Multi-phase Circuits in ATPDraw

Multi-phase Circuits in ATPDraw Hans Kristian Høidalen NTNU, Norway

NTNU-Electric Power Engineering O.S. Bragstadspl. 2F N-7491 Trondheim, Norway +47 73594225/73594279 [email protected]

Abstract - The paper reports extensions in ATPDraw version 5 related to multi-phase circuits funded by the EEUG organization. ATPDraw now supports up 26-phase circuits including Models input/output arrays X[1..26]. An enhanced Connection is developed with user selectable properties (phase, color, and label) for easy coupling between multiple and single-phase circuit parts. The probes are extended to support 26-phases and reading and displaying steady-state values from the lis-file. A models probe is added to directly monitor global Models variables. Up to 21 phase circuits are supported in the LCC module. Other extensions developed over the last year are only briefly listed.

Keywords: GUI, ATPDraw, Version 5, Enhancements, Connections, File formats, Compress.

1

Introduction

3-phase circuits have been supported by ATPDraw since the DOS versions in early 1990’s. To make connections between 3-phase and single phase circuits the Splitter was introduced from the very beginning. The first single-phase node connected to the Splitter will inherit the phase sequence from the Splitter. Thus three different classes of nodes exists • Single phase nodes with no extension. 6 characters name. • Three-phase nodes with extension ‘A’, ‘B’, and ‘C’. 5 characters name. • Single-phase nodes with extension ‘A’, ‘B’, or ‘C’. 5 characters name. This was coded as three node properties: NumPhases, PhaseSeq and Name. Fig. 1 shows how the phase sequence A, B, or C are inherited from the Splitter to its single phase connections. The other end of the single phase components become normal single phase nodes without node extensions. A

No phase extension

ABC SM

C

B

Fig. 1. Using the Splitter.

The Splitter is indeed challenging and results in some very important deviations from the rule “what you see is what you get”. Imagine the following two cases in fig. 2. The example to the left is a single-phase interruption. It really means that the left and right nodes must have a

different name but with phase A and B connected. This situation can not be transferred to the two 3-phase nodes and stored there as NumPhases, PhaseSeq, and Name. A possible solution to this could be to model the 3-phase nodes 3-dimentionally with a unique name for each phase. The example to the right is a transposition. This case can actually in theory be handled using the PhaseSeq property. The phase sequence can be reset to ABC at the rightmost node. However, the phase extension A, B, and C will in this case loose its physical meaning. The common difficulty in these two situations is that it is a group of components (Splitter & Connections) that will influence its neighbours. As a consequence of these difficulties Connections between Splitters was just simply forbidden. The exception is the degenerated . It will naturally be possible (and legal) to replace the connections with small case resistors or switches in fig. 2.

n1A n1B n1C

n2A n2B n2C

n2A n2B n3C

n4A n4B n4C

n1A n1B n1C

n2A n2B n2C

n2B n2C n2A

n3A? n3B? n3C?

Fig. 2. Example of challenging (and illegal) Splitter Connections.

A special problem is the node naming. If the user attempt to give the name ENDA to one of the nodes on the single phase side of the SPLITTER it is interpreted as a 3-phase name and another A is added at the end producing node names ENDAA, ENDAB, and ENDAC. Very soon it became required to introduce Transposition components instead of using switches and Splitters to control the phase sequence. Transposition components have the benefit that a single component is involved rather than as group as shown in fig. 2. The first approach was to change the phase sequence only locally as shown in fig. 3. This will ensure a correct transposition, but the extension A, B, and C will still loose its physical meaning.

U

A B C

A B C B C A

A B C

A B C

Fig. 3. The first attempt to introduce Transpositions.

The natural extension was to actually perform the transposition throughout the circuit. This may seem like a small change, but it really implies that a node will receive its properties not only from its neighbours but from the entire circuit. The input and output nodes of a component must be defined. The solution was to add another property to the node: Circuit. This property was fixed in the definition of each component (in the support file). The nodes with the same Circuit in a component will get the same PhaseSeq. For instance a 6-phase RL coupled line should have the same Circuit assigned to the two upper nodes and a different one to the two lower, as shown in fig. 4a. Fig. 4b shows the consequence of Transpositions in the present ATPDraw version, where the phase sequence is inherited throughout the circuit.

B C A

U

C

None A

B

Fig. 4. Final handling of Transpositions and Splitters.

The last step in multi-phase circuits was to support 3-phase nodes also for MODELS. Inside the Model, 3-phase nodes must be declared as arrays [1..3]. An example exa_8m3.adp is distributed with ATPDraw as shown in fig.5.

