This work-in-progress paper shares our experience and student feedback based on the first two years of our international research internship program at Grenoble Institute of Technology in France made available by Virginia Tech and supported through an NSF IRES grant. This program, IRES: Track I: U.s.- France Program for INverter-based And Cyber-secure Control and Communication for eLEctric power system (PINNACLE), trains and sends about 18 U.S. students (6 each year) for 8 weeks to Grenoble to engage in research and extracurricular activities, including language instruction, several industry visits, and integration with an existing international internship program, in its G2Elab. The overarching theme of students' research projects is to enable a massively inverter-based electric power system while addressing control, communication, and cybersecurity requirements and challenges. Students' exposure to these problems, especially in a European context, is expected to help them think of innovative solutions to the U.S.'s similar challenges. Additionally, G2Elab has active collaborations with several industry partners, which facilitates industry tours and field trips. This program is mutually beneficial and strengthens our existing collaboration by providing a framework for conducting research projects of common interest. We recruit nationally for this program. The program alumni are a cohort of individuals with highly desired skills for industry and graduate programs.

Power system operation needs to match generation to load demand. Accurate load forecasting helps operators maintain the power balance, reducing generation costs and preventing outages. This paper proposes an improved fuzzy clustering load forecasting method based on similar day and normalization approaches, especially for short-term power system load forecasting. Simulation results utilizing data from PJM, demonstrate a reasonable forecast error compared to PJM day-ahead hourly load forecasts. The superiority of this method is the simple calculations and accuracy based on the historical data.

As the composition of the power grid evolves to integrate more renewable generation, its reliance on distributed energy resources (DER) is increasing. Existing DERs are often controlled with proportional integral (PI) controllers that, if not properly tuned or if system parameters change, exhibit sluggish performance or large overshoot. The use of set point automatic adjustment with correction-enabled (SPAACE) with a linear predictor improves the transient response of these DERs without the need to access the PI controller parameters. The limitation of the existing SPAACE method is the high sampling rate needed for improved performance, which is not always practical. This paper proposes the addition of a memory term to the SPAACE with a linear predictor. This memory term is the integral of the errors of previous samples, which adds another layer to the prediction to improve the response at lower sampling rates and further reduces the overshoot and settling time compared to the existing SPAACE method. Time-domain simulation studies are performed in PSCAD/EMTDC to show the effectiveness of the proposed controller.

The number of installed remote terminal units (RTU) is on the rise, increasing the observability and control of the power system. RTUs enable sending data to and receiving data from a control center in the power system. A distribution grid control center runs distribution management system (DMS) algorithms, where the DMS takes control actions during transients and outages, such as tripping a circuit breaker and disconnecting a controllable load to increase the resiliency of the grid. Relying on communication-based devices makes the control center vulnerable to cyberattacks, and attackers can send falsified data to the control center to cause disturbances or power outages. Previous work has conducted research on developing ways to detect a cyberattack and ways to mitigate the adverse effects of the attack. This work studies false data injection (FDI) attacks on the DMS algorithm of a fully inverter-based microgrid in real time. The fully inverter-based microgrid is simulated using an RTDS, an amplifier, an electronic load, a server, a network switch, and a router. The DMS is integrated into the server codes and exchanges data with RTDS through TCP/IP protocols. Moreover, a recurrent neural network (RNN) algorithm is used to detect and mitigate the cyberattack. The effectiveness of the detection and mitigation algorithm is tested under various scenarios using the real-time testbed.

Cyberattack susceptibilities are introduced as the communication requirement increases with the incorporation of more renewable energy sources into DC microgrids. Parallel DC- DC converters are utilized to provide high current and supply the load. Nevertheless, these systems are susceptible to cyberattacks that have the potential to disrupt operations and jeopardize stability. Voltage instability may result from the manipulation of communication commands and low-layer control signals. Therefore, in this paper, a cyberattack that specifically targets parallel DC-DC converters is examined in a DC microgrid. A hybrid machine learning-based detection and mitigation strategy is suggested as a means to counteract this threat The false data injection (FDI) attack targeting the converters is investigated within a DC microgrid. The efficacy of the suggested approach is verified via simulations executed for various scenarios within the MATLAB/Simulink environment The technique successfully identifies and blocks FDI attacks, preventing cyberattacks and ensuring the safe operation of the DC microgrid.

Due to the increasing popularity of DC loads and the potential for higher efficiency, DC microgrids are gaining significant attention. DC microgrids utilize multiple parallel converters to deliver sufficient power to the load. However, a key challenge arises when connecting these converters to a common DC bus: maintaining voltage regulation and accurate current sharing. Unequal cable resistances can cause uneven power sharing and lead to power losses. Conventional droop control methods, which employ a virtual resistor to address this issue, have limitations in achieving good performance across the entire converter operating range. This paper proposes a modified droop control algorithm to address this issue. This method modifies the virtual resistor in a way that ensures power sharing aligns with each converter-rated capacity. The algorithm is simple to implement and uses local measurements to update the droop gain. This paper presents simulation studies and experimental tests to analyze the performance of the proposed method, considering scenarios with equal and unequal converter ratings. The results successfully validate the accuracy and effectiveness of this innovative approach.

