A generalized decoupling control strategy for an off-grid solar based hydrogen production system is proposed. In order to permit a continuous hydrogen production and to decouple the solar generation from the proton exchange membrane (PEM) electrolyser, a battery bank is added between this two. Thus, the overall system consists of two conversion stages, one that couples the photovoltaic (PV) array with the battery bank, and another that couples the latter one with the PEM electrolyser. Each stage consists of partial power converters (PPC) based on Dual Active Bridge (DAB) modules connected in an input parallel-output parallel (IPOP) interleaved configuration. The proposed DC-DC converter and control strategy enables the maximum extraction of solar energy, the regulation of the hydrogen production, and at the same time, ensures the equalization of the power flow between modules of each conversion stage. The performance of the proposed generalized decoupling control strategy is validated through dynamic simulation of the overall system.

The UPQC has been widely used to improve power quality. Therefore, in this new topology, it is relevant to study the limitations in order to obtain maximum benefit. This paper presents the stationary analysis of a three-phase unified power quality conditioner with the injection of active power in the DC link from a solar panel farm. The transformation from abc axes to dq axes is used to convert sinusoidally varying quantities into constant quantities. This allows finding an explicit solution of the system's state variables and inputs for a specific operating condition, which is useful for obtaining the system's operating region. Hence, establishing the voltage variations at the Point of Common Coupling (PCC) and the power factor of the load that the UPQC can compensate, in order to maintain the voltage at the load at nominal values and a specified power factor at the PCC. Another condition imposed in this work is that the topology should not absorb active power from the grid, aiming to reduce the losses of the topology. The preliminary results show that injecting active power from solar panels into the DC link enhances the ability to compensate sags and swells at the PCC.

The clustering of platelet glycoprotein receptors with cytosolic YxxL and YxxM motifs, including GPVI, CLEC-2 and PEAR1, triggers activation via phosphorylation of the conserved tyrosine residues and recruitment of the tandem SH2 (Src homology 2) domain effector proteins, Syk and PI 3-kinase. We have modelled the clustering of these receptors with monovalent, divalent and tetravalent soluble ligands and with transmembrane ligands based on the law of mass action using ordinary differential equations and agent-based modelling. The models were experimentally evaluated in platelets and transfected cell lines using monovalent and multivalent ligands, including novel nanobody-based divalent and tetravalent ligands, by fluorescence correlation spectroscopy. Ligand valency, receptor number, receptor dimerisation, receptor phosphorylation and a cytosolic tandem SH2 domain protein act in synergy to drive receptor clustering. Threshold concentrations of a CLEC-2-blocking antibody and Syk inhibitor act in synergy to block platelet aggregation. This offers a strategy for countering the effect of avidity of multivalent ligands and in limiting off-target effects.

Power conversion has gain relevance because of the capacity to transform the electric energy as needed in many applications such as electrical drives, electromobility, reactive power compensation, renewable energies, among others. In this context, the proper control of the power converter may lead to improve the efficiency and protect the entire power converter system. This paper presents a deadbeat control with the capability to enhance the fast dynamic response, typical of this technique, and therefore to be used for current and voltage control applications that require slower dynamic. The proposed technique is implemented in a three-phase power converter with satisfactory results; moreover, this technique is simple and light in computational cost. Finally, to corroborate the proposal, simulations are included with satisfactory results showing an improved dynamic and making the deadbeat control softer as some applications may require.

An interleaved DC/DC power cells-based topology is proposed in combination with a control method for photovoltaic plants. For this, two partial power and two interleaving methods are evaluated in terms of efficiency and performance. The selected topology consists of input-parallel-output-parallel interleaved DC/DC converters, which together with the control strategy, allows a high efficiency photovoltaic system, unlike conventional topologies. However, this type of topology is prone to present an unbalanced power distribution between the DC/DC power cells, mainly due to the natural differences between their components. This paper shows the application of a power balancing control strategy for interleaved partial power converters, which guarantees an equitable power distribution, therefore, it enables a correct sizing of the components. The simulation results show the correct operation of the power cells, in terms of overall high efficiency and power distribution among the power cells.

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.

This paper proposes a mixed linear control and model predictive control (MPC) scheme with extended horizon for a neutral point inverter topology (NPC) for photovoltaic applications connected to the AC network. The strategy is able to minimize the unbalance of the voltages of the capacitors in the DC link and to draw a sinusoidal current on the network with a unity displacement power factor. Unlike other MPCs, the resulting algorithm is easy to implement, the weighing factors of the cost function are not needed, and the computational cost is reduced. These advantages are added to the ability to operate the photovoltaic module at the point of maximum power (MPP).

Finite Control Set Model Predictive Control is an emerging alternative for the control of power converters. Its main advantages are its conceptual simplicity, fast control response, flexibility and direct consideration of non linearities as well as constraints. Due to computational constraints, short prediction horizons are usually desired in power converters. However, control issues may appear when applied in topologies that exhibit non-minimum phase behavior such as active front end rectifiers and boost dc-dc converters. This work proposes the use of the concept of statically equivalent outputs in order to control these systems with the shortest prediction horizon. The proposed predictive controller partially inverts the plant dynamics, determining an auxiliary output by means of nonlinear control tools. Theoretical and simulated results show the feasibility of the proposal.

This paper presents the use of a real-time simulation platform for the study of a high-power cycloconverter drive. Advantages of this strategy are reported, especially when compared to off-line simulation tools when evaluating electrical systems in presence of complex high-power static converters. Characteristics of a cycloconverter drive are presented, together with a real-time simulation model running in a multi-core platform from OPALRT. Time-domain simulation results with a time-step of 50μ s are shown. Capabilities of the model are exemplified with the analysis of two harmonic-current compensation strategies and the integration of the model with an external power converter for a power-hardware-in-the-loop application.

