The Editorial Board of the IEEE Transactions on Power Systems would like to recognize the following high quality papers published from 2018 through 2020:

This letter presents a novel optimization framework of formulating the three-phase optimal power flow that involves uncertainty. The proposed uncertainty-aware optimization (UaO) framework is: 1) a deterministic framework that is less complex than the existing optimization frameworks involving uncertainty, and 2) convex such that it admits polynomial-time algorithms and mature distributed optimization

Frequency security is an essential issue in power system operation and planning, especially with the increasing penetration level of intermittent and non-synchronous energy sources, which causes insufficiency of inertial and primary frequency responses. Therefore, various studies must observe the frequency security in the problem formulation as objective function and/or constraints. This letter proposes

Presents corrections to the above named paper.

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IEEE Transactions on Power Delivery IEEE Transactions on Power Systems Joint Special Section on Hybrid AC/DC Transmission Grids HVDC technology has brought many advantages to power transmission. Examples are increased flexibility in operation, expanded power transfer capability and easier interconnection of energy sources. However, HVDC links need to be built along existing AC transmission grids. It

In this letter, we present an alternative mixed-integer non-linear programming formulation of the reactive optimal power flow (ROPF) problem. We utilize a mixed-integer second-order cone programming (MISOCP) based approach to find global optimal solutions of the proposed ROPF problem formulation. We strengthen the MISOCP relaxation via the addition of convex envelopes and cutting planes. Computational

Traditionally, load forecasting models are trained offline and generate predictions online. However, the pure batch learning approach fails to incorporate new load information available in real-time. Conversely, online learning allows for efficient adaptation of newly incoming information. This letter advocates a novel online ensemble learning approach for load forecasting by combining batch and online

As the penetration of utility-scale solar photovoltaic (PV) power plants increases, the inertia in the system is reduced and there will be increased primary frequency response requirements. To increase inertia and improve the primary frequency response, grid-forming inverters connecting PV to grid and energy storage systems (ESSs) may play an important role. Moreover, high-voltage direct current (HVdc)

Low-frequency high-voltage alternating-current (LF-HVac) transmission scheme has been recently proposed as an alternative solution to conventional 50/60-Hz HVac and high-voltage direct-current (HVdc) schemes for bulk power transfer. This paper proposes an optimal planning and operation for loss minimization in a multi-frequency HVac transmission system. In such a system, conventional HVac and LF-HVac

Presents an index of the authors whose articles are published in the conference proceedings record.Presents an index of the authors whose articles are published in the conference proceedings record.

Among other things, in a detailed analysis of circumstances in power systems of great importance is the knowledge on contribution of individual generators to loads, and to currents and power losses in network elements. This work proposes an efficient method for obtaining these details. The method uses results of a power flow calculation, utilizes specific power system model, and applies the superposition

Semidefinite Programming (SDP) is a powerful technique to compute tight lower bounds for Optimal Power Flow (OPF) problems. Even using clique decomposition techniques, semidefinite relaxations are still computationally demanding. However, there are many different clique decompositions for the same SDP problem and they are not equivalent in terms of computation time. In this paper, we propose a new

We analyze the effect of DC lines on the controllability of AC power networks. We study the spectra of the controllability Gramian as a function of the addition of DC lines. We show that the trace of the controllability Gramian, which represents average controllability, is maximized when DC lines link node pairs with large effective reactance in the AC network.

The precise fluid and gas energy flow equations (FEFEs) are difficult to formulate due to the uncertain parameters. This paper proposes a data-driven approach to fit the FEFEs by polynomial functions through experimental data. Furthermore, a convex optimization model is set up to find the solution of the FEFEs, and a tight reformulation is proposed to exactly reformulate the proposed model as a second-order

We propose novel line outage distribution factors under AC power flow (AC-LODF) for providing very efficient approximate post-outage power flow solution. The AC-LODF is derived by using holomorphic embedding (HE) approach, and the approximate post-outage power flow solution is obtained with Padé approximation (PA). Tests on IEEE 14-bus system, and Polish 2383-bus system verify that the proposed AC-LODF

Chance-constrained program (CCP) is a popular stochastic optimization method in power system planning, and operation problems. Conditional Value-at-Risk (CVaR) provides a convex approximation for chance constraints which are nonconvex. Although CCP assumes an exact empirical distribution, and the optimum of a stochastic programming model is thought to be sensitive in the designated probability distribution

