SW for complementary simulations of technical regulations

In the previous blog post we analysed the Technical Supervision Standard (NTS) developed by Red Eléctrica de España and the Association of Electrical Energy Companies (AELEC), which indicates how each of the technical requirements established in the grid connection codes should be evaluated and certified. As a result of this analysis, we highlight the importance of complementary simulations when certifying compliance with some of these technical requirements.

The complementary simulations described in the NTS can be carried out using any electrical simulation program, and the standard does not require the use of a specific software. Furthermore, they are not required to be carried out by an accredited entity. However, the dynamic model of the plant used in the simulations must be validated by an authorised certifier. This plant model shall consist of the dynamic model not only of the electricity generating units (e.g. wind turbines, inverters, etc.) but also of the additional plant components (e.g. plant controller, STATCOM, etc.).

At Norvento we work with different SW packages depending on the specific project, but undoubtedly for the studies required by the NTS the most interesting ones are Power System Simulator for Engineering, by Siemens (PSS/E from now on) and Power Factory, by DIgSILENT. These are probably the most widely used electrical simulation programs, and the ones that we believe to be the most suitable for carrying out simulations such as those required by the NTS. Today we are going to focus on getting to know PSS/E a little better.

Power System Simulator for Engineering (PSS/E)

PSS/E is a SIEMENS software developed since 1972 and has evolved and established itself as one of the world’s leading tools for the analysis and simulation of power transmission systems.

Currently, PSS/E is the standard data and model format used in many countries around the world. In particular, in Spain it is the software used by the System Operator (Red Eléctrica de España), which requires the delivery of dynamic models of the generation plants compatible with PSS/E for those plants that are either going to be connected to the Transmission Grid or have an installed power of more than 10 MW. Therefore, the vast majority of generation module manufacturers (e.g. wind turbines, inverters, etc.) have models in PSS/E format, which facilitates the interchangeability of data and models between different organisations and entities.

PSS/E allows both static and dynamic simulations, so that any of the complementary simulations required in the NTS can be carried out using this simulation program. For this purpose, the dynamic module is required in addition to the basic PSS/E package.

An example of dynamic simulation in PSS/E is shown below, where the reactive power (in blue) and voltage (in green) response of a wind farm has been evaluated in response to variations in the reactive power setpoint of the wind farm (in red).

One of the great advantages of PSS/E is that it allows a high degree of automation of the simulations thanks to the possibility of developing scripts in a programming language as well known as Python. For the Norvento team, this automation is essential as it allows us to carry out multiple simulation cases and launch algorithms to post process the results, all of which contributes to reducing execution times.

Fig 1, for example, has been represented through the PSS/E graphical interface. However, such a figure could also be represented through external Python libraries, such as the matplotlib library, which would reduce execution times.

In future posts we will continue to explore simulation SW and look at a practical example of the additional simulations required to certify a plant’s compliance with grid codes, in order to clarify the studies that a developer will need to submit in order to connect a renewable generation plant to the grid.