This paper proposes an algorithm that effectively allows a PV plant to inject a given amount of reactive power into the grid regardless of the irradiance and temperature levels. In the presence of irradiance (daylight hours), the system injects active and reactive power into the grid, and the losses of the topology are supplied from the PV. Under absence of irradiance (clouds and at night) the system keeps the reactive power level into the grid, and the losses of the converter are supplied by the grid. Moreover, the proposed algorithm is capable of injecting a constant and given amount of reactive power during the transitions among the operating modes regardless of the active power level being injected into the grid. Thus, providing an overall robust ancillary service to support the grid.

A simple and robust multi-objective predictive control method that incorporates four main control objectives applied to a single-phase three-level neutral-point-clamped (NPC) converter operating as an active power filter (APF) is proposed in this paper. The four control objectives are: to self-support the dc-bus voltage under load variations, to compensate the reactive power and the current harmonics and to balance the dc capacitor voltages by using a predefined combination of the converter redundant switching states. The key benefit of the proposed method is that these objectives are accomplished without using weighting factors in the cost function which eliminates problems such as multi-objective optimization or additional empirical procedures for determination of these factors. As a result, the method is easy to implement and selects fast the optimal voltage to improve the dynamic-state performance. The well-known effect of model parameter errors issue, which is inherent in predictive control methods, is also tested to confirm that the method is robust even when the predictive model has a 25% error between actual and the theoretically estimated grid impedance values.

An active power filter implemented with three single-phase Neutral Point Clamped (NPC) converters is presented and analyzed. The proposed active power filter is aimed to compensate current harmonics and reactive power in three-phase medium voltage power distribution systems. A predictive control algorithm provides the switching states that ensure fast current tracking capability. To take advantage of the predictive control implementation simplicity, this paper includes useful information to replicate this implementation on similar topologies of multilevel converters. The proposed scheme presents lower line to line voltage harmonic distortion as well as an independent control in each phase, compared with the conventional three-phase NPC topology. Simulated results confirm the implementation viability of the proposed active power filter topology and associated control strategy.

Modular current source converters (MCSCs) have been proposed as an alternative method for increasing the power range of medium voltage PWM AC drives. MCSCs are built by stacking parallel current source converters. Two advantages that make MCSCs attractive are: (a) extended current/voltage ratings beyond the device ratings and (b) simplicity in balancing the DC link current in each module. This can be accomplished using two optimized modulating patterns that have been proposed for such topologies: (a) multilevel selective harmonic elimination (MSHE) and (b) displaced selective harmonic elimination (DSHE). Both techniques are based on SHE patterns but there are slight differences in their digital implementation due to the way they generate the harmonic cancellation. Furthermore, when these techniques are used in the rectifier stage, it is reported that MSHE and DSHE do not eliminate all the unwanted harmonics due to practical issues such as changes in the modulating indexes to control the DC link currents. This work compares the operation of DSHE and MSHE when used in rectifiers of an MCSC in terms of execution time, robustness to poor sampling frequency, and quality of harmonic profiles on AC input currents under different operating conditions. Experimental results are presented to validate the theoretical considerations.

A predictive control algorithm specially developed for shunt active power filters aimed to compensate reactive power and current harmonics components is presented and analyzed. The proposed predictive control algorithm is implemented in a three-phase four-leg voltage-source inverter (4L-VSI). The use of a 4L-VSI allows the compensation of current harmonics, reactive power and neutral current harmonics generated by single-phase non-linear loads. A detailed mathematical model of the filter, including the effect of the power system equivalent impedance is derived and used to design the proposed predictive control algorithm. The proposed active power filter and associated control scheme performance and compensation effectiveness are demonstrated by simulation and with experimental results.

The main drawback of a Multi-Cell topology based on Current Source Converters is the oscillating power drained by the single-phase inverters from the DC link which requires a large DC reactor in order to avoid a significant variation of the DC current. In this work, a control scheme is proposed in order to compensate the oscillating power, avoiding to oversize the DC reactor at the expense of increasing the distortion of the input currents in each power cell and the instantaneous peak of the modulation index. However, the overall input currents present very low distortion and the instantaneous peak of the modulation index can be reduced by properly designing the multi-pulse transformer in terms of voltage ratio and phase shift. Both, the input currents distortion and the effect in the modulation index are mathematically characterized. Simulation result illustrates the effectiveness of the proposed control approach.

A comprehensive solution to simultaneously compensate both reactive power and currents harmonics is presented for a multilevel STATic COMpensator (STATCOM). The proposed approach includes asymmetric power cells that independently compensate reactive power at fundamental frequency and cancel out the current harmonics coming from a nonlinear load. The presented analysis demonstrates that, under certain conditions, the modules aimed for harmonic cancellation require lower power than the modules that compensate the fundamental power factor. Thus, each module can be implemented with specialized power valves in order to improve the overall system performance. Simulated preliminary results confirm the correctness of the proposed approach.

This paper presents an overview of the state of the art in reactive power compensation technologies. The principles of operation, design characteristics and application examples of Var compensators implemented with thyristors and self-commutated converters are presented. Static Var generators are used to improve voltage regulation, stability, and power factor in ac transmission and distribution systems. Examples obtained from relevant applications describing the use of reactive power compensators implemented with new static Var technologies are also described.