Second-order generalized integrator (SOGI)-based phase-locked loops (PLLs)/frequency-locked loops (FLLs) are the most commonly used methods for grid synchronization. While the SOGI in these standard SOGI-PLLs/FLLs is adaptive to the estimated frequency, which results in the coupling between the SOGI and PLL/FLL, and this coupling brings about difficulties in stability analysis and parameter tuning

Phase-locked loop (PLL) control provides a typical synchronization mechanism for voltage-source converters (VSCs) integrated into strong grids. However, such a synchronization mechanism is hardly adaptive to the high-impedance weak grid neither to the islanded grid. In the scope of low-inertia weak grid issues, additional frequency control is conceived as an effective way for VSC-based devices to improve

In this work we address the problem of short-term load forecasting. We propose a generalization of the linear state-space model where the evolution of the state and the observation matrices is unknown. The proposed blind Kalman filter algorithm proceeds via alternating the estimation of these unknown matrices and the inference of the state, within the framework of expectation-maximization. A mini-batch

Despite it is essential to distribution network economics, computing energy loss for most major networks is still a tough task due to the absence of full monitoring. Assume the line current follows a normal distribution, the sum of its square is a linear combination of independent chi-square variables, which follows a generalized noncentral chi-square distribution. Based on this finding, we develop

Skewness can be used to identify the asymmetry introduced into a current stream by a High Impedance Fault (HIF). This letter introduces relative skewness as a superior computational approach for detecting HIF induced asymmetry changes in the feeder current. Relative skewness is defined as a measure of asymmetry in the stream with respect to the stream itself. The key highlight is the analysis of four

A novel concurrent control scheme of optimal re/active power regulation in a wind farm is proposed in this letter, of which the objective is to minimize the detrimental shortfall of active power during low-voltage-fault events. Distinguished from the existing works, the proposed control scheme incorporates an efficient optimization module into the wind turbine controllers. Specifically, it features

Recently, several authors have reported specific criteria to support the widely accepted use of a convex operational model for bulk energy storage in the formulation of power system operation and planning problems involving binary variables. Using two counterexamples, we show that this modeling simplification may give rise to impractical solutions featuring simultaneous charging and discharging, even

The letter proposes an algorithm for big data generation based on realistic selection of a set of contingencies for power systems described by undirected graphs. Every contingency is created by eliminating a certain number of elements in the system represented by graph edges. The number of elements as well as the distance between elements of the contingency is randomly selected according to a geometric

The fundamental mechanism of transient stability of the conventional power system can be physically understood with the rotor swing dynamics of synchronous generators (SGs). The basic factor affecting the transient stability is the power-angle relationship among the SGs. The integration of a large number of inverter-based generations (IBGs) into the power system inevitably changes the original power-angle

Hybrid AC/DC networks are an effective solution for future power systems, due to their ability to combine advantages of both AC and DC networks. However, they bring new technological challenges, one key area being the control of such a network. The network, and especially the interlinking converter (ILC), must be controlled to ensure that the DC and AC subsystems coordinate to stabilize the network

In this letter, we present a novel Gaussian Process Learning-based Probabilistic Optimal Power Flow (GP-POPF) for solving POPF under renewable and load uncertainties of arbitrary distribution. The proposed method relies on a non-parametric Bayesian inference-based uncertainty propagation approach, called Gaussian Process (GP). We also suggest a new type of sensitivity called Subspace-wise Sensitivity

This paper presents a distributed supplementary control for embedded Multi-Terminal VSC-HVDC (MTDC) grids to enhance the transient stability of the surrounding AC grid. Firstly, the need of supplementary controllers for embedded MTDC grids is demonstrated via the study of the Transient Energy Functions (TEF) of a simple hybrid AC/DC power system. Then, the proposed control structure is presented. This

Maintaining good quality of transient stability models for power system planning and operational analysis is of great importance. Identification and calibration of bad parameters using PMU measurements that work well for multiple events remains a challenging problem. In this letter, we present a novel parameter calibration method based on off-policy deep reinforcement learning (DRL) algorithm with

When the shunt elements in the $\Pi$ circuit line model are assumed zero, it has been proved that branch flow models are equivalent to bus injection models and that the second-order cone relaxation of optimal power flow problems on a radial network is exact under certain conditions. In this note we propose a branch flow model that includes nonzero line shunts and prove that the equivalence and the

