OPERATING PRINCIPLE OF THE DSTATCOM

Basically, the DSTATCOM system is comprised of three main parts: a Voltage Source Converter (VSC), a set of coupling reactors and a controller. The basic principle of a DSTATCOM installed in a power system is the generation of a controllable ac voltage source by a voltage source inverter (VSI) connected to a dc capacitor (energy storage device). The ac voltage source, in general, appears behind a transformer leakage reactance. The active and reactive power transfer between the power system and the DSTATCOM is caused by the voltage difference across this reactance. The DSTATCOM is connected to the power networks where the voltage-quality problem is a concern. All required voltages and currents are measured and are fed into the controller to be compared with the commands. The controller then performs feedback control and outputs a set of switching signals to drive the main semiconductor switches (IGBT’s, which are used at the distribution level) of the power converter accordingly.

Figure: Block Diagram of the voltage source converter based DSTATCOM

The AC voltage control is achieved by firing angle control. Ideally the output voltage of the VSI is in phase with the bus (where the DSTATCOM is connected.) voltage. In steady state, the dc side capacitance is maintained at a fixed voltage and there is no real power exchange, except for losses. The DSTATCOM differs from other reactive power generating devices (such as shunt Capacitors, Static VAR Compensators etc.) in the sense that the ability for energy storage is not a rigid necessity but is only required for System unbalance or harmonic absorption.

There are two control objectives implemented in the DSTATCOM. One is the ac voltage regulation of the power system at the bus where the DSTATCOM is connected. And the other is dc voltage control across the capacitor inside the DSTATCOM. It is widely known that shunt reactive power injection can be used to control the bus voltage. In conventional control scheme, there are two voltage regulators designed for these purposes. AC voltage regulator for bus voltage control and dc voltage regulator for capacitor voltage control. In the simplest strategy, both the regulators are proportional integral (PI) type controllers.

Comments

PRIMARY SECONDARY AND TERTIARY FREQUENCY CONTROL IN POWER SYSTEMS

Primary, Secondary and Tertiary Frequency Control in Power Systems Author: Engr. Aneel Kumar Keywords: frequency control, primary frequency control, automatic generation control (AGC), tertiary control, load-frequency control, grid stability. Frequency control keeps the power grid stable by balancing generation and load. When generation and demand drift apart, system frequency moves away from its nominal value (50 or 60 Hz). Grids rely on three hierarchical control layers — Primary , Secondary (AGC), and Tertiary — to arrest frequency deviation, restore the set-point and optimize generation dispatch. Related: Power System Stability — causes & mitigation Overview of primary, secondary and tertiary frequency control in power systems. ⚡ Primary Frequency Control (Droop Control) Primary control is a fast, local response implemented by generator governors (dro...

CASCADED TRANSFORMERS METHOD FOR GENERATING AC HIGH VOLTAGE

High-Frequency AC High Voltage Generation Using Cascaded Transformers Author: Engr. Aneel Kumar Figure 1: Infographic representation of cascaded transformers method for generating high AC voltages. Introduction In high voltage engineering , generating very high alternating current (AC) voltages is essential for testing equipment like insulators, circuit breakers, power cables, and other apparatus. One common and effective method for producing such voltages is the cascaded transformers method . This technique uses a series connection of specially designed test transformers , where the secondary of one transformer feeds the primary of the next. In this way, voltages are built up step by step, achieving levels in the range of hundreds of kilovolts (kV) or even megavolts (MV). Working Principle The principle of cascaded connection relies on the fact that each...

ADVANTAGES OF INTERCONNECTED GRID SYSTEM

Interconnected Grid System: Working, Advantages, Disadvantages, and Comparison with Isolated Grids Author: Engr. Aneel Kumar Figure 1: Infographic showing key advantages of an interconnected grid system. Introduction An interconnected grid system refers to a network of multiple power generation sources, transmission lines, substations, and distribution systems that are linked across regions, states, or even countries. Unlike an isolated grid (or islanded grid) which operates independently, an interconnected grid allows electricity to flow between interconnected nodes, enabling numerous benefits and some trade-offs. In today’s energy landscape—where demand, renewable generation, reliability, and cost pressure are all increasing—understanding how an interconnected grid works, what factors are essential, and what its advantages and disadvantages are is critical for utility planners, reg...

