Distributed Energy Management for Electric Power Systems

Transcription

1 Distributed Energy Management for Electric Power Systems Gabriela Hug, Soummya Kar, Chenye Wu,

2 Outline Introduction Decomposition Theory Theory Power flow control Consensus + Innovation Approach Theory Energy Management Conclusions 2

3 Introduction Prevailing Distributed Generation Resources Source: GTM Research, FERC 3

4 Introduction Active Distributed Generation Market Source: bcc Research 4

5 Introduction Demand/Supply Balancing Primary Control Based on local measurement of frequency; purpose is to stabilize frequency as load changes Secondary Control => Regulation Centrally controlled real time balancing; based on signal sent by control center every 4 seconds; purpose is to bring frequency back to nominal frequency and re-establishing tie line flows Tertiary Control => Energy Energy source scheduling including generator and storage dispatch and demand side management 5

6 Introduction Supply side is becoming increasingly distributed. In addition, demand side is also expected to become more flexible and provide regulation services. High volume of active participants is stressing the centralized control. Distributed approach can reduce the reliance and burden on the ISO, and potentially help to create a selforganized market. All these concerns warrant contemplating a distributed energy management system. 6

7 Introduction Definition of distributed optimization Multiple entities share control responsibility Each entity has limited information Goal is to achieve overall optimum via iterative process and communication among entities vs. 7

8 Challenges Energy Dispatch Algorithm needed for distributed optimization. Integration of distributed storage and ensuring that net load variations can be balanced. Distributed MPC and OPF solutions. Regulation Service Maintaining real time balance is already hard with central control. With current system, it is hard to perform efficient dispatch, since ACE is an integral signal. Distributed Frequency Control Solution. 8

9 Energy Dispatch Distributed Approach Based on consensus plus innovation approach Consensus: agreement on price Innovation: power balance Generator Load Storage 9

10 Energy Dispatch Characteristics of Approach Power balance only fulfilled once iterations converged Assumption is that load stays constant while iterating 10

11 System Model 11

12 Frequency Control Research Question: Can we develop a fully distributed framework for secondary frequency control with provable performance? Consensus plus innovations fully distributed control Real-time demand/supply balance Cost-effectiveness 12

13 Frequency Control Optimality Conditions Updating Rule for Participant n 13

14 Frequency Control Suppose primary frequency control is in place to stabilize the frequency. In steady-state, Assume γγ is a constant and Ω RR is public information By substituting this into updating rules, the updates can be done by measuring the deviation in frequency Δff locally. 14

15 Illustrative Example 50 participants; communication network is a 4-nearestneighbor graph System response by measuring the mismatch with sudden loss of 50 MW load. 15

16 Illustrative Example Phase 1: the innovations term dominates. Phase 2: the consensus term starts forcing the output of high-cost participants to ramp at a lower speed. Phase 3: the consensus term will further re-allocate the power outputs to achieve the cost effectiveness, while the innovations term will take care of small fluctuations. 16

17 Performance Evaluation Convergence Guarantee Derive ββ such that convergence criterion is fulfilled Real Time Balance Algorithm ensures that power balance is fulfilled while iterating whenever no ramping constraints become binding Cost Effectiveness Proof can be given that overall cost is cccc close to optimal dispatch, i.e. 17

18 Simulation Simulink Model 18

19 Simulation Parameters 19

20 Simulation Results for step change in load 20

21 Simulation Results for continuously changing load 21

22 Future Work How to quantify the impact of communication delay on the fully distributed control scheme? How to design a fault tolerant mechanism when considering the random measurement error of the local frequency? Try to use different cost functions, such as piecewise linear functions? 22