated by users which can also be added to the list of power line failures for example the removal of fuses.
In this failure, the strength of the voltage is found to be relatively higher that the nominal value for a period of a few cycles that are managed by the power supply. They results from an abrupt reduction in the demand for power or otherwise disturbances in the power distribution system. The power stations need to make the necessary adjustments to the voltage in line with the demand. Such a process is quite slow and hence resulting into a time lag between the variations in the demand for power and the reaction [Lee and Song, Samsung Electronics Co Ltd, 2015]. Moreover, surges may also result from short circuits that are within the vicinity of a load that is perceived to be sensitive. Upon a brief breakdown, there is a peak up of the voltage to twice or at other time thrice the nominal voltage within a period that ranges between 100 usec and 1 msec. An overvoltage of 15% is usually tolerable and any values beyond this value may result into the damage and hence shortening the life of the equipment [Abdennadher et al. 2012].
Mechanical switching of large loads: These results into the bouncing of the contacts of the circuit breaker that leads to oscillations which range between 400 Hz a 5 kHz. The disturbances are reflected in the power lines and are able travel over long distances with a lot of ease.
These are power disturbances that are superimposed on the normal 50Hz or sometimes 60 Hz waveforms and take place occasionally rather than on a competitive basis. Explanation behind spikes could be attributed to lightning strikes in which there are voltages impulses which run into numerous thousands of Voltages within a duration that last few milliseconds and some may even go for 100msec. these pulses are then transmitted throughout the network and get into the most sensitive parts of the various electronic devices. Owing to these spikes, there are a lot of damages that have been experienced on numerous motherboard and hard disks [Lim et al. 2014, pp. 4142-4151].
This is a voltage that is essentially lower than the required nominal value for a few cycles and tends to be the most common type of fault. Under voltage circumstances results from an abrupt increase in the demand of power within the electronic systems vicinity or as frequently happens of the mains voltage at the various power stations. This results from peak demands that are experienced. Moreover, huge power consumers are able to generate overload in the networks the case of the starting current of a lift that can be attributed to the under voltage in a building and thus extending to a network or computer system [Vazquez et al. 2014]. To the tune of 20% of the conditions of overvoltage can sufficiently be handles using the state of the art machines even though very high under voltages may results into permanent and severe damage of such systems.
This defines noise of very high frequency that may be transferred through the various power lines or be radiated from the source for example the supplies of switch mode power.
This is a distorted waveform of a voltage that is composed of components at harmonic frequencies which are found on a sustained basis which is in most case low order multiples of the frequency of the line [Jiang et al. 2012].
This defines a repetitive chopped waveforms of the supply voltage among them those that have an association with the regulators of the thyristor voltage.
A statement that was made by K. Neumann signified the significance of study along the line of UPS systems. PS systems applications have been found to start from small power among them electronic control systems, stand-by lighting, emergency lighting, escalators and other important services and equipment. Data losses in an access control system are it in a medium or small sized company may lead to devastating loss of information that would call for a tremendous manual work to retrieve and once again install the system [Jayaprakash et al. 2014, pp. 1295-1303]. In most case, stand-by batteries or even generators powered by diesel are offered for emergency.
Various configurations are demanded for the different sectors in which the UPS systems are applied. The load parameters among them sensitivity, power demand and load variation play a major role when it comes to specific demands on the UPS systems. Following this classification of loads, there are two main categories of UPS systems with respect to the capability of handling power and the response time. Other factors that have been considered at the stage of designing include the availability of weight and space [Kontorinis et al. 2012, pp. 488-499]. The different kinds of UPS systems in use are as shown in the figure below. As can be observed in the figure, the internal arrangement which is built system is often in small equipment which may also be portable. For the care of external arrangement in which the UPS system is connected as a separate unit to the equipment, there are various alternative schemes as discussed below:
The first one is a short summary of the most common external UPS systems is provided to illustrate the major differences besides elements which are shared in common. The second aspect is the internal configurations which are internal and are derivatives of a classical or on line system.
Time delay in UPS systems remains a major challenge as it has the capability of culminating into various negative impacts to even the smallest of all the companies [Buck et al. 2012]. This raises the need to come up with strategy that would ensure the delay that ranges between 100 msec and 1nsec is minimized to ensure continuous running of the available systems and protect loss of data that may lead to severe loss of information. This study will justify among other findings that the choice of a UPS system plays a role in the reduction of the delay time. UPS systems have various configurations and components that have different designs. An appropriate choice on a type of UPS system may help in reducing delay times as has been proposed by previous studies would be established [Kontorinis et al. 2012, pp. 488-499].
The steps that were followed during the study were very sequential the first step involved the identification of the causes of time delay in UPS systems. The relevant information was then collected using the best methods of data collection. The causes of time delay were ranked in order of prevalence. The impacts and strategies of control analysis were carried out. The results and the detailed discussion summarised the long process.
The UPS system was studied and several data collected. The various components of the system were explored extensively and their operations understood. The point at which time delay is introduced into the system was monitored and the various parameters that are responsible for the delay noted before they could be studied into more refined and comprehensive nature [Deng et al. 2013, pp. 420-429]. Each of the causes of time delay was allocated 30 minutes of in-depth analysis which was conducted mainly through experimental observations with the backing up of existing literature which offered information on what had been done by the previous scholars in related fields [Vazquez et al. 2014].
