# An Overview of the Functions of Smart Grids Associated with Virtual Power Plants Including Cybersecurity Measures

Anas Abdullah Alvi, Enrique Romero-Cadaval, Eva González-Romera, Jamil Hassan, Dmitri Vinnikov

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Anas Abdullah Alvi, Enrique Romero-Cadaval, Eva González-Romera, Jamil Hassan, Dmitri Vinnikov. An Overview of the Functions of Smart Grids Associated with Virtual Power Plants Including Cybersecurity Measures. 14th Doctoral Conference on Computing, Electrical and Industrial Systems (DoCEIS), Jul 2023, Monte Da Caparica, Portugal. pp.95-107, 10.1007/978-3-031-36007-7_7. hal-05473094

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# An Overview of the Functions of Smart Grids Associated with Virtual Power Plants Including Cybersecurity Measures

Anas Abdullah Alvi<fnref n="1" />(✉), Enrique Romero-Cadaval<fnref n="1" />, Eva González-Romera<fnref n="1" />, Jamil Hassan<fnref n="2" />, and Dmitri Vinnikov<fnref n="3" />

**Abstract.** The use of renewable energy is on the rise and is expanding ever so greatly in this modern age of technology. However, it comes with a new set of challenges to properly integrate these renewable energy-based power plants thus forming a virtual power plant safely and reliably into the power grid in which a smart grid plays an effective role. The main focus of this paper is to review the functions a modern-day smart grid plays in the integration of distributed energy resources to the grid to form a virtual power plant including cybersecurity measures. It also addresses a basic example of the detection of a cyber-attack caused into the grid assuming it to be manipulated by a hacker together with a novel solution and later validated by performing simulation.

**Keywords:** Virtual Power Plant (VPP) · Smart Grid · Inverter · Cyber-Attack

## 1 Introduction

The virtual power plant (VPP) is the integration of distributed energy resources (DER) under a single coordinated management. A VPP is an interconnected network of decentralized, small-scale power generating technologies, such as solar panels, wind turbines, energy storage systems and manageable loads that work together under the control of a single control system. Similar to a conventional centralized power plant, the VPP may be regulated to adapt to changes in energy demand and supply and can offer grid services like balancing and stability. The purpose of this integration of dispersed energy resources into a unified utility grid is to improve the energy system's dependability, flexibility, and efficiency [1].

Large centralized generation units were intended to be managed by the power system so that real-time monitoring and control of their safe operation and dependability was possible [2, 3]. Renewable energy sources (RES), such as solar, wind, and hydro power,

<footnote n="1">¹ Electrical, Electronic and Control Engineering Department, University of Extremadura, 06006 Badajoz, Spain
alvi@unex.es</footnote>

<footnote n="2">² Energy Products and Services, Badajoz, Spain</footnote>

<footnote n="3">³ Department of Electrical Power Engineering and Mechatronics, Tallinn University of Technology, 12616 Tallinn, Estonia</footnote>
have been growing in popularity due to their environmental benefits and decreasing costs. However, their integration into existing power systems has presented new challenges for control and operation [4]. The overwhelming amount of information including weather forecasts, power demand, and supply, that operators must process in real-time and the dependability of the power electronics-based systems working in parallel, as hundreds of power converters would be simultaneously exchanging energy with the grid, is the main obstacle to increasing the expansion of RES. In practice, it has already been observed that generation systems powered by power converters are having an impact on the stability and dependability of power systems due to the dynamics of the converter not matching well with the dynamics of the grid or due to the introduction of voltage and current harmonics into the power system [5, 6]. Even though distributed RES-based units are currently only considered because of their modest involvement, this will change soon due to the rapid increase in RES integration and the diminishing situation of fossil fuel power facilities [7]. In order to balance generation and demand while also contributing to the stability of power systems, utility-scale renewable power facilities must be designed and operated in a certain method [8, 9].

Cyber-security is another important feature that must be taken into consideration for present-day smart grids. This paper consists of cyber-attack detection along with a novel solution by using islanding mode of operation of the VPPs when an attack takes place in the main grid. It also deals with the contribution of modern-day smart grids in the context of VPPs which are listed as follows:

* Transient Frequency and Voltage Stability

* Inertia Support Capability

* Power quality and stability

* Active and Reactive Power Control

* Fast frequency such as power oscillation and inertia response support, reactive power compensation and grid-forming capability.

* Cyber-security measures associated with smart grids.

