Biến đổi hình học tô pô bộ biến áp nguồn điện ba pha hiệu quả cao với không gian véc tơ PWM

The Modified High Efficient Three-Phase Voltage Source Inverter Topology with Space Vector Pwm Phan Quae Dzung*, Le Chi Hiep, Nguyen Bao Anh, To Huu Phuc, Nguyen Dinh Tuyen Ho Chi Minh

The Modified High Efficient Three-Phase Voltage Source Inverter Topology

with Space Vector Pwm

Phan Quae Dzung*, Le Chi Hiep, Nguyen Bao Anh, To Huu Phuc, Nguyen Dinh Tuyen

Ho Chi Minh University of Technology

268, Ly Thuong Kiet 10 District Ho Chi Minh City

Received September 03 2013, accepted April 22 2014

Abstract

This paper proposes the modified Space vector PWfA tor the modified topology of high efficient

three-phase voltage source inverter (HE-VSI3) which consists of traditional six switches voltage source inverter and three bidirectional free-wheeling switches for creating the ac decoupling circuit This topology has the advantages such as the ability to improve the efficiency based on the principle of decoupling, the ability of applying to the conventional VSI scheme, the simplicity of the control algorithm and can widely applied to many applications The HE-VSI3 topology and modified space vector PWM method are simulated by using Matlab/Simulink software and implemented in the experimental prototype The high efficiency is obtained very promising in the proposed scheme with modified SVPWf^

Keywords Three-Phase VSI Topology, Space Vector PWM, LCL Filter Galvanic Isolated Transformer

1 Introduction

Con vent ion al'three-phase voltage source

inverter (VSI) is now widely used in industrial and

from dc to ac This scheme is particularly applied in

the electric motor drive systems and renewable

energy systems such as photovoltaic, fuel-cell

conversion systems The recent study on improving

the efficiency of three-phase inverters is based on the

scheme and control method for generating pulse

pattems become more complex and it is difficult to

be implemented for the existmg VSI [1,2],

Recently, many research papers have been

published for single phase VSI scheme for

transformerless grid connected system

The efficiency improvement is based on the

principle of ac or dc decoupling, when the zero state

on the H-bndge with a ac bypass circuit consisting of

a bidirectional switch (HERIC topology) [3] or a

diode rectifier and a switch with clamping to the dc

midpoint (HB-2VR topology) [4], are proposed In

case of dc decoupling cfrcuit, some topologies are

invented, which consists one extra switch (H5

topology) [5] or two extra switches (H6 topology)

[6,7] High conversion efficiency in these schemes is

obtained

In order to mcrease the efficiency, the

researchers usually pay attention to the use of

multi-' Conesponding Author, Tel; (-I-84) 903.657 486

level principles [8,9] This leads to a change in configuration and availability of PWM methods such

as space vector PWM of the we 11-developed three phase two-level inverter

This paper analyses the topology of high efficient three-phase VSI (HE-VSI3), which consists

of six fraditional switches for converting power and three bidirectional free-wheeling switches for creatmg the ac decoupling circuit (Fig I) In this topology, the DC common point is separated from the gnd neutral point or common point of stand-alone three-phase load The modified SVPWM algorithm is developed for this topology

This topology has the advantages such as the ability of improving the efficiency based on the principle of decoupling, the ability of applying to the conventional VSI scheme, the possibility of implementing the Space Vector PWM algorithm So,

it can he applied to many industrial field widely

~-J i

Fig 1 The modified three phase voltage source inverter with ac decoupling circuit (HE-VS13)

Fig 2 The HE-VSI3 with an output LCL fiher

'f-i-f

-iJJSfW' ~

Fig 3 The HE- VSI3 PV Grid-Connected System

This topology can he applied to'

- The application of electrical energy

conversion from DC to AC:

• for providing the ac voltage with variable

frequency and variable effective value to the load

filter (Fig 1)

• for providing the ac voltage with fixed

frequency and effective value to the load (such as

RL) with the output LCL filter for obtaining the tme

sinusoidal wave, (Fig 2)

