This paper proposes a hybrid control scheme based upon both a linear and a predictive control approach for a grid-tie inverter for photovoltaic applications. The proposed strategy uses the complex representation of the switching states and splits them choosing the best one without using an iterative loop. The resulting algorithm, in terms of the dynamic and static response, performs like the traditional Finite Set Model Predictive Control (FS-MPC). However, the proposed scheme is easy to implement, it does not need to tune parameters nor need a cost function and nor require iterating all the possible states to choose the best. Over the abovementioned advantages, it has the capability to operate the photovoltaic module at the maximum power point (MPP) and the ability to impose a sinusoidal current at the grid side with a unitary displacement power factor. Preliminary results are presented to validate the proposed control method.

Future distribution grids will require to integrate renewable energies in higher penetration levels than we are used to today in conventional power systems. To make this possible, key aspects of their operation such as reliability and robustness must been in safe levels. To accomplish the latter, two different technologies have been proposed: (a) Virtual Synchronous Machines and (b) Smart Transformers. Despite all the benefits that each one of these technologies provide, solid-state transformers have not been very successful in operating as smart transformers. Then, hybrid transformers were proposed as a more feasible solution and with the capability of providing ancillary services to the distribution grid. In this paper, a new type of hybrid transformer that incorporate features of a virtual synchronous machine is proposed. The proposed transformer is capable of emulating virtual inertia as an ancillary service, and, at the same time, providing other basic services such as reactive power injection and voltage compensation. Simulation results provide evidence of the advantages of using this type of hybrid transformers in distribution grids.

In this paper, a virtual synchronous generation (VSG) strategy is proposed for a three-phase quasi-impedance source inverter (qZSI). The main objective of the scheme is to provide inertia and damping to the inverter operation in order to add those characteristics to the system in the form of ancillary services, thus contributing a more stable operation of the microgrid where the inverter is operating. The generated references are received by linear control loops on the dc and ac sides of the three-phase qZSI. In the development of this work, the theoretical foundations of the proposal are shown. Also, to prove that the strategy helps to improve the response of the system, simulated results of the qZSI connected to a weak grid are displayed, showing data of the inverter operating in a traditional form (without inertia) and as a VSG, to make comparisons.

This paper proposes an algorithm capable of estimate the global maximum power point of a large photovoltaic (PV) array system operating under partially shaded conditions. The power-voltage characteristic of a photovoltaic array is a nonlinear function that becomes more complex under partial shading conditions, in fact, the power-voltage curve may exhibit multiple local maximum power points. The proposed algorithm uses two PV reference cells, every 900 m2, one operating in open-circuit and the other one in short-circuit, to estimate the solar radiation and the ambient temperature conditions of the PV arrays. The results show an estimation error of the ambient conditions lower than 1% of the actual values. As a result, the arrays provide the maximum power possible for any distribution of irradiance and temperature conditions.

This paper proposes a control strategy for a single-stage, three-phase photovoltaic (PV) system connected to a distribution network. The control entails obtaining the maximum power point of the PV system by means of a control strategy that is based on an inner current-control loop and an outer DC-link voltage regulator. The current-control mechanism decouples the PV system dynamic from those of the network and searches for unitary power factor at the grid side. The DC-link voltage-control scheme achieves maximum active power output. The maximization of the output power is performed by operating the PV array at its maximum power point that is estimated by a proposed technique that uses two PV measuring cells, one operating in open-circuit and the other one in short-circuit.

Power quality and reliability are inherent characteristics of the cascaded multilevel converters. However, in some converters, efforts should be made to ensure the durability and reliability of the equipment. This is the case of the single-phase current source cascaded inverter (SPCS-CI) in which, due to possible differences in the DC input current to each inverter of the system, it will be necessary to limit each output voltage of each unit. This can be done through a linear control strategy. In this work, the model and the mathematics of the problems caused by unbalanced DC currents in the described cascaded system are presented. Furthermore, a control scheme based on d-q reference frame components is proposed. Along with this, a control for the DC component voltages in the individual outputs of each inverter is added, which cannot be compensated completely by the d-q scheme. The proposed control strategy is a linear scheme with an updatable decoupler that allows to control d-q and DC voltages in a set of single-phase current source inverters disposed in a cascaded arrangement. Simulated results show the effectiveness of the proposed scheme.

This work presents a case study of a modular photovoltaic (PV) plant where PV panel arrays are connected to the grid through cascaded single-phase current-source inverters. It is shown that, under non-uniform insolation conditions of the PV arrays, the output voltages of the cascaded inverters become unbalanced. Therefore, a dc voltage elimination control loop is proposed to balance the output voltage of the H bridges. Additionally a control technique called virtual synchronous generator (VSG) is applied to the PV plant in order to support the control of the grid frequency emulating an inertial response and providing damping and droop power. For the simulated cases the PV plant was always capable of performing the VSG functions, in spite of the unbalance condition of the output voltages of the H bridges. However, when the proposed dc voltage elimination control loop was in operation the maximum peak output voltage and the amplitude of its fundamental component were reduced in 13.3 % and 27 % respectively.

The paper describes a technique to match satellite and radar images using the Hausdorff distance (HD). Minimization of the average of a truncated array of sorted Hausdorff distances is used to get estimates for the radar location, together with sensor bias errors and its platform speed vector. The technique is applied to maritime navigation, where geo-referenced satellite images (UTM) are matched to radar scan images. Good estimates are obtained for these variables, thus providing an alternative method to obtain a vehicle's location in GPS-denied environments or for indoor autonomous navigation.

This paper presents a control method called the pseudo-passive energy dissipation (P-PED) method. The P-PED method is a closed-loop control scheme for increasing the overall damping characteristics of an elastically-mounted space manipulator system. It reduces degrading base vibrations resulting from external disturbances or motion of the manipulator, thereby decreasing the time necessary to perform maneuvers. A methodology for computing the optimal P-PED gains is presented. Experimental results are presented which show that the P-PED method is viable for practical implementation.

The Coupling Map has been proposed as an analytical tool to describe the dynamic interaction between space manipulators which are either elastically mounted or carried by free-flying spacecraft. The Coupling Map has yielded a number of path-planning algorithms which have been successfully demonstrated in simulation to improve system performance. This paper presents an experimental evaluation of the Coupling Map and some of its path-planning algorithms. These experimental results show that the Coupling Map based path-planning algorithms are valid and viable candidates for practical implementation on space manipulator systems.>