Introduction

Action˳NET has a solution for the management of microgrids with an algorithm to optimize the objective function to be achieved.

This solution allows you to perform the following procedures:

1. Model any microgrid using the OpenDSS program;

2. Automatically import the model for SCADA Action˳NET oriented to microgrid solutions;

3. Generate, automatically, the database of the imported model and the screens with the unifilar and general and detail screens of the devices that make up the microgrid (Generators, battery banks, solar plants, etc.);

4. Enter with the restrictive functions of the imported model, such as borderline voltages, maximum current, maximum demand, energy price, etc.;

5. In module studies, perform all microgrid simulations, both in "Snapshot" mode, as in "Daily" mode;

6. In real-time mode, simulate the behavior of the system, with simulated data similar to the real ones;

7. Finally, after the evaluation of the system, run the system with real data from the field and let the system optimize the defined objective function, in real microgrid management situations.

Depending on the microgrid model and its characteristic functions, the optimization algorithm is adapted and, after the model tests, a system that automatically controls that model in different customers is adjusted.

OpenDSS Presentation

Or Open Distribution System Simulator (OpenDSS) is a simulation software for electric power distribution systems developed and supported by the EPRI. The program supports most permanent analyses, commonly performed for the study and planning of distribution systems, as well as being able to perform new types of analyses that are necessary to meet the needs related to Smart Grids.

Many of the features found in the program were originally intended to support distributed generation system (GD) analytics needs. Other features support energy transport energy efficiency analysis and harmonic analysis.

Finally, OpenDSS is designed to be indefinitely expandable in such a way that it can be easily modified to meet future needs or to meet the specific needs of users.

It can integrate with various development environments, being now integrated into SCADA Action˳NET through an optional module.

Presentation of the Solution

Microgrid Model Used in The Sample Application

As described in the introduction, the solution is adapted for each microgrid model to be managed.

For the presentation of this solution, a hypothetical microgrid was created composed of a gas station and a restaurant connected to the distribution network. Both the gas station and the restaurant have a distribution board with a set of loads.

Figure 1 - Example of microgrid unifilar.

This pair (Station/Restaurant), as can be seen in the unifilar shown in Figure 1, has a generator set and a battery and, depending on the price of the distributor's energy, can:

1. Charge the battery from the distributor and/or generator set;

2. Feed the system through these two energy sources and export the surplus energy to the distributor;

3. Feed the system from the battery and export the excess energy to the distributor;

4. Feed the system from the generator set and export the surplus energy to the distributor.

The objective function of the system is to minimize the cost of energy of the gas station/restaurant pair, considering the price of the distributor's energy every hour and the price of the energy generated through the generator set, every hour, considering its consumption and the price of fuel.

In addition to minimizing the daily price of energy, the objective function must also respect electrical restrictions of the system such as:

1. Maximum apparent power;

2. Minimum power factor;

3. Maximum current;

4. Minimum and maximum voltage range of the system;

5. Demand contract of the post/restaurant;

6. Cost contracted when the demand limit is exceeded.

The objective function, in this case, optimizes the operation minimizing system losses and its operating cost.

System Configuration in SCADA

After microgrid modeling, within the OpenDSS program this automatically modeled network for the Action˳NET - Grid˳NET program, which is the SCADA already adapted for the development of Microgrid management solutions, is imported.

When the program is active, the window shown in Figure 2 opens.

Figure 2 - Program opening screen

Next, you select the configuration to import the microgrid modeled through OpenDSS into the SCADA environment.

When the system goes into configuration mode, as shown in Figure 3, at the top right, four buttons are shown:

The 10th button presents the OpenDSS import manual explaining how to structure these files and in which directory they should be placed. The 20 button imports the modeled files in OpenDSS. Figure 3 shows the SCADA screen after this import. The 30 button automatically generates the Action˳NET tags associated with each microgrid circuit, and finally the 4th button automatically creates the screen with the microgrid unifilar.

On the configuration screen, shown in Figure 3, there are three sections:

1. Elements: right after importing the microgrid, as shown in the figure, in "Elements", a combo-box is open where all the elements that compose it are. Each line presents a microgrid element modeled with its attributes.

2. Definition of reference parameters: the microgrid reference parameters are defined, used to create electrical restrictions that must be considered such as borderline voltages, minimum power factor, apparent power of the primary transformer cab, contracted demand and its cost, etc.

3. Electricity price of the distribution concessionaire: In the case of the microgrid connected to a concessionaire, the price of energy every hour.

Note that depending on the microgrid to be managed and its objective function, this configuration screen can be changed, as for items (2) and (3).

Figure 3 - Microgrid configuration screen, after importing the model.

 After setting up the microgrid, as shown in Figure 4, the user returns the opening screen and selects the process.

Figure 4 - Exit the configuration screen by clicking on the user icon (see image).

Application Toolbar

On all screens of the application is shown at the top of the screen the toolbar with buttons as described below:

Process/Studies-Snapshot Mode

Next, you go into process where there are two operational modes: Studies, which allows the analysis of the network's behaviour according to input data and simulations of operating conditions and optimization that reads the data in real time and runs the microgrid behavior optimization algorithm.

