Towards Improved Reliability Indices using Waveform Distortions in Distribution System

The reliability of power supply to consumers is the main factor that is to be considered while designing, planning and operation of a distribution network. This problem can be solved by incorporating distributed generation (DG) at the consumer side itself. In order to enhance service availability, power quality, reliability, and loss reduction, DG is positioned optimally at the consumer end within the system. The optimal DG location and size is to be calculated in such a way that the total loss in the system should be minimal and cost savings should be maximal. In this study, for the investigation of effects of DG on reliability of distribution system, a practical 11 KV feeder with 41-bus, was employed. The selected practical feeder is modelled using the power world simulator (PWS) software and reliability of the system is verified by calculating various reliability indices such as system average interruption frequency index (SAIFI), system average interruption duration index (SAIDI), customer average interruption duration index (CAIDI), average system utility index (ASUI) and average service availability index (ASAI). After applying proposed loss sensitivity factor (LSF) method, the active and reactive power loss reduction are 41.30 % and 38.64 % respectively, least bus voltage is enhanced to 0.9405 pu from 0.8978 pu and the reliability indices are also improved.

Ensuring the provision of high-quality and dependable power supply to customers stands as a paramount responsibility within the realm of power systems. The concept of restructuring the power system emerges as an efficient approach to deliver economically viable and uninterrupted power supply. The assessment of power system reliability hinges on various factors, with the reliability index serving as a pivotal metric, dependent on both system security and adequacy. To enhance the reliability index, strategically locating FACTS devices becomes essential, a task facilitated through power flow analysis with specified constraints, pinpointing the weakest points through Genetic Algorithm-driven fast-acting device placement. The correlation between DG establishment and the reliability index was meticulously calculated, further bolstered by the introduction of a Derated Forced Outage Rate for enhanced performance assessment. In the pursuit of heightened power system reliability, sequential simulations prove invaluable, particularly in minimizing Expected Energy Not Supplied (EENS) and improving overall system reliability. The results obtained through sequential simulations underscore the effectiveness of this approach within bulk electrical systems. The installation of multiple FACTS devices in the system's weakest areas facilitated EENS computation, coupled with the assessment of related reliability indices such as system frequency and system duration. This approach not only enhances system reliability but also promotes the economic operation of both transmission and distribution.The simulation results substantiate the alignment of power system reliability objectives in deregulated power systems with the required standards, advocating for the restructuring of power networks. The reliability assessments, driven by the optimal placement of DGs and FACTS devices, reveal substantial improvements in system reliability, underscoring the pivotal role of these technologies in enhancing overall power system dependability.

A distribution system is the part of an overall power system which links the bulk system to the individual customers. The primary goal of any distribution system is to supply reliable and quality power to the consumers economically. Therefore reliability indices like system average interruption duration index (SAIDI), customer average interruption duration index (CAIDI), average service availability index (ASAI) and voltage stability index are the important performance indices of a distribution system which need to be satisfied from the customer point of view. The edifice of distribution system automation is fast and reliable communication control technologies leading to reliable power delivery to the customers. Also the ever expanding power demand is increasing the complexity of power system, necessitating highly reliable, secure and efficient distribution system. An attempt has been made in this paper to assess the impact on reliability due to automatic feeder reconfiguration for smart distribution purposes.

Our daily life is supported by powerful information networks which are composed of computers and communication equipments. If they do not work correctly or completely, our daily life would be surely confused. Under some circumstances safety could not be kept. Uninterruptible Power Supply (UPS) systems are commonly equipped to supply stable power to the critical loads, for example, large computer center telephone and telecomnication center, aviation control system and so on. Several kinds of UPS systems are now used in many important fields as the above mentioned. But they almost do not have been evaluated numerically based on system reliability.This paper evaluates MTBF of parallel redundant UPS systems, and reports MTBF of 2 sets of parallel redundant UPS system is lower than that of 3 sets of parallel redundant UPS system under some circumstances. Continuous power supply reliability of the UPS system with bypass and uninterruptible transfer switch is much higher than any other UPS system without bypass circuit and uninterruptible transfer switch. And then the last some highly reliable parallel operation technology are shown.

