MATLAB-SIMULNK MODEL OF AC GRID WITH NON-LINEAR

LOAD AND STATIC COMPENSATOR FOR POWER QUALITY IMPROVEMENT

Presented by

G.VENKATA SUBBAIAH Under the esteemed guidance of

Mr K.RAJENDRA, Asst Professor

OBJECTIVE

Aimed for power quality improvement The model is designed based on known algorithms of the

compensator operation and certain grid and load parameters. Efficiency of the compensator operation under various regimes power factor correction, grid current balancing for asymmetric

load and harmonics suppression, is also presented. Drawing attention to Static Compensators as multi-purpose

tools for Smart Grid formation is addresses as well. Index Terms— Power Quality, Harmonics, PFC, Static

Compensator.

INTRODUCTION

Improving the quality of electric power in modern electric grid is an important task.

A combination of conventional and renewable energy sources, a significant increase of a non-linear loads and the great complexity of operating modes requires a search for new means to reduce grid harmonics .

Effective tool for this is a Static Compensator (Statcom) .

This paper presents a detailed Matlab-Simulink model of a three-phase electric grid with a Statcom.

The paper shows simulations with specific verification that confirm its effectiveness.

An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of generating stations that produce electrical power, high-voltage transmission lines that carry power from distant sources to demand centers, and distribution lines that connect individual customers.

Non-linear loads generate harmonics of the current. These harmonics manifest their presence through two factors:

1. They themselves increase load to the system they flow through

2. They cause voltage drops on all the impedances throughout the system through which the currents flow.

The current harmonics are increasing the current loads to all the cabling, distribution frames, switching and circuit breaking devices, and supply transformers.

There any active work , This implies that the electrical system is exposed to higher loads and that the propagation losses and transformer losses grow. There are also increases in the current through the neutral conductor due to some harmonics in response to load imbalances

THREE PHASE ELECTRIC GRID WITH A STATCOM AND NON LINEAR

LOAD

The grid consists of a non-ideal voltage source (phases A, B, C, Ls, Rs), non-linear load consisting of three-phase diode rectifier with a resistor Rd and smoothing inductance Ld on the output and a Static Compensator

(Statcom) with bridge of transistors IGBT and diodes, capacitance Cdc and voltage Vdc on the input and

inductances Lc on the output. A Rf-Cf filter is also connected to the grid as well as other possible load.

BLOCK DIAGRAM OF STATCOM

STATCOM or Static Synchronous Compensator is a shunt device, which uses force-commutated power electronics (i.e. GTO, IGBT) to control power flow and improve transient stability on electrical power networks. It is also a member of the so-called Flexible AC Transmission System (FACTS) devices.

A STATCOM is composed of the following components:

1.Voltage Source Converter

a. Square wave inverter using gate turn off thyristors

b. PWM inverters using insulated gate bipolar transistors

2.DC capacitor

3.Inductive reactance(X)

4.Harmonic fiters

A current control mode (CCM) controller is used as the Statcom controlling unit. The control method is based on generating a PWM control pulses for IGBT bridge.

The main task of the controller is receiving a reference current for CCM. the principle of obtaining the reference current method is based on the instantaneous power values .

Primarily from the line voltages vab, vbc of the grid are formed by simple arithmetic operations on the phases Voltages vsa, vsb and vsc .

SIMULATION RESULTS

CONCLUSION

In this paper a particular Matlab-Simulink model of electric grid with a Statcom was developed.

The model enables verification of the different grid modes and evaluates the efficiency of its operation.

Checking the grid model containing a non-linear and unbalanced load shows the possibilities of STATCOM for providing high sinusoidal voltage and current in the grid

improve the power factor

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