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AES 2007 , THE VISION REDRAWN LONDON, 25-26 Sept. 2007

AES 2007 , THE VISION REDRAWN LONDON, 25-26 Sept. 2007. Investigation of voltage/frequency modulation in ship electric networks with pulsed loads , according to STANAG 1008 design constraints. F. Kanellos , PhD , Hellenic Transmission System Operator

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AES 2007 , THE VISION REDRAWN LONDON, 25-26 Sept. 2007

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  1. AES 2007,THE VISION REDRAWN LONDON, 25-26 Sept. 2007 Investigation of voltage/frequency modulation in ship electric networks withpulsed loads,according to STANAG 1008design constraints F. Kanellos ,PhD ,Hellenic Transmission System Operator I.K. Hatzilau ,Prof. Dr.-Ing.,Hellenic Naval Academy J. Prousalidis ,Ass. Prof., National Technical University of Athens 1

  2. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis What is the Scope of the Paper ? * STANAG 1008 , isthe NATO naval standard entitled “ Characteristics of Shipboard Electrical Power Systems in Warships of the North Atlantic Treaty Navies ” and dealing with Power Supply Quality ( P.S.Q. ) issues. - NATO AC/141(MCG/6)SubGroup/4) has the responsibility for STANAG 1008 - The last Edition, Ed. 9, was promulgated at 2004. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 2

  3. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis What is the Scope of the Paper ? Up-to-date, there is no NATO standard for the AES electrical power system (HV, electrical propulsion) * Although STANAG 1008does not directly apply to AES, but only to Low Voltage ship-service system of a “conventional” electrical network, the authors consider that it may be used as a discussion reference for standards applicable to LV sub-networks of AES. Even in AES there will be LV service system, with equipment of more or less similar operating constraints concerning voltage and frequency modulation, as stipulated by STANAG 1008. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 3

  4. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis What is the Scope of the Paper ? * In this paper, an effort is made to examine and validate or not the STANAG 1008 design constraints, via simulations in Matlab/Simulink, taking into account certain parameters which affect the entire phenomenon of “Voltage and Frequency modulation” caused by “Pulsed Loads”. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 4

  5. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis CONTENTS … the paper arrangement is the following : 1. INTRODUCTION and BACKGROUND 2. Model and Simulation Results for the CONVENTIONAL ELECTRICAL SYSTEM 3. Model and Simulation Results for the A.E.S. ELECTRICAL SYSTEM 4. DISCUSSION and CONCLUSIONS 5. Acknowledgements 6. References 7. Bibliography AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 5

  6. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND * “Modulation” is defined as the “ voltage and frequency periodic or quasi-periodic variations, such as might be caused by regularly or randomly repeated loading with frequency less than nominal ”. * VoltageandFrequency Modulation may affect the operation of several subsystems of the ship such as radarscopes, communication equipment, missile guidance systems, weapons, gear systems etc … AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 6

  7. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND • * Electric loads causing “modulation” • are loads which require high power(from kWs to GWs) • for a very short time interval (from msec to seconds) • and are known as “Pulsed Loads”. • Representative examples of Pulsed Loads are • - controlled heaters • - sonars • - radars • (EMALS) Electromagnetic • Aircraft Launch Systems • Electromagnetic Guns • (such as Rail Guns, • Coil Guns, Lasers, • High Energy Microwaves) • etc … Railgun concept Coilgun concept AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 7

  8. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND Pulsed loads of rather low peak absorbed power are usually directly connected to the electric power grid, while the ones of larger peak absorbedpower are usually coupled to the network via the intervention of Energy Storage Devices andPulsed Forming Networks (PFN). In this latter case, the power system does not interact with the pulsed load itself, but “sees” only the behavior of the intermediate power conditioning system. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 8

