frequency support among asynchronous …...frequency support among asynchronous ac grids through...
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FREQUENCY SUPPORT AMONG ASYNCHRONOUS AC GRIDS THROUGH MULTITERMINAL DC GRID
Dr. Nilanjan Ray ChaudhuriAssistant Professor
School of Electrical Engineering and Computer Science
Pennsylvania State University, University Park, PA
SUstainable Power & Energy Research Group(SUPER Group)
Thrust I: HVDC and MTDC
Thrust II: PMU Data Anomaly Detection & Correction
Thrust III: Wide-Area Damping Control
Thrust IV: Coupled Cascading Failure
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Amirthagunaraj YogarathinamPh.D. Student
Jagdeep KaurPh.D. Student
Kaveri MahapatraPh.D. Student
Kaustav ChatterjeePh.D. Student
Sai Gopal VennelagantiPh.D. Student
SUPER Group Team
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Asynchronous AC Grids
(a) (b) (c)
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Tres-Amigas Project
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Plan to capture rich offshore wind resources of North Sea, solar resources in sub-Saharan Africa
Plan to interconnect the major generation and load centers of UK, Scandinavia, and continental Europe forming a 'Super Grid'
Motivation for MTDC
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System Configuration
Schematic of the bipolar MTDC grid with metallic return (single-line diagram) connecting 4 asynchronous AC areas
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Controller Structure [J2]
Distress signal carries basic information as to which area is seeking help
With this new inertial and frequency droop control, the power of converter in itharea is given by,
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Nth-order Model
where, �𝑘𝑘𝑣𝑣𝑣𝑣 represents the normalized voltage droop coefficient (i.e., they add upto one)
The unique structure of matrices 𝐻𝐻𝑁𝑁 and 𝐾𝐾𝑁𝑁, enables application of certain mathematical tools
With certain assumptions, the Nth-order model for an equivalent monopolar model of the system can be derived as,
where,
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Performance Constraints
Satisfying two constraints individually, ensures ratios are met at 𝑡𝑡 = 0 or ∞ Satisfying two constraints together, ensures ratios are met at all time, post-disturbance
In general, there are multiple solutions to each of these performance constraints
The requirement is that the frequency of participating areas be in a certain prescribed ratio,
Initial-slopes constraint: Steady-state constraint:
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Summary and Parameter Design [J2]
Voltage-droop Control Constant Power Control(i) Nominal Mode
(ii) Participating Area
(iii) Non-participating Area
Power and Voltage Referencesby System Operators
(i) or (ii) or (iii) based on distress signal
Inner Current Control Loop
Current References
Power and Voltage References
Inertial, Frequency and Voltage Droop Control
Modulation Index
Inverter Switching Control
Market Mechanism or Grid Code
Ratios andParticipation of Areas
for disturbance in Area#i
Solve for Droop Coefficients
Small Signal Stability Analysison Full-order Model
choose aset of droop coefficients
Unstable Stable
Repeat till Stable
End
Based on
System Operators Provide Ratios
Satisfying Performace Constraints
Controller summary: Design of droop coefficients:
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Response in Nth-order Model (Ideal)
A 20% reduction in generation of G7 (Area#4) : (a) frequency dynamics and (b) ratios among frequency deviations
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Response in Full-order Model (Non-ideal)
A 20% reduction in generation of G7 (Area#4) : (a) frequency dynamics and (b) ratios among frequency deviations of G7, G5 and G1 and (c) positive-pole DC voltage
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System Configuration with OWF
Schematic of the bipolar MTDC grid with metallic return (single-line diagram) connecting 3 asynchronous AC areas and offshore wind farm (OWF) [J2]
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De-loaded Control of OWF [J2]
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Simulation Results
A 10% increase in load at bus #19 simulated in full-order model with OWF: (a) frequency response along with emulated frequency and (b) positive-pole DC voltage [J2]
A 10% increase in load at bus #19 simulated in full-order model with OWF: (a) WF power output and (b) rotor speed [J2]
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Conclusion
A reduced-order model, i.e., Nth-order model of N-asynchronous-area MTDC system was derived
A ratio-based selective power routing scheme based on minimal communication was proposed for the provision of primary frequency support through MTDC grids was proposed
The method is extended to MTDC with OWF, wherein we can quantify and controlfrequency support provided by OWF
For converter outage, power references were modified to minimize the AC-side frequencies while respecting appropriate constraints
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References• J1. S. G. Vennelaganti, and N. R. Chaudhuri, “Selective Power Routing in MTDC
Grids for Inertial and Primary Frequency Support,” IEEE Transactions on Power
Systems, vol. 33, no. 6, pp. 7020-7030, Nov. 2018.
• J2. S. G. Vennelaganti, and N. R. Chaudhuri, “Ratio-based Selective Inertial and
Primary Frequency Support through MTDC Grids with Offshore Wind Farms,” IEEE
Transactions on Power Systems, vol. 33, no. 6, pp. 7277-7287, Nov. 2018
• C1. S. G. Vennelaganti, and N. R. Chaudhuri, “Controlled Primary Frequency Support
for Asynchronous AC Areas through an MTDC Grid,” in proceedings of IEEE PES
General Meeting, Portland, OR,2018.
• C2. S. G. Vennelaganti, and N. R. Chaudhuri, “Inertial Support from Offshore Wind
Farms Interfaced through MTDC Grids,” in proceedings of ICRERA Conference, Paris,
France, pp. 1-5, 2018.
SUstainable Power & Energy Research Group(SUPER Group)
Funding from NSF grant award ECCS 1656983 is gratefully acknowledged.
Thank You!