Introduction

The HVDC converter library of HYPERSIM contains both 6 and 12-pulse rectifier and inverter 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. The internal architecture is the same for 6,12 pulse and rectifier, inverter blocks, and the details provided here apply to all the blocks.

The thyristor bridge can receive firing pulses from three different sources:

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

In addition, the models can simulate a valve short-circuit or a DC fault. Step responses can also be simulated to optimize the regulator parameters.

Figure 1

Converter Model

The general diagram of a converter station including a 12-pulse converter, a converter transformer, and the generic control system is shown in Figure 2. For a 6-pulse converter, the bridge would be connected to one of the two secondary windings (star or delta connections). A GTO-based two-level voltage-source converter (VSC) may be modeled by using the GTO+diode switch type in the six-pulse inverter. The model implementation includes logic for the simultaneous switching of a diode with the switching of a GTO in accordance with the correct sequence. 

Figure 2