Overview of Actuation Thrust

Overview of Actuation Thrust Fred Wang Thrust Leader, UTK Professor Prepared for CURENT Course September 4, 2013

Actuation in CURENT Wide Area Control of Power Power Grid Grid Measurement &Monitoring HVDC Storage PMU FDR WAMS Communication Communication Solar Farm Actuation Wind Farm PSS Responsive Load FACTS Generator 1-2

Actuation Technology Linkages Engineered Systems Hardware Testbed Testbeds Monitoring Modeling Large Scale Testbed Control Actuation Enabling Technologies Situational Awareness & Visualization Estimation Communication & Cybersecurity Control Design & Implementation System-level Actuation Functions Fundamental Knowledge Wide-area Measurements Modeling Methodology Control Architecture Economics & Social Impact Actuator & Transmission Architecture

Basic Actuation Functions in Power Systems Power flow control Voltage and var support Stability Protection Separation Fault current limiting Overvoltage suppression Energy source and load grid interface 1-4

Power Flow Control Power flow is determined by Kirchhoff's Laws, e.g. G1 G2 P V V X 1 2 12 sin 1 2 12 V 1 P D1 P G1 P 1 P G2 P 2 V 2 P D2 V 3 P G3 P D3 G3 1-5

Non Power Electronics Power Flow Actuators Voltage Generators (exciter control - PE) Switched shunt capacitor banks Transformer tap changer Impedance Switched lines Series compensation (switched series capacitors) Angle Phase-shifting transformers 1-6

Example of Phase-shifting Transformers A direct, symmetrical PST with limited range and voltage magnitude change. There are also other types (e.g. indirect PST) 1-7

Non Power Electronics Voltage & Var Actuators Generator (exciter) Condenser Switched capacitor banks Transformer tap changer Load management 1-8

Non Power Electronics Actuator for Stability Generator Governor Power system stabilizer (excitation) Switchgear Line switching Source and load switching Switched compensators Reactors Capacitors 1-9

Protection - Breakers Live-tank breakers Dead-tank breakers 1-10

Breaker with Switching Resistors Switching resistors Must absorb energy during switching => shorted after several ms! 1-11

Equivalent Circuit Short-circuit Interruption R L L L I S Fixed Contact Moving Contact U N C L U S U 1 U 2 Fault! I S 10 U S V Sw V Src 5 0 U S rated current Fault! -5-40 -30-20 -10-10 0 10 20 30 t [ms] 1-12

Equivalent Circuit Short-circuit Interruption R L L L I S Fixed Contact Moving Contact C L U S U N U 1 U 2 Fault! I S 10 U S U s rated current 5 0 U S U N Fault! -5-40 -30-20 -10-10 0 10 20 30 t [ms] 1-13

Equivalent Circuit Short-circuit Interruption R L L L I S Fixed Contact Moving Contact C L U S U N U 1 U 2 Fault! I S 10 U S U s rated current 5 0 U S U N Fault! -5-40 -30-20 -10-10 0 10 20 30 t [ms] 1-14

Equivalent Circuit Short-circuit Interruption R L L L I S Fixed Contact Moving Contact U N C L U S U 1 U 2 Fault! I S 10 U S U s rated current 5 0 U S U N -40-30 -20 Fault! -10-5 1 f 2-10 L C L L 0 10 20 30 t [ms] 1-15

Circuit Breaker Modeling Mechanical delay time (from command to contact separation): min 10...20 ms opening time = contact separation current interruption: default at zero crossing Arcing time: 1...5 cycles depending on CB type and current wave form include arcing time in opening time Arc modeling Arc voltage current relationship highly complex (parameters: CB design, thermodynamics) generic models mostly insufficient special modeling necessary zero arcing voltage for high voltage systems constant value (10...100 V) for low voltage systems 1-16

Overvoltage Protection Spark Gaps Metallic electrodes providing a gas insulated gap to flash over Very robust, but large variance in protection level Magnetically blown Surge Arresters Same basic principle as spark gaps, adopt SiC varistors but can handle much higher energy dissipation Metal Oxide Varistor (MOV) Ceramic composites based on zinc, bismuth, and cobalt Highly non-linear current-voltage characteristic Very precise and stable protection level Limited overload capability I V 20 1-17

MOV and Surge Arresters ABB arrester with silicon rubber enclosure (POLIM family) ABB arrester type MWK after overload test with 20 ka/0.2 s Metal Oxide Varistor I V diam = 38... 75 mm W/V = 3.6... 13.3 kj/kv Uc 1-18

