Fundamentals of Power Electronics and Power System with MATLAB Present by K.PremKumar, M.E., Lecture EEE, SVCET, Tirunelveli.

What is Power electronics Control

Power electronics devices Thyratrons,ignitrons and mercury arc rectifier SCR(Silicon Control Rectifier) Power MOSFET IGBT Power Transistor

Application of power electronics Battery charging Electric traction Solid state controllers for home appliances UPS

Advantages Higher efficiency Long life Small size and low weight Fast response

Disadvantage Produce harmonics in the supply system & controlled system Interference with communication system Produce low power factor at low voltage

Types of power electronics converters Diode rectifier AC-DC converters AC-AC converters DC-DC converters DC-AC converters

Power Electronics systems

Power System Generation Transmission Distribution

Structure of Power system Generators - convert one form of energy to electrical energy Transformer - transfer power or energy Transmission lines – transfer power from one location to another Control equipments – protection purpose (breaker, relay.,) Primary transmission (110kv,132kv,220kv,400kv or 700kv) Secondary transmission(33kv or 66kv) Primary distribution (11kv or 6.6kv) Secondary distribution(400v for 3Φ ,230v for 1Φ)

Transmission and distribution Transmission system Inter connection of two or more generating system Divided in to primary and secondary transmission Primary transmission -power loss very high -step up the voltage by step up transformer -transmit the power from SES to RES -primary transmission voltages are 110kv,132kv or 220k or 400kv or 765kv

Secondary Transmission Continuation… Secondary Transmission - Link b/w RES to SS -voltage is step down by step down transformer -voltage values are 66kv or 33kv Primary distributor - Link b/w SS to DS -voltage is step down to 11kv or 6.6kv

Secondary distributors Continuation… Secondary distributors -voltage is step down to 400v or 230 v - Link b/w DS to consumers

Building and Simulating a Simple Circuit Introduction Building the Electrical Circuit with powerlib Library

Introduction Explore the powerlib library Learn how to build a simple circuit from the powerlib library Interconnect Simulink® blocks with your circuit

Example 1: The circuit below represents an equivalent power system feeding a 300 km transmission line. The line is compensated by a shunt inductor at its receiving end. A circuit breaker allows energizing and de-energizing of the line. To simplify matters, only one of the three phases is represented. The parameters shown in the figure are typical of a 735 kV power system.

Procedure for simulation Open the SimPowerSystems main library by entering the following command at the MATLAB® prompt. >>powerlib This command displays a Simulink window showing icons of different block libraries.

(424.4e3*sqrt(2) volts in this case). Continuation… From the File menu of the powerlib window, open a new window to contain your first circuit and save it as circuit1. Open the Electrical Sources library and copy the AC Voltage Source block into the circuit1 window. Open the AC Voltage Source dialog box by double-clicking the icon and enter the Amplitude, Phase, and Frequency parameters according to the values shown in Circuit to Be Modeled. Note that the amplitude to be specified for a sinusoidal source is its peak value (424.4e3*sqrt(2) volts in this case).

Change the name of this block from AC Voltage Source to Vs. Continuation… Change the name of this block from AC Voltage Source to Vs. Copy the Parallel RLC Branch block, which can be found in the Elements library of powerlib, set its parameters as shown in Circuit to Be Modeled, and name it Z_eq. The resistance Rs_eq of the circuit can be obtained from the Parallel RLC Branch block. Duplicate the Parallel RLC Branch block, which is already in your circuit1 window. Select R for the Branch Type parameter and set the R parameter according to Circuit to Be Modeled. Once the dialog box is closed, notice that the L and C components have disappeared so that the icon now shows a single resistor.

Continuation… Name this block Rs_eq. Resize the various components and interconnect blocks by dragging lines from outputs to inputs of appropriate blocks.