  9. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis Diode Rectifier CB L-C-L Filter C CB Pulsed Load 4160 V AC Firing Command Capacitor charging and Pulsed Load firingControl System 1. INTRODUCTION and BACKGROUND Usually, the typical power time-profile of a Pulsed Load is the“rectangular” one, but in the case, that an intermediate system is used – e.g. a diode rectifier supplying the load through a capacitor– the load, which the ship power system actually“sees”, has an “impulse” power time-profile. “impulse” power profile Ppulse= exp[-t/(T1)] - exp[-t/(T2)] power “rectangular” power profile time (sec) power L-C-L Filter time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 9

  10. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND * DEFINITIONS, LIMITSandDESIGN CONSTRAINTS ofSTANAG 1008 Schematic representation of Voltage and Frequency Modulation, caused by a Pulsed Load AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 10

  11. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND In STANAG 1008 Voltage or Frequency Modulation are quantified, by using the difference between the Maximum and Minimum values as a percentage of the double of their Nominal Values, as shown in Equation (1) : (1) In this formula all voltages are to be in rms , or peak or mean values. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 11

  12. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND * According to STANAG 1008 the modulation limits are .. 2% for the Voltage and 0.5% for the Frequency AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 12

  13. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND According to design constraints of STANAG 1008 ( Edition 9, ANNEX B “User Information and Constraints “, para. 9.d ), in order voltage/frequency modulation not to exceed the above-mentioned limits, reactive and active power of the pulsed load are limited by these inequalities : (2) Qpulse< 6.5% of SsupplyandPpulse < 25 % of Ssupply where : Qpulse, is the reactive andPpulse the active power of the Pulsed Load, while Ssupply,is the full rated apparent power of the Supply at the time of occurrence of the pulse. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 13

  14. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND After some simple mathematics, the STANAG 1008 inequalities (2) are equivalent , to the LIMITSfor pulsed load operation shown in the following inequalities (2.a) : P.F.*x < 0.25 and P.F. > [ 1 – (0.065/x)2 ] 1/2 (2.a) where : P.F. is the Power Factorand Spulse is the Apparent Power of the Pulsed Load , while xis the Pulsed Load apparent power relativeto thefull rated apparent power of the Supply. P.F. = Ppulse / Spulse Spulse = ( Ppulse 2 + Qpulse2)½ x=Spulse /Ssupply AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 14

  15. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND The graphical representation of inequalities(2.a), with pulsed load relative apparent power xexpressed in percentage[S%] gives thepulsed load limit-curves,here-in-after :P.F.(S%) curves. P.F.(S%) limit-curves P.F. P.F.*x < 0.25pulsed load active power limit-curve x=Spulse /Ssupply P.F. > [ 1 – (0.065/x)2 ] 1/2 pulsed load reactive power limit-curve , x in percentage = S%. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 15

  16. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND In these diagrams we see, left the graphic of inequalities (2.a) and right the corresponding pulsed load limit-curve P.F.(S%) of STANAG 1008design constraints, which define the “acceptable” and “unacceptable”range of pulsed load operation. acceptable range unacceptable range STANAG 1008 limit-curve AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 16

  17. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND • * This STANAG 1008 guidelineseems to lead,to a rather • rough estimation of pulsed loads limits, as it deals withonly • the relative apparent power (x or S%) and the power factor(P.F.) • of the pulsed load, but it does not take into account • certain additional parameters affecting the entire phenomenon • such as : • periodicity of modulation • (pulse repetition frequency) • duty cycle of the pulsed load • profile of the pulsed load • point of connection of the • pulsed load onto the el. grid • system impedance • characteristics of the generators • and their associated frequency and voltage controllers • loading of the generator at the time of pulsed load occurrence • etc STANAG 1008 limit-curve AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 17

  18. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND So, in this paper we investigate, via simulations in Matlab/Simulink, the influence, of most of the parameters mentioned before, on the Voltage and Frequency modulation, in order to examine and validate or not the STANAG 1008, Ed.9 design constraints. STANAG 1008 limit-curve * By varying of some Pulsed Load and Network parameters, the resulting P.F.(S%) limit-curveswere estimated andcompared to the respective one of STANAG 1008. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 18

