Cost and losses associated with offshore wind farm collection networks which centralise the turbine power electronic converters

Costs and losses have been calculated for several different network topologies, which centralise the turbine power electronic converters, in order to improve access for maintenance. These are divided into star topologies, where each turbine is connected individually to its own converter on a platform housing many converters, and cluster topologies, where multiple turbines are connected through a single large converter. Both AC and DC topologies were considered, along with standard string topologies for comparison. Star and cluster topologies were both found to have higher costs and losses than the string topology. In the case of the star topology, this is due to the longer cable length and higher component count. In the case of the cluster topology, this is due to the reduced energy capture from controlling turbine speeds in clusters rather than individually. DC topologies were generally found to have a lower cost and loss than AC, but the fact that the converters are not commercially available makes this advantage less certain

Dynamic modelling of wind turbine and power system for fault ride-through analysis

This paper presents a Simulink model of a wind power system for the holistic analysis of wind turbine and power grid during grid faults, aiming to investigate wind turbine Fault Ride-Through performance. The model comprises a highly detailed dynamic model of a 2MW wind turbine and a generic electrical network model. The simulation result shows the behaviour of both wind turbine and power grid when grid faults occurs. The impact that a grid fault has on wind turbine components and grid transients is illustrated and discussed

Design of a hybrid PV/wind/diesel generator energy system for 120 residential apartments in Gusau

Gusau, a city in zamfara state, Nigeria is faced with the challenge of inadequate power supply as electricity supply from the national grid is unstable and inadequate, besides majority of those in the remote areas are isolated from the grid. The location has a potential for renewable resources, to overcome this challenge of inadequate power supply, a hybrid electric power system which employs the use of battery storage, solar and wind energy system with a diesel generator as reserve to provide adequate power to 120 residential apartments in a settlement isolated from the grid is being designed. The solar and wind energy resources in the location were assessed; the data from the two renewable energy resources available in the location was collected for the year 2015 from the Nigerian meteorological Agency, NIMET alongside the geographical coordinates and other useful parameters as input to the HOMER software simulator for analysis. The load profile of the location was carried out, the sizing of the energy mix from PV, wind, battery and generator was made using the software. The result of the simulation shows a yearly electricity production of 168,545KWh/yr, the yearly AC primary load is 67160KWh/yr. And the excess electricity is 88581Kwh/yr, this accounts for 52.6% of the total electricity generated hence, the hybrid energy system has the potential to provide the micro-grid with adequate power with high penetration of renewable energy

DC voltage control for fault management in HVDC system

This paper focuses on the transmission system options for connection of offshore wind farms and investigates the advantages and disadvantages of proposed concepts in order to draw a conclusion regarding their suitability for connection in the electricity system. Then, the most appropriate solution is implemented in Matlab/Simulink to show its benefits. For this purpose, 5 wind farms are connected to an offshore station and their power output is transferred onshore via a point – to – point DC link. Additionally a novel proposal of DC voltage control is included in the model to simulate the behaviour of the system when faults occur in the electricity grid

Enhancing PV modules efficiency and power output using multi-concept cooling technique

The efficiency and power output of a PV module decrease at the peak of sunlight due to energy loss as heat energyand this reduces the module power output. Multi-concept cooling technique, a concept that involves three types of passive cooling, namely conductive cooling, air passive cooling and water passive cooling has the potential to tackle this challenge. The experiment was set up using two solar panels of 250 watts each with both modules mounted at a height of 37 cm to create room for air-cooling, with the application of water-cooling at the surface of one of the PV modules to reduce the surface temperature to 20 ∘C. The rear of the same module attached to an aluminium, Al heat sink. The other module also mounted was without water-cooling and Al heat sink attachment. The Al heat sink comprises aluminium plate attached with aluminium fins to aid cooling, and water at a reduced temperature achieved with the introduction blocks of ice facilitated the module surface cooling. Analysis of the power output achieved, carried out with the help of the equation for PV array power output with a derating factor of 80%. The experiment recorded an increase in output power of 20.96 watts, and an increase in efficiency of not less than 3% achieved thus making the module more efficient and productive

