A.B. Attya

Evaluation of system reliability using seasonal and random operation techniques

The target of any power system is to deliver stable, clean and cheap electrical power to the customer. This paper offers two independent approaches to simulate the operation of the generating units in a power network. The first methodology depends on the load variation in each season while the other one is random through a certain sequence. Using the proposed approaches a comparison between the different suggested PDF that describes the failure and repair for any component is made. The simulation is done based on Monte Carlo method through a small radial system and the IEEE 13 node test system.

Novel wind turbine reliability model-implementation to estimate wind farms capacity credit

The expanded integration of wind energy imposes technical challenges to maintain system reliability. In order to tackle these challenges, comprehensive reliability models for wind turbines and related factors are essential. Proposed algorithm classifies Wind Turbine Generator (WTG) components based on their impact on WTG output. There upon, the WTG has a composite three-state reliability model which aggregates WTG foremost components. The chronological operation conditions of each component is obtained using state duration sampling method. Precise Wind Farms (WFs) reliability assessment requires accurate Wind Speed (WS) forecasting methods which acknowledge WSs propagation through WFs terrains. Thus, WS variations are developed based on Weibull distribution. Offered algorithms are integrated to estimate the capacity factor of some WFs using Monte Carlo simulation method. The implied WS data are recorded in certain locations in Egypt which are candidates to host WFs. The utilized simulation environments are MATLAB and Simulink.

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 process.

Insights on the Provision of Frequency Support by Wind Power and the Impact on Energy Systems

This paper implements and compares between the key concepts to enable wind power short-term frequency support from electrical and mechanical loads perspectives. Pitch de-loading, kinetic energy extraction, and wind turbine (WTG) over-speeding are investigated, where each concept is integrated as a supplementary controller to the conventional controls of WTG. Different patterns of wind speed are examined, step-change and real intermittent of high resolution. The examined aggregated synchronous area has a relatively high wind penetration with frequency support. The overall dynamic inertia of the system is assessed to analyze the impact of the integrated support methods and their key parameters. The coordination between synchronous areas and wind farms, which are interconnected through a multiterminal high-voltage direct-current network (MT-HVDC) is examined. A novel definition of the virtual inertia of MT-HVDC grid is proposed. Results show that pitch de-loading secures support reserve most of the time, and kinetic energy extraction provides sustainable support for a short interval, while accelerative de-loading could reach a compromise. The three methods are adaptable with the MT-HVDC holistic frequency support controller, with a slight advantage of kinetic energy extraction over the virtual inertia of the MT-HVDC. MATLAB/Simulink is the simulation environment.

Random operation of conventional distributed generators based on generation techniques

This paper presents a comparison between three different approaches to model the random operation of generation units in power networks for reliability studies. Monte Carlo simulation method is integrated with each of the proposed approaches to calculate the average power not supplied in a given system. The obtained results from each approach are compared to their corresponding values if obtained when seasonal operation is considered.

Increasing hybrid PV/wind/diesel generator power output with increased PV module efficiency

This research work focuses on increasing the power output of a hybrid energy system by giving a boost to the energy supplied from the PV module. It embraces the cooling of the PV module using a multi-concept cooling technique. An experiment was set up to reduce the surface temperature of the PV module to 20°C in order to increase its efficiency and hence power output. The experiment was performed using two 250 watts PV modules, water spraying was carried out on one of the modules which, was also attached with an Aluminium heat sink at the rear, while the other module was mounted without any form of cooling. The modelling of the hybrid energy system was done using MATLAB Simulink. An equation for PV module power output was used with a derating factor of 95% and the result of the experiment shows that power output of 262.4 watts is achievable, and the simulation result shows an increase in the power contributed by the module.

Frequency stability analysis in low frequency AC systems for renewables power transmission

The foreseen high penetration levels of wind energy will have serious implications on frequency stability, hence developed control methods of wind turbine and alternative technologies including energy storage should enable the provision of frequency support by wind power. Active research is ongoing to investigate the possibility of collecting and transmitting offshore wind power through low frequency alternating current systems (LFAC). This paper develops a novel method to enhance frequency support capability of generators connected to a LFAC system. The leveraged frequency regulation ability of the generators at LFAC system is emphasized. The voltage is proportional to the frequency of the LFAC system, so that the transformers can be protected when frequency drops. Then the generators at LFAC system acquire sufficient time for frequency regulation. In this paper, a hydro generator at LFAC system is regarded as an energy storage plant, which is connected to the LFAC system rather than normal frequency grid.

Encoderless flux vector oriented control of brushless doubly-fed reluctance generators

An angular position and velocity observer-based sensorless flux vector-oriented control scheme for a prominent doubly-fed reluctance generator has been presented and experimentally validated. This technology allows the use of the same partially rated power converter as the traditional slipring doubly-excited induction generator, while offering competitive performance with added cost benefits of high reliability and maintenance-free operation afforded by its brushless construction. The controller viability has been demonstrated on a laboratory machine prototype for emulated variable speed and loading conditions similar to those encountered in wind turbines.