CRZ2 CR50

CRZ2

CRZ1

CR50

CR20 CR01

CR30

SRC2 RAVB

GRCB

GAPA

GAPB

CR20 CR01 CR25

CR25 SRC1 U

CRZ1

CR30

U

SRC1

SRC2 RAVB

U

GRCB

U

GAPC

Fig. 5a) EXA_8.ADP. 3 single phase models (FLASH_1) control 3 TACS switches.

Fig. 5b) EXA_8m3.ADP. A 3-phase model (FLASH_3) controls 3 TACS switches in a group.

The procedure in ATPDraw that identifies the circuit and assign the node Name and Phase Sequence is called CompileCircuit. This procedure is the very complicated and quite risky to modify as it will affect the performance of all circuits.

2

The extended node

A node is an element of a circuit component or a connection. The node has the main properties Name, NumPhases, PhaseSeq, and Circuit. NumPhases could in previous versions only take the values 1 or 3, but in the new ATPDraw version all values between 1 and 26 are supported representing the node name extensions ‘A’ to ‘Z’. PhaseSeq was 0 for pure single phase nodes and a code representing the transposition sequence for 3-phase nodes. In the new ATPDraw version the 3-phase coding is kept and PhaseSeq is equal to 255 for 2 and 4-26 phase nodes. For single phase nodes PhaseSeq is equal to the actual phase number and 0 for pure single phase nodes. In the single phase case PhaseSeq actually represents the node name extensions ‘A’ to ‘Z’, with a value 0 resulting in no node extension. For pure single phase nodes the node name can take 6 characters otherwise 5. The user specified node names should not start by the character ‘X’, ‘Y’, or ‘Z’. The name identifying the node (PN, IN2, and UA[1] in fig. 6) can now be up to 12 characters (increased from 6) and this is consequently the new limit of variable names in MODELS as well.

Fig. 6 Node data dialogs. Drop-Down boxes added in replacement of the parameter Kind. Ground symbol rotation added for component nodes.

3

The extended Connection

The introduction of Transposition objects together with Splitters was challenging and several problems have been identified and corrected over the years. A general problem during debugging is that the sequence the circuit is put together in could affect the end result. One key question is: Should the phase sequence be inherited from the 3-phase to the single phase side of Splitters? The answer in ATPDraw is Yes primarily since the Splitter could be used also as a collector in the configuration. This type of configuration is really superfluous and could really be replaced by the following layout: Now the question becomes: Isn’t it more appropriate to connect a component to phase A rather than to the left or top phase? If this is true the Transposition across Splitters should be avoided and this is also much simpler to program in the CompileCircuit procedure. There is now way back however. Backward compatibility is essential. Transposition will take place across Splitters. The consequence of the above consideration was to extend the properties of the Connection similar to the extended node properties. The following rule is formed for the general class Connection: The property NumPhases is just equal to the number of phases carried by the connection (1..26). The property PhaseSeq is for a single phase connection equal to 0..26 (phase carried, 0: for single phase connections), for a 3-phase connection a code for the phase sequence ABC, and for an n-phase (2, 4-26) connection the value 255. Transposition will NOT take place across connections when NumPhases3 unless a Splitter is involved. Also PhaseSeq will not be automatically inherited along a chain of connections, but the Connection's properties will be inherited in the drawing process. This results in one backward compatibility problem. In earlier ATPDraw version it was legal (but no recommended) to connect a single phase connection to a three-phase node. This was automatically interpreted as a connection to the upper phase (A if no transpositions had occurred). With the new connection concept this is no longer obvious. This point probably needs further attention. One important thing remains. How can ATPDraw visualize the phase carried by the connection? The solution to this is to allow user selectable colors for the connections and to draw a connection label on the screen. The dialog box for connections is shown in fig. 7 (appears after a double click on a connection or during the drawing process).

Fig. 7. The Connection dialog box.

Fig. 8 illustrates the various options for (3-phase in this case) multiphase circuits in ATPDraw. The flag DEF is set at the source node to the left and this means that all connections marked with 1 will carry the phase D and so on. The color of the connections is user selectable as shown in Fig. 7, but as default the color and phase sequence are inherited when the user clicks on one to connection to draw a new one. It is now possible to click on the middle of a vertical/horizontal connection to draw a new connection. Selection of connections is performed by click and hold. The Connection label is moveable and on-screen editable. D

1

U D E F

E F D

1 3 E F D

F

E

D

E

D F

E

2

Fig. 8. Illustration of various phase options in ATPDraw.

