Application - 12-pulse parallel connection with decoupled...

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SINAMICS DCM

DC converter Application - 12-pulse parallel connection with decoupled interphase transformer Application Manual

05/2017 A5E34871844AQ/RS-AA/001

Introduction 1

Description of the application 2

Commissioning 3

Dimensioning example 4

Symbols 5

Literature 6

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Siemens AG Division Process Industries and Drives Postfach 48 48 90026 NÜRNBERG GERMANY

A5E34871844AQ/RS-AA/001 Ⓟ 08/2017 Subject to change

Copyright © Siemens AG 2017. All rights reserved

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Application - 12-pulse parallel connection with decoupled interphase transformer Application Manual, 05/2017, A5E34871844AQ/RS-AA/001 5

Table of contents

1 Introduction ............................................................................................................................................. 7

1.1 Important note ........................................................................................................................... 7

1.2 Preliminary remarks .................................................................................................................. 7

2 Description of the application .................................................................................................................. 9

2.1 Infeed transformer ................................................................................................................... 11

2.2 Converters .............................................................................................................................. 11

2.3 Interface transformer ............................................................................................................... 11

2.4 Current transformer ................................................................................................................. 12

2.5 Drive motor/load ...................................................................................................................... 12

2.6 Actual value sensing of the load voltage ................................................................................ 12

3 Commissioning ..................................................................................................................................... 13

3.1 Current control optimization .................................................................................................... 13

3.2 Test ......................................................................................................................................... 13

4 Dimensioning example .......................................................................................................................... 15

5 Symbols ................................................................................................................................................ 17

6 Literature .............................................................................................................................................. 19

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Table of contents

Application - 12-pulse parallel connection with decoupled interphase transformer 6 Application Manual, 05/2017, A5E34871844AQ/RS-AA/001


Introduction 1 1.1 Important note

The application is provided are not binding and do not claim to be complete regarding configuration, parameterization or any eventuality which may arise. The dimensioning example does not represent a customer-specific solution and is only intended to provide assistance with typical applications. The company operating the system is responsible for the correct operation of the dimensioned systems.

SIEMENS reserves the right to make changes and revisions to this document at any time without prior notice. If there are any differences between the suggestions made in this document and other Siemens publications, such as catalogs, the contents of the other document(s) take priority.

1.2 Preliminary remarks The 12-pulse converter circuit with interphase transformer is suitable for applications where solutions based on individual reactors are not feasible.

The interface transformer acts to compensate the current in the direction of the load; as a consequence, when using an ideal interface transformer, the load current is hardly smoothed at all.

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Introduction 1.2 Preliminary remarks



Description of the application 2

The basis for the application with interphase transformer should be taken from application document "12-pulse applications 09/2015", Reference [1]. This defines the basic interconnection and parameterization. When dimensioning the individual components, the notes provided in this Chapter as well as in Chapter 4 (Page 15) should be observed.

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Description of the application


Figure 2-1 Overview of the armature circuit with relevant signals

Legend Position Element 1 Supply transformer (see Chapter 2.1) 2 Converter (see Chapter 2.2) 3 Converter (see Chapter 2.2) 4 Interphase transformer (see Chapter 2.3) 5 Current transformer (see Chapter 2.4). 6 Drive motor / load (see Chapter 2.5). 7 Setpoint channel 8 Parallel connection interface 9 Actual load voltage 10 Actual load current 11 Actual value sensing, load voltage

Description of the application 2.1 Infeed transformer


2.1 Infeed transformer ● 3-winding transformer or a group comprising 2 transformers.

● Phase of the secondary voltage shifted through 30° el. - possible vector groups are Dd0y11, Dd0y5, Yy0d11, Yy0d5.

● Identical nominal secondary voltages

● Short-circuit voltage, primary-secondary uK1-2 and uK1-3 should be at least 4 %. Not complying with this requirement can be compensated by installing commutating reactors between the transformer and the individual converters, according to the engineering specifications [2]. The short-circuit voltage - taking into account the reactance of any commutation reactors - should not exceed 12%, referred to the rated converter current.

● As far as possible, the same short-circuit voltage, primary-secondary for both secondary sides, uK1-2 and uK1-3. Deviations of up to 10% with reference to the particular values are permissible (e.g. maximum deviation uK1-2 = 3.6 % and uK1-3 = 4.4 %).