The findings from each of the causes of time delay studied formed the basis of coming up with the various strategies that could be adopted to mitigate the challenge. Data was collected through secondary sources and conclusions based on the experimental and such data were stored for use in analysis at a later stage of the study [Cortes et al. 2012, pp. 1323-1325]. The accuracy of the data was enhanced through first hand recording of the information especially of the data from the experimental set up. As with regard to data extracted from secondary sources, bias was reduced through analysis of numerous and different sources of information.
From the experiment, the possible causes of time delay in an UPS system include:
These among other reasons may lead to possible loss of data by the UPS system of an organization which may in turn lead to possible loss of vital information. The consequences would be devastating as the company would have to spend heavily on the reinstallation of another UPS system even as it struggles to retrieve the lost information. The hold-up time was found to be the main factor among all the others that play a role in the determination in the length of delay in UPS system. The hold-up time of the UPS system at the provided load is determined by the manufacturer of the system and hence can only be controlled and checked at the manufacturing stage [Bhargava, Cakir and Mai, 2012, pp. 25-30]. A choice of a UPS system that has the desired specifications and components parts is thus ideal for controlling delay times as was observed when testing the various systems that had different design specifications. It was established from the results of the experiment that systems with higher hold-up time experienced the highest delay time hence were not recommended for use in cases where minimum delay time was an element of consideration [Vasquez et al. 2013, pp. 1271-1280].
Project Planning
Research Task |
Milestone Date |
Initial Literature review and Proposal – Approved |
8th April 2018 |
Detailed Literature review |
|
UPS systems |
22nd April 2018 |
Types of disturbances in UPS systems and their causes |
6th May 2018 |
Data Analysis |
|
Causes of time delay in UPS systems |
13th May 2018 |
Identifying implications of time delay in UPS system |
22th May 2018 |
How to minimize time delays in UPS systems |
1st June 2018 |
Conclusions |
|
Summarizing findings |
10th June 2018 |
Recommend the method of minimization of time delays |
24th June 2018 |
Conclusion
A fast transient response during the loading step change is as important as excellent steady state performances with regard to the regulation of the voltage and the total harmonics distortions which does not depend on the disturbances from the unknown load. Power fluctuations in the battery, charging condition of the battery, the hold-up time of the UPS system at the provided load and the time taken by the UPS system to shut down are the possible causes of time delay in an UPS system. The hold-up time was found to be the main factor among all the others that play a role in the determination in the length of delay in UPS system. The hold-up time of the UPS system at the provided load is determined by the manufacturer of the system and hence can only be controlled and checked at the manufacturing stage. These causes of delay time may lead to possible loss of data by the UPS system of an organization which may in turn lead to possible loss of vital information.
References
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Bhargava, M., Cakir, C. and Mai, K., 2012, June. Reliability enhancement of bi-stable PUFs in 65nm bulk CMOS. In ‘Hardware-Oriented Security and Trust (HOST), 2012 IEEE International Symposium’ on (pp. 25-30). IEEE
Buck, M., Haulick, T., Hetherington, P.A. and Zakarauskas, P., Nuance Communications Inc, 2012. Multi-channel adaptive speech signal processing system with noise reduction. U.S. Patent 8,194,872, 4th edn, Cambridge University Press, New York
Cortes, P., Rodriguez, J., Silva, C. and Flores, A., 2012. Delay compensation in model predictive current control of a three-phase inverter. ‘IEEE Transactions on Industrial Electronics,’ 59(2), pp.1323-1325
Deng, W., Liu, F., Jin, H. and Wu, C., 2013, July. SmartDPSS: Cost-minimizing multi-source power supply for datacenters with arbitrary demand. In Distributed Computing Systems (ICDCS), 2013 ‘IEEE 33rd International Conference’ on (pp. 420-429). IEEE
Golden, B., Lewis, K. and Corsell, P.L., GRIDPOINT Inc, 2012. Modular energy control system. U.S. Patent 8,103,389
Jayaprakash, P., Singh, B., Kothari, D.P., Chandra, A. and Al-Haddad, K., 2014. Control of reduced-rating dynamic voltage restorer with a battery energy storage system. ‘IEEE transactions on industry applications,’ 50(2), pp.1295-1303
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Jiang, S., Cao, D., Li, Y., Liu, J. and Peng, F.Z., 2012. Low-THD, fast-transient, and cost-effective synchronous-frame repetitive controller for three-phase UPS inverters. ‘IEEE Transactions on Power Electronics’, 27(6), pp.2994-3005
Kontorinis, V., Zhang, L.E., Aksanli, B., Sampson, J., Homayoun, H., Pettis, E., Tullsen, D.M. and Rosing, T.S., 2012, June. Managing distributed ups energy for effective power capping in data centers. In ‘Computer Architecture (ISCA), 2012 39th Annual International Symposium’ on (pp. 488-499). IEEE
Lee, S.G. and Song, S.H., Samsung Electronics Co Ltd, 2015. Methods of charging auxiliary power supplies in data storage devices subject to power on and/or hot plugging and related devices. U.S. Patent 9,208,894, 5th edn, CRC Press London.
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Mohod, S.W. and Aware, M.V., 2012. Micro wind power generator with battery energy storage for critical load. ‘IEEE systems journal,’ 6(1), pp.118-125
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