Description
The ARTEMiS distributed parameters line block implements an Nphases distributed parameters transmission line model optimized for realtime simulation.
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The ARTEMiS Distributed Parameters Line block implements an Nphases distributed parameters line model with lumped losses. The model is based on Bergeron's travelling wave method used by the Electromagnetic Transient Program (EMTP) ^{[1]}. This block is similar to the SPS distributed parameters line block but is optimized for discrete realtime simulation and allows network decoupling. It also allows multiCPU simulation on an RTLAB simulator.
Refer to the SPS Distributed Parameter Line block Reference page for more details on the mathematical model of the distributed parameters line.
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Network Decoupling
One of the main advantages of the ARTEMiS line blocks (Distributed parameters lines and Stublines), by opposition to the SPS lines, is the decoupling of the electric circuit into smaller subnetworks. This important property allows ARTEMiS to simulate, in realtime, circuits with more switching elements.
SPS and ARTEMiS solve electric circuits using the common statespace method. One of the main limitations of this method is related to the switch elements. When an event occurs that changes the topology of the circuit (or changes the state of a switch), SPS and ARTEMiS need to compute a new statespace matrix. This calculation causes unacceptable overhead when simulating a circuit in realtime.
To solve this problem, ARTEMiS stores the statespace matrices of a given set of topologies, normally the steadystate topologies, in cached memory and uses them when necessary without having to recalculate the matrices. However, the number of matrices required to cover all topologies of the system depends on the number of switch elements. When a circuit contains a lot of switch elements, the number of required topologies is high and it is not possible to store all matrices in cached memory because of the size of the matrices.
The decoupling property of the line allows ARTEMiS to divide the statespace system into two different statespace systems and reduce the total size of the statespace matrices in memory. It also reduces the maximum number of topologies by an important factor.
RTLAB Simulation Using a Cluster of PCs
The distributed configuration of RTLAB allows for complex models to be distributed over a cluster of PCs running in parallel. The target nodes in the cluster communicate between each other with low latency protocols such as shared memory, FireWire, SignalWire or InfiniBand, fast enough to provide reliable communication for realtime applications.
However, electrical circuits cannot be easily distributed over a cluster of PCs without changing the dynamic behaviors of the system. The communication delays degrade the computation.
ARTEMiS lines (Distributed Parameters Lines and Stublines) can be used to distribute a circuit over a cluster of PCs. ARTEMiS used the intrinsic delay of the line to split the circuit without affecting the dynamic property of the system. Moreover, SPS and ARTEMiS use physical modelling lines and connectors to model the circuit.
This type of signals cannot be used by RTLAB to communicate signals between subsystems, because the RTLAB opcomm block only supports basic Simulink signals. The only exception to this rule is the ARTEMiS Distributed Parameters Line block and the ARTEMiS Stubline block. RTLAB allows the insertion of a line block at the root level of the block diagram and the connection of the physical modelling ports of the block to the realtime subsystems.
Also, note that the physical modelling signals and ports do not have to pass through the OpComm block. The Example in the Characteristics and Limitations section illustrates how to use the block with RTLAB.
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Table of Contents  


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Table of Contents  



Mask and Parameters
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Simulation mode  Defines the mathematical models of the distributed parameters line used by ARTEMiS and SPS. Here are the available options: 

• SimPowerSystems: When this option is selected the block uses the SPS mathematical model that is not optimized for realtime simulation. • ARTEMiS model: When this option is selected the block uses the ARTEMiS mathematical model that allows fast realtime simulation and that allows network decoupling.  
Number of phases N  Specifies the number of phases, N, of the model. The block dynamically changes according to the number of phases that you specify. When you apply the parameters or close the dialogue box, the number of inputs and outputs is updated. 
Frequency used for RLC specifications  Specifies the frequency used to compute the resistance R, inductance L, and capacitance C matrices of the line model. 
Resistance per unit length  The resistance R per unit length, as an NbyN matrix in ohms/km. For a symmetrical line, you can either specify the NbyN matrix or the sequence parameters. For a twophase or threephase continuously transposed line, you can enter the positive and zerosequence resistances [R1 R0]. For a symmetrical sixphase line you can set the sequence parameters plus the zerosequence mutual resistance [R1 R0 R0m]. For asymmetrical lines, you must specify the complete NbyN resistance matrix. 
Inductance per unit length  The inductance L per unit length, as an NbyN matrix in henries/km (H/km). For a symmetrical line, you can either specify the NbyN matrix or the sequence parameters. For a twophase or threephase continuously transposed line, you can enter the positive and zerosequence inductances [L1 L0]. For a symmetrical sixphase line, you can enter the sequence parameters plus the zerosequence mutual inductance [L1 L0 L0m]. For asymmetrical lines, you must specify the complete NbyN inductance matrix. 
Capacitance per unit length  The capacitance C per unit length, as an NbyN matrix in farads/km (F/km). For a symmetrical line, you can either specify the NbyN matrix or the sequence parameters. For a twophase or threephase continuously transposed line, you can enter the positive and zerosequence capacitances [C1 C0]. For a symmetrical sixphase line you can enter the sequence parameters plus the zerosequence mutual capacitance [C1 C0 C0m]. For asymmetrical lines, you must specify the complete NbyN capacitance matrix. 
Line length  The line length, in km. 
Measurements  Line current and voltage measurement are not working. 
Inputs and Outputs
Inputs
NPhase voltagecurrent signals
Outputs
NPhase delayed voltagecurrent signals.
Characteristics and Limitations
The ARTEMiS distributed parameters line block does not initialize in steadystate so unexpected transients at the beginning of the simulation may occur.
The use of the ARTEMiS Distributed Parameter Line disables the Measurements option of the regular Distributed Parameter Line. Usage of regular voltage measurement blocks is a good alternative.
Direct Feedthrough  No 

