Joe Warner, Electric Power Industry Conference (EPIC), November 15, 2016 Advances in Grid Equipment Transmission Shunt Compensation

Transcription

1 Joe Warner, Electric Power Industry Conference (EPIC), November 15, 2016 Advances in Grid Equipment Transmission Shunt Compensation Slide 1

2 Excerpt from the BoA BoA: Book of Acronyms MSC/MSR: Mechanically Switched Capacitor/Reactor SVC: Static Var Compensator TCR: Thyristor Controlled Reactor TSR/TSC: Thyristor Switched Reactor/Capacitor STATCOM: Static Synchronous Condenser NPC: Neutral-Point Clamped MMC: Multi-level Modular Converter IGBT: Insulated-Gate Bipolar Transistor Slide 2

3 Network Challenges Shifting transmission system Synchronous generation retirement Penetration of distributed renewables and dynamic load Resulting in Weak networks with a resonance approaching fundamental frequency Increased vulnerability to disturbance Increased requirements for mitigation solutions Slide 3

4 Network Challenges National Grid Electric, Ten Year Statement Slide 4

5 Network Challenges Network resonances are shifting due to system changes Resonance frequencies and system damping affected by: Number of un-tuned shunt capacitor banks (over-compensation) Cable and T-line charging Parallel FACTS and HVDC installations (filters) System loading (active and reactive) Slide 5

6 Mechanically Switched Capacitors Solutions: 52 Cheap and low-loss for steady-state compensation Challenges: Slow switch-in/out and discharge Network dependent voltage step ΔUU UU QQ SS Overcompensation leads to low network resonance and has resulted in inadvertent network collapse rr = SS QQ Slide 6

7 Synchronous Condensers Solutions: Inertia increases system strength and provides fault current Reactive power compensation without generating harmonics Natural thermal overload capacity Challenges: Smaller output range ( < 100 MW) Var support provided by automatic excitation control, medium speed Maintenance Losses Slide 7

8 Static Var Compensator (SVC) Solutions: Fast, continuously variable output Large sizes available ( > 400 Mvar) Robust overvoltage capability Configurable to maximize value TCR TSR TSC Harmonic Filters Challenges: Slide 8 TCR generates harmonics Filter design dependent on network harmonic impedances Difficulty operating in a weak network Output varies with VV 2

9 STATCOM Converter Topologies u1-u t [s] 0 - Three-level NPC concept Pulse Width Modulation High Switching frequency (>1.5 khz) Maximum rating of 100 MVA IGBT units in series With IGBTS no voltage grading circuits (snubber circuits) Common dc-link Well suited for energy storage High harmonic generation Substantial power losses Slide 9

10 STATCOM Converter Topologies V1 V3 Chainlink MMC concept Cascaded H-bridges. Modular in # of cells 1 cell = 4 semiconductors (V1 V4) Number depends on required output. Distributed dc-link Low switching frequency ( ~300 Hz) U dc Lower power losses V2 V4 Slide 10

11 STATCOM How MMC works U dc U dc 20 cells vs. 2 cells above Slide 11

12 Static Synchronous Compensator (STATCOM) Solutions: V syst Fast, continuously variable output MMC configuration typically filterless V syst Operates in a weak network I cap I ind X T V conv Output varies directly with voltage Small footprint System Voltage Converte Voltage Capacitive Current Inductive Current VSC VDC - Challenges: Limited overvoltage capability Slide 12

13 SVC vs. STATCOM Performance V Capacitive Output 0 Inductive Output 1.0 I Slide 13

14 SVC vs. STATCOM Performance V B 1.0 Performance driven by vars, not speed A Vmin 0.8 STATCOM (±100 MVAr) SVC (±100 MVAr) SVC (125/-100 MVAr) Capacitive Output 0 Inductive Output 1.0 I Slide 14

15 SVC TCR Harmonic Generation n=5 HV bus 0.03 n= n=11 Y/d In/I n=13 n=19 n=23 n=17 n=25 n=7 n=11 MV SVC bus n=5 In Firing angle [degrees] TCR Filter banks Slide 15

16 STATCOM Harmonic Generation Slide 16

17 VI Characteristics Slide 17

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