In the future solar energy will be very important energy source. More than 45% of necessary energy in the world will be generated by photovoltaic array. Therefore it is necessary to concentrate our forces in order to reduce the application costs and to increment their performances. In order to reach this last aspect, it is important to note that the output characteristic of a photovoltaic array is nonlinear and changes with solar irradiation and the cellpsilas temperature. Therefore a maximum power point tracking (MPPT) technique is needed to draw peak power from the solar array in order to maximize the produced energy. This paper presents a comparative study of ten widely-adopted MPPT algorithms; their performance is evaluated using the simulation tool Simulinkreg. In particular, this study compares the behaviors of each technique in presence of solar irradiation variations.

Currently, the quality of supplied power is important to several customers. Power quality (PQ) is a service and many customers are ready to pay for it. In the future, distribution system operators could decide, or could be obliged by authorities, to supply their customers with different PQ levels and at different prices. A new device that can fulfill this role is the OPEN unified power-quality conditioner (UPQC), composed of a power-electronic series steady-state performancemain unit installed in the medium-voltage/low-voltage (LV) substation, along with several power-electronic shunt units connected close to the end users. The series and parallel units do not have a common dc link, so their control strategies are different than traditional UPQC control techniques. This device can achieve general improvement in PQ, reducing the most common disturbances for all customers that are supplied by the mains (PQ) by using only the series unit. Additional increments in PQ (i.e., mains power interruptions), can be provided to the customers who need it (custom power) by the shunt units. Therefore, this new solution combines an improvement in PQ for all end users, with a cost reduction for those that need high quality power. The proposed solution has been analyzed and described, and a model of a 400-kVA LV grid is considered a test network to evaluate the steady-state performance and functioning limits. The results obtained under steady-state conditions justify the configuration chosen and good device performance.

During overloads in the mains, the load curtailment applied to interruptible loads is often the only solution to keep the network in operation. Normally, in contingencies, the difference between the power absorbed and the power produced is very low, often less than 1% of the latter. Therefore if all the loads participated in the load shedding program, the discomfort would be minimal, considering its usually short duration. According to this point of view, we present a new approach to the load shedding program to guarantee the correct electrical system operation by increasing the number of participants. This new load control strategy is named Distributed Interruptible Load Shedding (DILS). Indeed, it is possible to split every user's load into interruptible and uninterruptible parts, and to operate on the interruptible part only. The optimal load reduction request is found by minimizing the expected value of an appropriate cost function, thus taking the uncertainty about the power absorbed by each customer into account. Presently, several users such as hospitals, data centres, supermarkets, universities, industries, etc. might be very interested in typical shedding programs as a way to spare money in their electrical account. However, in the future, when the domotic power plants are likely to be used widely, the distributors could interest the end users in participating in DILS programs for either economic or social reasons. By adopting the DILS program, the distributors can resort to the interruptible loads not only in case of emergency conditions but also during normal and alert operations.

Power Quality (PQ) improvement in distribution level is an increasing concern in modern electrical power systems. One of the main problems in LV networks is related to load voltage stabilization close to the nominal value. Usually this problem is solved by Smart Distribution Transformers, Hybrid Transformers and Solid-state Transformers, but also Dynamic Voltage Conditioner (DVC) can be an innovative and a cost effective solution. The paper introduces a new control method of a single-phase DVC system able to compensate these long duration voltage drifts. For these events, it is mandatory to avoid active power exchanges so, the controller is designed to work with non-active power only. Operation limits for quadrature voltage injection control is formulated and reference voltage update procedure is proposed to guarantee its continuous operating. DVC performance for main voltage and load variation is examined. Proposed solution is validated with simulation study and experimental laboratory tests. Some simulation and experimental results are illustrated to show the prototype device's performance.

The paper introduces a simplified model, named "two branches modelldquo, to characterize the electrical behaviour of the DLCs (Double Layer Capacitors). The new model is very similar to many others in literature from the circuital point of view, however the process of identification of its parameters is easier and faster. This new identification process can be followed in other some model proposed in literature. Experimental charge tests have been executed on supercapacitors of two different labels (Epcos and Maxwell) and size (between 100 F to 600 F). The experimental results and the performed simulations have been reported in order to verify the validity of the new identification proposed method.