1,512 research outputs found

    Ancillary Services in Hybrid AC/DC Low Voltage Distribution Networks

    Get PDF
    In the last decade, distribution systems are experiencing a drastic transformation with the advent of new technologies. In fact, distribution networks are no longer passive systems, considering the current integration rates of new agents such as distributed generation, electrical vehicles and energy storage, which are greatly influencing the way these systems are operated. In addition, the intrinsic DC nature of these components, interfaced to the AC system through power electronics converters, is unlocking the possibility for new distribution topologies based on AC/DC networks. This paper analyzes the evolution of AC distribution systems, the advantages of AC/DC hybrid arrangements and the active role that the new distributed agents may play in the upcoming decarbonized paradigm by providing different ancillary services.Ministerio de Economía y Competitividad ENE2017-84813-RUnión Europea (Programa Horizonte 2020) 76409

    Provision of ancillary services by renewable hybrid generation in low frequency AC systems to the grid

    Get PDF
    Wind energy high penetration levels in power systems lead to continuous power imbalance due to the intermittent nature of wind power. This paper proposes and investigates different methods to enable a hybrid generation system to provide frequency support to the grid. The hybrid generation is 100% renewable and composed of a wind farm and hydropower plant (HPP) of comparable generation capacities, and they are interconnected through a Low Frequency AC system (LFAC). The grid–tie is composed of a Voltage-Source Converter based High-Voltage, Direct Current (VSC-HVDC) junction that acts as frequency changer to maintain the grid nominal frequency. The HPP provides two types of ancillary services: wind power smoothing and frequency drops mitigation to avoid the use of thermal generation and battery energy storage. The paper offers different control methods to provide the two AS with improved coordination between the different controls in the hybrid generation system and complying with the common requirements of Grid Codes. The results obtained show that the frequency at the LFAC can tolerate mild drops to provide frequency support to the grid. The controllers’ parameters have a clear impact on the frequency response at both systems. Simulation environment is MATLAB and Simulink

    A Robust Frequency Control Approach in PV-Diesel Hybrid Power System

    Get PDF
    Hybrid power generation system such as photovoltaic (PV)-diesel is one of the solution to reduce operational cost of the conventional diesel generation system. However, fluctuation of PV power due to uncertainty in weather condition may generate an unstable frequency of system. Further, it may reduce the reliability of the power utility, especially when the penetration of PV power is large. Therefore, a frequency control approach that involving PV with battery supervised by neural network algorithm is proposed to generate a stable system frequency. This method can reduce the frequency deviation without smoothing PV output power. The PV panels can generate maximum power according to the weather condition and frequency deviation. The PV output power and battery output power is controlled by neural network algorithm control. The neural network algorithm control is considering frequency deviation, average insolation and change of insolation as input. The proposed method is compared with similar system but without the existence of battery as energy storage system. The simulation results show that the proposed method can generate small frequency deviation compared with system without battery

    Integrating photovoltaic systems into remote diesel generator powered networks

    Get PDF
    This thesis aims to research the effects of multiple ascending levels of photovoltaic (PV) power penetration on a prototype diesel generator powered network that has a PV power system integrated into it. First the effects of this additional photovoltaic penetration were documented then some ways to mitigate the effects of solar intermittency were investigated. This project relates to the Power and Water Corporation’s (PWC) proposed roll out of 10 megawatt of solar throughout more than 30 of the remote communities they service in the Northern Territory. This thesis is concerned with instantaneous PV power penetration and studying the effects levels of instantaneous penetration higher than 30 per cent may have on an individual network. To conduct this study, literature about solar irradiance data and previous trials in the Northern Territory was studied to make sensible simulation event estimates for a mock network. A network model was created and used in simulations to approximate the network’s response to cloud shading during various levels of penetration. The simulations confirmed that photovoltaic penetration of 30 per cent and even 45 per cent could easily be implemented without the need for upgrading the existing infrastructure. Both 60 and 70 per cent penetration level simulations suggested that there would likely be a need to raise the nominal generated voltage and or apply shunt capacitor banks to the load buses. The significance of these results is that they confirm the Power and Water Corporations premise that 30 per cent penetration is a safe starting point and also suggest that higher levels of photovoltaic penetration can be achieved with little to no costly infrastructure upgrades, depending on the level of penetration implemented

    Power systems with high renewable energy sources: A review of inertia and frequency control strategies over time

