The three-phase grid-connected inverters are widely employed in various distributed generation (DG) applications. The use of LCL filters at their outputs has proven several benefits, regarding passive component size reduction and improved high-frequency harmonics elimination. However, the resonance of the LCL filter hinders their application. Another issue with applying model predictive control (MPC) in LCL-filter-based DGs, as a high-performance controller, is the difficulty in including the various control objectives in a single cost function. The main issues include the necessity to compensate for various delays in the control loops and the selection of a proper weighting factor between objectives. Therefore, this paper proposes an efficient MPC method for grid-connected LCL-filtered DG inverters. The proposed MPC employs proper delay compensation for current/voltage loops. Furthermore, the proposed method incorporates various controlled variables in a single-objective function, eliminating the need for cascaded control loops. The proposed MPC is simulated in MATLAB/Simulink, and different test cases of active/reactive power demands are provided. The obtained results show the robust resonance-free performance of the proposed MPC method.

The availability of recently developed medium-voltage (MV) IGBT switch modules has made the diode-free alternative topology of three-level inverters a promising option, particularly for MV applications. Diode-free three-level-based solutions possess a smaller number of components and lower conduction losses in contrast to the diode-clamped NPC inverter. Nevertheless, some switches have to withstand half of the DC-link voltage, which still imposes restrictions on implementing a 3-level T-type inverter leg. This paper presents a reconfigured power circuit for a 3-level F-type inverter leg using a four-switch per phase-leg configuration. Compared to existing restrictions in T-type phase legs, the F-type phase leg reduces voltage stress, cost, and loss of the inverter. In this paper, an assessment is conducted to evaluate the performance and effectiveness of the F-type inverter. The investigation includes thermal analysis, switching loss, and efficiency analysis of the F-type inverter controlled by model predictive controllers. The results indicate that the F-type inverter acquires better loss distribution than the T-type inverter, revealing its usage in certain low-voltage and medium-voltage applications.

Recently, doubly grounded (DG) photovoltaic (PV) inverters have proven superior performance in total elimination capability of PV leakage currents. This is due to the direct connection of PV side negative terminal with grid side neutral terminal. This paper presents a boost DG-PV five-level (5L) inverter topology based on neutral point clamped (NPC) leg. The proposed DG-PV boost 5L-NPC inverter totally eliminates the existing leakage currents, achieves boost of PV voltage, is considered a single stage PV inverter structure, uses low component count, and has continuous PV current. Moreover, finite control set model predictive control (FCS-MPC) is presented for controlling multiple objectives in a single cost function for the proposed topology. The FCS-MPC also eliminates the cascaded l0ops in the conventional control methods, which facilitates the control design process. A simulation based case study is preformed of the proposed DG-PV boost 5L-NPC inverter with FCS-MPC controller. Superiority of proposed inverter and controller have been verified with various step changes in PV power, power quality of injected grid current, and capacitor voltage control.

Analysis and performance of a three-phase single-stage SEPIC differential-mode inverter (DMI) using a discontinuous modulation scheme (DMS) are presented in this paper. Since the DMS was previously suggested in many inverter topologies to reduce the voltage stress of utilized switching devices and enhance inverter efficiency, a simple design process to integrate DMS into the SEPIC DMI is proposed in this work. With this modulation strategy, the discontinuity of the duty cycle for one-third of the entire grid frequency cycle thoroughly minimizes the conduction losses and switching losses into the SEPIC converters. Also, it is noted that the voltage stress is significantly reduced in passive elements as well as switching devices. Furthermore, the compensation of the negative sequence harmonic components is maintained without adding extra sensors. The inverter operation along with mathematical analysis of the DMS and grid current control is presented. A PSIM simulator is used to evaluate the behavior of the proposed modulation strategy. Finally, a comparison with the conventional continuous modulation scheme (CMS) is performed for a better assessment.

