Transcription of Topic 1: Basics of Power Systems
1 Topic 1: Basics of Power Mohsenian Rad (U of T)1 Networking and Distributed SystemsECE 5332: Communications and Control for SmartSpring 2012 Power SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid2 The Four Main Elements in Power Systems : Power Production / Generation Power Transmission Power Distribution Power Consumption / Load Of course, we also need monitoring and control SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid3 Power Production: Different Types: Traditional Renewable Capacity, Cost, Carbon Emission Step up TransformersPower SystemsDr.
2 Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid4 Power Transmission: High Voltage (HV) Transmission Lines Several Hundred Miles Switching Stations Transformers Circuit BreakersPower SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid5 The Power Transmission Grid in the United SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid6 Major Inter connections in the United SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid7 Power Distribution: Medium Voltage (MV) Transmission Lines (< 50 kV) Power Deliver to Load Locations Interface with Consumers / Metering Distribution Sub stations Step Down Transformers Distribution TransformersPower SystemsDr.
3 Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid8 Power Consumption: Industrial Commercial Residential Demand Response Controllable Load Non ControllablePower SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid9 GenerationTransmissionDistributionLoadPo wer SystemsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid10 Power system Control: Data Collection: Sensors, PMUs, etc. Decision Making: Controllers Actuators: Circuit Breakers, Grid Graph RepresentationDr.
4 Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid11 Nodes: BusesLinks: Transmission LinesGeneratorLoadPower Grid Graph RepresentationDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid12 Nodes: BusesLinks: Transmission LinesGeneratorLoadBuses(Voltage) Power Grid Graph RepresentationDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid13 Nodes: BusesLinks: Transmission LinesGeneratorLoadTransmission Lines ( Power Flow, Loss) Power Grid Graph RepresentationDr.
5 Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid14 Nodes: BusesLinks: Transmission LinesGeneratorLoadConsumersPower Grid Graph RepresentationDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid15 Nodes: BusesLinks: Transmission LinesGeneratorLoad10 MW3 MW7 MWTransmission Line AdmittanceDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid16 Admittance y is defined as the inverse of impedance z: z = r + j x (r: Resistance, x: Reactance) y = g + j b(g: Conductance, b: Susceptance) y = 1 / z Parameter g is usually positive Parameter b: Positive: Capacitor Negative: InductorTransmission Line AdmittanceDr.
6 Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid17 For the transmission line connecting bus ito bus k: Addmitance: yik Example:yik= 1 j 4 (per unit) Note that, yiiis denoted by yiand indicates: Susceptance for any shunt element (capacitor) to ground at bus i. Y-Bus MatrixDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid18 We define: Ybus= [ Yij] where Diagonal Elements: Off diagonal Elements: Note that Ybasmatrix depends on the Power grid topology and the admittance of all transmission lines.
7 N is the number of busses in the grid. NikkikiiiyyY,1ijijyY Y-Bus MatrixDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid19 Example: For a grid with 4 buses, we have: After separating the real and imaginary parts: 4342414434241343432313323124232423212211 413121413121yyyyyyyyyyyyyyyyyyyyyyyyyyyy YbusBjGYbus Bus VoltageDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid20 Let Videnote the voltage at bus i: Note that, Viis a phasor, with magnitudeand angle.
8 In most operating scenarios we have:iiiVV jijiVV Power Flow EquationsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid21 Let Sidenote the Power injectionat bus i:Si= Pi+ j Qi Generation Bus: Pi> 0 Load Bus: Pi< 0(negative Power injection)Active Power Reactive PowerPower Flow EquationsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid22 Using Kirchhoff laws, AC Power Flow Equationsbecome: Do we know all notations here? If we know enough variables, we can obtain the rest of variables by solving a system of nonlinear equations.
9 NjjkkjjkkjjkkNjjkkjjkkjjkkBGVVQBGVVP11)c os()sin()sin()cos( Power Flow EquationsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid23 The AC Power Flow Equations are complicated to solve. Next, we try to simplify the equations in three steps. Step 1: For most networks, G << B. Thus, we set G = 0: NjjkkjjkkNjjkkjjkkBVVQBVVP11)cos()sin( Power Flow EquationsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid24 Step 2: For most neighboring buses.
10 As a result, we have: 15 to10 ji 1)()(jkjkjkCosSin NjkjjkkNjjkkjjkkBVVQBVVP11)( Power Flow EquationsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid25 Step 3: In per unit, |Vi| is very close to ( to ). As a result, we have: . Pkhas a linear model and Qkis almost jiVV kNkjjkjkkNjkjkNjjkkjkbBBBQBP ,111)( Power Flow EquationsDr. Hamed Mohsenian-RadTexas Tech UniversityCommunications and Control in Smart Grid26 Step 3: In per unit, |Vi| is very close to ( to ).
