Global Dynamic Response of a Medium-Sized Floating Offshore Wind Turbine with Stall Regulation

In this paper, a two-bladed medium-sized floating wind turbine with variable speed and power regulation by stall is studied. For floating offshore wind turbines, the major challenges are related to the dynamical behavior of the system in response to combined wind and wave loading. Especially for smaller systems, the coupling of aerodynamic and wave forces may lead to large amplitude motions. Coupled aero-hydro-servo-elastic simulations are carried out in OpenFAST. The goal of the study is to investigate the global dynamic response of the hypothetical wind turbine with stall regulation. Stall regulation concept is proposed and the structural loads are computed and results are presented and discussed.

Carbon Emissions and Renewables’ Share in the Future Iberian Power System

The main objective of this study is to assess if the targets set by the European Commission (EC) relating to the share of renewables and CO2 emissions by 2030 will be accomplished by the Iberian power system. In this regard, several projections for each generation technology’s installed capacity in the future power system are identified. These forecasts were issued by governmental and private Iberian organizations and by the European Association of Transmission System Operators (ENTSOE), the latter with three scenarios regarding the speed of the energy transition. The outputs of the study are extended to the 2040 horizon and include the energy generated by each technology, the CO2 emissions, the costs involved in the decarbonization, and the storage capacity needed to compensate for the renewables’ variability. The conclusion is that the Iberia peninsular is on the right path to achieve a fully decarbonized power system by 2040, outperforming by far the EC’s targets in 2030 if the governmental projections are followed. A significant capacity of storage options is envisaged to compensate for the variability of generation from renewables and to replace the power regulation services provided by the fossil fuel plants that will be shut down.

Supervisor Control for a Stand–Alone Hybrid Generation System Using Fuel Cell and Photovoltaic Energy

This paper discusses a comprehensive supervisor control for a hybrid system that comprises the photovoltaic generation , hydrogen system ( Fuel cell ,Electrolyse ) and an ac load is developed in this paper. The objectives of the supervisor control are, primarily, to satisfy the load power demand and, second, allows to store the gas through the electrolyser. For these purposes, the supervisor controller determines the operation mode online of the solar generation subsystem , switching from power regulation to maximum power conversion . Decision criteria for the supervisor based on measurable system variables are presented (voltages, and currents) . Finally, the performance of the supervisor controller is extensively assessed through computer simulation using a comprehensive nonlinear model .

Minimum Propulsion Power Assessment of a VLCC to Maintain the Maneuverability in Adverse Conditions

The International Maritime Organization (IMO) Guidelines for Determining Minimum Propulsion Power to Maintain the Maneuverability in Adverse Conditions is the sole regulation imposed on the routine design and approval of all new-built ships as a part of EEDI requirements. This study reviews the development of the guidelines and summarizes the recent amendments of MEPC76(2021). The present assessment is conducted for a new VLCC design following the new guidelines aiming at investigating the influence of alternative wave added resistance evaluation methods and the propeller design features on the assessment results. It is found that the most simple empirical formula method proposed by MEPC76 is not conservative enough, as could have been expected. On the other hand, spectral analysis methods based on empirically obtained and properly validated wave added resistance responses can produce consistent results. Moreover, discussions are made from the perspective of propeller design to meet the regulatory requirements. It is pointed out that the light running margin is a key design parameter, and propellers with larger light running margins are more advantageous for satisfying the minimum propulsion power regulation, thus ensuring the navigation safety in adverse conditions. These obtained insights and know-how can support the engineers in obtaining optimal design solutions.

Voltage and Frequency Control for Hybrid Stand-Alone Power Systems For Isolated Communities

This paper proposes a control and overall coordination of a hybrid stand-alone power system. The system may comprise a wind turbine, fuel cell, electrolyzer, battery storage, diesel generator and a set of loads. The overall control planning of the hybrid system is based on a two-level structure. The top-level is the energy management and power regulation system. Depending on wind and load conditions, this system generates reference dynamic operating points to low-level individual sub-systems. The energy management and power regulation system also controls the load scheduling operation during unfavourable wind conditions with inadequate energy storage in order to avoid a system black-out. Based on the reference dynamic operating points of the individual sub-systems, the local controllers control the wind turbine, fuel cell, electrolyzer and battery storage units. The proposed control system is implemented in MATLAB Simpower software and tested for various wind and load conditions. Results are presented and elucidated.

The Principle of Construction of Capacitive Reactive Power Compensators with Three-Stage Regulation

It is proposed to reduce the number of electrical and electronic devices by 1.5 times in three-stage capacitor installations by changing the connections in the power circuit and using a special control method. The new principle of construction of reactive power compensators will allow, with minimal changes and additions to existing installations, to reduce the costs of their production and the cost of finished products. The existing installations contain three blocks of the same type of capacitors, each of which is equipped with an electrical and electronic device and resistors for their discharge. It is proposed to connect two of these three blocks in parallel without changing the design of the products, using a common electronic device for connecting and disconnecting the resulting block of capacitors with double capacity and a common electrical device in the capacitor discharge circuit of this block. A model is presented in the Matlab environment for the study of dynamic and stationary processes of three-stage reactive power regulation in a new scheme of a capacitor plant. Numerical experiments have shown that when the installation is switched on and off, as well as when switching from one stage of reactive power regulation to another, the proposed device does not create bursts of starting currents. After starting, it almost immediately enters the steady-state operation mode and when switching stages, it also immediately passes from one level of the steady-state values of such to another level of their steady-state values. The installation is switched off without switching losses and without arcing on the mechanical contacts, since thyristor switches with natural switching are switched off first, and then the de-energized mains switch.

A method for Improving the Accuracy of Reactive Power Regulation by a Capacitor Plant

The problem of low accuracy of reactive power regulation by the most common three-component condenser installations in the industry and its impact on the quality of electricity and the efficiency of its consumption and use in industrial power supply systems is considered. To increase the accuracy of reactive power regulation by at least 2.3 times without changing the circuit of the capacitor plant and the number of switching equipment, a new control algorithm is proposed and described in detail. The results of testing a method for regulating reactive power in the Matlab environment based on the proposed algorithm for controlling capacitor blocks with changed parameters are presented. Numerical experiments have shown the possibility of seven-stage regulation, versus three-stage control in known industrial installations. The capacitor unit is switched on by a mains switch and then by thyristor switches without a surge of currents in the capacitors and without an asymmetry of currents in the network. The installation is switched off in the reverse sequence, first by thyristor switches with natural switching, and then by a mains switch without arcing on its contacts.