v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 W.K.HVDC Engineering INNOVATIVE TECHNOLOGIES FOR STABLE ACDC TRANSMISSION SYSTEMS No. 680 / W. KUEHN & D. MUELLER – GERMANY

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Contents 1German Grid Development Plan 2Power Control Methods  Normal DC Power Control  Power Sharing Control 3Low SCR Conditions 4Scheme and Contingencies Studied 5Charts 6Results

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 IEEE Spectrum 1a Europe Euphemia Could Europe's New Grid Algorithm Black-out Belgium? Pacific Northwest: “A key to the successful application of transactive systems is the use of automation to coordinate the decision making and action of the responsive assets.”

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No MW VSC based DC systems North to South plus interconnections with Sweden, Denmark, Norway, Belgium  High complexity grid not controllable in open-loop manner  Automation: Determine AC and DC OPF and establish OPF through proper controls without violating stability limits German Grid Development Plan „NEP 2014, Stand: November 2014, 1b

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Power Control Methods Dispatch of generation and DC power AC adapting to fluctuating generation and demand via ALFC DC AC Grid Normal DC Power Control Problem: Inadvertent AC power reversal at wrong DC power order High complexity: 8 to 10 point-to-point onshore DC transmission systems and more than 10 offshore DC connections 2 Gen. Dispatch Gen. Dispatch

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Power Control Methods Closed-loop control of power sharing No separate DC dispatch AC and DC power adapt automatically to fluctuating generation and demand via ALFC The parallel ACDC system behaves like an AC system Power Sharing Control DC Grid AC 3 Gen. Dispatch Gen. Dispatch

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Power Sharing Control Circuit OPF characteristic for automatic power sharing + Pac Pdc Ptotal k* Pdc/Ptotal k Pdc Pac PI- CNTRL 4 Power sharing control introduced in [6, 15]. dV/dQ criterion and VSF based HVDC stability analysis introduced in [6, 12].

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Low SCR Conditions What happens at sudden S.C.R. reduction? DC Grid AC 5 SCR At t = 4 s: SCR reduction through line trip DC order reduced automatically Sending end pushes power over parallel AC line => Instability Remedial measure Braking resistor or active load

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Scheme and Contingencies Studied 6 PQ diagrams required for: Ratings Operating ranges Limits Interpretation of simulator results

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Charts for Fault Case „a“ 7 DC Power AC PowerPower Angle Before fault: k = kopt After line trip increase of DC power to limit the power angle Reactive Power

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Charts for Fault Case „b“ Receiving Grid Power Receiving Grid Angle fault initiation battery almost fully charged line reclosure battery discharges max. batt. power Power Transferred Battery Power 8

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Results of Transient Simulation Automatic power sharing control meeting OPF Self-adapting power flow in AC and DC Only generation dispatch, no DC dispatch Transient stabilization through battery storage and storage power modulation Minimum load-rejection impact on sending end Control concept and storage principle also applicable to distribution grid 9

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Model Plant 10

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Battery Storage too expensive? Storage facilities will be needed anyway Battery costs will decline further Open question: Can distributed smaller storage stabilize bulk power infeed? => cell concept 11 ACDC Note: Back-up available for either battery or braking resistor solution = last resort method [10]

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Battery Storage too expensive? Risk of outage and blackout due to reduced short circuit power of receiving grid is similar to Classic HVDC Lost revenues to be compared with storage costs Future challenges need preparedness and, therefore, R&D on concepts and their feasibility Automation is the key factor for successful energy transition 12

v Winnipeg 2015 / Aug. 31 – Sept. 02 CIGRE Canada 2015 Conference No. 680 Thank You The End