Continuation… To complete the circuit of Circuit to Be Modeled, you need to add a transmission line and a shunt reactor. The model of a line with uniformly distributed R, L, and C parameters normally consists of a delay equal to the wave propagation time along the line. This model cannot be simulated as a linear system because a delay corresponds to an infinite number of states. However, a good approximation of the line with a finite number of states can be obtained by cascading several PI circuits, each representing a small section of the line.   A PI section consists of a series R-L branch and two shunt C branches. The model accuracy depends on the number of PI sections used for the model. Copy the PI Section Line block from the Elements library into the circuit1 window, set its parameters as shown in Circuit to Be Modeled, and specify one line section.

Continuation… The shunt reactor is modeled by a resistor in series with an inductor. You could use a Series RLC Branch block to model the shunt reactor, but then you would have to manually calculate and set the R and L values from the quality factor and reactive power specified in Circuit to Be Modeled.   Therefore, you might find it more convenient to use a Series RLC Load block that allows you to specify directly the active and reactive powers absorbed by the shunt reactor. Copy the Series RLC Load block, which can be found in the Elements library of powerlib. Name this block 110 Mvar. Set its parameters as follows: Vn=424.4e3 V Fn=60 Hz P=110e6 QL=110e6 vars QC=0

Continuation…

Continuation… You need a Voltage Measurement block to measure the voltage at node B1. This block is found in the Measurements library of powerlib. Copy it and name it U1. Connect its positive input to the node B1 and its negative input to a new Ground block. To observe the voltage measured by the Voltage Measurement block named U1, a display system is needed. This can be any device found in the Simulink Sinks library.

Continuation… From the Simulation menu, select Start. Open the Scope blocks and observe the voltages at nodes B1 and B2. While the simulation is running, open the Vs block dialog box and modify the amplitude. Observe the effect on the two scopes. You can also modify the frequency and the phase. You can zoom in on the waveforms in the scope windows by drawing a box around the region of interest with the left mouse button.

Example 2: Find out the response of boost DC-DC converter. The IGBT is switched on and off at a frequency of 10 kHz to transfer energy from the DC source to the load (RC). The average output voltage (VR) is a function of the duty cycle (a) of the IGBT switch:

Procedure for simulation Open the SimPowerSystems main library by entering the following command at the MATLAB® prompt. >>powerlib This command displays a Simulink window showing icons of different block libraries.

Continuation… From the File menu of the powerlib window, open a new window to contain your first circuit and save it as circuit2. Open the Electrical Sources library and copy the DC Voltage Source block into the circuit2 window. Open the DC Voltage Source dialog box by double-clicking the icon and enter the Amplitude according to the values shown in Circuit to Be Modeled. Change the name of this block from DC Voltage Source to Vdc. Copy the Parallel RLC Branch block, which can be found in the Elements library of powerlib, set its parameters as shown in Circuit to Be Modeled, and name it L1.

Continuation… The inductance of the circuit can be obtained from the Parallel RLC Branch block. Duplicate the Parallel RLC Branch block, which is already in your circuit1 window. Select L for the Branch Type parameter and set the L parameter according to Circuit to Be Modeled. Once the dialog box is closed, notice that the R and C components have disappeared so that the icon now shows a single inductor. Name this block L1.

Continuation… Copy the IGBT block, which can be found in the element library of powerlib, and connect as per circuit to be modeled, and name IGBT.

Continuation… Copy the diode and parallel RLC branch block, which can be found in the element library of powerlib, and connect as per circuit to be modeled, and name diode, R and C.

Continuation… Copy the pulse generator, voltage measurement and scope block, which can be found in the element library of powerlib, and connect as per circuit to be modeled. Set the parameter of pulse generator as shown in figure

Continuation… Resize the various components and interconnect blocks by dragging lines from outputs to inputs of appropriate blocks.

Continuation… From the Simulation menu, select Start. Open the Scope blocks and observe the waveforms. While the simulation is running, open the Vdc block dialog box and modify the amplitude. Observe the effect on the scopes.

Thank you