Metal Oxide Varistor (MOV) peak voltage continuous operating voltage 1-19

Protection - Arresters 1-20

Power Electronics Based Power Flow Control V 1 / 1 V 2 / 2 Powerflow P ~ = = ~ P V 1 X V 12 2 sin ( 1 2 ) + P HVDC Static Var Compensation (SVC) Series Compensation (SC) Phase Shifting Transformers HVDC and HVDC Light FACTS = Flexible AC Transmission System 1-21

Power Electronics Power Flow Actuator Voltage SVC (Static Var Compensator) STATCOM (Static Synchronous Compensator) Impedance TCSC (Thyristor Controlled Series Compensator) SSSC (Static Series Synchronous Compensator) Angle All TCPFT (Thyristor Controlled Phase-shifting Transformers or Angle Regulator) HVDC UPFC (Unified power flow controller) 1-22

Thyristor Controlled Series Capacitor (TCSC) A capacitive reactance compensator which consists of a series capacitor bank shunted by a thyristor-controlled reactor in order to provide a smoothly variable series capacitive reactance. Can be one large unit or several small ones. Limits fault current when reactor is fully on. AC Capacitor Line Reactor Thyristor valve 1-23

STATCOM and SSSC A static synchronous generator operated without an external electric energy source Can be shunt or series connected As a shunt compensator, can inject reactive power As a series compensator, its voltage is in quadrature with, and controllable independently of, the line current for the purpose of increasing or decreasing the overall reactive voltage drop across the line and thereby controlling the transmitted electric power. Line Interface Energy storage Transformer Converter 1-24

Unified Power Flow Controller The UPFC, by means of angularly unconstrained series voltage injection, is able to control, concurrently or selectively, the transmission line voltage, impedance, and angle or, alternatively, the real and reactive power flow in the line. The UPFC may also provide independently controllable shunt reactive compensation. AC line Coupling Xfmr Coupling Xfmr DC link Shunt VSI STATCOM SSSC Series VSI 1-25

HVDC Technology Development Mercury Arc Valve HVDC (Phased out) Thyristor Valve HVDC Classic IGBT (Transistor) Valve HVDC Light 1954 1970 1980 2000 Year Pros: Low losses Cons: Reliability Maintenance Environment Pros: Reliable Scalable Cons: Footprint Pros: Controllability Footprint DC Grids Cons: Losses 1-26

MUSD 800 kv DC for long distance bulk power transmission Tranmission of 6000 MW over 2000 km. Total evaluated costs in MUSD 3500 3000 2500 2000 1500 1000 500 0 Losses Line cost Station cost 765 kv AC 500 kv DC 800 kv DC Number of lines: Right of way ~300 ~ 120 ~ 90 (meter) 1-27

Power Electronics Actuator for Stability 1 st Thyristor-Controlled Series Compensation (TCSC) Project 1-28

PE for Stability: Dynamic Energy Storage Energy storage connected on DC-side of converter (SVC Light) Size depends on power level and duration Charge energy equal to load energy Focus on dynamic, manages: High number charge and discharge cycles High Power at medium duration Chosen high performance battery as energy storage 1-29

Battery Energy Storage Example Golden Valley Electric Association BESS Project 40 MW Rating 10 MWH Battery Capacity 1-30

Power Electronics Actuator for Protection 1-31

High Voltage DC Circuit Breaker Schematic Solid-State Trip Circuit Load High-Voltage ETO-based DC circuit breaker with an RC snubber. 1-32

High-Voltage DC Circuit Breaker A 3000V high-voltage DC circuit breaker to protect the DC capacitor bank in industrial power converter applications. 1-33

Test Waveform V out (5 V/div) Anode Current (200 A/div) Anode Voltage (500 V/div) Shoot-Through Failure Point t d t f (0.5 s) (2 s) The high-voltage DC circuit breaker tested at 1kA under 2kV DC bus. 1-34

Fault Current Limiting Circuit Breaker inductor rectifier DC CB Fast acting circuit breaker can function as a fault current limiter During normal operation, the circuit breaker shorts the highimpedance inductor, exhibits low impedance. During fault condition, the circuit breaker is open, the fault current flow through the high impedance inductor, thus limit the fault current to a tolerance level. 1-35

