Berta Test Bench

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BERTA Test Bench

OPAL-RT’s BERTA test bench is a safe, reliable and portable test bench for speed governors, turbines, voltage regulators (AVR) and power system stabilizers (PSS). Equipped with a high-performance real-time simulator programmed with world-renowned RT-LAB software, the BERTA Test bench enables users to easily and comprehensively test real generating units in the power plant, synchronized and transmitting power to the main grid and/or on real controllers connected to a virtual generating unit in laboratory.

Models and modeling parameters used in stability analyses are often theoretical approximations based on typical models and values. By relying on concrete data obtained through both open and closed loop tests, OPAL-RT’s BERTA makes it possible to accurately estimate and validate regulator, turbine and exciter system models. In addition, closed loop tests, which emulate islanded grid operation, can verify that the alternator under test contributes to the interconnected grid frequency stability.

Using the closed-loop feature, OPAL-RT’s BERTA solution lets users build and validate an accurate dynamic simulation of an alternator in an islanded grid in a fraction of the time required for traditional methods.

Increase Confidence Between Power Generators and Transmission System Operators

Control engineers and technicians can rely on BERTA for their on-site tests in power plant.

Electricity producers:

  • Control engineers involved in speed governor, AVR and PSS tuning;
  • Control engineers involved in validation and certification of generating unit control system technical specifications.

Engineering staff involved in generating units commissioning and/or specific on-site tests to comply with NERC (or any other regulatory agency) requirements on verification of models and data for:

  • Turbine/governor and load control or active power/frequency control functions; (Standard MOD-027)
  • Generator excitation control system or plant volt/var control functions. (Standard MOD-026)


The BERTA test bench can operate in two modes:

In open-loop operation, a disturbance signal with pre-defined shape and amplitude is injected into either the speed governor or voltage regulator and the various regulator, exciter or turbine behavior signals are observed. In addition to easily accessible or calculated signals, the simulator allows users to estimate alternator rotation speed and turbine mechanical power in real-time.

In Closed-loop operating mode, a real-time simulation of the rotor’s dynamic model allows users to calculate the speed deviation signal caused by the imbalance between the mechanical power and a virtual load. By injecting the signal in the speed governor while the alternator is sending power to the grid, it is possible to close the simulated speed loop and, thus, emulate islanded operation, even if the alternator is in fact synchronized with a multi-machine grid. As a safety measure, this signal is added to the real speed/frequency signal so that the simulator continues to react to grid frequency disturbances. The tests performed in this operating mode ensure the alternator stability if it were to be operated in islanded grid and improve its contribution to the stability of the larger grid to which it is synchronized.

BERTA functionalities:

    • Ensuring the tested unit's stability in an islanded power system, regardless of operating mode

    • Correctly setting AVR and PSS for damping natural electric power oscillations

    • Ensuring no interference between the speed governor and PSS, while continuing to contribute to the main grid stability

    • Certifying that the speed governor, AVR and PSS fulfill technical requirements.

BERTA provides:

  • Closed loop tests often reveal non-linear behaviors that were not anticipated through off-line simulations based on non-validated models;
  • Dynamic models are quickly available and validated on premises using real-time comparison with physical instruments;
  • Non-linear model parameter estimation.

BERTA is the best tool for complying to NERC’s MOD-026 and MOD-027 standards

NERC’s MOD-026 and MOD-027 standards require that electricity producers provide validated models of speed governors, turbines, AVRs and PSSs to the TSOs (Transmission system operators grouped in regional coordinating councils under NERC’s supervision).

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