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Session 3 – Ship Electric Power Systems 10 of the Topics at UT Austin Prof. Mack Grady, ECE Dept. Voltage sag Topic 1. Load Modeling for Stability Studies Extracting the power electronic load Extracted power electronic load current component • Every time there is a thunderstorm, you get voltage sags on the transmission grid Key Findings: • The power electronic loads on nearby feeders • On utility feeders, single-phase power electronic momentarily drop the out,net giving us a chance to determine load 5-15% their is net MW and observe their response to voltage deviations • For PSSE stability simulations of the UT Austin 80MW find that the impact of these is “stability • system, We havewe carefully studied field data, plusloads lab-created friendly” for 3-cycle disturbances, but “stability unfriendly” experiments, and now have load models for nonlinear for 6-cycle or longer disturbances. loads that are suitable for traditional power grid stability studies. Topic 2. Harmonics Testing Station and Nonlinear Load Modeling Feedback LabVIEW-based controller maintains desired harmonic voltage spectrum at test load Vampf-in + 250Vdc − 1.5kW PWM Inverter LC Filter 240V/240V, 3kVA Isolation Transformer Inverter output summed with building voltage 120V/24V, 320VA Summing Junction Transformer 120Vac Building Voltage Vload + Test Load − + − • Precision voltage waveform control with feedback. Portable. • LabView based 5% V7, Peaky • 1kW inverter provides (or eliminates) the harmonic distortion, while the 60Hz building voltage provides the bulk of the load power. Thus, a compact design. Real-time synching with the grid frequency is part of the Jacobian-based feedback. • Can produce practically any complex voltage waveform – single or multiple harmonics, or sinusoidal. Repeatedly. The interaction between harmonic voltage and load current can be analyzed. 5% V7, Flattened • Results – Touted Norton-based models for nonlinear loads do not work. Better to assume simple harmonic current injection. Topic 3. Interharmonic Detection and Analysis • Motivation – Copious amounts of interharmonics generated by nonlinear multi-frequency power electronic devices, e.g., adjustable speed drives (ASDs) – Small amplitude interharmonics can be harmful to the shipboard system. • Objective Rectifier Inverter M G Source DC Link Load – Assess interharmonic-related PQ problems in a more quantitative way • Approach – Utilize higher-order-statistical (HOS) signal processing From M. Hernes, SINTEF Energy Research, September 2003 Excitation of a 14 Hz natural frequency of an offshore platform turbine-generator by a 14 Hz interharmonic current frequency • Achievements – Developed robust detection methods for interharmonics generated by ASDs – Developed ASD condition monitoring methods based on the unique interharmonic signatures of ASDs – Developed interharmonic-caused light-flicker assessment methods for LEDs and CFLs Topic 4. Machine Condition Monitoring Diagnostic Motivation Variable Resistor Accelerometer • As machines degrade, they often tend to • become progressively more nonlinear Classical power spectra can not quantify the multi-frequency phase coupling associated with nonlinear interactions Objective • To provide new nonlinear signatures of and physical insight into the degradation of rotating machines (Induction motor) (DC generator) Experimental setup used to evaluate the effectiveness of our new HOS-based approach Approach • Higher-Order Spectral (HOS) Analysis Achievements • Improve conventional HOS approach by utilizing the bicoherence • Discriminate between intrinsic nonlinearities of a healthy machine and fault-induced nonlinearities • Resolved several practical issues related to applying HOS to condition monitoring of rotating • machines Quantify the strength of the nonlinear interactions by estimating complex coupling coefficients Topic 5. Impact of Pulse Loads on Electric Ship Power Systems, With and Without Flywheel Energy Storage Systems Time-Domain Simulation Model* main_gen Vgen BRK_GEN 13.8 kV bus Main Generator 36MW 13.8kV ip_ac out_dc FESS_EM vin1 out_ref vin2 BRK_FESS Pulse load Flywheel Energy Storage Module EM Laucher Pulse Load 3.55 MJ Total Capacity Idc max = 24 kA 9ms duration, 30 shots per minute PMM1 Vin_pmm1 BRK_PMM1 Propulsion Module 6.25 MVA 6kV * PSCAD/EMTD model Initial Results •FESS reduces disturbances on the generator and propulsion motor during pulse load operation Ship Electric Power System UT