OneCycle Control and Its Applications in Distributed Generation Keyue Smedley Dept. of Electrical Eng. and Computer Science University of California, Irvine, CA 92697, USA smedley@uci.edu 1
Table of Contents I. Our Power Systems It is time for renovation Power electronics is a key Component II. OneCycle Control A PWM Computer Active power filter derivation Universal OCC Controller III. Utility Applications Examples A possible configuration 2
I. Our Power System Thousands of generating stations, tens of thousands of transmission and distribution substations, 150 control area operators, and over 200,000 miles of transmission lines. One of the largest structural achievement by humans. 3
2001 Electricity flow in US (Quadrillion BTU) For every BTU electricity generated, twice of that amount is lost, which wastes the natural resources and creates environmental pollution. Courtesy of Energy Information Administration Annual review 4 3,333 BTU=1 kwh, 900million tons of coal/year
Issues in our current power system Grid Centralized generation: Long transmission line: Load harmonic currents: Large system: =>efficiency~30% =>consumes large amount of fossil fuel~70% =>environmental impact =>transmission losses =>system oscillation =>transformer heating =>reduced system capacity =>venerable to cascading faults 5
Power Electronics is a key element for distributed generation Regenerative Fuelcell Reversable inverter Statcon Inverter APF Central plant PFC Converter Inverter Converter Turbine Fuelcell Inverters renewable and alternative energy power generation PFC rectifierssinusoidal current use APF power quality control STATCON VAR compensation and voltage support 6
II. One Cycle Control d reset Cycle by cycle control =>fast and precise transient Q Q S R Comparator When 1/T s 0 t V 2 dt=v 1 t=dt s clock v1 Integrator with reset v2 V 2 d=v 1 OCC solves the first order polynomial equation CLK v (t) 1 v (t) Q Most power electronics problems can be expressed by a first order polynomial equation. 7
OCCA PWM Computer Clock Generator R R Integrator Integrator... I O 3 I O 2 w/ reset w/ reset I R Integrator w/ reset O v (t) CMP _ S R FF Q Q v 4 v 3 v 2 v 1 OCC solves nth order polynomial equations v 1 = v 2 d v 3 d 2 v 4 d 3 8
v a v b v c L a L b L c ThreePhase Converter Control e.g. active power filter derivation Sap San va Threephase nonlinear load Dap Sbp Sbn D an vb Dbp Scp Scn Dbn vc D cp Dcn P N E Control goal: V m 1 d an = R 1 d s 2 1 i a cn 1 2 i c d bn =1 V m = E R s R e v a v c = R e i a Control key equation 060 : i c 0 1 0 60 120 180 240 300 360 θ The line cycle is divided into six regions 9
ThreePhase Converter va,b,c Rsia Rsib Rsic iaref ibref icref ia,b,c a b c Current selection circuit La Lb Lc Region selection circuit Sap Sbp Scp San Sbn Scn Va Vb Vc 2 2 Onecycle control core Reset No multiplier, No DQ conversion, No software in the loop. ip in S Q R Q S Q R Q C Drive signal distributor PID P Vdc N to Sap San Sbp Sb n Scp Scn Vref _ Vdc sen sor Simple, Reliable, Robust, Modular, Universal. For symmetric or asymmetric systems. 10
A Universal 3phase Controller OCC controller is universal! Inverter Rectifier APF STATCON Etc. One controller does all! 11
III. OCC Applications P Nonlinear load P va,b,c ia,b,c La Lb Lc Sap Sbp Scp C Vdc Load Vdc sen sor va,b,c ia,b,c a b c iload La Lb Lc Sap Sbp Scp C Vdc Vdc sen sor San Sbn Scn icom San Sbn Scn Va Vb Vc N Va Vb Vc N Region selection circuit Region selection circuit Rsia Rsib Rsic PFC Current selection circuit ip in 2 2 Onecycle control core Reset S Q R Q S Q R Q Drive signal distributor PID to Sap San Sbp Sb n Scp Scn Vref _ Rsia Rsib Rsic Current selection circuit ip in 2 2 Onecycle control core Reset S Q R Q S Q R Q Drive signal distributor PID to Sap San Sbp Sb n Scp Scn Vref _ APF GCI va,b,c ia,b,c La Lb Lc Sap Sbp Scp C P Vdc dc source Vdc sen sor va,b,c ia,b,c Nonlinear load a b c iload La Lb Lc Sap Sbp Scp C P Vdc Vdc sen sor SVC San Sbn Scn icom San Sbn Scn Va Vb Vc N Va Vb Vc N Region selection circuit Region selection circuit Rsia Rsib Rsic Iref : kva kvb kvc Current selection circuit ip in 2 2 Onecycle control core Reset S Q R Q S Q R Q Drive signal distributor PID to Sap San Sbp Sb n Scp Scn Vref _ Iref : Rsia Rsib Rsic kva e jθ kvb e jθ kvc e jθ ip 2 Current selection circuit in 2 Onecycle control core Reset S Q R Q S Q R Q Drive signal distributor PID to Sap San Sbp Sb n Scp Scn Vref _ 12
