Labs for EGN 3375 Electromechanical Energy Systems at University of South Florida

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1 Labs for EGN 3375 Electromechanical Energy Systems at University of South Florida Author: Zhixin Miao, Lingling Fan, Yin Li, Minyue Ma, Zhengyu Wang Presented by: Zhengyu Wang Smart Grid Power System Laboratory Department of Electrical Engineering, University of South Florida

2 Outline Introduction Purpose of Labs Detailed Lab Design Contribution & Future Work Questions

3 Introduction This paper describes the labs designed for University of South Florida (USF) s undergraduate course EGN 3375 Electromechanical Energy Systems. To provide industrial level experience for undergraduate students, following software and hardware are employed: PSCAD OPAL-RT s RT-Lab Real-time Digital Simulator National Instruments (NI s) Control Toolkit: General Purpose Inverter Controller (GPIC), Singleboard RIO (sbrio) with LabVIEW as GUI. MOTORSOLVER s Electrical Machine Dyno-kits

4 Purpose of Lab The labs offer undergraduate students in-depth understanding of Faraday s Law, the key principle for transformers and rotating machines; The labs also expose students to the state-of-the-art simulation and control tools and offer students hand-on experiences.

5 Lab Design: The design emphases of lab are: Faraday s Law Transformers Electric Machines Lab sections are: Lab 1: PSCAD labs for transformer B-H curve plotting Lab 2: PSCAD and RT-Lab modeling of 3-phase transformers Lab 3: GPIC and sbrio enabled synchronous machine Faradays' Law Check Lab 4: GPIC and sbrio enabled induction machine Volt/Hz control and torque-speed curve plotting

6 Lab 1: B-H Curve Plotting Using PSCAD The relationship between magnetizing force (H) and flux density (B) is plotted as B-H curve. In PSCAD simulation, student shall build the circuit as shown on the right hand side. As described in paper, the flux density (B) and magnetizing force (H) are found to be proportional with primary side current (Ipp) and capacitor voltage (Vc). By measuring Ipp and Vc, B-H curve is shown. PSCAD Simulation Circuit B-H Curve

7 Lab 2: Three-phase Transformer Simulation In PSCAD and RT-Lab A three-phase Y-Y connected transformer is implemented in PSCAD. Due to Y-connection characteristic, the phase voltage and line-line voltage has following relationship. By running the PSCAD model, student shall observe the voltage magnitude change and 30 degrees phase difference. PSCAD Simulation Circuit Primary side voltage vs. Secondary side voltage

With a complete SimPowerSystems model, students will converter it to RT- Lab and run in real-time mode through RT-Lab

8 Cont. Next, student are taught to build a Y- Delta connected three-phase transformer circuit with MATLAB/Simulink and SimPowerSystems components. With a complete SimPowerSystems model, students will converter it to RT- Lab and run in real-time mode through RT-Lab Simulator. By assigning ports to output measurements, student can monitor the primary and secondary side voltages on oscilloscope. RT-Lab Modeling Experiment Setup Measurement of primary and secondary side voltages by oscilloscope

9 Lab 3: PMAC Synchronous Generator Open-circuit Voltage Relationship with Speed The objective of the Lab 3 is to explore the relation between PMAC Synchronous Generator Open-circuit Voltage and machine speed. In EGN 3375 class, the simplified form of Faraday s Law is expressed as following. Based on the equation, it is known that machine speed is proportional with open-circuit voltage. Block diagram of Lab 3 setup Since the PMAC synchronous generator is employed, the flux in the air gap is constant. So the measured open-circuit voltage and machine speed should plot a linear relationship. Open-circuit voltage vs. Machine speed Students are required to give multiple speed reference in LabVIEW based controller and observe the measurements of machine speed and generated line-to-line voltage RMS values. In result, the linear relationship shall be presented as shown in the picture on the left.

10 Cont. Physical lab setup of Lab 3

Lab 4: Induction Motor Volt/Hz Control and Torque-speed Curve Block diagram of Lab 4 setup The objective of the Lab 4 is to plot torque-speed curves for various stator frequencies.

11 Lab 4: Induction Motor Volt/Hz Control and Torque-speed Curve Block diagram of Lab 4 setup The objective of the Lab 4 is to plot torque-speed curves for various stator frequencies. In Lab 4, a DC machine is powered to perform as a controllable load to the induction machine through a DC/DC converter. Open-loop Volt/Hz control is applied to DC/AC converter to power the induction machine to build constant flux. Due to the connection between DC motor and induction motor, the torque is the same. For a DC motor with permanent magnet, its armature current is proportionally related the torque with a constant coefficient. Thus, the plot of DC motor armature current (Idc) versus speed is equivalent to the torquespeed curve of an induction motor. Physical setup of Lab 4

12 Cont The voltage applied on the DC machine is found based on the modulation index of DC/DC converter by: DC armature current Idc is computed based on the power conservation assuming switching loss is ignored for DC/DC converter: DC motor current vs. machine speed The default direction is into the DC motor. In the torque-speed plots, we treat the induction machine as a motor and the dc machine as generator.

13 Future Work Synchronous generator experiment DFIG experiment Etc.

14 Question?

15 Thank You! Contact info: Smart Grid Power System Laboratory University of South Florida

3.1.Introduction. Synchronous Machines

3.1.Introduction. Synchronous Machines 3.1.Introduction Synchronous Machines A synchronous machine is an ac rotating machine whose speed under steady state condition is proportional to the frequency of the current in its armature. The magnetic