## 2 Relationship with Technological Innovation for Connected Cyber Physical Spaces

The increased implementations of VPPs also comes with the challenges affiliated with data protection, securing physical systems and information privacy. Cybercriminals can now deliberately attack the energy sector to disrupt operations thanks to recent technological breakthroughs. Despite efforts by security researchers to reduce the dangers and vulnerabilities, it is still difficult due to the evolution of VPPs into a cyber-physical based system [10, 11]. This is why it is important to have technological innovation in the cyber physical spaces to keep up with the new and unknown methods of cyber-attacks in the energy sector. The energy sector has recently been one of the most targeted industries. Over time, the attackers' motives have evolved. Table 1 illustrates the increase in other incentives, such as cyberwarfare and causing disruptions, even though money is still the dominant driver [12].
<table><caption>**Table 1.** Effects of Cyber-Attack.</caption><thead><tr><td>Name of Cyber Attack</td><td>Place</td><td>Year</td><td>Impact</td><td>Vulnerability</td></tr></thead><tbody><tr><td>BlackEnergy</td><td>Ukraine Power Grid</td><td>2014/2015</td><td>In Ukraine, a power disruption for a duration of 6 h occurred which affected almost 230,000 people</td><td>Poor infrastructure, corruption, and tensed relations with external countries [13]</td></tr><tr><td>Industroyer/Crash Override</td><td>Ukraine Power Grid (North City of Kiev)</td><td>2016</td><td>Ukraine lost 1/5 of its electrical capacity due to an hour-long power outage</td><td>Direct control of the switches and circuit breakers at power grid substations using four ICS protocols [14]</td></tr><tr><td>Triton</td><td>Oil and Gas Plant Saudi Arabia</td><td>2017</td><td>The attackers were interested in causing an explosion to spread throughout the entire plant, but their plan was thwarted due to a virus flaw and vulnerability</td><td>Malicious TriStation protocol use by a malware framework to target the Triconex Safety Instrumented System (SIS) controllers [15]</td></tr></tbody></table>

# 3 Functions of Smart Grids

A VPP is a network-based system which combines and controls numerous DERs as if they were a single power plant. The VPP communicates with the grid operator and the combined DER. While physical power is exchanged between DERs and the grid, the VPP communicates with both the grid operator and the aggregated DERs as shown in Fig. 1. Some of the functions of smart grids associated with VPPs are discussed in detail below.

## 3.1 Inertia Support Capability

The VPP offers inertia support by synchronizing the parameters of grid-forming inverters. Additionally, an online learning-based parameter sets method is created that allows the VPP's inertia to be adjusted. Constant voltage and constant frequency control (V/f control), constant power control (PQ control) and virtual synchronous generator control (VSG control) are the three control techniques that the majority of DERs use to function. Grid-following (GFL) inverters frequently use PQ control, which is dependent on pre-determined frequency and voltage reference values. As a result, it cannot deliver active adjustable inertia support. V/f control, which is commonly adopted in
grid-forming (GFM) inverters, can function in a microgrid’s islanding mode but cannot supply inertia. A possible method to reduce system inertia is VSG control, which replicates the inertia and damping properties of traditional synchronous generators (SGs). By modifying the GFM inverters’ control parameters (i.e., damping coefficient D and the moment of inertia J) in VSG mode, the DERs’ inertia can be changed [16].

<figure><img src="image_4.png" /><figcaption>Fig. 1. Overview of VPP interactions.</figcaption></figure>

## 3.2 Power Quality and Stability

The grid-supportive capabilities of smart grids help the system to maintain power quality and stability. For network managers to directly observe and control every single inverter and DER, however, would not be feasible. VPPs and distribution energy resource management systems (DERMS) are therefore being studied in global states with high penetration of renewable energy. The DERMS software organizes various DERs to achieve local feeder-specific advantages such as optimal power flow, locational capacity relief, and voltage and active power management [17]. The management system can send control signals to smart inverters in DERMS-type applications to control demand-flexible DERs to assist the grid, such as discharging batteries to match the demand or halting electric vehicle (EV) charging to reduce demand. The inverter can function as an interface between the grid and the local energy asset because of its position at the point of intersection in the power network [18].

## 3.3 Voltage Stability and Transient Frequency Analysis

The flow and control of energy were the main objectives of the VPP models in the past. A dynamic VPP model must be implemented for the system transient response
study, a model that works well for system analysis and that the Transmission System Operator (TSO) can use to assess the effect of VPPs in the entire grid. The suggested framework can support the transient response of the vital controllers that comprise the distributed generators that constitute the VPP. The suggested aggregated model's validity is confirmed by comparison with a real-time detailed Electro-Magnetic Transients (EMT) model of the VPP [19].