Active Power Filters Grid APF Capacitive load Inductive load transformer substation APF actively cancels the harmonics from the load The line current is sinusoidal APF only processes the harmonic and reactive power Can be used in equipment, buildings, substations, etc 13
Experimental Waveforms Symmetric operation: Phase A line voltage Threephase currents THD=3.2% PF~1 Phase A line voltage Phase A line current Phase A APF current Phase A load current 14
Startup Transient Test Start Point Start Point Grid Voltage Grid Voltage Start Point Grid Current Start Point APF Current 15
Load Step Up Transient Test Load current> APF current > <Line current 16
UCI PEL Grid connected Inverter for Power Generation Renewable/Alternative Power Generation OCC Gr idt ied inv er te r Sinusoidal current injection Robust performance Maximum power point tracking 17
Onecycle Control Rectifiers for Harmonic Suppression Traditional rectifiers draw harmonic current Onecycle control rectifiers draw sinusoidal current 18
OCCSTATCOM for Reactive Power Compensation OCC STATCOM VAR Static Synchronous Compensator 1. Superior voltage supporting capability 2. Uses small dc capacitors instead of large dc capacitors 3. Needs smaller space than conventional switched capacitors. 19
One of Possible Hybrid Configuration Grid P Local area OCC Converter functions as: inverter rectifier active power filter var generator P Q H P Q H P P P nonlinear load nonlinear load nonlinear load nonlinear load OCC converter OCC converter OCC converter OCC converter OCC converter smedleyoccdg fuel cell unit fuel cell unit micro turbine micro turbine reversable fuel cell solar cells wind turbine 20
OCC Unified Power Quality Conditioner OCC UPF C Improve voltage quality. Improve current quality. Improve power system stability. Improve power system security. Improve transmission efficiency Energy Quality Items AF 1 (Series AF) AF 2 (shunt AF) Source voltage Load current harmonics harmonics suppression compensation Source voltage Load reactive Current Regulation compensation Unbalanced Load Voltage balancing operation Neutralline/ common Voltage flick/sag/dip mode current compensation cancellation DC Voltage regulation Impulse & EMI suppression 21
Voltage unbalance and harmonic compensation==> OCCUPQC Before After PhaseA Voltage PhaseA Voltage Load current: THD 25% Cos _ 0.76, PF 0.74 Line Current: THD 7% Cos _ 1, PF 1 <==Reactive and nonlinear Load current compensation Before After 22
Reversible OCC Rectifier Grid line current THD<0.5% PF~1. occ rectifier dc output Motor load, battery, or reversable fuelcells transformer substation Regenerative power generation Energy conservation 23
APFInverter in One Grid Nonlinear loads THD>30% Photo voltaic DC OCC GCI with MPPT line current THD<0.5% PF~1. transformer substation MPPT at DC side Cancel harmonics at ac side 24
Frequency Converter Grid Windpower OCC converter OCC converter variable frequency ac current THD<0.5% PF~1. line current THD<0.5% PF~1. transformer subs tation Two OCC converters back to back to Form high power quality frequency converter. 25
APFSTATCON in One Grid OCC STATCON Capacitive load transformer substation line current THD<0.5% VAR adjustable Inductive load Generate reactive as need Cancels the harmonics in the line. 26
OCC APF for Mega Power 150KVA OCC APF 150KVA OCC APF Grid 1MVA Windpower diode rectifier thyristor inverter variable frequency ac current THD<0.5% PF~1. line current THD<0.5% PF~1. transformer subs tation Combine with Diode/Thyristor type of converters To achieve high power and low THD. 27