Biblio

In today's power market, it's vital to keep electrical energy affordable to the vast majority of people while maintaining the highest degree of dependability. Due to which, the transmission network must operate beyond transfer limitations, generating congestion on transmission lines. These transmission line difficulties can be alleviated with the use of reactive power adjustment based on FACTS devices. Using a fuzzy tuned Static Synchronous Series Compensator [SSSC], this research proposes a novel method for calculating the effective damping oscillation control signals. The performance of the SSSC is compared to that of fuzzy logic-based controllers using PI controllers. According to the simulation results, the SSSC with fuzzy logic control effectively improves power flow under disrupted conditions

The modernization of legacy power grids relies on the prevalence of information technology (IT). While the benefits are multi-fold and include increased reliability, more accurate monitoring, etc., the reliance on IT increases the attack surface of power grids by making them vulnerable to cyber-attacks. One of the modernization paths is the emergence of multi-terminal dc systems that offer numerous advantages over traditional ac systems. Therefore, cyber-security issues surrounding dc networks need to be investigated. Contributing to this effort, a class of false data injection attacks, called load redistribution (LR) attacks, that targets dc grids is proposed. These attacks aim to compromise the system load data and lead the system operator to dispatch incorrect power flow commands that lead to adverse consequences. Although similar attacks have been recently studied for ac systems, their feasibility in the converter-based dc grids has yet to be demonstrated. Such an attack assessment is necessary because the dc grids have a much smaller control timescale and are more dependent on IT than their traditional ac counterparts. Hence, this work formulates and evaluates dc grid LR attacks by incorporating voltage-sourced converter (VSC) control strategies that appropriately delineate dc system operations. The proposed attack strategy is solved with Gurobi, and the results show that both control and system conditions can affect the success of an LR attack.

With the objective to eliminate the input current sensor in a totem-pole boost power factor corrector (PFC) for its low-cost design, a novel discretized sampling-based robust control scheme is proposed in this work. The proposed control methodology proves to be beneficial due to its ease of implementation and its ability to support high-frequency operation, while being able to eliminate one sensor and, thus, enhancing reliability and cost-effectiveness. In addition, detailed closed-loop stability analysis is carried out for the controller in discrete domain to ascertain brisk dynamic operation when subjected to sudden load fluctuations. To establish the robustness of the proposed control scheme, a detailed sensitivity analysis of the closed-loop performance metrics with respect to undesired changes and inherent uncertainty in system parameters is presented in this article. A comparison with the state-of-the-art (SOA) methods is provided, and conclusive results in terms of better dynamic performance are also established. To verify and elaborate on the specifics of the proposed scheme, a detailed simulation study is conducted, and the results show 25% reduction in response time as compared to SOA approaches. A 500-W boost PFC prototype is developed and tested with the proposed control scheme to evaluate and benchmark the system steady-state and dynamic performance. A total harmonic distortion of 1.68% is obtained at the rated load with a resultant power factor of 0.998 (lag), which proves the effectiveness and superiority of the proposed control scheme.

The accelerated penetration rate of renewable energy sources (RES) brings environmental benefits at the expense of increasing operation cost and undermining the satisfaction of the N-1 security criterion. To address the latter issue, this paper extends the state of the art, i.e. deterministic AC security-constrained optimal power flow (SCOPF), to capture two new dimensions: RES stochasticity and inter-temporal constraints of emerging sources of flexibility such as flexible loads (FL) and energy storage systems (ESS). Accordingly, the paper proposes and solves for the first time a new problem formulation in the form of stochastic multi-period AC SCOPF (S-MP-SCOPF). The S-MP-SCOPF is formulated as a non-linear programming (NLP). It computes optimal setpoints in day-ahead operation of flexibility resources and other conventional control means for congestion management and voltage control. Another salient feature of this paper is the comprehensive and accurate modelling: AC power flow model for both pre-contingency and post-contingency states, joint active/reactive power flows, inter-temporal resources such as FL and ESS in a 24-hours time horizon, and RES uncertainties. The applicability of the proposed model is tested on 5-bus (6 contingencies) and 60 bus Nordic32 (33 contingencies) systems.

