Projects:2018s1-182 Inertia Characterisation and Modelling in a Renewable Energy and Battery Based Microgrid

Introduction

Synchronous inertia, is basically the amount of stored energy in a power system that can be utilised during supply demand imbalances. Recently, due to high penetration of wind and solar power in a power system, thus form of inertia has slowly been decreasing thus causing instability in the power system as the frequency fluctuates more.

A possible solution for this is to provide more stored energy in the system using batteries. This is called synthetic inertia. Although not instantaneous like synchronous inertia, with fast frequency processing, synthetic inertia could be a viable way of minimising supply demand imbalances at all times and therefore stabilising frequency.

Project Team

• Maxwell Weppner
• Pei Ying Lim

Project Supervisors

• Assoc Prof. Nesimi Ertugrul
• Dr Wai-Kin Wong (Electranet)

Motivation

Power Systems are changing rapidly. In the South Australian case, on average, approximately 50% of the electricity is produced by asynchronous generators. However, the asynchronous supply at any given time can reach 100% and regularly does. This is in stark contrast with historical power systems where 100% of the electricity was sourced by synchronous generators all of the time. This has consequently had a number of effects on the modern power system, one being the ever decreasing synchronous inertia that historical systems inherently had.

Low system inertia is a problem when it comes to system stability as was seen in the 2016 Blackout in South Australia. Thus, it is desired to somehow replace this stability. Synthesizing inertia is one such method and has been explored in this project.

Objectives

The objective of this project is to model a renewable energy and battery based microgrid focusing on inertia characterisation. The project objectives are listed below :

a) Develop microgrid with +/- 0.15Hz of frequency regulation

b) Improve the rate of change of frequency measurement (RoCoF) scheme

c) Demonstrate the role of battery energy storage solution (BESS) for frequency regulation and frequency contingency

d) Software modelling and validation

Project Structure

This project is divided into multiple stages.

Stage 0 - Literature Research

Stage 1 - Validation of Previous Result

Stage 2 - New System Improvements

Stage 3 - Software Modelling and Validation

Project Results

Stage 1 - Validation of Previous Results.

In this stage, we reproduced the setup from the previous year and aimed to validate previous results.

We repeated all the experimental test beds that were performed in 2017. However, the exact results were not recreated because of the petrol generator itself. There were a number of problems with the generator, these included a fluctuating output voltage frequency and a distorted voltage sine wave. Under the load step changes that were imposed on the generator in these test beds, these problems were amplified. After reproducing the previous results to an acceptable limit, a deeper understanding of this system and its problems was realised allowing a platform for the remainder of the project to commence from.

Stage 2 - The New System

Due to the problems with the petrol generator it was replaced with a different system incorporating a DC Motor as the prime mover of a three phase synchronous generator. Simple resistive loads were applied to the system under operation to act as the "base load", electronic load banks were attached to each phase and were controlled by LabVIEW software. The same test beds were applied to this system to investigate the difference, the results showing that the new setup was superior. Following this, the LabVIEW software was significantly adjusted such that it could measure a declining frequency and turn the E-Loads off accordingly. It is important to note that this fast frequency response action was implemented separately from the E-Load control logic as it is supposed to be. Once this was implemented, various scenarios were tested and the characteristics of this FFR and this system as a whole were recorded.

Stage 3 - Modelling the System

References

[1]Deloitte, “Energy markets and the implications of renewables,” Deloitte, Adelaide, 2015.

[2] M. A. Pelletier, M. E. Phethean and S. Nutt, “Grid code requirements for artificial inertia control systems in the New Zealand Power System,” Transpower, Wellington, 2012.

[3] A. Portelli, “Inertia Characterisation and Modelling in a Renewable Energy and Battery Based Microgrid,” The University of Adelaide, Adelaide, 2017.

[4] R. Eriksson, N. Modig and K. Elkington, “Synthetic inertia versus fast frequency,” IET Journals, Sundbyberg, 2017.

[5] H. Thiesen, C. Jauch and A. Gloe, “Design of a System Substituting Today’s Inherent Inertia in the European Continental Synchronous Area,” Hochschule Flensburg, Flensburg, 2016.

[6] N. Miller, “Technology Capabilities for Fast Frequency Response,” General Electric, Schenectady, New York, 2017.

[7] M. B. S. M. Seyedi, “The Utilization of Synthetic Inertia From Wind Farms And Its Impact On Existing Speed Governors And System Performance,” Elforsk AB, Stockholm, 2013.

[8] F. G. -. Longatt, “IMPACT OF SYNTHETIC INERTIA FROM WIND POWER ON THE PROTECTION/CONTROL SCHEMES OF FUTURE POWER SYSTEMS: SIMULATION STUDY,” Faculty of Computering and Engineering, Coventry University, Coventry, 2012.

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[10] G. G. Haines, AESKB Software PMU Analyser V0.1 GH 2017-11-01, Adelaide: The University of Adelaide, 2017.

[11] K. Kikkert, “Response from Nesimi Team,” Google, Adelaide, 2018.

[12] D. Vowles, Power Systems Lecture Notes, Adelaide: The University of Adelaide, 2017.

[13] AEMC, The Frequency Operating Standard, Sydney: AEMC, 2017.

[14] “Multi-cylinder Engines (Automobile),” what-when-how, [Online]. Available: http://what-when-how.com/automobile/multi-cylinder-engines-automobile/.

[15] E. Explained, Flywheel - Explained, 2012.

[16] I. Toshio, H. Taniguchi, Y. Ikeguchi and K. Yoshida, Estimation of Power System Inertia Constant and Capacity of Spinning-reserve support Generators Using Measured Frequency Transients, Tokyo; Osaka: IEEE, 1997.