The power system, dominated by synchronous generation, is moving toward a higher share of renewable generation. A voltage-source converter (VSC) known as an inverter is usually utilized as an interface between renewable generation units and the power system. Different methods are developed to control the voltage and power of VSCs. This paper evaluates the performance of a voltage controller and an angle droop-based power sharing method for a power system, which is a combination of inverter-based generation units and a synchronous generator. The studied controllers enable 1) accurate power sharing between all inverter-based generation units, 2) terminal voltage regulation by considering the maximum current of renewable generation units, and 3) maintaining frequency of the system at 60 Hz in the steady state independent from communication links. Different simulation case studies are performed in PSCAD/EMTDC software to study the performance of the angle droop-based power sharing algorithm.

This paper studies the transient behavior and resonance mitigation performance of a grid-connected voltage-sourced converter (VSC) under several control strategies using hardware-in-the-loop (HIL) simulation. Many VSCs use LCL filters to increase their power quality. However, an LCL filter may increase the possibility of resonance. Therefore, controllers need to include an active damping feature to improve the transient behavior of the system. There are several active damping current controllers such as 1) internal model control, 2) virtual RC damping control, and 3) notch filter control methods. This paper discusses the overshoot, rise time, and dq-axis current decoupling feature for each controller using HIL simulation case studies performed in the OPAL-RT real-time platform.

This project presents a power sharing and voltage control scheme for multi-terminal HVDC (MTDC) grids. A generalized hierarchical droop-based controller is designed to control the DC-side voltages and dispatched powers. To improve the steady-state performance of the MTDC grid, this project proposes a feedforward mechanism to make the current controller of the voltage-sourced converters (VSC) independent of the AC-side load conditions. The performance of the proposed scheme is evaluated under several case studies. A comparison between the proposed controller and traditional controllers is also made with time-domain simulation studies in PSCAD/EMTDC software. Results show that the proposed controller can successfully control the real powers and DC voltages while having a stable performance during AC-side load changes.

Analytical evaluation and voltage control method of a cascaded step-up switched-capacitor converter (CSU-SCC) under zero current switching (ZCS) operation and continuous conduction mode is studied in this paper. The ZCS condition, which means operation below resonant frequency, makes the soft-switching operation of switching devices. Therefore, it increases the converter efficiency. In addition, due to operating in higher range of switching frequency, the size of proposed converter can be reduced (i.e., higher power density). Compared with the competitive topology of SCCs, it enables the output voltage regulation of the converter under ZCS. The proposed CSU-SCC provides a higher range of output voltage and power by proposing an exponential structure of an SCC. An analytical study is developed to calculate the output current and voltage characteristics of the converter. Based on the derived output voltage characteristic, a closed-loop voltage controller is proposed to regulate the output voltage of the CSU-SCC under different conditions. The simulation results for an input voltage 110 V-160 V and 500 W CSU-SCC converter verify the proposed analysis and the proposed voltage controller.

This paper investigates the impact of cyber attacks on the voltage regulation problem in distribution grids with photovoltaic (PV) units that have reactive power capability. While previous research has studied voltage regulation from different aspects, the impact of cyber attacks on this problem is not thoroughly analyzed. This paper employs a centralized control scheme equipped with an attack detection algorithm that utilizes voltage measurements at different parts of the distribution grid. It shows how modification of measurements by an undetected attack affects the dynamics and reactive power injection capability of the PV inverter. In addition, the impact of a cyber attack on the reactive power control loop of the PV inverter is studied. Finally, the results of this study are used to assess the risks in reactive power control by a PV inverter affected by a cyber attack. Studies in this paper are performed on the IEEE 13-bus test system augmented by PV generation with the full cyber layer model implemented in MATLAB/SIMULINK simulation tool.

In recent years, there has been a significant increase in wind power penetration into the power system. As a result, the behavior of the power system has become more dependent on wind power behavior. Supervisory control and data acquisition (SCADA) systems responsible for monitoring and controlling wind farms often have vulnerabilities that make them susceptible to cyberattacks. These vulnerabilities allow attackers to exploit and intrude in the wind farm SCADA system. In this paper, a cyber-physical system (CPS) model for the information and communication technology (ICT) model of the wind farm SCADA system integrated with SCADA of the power system is proposed. Cybersecurity of this wind farm SCADA system is discussed. Proposed cyberattack scenarios on the system are modeled and the impact of these cyberattacks on the behavior of the power systems on the IEEE 9-bus modified system is investigated. Finally, an anomaly attack detection algorithm is proposed to stop the attack of tripping of all wind farms. Case studies validate the performance of the proposed CPS model of the test system and the attack detection algorithm.

This paper investigates control of multi-port DC microgrids with a fast transient response and online parameter adaptation. This DC microgrid can handle connection and disconnection of several energy generation units (e.g., fuel cell or photovoltaic units) and battery energy storage units to provide a DC load. To control several unidirectional and bidirectional converters of this microgrid, a scalable model predictive control (MPC) with online parameter adaptation capability is proposed. This adaptive model predictive control (AMPC), which provides fast MPC control for both inner and outer control loops, obviates the need to have a good knowledge about system parameters (as required by conventional MPC controllers). The estimated values of system parameters are deployed in the MPC controllers to ensure fast transient response of the system. This controller increases the scalability of the system to add or remove new power units with unknown parameters. Simulation case studies validate the proposed controller structure.