- Photovoltaic panels three-phase

grid-connected applications with an isolation LV

transformer (Fig 3) Almost the network

configurations are divided mto two groups: with

galvanic isolated fransformer and transformerless

The grid connected configuration with isolated

fransformer has advantages such as safety, no leakage

cunent, and no dc cunent injection In contrast,

fransformerless topology has higher efficiency, but it

has more complex control algorithms and some

related issues such as leakage cunent and dc current

injection into the grid

2 Modified he-vsi topology

2.1 Structure and principle of the High Efficient

VSI3

Modified topology, called the High Efficient

Voltage Source Inverter (HE-VSI3), uses a modified

version of the three-phase bridge VSI, by adding an

ac-decoupling circuit, which composes of three exfra

bidirectional switches as shown in Fig I DC

common point is separated from grid or load common

point and the common point of bidirectional switches

The purpose of the HE-VS13 scheme is the

zero space vector occurs (S1, S3, S5 or S2 S6 are

m on-state in conventional VSI scheme), i lie output current of the modified configuration flow.-, in a path with ac decoupling circuit via three extra fi^ewheeling switches (SSI-SS3) and therefore the

of switches Si-Sft are reduced, i.e increasing the efficiency of inverter

The filter parameter (Table I) is calculated using the method which is shown in [9]

Table 1 Table of designed parameters for Id filter

Scheme Power load,[W]

5000

10000

15000

20000

Filter parameter

Li, |mH|

3.306

1.102 0.863

Lg, | m H | 0.462 0.231

0.116

C, IllFI 3.29

9.87 13.2 Semiconductor losses in voltage source IGBT converters can be calculated using method in [10], The efficiency of the VSI and the modified HE-VSI3 is calculated by the formula:

where Pm is the input dc power, Poui is the output

ac power according to I" voltage harmonic

' o u J " '\RMS IRMS > '

2.2 Modified Space Vector PWM algorithm for the High Efficient VSIS

The space vector modulation is based on the formation of three voltage vectors in sequence in one sampling interval Ts so that the average output voltage meets the requirement The calculations of the switching states in VSI are as follows for /i Ts [11]:

t = — M r s i n i r / 3

- T / 2 - f _ -t^

•R MT sin Q ;

(4) where: t, • duration for vector V„ i^ -duration for vector Vy, 1^ - duration for vector Vi, M - the index

of modulation M = VVV,™ (V" - amplitude of the required voltage vector, V,.„ - peak value of six step voltage)

Fig 4 shows the space vectors ii the modified

The algorithm of modified space vector PWM

is proposed in Fig 5 The switchmg process of

modified algonthm when the zero voltage occurs and

finishes in sector 1 is shown in Fig 6 The difference

is when the zero space vector occurs, in the modified

topology (HE-VS13), all switches SSI, SS2 and SS3

are mm on and all SI, S2, S3, S4, S5 and S6 are frim

off with the inserted blank time (DT! - Dead time

interval) between complementary switches This way,

using SSI - SS3 as shown m Fig.l, the zero-voltage

of the inverter, during which period the DC-lmk is

separated from die load or the grid, because all S1-S6

are turned off

This modified SVPWM is very simple and

easily to implement by using DSP or FPGA

confroller for generating pulse pattems

J Simulation of the modified he-vsi with svpwm

The simulation model is built

Matlab/Simulink with SimPowerSystem Toolbox

3.1 Case study 1: Reference output voltage is

fixed, power load is changeable (for application

such as stand-alone load or grid power system)

The simulation model includes (Fig.7):

- DC link voltage: Vd = 800V

- HE-VSB inverter (Fig.I)

- Filter: LCL type

- Reference output voltage: Vp = 22 QV^s,

fi= 50Hz

- Modified SVPWM : modulation index

M= 0 7881; switchmg frequency fs^v ^ 10 kHz

- Switch parameters: IGBT on-state

resislance=0.02 £1, IGBT forward voltage =2.5 V,

Diode on-state resistance=0.01 Q, Diode forward

voltage-0.8 V

- Load : RL (5 kW, 10 kW, 15 kW, 20 kW)

The simulation results of output phase voltage

and cunent waveform are shown in Fig, 8 Fig, 9

efficiency between VSI and HE-VSI3 versus power

load is presented in Table 4, S.Table 2, 3,

Fig 5 The flowchart of modified Space Vector PWM for HE-VS13

J L

^ T L L

.- i n

I l_

Fig 6 Pulse pattern of SVPWM (a) and Modified

SVPWM (b)

V,<0DI-OIIO) ViflOI-OOO)

Table 2 Table o f simulation re suits fo VSI

VSI

|kW|

5

!0

15

20

Pdc, [W]

6442

11550

16650

21740

Pout,

5037

10060

15070

20070

n

0.78 0.87 0.90 0.92

Id, |A1

8.05 14,43 20.81 27.17

VlHMS

IV]

220-8 220,7

220 5

220 4

THD

|%| 1,03 1-04

1 04

1,04

Fig 7 The simulation model of HE-VSI3 witli tile

modified SVPWM

5

Fig 8 Output voltage and cunent waveform of

HEVSI3 (when Picad = 20kW)