  19. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 1. INTRODUCTION and BACKGROUND Concerning the topology of the ship electric network, two main configurations are considered : - first, a LV “conventional” system ( without electrical propulsion part) and - second an AES configuration, where the Voltage and Frequency modulation at the LV-subsystem is investigated. STANAG 1008 limit-curve * Finally, in the paper, general conclusions are derived, as well as a proposition for generalization of the STANAG 1008 P.F.(S%) limit-curve. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 19

  20. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2. CONVENTIONAL SHIPBOARD EL. SYSTEM 2.aModel of Ship Electric Network In this case study we consider a “conventional” configuration for the network with only LV part, and without electric propulsion , as it is shown in the next slides. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 20

  21. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) Model of network used for a “conventional” ship. MP : “Measuring” point, where Voltage modulation is estimated. The generating set is aggregated in a Pm = 2 MVA, 440V, 60Hz synchronous generator, driven by diesel engine. Gen. Parameters ra0.0036 Xd1.56 X'd0.296 X''d0.177 Xq1.06 X''q0.177 Xl0.052 T'do3.7 sec T''do0.05 sec T''qo0.05 sec H 1.07 sec F 0.1 50m 100m Pulsed Load AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 21

  22. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) GOVERNORblock diagram Pm: mechanical power ωref: Reference speed ωm: measured speed Kf 40 [T1, T2, T3] [0.01, 0.02, 0.2] [T4, T5, T6] [0.25, 0.009, 0.0384] [Tmin, Tmax) [0.1, 1] Td( Engine time delay ) 0.024 Pm0 0.5 Values of Governor-parameters AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 22

  23. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) AVR IEEE type 1 block diagram Vref: Voltage reference EFD: Field voltage reference Vs: stabilization voltage signal EC: measured voltage Values of AVR-Parameters LPF time constant Tr(s) ……….….[ 20e-3 ] Regulator gain and time constant [Kfr , Tfr(s)] …[ 200, 0.001 ] Exciter [Ke , Te(s)] ………. [ 1, 0 ] Transient gain reduction [Tb(s) , TC(s)] …. [ 0, 0] Damp filter gain and time constant [Kfd , Tf(s)] … [ 0.001, 0.1 ] Field saturation parameters [A, B] ……. [ 0, 0 ] Regulator output limits [VRmin, VRmax(p.u.), KC ] [ -11.5, 11.5, 0 ] AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 23

  24. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) For no load – full load operation and vice versa, we see here … … the Generator active power(p.u) … and the - at Generator and at - Pulsed load bus Within about 1.5 sec AVR stabilizes the Voltage at generator terminal. Voltage variation Generator terminal Voltage [V] Pulsed Load bus Time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 24

  25. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) … while here,we see the corresponding Frequency variation . System frequency recovers 3 sec after full load application. Frequency [Hz] Time (sec) Generator active power (p.u) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 25

  26. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) System response for a repetitive pulsed load * Generator loading is 48% * Pulsed Load : rectangular-profile 0.3sec period, 50% duty cycle P.F.= 0.8 inductive, and relative apparent powerS=15% of generator nominal apparent power RMS voltage at service load bus Time (sec) Generator active power System frequency Time (sec) Time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 26

  27. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.aModel of Ship Electric Network (conventional) It is noticeable, that immediately after a repetitive pulsed load application, a sub-transientphenomenon occurs , which should be included in voltage and frequency modulation estimation. Voltage [V] ΔV ’ > ΔV Time (sec) Frequency [Hz] Δf ’ > Δf AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 27

  28. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) In order to estimate the pulsed load operation limit-curves P.F.(S%), the electrical network is simulated for several Pulsed Load and Network parameters with a rectangular profile pulsed load connected on the 440 V side. For each parameter set, the pair of values of P.F and S% is sought iteratively, so that neither voltage nor frequency modulation exceed the 2% and 0.5% limits respectively, while at least one of them is very close to these limits. The parameters investigated and their respectivevalue ranges are summarized in the following : AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 28