Brushless synchronous generators (BSG) are typically used to produce an island network whose voltage is close to the nominal voltage of the generator. Generators are often used also in test-field applications where also zero output voltage is needed. The exciter construction and magnetic remanence may lead to a situation where the non-loaded generator terminal voltage cannot be controlled close to zero but a significant voltage is always generated because the exciter remanence. A new brushless synchronous generator excitation and de-excitation converter topology for test applications is proposed. The purpose is to achieve full voltage control from zero to nominal level without modifications to the generator. Insulated-gate bipolar transistor (IGBT) and Field-Programmable Gate Array (FPGA) technology are used to achieve the required fast and accurate control. In the work, simulation models were first derived to characterize the control performance. The proposed converter topology was then verified with the simulation model and tested empirically with a 400 kVA brushless synchronous generator. The results indicate that the exciter remanence and self-excitation can be controlled through the exciter stationary field winding when the proposed converter topology controls the field winding current. Consequently, in highly dynamical situations, the system is unaffected by mechanical stresses and wear in the generator.

As a part of the global decarbonization agenda, the electrification of the transport sector involving the large-scale integration of electric vehicles (EV) constitues one of the key initiatives. However, the introduction of EV loads results in more variable electrical demand profiles and higher demand peaks, challenging power system balancing, voltage and network congestion management. In this paper, a novel optimal load scheduling approach for a coupled power and transportation network is proposed. It employs an EV charging demand forecasting model to generate the temporal-spatial distribution of the aggregate EV loads taking into account the uncertainties stemmed from the traffic condition. An AC optimal power flow (ACOPF) problem is formulated and solved to determine the scheduling decisions for the EVs, energy storage units as well as other types of flexible loads, taking into account their operational characteristics. Convex relaxation is performed to convert the original non-convex ACOPF problem to a second order conic program. Case studies demonstrate the effectiveness of the proposed scheduling strategy in accurately forecasting the EV load distribution as well as effectively alleviating the voltage deviation and network congestion in the distribution network through optimal load scheduling control decisions.

This paper presents the results of a multifaceted study of the behavior of a novel hydrokinetic energy harvester that utilizes vertical oscillations. Unlike traditional rotating turbines used in hydrokinetic energy, this particular device utilizes the fluid structure interactions of vortex-induced-vibration and gallop. Due to the unique characteristics of this vertical motion, a thorough examination of the proposed system was conducted via a three-pronged approach of simulation, emulation, and field testing. Using a permanent magnet synchronous generator as the electrical power generation source, an electrical power conversion system was simulated, emulated, and tested to achieve appropriate power smoothing for use in microgrid systems present in many Alaskan rural locations.

The prevalence of Internet of Things (IoT) allows heterogeneous and lightweight smart devices to collaboratively provide services with or without human intervention. With an ever-increasing presence of IoT-based smart applications and their ubiquitous visibility from the Internet, user data generated by highly connected smart IoT devices also incur more concerns on security and privacy. While a lot of efforts are reported to develop lightweight information assurance approaches that are affordable to resource-constrained IoT devices, there is not sufficient attention paid from the aspect of security solutions against hardware-oriented attacks, i.e. side channel attacks. In this paper, a COTS (commercial off-the-shelf) based Randomized Switched-Mode Voltage Regulation System (RSMVRS) is proposed to prevent power analysis based side channel attacks (P-SCA) on bare metal IoT edge device. The RSMVRS is implemented to direct power to IoT edge devices. The power is supplied to the target device by randomly activating power stages with random time delays. Therefore, the cryptography algorithm executing on the IoT device will not correlate to a predictable power profile, if an adversary performs a SCA by measuring the power traces. The RSMVRS leverages COTS components and experimental study has verified the correctness and effectiveness of the proposed solution.

The continuous integration of intermittent low-carbon energy resources makes islanded microgrids vulnerable to voltage fluctuations. Besides, different dynamic response of synchronous-based and inverter-based distributed generation (DG) units can result in an instantaneous power imbalance between supply and demand during transients. As a result, the ac-bus voltage of microgrid starts oscillating which might have severe consequences such as blackouts. This paper modifies the conventional control scheme of battery energy storage systems (BESSs) to participate in improving the dynamic behavior of islanded microgrids by mitigating the voltage fluctuations. A piecewise linear-elliptic (PLE) droop is proposed and employed in BESS to achieve an enhanced voltage profile by injecting/absorbing reactive power during transients. In this way, the conventional inverter implemented in BESS turns into a smart inverter to cope with fast transients. Using the proposed approach in this paper, any linear droop curve with a specified coefficient can be replaced by a PLE droop curve. Compared with linear droop, an enhanced dynamic response is achieved by utilizing the proposed PLE droop. Case study results are presented using PSCAD/EMTDC to demonstrate the superiority of the proposed approach in improving the dynamic behavior of islanded microgrids.

