E x R E x R 1:a E x R/a 2

E j 2.0 j j 0.05 Generator terminal voltage maintained at pu j 0.08 V/a Load voltage (V) maintained at pu by varying tap ratio a Reflected load admittance on primary side of transformer = (0.75 – j 0.375)*(a * a) Generator transformer Load transformer Transmission line

   V s  a (tap) discretiser amax amin     1+sT filter deadband sign     100 s   1+s Gen Terminal Voltage E  

Equilibrium Large disturbance from Equilibrium (spring breaks!)

 Controller + Actuator P G0 Turbine PGPG Gate or Valve Position  REF  - +

P L1 P L2 Pe1 Pe2 xg xe2xe1 RX E1  E2  RX V1V1 V2V2  22 P 1, Q 1 P 2, Q 2

Turbine Governor Generator Valve / Gate position Mechanical Power Speed/Rotor Angle  Pm0 (“Load Ref”)      ref   KG GENERATOR + TURBINE/ GOVERNOR +

GENERATOR + TURBINE/ GOVERNOR ON AGC GENERATORS + TURBINES/ GOVERNORS NOT ON AGC GENERATORS + TURBINES/ GOVERNORS NOT ON AGC GENERATOR + TURBINE/ GOVERNOR ON AGC NETWORK (AREA 1) NETWORK (AREA 2) Tie Line Measured Power Flow on Tie Line B1 Speed deviation from nominal Speed deviation from nominal k1/sk2/s  - +  + + B2  P 12  P mo1  P mo2

DC AC Controlled Rectifier Main Generator

Diode Bridge (rotating) Field Winding AC generator RR R S SSS NSNS R Permanent Magnet Generator R: Rotating Member S: Stationary Member Control Signals From Regulator

Controller  Vref Measured Terminal Voltage Stabilizing / Limiting Signals To Thyristor Bridge

Idc Va Ia Va: phase a to neutral voltage Ia : phase a current flowing into the converter  Delay Angle of Converter P: Power Drawn by Converter Q: Reactive power drawn by Converter P > 0 Q > 0  P, Q  DC side P, Q Rectifier Inverter Va Ia P < 0 Q > 0  

 V i V i V i V i  =180  =90     

Location 1 Location 2 Phase angular difference between the two can be determined independently if a common timing pulse is transmitted to the locations simultaneously

(STATIC) DATA ACQUISITION (executes every 2-4 seconds) Voltage/ Power “Raw” Measurements Status of Circuit Breakers STATIC STATE ESTIMATION (executes every 10s to 1 min) Present Network / Load/ Generation Configuration (Operating Condition) Remote Measurements STATIC / DYNAMIC SECURITY ANALYSIS (executes every 1 – 10 mins) NORMAL STATE ALERT STATE SECURITY CONSTRAINED OPTIMAL POWER FLOW (Executes every 10 – 30 mins) REAL / REACTIVE POWER SCHEDULE CHANGES OR

Different Entities in a Deregulated Environment Generator Companies (Gencos) Transmission Companies (Transcos) Distribution Companies (Discos) Independent System Operator (ISO) Retail Energy Service Companies (Rescos) Customers

The Competition Competitive Generation Market Many sellers vying to sell to the customers Transco Monopoly Franchise Disco Monopoly Franchise Competitive Retail Power Market Many retailers vying to sell to the customers CompetitionMonopoly Competition

E Reflected load admittance on primary side of transformer = ( )*(a*a) j2.0 R j0.145 Transmission Line 0.01+j0.05 Generator Transformer 0.01+j0.05 Load transformer j0.08 VaVa Generator terminal voltage Maintained at pu Load Voltage (V) maintained at pu by varying tap ratio ‘a’

E j 2.0 j j 0.05 Generator terminal voltage maintained at pu j 0.08 V/a Load voltage (V) maintained at pu by varying tap ratio a Reflected load admittance on primary side of transformer = (0.75 – j 0.375)*(a * a) Generator transformer Load transformer Transmission line E R

NORMAL Load tracking, economic dispatch RESTORATIVE Resynchronization IN EXTREMIS Cut losses, protect equipment ALERT Preventive Control EMERGENCY Heroic Action E, I SECURE Reductions in reserve margins Violation of inequality constraints A - Secure SYSTEM INTACT SYSTEM NOT INTACT System splitting and / or load loss E, I INSECURE E: Equality constraints, I: Inequality constraints, -: Negation