The power flow problem is an indispensable tool to solve many of the operation and planning problems in the electric grid and has been studied for the last half-century. Currently, popular algorithms require second-order methods, which may lead to poor performance when the initialization points are poor or when the system is stressed. These conditions are becoming more common as both the generation

The global optimum of the optimal power flow (OPF) problem can be sought in various practical settings by adopting the conic relaxations, such as the second order cone programs (SOCPs) and semi-definite programs (SDPs). However, the ZIP (constant impedance, constant current, constant power) and exponential load models are not directly amenable with these conic solvers. Thus, these are mostly treated

We reexamine and critique the classical area control error concept used in automatic generation control, and propose a new error signal termed the area injection error. Unlike the ACE, the AIE uses direct measurement of generator power levels, yielding improved AGC performance in the presence of bias uncertainty and nonlinearity in generator turbine-governor responses. As a by-product of our analysis

This paper presents a Synchronized Phasor Measurement Unit (PMU) based controller to support the coordination and operation of a high-capacity high-voltage direct current (HVDC) macrogrid transmission for the continental US. The proposed controller allows for optimal scheduling of each segment of the multi-terminal HVDC network under normal and contingent conditions, while considering minimum levels

With the mushrooming of distributed renewable generation, energy storage unit (ESU) is becoming increasingly important in residential energy systems. This letter proposes a fractional programming model to determine the optimal power, and energy capacities of residential ESUs. The objective function maximizes the ratio between the reduced electricity tariff, and the investment cost of ESU, ensuring

This letter proposes a new way for including hard limits associated with control devices in the formulation of the transient stability problem. The inequality constraints representing hard limits are transformed into a set of equality constraints by using the concept of complementarity constraints and the Fisher-Burmeister merit function. This set of constraints are added to the rest of the equations

Convergence bidding (CB), a.k.a., virtual bidding (VB), is a market mechanism facilitated by Independent System Operators (ISOs) in wholesale electricity markets to help lower the gap between the prices in the day-ahead market (DAM) and prices in the real-time market (RTM). In this paper, we seek to answer two questions: 1) how can a strategic market participant maximize its profit when submitting

This paper proposes a new distributed dispatch scheme to realize efficient coordinated real-time dispatch of the coupled transmission grid and active distribution grids (ADGs). In the proposed scheme, on the one hand, the concept of optimal power exchange interval is introduced to coordinate the transmission grid and ADGs so that the reserve capacity support from ADGs can be incorporated in the dispatch

Sudden occurrence of a large forced oscillation (FO) is a challenging problem for power system operators, especially when the forced oscillation is resonating with a natural system mode. Among the methods for oscillation source location, the energy flow method has shown promise for detecting the source of a natural oscillation as well as a forced oscillation. In this paper, we analyze the performance

Combined heat, and power dispatch promotes interactions, and synergies between electric power systems, and district heating systems. However, nonlinear, and nonconvex heating flow imposes significant challenges on finding qualified solutions efficiently. Most existing methods rely on constant flow assumptions to derive a linear heating flow model, sacrificing optimality for computational simplicity

Grid interconnected multi-microgrids provides potential benefits to the consumers, where the microgrids (MGs) equipped with distributed generators (DGs), energy storage systems (ESSs), and diesel generators. However, intermittency of DGs, high cost of ESSs, and depleting fossil fuels are the major challenges for the economic operation of interconnected multi-microgrids. One potential way to address

In the face of extreme events, e.g., hurricanes, the transmission systems, especially the transmission lines, are affected across time and space. To mitigate these impacts on the day-ahead market from a probabilistic perspective, a resilient unit commitment (UC) problem is formulated as a two-stage distributionally robust and robust optimization (DR&RO) problem. In the first stage, the commitment,

Topology identification (TI) is a key task for state estimation (SE) in distribution grids, especially the one with high-penetration renewables. The uncertainties, initiated by the time-series behavior of renewables, will almost certainly lead to bad TI results without a proper treatment . These uncertainties are analytically intractable under conventional framework—they are usually jointly spatial-temporal

Forced oscillations in power systems can lead to disruptive large oscillations across the grid when resonating with inter-area system modes. This letter proposes a rigorous method for estimating the overall impact of a forced oscillation when the forced oscillation frequency is close to the frequencies of multiple system modes. Apart from providing analytical insight, the method is shown to be useful

