Tài liệu tiếng anh Điện tử công suất mạch MERS Magnetic engergy recovery switch

Luận văn, Điện tử công suất, đề tài tốt nghiệp, đồ án, thực tập tốt nghiệp, đề tài

Application of Magnetic Energy Recovery Switch (MERS)

for Power Factor Correction

Jun Narushima, Kouta Inoue, Taku Takaku, Takanori Isobe, Tadayuki Kitahara, Ryuichi Shimada

(Tokyo Institute of Technology)

IPEC-Niigata 2005 April 4-8, 2005 Toki Messe Niigata, Japan

Table of contents

Operation principles of MERS.

Power factor correction of phase induction motor.

Magnetic Energy Recovery Switch

Bi-directional currentswitch

Simple circuit, simplecontrol

Can shut off current

in any phase

Connected in series

S1 S2

S4 S3

MERS has a fucnction of automatic power factor correction

regardless of the load inpedance.

Operational mode (a)(b)

Current decreases rapidly.

-When the capacitor is

not charged, Current flows

2

3

Reactance voltage compensation

4

L R

L R

When v is the maximum

value, i becomes zero.

A gate signal shifted by δ

is required for power factor correction.

δ depends on the load

impedance ratio X / X

c d

L C

Gate angle for power factor 1

V ≒ 0.7~1 p.u.C

V > 1 p.u.C

Automatic power factor correction is realized under the

conditionof X / X < 1C L

Single-phase induction motor

8

Low cost.

Bad power factor.

It requires large power capacity

and causes an increase in cost

Easy to use.

Single-phase induction motors

are widely used

(home, agriculture, factory )

The power factor is

0.3~0.7 (at the best)

Costly power converter

Experimental setup

9

Tested machine

Load machine Controller

Load machine DC motor

Gate Control Circuit

Single-phase induction motor

IGBTs of MERS are controlled

synchronusly with the AC system

Power factor

11

The power factorswithout MERS arevarying between0.8~0.4

The power factorswith MERS aremaintained within0.9~1.0

Input current

12

The power factorcorrection decreasesinput current

Improves utilization of electrical equipment.

(decreases required power capacity.)

13

Efficiecy does not decreases , although the current waveform

is distorted.

Includes losses of motor and MERS.

MERS improve the power factor while it does not affect the

load side

The current waveforms by phase shifting control have large

distotion and harmonic components

PWM control can be used for applications which require clean

sinusoidal waveforms

A reference current i is

determined by input voltage

to maintain the power factor

MERS with PWM control also achieves the power factor

correction.

Power factor

16

The power factor by phase shifting control decreases to 0.9 at low load.

(Higher harmonic ponents cause insufficient power factor correction.)

com-The power factor by PWM control is always maintained to be 1

The sinusoidal current generated by the PWM control

improves the power factor more efficiently.

with MERS(PWM)

with MERS (Phase shifting)

17

Efficiecy of PWM control is almost the same as that of phase shifting.

Although the sinusoidal current waveform

decreases losses of motor, switching losses are increased by PWM.

The PWM control of MERS does not have significant effect

Energy saving by MERS

The experiment to demonstrate energy saving by MERS

were carried out

Wattmeter

Refrigerator(100W)

Using single-phase induction motor.

The power factor is 0.72.

The voltage applied to the refrigerator is fixed at 100V.

Experimental result

19

Loss of the long wire decreases from 13.9W to 7.2W

57kWh of energy will be saved in a year

About 900yen (= $8) will be saved (in Tokyo)

Required electric capacity is decreased about 30%

without MERS with MERS Power factor

Active power (W)

Apparent power (VA)

Current (A) Rective power (Var)

0.72 110.9

152.6 1.53 104.8

0.96 104.2

108.5 1.12 29.8

20

The power factor correction using MERS was proposed.

Power factor is improved automatically regardless of

load conditions by phase shifting control.

The power factor of single-phase induction motor is

improved by MERS.

PWM control of MERS achieves the power factor

correction without distortion of current waveform.

The distorted current does not decrease efficient of the

motor.

An experiment to demonstrate that the power factor

correction can save energy were carried out.