Renewable Power Grid Research Articles

Stochastic small disturbance stability analysis of nonlinear multi-machine system with Itô differential equation

Abstract The stochastic small disturbance stability is widely recognized as a major issue in the small signal stability of power system due to complex stochastic factors such as increasing large-scale renewable power grid integration, random fluctuations of electrical loads and so on. By the relevant theories of Ito differential equation, this paper proposes a new method to prove the mean stability and mean square stability of the power angle and the angular speed of the nonlinear multi-machine system under small Gauss random disturbances. In this approach, the stability criterion is derived from the system. Simulation results of 4-machine 11-bus system and the 16-machine 68-bus system using MATLAB demonstrate that the proposed method is able to analyze the stochastic small disturbance stability with high effectiveness and accuracy compared with the theoretical proof, and it is suitable for any nonlinear multi-machine system. Based on the application of stochastic differential equation, the influence of intensity and quantity of the random disturbances on the stability of the system is further analyzed.

Reactive Power Management in Renewable Rich Power Grids: A Review of Grid-Codes, Renewable Generators, Support Devices, Control Strategies and Optimization Algorithms

Power electronic converter (PEC)-interfaced renewable energy generators (REGs) are increasingly being integrated to the power grid. With the high renewable power penetration levels, one of the key power system parameters, namely reactive power, is affected, provoking steady-state voltage and dynamic/transient stability issues. Therefore, it is imperative to maintain and manage adequate reactive power reserve to ensure a stable and reliable power grid. This paper presents a comprehensive literature review on the reactive power management in renewable rich power grids. Reactive power requirements stipulated in different grid codes for REGs are summarized to assess their adequacy for future network requirements. The PEC-interfaced REGs are discussed with a special emphasis on their reactive power compensation capability and control schemes. Along with REGs, conventional reactive power support devices (e.g., capacitor banks) and PEC-interfaced reactive power support devices (e.g., static synchronous compensators) play an indispensable role in the reactive power management of renewable rich power grids, and thus their reactive power control capabilities and limitations are thoroughly reviewed in this paper. Then, various reactive power control strategies are reviewed with a special emphasis on their advantages/disadvantages. Reactive power coordination between support devices and their optimal capacity are vital for an efficient and stable management of the power grid. Accordingly, the prominent reactive power coordination and optimization algorithms are critically examined and discussed in this paper. Finally, the key issues pertinent to the reactive power management in renewable rich power grids are enlisted with some important technical recommendations for the power industry, policymakers, and academic researchers.

Electricity Cost Minimization for Delay-tolerant Basestation Powered by Heterogeneous Energy Source

Recently, there are many studies, that considering green wireless cellular networks, have taken the energy consumption of the base station (BS) into consideration. In this work, we first introduce an energy consumption model of multi-mode sharing BS powered by multiple energy sources including renewable energy, local storage and power grid. Then communication load requests of the BS are transformed to energy demand queues, and battery energy level and worst-case delay constraints are considered into the virtual queue to ensure the network QoS when our objective is to minimize the long term electricity cost of BSs. Lyapunov optimization method is applied to work out the optimization objective without knowing the future information of the communication load, real-time electricity market price and renewable energy availability. Finally, linear programming is used, and the corresponding energy efficient scheduling policy is obtained. The performance analysis of our proposed online algorithm based on real-world traces demonstrates that it can greatly reduce one day’s electricity cost of individual BS.

An Experimental Fuzzy Inference System for Global Grid Electricity Peak Power Load Forecasting Third Core Module of First Console on G2P3S

Our World gives several symptoms of climate change. Devastating draughts increase (negative for World (-)), global mean temperature increase (-), lightning strikes increase (-), sea ice cover melt (-), tree mortality increase (-), and forest degradation increase (-) have been observed for decades. They are all negative measures for continuity of life. Diversity of species has been decreasing, so that life on Earth is dying. Only responsible specie for this situation is humankind. This study presents a small footstep to prevent this situation. Modeling of a 100% renewable power grid on World (Global Grid) is eminent. Annual peak power load (Gigawatt: GW, Kilowatt: kW) (peak demand or load) forecasting in power demand side is crucial for global grid modeling. This study presents an experimental fuzzy inference system for the third core module (100 years’ power demand forecasting) of the first console (long term prediction) of Global Grid Peak Power Prediction System (G2P3S). The inputs (world population, global annual temperature anomalies °C) and the output (annual peak power load demand of Global Grid in GW) are modeled with seven triangular fuzzy input membership functions and seven constant output membership functions. The constant Sugeno-Type fuzzy inference system is used in the current experimental model. The maximum absolute percentage error (MAP) is calculated as 45%, and the mean absolute percentage error (MAPE) is found as 39% in this experimental study. The MAP and MAPE of the first core module model (Type 1) were 0,46 and 0,36. The MAP and MAPE of the second core module model (Interval Type 2) were 0,46 and 0,36. As a result, this study is a good start for the third core module of the first console on Global Grid Peak Power Prediction System research, development, demonstration, & deployment (RD3) project. This experimental study also warns humankind in this subject. Hopefully, the most polluting societies on our World such as China, United States, India, Russia, Japan, Germany, South Korea, and Canada take urgent actions to start to build the foundations of 100% renewable power global grid by organizing a global grid consortium.