The article analyzes the regulations for assessing the quality of electricity supply, which is especially important for distribution system operators in terms of the introduction of incentive tariffs. The influence of the increase in the installed capacity of RES on the normative indicator of the duration of power supply interruptions — SAIDI was determined, and also the change of the indicator of the average duration of power supply failures (min) from the year and region was analyzed. Correlation analysis was performed for a number of operators of distribution systems for the impact of renewable energy generation on SAIDI, in the periods 2013—2016 and 2017—2020. It is determined that in the period from 2013 to 2016, the growth of the installed capacity of renewable energy sources had almost no effect on the normative indicator of the duration of power outages — SAIDI. And since 2017, due to the choice of sub-optimal connection points and / or a sharp increase in the installed capacity of renewable energy sources, SAIDI is increasing. Graphs of dependence of increase of the established capacity of renewable energy sources on areas of Ukraine in the period from 2013 to 2020 are constructed. For clarity, a graph of the dependence of the installed capacity of renewable energy sources for a number of distribution system operators on the year of implementation of such capacity for two periods, namely 2013—2016 and 2017—2020. The schedule of dependence of the annual indicator of average duration of failures in power supply on areas of Ukraine in the period from 2013 to 2020 is constructed. The regions with the largest installed capacity of renewable energy sources as of the end of 2020 were selected for plotting and correlation analysis. The conclusion on the influence of renewable energy sources on the reliability of electricity supply to distribution system operators is made.

Assessment of customer power supply reliability is an important part of distribution system operation and planning. Distribution system reliability assessment is a measure of continuity and quality of power supply to the consumers, which mainly depends on interruption profile, based on system topology and component reliability data. The paper mainly describes about the radial Distribution system reliability is evaluated in two methods. One by placing capacitor at weak voltage nodes for improvement of voltage profiles, reducing the total losses. Second way by improving reliability indices by placing protective equipment (isolators) in the feeder. This paper present an effective approach for real time evaluation of distribution power flow solutions with an objective of determining the voltage profiles and total losses. To improve the voltage profiles and reducing losses by placing capacitors at weak voltage profile nodes using Particle Swarm Optimization (PSO) technique. The Distribution System Reliability Indices are also calculated for the existing radial distribution system before and after placement of isolator. In this paper we have considered the load diversity factor for analysis of load data for real time system. Two matrices the bus-injection to branch-current matrix (BIBC), the branch-current to bus voltage matrix (BCBV) and a simple matrix multiplication are used to obtain power flow solutions. This paper also presents an approach that determines optimal location and size of capacitors on existing radial distribution systems to improve the voltage profiles and reduce the active power loss. The performance of the method was investigated on an 11kV real time Upadyayanagar radial distribution feeder as system of case study. A matlab program was developed and results are presented.

Optimal reconfiguration of electrical distribution systems considering reliability indices improvement

A Data Center can consist of a large group of networked servers and associated power distribution, networking, and cooling equipment. All these applications consume enormous amounts of energy which result in a significant increase in energy inefficiency problems. One of the causes of Data Center energy inefficiency power distribution is from the uninterruptible power supply (UPS). The UPS system is an alternate or backup source of power linking between mains power supply and end critical loads in order to provide back-up power and protection for the sensitive load. This study attempts to answer the question of how can future UPS topology and technology improve the efficiency of Data Center. In order to analyze the impact of different UPS technologies and their operating efficiencies, a model for a medium size Data Centre is developed, and load schedules and worked schematics were created to analyze and test the components of each of the UPS system topologies.

Since the auxiliary three-phase oil pump motor of ship machine set needs uninterrupted power supply(UPS), the oil pump motor needs to be switched to UPS equipment for power supply in case of power loss of the generator. In order to realize the smooth transition of the oil pump motor when switching to UPS, the three-phase voltage output by the inverter in UPS needs to be in the same frequency and phase as the generator voltage. In this paper, the basic working principle of UPS is introduced, the advantages and disadvantages of two phase-locked loops for tracking phase are analyzed, and a phase-locked loop(PLL) based on second-order generalized integrator is selected to be used in inverter. Finally, the feasibility of this method is verified by experiments.

This paper is concerned with the control of a line interactive Uninterruptable Power Supply (UPS) system in a Microgrid. In grid connected mode, power can be imported from the grid to charge the battery or it can be injected into the grid to boost the power supplied by the Microgrid. In island mode, the UPS supplies local critical load in parallel with other sources. Power flow is controlled using the frequency and voltage drooping technique to ensure seamless transfer between grid connected and parallel islanding modes of operation. When the power is imported from the grid, an outer voltage controller that regulates the DC link voltage sets the power demand for an inner power flow controller. The outer voltage loop is designed with the aid of small signal analysis which has been used to model the dynamics of the inner power flow controller. Due to the limited DC link capacitance, the drooping coefficients are chosen carefully to limit transient circulating active power from the grid to the UPS module or from one UPS module to another. The traditional way of measuring active and reactive power which is based on using a low pass filter is replaced by a real time integration method which is shown to improve the response of the controller. A virtual impedance is utilized in grid-connected mode to improve output current THD. Experimental results of two 60kW line interactive UPS modules are provided to validate the design.