## 3.4 Reactive Power Compensation, Frequency Support and Grid-Forming Capability

Transmission system operators (TSOs) are increasingly demanding power plants with power converter interfaces to provide frequency support, reactive power compensation, and grid-forming capabilities. In these plants, a substantial number of converters are run concurrently, and each one must be properly coordinated to offer these services. The virtual synchronous machine (VSM) control approach is frequently used for this purpose. The number of connected converters, their size, control settings, and electrical connections all affect how dynamically the entire plant behaves. Because of this, it is challenging to understand how each VSM affects the plant's response and its aggregated dynamic characteristics [20].

## 3.5 Fast Frequency Support

System operators have been obliged to tighten grid rules to require renewable power plants (RPPs) to offer fast frequency support, such as power oscillation damping and inertia response, because of the growing contribution of renewables to power systems. This can be achieved by implementing virtual synchronous power plant controller (VSPPC) for RPPs. Since it allows for the reproduction of inertia and offers capabilities for power oscillation damping, the VSPPC benefits the most from replicating the behavior of a SG, particularly in the case of grid events. The primary benefit of the VSPPC is that it avoids the need to modify the converter controllers in the plant, which are frequently controlled as grid-following generation units.

At present, RPPs are required to offer dynamic services like power oscillation damping and inertia response in addition to traditional control services, such as voltage regulation and frequency [21–26]. One of the approaches to establish these newly required services is to use the grid-forming power converters instead of grid-following power converters, which may use a controller based on a virtual synchronous machine [27]. Each power converter that forms a grid can function as a synchronous generator to give the grid damping and synthetic inertia, primarily managing the current or power reference [28, 29]. It has been shown that the implementation of a grid-forming power converter is practical for a single power converter [30, 31]. This strategy might not be financially viable for RPP, though, as it would be necessary to spend more time and money to design a new control system for the power converters. Moreover, the grid-forming power converters' independent parallel functioning may result in problems with power oscillation in the plant [32].
## 3.6 Active and Reactive Power Control

Distributed generation helps to improve the quality of power. Distributed generation (DG) provides significant advantages for the enhancement of the voltage profile and power factor in places where voltage support is challenging due to constraints on the primary (central) power grid. Large-scale decentralized power generation unit implementation may also cause instability. This is caused by the ineffective power control of the DG units, which also causes reactive power imbalance and fluctuations in the voltage of the power network. These factors make operating DG sources in a regulated environment crucial. As a result, DG control paradigms have been proposed, with MicroGrid and VPP being the two primary ones. For synchronous generators, there are currently no control paradigms that permit independent control of the machine's active and reactive power output. For any network to be stable, the power balance must be maintained. Generator instability, which can include rotor angle instability, voltage instability and frequency instability can be brought on by an improper balance of active and reactive power in the network [33].

# 4 Cybersecurity Measures in Grids

Modern day smart grids require cyber security measures due to the increasing number of attacks by hackers. There exist different types of solutions regarding cybersecurity measures in grids namely confidentiality, integrity, and availability [34] In this paper, two scenarios of attacks are considered in a VPP. The first one is the attack inside the low voltage grid or the microgrid. The cyber-physical layer of the VPP can monitor the voltage and current in different points of the layer to detect any sudden changes due to external manipulation and hence the system is restored back to normal operation. In the second scenario, the cyber-attack is considered inside the main grid or high voltage side. A novel solution is also proposed regarding this type of threat in detail by using the islanding mode of operation and later validated by performing simulation using MATLAB/Simulink.

## 4.1 A Basic Example of Determining Cyber Attack in a Micro-grid

A basic example based on Thevenin voltage closed form derivation is demonstrated in the following Fig. 2(a). It comprises of a PV field with 616 solar panel modules coupled in an array of seven series connections and eighty-eight parallel connections with a combined power of 250 kW. 50 Hz is the rated frequency taken into account for the system. In order to successfully reduce the harmonics introduced to an acceptable value and achieve the desired power quality, the PV field is linked to a three-level, neutral point clamping (NPC) inverter that converts DC power to AC and incorporates an LCL filter. A distribution transformer is finally used to link the system to the grid. On the high voltage side, a balanced three phase load rated at 250 kW (at a nominal voltage of 25kVRMS) is connected. Mainly, in this example, an attack is introduced in the point between the microgrid and distribution grid.
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** (a) Block Diagram of the Model under Study (b) An illustration of N-DEGs TVPP for the closed form derivation of Thèvenin voltage</figcaption></figure>

