The increasing penetration of wind and solar generation necessitates efficient and reliable grid connection processes. A critical aspect of this process is the thorough testing and approval of the RMS and EMT models, which are typically developed by wind farm or solar park developers, often with the support of consultants. This paper presents the Model Test Bench (MTB), https://github.com/Energinet-SimTools/MTB, toolbox, an innovative open-source solution developed by Energinet, https://en.energinet.dk/, (the Danish TSO) in Python to significantly expedite the testing of these essential models for grid code compliance.

The MTB toolbox automates the execution of a suite of test cases and currently supports DIgSILENT PowerFactory for RMS models and PSCAD/EMTDC for EMT models. This automation reduces the manual effort and potential for inconsistencies associated with traditional testing procedures. The paper will provide a brief overview of the MTB toolbox's usage, illustrating how skilled engineers can leverage its capabilities to perform comprehensive set of test cases for grid code compliance assessments.

This paper will present several test cases demonstrating how the MTB facilitates the evaluation of adherence to the European Network Code (EU) 2016/631 on Requirements for grid connection of Generators (RfG), https://eur-lex.europa.eu/legal-content/DA/TXT/?uri=uriserv%3AOJ.L_.2016.112.01.0001.01.DAN Specifically, we will showcase its application in assessing critical performance aspects such as:

• Frequency Sensitive Mode (FSM)
• Limited Frequency Sensitive Mode - Over- and Underfrequency (LFSM-O/U)
• Reactive Power Capability
• Voltage Regulation Capabilities
• Fast Fault Current Contribution

with specific reference to the Danish Grid Codes for RfG, https://energinet.dk/media/zsxpqk5t/16_05118-127-nc-rfg-nationale-krav-for-nettilslutning-af-produktionsanlaeg-revision-3-01-04-2025.pdf

It should be noted that although the suite of test cases that can come with the MTB are specifically chosen to test for grid compliance against the Danish Grid Codes, they can easily be customized by simply editing or adding a Row in the supplied “testcases.xlsx” Excel Workbook that is used as input to the MTB. Test cases are currently grouped into four Sheets, i.e. for:

• RfG cases
• Demand Connection Code (DCC) cases,
• Unit cases and
• Custom cases

For each test case, one need to specify the initial voltage (U0) and power (P0) setpoints, the P-and Q-modes the plant is operating in, and depending on the Q-mode, the related initial Q reference setpoint (Qref0). This depends on whether constant Q, constant Power Factor (PF) or Automatic Voltage Regulation (AVR) mode, sometimes also called Q(U) mode was selected. The MTB also allows for three Short-Circuit Ratios (SCRs) and their corresponding X/R ratios to be used for a test case. Typically, at maximum, minimum and at a level in between these two extreme values.

For each test case, up to 12 events can be specified. This includes:

• the event type,
• the time at which the event occurs,
• the new step value change, or
• the new ramp value change, e.g. a df/dt event

Currently supported event types are:

• A voltage change at the PoC (both step and ramp)
• A relative voltage change at the PoC (both step and ramp)
• A new active power (P) reference (both step and ramp)
• A frequency change at the PoC (both step and ramp)
• A relative frequency change at the PoC. (both step and ramp)
• A change in the grid impedance (SCR and X/R ratio)
• A new reactive power (Q) reference, based on the Q-mode of the plant (both step and ramp)
• SIPS or EPC signals
• Applied faults
• Phase jumps at the PoC
• Changes of custom signal (currently 10 supported)

The tool supports combinations of all event types in a single simulation case. Such as change in the grid impedance when a fault clears, representing properly the real scenario of a fault event.

While the MTB significantly automates test case generation and execution, the process currently still requires skilled engineers to visually inspect and evaluate the HTML, Plotly generated output results for grid code compliance. This also includes checking for consistency between the output of the EMT and RMS models. The test case examples that will be presented, will highlight the tool's effectiveness in streamlining the compliance verification process.

The open-source nature of the MTB toolbox, documented extensively on its Wiki, https://github.com/Energinet-SimTools/MTB/wiki, fosters collaboration and allows for continuous development towards further automation. Ultimately, the MTB toolbox offers a significant step towards accelerating the integration of renewable energy sources into the power grid by simplifying and standardizing the crucial grid code compliance testing phase.