Inter national J our nal of Electrical and Computer Engineering (IJECE) V ol. 10, No. 6, December 2020, pp. 6233 6243 ISSN: 2088-8708, DOI: 10.11591/ijece.v10i6.pp6233-6243 r 6233 Implementation of a grid-tied emer gency back-up po wer supply f or medium and lo w po wer applications Dhiman Cho wdhury 1 , Mohammad Sharif Miah 2 , Md. F er oz Hossain 3 , Uzzal Sark er 4 1 Department of Electrical Engineering, Uni v ersity of South Carolina, Columbia, United States of America 2, 3, 4 Department of Electrical and Electronics Engineering, Daf fodil International Uni v ersity , Bangladesh Article Inf o Article history: Recei v ed Jul 1, 2019 Re vised Mar 23, 2020 Accepted Mar 31, 2020 K eyw ords: Back-up po wer supply Boost con v erter Changeo v er relay IPS Push-pull in v erter UPS ABSTRA CT Emer genc y back-up po wer supply units are necessary in case of grid po wer shortage, considerably poor re gulation and costly establishment of a po wer system f acility . In this re g ard, po wer electronic con v erters based systems emer ge as consistent, properly controlled and ine xpensi v e electrical ener gy pro viders. This paper presents an imple- mented design of a grid-tied emer genc y back-up po wer supply for medi um and lo w po wer applications. There are a rectifier -link boost deri v ed DC-DC battery char ging circuit and a 4-switch push-pull po wer in v erter (DC-A C) circuit, which are controlled by pulse width modulation (PWM) signals. A changeo v er relay based transfer switch controls the po wer flo w to w ards the utility loads. During of f-grid situations, loads are fed po wer by the proposed system and during on-grid situations, battery is char ged by an A C-link rectifier -fed boost con v erter . Char ging phenomenon of the battery is controlled by a relay switched protection circuit. Laboratory e xperiments are carried out e xtensi v ely for dif ferent loads . Po wer quality assessments along with back-up du- rations are recorded and analyzed. In addition, a cost allocation af firms the economic feasibility of the proposed frame w ork in case of reasonable consumer applications. The test-bed results corroborate the reliability of the research w ork. Copyright c 2020 Insitute of Advanced Engineeering and Science . All rights r eserved. Corresponding A uthor: Dhiman Cho wdhury , Department of Electrical Engineering, Uni v ersity of South Carolina, SC 29208, Columbia, United States of America. Email: dhiman@email.sc.edu 1. INTR ODUCTION Modern po wer system architecture inte grates with sustainable and definiti v e po wer electronic con v er t- ers consisted of ef fectual circuit structures and stable operational characteristics . These con v erters are generally realized and configured as switching netw orks with acti v e and passi v e switching modules, po wer transfer de- vices and circuit constituents lik e resistor , capacitor , inductor etcetera. The infrastructure comprises control loops which feed switching signals to the con v erter circuit. These switching con v erters based po wer generation and distrib ution models can w ork in both grid-connected and islanded modes. In an y case, these con v erters can perform as alternati v es to t h e traditional po wer generation and distrib ution netw orks. Man y re gions across the w orld f all victim to grid po wer shortage, frequent distrib ution f ailure, v ery poorly re gulated supply , glitches in the constituent po wer sub-stations and e xpensi v e i nfrastructure. In t he e v ents of grid po wer una v ailabil- ity , emer genc y utility loads (also kno wn as critical loads) can be supplied po wer by these uninterruptible and continual po wer sources. Thereby , practitioners and researchers indulge themselv es in designing and imple- menting po wer electronic con v erters of dif ferent topologies and architectures for ensuring ef fecti v e supply of electrical ener gy to consumers. Moreo v er , these con v erter netw orks are deplo yed in de v eloping ef ficient re- ne w able ener gy s o ur ces enabled po wer systems and scalable microgrids, as reported in [1-4]. These microgrid J ournal homepage: http://ijece .iaescor e .com Evaluation Warning : The document was created with Spire.PDF for Python.