Accurate estimates of the electromechanical disturbance propagation in a power system play an important role in taking preventive, corrective, and in-extremis control actions. This paper proposes an analytical method for disturbance propagation investigation based on the electromechanical wave theory. A frame structure model is developed that allows us to derive an analytical relationship between the

This paper proposes a novel method for the machine learning-based online prediction of generator dynamic behavior in large interconnected power systems. Unlike the existing literature in this domain, which assumes faults occur immediately after a steady-state situation, the proposed method takes the possibility of multiple disturbances into account. It is founded on a simulation-based classification

The flexibility provided by High Voltage Direct Current (HVDC) systems can be further extended by Wide Area Monitoring, Protection, and Control (WAMAPC) systems. WAMPAC systems enable many HVDC applications and, on the other hand, inevitably introduce cybersecurity concerns that need to be addressed. In this work, a security domain layer and decision framework is reported to detect and mitigate the

This paper presents a mathematical analysis of how wind generation impacts the slow coherency property of power systems. Slow coherency arises from time-scale separation in the dynamics of synchronous generators, where generator states inside a coherent area synchronize over a fast time-scale due to stronger coupling, while the areas themselves synchronize over a slower time-scale due to weaker coupling

In this paper, we investigate whether and under which conditions jointly owning a variable renewable source of electricity (VRES) and an electricity storage generates economies of scope in competitive electricity markets. Using a simple stochastic optimization model that assumes frictionless markets, we analytically show that no economic benefit arises from combining the two assets. This finding is

In a multi-regional interconnected grid, the probabilistic load flow (PLF) of any region cannot be calculated individually but should consider the uncertainties introduced in other areas. Accordingly, the topologies, loads, and generations of every region are needed. Although the renewable generation data could be assumed as publicly known, some regional independent system operators (ISOs) still would

This paper studies the optimal clearing problem for prosumers in peer-to-peer (P2P) energy markets. It is proved that if no trade weights are enforced and the communication structure between successfully traded peers is connected, then the optimal clearing price and total traded powers in P2P market are the same with that in the pool-based market. However, if such communication structure is unconnected

The maximum active power that a Line-Commutated-Converter High Voltage Direct Current (LCC-HVDC) can provide instantly, called LCC-HVDC-MC Maximum Emergency Power Capacity, is an important information for determining the emergency control strategy of a power system subject to a large disturbance. However, it is a challenging task to calculate this capacity accurately due to system model uncertainties

The identification of generator coherency is crucial to design intentional controlled power system islanding. Due to high penetration of nonsynchronous generation, power system inertia changes both temporally and spatially. Thus, the dynamics in system oscillations and associated slow coherency of generators are directly affected by this. Therefore, their sensitivity deserves investigation. In this

In 2011, the Federal Energy Regulatory Commission (FERC) mandated that demand response (DR) procurement pass a net benefits test (NBT) in Order 745 to ensure that the benefits outweighed the costs. Without NBT, DR procurement could result in losses to consumers considering payments for energy and DR services. Current NBT implementations are monthly. However, this neglects to consider two important

Traditional cyberattack strategies on the electricity market only consider bypassing bad data detections. However, our analysis shows that experienced market operators can detect abnormal locational marginal prices (LMPs) under the traditional attack model during real-time (RT) operations, because such attack model ignores the characteristics of the LMP itself and leads to price spikes that can be

Presents closure discussion to the above named paper.

Reactive power reserves are important for grid stability and have a variety patterns depending on fault location as power systems become larger and complex. This paper presents the clustered effective reactive reserve (CEQR), an indicator that is suitable for identifying the risk of dynamic voltage stabitlity in terms of power system operation. This indicator provides the following features: i) It

Microgrids play a pivotal role in the attempts to achieve universal access to electricity; hence, their accurate planning, which also includes the evolution of the system over the project lifetime, is essential for maximizing the profitability of the investments. This paper proposes an iterative multi-year mixed-integer linear programming (MILP) optimization, in which power-dependent efficiency and

A power system with a large number of wind farms may consist of several thousand or more wind turbine generators (WTGs). Owing to the high dimension of the linearized model of such a power system, applying conventional modal analysis may be impossible due to the numerical complexity. This study proposes a reduced-order method of modal analysis to detect the risk and trace the sources of oscillatory