A Supervisory Power Management System for a Hybrid Microgrid With HESS

This paper proposes a supervisory power management system (PMS) for a grid interactive microgrid with a hybrid energy storage system. The key feature of the proposed PMS is reduced number of sensors required to implement the PMS. The PMS considers renewable power variation, grid availability, electricity pricing, and changes in local loads. It can detect the operating mode of system without measuring load currents and powers. A single-phase voltage source converter (VSC) transfers real power between dc grid and utility grid besides offering ancillary services such as harmonic mitigation, reactive power support, and unity power factor at the point of common coupling (PCC). In the proposed system, a better dc-link voltage regulation is achieved and the usage of supercapacitors reduces the current stress on the battery. The PMS also addresses extreme operating conditions such as load shedding, off-maximum power point tracking operation of photovoltaic, elimination of critical oscillation of hybrid energy storage systems power, islanded operation, and resynchronization with grid. The performance of the proposed PMS is verified by digital simulation and experimental studies.

G<sup>2</sup>EDPS's First Module & Its First Extension Modules

100% renewable worldwide power grid (Global Grid) system needs a Global Grid Electricity Demand Prediction System (G²EDPS) with very short, short, medium and long term forecasting consoles. This paper presents the 1^st core module and its 10 extension modules in the long term prediction console. A type 1 Mamdani like Fuzzy Inference System (FIS) with 7 triangle membership functions and 49 rules is designed for 2 input and 1 output variables for a 100 year forecasting period. The maximum absolute percentage errors (MAP), the mean absolute percentage errors (MAPE), and the Symmetric MAPE (SMAPE) of the best core module and its extension modules are respectively 0, 24; 0, 08; 0, 05 and 0, 22; 0, 07; 0, 05.

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

The Blue LED Nobel Prize: Historical context, current scientific understanding, human benefit

Experimental demonstration and application planning of high temperature superconducting energy storage system for renewable power grids

Abstract Since high temperature superconducting magnetic energy storage system (HT SMES) has attracted significant attention for their fast response in milliseconds, high efficiency (cyclic efficiency over 95%) and unlimited times of charging and discharging cycles, it can be used for system stabilizing – damping out low frequency power oscillations. A voltage source converter (VSC) based HTS SMES has been optimal designed for achieving a high efficiency and has been constructed by China Electric Power Research Institute (CEPRI). This SMES can store the maximum energy, while for the first time used two states of art high temperature superconductors, YBCO and BSCCO tapes. It has been tested in a 110 kV transmission power system by a dynamic power fluctuation compensation experiment using three different controlling strategies in CEPRI. The experimental output powers with these three strategies are compared and the results show that the SMES can trace the power variation and provide the required power to restrain the power fluctuation in milliseconds successfully. Finally, the application planning of SMES with the equivalent capacity in a practical renewable power system at Zhangbei wind power test base is evaluated by a case study based on the PSCAD/EMTDC simulation. An optimal switch time of the SMES in wind power system is presented using the real transmission parameters of Zhangbei power grid. This study can provide a reference for the demonstration of large-scale SMES systems in renewable power system.

动态能量获取下无线通信的能量管理与资源优化

Due to the advantages of environment friendliness, easy and flexible deployment, utilizing renewable energy for wireless communications has attracted extensive attention recently. Since the renewable energy is not stable, and the capacity of batteries is limited, it is hard to predict and optimize the utilization of the energy for transmission. The double-randomness due to energy arrival and channel variation makes it a challenging job to efficiently exploit renewable energy for wireless communications. This article reviews the current research status, based on which the authors provide some insights on how to perform energy management and resource optimization for wireless communications under dynamic energy harvesting. Moreover, the authors introduce some initial results on the power allocation for a wireless communication link driven by both renewable energy and power grid. Particularly, the offline optimal power allocation policy is derived, and the extension to online algorithms is discussed.

A Design Methodology for Smart LED Lighting Systems Powered By Weakly Regulated Renewable Power Grids

The increasing use of intermittent renewable energy sources to decarbonize electric power generation is expected to introduce dynamic instability to the mains. This situation is of particular concern for mini-grids or isolated grids in which wind and/or solar power sources are the dominant or the sole power sources. In this paper, we utilize the photo-electro-thermal theory to develop a design methodology for LED lighting systems for weakly regulated voltage sources, with the objectives of minimizing the fluctuation of the human luminous perception and adopting reliable LED driver with long lifetime and robustness against extreme weather conditions. The proposed LED system, practically verified in a 10 kVA small power grid driven by an ac voltage source and a wind energy simulator, can be considered as a smart load with its load demand following the power generation. A typical swing of 40 V in the mains will cause only 15% actual light variation in a 132 W LED system when compared with 40% change in 150 W high-pressure-sodium lamp system. The design methodology enables future large-scale LED systems to be designed as a new generation of smart loads that can adapt to the voltage and power fluctuations arising from the intermittent nature of renewable energy sources.