Performance analysis and output voltage regulation of a cascaded step-up switched-capacitor converter (SCC) under zero voltage switching (ZVS) condition is analyzed in this paper. The ZVS condition (converter operation above its resonant frequency) provides 1) zero-voltage switching, which leads to a relatively higher efficiency compared to zero current switching (ZCS) under the resonant frequency in MOSFET-based converters and 2) operating in a higher frequency, which reduces the size and increases the power density of the converter. It also provides output voltage regulation compared with previously proposed SCCs in ZCS condition. This paper proposed a cascaded switched-capacitor converter (CSCC) that provides a high voltage gain. For this structure, it proposes a mathematical analysis to calculate the output voltage characteristics of the converter. This study is then employed to design a control loop for the output voltage of the converter. The simulation results for a 110–160 V and 500W SCC converter confirm the proposed analysis and the designed control loop.

Fuel cell is an attractive alternative to generate clean electricity for many industrial applications. This paper discusses model predictive control (MPC) of a fuel cell-based power unit (FC-PU) for vehicular applications. The MPC improves the transient response of the FC-PU. In this FC-PU, a unidirectional converter controls the current of a proton exchange membrane (PEM) fuel cell, and a bidirectional converter controls the output DC link voltage by regulating the battery current. The proposed MPC structure in the continuous control set (CCS) scheme has a fixed switching frequency and employs two different sampling frequencies to provide MPC for both inner and outer control loops. This controller provides a fast response to the changes in the reference values of the control variables or system transients such as load transients. It is also robust against parameter mismatch. Simulation results validate the proposed controller via several simulation case studies.

A modular multilevel converter (MMC), which provides output voltages with low harmonic contents, gives a simple structure without needing several isolated DC power supplies. However, an MMC suffers from sheer number of switches and associated electronic circuits because it requires the addition of two half-bridge submodules to one leg of the converter to add only one voltage level to the output voltage waveform. This paper proposes a granular multilevel converter (GMC) that provides required number of voltage levels with a reduced number of power switches and associated electronic circuits. In the proposed GMC, the addition of one submodule doubles the number of output voltage levels. For a specific number of submodules, the charge control algorithm of the capacitors and the switching table of the proposed converter are described. The proposed control algorithm ensures the voltage control of submodule capacitors using hysteresis controllers and the data from the transducers of the line current and capacitor voltages. The proposed converter structure, charge control algorithm, and switching table are validated by simulation case studies.

This paper studies the operation of a microgrid under various scenarios with a focus on the effect of communication delays. The test microgrid is the CIGRE-IEEE low-voltage system, and a variety of loads are modeled in the system, including a nonlinear load, an impulse load, a battery, a highly capacitive load, and a highly inductive load. The simulation studies cover three scenarios: 1) a system with load changes, 2) a system with a transient fault, and 3) a system with both a transient fault and communication delay. The paper aims to determine the maximum permissible latency for all the case studies.

Fuel cell-based power units have increasingly become an attractive option to provide clean and efficient electricity in certain niche applications. This paper discusses the characteristics of a proton exchange membrane (PEM) fuel cell for a battery extender auxiliary power unit and explains the steps of the design process. A two-leg converter topology is proposed to control the fuel cell output, battery charge and discharge process, and the voltage of the DC link. Different operating modes of the system are analyzed and the functions of energy management system are studied. Sizing for the fuel cell, battery, power electronic converter, and passive components are presented, and the controllers of the power electronic converter are designed. Simulation case studies in both steady state and transient conditions are presented to validate the effectiveness of the presented fuel cell-based battery extender power unit and the proposed design process.

This paper proposes an improved prediction algorithm for SPAACE, a strategy for mitigating transients at a distributed energy resource (DER) caused by disturbances in a microgrid. Controllers used by DER units are typically tuned for grid-connected operation of a microgrid. However, islanded operation changes the dynamics of the system making it more susceptible to large transients that may violate the operational limits of the system. The previously proposed strategies are called set point automatic adjustment with correction enabled (SPAACE) and SPAACE with prediction enabled. SPAACE works by tracking the output of a system (e.g., current, voltage, or power) and adjusting its controlled set point during violations in order to shape the trajectory to a desired form. SPAACE with prediction works similarly but adjusts the set point based on predicted values of the system output. Case studies are presented to demonstrate the ability of the improved strategy to mitigate transients in current and voltage control modes.

Estimation of electromechanical modes has attracted attention during past few decades because the estimation of these modes provides vital information about the stability of the power system. In this paper, a new state-space model is developed for online detection of a ringdown signal using extended Kalman filter (EKF). The proposed model not only can estimate constant parameters, but it can also track time-varying parameters. Simulation results demonstrate the desirable performance of the proposed method for ringdown parameter estimation.