6234 r ISSN: 2088-8708 technologies e xtend the horizon of clean and unw a v ering electrical ener gy generation and supply incorporating the cutting edge premises of po wer electronics. In this article, a medium and lo w po wer utility back-up system is presented, which is de v eloped using po wer electronics and control de vices and methodologies. The system design, equi v alent mathematical models of the switching con v erter circuits and obtained PLECS simulation results of the system are reported in [5]. The proposed research design consists of a battery-sourced 4-switch push-pull in v erter circuit. Thi s po wer in v erter unit feeds ener gy to the consumer end when the mains supply is una v ailable. A DC-DC boost con v erter char ges the battery . The grid connection of the designed frame w ork is substantiated through the rectifier -link source end of the battery char ger . An electrical isolation at the i n put terminal of the battery char ger is implicated, which steps-do wn the grid v oltage (230 V r .m.s. to 12 V r .m.s.) and the con v erter produces a suitable v oltage le v el (24 V DC) to char ge the battery . In this proposed system, the char ger maintains a char ging v oltage twice the nominal battery v oltage. The switching operation of the DC-DC boost con v erter is controlled by high frequenc y (40 kHz) PWM signals. The switching frequenc y is maintained as such to reduce the current ripples, s ize of the filter components and switching de vice conduction losses. The con v erter operates in continuous conduction mode (CCM), which m eans the a v erage inductor curre nt is al w ays greater than the ripple component and the current does not go ne g ati v e during the entire c ycle of operation. A 4-switch push-pull in v erter of fering a high current dri ving ability is used as the ener gy feeder in case of grid po wer f ailure. Snubber components connected at the switching de vices reduce o v erall dv dt ef fects during circuit operation. At load end a 50 Hz center -tapped step-up transformer is located to generate suitable range of utility v oltage and pro vide g alv anic isolation between the po wer supply port and consumer port. Finally , an L-C lo w pass filter is designed at the load side. The in v erter switches are controlled by tw o compl ementary fix ed duty ratio PWM signals of the mains line frequenc y (50 Hz). During on-grid condition, the loads and the battery are fed po wer by the grid and the char ger , respecti v ely . During of f-grid condition, the customized po wer supply system deli v ers po wer to the loads. The po wer transfer switching from grid to the customized po wer supply system is automatic and instantaneous, which means no humane in v olv ement is required and no considerate delay is compromised. F or this transfer application, a changeo v er relay with a switch operating rate of 3-5 ms is emplo yed here. There is a relay switching circuit to control the char ging process of the battery . If the battery v oltage is at its rated v al ue (12 V), the char ge controller disconnects the battery from the char ger , and thus pre v ents the o v er -char ging phenomenon. There are a number of research w orks and associated e xperiments conducted to implement re liable po wer supply frame w orks based on po wer electronic means, such as [6, 7]. In these w orks, inno v ati v e designs of po wer in v erters are articulated. Moreo v er , a high g ain switched-coupled-inductor -switched-capacitor step- up con v erter topology for practical applications is presented in [8]. In addition, se v eral no v el designs of DC- A C con v erters for industrial applications are reported in [9-26]. High sending-end po wer f actor and reduced v oltage and current THD are significant features of a ef ficient po wer system. The proposed system pro vides good sending-end po wer f actor and lo w v oltage and current THD v alues, as obtained from the laboratory assessments. Se v eral po wer electronic systems r eporting po wer f actor impro v ement and THD reduction in case of non-linear loads are presented in [27-30]. In [5], a state a v eraging model of the battery char ging circuit is deri v ed and a Laplace domain transfer function is determined from the time domain model. Additionally , the in v erter circuit is analyzed as a switching con v erter model in [5]. In this article, e xperimental test results of the proposed design are presented. A test-bed of dif ferent A C utility loads rated from 60 W to 250 W is configured for e xperiments. Sending-end po wer f actor , input-output po wer quantities (v oltage and current) with the associat ed THD v alues, utility back-up po wer durations and po wer ef ficiencies in accordance with load v ariations are e v aluated. An o v erall cost estimation is presented as well. From literature re vie ws, background study and state-of-the-art in v estig ations, it can be implied that reliable and economically feasible po wer electronics based clean and alternati v e ener gy solutions are essential in modern po wer systems. In re g ard to this prospect, this article presents a grid-connected emer genc y back-up po wer system pro viding a cost-reasonable medium