Camilo Carrillo

A third order model for the doubly-fed induction machine

Abstract Induction generators are generally simulated by means of a well-known model described by Brereton et al. [1] , based on the induction motor equations derived by Stanley [2] . In this model the possibility of opening the rotor circuit in order to inject a voltage source is not taken into account, although there are other models where it is dealt with [3] . This paper presents an alternative way of obtaining the mentioned model and introduces the possibility of modeling voltage sources in the rotor circuit, which can be very useful when simulating some generating schemes, such as variable speed asynchronous wind turbines.

Influence of the shadows in photovoltaic systems with different configurations of bypass diodes

The IU characteristic curve of a photovoltaic module is affected by shadows, depending on the shaded area of the PV module, and the radiation received by the shaded areas. Another factor in the shape of the I-V curve of a PV module, is the configuration of the electrical connection between its cells and bypass diodes. Bypass diodes are installed in the modules to prevent power consumption when they are shaded or damaged; they also prevent cells from working near the avalanche zone. This paper examines the performance of a photovoltaic array. A PV array consists of modules connected between them. Particularly, the configuration with bypass diodes overlapped is analysed, showing that totally or partially shaded modules can consume some of the power generated by other modules of the PV array. This effect is also present in low power PV arrays. In these cases, the power dissipated by a diode is small; but if there are many diodes, the power dissipated by all the diodes can be comparable with the power produced by various PV modules. Additionally, this article deals with the influence of the inverter in the MPP tracking.

Synchronization of asynchronous wind turbines

In this paper, a theoretical analysis and explanation of synchronization phenomena in wind parks with asynchronous generators is presented.

Estimation of energy losses in a Wind Park

The study of energy losses in any electric installation is closely related to energy efficiency. Its calculation depends on the number and the quality of the available electrical measurements. Typically, every wind park has electrical measurements in all its wind turbines and its HV point of connection. However, it is difficult to calculate in an easy way these losses due to problems like redundancy, inaccuracy, lack of data, etc. A state estimation (SE) method will be proposed in this article, in order to calculate the power losses. By means of available measurements (power, voltage, current...) and parameters of the network (cables, transformers...), the losses taking place in each element can be obtained. SE also allows detecting errors in measurement and calculating the wind park state when certain measurement equipments are unavailable. Wind speed measurements are used to get pseudo-measurement if necessary and to filter errors. Finally, an economic study will be done taking into account the different ways of selling wind energy in the Spanish network. Consequently, the economic importance of losses will be evaluated too. The location of this project is The Sotavento Wind Park, Serra da Loba, Spain. The results shown throughout this article have been applied there with the aim of analysing its energy efficiency.

Coordinated reactive compensation in a Wind Park

In wind energy, an incentive payment related to the reactive power compensation is applied. In the past, the maximum incentive was achieved when the cos phi, that was calculated as a monthly mean, was almost unitary (cos phi = 1.00). The payment is a percentage of the average reference tariff (ART). Since the 1st of January 2007, the Spanish regulation RD 436 /2004 has modified the incentive payment. Nowadays, it is calculated each 15 minutes from the energy during this period, and its maximum value depends on the achievement of a objective power factor (cos phi) which is defined in three time frames: peak hours (cos phi < 0,95 cap.), valley hours (cos phi < 0.95 ind.) and flat hours (cos phi = 1.00). To maximize the incentive payment, in the Sotavento Experimental Wind Park (Spain) a configuration with a central controller that coordinates the actuation over all the capacitor steps in the wind park has been installed. In this article, a central controller algorithm which is based on a dynamic programming is proposed. Its main objectives are: to maximize the incentive payment, or achieve the equivalent objective PF, and to minimize the number of connection operations over the capacitor steps (especially those in substation). At the present time, the algorithm is being tested in the wind park.

Regulation of synchronous generators by means of hydrostatic transmissions

Summary form only given as follows. In many applications within the engineering world, an isolated generator is needed (e.g. in ships). Diesel units (diesel engine and synchronous generator) are the most common solution However, the diesel engine can be eliminated if the energy from another source (e.g. the prime mover in a ship) is used to move the generator. This is the care for the shaft coupled generator, where the coupling between the mover and the generator is made via a hydrostatic transmission so that the mover can have different speeds and the generator is able to keep a constant frequency. The main problem of this system is the design of a speed governor that makes possible the desired behaviour. In this paper a simulation model is presented in order to analyse the behaviour of this kind of systems and to help in the speed governor design. The model is achieved with a parameter identification process also depicted in the paper. A comparison between simulation results and measurements is made to show the model validity.