Gain scheduled and robust H∞ control above rated wind speed for wind turbines

This paper investigates two different approaches for individual pitch control for wind turbines. The first one is a gain scheduled decentralised control design and the second one is a robust H∞ loop shaping control design. Both controllers work well in the region above rated wind speed, exhibiting a response that is mostly independent of wind speed. The investigation is conducted based on the NREL 5MW benchmark wind turbine. Turbine modeling and control is conducted in FAST and Simulink

Control of DFIG wind turbines in offshore networks during large transients

Control flexibility and fault ride-through capability of offshore wind farms and their electrical collectors array have been studied in this paper. The research is focused on the implementation of different control techniques for large offshore wind farms and also for variable wind turbines. The third harmonic injection technique is added to improve the modulation signal, which is fitted into the PWM system. Improvements in the acquisition and process of the reference signal for the inner and outer current controllers have shown significantly power peaks’ reduction during large transients. Also, fault current reduction and reduction of the recovery time have been observed. The control system also improves considerably dc voltage performance in the HVDC link. Overall, results have shown significant improvements in the active and reactive power transmission for the ac star layout in the collector

Distribution voltage control utilising the reactive power capabilities of wind generators

Voltage rise issues have become a major limiting factor to greater penetration of wind generators in weak distribution networks. A complete decentralised approach to voltage control (VC) that fully utilises the reactive power capabilities of distribution wind generators is an emerging technology and one that has not yet been investigated extensively. This study explores the potentials of modern wind turbine technology integration to address the problem. It assesses such potentials on a realistic 289-node UK generic 11 kV distribution network using time-series optimal power flow simulations under constraint conditions. This study examines the power factor control and VC modes of operation of typical generators and proposes practical techniques that enhance greater connection capacities. The study successfully reveals that, operating the wind generators within a flexible reactive power capability limits effectively mitigates the voltage rise problem and maximises generation levels

Maximising wind generation through optimised operation of on-load tap changing transformers in active distribution networks

On-load tap changing transformers are the most common control device to regulate and maintain distribution network voltage within required limits. Voltage rise issues on the other hand have become a major factor limiting greater penetration of low carbon generators, particularly in weak distribution networks. Here, the voltage rise problem is addressed through the application of optimised set-point voltage technique that aims to improve network hosting capacity to accommodate high wind penetration. It assesses the effectiveness of the technique on a realistic 289-node UK generic 11 kV distribution network using time-series optimal power flow simulations. The results reveal that when the tap changer is operated at the optimised set-point voltage, it can lead to greater energy yields. It also shows a reduction in the number of tap changing operations when the transformer is operated within the optimised deadband allowing for an improved life-span and minimum maintenance cost

Novel metrics to quantify the impacts of frequency support provision methods by wind power

This paper introduces two novel metrics to judge the capability and influence of wind power to provide virtual inertia response (i.e. frequency support). The first metric considers the generation unit (i.e. wind turbine generator (WTG)/wind farm (WF) vs. synchronous generator). This metric is applied to compare between three different methods of provision of frequency support. The second metric assess the improvement or hindering in frequency response at the point of common coupling (PCC) between a WF and a synchronous area. This metric is critical especially to WFs that are connected via High Voltage Direct Current (HVDC) or Low-frequency AC links. Both metrics are universal so that they could be applied to any support method, and any power system. The first metric is applied to assess the virtual inertia response of an offshore WF, which is considered as a power plant along with the HVDC transmission link. Results assure the positive impact of the provision of frequency support by wind power. This impact is quantified could be used to tune frequency support controllers, and optimize system planning. It is verified that no obstacles are implied by the HVDC link to integrating frequency support methods, as the WF dominates the support proces