po wer architecture for frequent consumer and industrial ap- plications. The frame w ork proposes custom engineered PWM signal generation circuits, po wer in v erter circuit and relay based switching circuits. The proposed design is simpler and more cost-ef fecti v e than those reported in [9-26] with a potential ef ficienc y merit. The in-depth e xperimental v alidations af firm the applicability and major contrib utions of the proposed research w ork. The remnant of the manuscript is or g anized as follo ws. Section 2. presents the o v ervie w of the pro- Int J Elec & Comp Eng, V ol. 10, No. 6, December 2020 : 6233 – 6243 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 6235 posed design including the po wer transfer switching operation, relay switching circuit function and PWM gen- eration circuits manifestation. Section 3. documents the practical design considerations and laboratory based e xperimental assessments of the frame w ork. Section 4. concludes the article. 2. O VER VIEW OF THE PR OPOSED DESIGN The design of the de v eloped grid-tied emer genc y back-up po wer supply system for medium and lo w po wer applicati ons is reported in [5], which is presented here by Figure 1. The description of the system layout is documented in [5]. Ne v ertheless, a brief o v ervie w of the implemented design and its functionalities is articulated in this particular section. Figure 1. Layout of the proposed back-up po wer system [5] 2.1. P o wer transfer switching operation The transfe r switching operation from the mains line to the customized po wer circuit in case of grid po wer f ailure is implemented by a changeo v er relay fol lo wing a double pole double thro w (DPDT) switching structure. The switching operation is configured as follo ws. Direct connection relay R c 1 connects the mains po wer line to the utility load terminal. Circuit-to-load connection relay R c 2 bridges the in v erter circuit output port with the utility load terminal. R c 1 and R c 2 get acti v ated alternati v ely . Generally a relay has tw o switching terminals and one mo ving pole to shift position from one terminal to another . In this DPDT relay , the normally closed (NC) terminal or R c 2 is connected to the in v erter output and the normally open (NO) or R c 1 is connected to the grid. An y utility load is realized by the mo ving pole. In the de-ener gized state (mains po wer is absent), the load is connected to NC and con v ersely , in the ener gized state (mains po wer is present), the load gets automatically connected to NO. 2.2. Relay switching cir cuit operation An intelligible relay switching circuit is designed to control the connecti vity of the battery to i ts char ger . Therefore, this relay switched circuit unit determines the char ging operation and pro vides protection ag ainst o v er -char ge and o v er -v oltage states for the battery . The relay switching op e ration is configured in the follo wing manner . Implementation of a grid-tied emer g ency bac k-up power supply for ... (D. Chowdhury) Evaluation Warning : The document was created with Spire.PDF for Python.
6236 r ISSN: 2088-8708 If the battery v oltage is at or abo v e its rated nominal v alue, the switching circuit disconnects the char ger from the battery . Char ger connection relay R cc , is basically a single pole double thro w (SPDT) relay switching circuit which connects the battery to the char ger . Battery char ge controller consists of a comparator circuit, in which the reference v oltage V r f , k ept at 12 V , is fed from the rectifier and it is connected to a non-in v erted port, whereas the battery v oltage V B is connected to an in v erted port of an operational amplifier (op-amp). The dif ference v oltage V is V r f V B . The w ork process in op-amp happens to be: the comparator output v oltage V cmp is V sat = V = 0 V , if V < 0 and is + V sat = V + = 12 V , if V > 0 ; here V sat is the saturation v oltage. The comparator is follo wed by a relay s witching circuit, as presented in Figure 1, of which the input is the comparator output v oltage. Here NO terminal is connected to the char ger , NC terminal is open and the mo ving pole C is connected to the battery . When V cmp = 0 V , there is no current flo wing through the switching relay and the battery is disconnected from the char ger . When V cmp = 12 V , a current flo ws through the relay and the battery is connected to the char ger . 