Chasing the Wind on a Cloudy Day

IssuesIntegratingRenewablesChasing the Wind on a Cloudy Day

What problems do distributed

“renewables” pose

• Low capacity factor hurts payback

• Non-dispatchability requires standby generation

• Geographic non-optimal limitations

• Resonance interactions with series compensators or existing rotating machinery

• Introduction of frequent and severe transients reduce reliability and wear out equipment

(Distributed) Systems Reliability?

System Operators are penalized for violations of contractual power quality

99.5% Reliability = <1 day per year of failure

Fewer Components + High MTBF = Reliable Systems

Just how much gets to you?

Just how much gets to you?

How does Solar affect costs?

Why do we store energy (like this)?

How does the grid work?

Transmission Issues by Frequency

Transmission Lines

Real = Relative PhaseReactive = Relative Magnitudes

Short lines thermally limited

Long lines stability limited

Transmission Lines

TypicalLine

Per km @ 320km

LinekV

Resistancve

Reactance(O

hms)

Capacitance

(uF) SurgeImpedanceLoading(MW)

SurCur(kA

gerent)

TheLimi(MW

rmalt)

Cost perMile($MM)

345 0.04 0.37 4.52 480 1.39 960 2.1

Time AND Space are both constraints in the generation and consumption of energy

Power flows in the direction of phase angle decrease.

Wind causes severe frequency fluctuations both above and below 60 Hz.

What Functions Integrate

Renewables

• Increasing existing line capacity(constantly – steady state)

• Regulation (constantly - seconds)

• Directing Power Flows (occasionally: minutes)

• Transient Stability & Damping Resonance(occasionally - 0.03 to 15 seconds)

• Required Reading• FERC Order 1000 (May 2012)• FERC RM10-11 (June 2012)• FERC NOPR RM11-24

Existing SolutionsCapacity

250MVAR

Torque Amplification in Compensated Networks

Proposed Solutions• DC Isolation

• PE Inverter are functionally required to integrate wind and solar safely

• Regulation• Switched Impedance Issues

• Fixed VAR injection• ZVS or Serious Transients• Harmonics

• Synchronous Condenser or STATCOM• Variable VAR injection• Requires complex PE Inverters

Power Flow Control• SSSC• UPFC• IPFC

Speaking candidly with the DOE“There is not a single transmission expansion project in this country that is not currently being challenged by land owners.”“From Florida to California distribution feeders are being overloaded due to home generation of solar energy”“Many long lines in the western interconnect are currently being series compensated”-Pat Hoffman (Asst. Sec. of DoE Office of Electricity Delivery and Energy Reliability)

List of Figures

Fig. 1 – Frauhofer InstituteFig. 2, 3 - D. Rastler. Electricity Energy Storage Technology Options: A White Paper Primer on Applications, Costs, and Benefits. Electric Power Research Institute. 2010.Fig. 4 - IEEE P1726™/D10 Draft Guide for the Specification of Fixed Series Capacitor Banks for Transmission System Applications. IEEE. 2010

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ReferencesIEEE Subsynchronous Resononance Working Group, “Second Benchmark Model for Computer Simulation of Subsynchronous Resonance,” IEEE Transactions on Power Apparatus and Systems, Col. PAS-104, No. 5, May 1985.R.C. Dugan, M.F. McGranaghan, S. Santoso, H.W. Beaty, “Electrical Power Systems Quality, 2nd Ed.” McGraw-Hill, 2003. J.D. Glover, M.S. Sarma, T.J. Overbye, “Power System: Analysis & Design, 5th

Ed.” Cengage Learning, 2012.A.M. Dodson, R. McCann, “A Modular Multilevel Converter for Series Compensation of an EHV Transmission Line with Battery Energy Storage,” Power Electronics Conference of Illinois, PECI Feb. 2013M.G. Molina, P.E. Mercado, “Comparative evaluation of performance of a STATCOM and SSSC both integrated with SMES for controlling the power system frequency,” IEEE/PES Transmission & Distribution Conference & Exposition, 2004 Latin America.M.H. Haque, “Damping improvement by FACTS devices: A comparison between STATCOM and SSSC,” Electric Power Systems Research, 2006. L. Zhang, M. Crow, Z. Yang, S. Chen, “The Steady State Characteristics of an SSSC Integrated with Energy Storage,” Power Engineering Society Winter Meeting, 2001. pp. 1311 – 1316.L. Zhang, et.al. “A Comparison of the Dynamic Performance of FACTS with Energy Storage to a Unified Power Flow Controller,” M. El-Moursi, B. Bak-Jensen, M. Abdel-Rahman, "Novel STATCOM Controller for Mitigating SSR and Damping Power System Oscillations in a Series Compensated Wind Park," IEEE Transactions on Power Electronics, vol.25, no.2, pp. 429-441, Feb. 2010.

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