DSP-Based Control for Parallelism of Three-Phase Voltage Source Inverter Telles B. Lazzarin, Member, IEEE, and Ivo Barbi, Fellow, IEEE Power Electronics Institute (INEP), Department of the Electrical Engineering (EEL), Federal University of Santa Catarina (UFSC), Florianópolis , Brazil

Abstract—This paper describes a theoretical and experimental study on a control strategy for the parallel operation of three-phase voltage source inverters (VSI), to be applied to UPS. The proposed control system for each inverter consists of two main loops, which both use instantaneous values. The first (parallelism control) employs the feedback of the inductor currents from the output filter to modify the input voltages of the same filter and thereby control the power flow of each VSI to the load. Additionally, the second loop (voltage control) is responsible for controlling the output voltages of the LC filter, which coincides with the output voltages of the VSI. The proposed control strategy ensures the proper sharing of the load current and avoids current circulation among the inverters during transient and steady-state operation. The VSI and the proposed control strategy are analyzed in an orthogonal stationary frame, and as a result, simple and effective models were achieved. The proposed control system was digitally implemented in a TMS320F2812 DSP and was verified through experimental results with a 10 kVA prototype, which has the parallel operation of two three-phase VSIs.

II. INTRODUCTION
 ININTERRUPTIBLE power supply (UPS) devices are employed to feed critical loads which, at high power values, utilize a three-phase system. Moreover, inmany applications the total load consists of a set of single and three-phase loads, which requires the employment of three-phase UPS, capable of feeding all types of load. In addition, critical loads also require a power supplywith high-reliability and redundancy that can be obtained with the parallel-connection ofUPSs.As iswell-known, the parallelism of UPS is a problem related to the parallel operation of voltage source inverters (VSIs). The parallel operation of three-phase VSIs has a greater complication due to the complexity and the greater number of variables involved in a three-phase system. Recent publications in the literature [1]–[3] broach this problem and they point out that there is still a need for new solutions to the parallelism of three-phase VSIs. It is also well-known that the parallel operation of VSIs requires a control system to ensure proper operation of the structure. A traditional solution is the strategy based on the frequency and voltage droop [4]–[18]. This strategy controls the average active and reactive power flow from the VSI to the load and it does not require communication among the inverters. It provides increased reliability and redundancy but it has errors associated with load sharing, poor transient response, reduced voltage regulation and it does not control the division of the harmonic currents [1], [3]. In the literature there are interesting studies reported [8], [9], [11], [18]–[22] which minimize the disadvantages, in most cases addressing single-phase systems. On the other hand, there are strategies related to communication, such as central control [23]–[25], master-slave control [26]–[29] and distributed control [2], [3], [30], [25]. These strategies are most effective in terms of load sharing, but high reliability and redundancy are not available due to the communication between units. In recent years, these strategies have been based on the instantaneous current control [2], [3], [24], [34], [35], in which the parallelism control receives information on the instantaneous current supplied by all units. Good transient response and the appropriate load sharing among VSIs, including the harmonics of load current, are advantages introduced by instantaneous control. The evolution of these strategies is associated with the use of microcontrollers, DSP and FPGA in power converters [36]–[44]. The digital control provides the means to propose new solutions to complex problems as in the parallel operation of three-phase voltage inverters. In this context, this paper proposes a distributed control strategy for the parallel operation of three-phase VSIs. Each VSI has its own control unit, responsible for regulating the output voltages and ensuring its parallel operation.