Fig 9 Input, output power (W) and efficiency

Table 3 Table of simulation results for HE-VS13

(Fig 1)

HE-VSI3

Power

[kW|

5

10

15

20

Pdc,

1W|

6008

11140

16280

21410

Pout,

|W]

5082

IOI60

15240

20320

Tl

0.84

0.91

0.93

0.94

Id, |A|

751

13,93

20,35

26.77

VI

221 8

221 8 221,8 221,7

THD

|%J 1-03

I 03

1 03

1 04

;e and

such as 3.2 Case study 2: Reference output v frequency are changeable (for appUcatio induction motor drive)

The simulation model mcludes'

- Load : Pio.d_n,= = 5 kW, Qtod_n,ax = 1 kvar The simuladon resuhs of output phase voltage and cunent waveform are shown in Fig 10, I I The comparison of efficiency between VSI and HE-VSIS versus modulafron index (or base frequency) is presented in Table 4, 5

The output voltage has modified shape and the output cunent has sine shape The efficiency of

HE-The load cunent is m phase with the output

voltages with sinusoidal waveforms (Fig 11) In case

of HE-VS13 topologies, the higher efficiency is

obtained in whole the power load range

The output voltage and current have sine

shape and low THD index Besides, the efficiency of

Fig 10 Output phase voltage waveform of HE-VSI3 (when f= 40Hz, M=0.63)

Fig 11 Output cunent waveform of HE-VSI3 (when

f = 40 Hz, M = 0.63)

Table 4 ^able of simulation results for VSI

VSI

fl, | H z |

10

20

30

40

50

M

0.157 0.315 0.472 0.630 0.788

Pd.,

2140

4462

6657

6636

6440

P ,

1407

3154

4865

5004

5036

1

0.65 0.70 0.73

0.75 0.78

Id,

|A| 8.172 8.509

8 457 8.295 8.049

Vi,

|V| 40.79 86.31 131.2 176,1 220.8

Table 5 Table of simulation results for HE-VS13

HE-VSI3

n,

IHil

10

30

50

M

0.157 0.315

0 472

0.788

Pdc,

|W1

1573

3606

5924

Pout

| W |

1299

3066

4964

1

0.82

0.84

0.83

Id,

|A|

6 01 6.877

7 224 7,405

VI,

|V1

39.29

84 95 130.3

220.2

t Experimental results for he-vsi3 topology

A prototype is used to verify the modified

topology with SVPWM confrol algonthm The

expenmental model (Fig 12) includes:

- DC Source: 130 V

- Confroller: Card FPGA Virtex 5

- VSI and AC Decoupling Circuit 12 IGBTs

FGL60N100

- Dnver' HCPL A3020

- Switching frequency: 10 Hz

- Deadtime duration 2ps

- RL Load: R - 3 3 i l , L = 5mH

Table 6 Table of experimental results for the conventional VSI (Averaged values for 11 measures)

Fig 12 Experimental model of HE-VSI3

Fig 13 Output phase voltage wavefonn of HE-VSI3

TMt J L •Stop M(*K-i60DllH

VSI ToDOloEV

M

0.8

DC Voltage (V) 132.93 Average Temperature CC)

DC Current (A) 5.15

Input Power (W) 685.53

Output Power (W) 633.64

1

(%)

92,43 .lain switches: 62.04 "C Sidirectional switches 28.33 °C

Table 7 Table of experimental results for the HE-VSB (Averaged values for 11 measures)

HE-VSI3 ToDoloEV

M

0,8

DC Voltage

132 74 Average Temperature

rc)

DC Current (A) 5,10

Input Power (W) 676.54

Output Power (W)

628 27

(%)

92.86 vlain switches 55 83 "C Bidirectional switches: 38 33 °C

The experimental results demonsfrale the feasibility of modified HE-VS13 scheme with SVPWM algorithm (Fig 13, 14), The comparison of HE-VS13 IS presented m Table 6, 7 The higher efficiency of HE-VSI topology is obtained

:? Conclusions

The modified topology of high efficient three-phase voltage source inverter (HE-VS13) with Space Vector PWM is presented The HE-VS13 topology consists of conventional six switches two level voltage source inverter and auxiliary three bidirectional switches in order to create the ac decoupling circuit- The modified Space Vector PWM for generating pulse pattems is also shown in details The proposed HE-VS13 topology with modified space vector PWM method is simulated by using Matlab/Siraulmk software and implemented in the experimental prototype The high efficiency is obtained very promising

Acknowledgments This research is funded by Vietnam National University - HCMC University of Technology, Viemam under grant number B2012-20-04TD

Fig, 14 Output phase current waveform of HE-VSI3

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