Object Oriented Network Modelling

This chapter presents the object oriented Deep-Editor model, showing the class family and its relationship with network editors. Figure 3 illustrates the hierarchical class tree of the DeepEdit model.

Figure 3. Object Definition and Inheritance in DeepEdit

Using the object-oriented structure in Figure 3, the model implements analysis tools such as: power flows, short circuit calculations, economic load dispatch, among others. The calculation tools in turn make a set of objects that can communicate with physical network, market, and hydro objects and with each other, to obtain the information required by the different algorithms. Figure 4 illustrates the general structure of calculation objects or analysis tools.

Figure 4. Analysis tool objects structure of DeepEdit

All objects that represent network elements have fields or attributes in which their main characteristics are defined. The main fields used in the annual scope pricing tools are:

• Operational (technical) information.

• Economic information.

There are other fields such as Graphic Information and Location Information, the latter is used for a Geographical Information System incorporated in DeepEdit. In the case of the generators, both the operation information and the economic information are used. The following operational data are used by the power flow calculations:

• Nominal Voltage: nominal voltage at which the generator delivers its power.

• Output limit: maximum apparent power that the generator can deliver.

• Sn: nominal apparent power of the generator.

• St: generator statism, for frequency regulation studies.

• Pmin and Qmin: It is the minimum active and reactive power network injections.

• Pmax and Qmax: It is the maximum active and reactive power network injections.

• P (sun): value of active power that the generator is delivering to the system.

• Q (sun): value of reactive power that the generator is delivering to the system.

• lf_type: type of generator in relation to the problem of power flows.

• DF: default value.

• PQ: fixed P and Q.

• PV: fixed P and V.

• SL: P and Q variables (slack).

• VD: voltage dependent.

• lf_type_s: type of generator, result of a simulation, in relation to the problem of power flows.

• Us: voltage setpoint, in the case of generator type PV, SL or DF when applicable.

The economic attributes of interest for an optimal dispatch are:

• Alpha: Corresponds to the fixed cost of the quadratic cost curve in the active power of the generator in question.

• Beta: Corresponds to the linear weight of the active power in the cost function of the generator.

• Gamma: Corresponds to the quadratic weight of the active power in the cost function of the generator.

Figure 5 shows the graphical interface that the editor offers to set the operation information for the generators when building a network to be evaluated by a power flow. Figure 6 shows the interface for economic information.

Figure 5. Generators operational information

Figure 6. Generators economic information

The following figures show the editor’s graphic interface for network elements (transformers and transmission lines).

Figure 7. Transmission lines operational information

• Nominal Voltage: nominal voltage of the line.

• Output limit: maximum apparent power that can circulate through the line.

• Security Coefficient: percentage of availability.

• Resistance: π-model series resistance.

• Reactance: π-model series reactance.

• Capacity: π-model capacitance of the parallel capacitor (shunt).

• S. resistance: π-model conductance of the parallel resistance (shunt).

• Length: Length of the transmission line.

• Sn: nominal apparent power of the line.

Figure 8. Transformers operational information

Power transformers are represented by their equivalent model π. In the case of transformers, the tap (real) modeling shown in the following figure is performed.

Figure 9. Equivalent network model

The admittance matrix is determined by the following equation:

DeepEdit assumes the possibility of defining and change the TAP position using the Zusatsspg parameters: L (maximum voltage additional series in percentage), max tap (maximum number of positions of the TAP, positive integer value) and soll tap. (specified position of the tap, positive or negative integer value less than or equal to max tap in absolute value). Thus, the relationship between these parameters and the value of t is determined by:

The parameters of the π-model are calculated from the short circuit and open circuit tests of the power transformer (usually defined by manufacturer). Since this information is usually not available, in DeepEdit, under the “Parameters in pu” tab it is possible to incorporate the values in PU of the PI model directly. This would only require to previously define parameters un1, un2, ur1, ur2 and smax. In general, the values of uri are generally identical to the uni, in the sense that the nominal operational values usually coincide with the nominal values of the manufacturer.