The Switching Function: Analysis of Power Electronic Circuits
By demonstrating the usefulness of the switching function in analyzing power electronic circuits, this text derives compact expressions for output voltage and current and input current.
TABLE OF CONTENTS The Switching Function: Analysis of Power Electronic Circuits
Part 5: Active Filters
Chapter List
- Chapter 18: The Thyristor-Controlled Reactor
- Chapter 19: The Switched Capacitor Active Filters
- Chapter 20: The Inverter Configuration Active Filter
- Chapter 21: Single Phase Rectification with Active Line Shaping
18.1 Introduction
There are many configurations for active power filters [12]. The thyristor-controlled reactor is perhaps one of the first configurations [13].
The current is controlled in an inductor by delaying the triggering of the thyristors. There are two versions; the single reactor and the two-reactor circuits. For the single reactor the firing angle is limited to the range 90 180 and for the two-reactor circuit the firing angle is extended from 0 180 . In the former case, the current is discontinuous giving rise to a high %THD figure. In the latter case, the current is continuous up to a firing angle of 90 giving a low-distortion figure. The three phase configuration - even though not presented here - with a delta or star connection can easily be derived from the presented material.
A parallel capacitor is included to provide leading reactive power.
18.2 The Single Reactor Arrangement
18.2.1 Operation and the Switching Function
Triggering for each thyristor is done at the correct half-cycle: hence thyristor TH1 is fired during the positive half-cycle and TH2 during the negative half-cycle, Fig. 18.1. The delay angle, ?, is set to allow a smaller or bigger part of the half-cycle to pass to the output. It can be varied from the load phase angle to 180 allowing smooth control of the level of the...
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