4

The extended probe

The probe components have been extended to handle multi-phase nodes as shown to the left of each dialogs in fig. 9 The user has full control of the phases 1..26 to monitor. A new Model probe has been introduced than can monitor input/outputs to Models directly without the manual RECORD specification. The voltage and current probes also has the option to record and visualize the steady-state voltage, current and power by reading the lis-file (only phase A for multiphase probes). The probe dialog also contains options for pu/rms scaling of the steady-state quantities. Fig. 10 shows an example of the steady-state screen plotting. The current probe has an Add current node button. When checked this will actually give two measuring switches in series and a node connected to the mid-point. This node can be used as input to TACS/Models without uncertainty of which current actually measured.

Fig. 9 The new Probe Data Dialog (voltage left, current right). 298.L 2.91

159.9L172.6

-285.+j159.9

BCT

I

Y

Y

I

I

T1 -302.+j251.8 1

+

I

203.9L-169. I

159.9L172.6

+

+

I

I +

I

I

-1.E3+j8.125 -1.E3-j243.7

-1.E3-j1085. I

+

+

T2

BCT Y

Y

I

T1

BCT

Y

Y

MOV

3.617+j0.361

I

I

1.129+j0.119

Fig. 10 Screen plots of steady-state values scaled to 3-phase rms values.

5

From 3-phase to n-phase

With the new generalized Connection component general n-phase circuits can be supported, but only 3-phase nodes will be transposed. The number of phases is, however, limited to 26 due to the node name extension A..Z. What is the benefit of a 26-phase circuit? First of all this is important for MODELS and GROUPS. An n-phase connection could also be useful just to clear up the circuit drawing. As an initial example a 6-phase connection is shown in Fig. 11 for communication between a 6-pulse thyristor bridge and its control circuit. This will make the drawing much easier to read. This example is also used later on to show how the thyristor bridge and the control circuit could be split in two parts. POS1 1

3

5

4

6

2

Freq

Freq

Angle 180 4

6

2 1

2

3

4

5

6

Fig. 11. Communicating a 6-phase signal between a thyristor bridge and its control circuit.

The 26-phase node support also MODEL variables X[1..26] and this allows much more signals to be communicated with a model than the previous 3-phase nodes. A typical example could be a model that calculates and output the harmonics of a signal by DFT as shown in

Fig. 12 (added in Example 14 in the ATPDraw distribution). The current in phase A on the high voltage side is sent as input to a recursive Fourier model and some harmonics (1, 5, 7, 11, and 13 etc.) are recorded in this case. The example in Fig. 12 could also to some extent have been handled in previous ATPDraw versions as well, but the harmonics would then only be available as internal variables. Using the RECORD option would made it possible to plot the result, but the harmonics could not be send as outputs and communicated with other models or the circuit. M MODEL fourier

IMP

1

V

I

V

I Y

2000

Y

POS1

SAT

VS

V

I

I

U

1500 1000

I

+

v -

500 0

I

POS2

I Y

-500

V -1000

SAT

-1500 -2000 0.00

0.04

(f ile Exa_6g.pl4; x-v ar t) c:VSA

0.08 -VDA

m:X0092A

st

0.12

0.16

[s]

0.20

m:X0092K

th

Fig. 12. Utilizing the multi-phase feature to obtain harmonics of a current (1 and 11 shown in figure).

The multi-phase node and connection could also be useful to communicate more nodes to and from a GROUP. If the GROUP has a component with an n-phase node, this node could be set as an external connection point. A connection (bus) could not be specified as an external node however. To overcome this limitation a new dummy component called COLLECT ( ) is created. This component has no data and just a single 26-phase node. The actual number of phases in use is not set in for this component, but the NumPhases for Connections to it could optionally be changed. Figures 13 and 14 show an example where the thyristor bridge with control in Fig. 11 is split in two more general parts; One for the Thyristor Bridge and one for the Control. This will allow more general building blocks for future use.

4

1

3

5

4

6

2

6

2

Fig. 13. Creating a GROUP out of the Thyristor Bridge.

Freq

Freq

Angle 180

1

2

3

4

5

6

Fig. 14. Creating a GROUP out of the Control.

Putting these two GROUPS together is just straight forward as shown in Fig 15. Since the CONNECT nodes are 26-phase the Connection between will also be 26-phase by default, but this could optionally be changed to 6. The circuit in fig. 15 looks more complicated than when the Thyristor Bridge and Control are embedded in the same GROUP. The flexibility is, however, increased and more user control is given to for instance the synchronization (zero crossing detection).