● The minimum short-circuit voltage between secondary windings uK2-3 should be higher than 10 %. A lower level of decoupling between the two systems could result in instability in the current distribution between the two system halves.

2.2 Converters These converters belong to the SINAMICS DCM series of devices. The application document involves typical applications for the selected devices; essentially, all SINAMICS DCM devices can be used.

2.3 Interface transformer The interface transformer is implemented as single-phase transformer.

● Ratio 1:1

● Frequency = 600% line frequency (300Hz at 50Hz system, 360Hz at 60Hz system)

● The no-load current I0 should be 5-12% of the rated current. The value of the no-load current is to be achieved using the air gap in the interphase transformer core.

● The primary/secondary voltage is the U1_N = U2_N - is 0.65 times the line to line voltage of the secondary side of the infeed transformer.

● The rated thermal currents I1_N = I2_N of the windings correspond to half the DC output current of the system.

● The nominal power rating of interphase transformer SN* is ≥ 0.12x the nominal power rating of the current transformer.

● The short-circuit voltage uK of the interphase transformer should, as a minimum, be 10% - when considered as a transformer. A higher short-circuit voltage results in better current smoothing - and increases the line harmonics.

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Description of the application 2.4 Current transformer


In addition to increasing the no-load current, the air gap in the interphase transformer also results in achieving a lower sensitivity of the interphase transformer with respect to saturation effects when both converters are operating unbalanced. Reducing - or even eliminating - the air gap in the interphase transformer core reduces the no-load current, and therefore increases the effect of the interphase transformer when it comes to improving the system line harmonics. However, it should be noted that reducing the airgap increases the sensitivity of the interphase transformer regarding saturation. If the no-load current of the interphase transformer is to lie below 10%, for each % (percentage point) below 10%, the nominal power rating should be increased by a factor of 1.1.

The precise dimensioning of the short-circuit voltage uK (or leakage inductance) and the no-load current (or magnetizing inductance) of the interphase transformer depends on the specific application. In addition, additional data is required, for example load inductance, permissible current ripple, control dynamic response required etc. The requirements relating to permissible line harmonics (current and voltage harmonics) as well as the existing harmonic line distortion of other possible loads should also be clearly specified.

Based on this data, a precise numerical transient simulation can be performed to determine the dispersion parameters of the interphase transformer. If, as a result of the simulation, leakage inductance variables (or short-circuit voltage uK) are obtained that cannot be implemented in practice, then the system is not suitable for the use of an interphase transformer. In this case, the better solution is to equip each converter with individual reactors.

2.4 Current transformer We recommend that a suitable current transformer is used at the output to sense the current actual value. The current actual value should be connected to one of the analog inputs of the CUD provided for the purpose, see FP6850, FP2085, FP2090 as well as parameters p81852, p81853 (master and slave) according to the List Manual [3].

2.5 Drive motor/load The criteria listed are applicable for motor and/or resistive-inductive loads - including a counter voltage - with either no non linearity, or just a small amount of non linearity. A precise numerical simulation of the system is required if the system is to be designed/dimensioned for loads that are strongly non linear - or for capacitive loads.

2.6 Actual value sensing of the load voltage Sensing the actual voltage using a suitable voltage transformer (PT) at the load is necessary to achieve stability in operation, if the electromotoric voltage is parameterized as input variable of the precontrol. The voltage actual value should be connected to AI2 of the CUD (master and slave); the appropriate parameters must be assigned during the commissioning phase. See List Manual [3], function diagram FP6902, p51854, p51855.


Commissioning 3

The system response depends on many parameters; it is not possible to draw up a parameter set that is generally applicable. As a consequence, it is absolutely essential that an experienced technician manually post-optimizes the current controller.

3.1 Current control optimization The current controller must be optimized according to the document 12-pulse applications 09/2015 [1] Chapter 3.3.4.2.

3.2 Test The notes and information provided in this document are recommendations. These are based on experience, state-of-the-art technology and numerical simulation. It must be carefully verified that dimensioning and parameterizing are correct. This must be performed in test operation, at the latest during the commissioning phase.