When you select process mode, the system goes into optimization mode, as shown below. Since there is no data from the field, everything is zeroed out.

Figure 5 - Process mode - Optimization.

By selecting the study mode, as shown in Figure 6, the system goes into simulation/snapshot mode. In this mode, you can work in snapshot or daily:

• Snapshot: a photo of the system is taken at a given moment of the day and one can study the behavior of the microgrid at this moment, after the power flow is performed, through the available OpenDSS reports (reports);

• Daily: Select one time of day to be studied, depending on the load curve of the system from zero hour to this moment.

Figure 6 - Process/study mode - Snapshot.

 In the figure above, the system is at full load, buying power from the concessionaire, the generator producing energy as well and the battery being charged.

It can act on the system, reducing loads, acting on circuit breakers, etc. and after wheeling the power flow and analyzing the system at that moment.

By clicking on an element of the microgrid you can check its parameters, as shown in the figure below where the user left-clicked on the name of the distribution concessionaire (GRAAL).

Figure 7 - Process Mode/Studies- Snapshot/Attributes of the GRAAL element.

Figure 8 shows an OpenDSS report of the power on each system circuit. Note that 13 OpenDSS reports are available in study mode, so the user can analyze the behavior of the microgrid.

Figure 8 - Example of a report generated in Process/Studies-Snapshot mode.

Process/Studies Mode - Daily

In Daily mode, you select an hour of the day and run the power flow from the beginning of the day to the set time. The figure below describes the toolbar functions for daily mode: 

1. Go to real-time mode.

2. Selects Snapshot/Daily mode.

3. Step interval.

4. Time to end the study.

5. OpenDSS reports available.

6. Wheel power flow to the defined range.

7. Load curve (station and restaurant).

8. Places gauges on each element of the microgrid.

9. Puts monitor on microgrid element.

10. Removes/Inserts network from the concessionaire.                                                                       

For example, in the figure below, the power flow of the whole day was performed, that is, from the beginning of the day to 24 hours.

Figure 9 - System in process/studies mode - Daily.

The following are some examples of studies done in daily mode:

1. Figure 10 shows the load curve of the gas station and restaurant for the study [0, 24h];

2. Figure 11 shows the insertion of meters in each element of the Microgrid. On the X axis we have the records, where each record is a microgrid variable and on the Y axis we have the 15 microgrid circuits;

3. Figure 12 shows two monitors showing P1 power in two circuits: CPFLPRITF1C4 and QTAQSCGRC1 during the 24 hours;

4. Figure 13 shows the islanding of the system, after the concessionaire's interconnection circuit breaker is switched off;

5. We turn off the load of the restaurant and monitor the load in the CPFLPRITF1C2 circuit. Note that the system starts selling power to the distribution concessionaire. Red arrows exporting power to the utility.

Figure 10 - Load Curve of the Gas Station and restaurant.

Figure 11 - Meters placed on each element of the Microgrid.

Figure 12 - Two monitors placed on 2 microgrid circuits.

Figure 13 - System islanding and load curve of the gas station after islanding.

Figure 14 – The restaurant load is removed and we show the power in the CPFLPRITF1C2 circuit.

Process/Optimization Mode

After studying the microgrid in all the desired conditions, the system can be activated in Optimization mode when, in real time, it should optimize the objective function of the microgrid.

Figure 15 shows the program running in real time, in simulation mode, when entries for the current time are simulated.

Figure 15 - Real-time Microgrid, entries simulation mode. 

Optimization Report

Finally, figure 16 shows the result of running the optimization algorithm for 24 hours. No restrictive function was transgressed, that is, the voltage was within the defined limits, the maximum demand was not exceeded, the power factor was always above the minimum limit, etc. When any penalty is recorded, the number of penalties is incremented and the penalty is flagged in different color. The operational cost of the energy is recorded and is shown the period of the day that the battery was being charged and the period that it fed the charges. In the model presented, there was a reduction in the cost of energy in the order 20%.

Figure 16- Result of the execution of the optimization algorithm.

Conclusions

The solution for any microgrid similar to that presented in the example is ready, simply by changing its attributes if there are some different conditions, such as a battery or a generator set other than the modeled element, a distribution concessionaire with another price/hour spreadsheet, loads and transformer different from the modeled ones, etc.

In the case of a different microgrid where, for example, there is a photovoltaic generation beyond the generator, it will be necessary to do a new modeling, a new unifilar and the objective function can be changed, as well as the reference parameters can be changed.

In the adequacy of the system for each new microgrid, it will be necessary to develop a new objective function, programming in C#, VB˳NET or Python. In addition, you may need to change the SCADA configuration screen to match the constraints that must be respected, as well as change the optimization report to reflect the new objective function with its constraints.

But once the new microgrid is complete, the solution will be ready for this second microgrid model and can be repeated for similar networks, but with different attributes, simply by changing the latter.