1

3

26 phase connection Optionally change to 6

U

Fig. 15. Creating a Thyristor Rectifier from the two GROUPS in Figs. 13 and 14.

6

Conclusion

The support of 26-phase nodes adds substantial more flexibility and capacity to ATPDraw. The Connection object is generalized with user control of the number of phases, the actual phase carried by a single phase connection, and the color. This results in improved readability of the circuit drawing and enables communication of multi-phase signals from MODELS and GROUPS. The funny thing is that the new Connection is easier to handle than the Splitter since the complications of Transposition are avoided. Support of the combination of the new Connection and the old Splitter is complicated, however. In a lot of situations when a single phase circuit is connected to a 3-phase node the extended Connection can replace the usage of a Splitter. Extended probes have been developed.

Appendix Other updates in ATPDraw 5.0 Vector graphics This is the second part of an EEUG sponsored project already completed. • All components can have a vector icon or a bitmap icon (but not both). A bitmap icon has the size of 41x41 with 8 bit color depth. The vector icon can consists of up to 93 elements

• • • • •

(line, rectangle, ellipse, poly-line, arc, Bezier curve, or 8 char. text) within a 255x255 frame and with up to 256 colors. Each element is associated with a property Tag that is used to turn on/off elements dynamically. This is extensively implemented for RLC components, sources, time control switch, LCC, transformers, and universal machines. Most standard components (~200) have already got a vector icon in the file ATPDraw.scl. For backward compatibility reasons the new vector icons have about the same size as the old bitmap icons (the node positions must be the same). The vector icons are individually scaleable (x2, x3 etc.) and Flipping (left to right) is supported. Vector graphics enables better zooming capabilities and as mentioned better dynamics. A new routine for automatic icon creation for Groups and Models that supports up to 32 nodes is implemented. Individual icon size set for each components and this restricts the selective rectangle around components and reduces the object overlap conflicts. Individual specification of the branch output request symbol position.

New file formats, recompress, and undo/redo This is a BPA sponsored project running in parallel and implies new format of project and support files with backward compatibility and some other enhancements. • The maximum component size is increased to 64 data and 32 nodes. The length of data and nodes ID names is increased to 12 characters (useful for Models). A Unit string (12 char.) is added to all data parameters. The node positions are changed from the predefined border positions 1-12 to relative x-y positions (-120, -110, … -10, 0, 10, … 110, 120). • The support-file is used only when a component is created. All the properties of the Support-file (called Definitions) are now included in the component. The support files are no longer included in the project file. Some components like Groups and Models (based on mod-files) are not associated with a support-file at all, since they are entirely created in-memory. The the Component dialog box (standard input) ATPDraw offers to edit the definitions of each component locally. • The "external" data associated with the components Models (mod-file), User specified (lib-file), Transformers (bct/xfm-files), Lines/Cables (alc-file) etc. are no longer stored in global files but are stored internally for each component. Consequently no components share data any more and no file conflicts arise between projects. A drawback is the case of several equal LCC/BCTRAN objects in a file which now can require multiple superfluous ATP executions. • When a project is opened no files are copied to disk (but instead to internal memory strings). Consequently the warning "File on disk is older than…" are completely removed. The only exception is lib-files for $Include which must be stored on disk. • The user is asked to specify a Result Directory when opening a project and all results (ATP-file and lib-files) are stored in this directory. This enables easy transmission of the ATP results for further processing outside ATPDraw. • The user can also add local help texts to all components. • The project file now follows the PKZIP 2 standard. New compression/decompression routines are implemented. • •

Undo/Redo is updated to handle screen texts and editing of "external data". Regrouping of GROUP components supported. Select a group and click on Edit|Compress. The group content is always centred in the circuit window when viewed.

• • • • • •

Some gridsnap bugs related to connections (in particular with rubber bands on) corrected. The Hybrid Transformer component XFMR is updated to handle open circuit test reports at any winding (the low-voltage winding does not have to be the innermost). Toolbar modified since Recent Components vector graphic icons do not fit in the 41x41 buttons any more. Zooming and Node dot size combo boxes added to the toolbar. Red node dots indicate User named node. TACS input signs: red=pos, blue=neg. Copy/Paste data grid buttons added. Possible to paste in data via the clipboard. Type 1 source added.

Fig. 16 ATPDraw version 5 with all standard components in Vector Graphic style.