2.3. Switch contr ol PWM signal generation The switching operations of the DC-DC boost con v erter and push-pull in v erter are e x ecuted by fix ed duty ratio (0.5) PWM signals of 40 kHz and 50 Hz, respecti v ely . Analog inte grated chip (IC) SG3525A is used to generate the associated PWM signals. These PWM signals are fed into the g ate terminals of the switching de vies. T echnical features, operational principles and connection diagrams of SG3525A are reported i n details in [31]. In re g ard to maintain the trade-of f between switching loss and conduction loss of a switching de vice, 40 kHz switching frequenc y is optimized in this w ork for controlling boost con v erter . In case of the push-pull in v erter , both of the complementary 50 Hz pulses are used to control the switching operations of the in v erter le gs, le g1: Q i 1 Q i 2 and le g2: Q i 3 Q i 4 . Here 50 Hz pulses are required irrespecti v e of conduction and switching losses, since the in v erter ought to generate po wer quantities at the grid fundamental frequenc y . F or biasing the PWM generation circuits, the battery v olta g e is used. Figures 2 and 3 present the circuit schematics for 40 kHz and 50 Hz PWM signal generation, respecti v ely . T o e v aluate the performance of the de v eloped system, dif ferent types of utility loads with dif ferent po wer ratings are fed po wer by the in v erter circuit. A critical load such as a personal computer unit (HD display+CPU) is also tested to ascertain the emer genc y back-up po wer supply capability of the proposed frame w ork. Figure 2. Circuit schematic for 40 kHz PWM signal generation using SG3525A [5] Figure 3. Circuit schematic for 50 Hz PWM signal generation using SG3525A [5] Int J Elec & Comp Eng, V ol. 10, No. 6, December 2020 : 6233 – 6243 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 6237 3. EXPERIMENT AL RESUL TS AND AN AL YSIS In this article, a simple yet ef ficient and cost-ef fecti v e emer genc y back-up po wer system for re gu l ar medium and lo w po wer consumer applications is reported. Laboratory tests are conducted to ratify the v al- idation of the articulated design for practical user applications. The test-bed containing v arious utility loads with dif ferent po wer ratings are e xperimented. The w a v eforms of po wer quantities are observ ed in digital os- cilloscopes. F or measurement purposes, digital multimeter , LCR meter , THD meter , w att meter and po wer f actor meter are utilized. T able 1 sho ws the specifications of the de v eloped system components. 60 W - 250 W dif ferent types of utility loads are used for the e xperimental e v aluations. The components’ notations follo w the terms as presented in Figure 1. T able 1. Specifications of the system components to de v elop the laboratory prototype Components’ Notations Specifications T x 1 230 V - 12 V , 300 W , 50 Hz iron core step-do wn transformer with a turns ratio of N 1 : N 2 = 38 : 2 D 1 D 4 , D s , D c , D s 1 D s 4 , D sr & D r GP60-005 po wer diodes L r 0.1 mH, rectifier output filter inductance (made on a po wder core) C r 500 F , rectifier output filter capacitance (25 V electrolytic capacitor) L c 0.95 mH, boost con v erter input inductance (made on a po wder core) C c 47 F , boost con v erter output capacitance (50 V electrolytic capacitor) Q c , Q i 1 Q i 4 & Q r IRFZ44N n-channel enhancement type MOSFET with an absolute maximum on-resistance, R on =17.5 m and maximum drain current, I D = 49 A Battery 12 V (rated nominal v oltage), 7.5 A-h (capacity) and 9 V (cut-of f v oltage), Uniross UPS battery R s 1 R s 4 225 , snubber resistance (2 W resistor) C s 1 C s 4 & C sr 10 nF , snubber capacitance (ceramic capacitor , part number 103) T x 2 12 V - 230 V , 400 W , 50 Hz iron core step-up transformer with a center -tapped primary side and a turns ratio of n 1 : n 2 : n 3 = 2 : 2 : 38 L o 21.2 mH, in v erter output filter inductance (made on a po wder core) C o 470 F , in v erter output filter capacitance (250 V electrolytic capacitor) A LM324, op-amp with the biasing v oltage of V + = 12 V and V = 0 V R r 1 & R r 2 1 k and 12 k respecti v ely , resistances in the input terminal of the battery char ge control ler circuit (2 W resistor) V dd 12 V , biasing v oltage of the relay switching circuit C, NO & NC common, normally open and normally closed terminals of a 250 V , 20 A, SPDT electromechan- ical relay T ransfer Switch 250 V , 30 A, 3 ms (transfer rate) electromechanical relay Ho we v er , the detailed PLECS simulation results and associated analysis are reported in [5]. In t his article, Figure 4 presents a de vice under test (DUT) model of the system. There is a cooling f an of 12 V bias v oltage attached to the prototype to annihilate the heat of the circuit components. Ev ery electrical switching module in the circuit is associate d with heat sinks. T o e v aluate the ef ficac y , certain po wer quality measures are tak en into consideration. The sending-end po wer f actor can