The vulnerability of islanded microgrids to voltage and frequency variations is due to the presence of low-inertia distributed generation (DG) units. Besides, the considerable difference between the inertia of synchronous-based and inverter-based DGs results in a power mismatch between generation and consumption during abnormal conditions. As a result, both voltage and frequency of microgrid ac-bus start oscillating which might lead to blackouts. This paper deploys the traditional controller of photovoltaic (PV) units to improve the dynamics of islanded microgrids by reducing the voltage and frequency deviations. To this end, an adaptive piecewise droop (APD) curve is presented and implemented in PV units to attain a faster balance between supply and demand during transients, leading to an enhanced frequency response. Besides, the reactive-power control loop is equipped with a droop characteristic which enables the PV units to inject/absorb reactive power during transients and participate in voltage-profile enhancement of the system. Case study results are presented using PSCAD/EMTDC to confirm the validity of proposed method in improving the dynamic behavior of islanded microgrids.

This work adopts an online resiliency monitoring framework employing metric temporal logic (MTL) under cyber-physical anomalies, namely false-data injection attacks, denial-of-service attacks, and physical faults. Such anomalies adversely affect the frequency synchronization, load sharing, and voltage regulation in microgrids. MTL formalism is adopted to monitor the outputs of inverters/converters against operational bounds, detect and quantify cyber-physical anomalies, monitor the microgrid's resiliency during runtime, and compare mitigation strategies. Since the proposed framework does not require system knowledge, it can be deployed on a complex microgrid. This is verified using an IEEE 34-bus feeder system and a DC microgrid cluster in a controller/hardware-in-the-loop environment.

The Controller Area Network (CAN), a broadcasting bus for intra-vehicle communication, does not provide any security mechanisms, although it is implemented in almost every vehicle. Attackers can exploit this issue, transmit malicious messages unnoticeably and cause severe harm. As the utilization of Message Authentication Codes (MACs) is only possible to a limited extent in resource-constrained systems, the focus is put on the development of Intrusion Detection Systems (IDSs). Due to their simple idea of operation, current developments are increasingly utilizing physical signal properties like voltages to realize these systems. Although the feasibility for CAN-based networks could be demonstrated, the least approaches consider the constrained resource-availability of vehicular hardware. To close this gap, we present Voltage-Based Lightweight Intrusion Detection (VALID), which provides physics-based intrusion detection with low resource requirements. By utilizing solely the individual voltage levels on the network during communication, the system detects unauthorized message transmissions without any sophisticated sampling approaches and feature calculations. Having performed evaluations on data from two real vehicles, we show that VALID is not only able to detect intrusions with an accuracy of 99.54 %, but additionally is capable of identifying the attack source reliably. These properties make VALID one of the most lightweight intrusion detection approaches that is ready-to-use, as it can be easily implemented on hardware already installed in vehicles and does not require any further components. Additionally, this allows existing platforms to be retrofitted and vehicular security systems to be improved and extended.

In this paper, the Authors present MQTT (ISO/IEC 20922), coupled with Public-key Infrastructure (PKI) as being highly suited to the secure and timely delivery of the command and control messages required in a low-latency Automated Demand Response (ADR) system which makes use of domestic-level electrical loads connected to the Internet. Several use cases for ADR are introduced, and relevant security considerations are discussed; further emphasizing the suitability of the proposed infrastructure. The authors then describe their testbed platform for testing ADR functionality, and finally discuss the next steps towards getting these kinds of technologies to the next stage.

Compared with traditional centralized control strategies, the distributed control systems significantly improve the flexibility and expandability of an modular multilevel converter (MMC). However, the stability issue in the MMC distributed control system with the presence of control loop coupling interactions is rarely discussed in existing research works. This article is to improve the stability of an MMC distributed control system by inhibiting the control conflict due to the coupling interactions among control loops with incomplete control information. By modeling the MMC distributed control system, the control loop coupling interactions are analyzed and the essential cause of control conflict is revealed. Accordingly, a control parameter design principle is proposed to effectively suppress the disturbances from the targeted control conflict and improve the MMC system stability. The rationality of the theoretical analysis and the effectiveness of the control parameter design principle are confirmed by simulation and experimental results.

Series DC electric springs (DCESs) are a state-of-the-art demand-side management (DSM) technology with the capability to reduce energy storage requirements of DC microgrids by manipulating the power of non-critical loads (NCLs). As the stability of DC microgrids is highly prone to dynamic interactions between the system active and passive components, this study intends to conduct a comprehensive small-signal stability analysis of a community DC microgrid integrated with distributed DCESs considering the effect of destabilizing constant power loads (CPLs). For this purpose, after deriving the small-signal model of a DCES-integrated microgrid, the sensitivity of the system dominant frequency modes to variations of various physical and control parameters is evaluated by means of eigenvalue analysis. Next, an active damping control method based on virtual RC parallel impedance is proposed for series DCESs to compensate for their slow dynamic response and to provide a dynamic stabilization function within the microgrid. Furthermore, impedance-based stability analysis is utilized to study the DC microgrid expandability in terms of integration with multiple DCESs. Finally, several case studies are presented to verify analytical findings of the paper and to evaluate the dynamic performance of the DC microgrid.

