DC Station Control of HVDC transmisson system

DC station control hvdc

1. DC STATION CONTROL 500 KV HVDC Terminal, Mahendragarh

2. DC Station Control – Key presentation points Control system hierarchy Control overview Hardware: Cubicle, SIMATIC-TDC Rack Functional description Switchyard Interlocking (DC and AC Filter Subbanks) AC Filter Control DC Switchyard Control DC Current Limitation due to AC Filter Configuration Redundancy Aspects

3. DC Station Control - Control System Hierarchy

4. DC Station Control – Control overview

5. DC Station Control - Control overview

6. DC Station Control - Hardware: Cubicle, SIMATIC-TDC Rack TDC rack cards CPU MFI bus Serial communication Field bus connection LAN connection TDM bus communication Optical communication

7. DC Station Control – Functional description Bipole Control Power Order Calculator for scheduled bipole power Power Order Calculator for bipole level modulation controls (Run-Backs, Run-Ups, Power Limitation) Bipole Power Capability Calculator Current Balance Controller (CBC) DC Configuration Control DC Configuration Control Modes Switching of DC Yard without Inter-station Interlocking of DC switchyard Monitoring of MRTB / GRTB (MRS) Switching DC Configuration Control of Sub sequences in DC switchyard

8. DC Station Control – Functional description Subbank Switching Control AC Filter Control Functions Reactive Power Control AC Voltage Control DC Current Evaluation for Harmonic Performance Control Monitoring of subbank configuration Operation without sufficient AC filter Switching Frequency Control Manual Switching of Subbanks Co-ordination of Subbank Switching and Converter Operation Reactive Power Control Functions without Converter Operation AC Voltage Limitation Control Self Excitation Prevention Converter Shutdown and Reactive Power Bank Tripping after Outage of DC Station Control

9. DC Station Control – Functional description Control Level and Location Co-ordination: Co-ordination and changeover of Control Level (System-, Station Control Level) Co-ordination and changeover of Control Location (local DC HMI, DC HMI at remote converter station) Data Exchange with Remote Converter Station: Collection of received data from local Pole Control systems and operator control systems and transfer to remote converter station Distribution of received data from remote converter station to local Pole Control systems and the local operator control systems

10. DC Station Control – Functional description Sequence of Event Recording Function: Processing of messages received from I/O unit, bay control units and AC Filter Main Protection Processing of messages received from redundant DC Station Control system Processing of software messages Transfer of messages to the local DC HMI, RCI Redundancy Functions: HW monitoring functions SW monitoring functions System Selection Control Follow-up functions for ramp generators, timers and flip-flops

11. DC Station Control – DC Yard configuration sequence

12. DC Station Control – AC Filter Control AC Filter Control is a station related control function Reactive power control Reactive power level at the 400 kV AC busbar and busbar voltage are influenced by connected AC-filter, shunt capacitor and shunt reactor subbanks and reactive power consumption of the converters Main Functions measuring functions for AC busbar voltage and reactive power AC Voltage limitation control control and monitoring of AC filter switchgear subbank switching according to reactive power, busbar voltage and harmonic performance conditions and to avoid self-excitations of nearby generators Types of Reactive Power Sub Banks A : Filter subbank; double tuned 12/24 harmonic B : Filter subbank; double tuned 12/36 harmonic C : Filter subbank; double tuned 3 harmonic / high pass D : Filter subbank; single tuned 12 harmonic E : Shunt capacitor subbank

13. DC Station Control- Filter Control and Voltage Measurement AC Voltage control The reactive power values of the subbanks are measured using direct CT/PT inputs at the bay controllers 6MD66. Inputs are: the subbank current at CT -T3 and the busbar voltage at PT –T15 The AC busbar voltages are hardwired to the DC Station Control The maximum value of the bus-bar voltages is taken for further control functions The reactive power exchange with the AC network is calculated by totalizing the values of reactive power in the subbanks and two values related to the converter poles Positive sign represents capacitive and negative sign inductive reactive power

14. DC Station Control – Field bus loop

15. DC Station Control – Redundancy Aspects Designed as fully redundant system (system 1, system 2) for each pole All input signals are fed to both systems which evaluate these continuously The hot standby (passive) controller is updated by the data from the process (e.g. measured values, equipment status) Data not available from the process (e.g. reference values, integrator settings) are updated by information from the active system Separate cubicles for system 1 and system 2, mechanically / electrically separated each rack with its own processor and I/O-boards, separate 220V DC power supplies separate changeover logic modules (COL / LFM) Switchover to the hot-standby system can either be initiated automatically by the self-monitoring function of the active control system manually by maintenance personnel at the control cubicle

16. DC Station Control – Redundancy Aspects COL module LFM module

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