Discrete sample time  Yes, defined in the ARTEMiS guide block. 
XHP support  Yes 
Work offline  Yes 
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Example
The example shows how to use the ARTEMiS distributed parameters line to decouple an electrical network into two distinct subnetworks and consequently to optimize the time to simulate the system in realtime. This property also allows ARTEMiS to simulate systems that contain more switching elements and consequently more complex systems.
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Info 

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color  #D3D3D3 

Note: The procedure shown below can also be applied to ARTEMiS Stubline block to decouple subnetworks and optimize realtime simulation. 
Open the SPS demo power_monophaseline model by typing the following command in the command prompt of Matlab: power_monophaseline;
To become familiar with the example, consult the help and perform simulation and check the results. The next steps will modify the demo to use the ARTEMiS solver instead of the normal SPS solver.
Drag an ARTEMiS Guide block from the ARTEMiS library into the model and set it sample time to 50e6 seconds.
Set the SPS PowerGUI block to <Discrete> mode with a sample time equal to ARTEMiS
Change the SPS Distributed Parameter Line line
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to
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an ARTEMiS
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Distributed Parameter Line block by chaning the corresponding option in the ARTEMiS GUIde block:
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The model must be similar to the following figure. Save the model under the following name: power_monophaseline_artemis.mdl.
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Simulate the model and analyze the results. You will see that the results are similar to the original model.
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The next steps will show you how to run the model on a cluster of PCs running RTLAB. The general idea is to benefit from the intrinsic delay of the transmission line to split the model into subnetworks. The mathematical model of the distributed parameters line of ARTEMiS, contrary to the SPS model, allows distribution of the line onto two different CPUs. This property also allows ARTEMiS to simulate systems containing more switching elements and consequently more complex systems.
Select all blocks located in the subnetwork 1 in the figure above and press CtrlG to create a new subsystem.
Move the ARTEMiS block inside the subsystem.
Rename this subsystem to SM_Subnetwork_1. The following figure displays the content of the SS_Subnetwork_1 subsystem.
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Select all blocks located in the subnetwork 2 and press CtrlG to create a new subsystem.
Add an ARTEMiS Guide block inside the subsystem.
Rename this subsystem to SS_Subnetwork_2. The following figure illustrates the content of the SS_Subnetwork_2 subsystem.
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Select the 3 remaining blocks, normally the two scopes blocks and the Mux1 block and press CtrlG to create a new subsystem.
Rename this subsystem to SC_Console.
Add the RTLAB opcomm block between the inports blocks and the content of the subsystem. Don’t forget to set the number of inports of the OpComm blocks to 3. Refer to the RTLAB user guide for more help.
The following figure illustrates the content of the SC_Console subsystem after the modifications described above have been made.
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Modify the solver parameters of the model; select one of the fixedstep solver, like ode3 for example, and change the fixedstep size to 50e6.
Organize the top level blocks according to the following figure. IMPORTANT: the powerGUI block must be at the top level.
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Save your model.
Your model is now ready to be compiled with RTLAB. Refer to the RTLAB User Guide for more help. If you have set the sample times of your model with a variable set in the workspace (ex: Ts), you should set the model initialization function with <Ts=50e6;> in File>Model Properties>Callbacks→InitFcn
Limitations
Usage in RTLAB as task decoupling elements
When used in RTLAB to decouple and separate computational tasks on different cores/CPUs, the following connection restriction are applicable to the ARTEMiS distributed parameters line model:
The ARTEMiS distributed parameters line must be located on the toplevel of the RTLAB compatible Simulink model
Each ARTEMiS distributed parameters line outports can be connected only to SimPowerSystems component located inside the RTLAB toplevel subsystem (names beginning with ’SS’ or ’SM’ prefixes)
No connection between ARTEMiS distributed parameters lines is allowed on the toplevel. If such a connection is required, the ARTEMiS distributed parameters block connection lines must be first routed inside the subsystems individually and the connection between the ARTEMiS distributed parameters line ports can be made inside the subsystem. The following figure shows an example of illegal ARTEMiS DPL connection at the RTLAB toplevel and how to connect the line inside an RTLAB toplevel subsystem.
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References
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