be defined as follo ws. P F s = P R S A = V I cos V I = cos (1) Here P R is the real po wer (W), S A is the apparent po wer (V A), is the angle between v oltage, V and current, I . Lo w po wer f actor means significant po wer loss, therefore it is rudimentary to maintain a high sending-end po wer f actor during operations of a po wer utility s ystem. In addition, harmonic distortions are determined to calculate the losses and observ e irre gularities in the w a v eforms due to unw anted harmonic contents in v oltage and current measurements. Due to presence of harmonics and sub-harmonics, distorted v oltage and current signals are fed into utility loads and the o v erall operation becomes de graded. The total harmonic distortion (THD) v alues (%) of respecti v e current and v oltage signals are measured as follo ws. I H = p I 2 2 + I 2 3 + I 2 4 + I 2 5 + I 2 6 + ::: I 1 100% (2) V H = p V 2 2 + V 2 3 + V 2 4 + V 2 5 + V 2 6 + ::: V 1 100% (3) Implementation of a grid-tied emer g ency bac k-up power supply for ... (D. Chowdhury) Evaluation Warning : The document was created with Spire.PDF for Python.
6238 r ISSN: 2088-8708 Here an y po wer quantity can be represented by L (= V and I ). L 1 is the fundamental or base frequenc y (50 Hz) component, L 2 , L 3 , L 4 , L 5 ,... are the 2nd, 3rd, 4th, 5th,... order harmonic components, respecti v ely . Figures 5 and 6 prese n t the obtained 40 kHz and 50 Hz PWM signals with fix ed 50 % duty ratio, respecti v ely . These switching signals are outcomes of SG3525A. The switching frequencies of these tw o generated PWM signals are measured as 43.1256 kHz and 51.169 Hz, respecti v ely; which are v ery close to the desired v alues. In the design, fe w v oltage con v ersion stages are present to emplo y correct quantities for most optimized po wer transformations. T able 2 manifests the v oltages at dif ferent stages of the system. Figure 4. A DUT model of the proposed design for laboratory assessments Figure 5. Generated 40 kHz switching PWM pulses Figure 6. 50 Hz switching PWM pulses in oscilloscope Int J Elec & Comp Eng, V ol. 10, No. 6, December 2020 : 6233 – 6243 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 6239 T able 2. V oltage le v els at dif ferent stages Stage V alue (V) Mains Line (grid) 230 (r .m.s.) Step-Do wn T ransformer Output 12.1 (r .m.s.) Rectifier Output 12.5 Boost Con v erter Output 23.9 Battery 12 In v erter Output (no-load) 228.8 (r .m.s.) 60 W - 250 W utility loads are supplied po wer by the de v eloped system. A personal desktop c o m puter acts as a 250 W critical load while assessing the emer genc y back-up po wer supply performance and its relia- bility for consumer usage. Figure 7 presents the output v oltage w a v eforms for 60 W and 100 W loads, whereas Figure 8 presents 132 W and 192 W load v oltages, respecti v ely . Figure 7. In v erter output v oltages for 60 W and 100 W loads respecti v ely Figure 8. In v erter output v oltages for 132 W and 192 W loads respecti v ely An elaborated performance inspection is carried out considering po wer f actor , v oltage and current har - monic distortions, output v oltage, back-up duration and po wer ef ficienc y yielding to load v ariations. T able 3 presents the o v erall performance e v aluation of the implement ed system for dif ferent loads. Here for a fluorescent and incandescent b ulb the maximum utility is considered to be its full brightness le v el to approx- imately 80 % of the full brightness le v el and f o r a f an is considered to be its full rated speed to 80 % of the full rated speed. The brightness le v el is estimate d roughly on the basis of a 25 - 30 year old vie wer’ s e yesight comfort le v el in night-time and the speed of a f an is determined using a speedometer . At the no-load condition the in v erter output v oltage (r .m.s.) is 228.8 V with an operating frequenc y of 50.2 Hz. T able 3 presents the changes in load v oltage v alues with respect to loads with dif ferent po wer ratings. The minimum utility load tested here is a 60 W incandescent b ulb and the maximum utility load tested here is a 250 W desktop computer . F or each load, instantaneous transfer switching (from mains po wer to in v erter po wer) feature is tested during of f-grid condition. The back-up po wer durations for dif ferent loads are considerable and after 10 minutes of back-up supply , in v erter input current and po wer ef ficienc y for each load are measured. From T able 3, it can be observ ed that the in v erter output v oltage THD v alues ( 18.3 %) do not change with load v ariations, whereas the load current THD v alues (minimum 17.8 % and maximum 19.1 %) change with load v ariations. From Figures 7 and 8, it is