Fault current at secondery side (A) Fault Current Limiter Simulation Results 20000 15000 w/o FCL w/ FCL w/ IFCL 10000 5000 0-5000 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2 Time (s) Without FCL, the prospective fault current could reach 10x rated current (red dash line). Traditional FCL acts at current zero-crossing point, it can t suppress the first peak (blue dot line). Fast acting FCL limits the fault current in all range (pink solid). 1-36

Summary of Actuation Technologies Traditional non power electronics based actuators have limited actuation capability. The system is generally not very flexible PE based actuators (FACTS, HVDC) can be very effective for Power flow control Voltage and var control System stability Protection Interface of source and load Issues: cost, reliability Solutions: new PE technology, modular approach, hybrid approach, different architecture 1-37

Impedance Based Actuators (1) 1-38

Impedance Based Controllers (2) 1-39

Impedance Based Controllers (3) All impedance based controllers have common converter functions ac bi-directional switch 1-40

LOAD Controller STATCOM - Static Synchronous Compensator Mini-HVDC (Voltage Source) Shunt Connected Current Controllers One-line Configuration System Functions Stability enhancement V regulation & VAR compensation System Interconnect Power flow control Stability enhancement Control Principle VAR control through current control in shunt connection Power and Var control through back-to-back converters Basic PE Function Bi-directional AC/DC VSI Bi-directional AC/DC VSI Active Filter (Shunt connected) Harmonic current filtering Inject canceling harmonic current Bi-directional AC/DC VSI UPS (Line-interactive type shown) LOAD Standby power Power conditioning V or I regulation depending on operating mode Bi-directional AC/DC VSI and bidirectional AC switch DER Interconnect - Mirco-turbine, fuel cells, wind or solar generator, energy storage systems LOAD Interface to AC grid Power conditioning V or I regulation depending on operating mode Bi-directional AC/DC VSI and DC/DC converter 1-41

Series Connected Voltage Controllers Controller SSSC - Static Series Synchronous compensator DVR - Dynamic Voltage Restorer Active Filter (Series connected) One-line Configuration System Functions Power flow control Stability enhancement Voltage regulation and conditioning Harmonic voltage filtering Control Principle VAR control through voltage control Injecting voltage to compensate for sags and unbalance Inject canceling harmonic voltage Basic PE Function Bi-directional AC/DC VSI Bi-directional AC/DC VSI Bi-directional AC/DC VSI All series connected voltage controllers and shunt connected current controllers have common converter functions AC/DC VSI 1-42

Basic PE Building Block Functions v dc 3-ph VSC v a v b v c R L i a i b i c m a m b m c C R dc i dc i m R L v dc 3-ph Switch DC-DC 1-43

Modular Approach - Distributed FACTS Distributed Series Static Compensator 1-44

Modular Converters for Multi-Terminal HVDC Systems Modular multilevel converter (MMC) P SM SM SM SM SM SM C sub + L arm L arm L arm A B C L arm L arm L arm SM SM SM SM SM SM N 1-45

Hybrid Approach - Thin AC Converter 1-46

Actuation Thrust Objectives and Challenges Objectives Develop actuation methodology and system architecture that will enable wide-area control in a transmission grid with high penetration of renewable energy sources Challenges 1) Lack of cost effective wide-area system-level actuators 2) Lack of global actuation functions for the existing actuators or lack of knowledge how to use these actuators for global functions 3) System architecture not best suited for wide-area coordinated actuation and control for network with high penetration of renewable energy sources 4) Lack of design and control methodologies for systems with power electronics converters interfacing a high percentage of sources and loads

Technical Approaches and Research Focus Multifunctional actuators to exploit full capabilities of existing or future actuators Renewable energy sources supporting system control FACTS, HVDC Flexible and controllable transmission architecture Hybrid AC/DC Multi-terminal HVDC

Hybrid AC/DC Transmission P 1 2 3V ph sin X 1 2 3V a sin 2 ac dc d d P2 P + P + V I X 1-49

Multi-terminal HVDC in NPCC System Area 1 (NYISO) G1 1 5 6 7 8 Area 2 (ISO-NE) 9 10 11 3 G3 L7 C7 C9 L9 2 G2 4 G4 L12 L13 Area 3 (Load Center) VSC 4 VSC 3 DC cable VSC 2 VSC 1 Area 3 (MTDC) Wind Farm II Wind Farm I

MT-HVDC Testbed Interface

Conclusions Actuation thrust provides essential technology for wide-area coordinated control, and directly supports the CURENT systems. Thrust research plan has been established with focus on multifunctional actuators and flexible architecture. 1-52