Introduction, Icons and diagrams

The HVDC converter library contains both 12-pulse and 6-pulse models. The control system is the same for both types of converters. However, 12-pulse models offer the possibility of choosing between two types of synchronization systems. Since each converter can be operated as a rectifier or as an inverter, the set of parameters is the same for all four converter models. However, different icons and elements are provided to differentiate rectifiers and
inverters. The control system1 includes regulation, synchronization, protection and tap changer subsystems. The models can simulate a valve short-circuit or a DC fault. Step responses can also be simulated to optimize the regulator parameters. Finally, the thyristor bridge can receive firing pulses from four different sources:

The internal generic control system provided with the converter;
An external physical source;
Simulink;
The HYPERSIM control module (control block)

A GTO based two-level voltage-source converter (VSC) may be modeled by using the GTO+diode switch type in the six-pulse inverter shown in Figure 11 - 4. The model implementation includes a logic for the simultaneous switching (OFF or ON) of a diode
with the switching of a GTO in accordance with the correct sequence. In this case, the “precision valve” option is not operational.

Icon and diagram of 12-pulse rectifier. This control system is only intended for the thyristor-based bridge.

Icon and diagram of 12-pulse inverter.

Icon and diagram of 6-pulse rectifier.

Icon and diagram of 6-pulse inverter.

Modeling the Converter and its Control System

The general diagram of a converter station including a 12-pulse converter, a converter transformer and the generic control system is shown in Figure 11 - 5. For a 6-pulse converter, the
bridge would be connected to one of the two secondary windings (star or triangle connections).
The general diagram of the control system is shown in Figure 11 - 6.

Valve Faults and DC Fault

It is possible to simulate a short circuit on any of the 12 valves (at the user’s choice) for a specified time interval (see form in Figure 11 - 16). A resistive grounded DC fault can also be simulated at the converter terminal. The time interval is referenced with respect to the start of the acquisition, or t = 0.