observ ed that the load v oltages are in the form of modified square w a v e of a fundamental frequenc y of approximately 50 Hz. From the changes in in v erter output v oltages during load v ariations, it can be concluded that the in v erter with loaded conditions w orks lik e a current source in v erter (CSI) and requires a feedback control loop to k eep t he output v oltage constant. F or a fix ed reference load current, a closed-loop control is essential that can be in continuous or discrete mode of operation; since no specific loop update time is required in the design. F or a po wer control implication, a multi-loop control happens to be required in which v oltage control is going to be the outer loop and current control is going to be the inner loop recei ving commands to track from the outer v oltage control loop. Ho we v er , these control prospects are in the future scope of this research design. The e xperimental sending-end po wer f actor of the proposed system is close to 0.9 with a mains l ine Implementation of a grid-tied emer g ency bac k-up power supply for ... (D. Chowdhury) Evaluation Warning : The document was created with Spire.PDF for Python.
6240 r ISSN: 2088-8708 current THD of around 25 %, which is considerably si gnificant in case of lo w line po wer loss. The system po wer ef ficienc y is subject to load v ariations. The maximum and minimum po wer ef ficiencies are close to 92 % and 75 %, respecti v ely . The observ ed back-up times for dif ferent loads underscore the reliabi lity of this system as an emer - genc y po wer supply especially in the re gions, which are victims to frequent po wer outage and poor v oltage re gulation. A computer is supported for a time period of 13 minutes, whereas lo w loads lik e 60 W and 100 W incandescent b ulbs are pro vided po wer back-ups for more than 1 hour durations. Thereby , it can be implied that the proposed system can be a potential solution to consumer UPS de vices. The cost ef fecti v eness is one of the most prominent features of the presented research w ork. The o v er - all cost estimation is enumerated in T able 4. It can be observ ed that the proposed system can be implemented incurring an e xpense belo w 30 $, which is significant in case of re gular and reasonable consumer applications. T able 3. Performance e v aluation of the DUT for dif ferent loads with sending-end po wer f actor P F s = 0 : 89 , mains current THD I mH = 25 : 3(%) , no-load in v erter v oltage V N L = 228 : 8 V (r .m.s.) and operating frequenc y f op = 50 : 2 H z Load T ype (Quantity) Load Po wer Rating (W) In v erter Out- put V oltage in Full Load State V L (V) Po wer Back- Up Duration for Maxi- mum Utility t b (Minutes) In v erter Input Port Current I inp (A) [mea- sured after 10 minutes of po wer back-up] Po wer Ef fi- cienc y p (%) [measured after 10 min- utes of po wer back-up] In v erter Output V oltage THD V LH (%) Load Cur - rent THD I LH (%) Incandescent Bulb (1) 60 208 86 4.9 91.8 18.3 17.8 Incandescent Bulb (1) 100 185 72 8.7 86.2 18.3 17.8 Incandescent Bulb (1) + Flu- orescent Bulb (1) 132 166 58 11.8 83.9 18.3 18.0 Incandescent Bulb (2) + Flu- orescent Bulb (1) 192 144 49 20.3 79.8 18.3 18.3 Ceiling F an (1) 120 171 53 10.7 84.1 18.3 18.5 CPU+Display unit (1) 250 127 13 29.9 74.6 18.3 19.1 T able 4. Cost allocation of the de v eloped prototype Subsystem Expendi ture ($) Battery 7.67 Char ger & its Controller 5.95 In v erter & its Controller 11.26 Relay & Switching Circuit 3.64 T otal 28.52 4. CONCLUSION Ef ficient and cost ef fecti v e po wer electronic switching con v erters based emer genc y back-up po wer supply systems are significant alternati v es to poorly re gulated and e xpensi v e grid po wer netw orks, especially in the re gions which f ace frequent grid po wer outages. In this article, design and practical considerations in re g ard to implementation of a grid-tied emer genc y utili ty back-up for medium and lo w po wer consumer usage are presented. A 4-switch push-pull in v erter circuit is de v eloped to support loads alternati v ely with the mains po wer line. Modified square w a v e v oltage signals are generated at the grid fundamental frequenc y by the back-up unit. The in v erter is sourced by an ener gy storage de vice (battery), which is char ged by a rectifier - fed PWM signal switched boost con v erter . A DPDT configured changeo v er relay mak es the instantaneous Int J Elec & Comp Eng, V ol. 10, No. 6, December 2020 : 6233 – 6243 Evaluation Warning : The document was created with Spire.PDF for Python.