Field-Programmable Gate Arrays (FPGAs) are versatile, reconfigurable integrated circuits that can be used as hardware accelerators to process highly-sensitive data. Leaking this data and associated cryptographic keys, however, can undermine a system's security. To prevent potentially unintentional interactions that could break separation of privilege between different data center tenants, FPGAs in cloud environments are currently dedicated on a per-user basis. Nevertheless, while the FPGAs themselves are not shared among different users, other parts of the data center infrastructure are. This paper specifically shows for the first time that powering FPGAs, CPUs, and GPUs through the same power supply unit (PSU) can be exploited in FPGA-to-FPGA, CPU-to-FPGA, and GPU-to-FPGA covert channels between independent boards. These covert channels can operate remotely, without the need for physical access to, or modifications of, the boards. To demonstrate the attacks, this paper uses a novel combination of "sensing" and "stressing" ring oscillators as receivers on the sink FPGA. Further, ring oscillators are used as transmitters on the source FPGA. The transmitting and receiving circuits are used to determine the presence of the leakage on off-the-shelf Xilinx boards containing Artix 7 and Kintex 7 FPGA chips. Experiments are conducted with PSUs by two vendors, as well as CPUs and GPUs of different generations. Moreover, different sizes and types of ring oscillators are also tested. In addition, this work discusses potential countermeasures to mitigate the impact of the cross-board leakage. The results of this paper highlight the dangers of shared power supply units in local and cloud FPGAs, and therefore a fundamental need to re-think FPGA security for shared infrastructures.

This paper presents a new micro-architectural vulnerability on the power management units of modern computers which creates an electromagnetic-based side-channel. The key observations that enable us to discover this sidechannel are: 1) in an effort to manage and minimize power consumption, modern microprocessors have a number of possible operating modes (power states) in which various sub-systems of the processor are powered down, 2) for some of the transitions between power states, the processor also changes the operating mode of the voltage regulator module (VRM) that supplies power to the affected sub-system, and 3) the electromagnetic (EM) emanations from the VRM are heavily dependent on its operating mode. As a result, these state-dependent EM emanations create a side-channel which can potentially reveal sensitive information about the current state of the processor and, more importantly, the programs currently being executed. To demonstrate the feasibility of exploiting this vulnerability, we create a covert channel by utilizing the changes in the processor's power states. We show how such a covert channel can be leveraged to exfiltrate sensitive information from a secured and completely isolated (air-gapped) laptop system by placing a compact, inexpensive receiver in proximity to that system. To further show the severity of this attack, we also demonstrate how such a covert channel can be established when the target and the receiver are several meters away from each other, including scenarios where the receiver and the target are separated by a wall. Compared to the state-of-the-art, the proposed covert channel has \textbackslashtextgreater3x higher bit-rate. Finally, to demonstrate that this new vulnerability is not limited to being used as a covert channel, we demonstrate how it can be used for attacks such as keystroke logging.

In this paper, the cybersecurity of distributed secondary voltage control of AC microgrids is addressed. A resilient approach is proposed to mitigate the negative impacts of cyberthreats on the voltage and reactive power control of Distributed Energy Resources (DERs). The proposed secondary voltage control is inspired by the resilient flocking of a mobile robot team. This approach utilizes a virtual time-varying communication graph in which the quality of the communication links is virtualized and determined based on the synchronization behavior of DERs. The utilized control protocols on DERs ensure that the connectivity of the virtual communication graph is above a specific resilience threshold. Once the resilience threshold is satisfied the Weighted Mean Subsequence Reduced (WMSR) algorithm is applied to satisfy voltage restoration in the presence of malicious adversaries. A typical microgrid test system including 6 DERs is simulated to verify the validity of proposed resilient control approach.

On-Load Tap Changing transformers are a widely used voltage regulation device. In the context of modern or smart grids, the control signals, i.e., the tap change commands are sent through SCADA channels. It is well known that the power system SCADA networks are prone to attacks involving injection of false data or commands. While false data injection is well explored in existing literature, attacks involving malicious control signals/commands are relatively unexplored. In this paper, an algorithm is developed to detect a stealthily introduced malicious tap change command through a compromised SCADA channel. This algorithm is based on the observation that a stealthily introduced false data or command masks the true estimation of only a few state variables. This leaves the rest of the state variables to show signs of a change in system state brought about by the attack. Using this observation, an index is formulated based on the ratios of injection or branch currents to voltages of the terminal nodes of the tap changers. This index shows a significant increase when there is a false tap command injection, resulting in easy classification from normal scenarios where there is no attack. The algorithm is computationally light, easy to implement and reliable when tested extensively on several tap changers placed in an IEEE 118-bus system.