### 4.1.1 Scenario 1

One of the basic methods of identifying a cyber-attack is determining the manipulation of the voltage and current and as a result the power at different setpoints in a transmission line which are also known as Point of Common Coupling (PCC). The voltage and current in these PCCs are constantly compared with a fixed set of values in the cyber security outer layer. If there is a drastic change in either the voltage or current and as a result, the active power in these PCCs, it should be assumed that there is a high chance of the system being attacked during that period.

In the given illustration of N number of DEGs Technical Virtual Power Plant (TVPP) for the closed form derivation of Thèvenin voltage, the cybersecurity analytics system's methodology for identifying normal operation region serves as the foundation [35]. This region of regular operation is used as a confirmation approach to separate malicious set-points that the network cyber-layer requires. A cyber attacker who controls the set-points for the VPP cyber-layer is the source of these harmful set-points. Based on a derived one-to-one mapping between the cyber-layer generated set-points and the internal PCC bus voltages of the network, the normal operation region is defined. Using internal PCC bus voltage monitoring, this derived mapping is contrasted with an inverse mapping to look for anomalies. The voltage anomaly is caused by an intrusion after the cybersecurity analytics system notices a discrepancy between the one-to-one mapping and the inverse mapping [35].

The system is simulated for a total of 1s by using MATLAB Simulink software as demonstrated in Fig. 3. It is assumed that at 0.5s, the system is attacked by the hacker in between the point of microgrid and distribution grid and as a result the voltage, current and power values are changed from their rated values. From these manipulated values,
<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Voltage (in V) and Current (in A) waveforms in different points of microgrid, as indicated in Fig. 2a (a) during normal condition, (b) after the attack; and Voltage (in V), Current (in A) and Active Power (kW) waveforms of a single phase during (c) normal condition, (d) under attack.</figcaption></figure>

it can be easily identified that the system is under attack by the hacker and necessary steps must be taken to bring the system back to normal operating condition.

### 4.1.2 Scenario 2

In this case, it is assumed that a cyber-attack takes place in between the main grid and the distribution grid. Often in many circumstances, a hacker has no prior knowledge regarding the total network of VPPs across the whole transmission system. However, the hacker may have the total information regarding the main grid. In this case, the hacker tries to manipulate the data in the main grid system and makes the system unstable and as a result, a blackout may occur. One of the many solutions in this scenario is to isolate the grid from the system and use the islanding mode operation for the microgrid. In this case, the detection takes place if the voltage changes to ±15% and frequency to ±0.1 Hz [36]. In Fig. 4, a flowchart based on the algorithm can be established based on these aforementioned conditions.
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Flowchart for operating the system in islanded condition due a cyber-attack in the main grid.</figcaption></figure>

In this case in Fig. 5, the simulation results are observed for a total duration of 1s. At 0.5s, a hacker tries to manipulate the system in the main grid location. It can be observed that, if the main grid is not isolated from the grid connected PV based solar power plant, the system becomes unstable and is not able to generate any active power. However, if the grid is disconnected from the system by means of a relay, breakers and using islanding mode of operation, it can be observed that the solar power plant is able to supply active power into the loads and the system remains stable.
<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Voltage (in V) and Current (in A) waveforms in different points of microgrid, as indicated in Fig. 2a (a) before islanding condition, (b) after islanding condition; and Voltage (in V), Current (in A) and Active Power (kW) waveforms of a single phase (c) before islanding condition, (d) after islanding condition.</figcaption></figure>

**5 Conclusion**

This paper mainly reviewed the different functions along with cybersecurity measures of modern-day smart grids in the context of VPPs. The importance of these functions and the related existing challenges are assessed in different sectors of smart grids and the possible solutions are described. Finally, a case study is performed consisting of a grid connected PV power plant in which a basic detection of cyber-attack together with a novel solution is demonstrated by means of simulation by considering two scenarios of the point of attacks in a power transmission line. It can be observed that, islanding
mode of operation of a VPP can be an effective way to supply electrical power to the loads in a microgrid in case there is a cyber-attack in the main generation plant. In the future work, more ways to nullify the effects of cyber-attacks will be assessed along with the improvements of present-day solutions.

**Acknowledgement.** This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 955614.

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