Int J Elec & Comp Eng ISSN: 2088-8708 r 6241 transfer operation between the grid and the customized po wer supply system. Ov er -v oltage and o v er -heat protection schemes are pro vided for the battery through an SPDT rel ay switching circuit, which controls the char ging operation. Control units to generate switching PWM signals of respected frequencies are de v eloped in this w ork. A laboratory prototype is de v eloped to assess the performance for dif ferent loads. The p e rformance e v aluations and o v erall cost estimations corroborate the reliability and economic feasibility of the proposed design for potential consumer applicat ions. A more compact and high po wer sine w a v e generating po wer system with feedback control feature is a future scope of this w ork. REFERENCES [1] A. S. M. K. Hasan, D. Cho wdhury and M. Z. R. Khan, ”Scalable DC Microgrid Architecture with a One- W ay Communication Based Control Interf ace, ” 10th International Conference on Electrical and Computer Engineering (ICECE) , pp. 265-268, Dec 2018. [2] D. Cho wdhury , A. S. M. K. Hasan and M. Z. R. Khan, ”Scalable DC Microgrid Architecture with Phase Shifted Full Bri dge Con v erter Based Po wer Management Unit, ” 10th Internati o na l Conference on Electrical and Computer Engineering (ICECE) , pp. 22-25, Dec 2018. [3] A. S. M. K. Hasan, D. Cho wdhury and M. Z. R. Khan, ”Performance Analysis of a Scalable DC Microgrid Of fering Solar Po wer Based Ener gy Access and Ef ficient Control for Domestic Loads, ” arXi v:1801.00907 [eess.SP] , pp. 1-5, Jan 2018. [4] D. Cho wdhury , A. S. M. K. Hasan, M. Z. R. Khan, ”Islanded DC Microgrid Architecture with Dual Acti v e Bridge Con v e rter Based Po wer Management Units and T ime Slot Based Control Interf ace, ” IEEJ T ransactions on Electrical and Electronic Engineering , v ol. 15, no. 6, pp. 863-871, Jun 2020. [5] D. Cho wdhury , M. S. Miah and M. F . Hossain, ”Grid-Connected Emer genc y Back-Up Po wer Supply , ” Circuits and Systems , v ol. 10, pp. 1-19, Jan 2019. [6] Y -. H. Chang and J-. J. Liao, ”A No v el Coupled-Inductor Switched-Capacitor In v erter for High-Gain Boost DC-A C Con v ersion, ” The International MultiConference of Engineers and Computer Scientists , pp. 603-608, Mar 2016. [7] D. Cho wdhury , M. F . Hossain, M. S. Miah, M. M. Hossain, M. N. U. Sheikh, M. M. Rahman and M. M. Hasan, ”Design and Implementation of a Switching Con v erters Based Po wer System for Re gions V ictim to Frequent Po wer Outage, ” IEEE SoutheastCon , pp. 1-6, Apr 2018. [8] Y -. H. Chang and J-. S. Lin, ”A High-Gain Switched-Coupled-Inductor Switched-Capacitor Step-Up DC- DC Con v erter , ” The International MultiConference of Engineers and Computer Scientists , pp. 624-629, Mar 2016. [9] J. Choi and F . Kang, ”Se v en-Le v el PWM In v erter Emplo ying Series-Connected Capacitors P aralleled to a Single DC V oltage Source, ” IEEE T ransactions on Indust rial Electronics , v ol. 62, no. 6, pp. 3448-3459, Jun 2015. [10] C. P an, C. Lai and Y . Juan, ”Output Current Ripple-Free PWM In v erters, ” IEEE T ransactions on Circuits and Systems-II: Express Briefs , v ol. 57, pp. 823-827, Oct 2010. [11] M. Mezaroba, D. C. Martins and I. Barbi, ”A ZVS PWM Half-Bridge V oltage Source In v erter W ith Acti v e Clamping, ” IEEE T ransactions on Industrial Electronics , v ol. 54, pp. 2665-2672, Oct 2007. [12] C. M. Lia w , Y . M. Lin, C. H. W u and K. I. Hwu, ”Analysis, Design, and Implementation of a Random Frequenc y PWM In v erter , ” IEEE T ransactions on Po wer Electronics , v ol. 15, pp. 843-854, Sep 2000. [13] Y . Kim, S. Shin, J. Lee, Y . Jung and C. W on, ”Soft-Switching Current-Fed Push–Pull Con v erter for 250-W A C Module Applications, ” IEEE T ransactions on Po wer Electronics , v ol. 29, pp. 863-872, Feb 2014. [14] B. Reznik o v , M. Srndo vic, Y . L. F amiliant, G. Grandi and A. Ruderman, ”Simple T ime A v eraging Cur - rent Quality Ev aluation of a Single-Phase Multile v el PWM In v erter , ” IEEE T ransactions on Industrial Electronics , v ol. 63, pp. 3605-3615, Jun 2016. [15] R. Chauprade, ”In v erters for Uninterruptible Po wer Supplies, ” IEEE T ransactions on Industry Applica- tions , v ol. IA-13, pp. 281-297, Jul/Aug 1977. [16] Z. J. Zhou, X. Zhang, P . Xu and W . X. Shen, ”Single-Phase Uninterruptible Po wer Supply Based on Z-Source In v erter , ” IEEE T ransactions on Industrial Electronics , v ol. 55, pp. 2997-3004, Aug 2008. [17] Z. Rymarski and K. Bernacki, ”Dif ferent approaches to modelling single-phase v oltage source in v erters for uninterruptible po wer supply systems, ” IET Po wer Electronics , v ol. 9, pp. 1513-1520, Jun 2016. Implementation of a grid-tied emer g ency bac k-up power supply for ... (D. Chowdhury) Evaluation Warning : The document was created with Spire.PDF for Python.
