Embedding breakers into the SSN induction machine

One of the optimisation contraint of an SSN model is the number of switches per SSN group. User will want this number of switch per SSN group to be below 12 typically. If not, some additional SSN group have to be creates, possibly increasing the number of SSN node and simulation time-step.

One optimisation that can be made in this regard is to embed switches or breakers into an existing device like the SSN Induction machine (SSN-IM).

Image 1. Comparison of two models: SSN-IM with embedded breaker (top), standard SSN-IM (bottom)

In Image 1, we have compare the standard SSN-IM with the one with embedded breakers. The impact is that the SSN group connected with the SSN-IM with embedded breaker has less switches, because it was 'transfered' inside the SSN-IM.
The effect of this is that the user can add 3 more switches into the SSN group left of the SSN-IM without negative impact on performance.

Methodology

The SSN-IM uses a stator fixed reference frame D-Q transform internally.  What was done here is that we added the breakers resistance in series with the stator resistance inside the D-Q transform. The breaker resistances (3 resistances) are transformed into the D-Q frame with P*Rbrk*Ptr, where P is the fixed-referecne frame D-Q matrix. (Ptr is the transposed of P) and Rbrk is the vector 3 breaker resistance vector.

The methodology is quite simple and efficient numerically.

By comparison, if we were to apply this technique to Distributed Parameter Line (DPL) model, the approach could be less effective because DPL have an impedance that is reference to ground and computing the model+breaker equivalent impedance can require some inverse computation.

Availability

This SSN-IM with embedded breaker model will be available in early 2020 in the next release of ARTEMiS. 

Introduction

This blog objective is to disseminate information of the ARTEMiS blockset for SimPowerSystems-Simulink and the SSN solver.

In this highly specialized blog, I will post things such as:
- New ARTEMiS and SSN models
- Tricks and Expert techniques for real-time simulation of power systems.

Some definitions first.

ARTEMiS: Advanced Real-Time Electro-Magnetic Solver. (That' s why the 'i' is not capitalized!) It's a tool to make real-time simulation of power systems, which includes different models and solvers such as SSN.

SSN: State-Space-Nodal. This is an equation solver for power systems. At the core, it uses a nodal admittance method similar to EMTP. The main difference is that all electric branches are formulated using a state-space approach and are user-defined (as opposed to Hypersim and EMTP which provide a fixed set of electric branches and elements).

References:

C. Dufour, J. Mahseredjian,  J. Bélanger, J. L. Naredo, “An Advanced Real-Time Electro-Magnetic Simulator for Power Systems with a Simultaneous State-Space Nodal Solver”,  IEEE/PES T&D 2010 - Latin America, São Paulo, Brazil, Nov. 8-10, 2010

C. Dufour, J. Mahseredjian , J. Bélanger, “A Combined State-Space Nodal Method for the Simulation of Power System Transients”, IEEE Transactions on Power Delivery, Vol. 26, no. 2, April 2011 (ISSN 0885-8977), pp. 928-935