    Get PDF
    Traditionally, inertia in power systems has been determined by considering all the rotating masses directly connected to the grid. During the last decade, the integration of renewable energy sources, mainly photovoltaic installations and wind power plants, has led to a significant dynamic characteristic change in power systems. This change is mainly due to the fact that most renewables have power electronics at the grid interface. The overall impact on stability and reliability analysis of power systems is very significant. The power systems become more dynamic and require a new set of strategies modifying traditional generation control algorithms. Indeed, renewable generation units are decoupled from the grid by electronic converters, decreasing the overall inertia of the grid. ‘Hidden inertia’, ‘synthetic inertia’ or ‘virtual inertia’ are terms currently used to represent artificial inertia created by converter control of the renewable sources. Alternative spinning reserves are then needed in the new power system with high penetration renewables, where the lack of rotating masses directly connected to the grid must be emulated to maintain an acceptable power system reliability. This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values. A comparison of the rotational grid inertia for traditional and current averaged generation mix scenarios is also carried out. In addition, an extensive discussion on wind and photovoltaic power plants and their contributions to inertia in terms of frequency control strategies is included in the paper.This work was supported by the Spanish Education, Culture and Sports Ministry [FPU16/04282]

    Large Grid-Connected Wind Turbines

    Get PDF
    This book covers the technological progress and developments of a large-scale wind energy conversion system along with its future trends, with each chapter constituting a contribution by a different leader in the wind energy arena. Recent developments in wind energy conversion systems, system optimization, stability augmentation, power smoothing, and many other fascinating topics are included in this book. Chapters are supported through modeling, control, and simulation analysis. This book contains both technical and review articles

    Energy Management Control for Multimode Microgrid Renewable Integration

    Get PDF
    The need for storing energy has grown in correlation with the need for renewable and distributed energy resources. Designing a storage unit system which complements the distributed generation is required for increased efficiency and reducing the burden on the utility grid. The energy storage model used in this thesis is the Li-ion battery which is efficient, has high energy density and has applications in field of electronics, transportation and electric power industry. The wind turbine generator, photovoltaic (PV) and the energy storage unit modeled in this work share a symbiotic relationship even though they are completely separate entities which can be connected at separate locations. This study contributes better control as well as ease of connection to the system. To show the effect of storage unit on microgrid distribution system two test systems were considered, standalone system and standard IEEE 13 node feeder system with wind turbine generator and photovoltaic panel. The integration and control of energy storage system is achieved using a battery energy management control (BEMC) at the upper level and a real/reactive power controlled voltage source converter at the lower level. To enhance the control, optimization is performed where the proportional gain and the integral time constant of the PI controller are optimized using genetic algorithm which reduces the losses and increases the efficiency of the system. The results show that the battery energy management control system is effective in controlling the modes of operation of energy storage module based on the wind and solar conditions and is able to completely balance the power produced by the wind generator and PV modules. In this thesis all the test systems and the control were implemented in PSCAD as it is emerging as the new industry standard for transient power applications research

    Short-term energy storage for power quality improvement in weak MV grids with distributed renewable generation

    Get PDF
    The intermittent and stochastic nature of renewable energy sources impose several challenges for the operation of electrical networks, and affect power quality levels as well. This paper addresses one of the issues associated to power quality in electrical networks: voltage flicker. The main contribution of the paper fall in the proposal of a methodology for addressing the location in the network and the sizing of an active filter for flicker filtering. The designed active filter is based on controllable and bidirectional power electronics. Also, it includes energy storage capability, so as to maximize flicker filtering effectiveness by performing both active and reactive power regulation.Postprint (author's final draft

    Power-Smoothing Scheme of a DFIG Using the Adaptive Gain Depending on the Rotor Speed and Frequency Deviation

    Get PDF
    In an electric power grid that has a high penetration level of wind, the power fluctuation of a large-scale wind power plant (WPP) caused by varying wind speeds deteriorates the system frequency regulation. This paper proposes a power-smoothing scheme of a doubly-fed induction generator (DFIG) that significantly mitigates the system frequency fluctuation while preventing over-deceleration of the rotor speed. The proposed scheme employs an additional control loop relying on the system frequency deviation that operates in combination with the maximum power point tracking control loop. To improve the power-smoothing capability while preventing over-deceleration of the rotor speed, the gain of the additional loop is modified with the rotor speed and frequency deviation. The gain is set to be high if the rotor speed and/or frequency deviation is large. The simulation results based on the IEEE 14-bus system clearly demonstrate that the proposed scheme significantly lessens the output power fluctuation of a WPP under various scenarios by modifying the gain with the rotor speed and frequency deviation, and thereby it can regulate the frequency deviation within a narrow range
    corecore