6242 r ISSN: 2088-8708 [18] J. Chen and C. Chu, ”Combination V oltage-Controlled and Current-Controlled PWM In v erters for UPS P arallel Operation, ” IEEE T ransactions on Po wer Electronics , v ol. 10, pp. 547-558, Sep 1995. [19] K. Lo w and R. Cao, ”Model Predicti v e Control of P arallel-Connected In v erters for Uninterruptible Po wer Supplies, ” IEEE T ransactions on Industrial Electronics , v ol. 55, pp. 2884-2893, Aug 2008. [20] M. Shahparasti, A. Y azdian, M. Mohamadian, A. S. Larijani and A. F atemi, ”P arallel uninterruptible po wer supplies based on Z-source in v erters, ” IET Po wer Electronics , v ol. 5, pp. 1359-1366, Sep 2012. [21] H. K omurcugil, ”Impro v ed pass i vity-based control method and its rob ustness analysis for single-phase uninterruptible po wer supply in v erters”, IET Po wer Electronics , v ol. 8, pp. 1558-1570, Jul 2015. [22] H. Deng, R. Orug anti and D. Srini v asan, ”A Simple Control Method for High-Performance UPS In v erters Through Out put-Impedance Reduction, ” IEEE T ransactions on Industrial Electronics , v ol. 55, pp. 888- 898, Feb 2008. [23] F . Botter ´ on, R. E. Carballo, R. O. N ´ u ˜ nez, A. P . Quintana and G. A. Fern ´ andez, ”High Reliability and Performance PWM In v erter for Standalone Microgrids, ” IEEE Latin Amer ica T ransactions , v ol. 11, pp. 505-511, Feb 2013. [24] M. Shahparasti, A. Y azdian, M. Mohamadian, A. S. Larijani and A. F atemi, ”P arallel uninterruptible po wer supplies based on Z-source in v erters, ” IET Po wer Electronics , v ol. 5, pp. 1359-1366, Sep 2012. [25] K. Bernacki and Z. Rymarski, ”Electromagnetic compatibility of v oltage source in v erters for uninterrupt- ible po wer supply system depending on the pulse-width modul ation scheme, ” IET Po wer Electronics , v ol. 8, pp. 1026-1034, Jun 2015. [26] X. Li., Z. Deng, Z. Chen and Q. Fei, ”Analysis and Simplification of Three-Dimensional Space V ector PWM for Three-Phase F our -Le g In v erters, ” IEEE T ransactions on Industrial Electronics , v ol. 58, pp. 450-464, Feb 2011. [27] S. Das, K. M. Salim and D. Cho wdhury , ”A no v el v ariable width PWM switching based b uck con v erter to control po wer f actor correction phenomenon for an ef ficacious grid inte grated electric v ehicle battery char ger , ” TENCON 2017 - 2017 IEEE Re gion 10 Conference , pp. 1-6, No v 2017. [28] D. Cho wdhury , M. I. Hussain, M. G. Zakaria, M. Z. R. Khan and M. Z. Haider , ”An Electrically Isolated Lo w Po wer LED Dri v er Of fering Po wer F actor Correction with Ameliorated Mains Current THD, ” 8th IEEE India International Conference on Po wer Electronics (IICPE) , pp. 1-6, Dec 2018. [29] D. Cho wdhury , M. I. Hussain, M. G. Zakaria, and M. Z. R. Khan, ”A Lo w Po wer LED Dri v er with a Soft-Switched Buck Con v erter and a P arallel-Loaded Series L-C Res onant In v erter , ” 10th International Conference on Electrical and Computer Engineering (ICECE) , pp. 26-29, Dec 2018. [30] S. Das, K. M. Sali m, D. Cho wdhury and M. M. Hasan, ”In v erse sinusoidal pulse width modulation switched electric v ehicles’ battery char ger , ” International Journal of El ectrical and Computer Engineering (IJECE) , v ol. 9, pp. 3344-3358, 2019. [31] ON Semiconductor , ”SG3525A Pulse W idth Modulator Control Circuit, ” Jan 2005. [Online]. A v ailable: https://www .onsemi.com/pub/Collateral/SG3525A-D.PDF BIOGRAPHIES OF A UTHORS Dhiman Cho wdhury is a PhD student and graduate research assistant at Uni v ersity of South Car - olina. He obtained Bachelor of Science (B.Sc.) de gree in Electrical and Electronic Engineering in 2016 from Bangladesh Uni v ersity of Engineering and T echnology , Dhaka, Bangladesh. He w ork ed as a f aculty member (research and academic) in Daf fodil International Uni v ersity , Dhaka, Bangladesh in 2016-2017. His researc hes are in fields of po wer electronics, rene w able ener gy , microgrids, signal processing and control systems. Currently , he is w orking on FPGA based real-time models de v elop- ment of po wer electronic con v erters with associated control system interf ace. He is af filiated with IEEE as a student member a nd IAENG as a me mber . He is a re vie wer of se v eral journals lik e IEEE Systems, IET Po wer Electronics, Ener gies, Sensors, Sustainabilit y , Processes and Applied Sciences (MDPI), Applied Ener gy and Electric Po wer Systems Research (Else vier), IEEE Po wer and T echnol- ogy Systems Journal, International Journal of Modelling and Simulation and Electric Po wer Compo- nents and Systems Journal (T aylor & Francis) and Circuits and Systems (SCRIP). He has published se v eral journal articles and conference proceedings. Int J Elec & Comp Eng, V ol. 10, No. 6, December 2020 : 6233 – 6243 Evaluation Warning : The document was created with Spire.PDF for Python.