This paper presents an improved sequential model predictive control (MPC) method for single phase photovoltaic (PV) applications. The T-type H-bridge five-level topology is selected in this paper. The proposed method achieves constant switching frequency operation of the inverter, which is advantageous over the variable switching frequency MPC methods. The proposed fixed switching frequency MPC (FSF-MPC) method eliminates the weighting factors, which represent critical element in applying classical MPC methods. Moreover, the proposed FSF-MPC method achieves low dv/dt values through using optimized switching sequences to evaluate the cost function. The simulation results of the proposed FSF-MPC method are provided and compared with variable switching frequency MPC method. The results show the fast tracking in both controllers. Whereas, fixed switching frequency and weighting factorless operation are obtained using the proposed FSF-MPC method. Additionally, lower total harmonic distortion (THD) in the output voltage is obtained using the proposed FSF-MPC method compared to classical MPC method.

In this paper, a space Vector modulation scheme (SVMS) to enhance the performance of the single-stage three-phase grid-tied SEPIC-based differential inverter is presented. Compared to the traditional modulation schemes, the proposed modulation scheme offers a significant reduction in the peaks of output voltages and input currents of the utilized SEPIC modules at the same voltage gain. Moreover, the peak voltages of the utilized capacitors in SEPIC converters are reduced. Therefore, the voltage stresses, conduction losses, and switching losses have been decreased, and the system efficiency has been increased in accordance. The proposed SVMS is implemented by employing a simple modification to the traditional continuous modulation scheme (CMS) of differential inverters, which keeps the smooth operation of the grid-current control at the inverter side and verifies low execution time. Moreover, a detailed comparison between the proposed modulation scheme and traditional CMS at different power ratings is introduced. The performance of the proposed SVMS is evaluated using the PSIM environment to validate the theoretical features added to the grid-current control and the SEPIC-based differential inverter.

Data security is the main challenge in Internet of Things (IoT) applications. Security strength and the immunity to security attacks depend mainly on the available power budget. The power-security level trade-off is the main challenge for low power IoT applications, especially, energy limited IoT applications. In this paper, multiple encryption modes that provide different power consumption and security level values are hardware implemented. In other words, some modes provide high security levels at the expense of high power consumption and other modes provide low power consumption with low security level. Dynamic Partial Reconfiguration (DPR) is utilized to adaptively configure the hardware security module based on the available power budget. For example, for a given power constraint, the DPR controller configures the security module with the security mode that meets the available power constraint. ZC702 evaluation board is utilized to implement the proposed encryption modes using DPR. A Lightweight Authenticated Cipher (ACORN) is the most suitable encryption mode for low power IoT applications as it consumes the minimum power and area among the selected candidates at the expense of low throughput. The whole DPR system is tested with a maximum dynamic power dissipation of 10.08 mW. The suggested DPR system saves about 59.9% of the utilized LUTs compared to the individual implementation of the selected encryption modes.

Context-awareness is a key requirement in many of today's networks, services and applications. Context Management systems are in this respect used to provide access to distributed, dynamic context information. The reliability of remotely accessed dynamic context information is challenged by network delay, packet drop probability, information dynamics and the access strategies taken. QoS classification and system configuration of context management traffic is in this aspect important in order to efficiently balance generated access traffic between network delay, packet loss probability, information dynamics and reliability requirements to the information from the applications. In this paper we develop a QoS Control network concept for context management systems. The concept includes a soft realtime algorithm for model based context access configuration and QoS class assignment, and allows to put probabilistic bounds on.

Context aware network services are a new and interesting way to enhance network users experience. A context aware application/service enhances network performance in relation to dynamic context information, e.g. mobility, location and device information as it senses and reacts to environment changes. The reliability of the information accessed is a key factor in achieving reliable context aware application. This paper will review the service degradation in Context Management Frameworks (CMF) and the effect of high network utilization, with particular focus on the reliability of the accessed information. The paper considers a developed framework from the ICT project, OPEN, and investigates the impact of applying Differentiated Services (DiffServ) Quality of Services (QoS). The paper finally provides insight in how the insight gained can be utilized to ensure reliable remote accessed context information.