MMC Design Aspects and Applications. John Strauss Siemens AG.

Transcription

1 MMC Design Aspects and Applications John Strauss Siemens AG. 1

2 VSC-HVDC with MMC Basic Scheme Reference HVDC PLUS Converter Arm Converter Module Power Module Electronics (PME) PM 1 PM 1 PM 1 PM 2 PM 2 PM 2 Power Module (PM) PM n PM n PM n Converter Reactors V d u d PM 1 PM 1 PM 1 IGBT1 D1 PM 2 PM 2 PM 2 IGBT2 D2 PM n PM n PM n Phase Unit

3 The Result: MMC a perfect Voltage Generation +V d /2 AC and DC Voltages controlled by Converter Arm Voltages: V Conv. ) V AC 0 -V d /2

4 Benefits of VSC-HVDC Space Saving HVDC PLUS Example 400 MW HVDC PLUS HVDC Classic

5 Basic Features of MMC Technology As little as 20 modules per phase will already meet IEC/IEEE limits without AC harmonic shunt filters. The reactive power can be controlled to any value within the limiting characteristics

6 MMC topology - Features and Benefits Low semiconductor switching frequency Low generation of harmonics High modularity in hardware and software Use of well-proven standard components Sinus shaped AC voltage waveforms Easy scalability Reduced number of primary components Low converter losses No Harmonic / PLC / Radio interference filtering required High flexibility, economical from low to high power ratings High availability of state-ofthe-art components Use of standard AC transformers Low engineering efforts High reliability, low maintenance requirements

7 Reference from HVDC PLUS - Win-TDC with PLUSCONTROL Remote HMI SIMATIC WinCC Win-TDC Local HMI RCI SCADA Interface Operator Level SIMATIC TDC C&P Level PLUSCONTROL Current Control System CCS I/O Level Measuring System MMS 1 Module Management System MMS n I/O Unit I/O Unit Switchgear & Auxiliaries Voltages & Currents Converter Power Modules

8 MMC Controls - Features and Benefits Current reversal possible with no minimum holding currents Full output vector controls Uni-polar DC voltage Full primary U/F controls Very Fast Closed Loop Control Flexible Control Mode Coord. (P-Q / U-F / Multi-Term) Allows for precise power flow control down to Zero MW Allows for independent control of Active and Reactive Power Good for Cable and Multi- Terminal applications Used for Black Start of Offshore grids (as well as SRAS) Allows for Fault Ride Through (FRT) and fault current inject Allows for even Faster (Linear) Power Reversal without Blocking of the Converters.

9 Fault Ride Through (FRT) Transbay Cable (Inverter Station)

10 Fast Power Reversal Simulated (based on TBC) VDC kv VDC kv AC Converter Voltages Currents at the AC Terminals Six Converter Arm Currents P DC MW P DC MW DC Converter Current

11 Offshore Windfarm Grid Access by HVDC Control Requirements The offshore converter station is the master device of the offshore grid The converter must be able to control the offshore frequency and voltage Blackstart is required basically no stable offshore grid at all Frequency and voltage control have to work for both power flow directions: Windfarm starting up or idling Windfarm generating power

12 Offshore Grid Control: 3p Offshore Fault Short Circuit Current Contribution 200 AC Voltages Offshore Rectifier 1.2 pu Short Circuit Current 400 Onshore Inverter kv 0 kv AC Currents pu 0 pu Active & Reactive Power Q Support Onshore (Loss of generation) pu DC Voltage pu pu pu DC Voltage pu pu DC Current & Offshore Frequency DC Current time time 1.2

13 Offshore Windfarm Grid Access with HVDC Braking Chopper at Onshore Converter Station DC side braking chopper absorbs dynamic excess power generated by the Windfarm during onshore grid interruptions Windfarm will take no notice of short onshore grid interruptions For enduring grid faults, the Windfarm may be throttled down in usual order, via Winfarm power control no emergency shut-down The Chopper is installed at the onshore converter station, the offshore station s footprint is not enlarged.

14 3p Onshore Fault Smooth Chopper Operation Offshore Rectifier Onshore Inverter AC Voltages Active & Reactive Power DC Voltage Smooth DC Voltage & Current DC Current & Offshore Frequency DC Current & Chopper Current

15 Modular Braking Chopper Features and Benefits Smooth DC voltage and current Redundant design Use of well-proven standard components Easy scalability Low number of primary components Save fault ride through of offshore windfarm High reliability High availability of state-ofthe-art components Low engineering efforts Low maintenance requirements

16 Conclusion Uni-polar HVDC is best suited for DC Cable, Multi terminal and DC grid application. VSC-HVDC System is the state-of-the-art DC transmission technology to provide grid access to large offshore wind parks and renewable energy supplies. VSC-HVDC System (as bulk power transmission system) is suitable for interconnecting AC Grids. VSC with MMC will be an integral part of future transmission systems.