Improved fuzzy - PI controller design for three-level shunt active power filter

International Journal of Scientific Engineering and Technology ISSN:2277-1581

Volume No.5 Issue No.1, pp: 63-66 01 Jan.2016

doi : 10.17950/ijset/v5s1/113 Page 63

Improved Fuzzy–PI Controller Design for Three-Level Shunt Active Power

Filter

MinhThuyen Chau1

, HuuPhuc Dinh2

, CongPhuong Vo2

1 Department of Electrical Engineering - Industrial University of Ho Chi Minh City, Viet Nam

2 Department of Electrical & Electronic Engineering - Ho Chi Minh City University of Transport, Viet Nam

Corresponding Email: [email protected]

Abstract: This paper proposes an improved fuzzy-pi controller

for three-level shunt active power filter. This controller has

proved the effectiveness of the improved fuzzy PI controller

compared with the traditional PI and improved PI controllers

in reducing dynamic response time, minimizing the error in

steady-state, reducing THD of source current.

Keywords: Active power filter, PI control, fuzzy logic control,

power factor

I. Introduction

Currently, the use of more and more of nonlinear loads cause

of electric quality in the grid becomes worse. To solve this

problem, there are many methods such as: using the passive

power filter circuit LC. The use of passive filter circuits is

simple, easy to make, low cost [1-3]. However, it also has many

disadvantages as easily resonate, instability. From here the

concept “active power filter (APF)” birth to overcome the

disadvantages of passive power filter circuits [4-8]. APF has the

ability to control online under load, regardless of the typical of

load and the solved resonance problem with the system’s

impedance. APF often there are two forms: three-phase three￾wire and three-phase four-wire. In this paper, we study for three￾phase three-wire APF.

Effective work of the APF depends on many factors,

including the influence of the voltage source inverter (VSI) and

the controller plays a very important role. Now there are many

controllers were using for the APF as traditional PI, Hysteresis,

Fuzzy, neural... Control method using a traditional PI controller

uses the most because of the simplicity and easy to experimental

implementation of its, but it’s hard flexible to online control of

process control [9-10]. With Hysteresis controller then

characterized by the ability to respond faster, but the error in

establishing large [11]. Fuzzy controller, there is no need of math

model, but the result depends on experience [12-14]. Neural

network control is capable of self-learning, adaptive, but the slow

response, complex [15]. Furthermore the APF models almost

only use two-level VSI, this lead to restrictions on capacity and

efficient compensation of the APF.

Therefore, this paper proposes a control method using

improved fuzzy-PI controller for three-level active power filter to

further enhance the effectiveness and scope of application of the

APF. This controller is controlled according to the individual

frequency based on the amplitude and angular frequency. The

advantage of this control is possible to give the error in steady￾state toward zero. The fuzzy regulator aims to adjust the PI

controller’s parameters. As such, this controller has the ability to

reduce the dynamic response time, minimizing the error in

steady-state, reduced THD of three-phase source current.

II. Principle of Operation of Three-level Shunt Active Power

Filter

Principle of operation of the three-level shunt active power

filter is shown as in figure 1.

source

si

Fi

Li

C1

C2

S11

S12

S13

S14

S21 S31 S22 S32 S23 S33 S24 S34

+ DC - U

Nonlinear load Fig 1. Topology of three-level shunt active power filter

According to figure 1, we have:

Is=iL-iF (1)

Assume that, nonlinear load current can be analysed out two

components: fundamental component iLf and harmonic

component, we have:

iL=iLf + iLh (2)

then compensation current by shunt active power filter must be

iapf = iLh , and result of source current is:

is = iL-iF = iLf (3)

From there we can see that it contains only the fundamental

component of the non-linear load and thus eliminated the

harmonic component, the result is the source current no harmonic

components.

III. Improved fuzzy-PI Controller Design for Three-level

Shunt Active Power Filter

Control diagram of improved fuzzy-PI controller design for

three-level shunt active power filter is shown as in figure 2. It

consist of two controllers: fuzzy and improved PI.

According to [12], the improved PI controller aims to reduce

error in steady-state toward zero and its transfer function is

Im

2 2

s

2K s

s (m )  