This paper proposes a distributed fixed-time based secondary controller for the DC microgrids (MGs) to overcome the drawbacks of conventional droop control. The controller, based on a distributed fixed-time control approach, can remove the DC voltage deviation and provide proportional current sharing simultaneously within a fixed-time. Comparing with the conventional centralized secondary controller, the controller, using the dynamic consensus, on each converter communicates only with its neighbors on a communication graph which increases the convergence speed and gets an improved performance. The proposed control strategy is simulated in PLECS to test the controller performance, link-failure resiliency, plug and play capability and the feasibility under different time delays.

With the tighter integration of power system and Information and Communication Technology (ICT), power grid is becoming a typical cyber physical system (CPS). It is important to analyze the impact of the cyber event on power system, so that it is necessary to build a co-simulation system for studying the interaction between power system and ICT. In this paper, a cyber physical power system (CPPS) co-simulation platform is proposed, which includes the hardware-in-the-loop (HIL) simulation function. By using flexible interface, various simulation software for power system and ICT can be interconnected into the platform to build co-simulation tools for various simulation purposes. To demonstrate it as a proof, one simulation framework for real life cyber-attack on power system control is introduced. In this case, the real life denial-of-service attack on a router in automatic voltage control (AVC) is simulated to demonstrate impact of cyber-attack on power system.

The three-phase grid-connected converter control strategy, which applies to the battery energy storage system, generally ignores the interference of harmonic components in the grid voltage. As a result, it is difficult to meet the practical application requirements. To deal with this problem, it is necessary to optimize and improve the traditional control strategy, taking harmonics into consideration. And its bases are analysis of the harmonic characteristics and study of its control mechanism in the grid-connected converter. This paper proposes a method of harmonic decomposition, classifies the grid voltage harmonics and explores the control mechanism in the grid-connected converter. With the help of the simulation model built by Matlab/Simulink, the comparative simulation of the energy storage control system carried out under the control of the ideal grid voltage input and the actual one, verifies the correctness of the analytical method proposed in the article.

The traditional electricity distribution system is rapidly shifting from the passive infrastructure to a more active infrastructure, giving rise to a smart grid. In this project an active electricity distribution network and its components have been studied. A 14-node SCADA-based active distribution network model has been proposed for managing this emerging network infrastructure to ensure reliability and protection of the network The proposed model was developed using matlab /simulink software and the fuzzy logic toolbox. Surge arresters and circuit breakers were modelled and deployed in the network at different locations for protection and isolation of fault conditions. From the reliability analysis of the proposed model, the failure rate and outage hours were reduced due to better response of the system to power fluctuations and fault conditions.

Distributed Generation Photovoltaic Systems -DGPV - connected to the power distribution grid through electronic inverters can contribute, in an aggregate scenario, to the performance of several power system control functions, notably in self-healing and voltage regulation along a distribution feeder. This paper proposes the use of an optimization method for voltage regulation, focused on reactive power injection control, based on a comprehensive architecture model that coordinates multiple photovoltaic distributed sources to support grid reconfiguration after self-healing action. A sensitivity analysis regarding the performance of voltage regulation, based on a co-simulation of PSCAD and MatLab, shows the effectiveness of using dispersed generation sources to assist grid reconfiguration after disturbances caused by severe faults.

Aiming at the composite uncertainty characteristics and high-dimensional data stream characteristics of the evaluation index with both ambiguity and randomness, this paper proposes a emergency severity assessment method for cluster supply chain based on cloud fuzzy clustering algorithm. The summary cloud model generation algorithm is created. And the multi-data fusion method is applied to the cloud model processing of the evaluation indexes for high-dimensional data stream with ambiguity and randomness. The synopsis data of the emergency severity assessment indexes are extracted. Based on time attenuation model and sliding window model, the data stream fuzzy clustering algorithm for emergency severity assessment is established. The evaluation results are rationally optimized according to the generalized Euclidean distances of the cluster centers and cluster microcluster weights, and the severity grade of cluster supply chain emergency is dynamically evaluated. The experimental results show that the proposed algorithm improves the clustering accuracy and reduces the operation time, as well as can provide more accurate theoretical support for the early warning decision of cluster supply chain emergency.