Browsing by Author "Kaewnukultorn, Thunchanok"

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    Characterization of Voltage Stabilization Functions of Residential PV Inverters in a Power Hardware-in-the-Loop Environment
    (IEEE Access, 2022-10-26) Kaewnukultorn, Thunchanok; Sepúlveda-Mora, Sergio B.; Hegedus, Steven
    The exponential growth of Photovoltaic (PV) technology is creating concerns for electric grid operators. As PV penetration increases, overvoltage in the distribution network can occur due to a mismatch between PV generation and load demand. However, PV smart inverters can be part of the solution to stabilize grid voltage. By providing reactive power and other grid supporting functions, PV inverters in a distribution network can mitigate this problem and enable a higher integration of renewable energy. To accomplish this, characterization and testing of advanced functions must be performed at a small scale before deploying these strategies in the field. In this work, we described in detail the components and communication interfaces of a Hardware-in-the-Loop testbed that includes two 3.8 kW PV inverters from different manufacturers. We conducted efficiency tests on the inverters and characterized the grid supporting functions for grid voltage stabilization, specifically constant power factor, volt-var, and volt-watt. We identified some abnormalities in the operation of the volt-var-watt control in one of the inverters and presented a method to overcome the limitation in remote control of another inverter using Modbus communication. Identifying, understanding, and overcoming shortcomings on the operation of PV smart inverters that provide grid supporting functions is key for the quick adoption of this technology and can help regulatory agencies to determine what is the appropriate control mode that will facilitate higher PV capacity. Additionally, we discuss the economic and technical implications of operating the inverter in active or reactive power grid control.
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    Smart PV Inverter Cyberattack Detection Using Hardware-in-the-Loop Test Facility
    (IEEE Access, 2023-08-23) Kaewnukultorn, Thunchanok; Sepúlveda-Mora, Sergio B.; Broadwater, Robert; Zhu, Dan; Tsoutsos, Nektarios G.; Hegedus, Steven
    This paper evaluates residential smart photovoltaic (PV) inverters’ responses to cyberattacks and assesses the performance of an intrusion detection strategy for smart grid devices by comparing time-series power flow results from a simulation application called Faster Than Real-Time (FTRT) Simulator to measurements from a Power Hardware-in-the-Loop (P-HIL) laboratory as a testbed. Twenty different cyberattacks from three classes - Denial of Service (DoS), Intermittent attack, and Modification - were designed and tested with grid-tied smart inverters in order to study the inverters’ responses to malicious activities. The intrusion detection strategy was developed using a comparison between the predicted PV power output from FTRT and the power flows measured from P-HIL laboratory through the API interface. Real and reactive power thresholds were assigned based on a number of repeated experiments to ensure the applicability of the thresholds. The results showed that inverters from different manufacturers have their own unique responses which could be detected by the power flow measurements. Our detection method could identify over 94% of actual malicious actions and 7.4% of no-attack hours are detected as false positives. Out of 38 under-attack hours, 2 undetected hours are due to the intermittent attacks. Different attacks can be detected based on the targeted components of the complex power that attackers are aiming to cause disturbances. Our findings additionally show that DoS can be noticed immediately after the devices have been sabotaged, and they can be detected from the active power analysis. However, modification attack detection will depend more on the reactive power measurements, while intermittent attacks remain the most challenging for the proposed detection method since the objective of intermittent attacks is to create an oscillation of the complex power components which need a relatively high time resolution for the measurement.