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Commissioning 3.2 Test



Dimensioning example 4

A motor with the following key data is involved:

● UN = 600 V

● IN = 4000 A

After assessing the drive dynamic performance, line harmonics and other parameters, a decision was made to use a 12-pulse parallel circuit with the following data:

● U2N = 575 V

● 2x SINAMICS DCM converters, 4Q 575 V / 2800 A

The infeed transformer is selected with the following key data:

● Transformer nominal power rating: SNT = U2N * 3*√2 / π * IN * 1.05 = 575 * 3*√2 / π * 4000 A * 1.05 SNT = 3.26 MVA

● U1 = according to the system supply point (point of connection)

● U2 = U3 = 575V

● Dd0y11 vector group

● uK1-2 = 5%

● uK1-3 = 5%

● uK2-3 = 15%

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Dimensioning example


The interphase transformer is defined as transformer:

● fN = 300Hz (6 × 50 Hz)

● Interphase transformer nominal power rating: SNIT = 0.12 * 3.26 MVA = 195.6 kVA

● U1 = 0.65 * 575V = 380V

● U2 = U1 = 380V

● I0 = 10% * 195.6 kVA/380 V = 51.5 A

● Thermal current of the winding I1 = 2000A

● Thermal current of the winding I2 = 2000A

● Short-circuit voltage of the interphase transformer uK = 15%

This interphase transformer has an effective inductance per phase:

The inductance values listed above can be measured between connections 1-3 or 2-3

The interface transformer described in the example mainly compensates the current in the direction of the load; as a consequence, when using this interphase transformer, the load current is hardly smoothed at all.


Symbols 5Symbol Explanation U1N, U2N Nominal primary/secondary voltage of the transformer I1N, I2N Nominal primary/secondary voltage of the transformer I0 Transformer no-load current uK1-2 Short-circuit voltage, secondary winding 2 with respect to the primary winding uK1-3 Short-circuit voltage, secondary winding 3 with respect to the primary winding uK2-3 Short-circuit voltage, secondary winding 2 with respect to secondary winding 3 uK Short-circuit voltage of the interphase transformer SNIT Nominal power rating of the interphase transformer, for dimensioning the inter-

phase transformer, the nominal power rating with nominal core induction is considered.

U1, U2 Rated voltages of the interphase transformer windings I1, I2 Rated currents of the interphase transformer windings SNT Type rating of the converter transformer

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Symbols



Literature 6[1] Siemens AG; 12-pulse applications 09/2015; A5E34871844G

[2] Siemens AG; SINAMICS DCM, commutating reactors, operating instructions 2013; A5E32621741A

[3] Siemens AG; SINAMICS DCM List Manual, 6RX1800-0ED00

[4] Schäfer,J: Rectifier Circuits: Theory and Design, John Wiley&Sons Inc. USA, 1965; CatNo. 65-12703

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Literature


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Siemens AGDivision Process Industries and DrivesPostfach 48 4890026 NÜRNBERG德国

本公司保留更改的权利6RX1800-0AD27© Siemens AG 2009-2015

Сименс АОDivision Process Industries and DrivesPostfach 48 4890026 NÜRNBERGГЕРМАНИЯ

Возможны изменения 6RX1800-0AD56© Siemens AG 2009-2015

Siemens AGDivision Process Industries and DrivesPostfach 48 4890026 NÜRNBERGALEMANIA

Sujeto a cambios sin previo aviso6RX1800-0AD78© Siemens AG 2009-2015

Siemens AGDivision Process Industries and DrivesPostfach 48 4890026 NÜRNBERGGERMANIA

Con riserva di modifiche6RX1800-0AD72© Siemens AG 2009-2015

Siemens AGDivision Process Industries and DrivesPostfach 48 4890026 NÜRNBERGALLEMAGNE

Sous réserve de modifications techniques.6RX1800-0AD77© Siemens AG 2009-2015

Siemens AGDivision Process Industries and Drives Postfach 48 4890026 NUREMBERGGERMANY

Subject to changeA5E34871844AQ© Siemens AG 2017

Siemens AGDivision Process Industries and DrivesPostfach 48 4890026 NÜRNBERGDEUTSCHLAND

Änderungen vorbehalten6RX1800-0AD00© Siemens AG 2009-2015

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