Activities: Topic 6 Architecture of shipboard NGIPS AC distribution model (as built in Matlab/Simulink) GOAL • Re-build AC and DC models with independent solvers • Conduct analyses using multi-processor machines • Status: Started work on solutions of component models Generators Breakers Energy storage Propulsion Transformers Rectifiers Filter Motor Drive Propulsion Motor DC distribution model Ship Electric Power System UT Activities: Topic 7 Prime power generation studies Prime mover type Coupling method Electric generator type Power conversion • Gas turbines • Gear boxes • Wound-field DC output • Diesel engines • Direct • Permanent-magnet Variable AC output • Superconducting 24 possible topologies System size Analyzed 1 possible topology Plan to select and analyze other topologies MT30 LM2500 LM1600 Analyses System performance MT5 80 MW genset Fuel Volume (m3) Combination (MW) 5 15 20 40 101 20 20 20 20 112 Fuel consumption during 4 4 36 36 117 24-h mission for DDG-51 Ship Electric Power System UT Activities: Topic 8 Ship IPS components: Electric machine models Modeling effort focuses on capturing and exploring fundamental assumptions as well as solution software Stationary 3-axis synchronous machine model dq model of synchronous wound-field generator id + if Ll p λd Lm d ikd R L + f Rk f Vf d Lkd + - - - d-axis p λq iq v v s ikq Ll Lm q q-axis di f di di vd Ra id ( Ll Lmd ) d Lmd Lmd kd e ( Ll Lmq )iq e Lmq ikq dt dt dt di di kq vq Ra iq ( Ll Lmq ) d Lmq e ( Ll Lmd )id e Lmd i f e Lmd ikd dt dt di f di di 3 v f R f i f Lmd d ( Ll Lmd ) Lmd kd 2 dt dt dt di f dikd did dikd 0 Rkd ikd Lkd Lmd ( ) dt dt dt dt dikq dikq diq 0 Rkq ikq Lkq Lmq ( ) dt dt dt 3 Poles Te [( Lmq Lmd )id iq Lmd i f iq Lmd ikd iq Lmqikq id ] 2 2 Previous work: • dq model implemented in Simulink for study of balanced systems Rk L q kq vr T i is ir T d λ Ri L'i Li ' dt i ' L1 ( R L' )i L1v v Ri Te J iT L'i r d r dt (Te Tm T f ) Inductance matrix: L0 L 2 cos( 2 a ) L3 L 2 cos( 2 c ) L3 L 2 cos( 2 b ) Lmf cos( a ) Lmkd cos( a ) Lmkqsin( a ) L0 L 2 cos( 2 b ) L3 L 2 cos( 2 a ) Lmf cos( b ) Lmkd cos( b ) Lmkq sin( b ) L0 L 2 cos( 2 c ) Lmf cos( c ) Lmkd cos( c ) Lmkq sin( c ) L Llf Lfkd Lfkd 0 Llkd Lkdf 0 Llkq Lmkq On-going work: • Develop solution using Fortran 90/95/2003 • Build code so that it can run on multi-processor machines • Obtain solution on PC first • Run on supercomputers with system model Ship Electric Power System UT Activities: Topic 9 Ship IPS components: 100 MJ Energy storage module R RD 2 R R di v diD1 vac Rs RD1 di di iD1 s iD 2 s iD 4 s iD 5 D 2 D 4 D 5 d dt Ls Ls Ls Ls Ls dt dt dt Ls R RD 3 R R di di di v diD 2 vcb Rs RD 2 iD 2 s iD 3 s iD 5 s iD 6 D 3 D 5 D 6 d dt Ls Ls Ls Ls Ls dt dt dt Ls diD 3 vba Rs RD 3 R RD 4 R R di v di di iD 3 s iD 4 s iD 6 s iD1 D 4 D 6 D1 d dt Ls Ls Ls Ls Ls dt dt dt Ls R RD 5 R R di v diD 4 vac Rs RD 4 di di iD 4 s iD 5 s iD1 s iD 2 D 5 D1 D 2 d dt Ls Ls Ls Ls Ls dt dt dt Ls diD 5 vcb Rs RD 5 R RD 6 R R di di v di iD 5 s iD 6 s iD 2 s iD 3 D 6 D 2 D 3 d dt Ls Ls Ls Ls Ls dt dt dt Ls diD 6 vba Rs RD 6 R RD1 R R di v di di iD 6 s iD1 s iD 3 s iD 4 D1 D 3 D 4 d dt Ls Ls Ls Ls Ls dt dt dt Ls dvd (iD1 iD 3 iD 5 ) iload dt Cd Cd Rectifier did R 1 Lq v d a id e iq dt Ld Ld Ld diq R 1 Ld v q a iq e id e f dt Lq Lq Lq Lq 3 Poles Te ( f iq ( Ld Lq )id iq ) 2 2 Charging motor (Simple pm synchronous, no dampers) J d 2 m dt 2 d m m dt (Te Tm T fr ) Flywheel dynamics vd Ra id pd e q vq Ra iq pq e d v f R f i f p f d Ld id Laf i f Ldkd ikd q Lq iq Lqkq ikq 3 2 di1 v1 Rinv i1 dt di Linv 2 v 2 Rinv i 2 dt v i D1 1 R D1 Linv iD2 v2 RD2 i a (i1 i D1 ) (i 2 i D 2 ) Breaker V d v1 v 2 v 2 v an v nN f Laf id L ff i f L fkd ikd Alternator (wound-field w/ 2 dampers) v a vb vc 0 Inverter (equations for 1 leg only) Detailed performance model valid for a range of applications Ship Electric Power System UT Activities: Topic 9, cont. Ship IPS components: Energy storage module Example run Component models provide good system understanding showing flywheel storage well suited for ship applications Ship Electric Power System: UT Activities: Topic 10 MVDC, MVAC, and HFAC system simulation COTS baselines Work to be coordinated with ESRDC team members Prop Motor Inverter 5 kVDC Rectifier Gen Prime Mover Main Power Distribution Fuel Rectifier Aux Gen Prime Mover DC/DC Charge DC/AC Ship Service Power Loads Energy Storage Discharge High Pulse Power Loads Added to baseline THE EXPLORATION OF MVDC REQUIRES ADDING PRACTICAL COMPLEXITY TO THE BASIC PROBLEM Questions?