Development and analysis of distributed energy resources microgrid system using Simscape Electrical

This project deals with the development of various Distributed energy resources microgrid systems and focuses on the islanding condition. The simulations are carried out using SIMSCAPE electrical. An emphasis on how the microgrid is self-sufficient in maintaining the frequency is also shown.

INTRODUCTION

Microgrids are a localized group of electricity sources and loads that operates synchronously with the utility grid. These have emerged as a flexible architecture for deploying distributed energy resources (DERs) that can meet the wide-ranging needs of different communities.[1] These DERs can comprise of various components like electric storage, diesel generator and renewable devices like wind power and solar polar etc. Fig. 1 represents a system where various of these DERs are connected in the microgrid which is connected to the main utility grid.

Fig.1. Representation of Microgrid

Fig.2 Schematic representation of islanding a microgrid

According to the US Department of Energy [2], a microgrid is a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that act as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected or island mode. The emphasis of this project is to evaluate the transition of the system in island mode.

The main advantage of using a microgrid is its ability to get island and still remain online even if weather conditions are bad or grid faults occur. Due to the presence of local DERs, there is a drastic increase in reliability and dependence in completely isolated areas without traditional utility access

MODEL SETUP

For the working model, a 3-phase power supply is used. This is connected to a 3-phase transformer to step down the voltage to the desired value. This system is then connected to a load and a DG set which act as DERs in this case. Between the connection of transformer and DERs, a switch is implemented which controls the time when the islanding operation is desired. The islanding time in this project is 5 seconds and the model parameters are summarized in table (1 to 4). The model setup is shown in Fig. 3 The model stores the values of voltage and frequency as output.

Table 1. Parameters of 3 phase source

Table 2. Parameters of 3 phase transformers

Table 3. Parameters of Load

Table 4. Parameters of DG set

Fig. 3. Simulation model

RESULTS

Fig.4. Frequency analysis

Fig.5 Voltage analysis

Fig.4 shows the behavior of frequency with respect to time. . As can be seen the islanding condition occurs at 5 sec and due to a sudden change, the frequency begins to oscillate. However as can be seen, at a very large value of time, the frequency reaches back to 60 Hz. The time taken by the frequency to transient and reach back to rated value and is called as the persistent time.

Fig. 5 shows the variation of voltages with time. As can be seen, the voltage begins to oscillate at 5 sec and takes some time to adjust its value back to the rated voltage of 460 V. Fig. 6 shows the development of 3-phase voltage with time. These voltages can be seen to follow the cosine curve with changing amplitude during the transient time.

Fig. 6. Voltage variations

CONCLUSIONS

The analysis show that the frequency and voltage quickly restore to their rated values just after the islanding operations. Due to this it can be conclusively said that the microgrid is self sufficient once disconnected from the utility grid.

REFERENCES

[1] Adam Hirsch, Yael Parag, Josep Guerrero, Microgrids: A review of technologies, key drivers, and outstanding issues, Renewable and Sustainable Energy Reviews, Volume 90, 2018, Pages 402-411, ISSN 1364-0321

[2] Dan T. Ton, Merrill A. Smith, The U.S. Department of Energy's Microgrid Initiative, The Electricity Journal, Volume 25, Issue 8, 2012, Pages 84-94, ISSN 1040-6190,

[3] Real-Time Implementation of Islanded Microgrid for Remote Areas, Journal of Control Science and Engineering, Volume 2016, Article ID 5710950

[4] Microgrids: A review of technologies, key drivers, and outstanding issues, Renewable and sustainable energy reviews, Volume 90, July 2018, Adam Hirsch et.al

[5] The U.S. Department of Energy's Microgrid Initiative, The electricity Journal, Volume 25, Issue 8, Oct 2012, Dan T. Ton et,al

[6] Micro grid system development , Mathworks, Jonathan LeSage

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