A Novel Circuit Configuration of UPS with Auxiliary Inverter and Its Specific Control Implementations Katsuya Hirachi and Mutsuo Nakaoka

A Novel Circuit Configuration of UPS with Auxiliary Inverter and Its Specific Control Implementations
Katsuya Hirachi and Mutsuo Nakaoka
RESEARCH AND DEVELOPMENT DIVISION POWER SUPPLY  COMPANY,YUASA,OSAKA JAPAN.
DEPT. OF ELECTRICAL AND ELECTRONICS ENGINEERING  YAMAGUCHI UNIVERSITY
YAMAGUCHI JAPAN

Abstract
 The rapid expansion of small computers over the last 10-odd years has brought about great changes in the circumstances affecting UPSs. There are strong demands that UPSs become much smaller and lighter, and more economical, which has resulted in the wide application of the circuit topology without transformer. A disadvantage of such UPS topology is that the DC link voltage is very high, which invites decreased reliability and increased cost of battery bank. Some circuit configurations were proposed to eliminate this disadvantage, but they still had problems. In this paper, a novel circuit configuration which eliminates these problems is proposed and evaluated by the experimental results of prototype UPS.
LINK
http://jpe.or.kr/archives/view_articles.asp?seq=79
LINK DIRECT
http://manuscript.jpe.or.kr/ltkPSWeb/pub/pubfpfile.aspx?ppseq=79

Design of Robust Controller for Single-Phase Double-Conversion UPS System Seung-Beom Lim, Young-Min Seol, Sang-Hoon Kim, Jin-Woo Lee, and Soon-Chan Hong Dankook University, Korea, Kangwon National University, Korea

Design of Robust Controller for Single-Phase
Double-Conversion UPS System

Seung-Beom Liml, Young-Min Seo, Sang-Hoon Kim, Jin-Woo Lee, and Soon-Chan Hongl
 Dankook University, Korea,  Kangwon National University, Korea, Doowon Technical College,
Koreabus1327@hotmail.com, maniyan@nate.com, kshoon@kangwon.ac.kr, jinwoo@doowon.ac.kr, schong@dku.edu

Abstract-UPS is largely divided into passive-standby, line interactive,
and double-conversion types. In general, a double conversion
type is used at a site requiring a high reliability. The
main function of the double-conversion UPS is providing the
constant voltage, constant frequency, regardless of the linear or
non-linear load and variation of the load. In this paper, the
robust controller of the single phase double-conversion UPS is
designed and its performance is verified by both simulations and
experimentation.

RESUMO DA NORMA IEC 62040 FOR UPS

As normas IEC 62040 são normas internacionais que definem as características e
especificações de UPS. Estas normas abordam os seguintes assuntos:

IEC 62040-1-1. Uninterruptible power systems (UPS) Part 1-1: General and safety
requirements for UPS used in operator access areas (IEC 62040-1-1, 1999).

IEC 62040-1-2. Uninterruptible power systems (UPS) - Part 1-2: General and safety
requirements for UPS used in restricted access locations (IEC 62040-1-2, 1999).

IEC 62040-2. Uninterruptible power systems (UPS) - Part 2: Electromagnetic compatibility
(EMC) requirements (IEC 62040-2, 1999).

IEC 62040-3. Uninterruptible power systems (UPS) - Part 3: Method of specifying the
performance and test requirements (IEC 62040-3, 1999).

RESUMO DA NORMA IEC 62040
http://www.mediafire.com/?ug4ddj5eyva8om0

GE Zenith ATS Seismic compliance video 2009_mpeg4_mp3.avi

SOCOMEC UPS

RIELLO Inside our ups's manufacturing

Caratteristiche_principali_dell'UPS_Trinergy.wmv

Durante il convegno E3-DAY del 16 febbraio 2010 Chloride illustra le caratteristiche distintive di Trinergy: UPS modulare di alta potenza (a partire da 200 kVA), con efficienza fino al 99% e scalabilità fino a 9,6-12,8 MW.

