Deqiang Gan

Bio: Deqiang Gan is an academic researcher from Zhejiang University. The author has contributed to research in topics: Electric power system & Electricity market. The author has an hindex of 28, co-authored 137 publications receiving 2663 citations. Previous affiliations of Deqiang Gan include Cornell University & ISO New England.

Stability-constrained optimal power flow

Abstract: Stability is an important constraint in power system operation. Often trial and error heuristics are used that can be costly and imprecise. A new methodology that eliminates the need for repeated simulation to determine a transiently secure operating point is presented. The theoretical development is straight-forward: dynamic equations are converted to numerically equivalent algebraic equations and then integrated into the standard OPF formulation. Implementation issues and simulation results are discussed in the context of a 162-bus system.

A New Frequency Regulation Strategy for Photovoltaic Systems Without Energy Storage

Abstract: To maximize the revenue from selling energy, photovoltaic systems (PVs) in general operate in the so-called maximum power point tracking mode. However, the increasing penetration of renewable energy sources in power systems has motivated the design of innovative control to provide ancillary services. The focus of this paper is to develop a new control strategy that enables PVs to adjust the active power outputs and provide frequency regulation to power systems. In this strategy, two different modes are designed: 1) the frequency droop control mode for PVs to provide primary frequency support to power systems, and 2) the emergency control mode to prevent system frequency collapse and, therefore, to prevent too much generation tripping after fault. Based on a detailed PV dynamic model, simulation results show the effectiveness of the proposed control strategy in improving the frequency stability.

Energy and reserve market designs with explicit consideration to lost opportunity costs

Abstract: The primary goal of this work is to investigate the basic energy and reserve dispatch optimization (cooptimization) in the setting of a pool-based market. Of particular interest is the modeling of lost opportunity cost introduced by reserve allocation. The authors derive the marginal costs of energy and reserves under a variety of market designs. They also analyze existence, algorithm, and multiplicity of optimal solutions. The results of this study are used to support the reserve market design and implementation in ISO New England control area.

A Distributionally Robust Co-Ordinated Reserve Scheduling Model Considering CVaR-Based Wind Power Reserve Requirements

Abstract: The reserve scheduling problem becomes more difficult to handle when wind power is increasing at a rapid rate in power systems and the complete information on the stochasticity of wind power is hard to be obtained. In this paper, considering the uncertainty on the probability distribution (PD) of the wind power forecast error (WPFE), a distributionally robust co-ordinated reserve scheduling (DRCRS) model is proposed, aiming to minimize the total procurement cost of conventional generation and reserve, while satisfying the security requirement over all possible PDs of WPFE. In this model, a distributionally robust formulation based on the concept of conditional value-at-risk (CVaR) is presented to obtain the reserve requirement of wind power. In addition, to achieve tractability of the scheduling model, the random variable that refers to WPFE in the scheduling model is eliminated, equivalently converting the stochastic model into a deterministic bilinear matrix inequality problem that can be effectively solved. Case studies based on the IEEE-39 bus system are used to verify the effectiveness of the proposed method. The results are compared with the normal distribution based co-ordinated reserve scheduling (NDCRS) method that assumes WPFE is of normal distribution.

Control of Island AC Microgrids Using a Fully Distributed Approach

Abstract: A fully distributed control scheme of island ac microgrids that can perform the primary, secondary, and tertiary control locally in distributed generators (DGs) is proposed. In the control scheme, no central controller or external information exchange is needed, while the final frequency can be controlled within the allowable range and the DGs can share loads according to their increment costs. The low-pass filters are designed to decouple the dynamics of the microgrid and to improve the system performance. Simulation studies verify the effectiveness of the control scheme.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

MATPOWER: Steady-State Operations, Planning, and Analysis Tools for Power Systems Research and Education

Abstract: MATPOWER is an open-source Matlab-based power system simulation package that provides a high-level set of power flow, optimal power flow (OPF), and other tools targeted toward researchers, educators, and students. The OPF architecture is designed to be extensible, making it easy to add user-defined variables, costs, and constraints to the standard OPF problem. This paper presents the details of the network modeling and problem formulations used by MATPOWER, including its extensible OPF architecture. This structure is used internally to implement several extensions to the standard OPF problem, including piece-wise linear cost functions, dispatchable loads, generator capability curves, and branch angle difference limits. Simulation results are presented for a number of test cases comparing the performance of several available OPF solvers and demonstrating MATPOWER's ability to solve large-scale AC and DC OPF problems.

Linear systems

Abstract: Most of the signal processing that we will study in this course involves local operations on a signal, namely transforming the signal by applying linear combinations of values in the neighborhood of each sample point. You are familiar with such operations from Calculus, namely, taking derivatives and you are also familiar with this from optics namely blurring a signal. We will be looking at sampled signals only. Let's start with a few basic examples. Local difference Suppose we have a 1D image and we take the local difference of intensities, DI(x) = 1 2 (I(x + 1) − I(x − 1)) which give a discrete approximation to a partial derivative. (We compute this for each x in the image.) What is the effect of such a transformation? One key idea is that such a derivative would be useful for marking positions where the intensity changes. Such a change is called an edge. It is important to detect edges in images because they often mark locations at which object properties change. These can include changes in illumination along a surface due to a shadow boundary, or a material (pigment) change, or a change in depth as when one object ends and another begins. The computational problem of finding intensity edges in images is called edge detection. We could look for positions at which DI(x) has a large negative or positive value. Large positive values indicate an edge that goes from low to high intensity, and large negative values indicate an edge that goes from high to low intensity. Example Suppose the image consists of a single (slightly sloped) edge:

Zero Duality Gap in Optimal Power Flow Problem

Abstract: The optimal power flow (OPF) problem is nonconvex and generally hard to solve. In this paper, we propose a semidefinite programming (SDP) optimization, which is the dual of an equivalent form of the OPF problem. A global optimum solution to the OPF problem can be retrieved from a solution of this convex dual problem whenever the duality gap is zero. A necessary and sufficient condition is provided in this paper to guarantee the existence of no duality gap for the OPF problem. This condition is satisfied by the standard IEEE benchmark systems with 14, 30, 57, 118, and 300 buses as well as several randomly generated systems. Since this condition is hard to study, a sufficient zero-duality-gap condition is also derived. This sufficient condition holds for IEEE systems after small resistance (10-5 per unit) is added to every transformer that originally assumes zero resistance. We investigate this sufficient condition and justify that it holds widely in practice. The main underlying reason for the successful convexification of the OPF problem can be traced back to the modeling of transformers and transmission lines as well as the non-negativity of physical quantities such as resistance and inductance.

Energy function analysis for power system stability

Abstract: (1990). ENERGY FUNCTION ANALYSIS FOR POWER SYSTEM STABILITY. Electric Machines & Power Systems: Vol. 18, No. 2, pp. 209-210.