  29. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) For the simulation of the assumed operating scenarios, thebasic model parameters values used,are shown on this table * Generally, in most of the following scenarios only one basic parameter is changed and the rest are maintained constant, examining in this way the extent, that the specified parameter affects the results. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 29

  30. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) In this table the Parametersdeviation ranges investigatedare shown. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 30

  31. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) The algorithm of defining the P.F.(S%) limit-curve is based on a trial and error approach: several simulations are run up to when the limit is met. For each parameter set and each S% value, the corresponding value of P.F. is sought. STANAG 1008 limit-curve For example, in this figure, in the case of S=11% pulsed load apparent power, starting from point 1, after some iterative simulations we result in point 4, where Voltage Modulation is 1.99% and Frequency modulation is 0.05%. Point 4 belongs to the limit-curve we are looking for. Calculated limit-curve - - - - - - - AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 31

  32. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) In the following representative results regarding the influence of some parameters on pulsed load operation limit-curve P.F.(S%) are shown. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 32

  33. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) Influence ofGenerator Sub-transient ReactanceX’’on P.F.(S%) limit-curves Fig. 8 STANAG limit In this diagram, we see the influence of the generatorsub-transient reactanceX’’-varying between 11% and 20% - on the P.F.(S%) limit-curve. 20% 11% AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 33

  34. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) Influence of 440V “Cable Lengths” on P.F.(S%) limit-curves Fig. 10 The variation of the 440 V Cable Lengths between 50m and 500m affects significantly the unacceptable operating area. STANAG limit 500m 50m * 0.15+0.35j (ohm/km) * generator loading 10%, *pulsed load : period 0.4sec, duty cycle 60% AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 34

  35. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) Influence ofPulsed Load “Period” T on P.F.(S%) limit-curves Fig. 11 The variation of the Pulsed Load Period between 0.02 and 1.6 sec has also a significant effect on the limit-curve. The higher the pulsed load period is, the bigger the unacceptable operating area. STANAG limit 0.3sec 0.15sec 0.05sec AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 35

  36. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) Influence ofPulsed Load “Duty Cycle” on P.F.(S%) limit-curves Fig. 12 The variation of the Pulsed Load Duty Cycle between 15 and 90% of the 0.3sec period affects considerably the limit-curve. The higher the Duty Cycle is, the bigger the unacceptable operating area. STANAG limit 70% 30% 15% AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 36

  37. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) Some further simulation results are summarized in the following. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 37

  38. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) Fig. 14 Df % versus DV % relation. Total statistic of all the cases studied In all examined scenarios : Voltage modulation limit is exceeded more times than Frequency limit, leading to the conclusion that Voltage limit is tighter than the Frequency limit. Additionally, almost never both limits are exceeded. Frequency modulation Voltage modulation AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 38

  39. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) DV% at several buses Generator bus Voltage modulation vs 440 V bus Voltage modulation Fig. 15b In all examined scenarios : Voltage modulation at Generator bus and at 115 V bus are always smaller, than that of the 440 V service load bus. Therefore, studying modulation of 440 V, leads to safe results for the entire system. 115V bus Voltage modulation vs 440 V bus Voltage modulation Fig. 15a AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 39

  40. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 2.b Simulation Results (conventional Network) The extent, that the Voltage modulation limit affects the limit-curves, is investigated, too. Voltage modulation limits from 1.5 to 2.5 (%) are considered. The P.F.(S%) curves are displaced almost symmetrically around the 2% limit-curve, for different Voltage modulation limits. STANAG limit *generator loading 15%, * 440 V cable length 250m, * pulsed load : period 0.6sec, duty cycle 50% Fig. 16 AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 40

  41. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION In this case, the electric network of a warship in the context of AES, with a pulsed load installed, is simulated. * The generating set is aggregated in a 35 MVA, synchronous Generator operating at 4.16 kV, driven by diesel engine. * The main HV load is a Propulsion Induction Motor, assumed, to operate at constant power mode during the simulation. * Ship service loads are fed through HV/LV transformers. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 41