Enterprise-Scale UPS Protection for Medium and Large Data Centers -EmersonNetworkPower

Analysis of Parallel Operation of Uninterruptible Power Supply

Analysis of Parallel Operation of Uninterruptible
Power Supplies Loaded through Long Wiring
Cables
L. Corradini P. Mattavelli M. Corradin, F. Polo
ECEE Department
University of Colorado at Boulder
DTG
University of Padova
Socomec Sicon UPS Italia
1111 Engineering Drive
Boulder, CO 80309
Stradella S. Nicola 3,
36100 Vicenza – Italy
Via Sila 1/3
36033 Vicenza – Italy
luca.corradini@colorado.edu mattavelli@ieee.org {michele.corradin,
filippo.polo}@socomec.com

AFFIDABILITA’ E QUALITA’ DEL SERVIZIO ELETTRICO PER UTENTI

POLITECNICO DE TORINO-Ingegneria Elettrica-
relatore: Prof. Roberto Napoli
Negli ultimi anni l’Italia è stata caratterizzata da un incremento dei consumi di
energia elettrica sia nel settore industriale che nel settore terziario, inoltre si è
riscontrato, grazie allo sviluppo tecnologico, un aumento sostanziale degli
utilizzatori che fruttano componenti elettronici molto sensibili, come vedremo, ai
disturbi della rete in grado di provocare mal funzionamenti o addirittura la rottura
di tali componenti.
Un altro cambiamento radicale che ha sconvolto il panorama elettrico per quanto
riguarda la produzione e la vendita di energia elettrica, è stato la liberalizzazione
del mercato che ha portato all’introduzione di soggetti terzi come distributori di
energia ,a differenza di quanto capitava in passato, dove questo mercato era
gestito interamente da ENEL.
Queste condizioni, cioè una maggiore qualità del servizio e la comparsa di tanti
piccoli distributori, ha evidenziato la necessità di avere delle linee guida da
seguire per regolare i rapporti tra le varie parti; tale necessità è stata recepita sia da
A.E.E.G. che ha emanato le proprie regole in campo legislativo, sia dal CEI che
ha stabilito le regole tecniche per uniformare tutte quelle regole che erano state
emanate da ogni singolo distributore.
In questo elaborato faremo inizialmente una panoramica sulle principali cause che
inficiano la qualità dell’alimentazione, per poi passare ad una analisi dei principali
aspetti delle leggi e delle regole tecniche vigenti, evidenziando alcuni problemi e
proponendo alcune soluzioni non prese in considerazione da queste.

Leggi l'articolo completo

Comparing Transformer-based and Transformerless Uninterruptible Power Supplies

Robin Koffler is the General Manager for Riello UPS Ltd the UK subsidiary of Riello UPS (RPS S.p.A)

