Post on 06-Feb-2016
description
1
A stochastic power network calculus for integrating renewable energy sources into the
power grid
Presenter: qinghua shen
Wang, Kai, et al. "A stochastic power network calculus for integrating renewable energy sources into the power grid." Selected Areas in Communications, IEEE Journal on 30.6 (2012): 1037-1048.
2
content
• Intro• Formulation• Power system modelling• Performance metrics • Case study • Conclusions
3
1. Intro
• Motivationuse environmentally friendly sourcesadopt storage to match uncertain supply and demand (island)
improve reliability of the system
4
1. Intro
• MotivationWhy network calculus
The ability of the stochastic network calculus to model broad classes of queueing scenarios and capture statistical multiplexing gain
Why extend Decoupled arrival and service processSpecific performance metrics:
Fraction of Time that energy is not-served (FTNS) waste of power supply (WPS) (drop rate)
5
2. Formulation
• Problem descriptionIsland: only renewable sources for supplyStorage has limited capacity CNp: PV panels, Nw wind turbinesObjectives: reliability provisioning in terms of FTNS
6
2. Formulation
• Network Calculus was designed to facilitate stochastic performance analysis
(tail performance analysis with multiplexing)Envelop process to characterize arrival processQueue characterization:
7
3. Power system modelling
• Energy storage: discrete – Charged:
– Discharged:
– Differences from queue• Departure is not a function of the arrival and current
queue
8
3. Power system modelling
• Energy demand and supply– Upper curve:
– Lower curve:
– Similar for supply– Upper curve: similar to queue– Lower curve: needed for energy storage– Tightness: tradeoff between shapes of curves and
bounding function
9
4. Performance metrics
• Transform to non-recursive– recursive
– Non-recursive:
– Compare to previous work• Finite buffer length
10
4. Performance metrics
• How to present metrics recursive form
Loss of power supply:Fraction Time of no service:Waste of power supply (WPS)
11
4. Performance metrics
• How to present metrics non recursive form
Loss of power supply:
Fraction Time of no service:Waste of power supply (WPS):
12
4. Performance metrics
• Bound expression Loss of power supply:
Intuition: upper of demand - lower of supply
Waste of power supply (WPS):Intuition: upper of supply – lower of demand
13
4. Performance metrics
• More benefits to come!Multiplexing:
For N source with
Similar results for upper bound
• Something is missing! (hao)
15
5. A case study • Model fitting– Linear function with rate equal to long term mean rate– exponential functions for the bounding functions
16
5. A case study • Model fitting– Linear function with rate equal to long term mean rate– exponential functions for the bounding functions
17
5. A case study • Model fitting– Linear function with rate equal to long term mean rate– exponential functions for the bounding functions
19
6. Conclusion• Issues: demand and supply for an island– Only renewable energy– Storage aided– Reliability
• Good point– New type of “queue”– Finite buffer analysis
• Insufficient– Does this really matter (finite queue, decoupled?)
• My view– Not average tail but instantaneous tail(New fitting)– How will renewable energy impacts the market?