  42. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION The generating set is aggregated in a Pm = 35 MVA, 4.16 kV, 60Hz synchronous generator, driven by diesel engine Model of network used for an “AES”. MP : “Measuring” point, where Voltage modulation is estimated. Gen. Parameters ra0.00285 Xd1.305 X'd0.296 X''d0.232 Xq0.475 X''q0.243 Xl0.18 T'do1.9 sec T''do0.05 sec T''qo0.1 sec H 2.1 sec F 0.08 100m 250m 50m Pulsed Load AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 42

  43. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION(Results) Within the framework of this paper, some preliminary results in the simplified AES configuration are presented next. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 43

  44. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION(Results) *First, the effect of Pulsed Load installation point , on P.F.(S%) limit-curve at 440 V bus , is examined, by assuming a rectangular Pulsed load installed in 440 V pulsed load installed, either at 440 Vor at 4.16 kV supply system. STANAG limit …the result is, that the operating unacceptable area is increased, if the pulsed load is installed at 440 V bus. *rectangular pulsed load 0.6 sec period, 50% duty cycle * generator loading 53% Pulsed load installed in 4.16 kV Fig. 19 AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 44

  45. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis Rectifier CB Filter C CB Pulsed Load 4.16 kV AC Control 3. AES CONFIGURATION(Results) *Next, we examine the effect of pulsed load profile, installed at 4.16 kV supply on the variation … - ofsystem frequency - and ofvoltage at different points of the network. Two different pulsed load profiles, with the same peak value (15% p.u) and(1 sec) duration, are used : (a) a Pulsed load of impulse profile e.g. a rail-gun not directly connected to the electrical network, but supplied via a diode rectifier and a capacitor (b) a Pulsed load of rectangular profile, connected directly to the electrical network. AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 45

  46. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION(Results) Here, we see the Generator active power for a “rectasngular” and for an “impulse”Pulsed Load profile installed at4.16 kVsupply. rectangular * generator loading 53% impulse Gen. active power (p.u) Time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 46

  47. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION(Results) Here, we see the influence ofPulsed Load profile installed at4.16 kVsupply, rectangular on System frequency : rectangular impulse Gen. active power (p.u) impulse Frequency Hz Time (sec) generator loading 53% Frequency deviates from the nominal value more in case of the rectangular pulsed load (as the system has to counteract to bigger absorbed energy by the pulsed load). Time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 47

  48. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION(Results) Influence of an impulseand of a rectangular profile pulsed load, installed at4.16 kVsupply, on Voltage RMS variation(p.u) at … 1HV Generator bus, 2440 V load bus 3 HV pulsed load and propulsion bus, 4115 V load bus 1 1 2 2 Voltage [p.u] Voltage [p.u] 3 3 4 4 Impulse profile Rectangular profile Time (sec) Time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 48

  49. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 3. AES CONFIGURATION(Results) The initial voltage sag, corresponding to the first msec of pulsed load application, is smaller, in the case of rectangular pulsed load. However, when the pulsed load (of rectangular form) is disconnected, a voltage overshoot occurs, resulting in this way to a similar voltage modulation for both cases, impulse (a) and rectangular (b) profile . Voltage (p.u.) Fig. 22 Time (sec) AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 49

  50. AES 2007 Investigation of voltage/frequency modulation in ship electric networks with pulsed loads according to STANAG 1008 design constraints F. Kanellos, I.K. Hatzilau, J. Prousalidis 4. DISCUSSION and CONCLUSIONS In this paper we study from the point of view of STANAG 1008 design constraints andvia Matlab-simulation the influence of some Pulsed Load and Network parameters, on Voltage and Frequency modulation at the LV part of a shipboard electrical network (being either conventional or in the context of AES). There are two main conclusions of interest, on which we must focus : AES 2007 , The Vision Redrawn - International Conference , LONDON, 25-26 Sept. 2007 50

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