Choosing between transformer-based or transformerless uninterruptible power supplies may not be a simple ‘either/or’ decision, particularly above 10kVA. Both technologies have their place in today’s power protection scenarios but the key differences between them are: physical size, efficiency, noise output and the levels of input harmonic distortion that they generate.
Both uninterruptible power supply designs produce a tightly regulated source of uninterrupted power but they differ in the way they generate the dc voltage required by their inverters and their output stages.
Transformer-based Uninterruptible Power Supplies: until the early 1990s, the only design of online uninterruptible power supply was transformer-based. Nowadays, the design is still available but generally in larger sizes for UPS from eight to 800kVA. The most common applications for this are large industrial sites.
This type of UPS has a robust transformer-isolated inverter output, which makes it more suitable for the type of application where there is a likelihood of electrical noise; spikes, transients, and potentially, a high degree of short-circuit currents.
The inverter generates an ac supply from its dc power source, which is fed into a step-up transformer. The primary function of the transformer is to increase the inverter ac voltage to that required by the load. The transformer also protects the inverter from load disruption, whilst also providing Galvanic isolation (a method of isolating input and output).
Modern inverter designs use IGBTs (Insulated Gate Bipolar Transistors) in place of more traditional switching components (such as power transistors and thyristors). IGBTs combine the fast-acting and high power capability of the Bipolar Transistor with the voltage control features of a MOSFET gate to form a versatile, high frequency switching device. This in turn has given rise to more powerful, efficient and reliable inverters.
Transformer-based UPS are also supplied with a dual input option as standard, which can be selected at installation by simply removing a linking connector from its input terminal. This allows it to be powered from two separate ac supply sources thus adding further resilience. A transformerless UPS can be installed with dual input capability, with supplies derived from the same source, but this is typically a factory-fit option.
Transformerless Uninterruptible Power Systems
Transformerless UPS is a newer design, commonly available from 700VA to 120kVA. The primary purpose behind the introduction of transformerless units was to reduce the overall physical size and weight thus making an uninterruptible power supply unit more suitable for smaller installations and/or computer room/office type environments, where space may be limited. It also generates far less noise and heat than its transformer-based cousin and has far lower input harmonic distortion levels making it compatible with environments where electronic equipment (such as computers) may be more sensitive to this type of distortion.
In place of the step-up transformer, a transformerless UPS uses a staged process of voltage conversion. The first stage combines a rectifier and booster-converter to generate a dc supply for the inverter. An uncontrolled, three-phase bridge rectifier converts the ac supply into a dc voltage. This is passed through a mid-point booster circuit to step the dc voltage up to typically 700-800Vdc from which a battery charger and inverter are powered. In the second stage, the inverter takes the supply from the booster-converter and inverts it back to an ac voltage to supply the load.
An added benefit of this method is that the rectifier can operate from either a three or single-phase input supply. This can be configured at installation for systems up to 20kVA. A control system ensures a stable, regulated dc voltage is supplied to the inverter at all times and the inverter can operate regardless of UPS output load variations or mains power supply fluctuations or disturbances.
Choosing between Transformer-based or Transformerless Uninterruptible Power Supplies
In many applications the choice between the two may be clear. It is where the two ranges overlap, in terms of power rating, that the decision is more complicated. Consideration needs to be given then to: initial purchase cost, physical size, running costs, the installation environment, and in particular, the levels of input harmonic distortion they generate. Both designs can be operated in parallel to achieve higher levels of availability and resilience.
Over the last decade, the gap between these two uninterruptible power supply technologies has reduced as manufacturers have applied common techniques and research & development efforts to both designs. The driving force behind this has been cost and size, alongside demands to improve operating efficiency and reduce harmonic generation. In terms of online performance, both designs provide the same level of performance and are classified as VFI systems (voltage and frequency independent - in accordance with EN/IEC 62040-3). Their principal differences are their effects on upstream supplies and the operating environment.
Transformerless UPS are generally recognised as more efficient and having a higher power factor than an equivalent transformer-based design, therefore operating costs can be lower.
Below 10kVA, the transformerless UPS design dominates the online uninterruptible power supply market and has become the standard within data centre environments as they offer a more compact footprint, higher operating efficiencies and lower noise output. However, the strengths of the transformer-based design come into play in the industrial environment.

EXCELENTE ARTIGO DO ENG. ROBIN KOFFLER,ELE E REALMENTE VALIDO NOS MERCADOS EUROPEUS,NORTEAMERICANO,ASIATICO,MAIS NO MERCADO ESPECIFICAMENTE BRASILEIRO ,TERIA QUE TOMAR EM CONTA NOSSA REALIDADE ESPECIFICA,ISTO E,BRASIL E O CAMPEAO MUNDIAL DOS RAIOS,AS DESCARGAS ATMOSFERICAS NAS REGIONES SUDESTE E MAIOR PARTE DO TERRITORIO,SAO DE NATURALEZA INTENSA QUE OS UPS COM TRANSFORMADOR TEM MAIOR VIDA UTIL E ROBUSTEZ QUE OS QUE SAO PROJETADOS SEM TRANSFORMADOR,NESTE CASO OS CIRCUITOS SUPPRESSORES DE SURTOS E DESCARGAS ATMOSFERICAS TRABALHARAM A SUA MAXIMA CAPACIDADE,POR ISSO TEM QUE SER BEM ANALIZADO A ESCOLHA MAS CERTA PARA CADA NECESSIDADE.

SEMINARIO BASICO DE UPS

SEMINARIO SOBRE UPS , TENDENCIAS TECNOLOGICAS Y COMERCIALES.