ADVANTAGES AND DISADVANTAGES OF CORONA EFFECT IN TRANSMISSION LINES | ELECTRICAL ENGINEERING GUIDE

Advantages and Disadvantages of Corona Effect in Power Systems In high-voltage overhead transmission lines , the corona effect plays a critical role in system performance. Corona occurs when the air around a conductor becomes ionized due to high electric stress. While often seen as a drawback because of power losses and interference , it also provides certain engineering benefits . This article explains the advantages and disadvantages of corona effect in detail, with examples relevant to modern electrical power systems. ✅ Advantages of Corona Effect Increase in Virtual Conductor Diameter Due to corona formation, the surrounding air becomes partially conductive, increasing the virtual diameter of the conductor. This reduces electrostatic stress between conductors and minimizes insulation breakdown risks. Related Reading: Electrostatic Fields in High Voltage Engineering Reduction of Transient Surges Corona acts like a natural cushion for sudden ...

Advantages of Per Unit System in Power System Analysis | Electrical Engineering

Advantages of Per Unit System in Power System Analysis In electrical power engineering, the per unit (p.u.) system is one of the most widely used techniques for analyzing and modeling power systems. It is a method of expressing electrical quantities — such as voltage, current, power, and impedance — as fractions of chosen base values rather than their actual numerical magnitudes. This normalization technique provides a universal language for system calculations, minimizing errors, simplifying transformer modeling, and enabling consistency across multiple voltage levels. Because of these benefits, the per unit system is essential in fault analysis, load flow studies, transformer testing, and short-circuit calculations . ⚡ What is the Per Unit System? The per unit system is defined as: Q u a n t i t y ( p u ) = A c t u a l V a l u e B a s e V a l u e Quantity_{(pu)} = \dfrac{Actual \ Value}{Base \ Value} Q u an t i t y ( p u ) = B a se ...

FACTORS AFFECTING BATTERY PERFORMANCE

Batteries have limited life, usually showing a slow degradation of capacity until they reach 80 percent of their initial rating, followed by a comparatively rapid failure. Regardless of how or where a UPS is deployed, and what size it is, there are four primary factors that affect battery life: ambient temperature, battery chemistry, cycling and service. 1) AMBIENT TEMPERATURE The rated capacity of a battery is based on an ambient temperature of 25°C (77°F). It’s important to realize that any variation from this operating temperature can alter the battery’s performance and shorten its expected life. To help determine battery life in relation to temperature, remember that for every 8.3°C (15°F) average annual temperature above 25°C (77°F), the life of the battery is reduced by 50 percent. 2) BATTERY CHEMISTRY UPS batteries are electro-chemical devices whose ability to store and deliver power slowly decreases over time. Even if you follow all the guidelines for proper storage, us...

AC Transmission Line and Reactive Power Compensation: A Detailed Overview

Introduction The efficient operation of modern power systems depends significantly on the management of AC transmission lines and reactive power. Reactive power compensation is a vital technique for maintaining voltage stability, improving power transfer capability, and reducing system losses. This article explores the principles of AC transmission lines, the need for reactive power compensation, and its benefits in power systems. Keywords: Reactive Power Compensation Benefits, STATCOM vs SVC Efficiency, Power Transmission Stability Solutions, Voltage Stability in Long-Distance Grids, Dynamic Reactive Power Compensation. Fundamentals of AC Transmission Lines AC transmission lines are the backbone of modern power systems, connecting generation stations to distribution networks. They have distributed electrical parameters such as resistance ( R R R ), inductance ( L L ), capacitance ( C C ), and conductance ( G G ) along their length. These parameters influence ...

ENGINEERING ARTICLES

Search This Blog