HVDC transmission is widely used in power system, especially the long distance and large capacity transmission, and the mutual influence of AC system and DC system or multiple DC system has become a hot research topic in power system. To carry out this research, it is bound to establish a corresponding simulation system, which is the core part of this simulation system.

Power system simulation is divided into Non Real Time Simulation and Real Time Simulation. Due to the low efficiency of the Non Real Time Simulation, it can not access the actual device, so it is widely used in the field of engineering application and system research, and the RTDS Real Time Simulation technology is widely used in power system simulation.

RTDS provides a rich model library, which can easily finish a simulation modeling of AC or DC primary system. The protection of its own control model of HVDC control model can build the foundation, but because its control characteristics have a large deviation with the actual, that can not meet the actual application requirements. Therefore, it can only use the actual HVDC control and protection device the way.

Although actual device access mode has solved the bottleneck problem of HVDC transmission system, however, this way also has the problems with high cost, large workload, low efficiency and long period. Even if the equipment is only one, it has to be joined up into all the control and protection devices of the whole project which generally tend to have more than 100 cabinets, therefore, it is very difficult to achieve for the general users.

Pole Control System

Pole control system contains a dozen control units (including dc power/current control, transient stability control, current balance control, current margin compensation control, inter electrode power transfer control, overload control, transformer tapping control, constant DC current control, constant dc voltage control, constant extinction angle control, etc.). Control units cooperate with each other, and under different operation conditions, there are different input modes and combination patterns. The operating characteristics of the HVDC system is mainly controlled by the dc voltage regulator, dc current regulator, and extinction angleregulator.

DC CURRENT CONTROL

Determination of Current reference

Current margin compensation

Voltage dependent current limit control

Transient current control

The inter electrode power transfer

Current balance control

Group voltage balance control (EHV)

Deblock sequence (EHV)

Series valve group deblock/block (EHV)

DC PROTECTION

In a system failure or other abnormal conditions, the DC protection by electrical detection of corresponding (current, voltage, power, frequency, etc.) changes or other non electrical quantity, make the correct response, and prevent damage to the HVDC equipment safe and stable operation of HVDC transmission system.

DC Converter Protection

Valve short circuit protection

Commutation failure protection

Twelve-pulse bridge differential current protection

Valve differential DC current protection

DC LINR PROTECTION

DC travelling wave protection

DC voltage sensing protection

Low-voltage of DC transmission line protection

Longitudinal differential protection of DC transmission line

Transverse differential protection of DC transmission line

STATION CONTROL SYSTEM

The station control system mainly includes the AC filter and converter transformer tapping control.

   AC Filter Control

Minimum filter

Reactive power control

AC voltage control

Dead-time control

Converter Transformer Tapping Control

Reactive power control

AC voltage control

Dead-time control