Combining Distributed Flexible Resources into a Virtual Power Plant

A Brief Presentation on Categorization and Application of Distributed Flexible Resources

Tony Yen
Renewable Energy Digest
3 min readSep 27, 2020

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Background

  • Flexibility Services Categorization…
    - With Different Timescale
    - With Different Spatial Features
  • Distributed Flexible Resources
    - Purely Supply
    - Purely Demand
    - Storage
    - Hybrid

Flexibility Services Categorization

With Different Timescale

Source: Status of Power System Transformation, IEA, 2018
Source: Demand-side Flexibility for Power Sector Transformation, IRENA, 2019

With Different Spatial Feature

  • Some flexibility services are (nearly) spatially homogeneous (effects are same independent of location of supply), e.g. frequency control under normal operation conditions
  • Others are spatially heterogeneous (effects depend strongly on location of supply), e.g. voltage control or frequency control under islanded operation conditions
Frequency control under normal operation conditions
Voltage control on a local grid

Cost Effectiveness of Different Resources

Source: On the way to efficiently supplying more than half of Turkey’s electricity from renewables, SHURA, 2019

Flexible Distributed Resources (Demand): Towards VRE-Availability-Based Demand-Side Management

Operation Paradigm — Past

Operation Paradigm — Present

Operation Paradigm — Future

VRE-Availability-Based DSM: Capacity Allocation

  • Assumption: N consumers, each has a profile 𝐷_𝑖(𝑡) (a stochastic time series), are to be supplied with a VRE fleet with fixed capacity 𝐶𝐴𝑃_0 and a maximum availability 𝐶𝐹(𝑡) (a stochastic time series)
  • Basic case: without adjusting the demand, find the optimal capacity allocation set such that expected total VRE consumption of the consumers is maximized

VRE-Availability-Based DSM: Flexible Demand Scheduling

  • Assumption: Each consumer is given fixed capacity allocation 𝐶𝐴𝑃_𝑖. Their demand can also be divided into two parts: a flexible part 𝐹_𝑖(𝑡) and an inflexible part 𝐼𝑛𝑓_𝑖(𝑡)
  • The flexible part is of the demand is a deterministic value that can be shifted around its default time occurrence 𝑡_0 between the interval [𝑡_0−∆𝑡, 𝑡_0+∆𝑡]; the inflexible part of the demand is a stochastic time series.
  • Objective: find the optimal schedule such that expected total VRE consumption of the consumers is maximized
We denote shift of flexible demand from 𝑡_0 to 𝑡′ as 𝑆_𝑖 (𝑡_0, 𝑡′ )

Flexible Distributed Resources (Supply): Flexible VRE Fleet

Methodology: Details in Potential Evaluation

Source: Dung-Bai Yen, Bidding Strategies and Impacts of Flexible Variable Renewable Energy Sources in a Simulated German Electricity Market, Inatech (University of Freiburg), 2019

Methodology: Reserve Allocation

Methodology: Reserve Delivery

Source: Schmidt et al. Case Study on Primary Frequency Control with Wind-Turbines and Photovoltaic Plants, IEEE, 2014.
Source: Alba Elena García Alonso, Maximum Power Point Tracking Algorithms for Solar Photovoltaic Systems, Escuela Técnica Superior de Ingenieros Industriales de Madrid (Universidad Politécnica de Madrid), 2017.
Source: Schmidt et al. Case Study on Primary Frequency Control with Wind-Turbines and Photovoltaic Plants, IEEE, 2014.

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Tony Yen
Renewable Energy Digest

A Taiwanese student who studied Renewable Energy in Freiburg. Now studying smart distribution grids / energy systems in Trondheim. He / him.