An increasing penetration of distributed generation (DG) in distribution systems has led to the concept of Microgrid. Reliability enhancement is one of benefits of Microgrid system because it can operate in both grid-connected mode and islanding mode. However, system protection is one of the important issues in Microgrid planning because operation mode and location of protective devices have effect on system reliability. This paper will present an algorithm to determine an optimal placement of protective devices in Microgrid system for improving reliability indices considering operation mode. The objective functions are to minimize three reliability indices that are system average interruption frequency index (SAIFI), system average interruption duration index (SAIDI) and energy not supplied (ENS). The proposed algorithms for solving the optimization problem and reliability evaluation are Particle Swarm Optimization (PSO) and Monte Carlo Simulation (MCS), respectively. Simulation results of implementing the proposed approach on modified feeder4 of RBTS bus 6 show the performance of this method.

This paper presents the reactive power compensation with UPS. The most effective power quality improvement solution is analyzed in an uninterruptible power supply systems. The conventional UPS has three stages i.e rectifier converts AC to DC, Battery to store DC and Inverter to convert DC to AC. A novel technique has implemented in off-line UPS. The power is delivered to load via by-pass switch when main supply is available. Inverter does not operate during this period. So inverter function is same as conventional inverter. To overcome this problem, static change over switches has proposed. Hence it will get better voltage regulation and loss less in distribution system. The performance of simulation result is analyzed using MATLAB/SIMULINK.

Pantograph arcing with AC supply generates transients, cause asymmetries and distortion in supply voltage and current waveforms and can damage the pantograph and the overhead contact line. The asymmetry generates a net dc component and harmonics, which propagate within the traction power and signalling system and causes electromagnetic interference. Unlike DC-fed systems (Part I), the arcing in ac supply is complex because of the zero crossing of currents and voltages. In this paper, we discuss the mechanisms of sliding contact and arcing between pantograph-contact wire using the experimental setup described in Part I. Influences of various parameters and test conditions on arcing phenomenon and their signature patterns on the supply voltage and current waveforms are presented. It is shown how the arcing mechanism and corresponding asymmetry in the voltage and current waveforms are governed by line speed, current, supply voltage, inductive load, and pantograph material. The asymmetry in the current waveform is mainly due to the difference in the duration of successive zero-current regions and uneven distortion of the waveshapes. This, in turn, creates the asymmetry in the voltage waveform. The findings presented in this paper could be beneficial for coming up with appropriate mitigation techniques from the electromagnetic interference due to pantograph arcing in AC traction systems.

In the article, based on the concept of increasing the reliability of the formed image of the complex of technical means for ensuring the operation of an unsolicited measuring station of the network of stations of the ground control complex, a solution is proposed for choosing the general scheme of an uninterruptible power supply as part of a complex of technical means of unsolicited measuring systems. The uninterrupted power supply system is designed to automatically provide a set of technical means for ensuring the operation of a non-demand measuring station with a guaranteed and uninterrupted power supply in accordance with the indicators of reliability, autonomy and quality of electricity specified in the terms of reference. A procedure for selecting the constituent elements of an uninterruptible power supply is proposed, the main stages and composition of the protection means for the power supply network are considered. A block diagram of protection over the power supply network is presented. It is noted that structurally, the uninterruptible power supply should be able to be placed both in a stationary room and in a block container.

Nowadays the use of Uninterruptible Power Supply (UPS) is common because UPS is able to provide a backup electrical power when the main source is disconnected or interrupted. With the use of a UPS, the supply of electrical power to the system will not be interrupted. When the UPS operates, the voltage go through dual conversion process, from AC to DC by the rectifier and from DC to AC by the inverter. The DC voltage in the UPS is used to supply the battery charger and the AC voltage is used to supply the load system. The switching process of the inverter can produce disturbances at high frequency. In this study, a 1 KVA UPS is connected to a capacitive load 3.6 µF, 7.2 µF, 14.4 µF and 28.8 µF which generate the highest disturbances voltage of 309.53 mV at a frequency of 9.8 kHz at a load of 28.8 μF and the lowest of 1.33 mV at a frequency of 110.6 kHz at a load of 3.6 μF. The disturbances voltage occur at three dominant frequencies of 19-24 kHz, 35-44 kHz and 105- 114 kHz and increases as the increase of capacitive load level.