This study addresses the frequency control problem in multiarea power systems through the design of a decentralized periodic event-triggered scheme (DPETS). Initially, a unified discrete-time multiarea model is developed for power systems by adopting the general discretization method. Subsequently, a discrete-type DPETS is designed, relying solely on the locally available area control error to determine the time instants for transmitting the control signal to the equivalent generating unit. Furthermore, the ultimate boundedness of power systems under time-varying load demand disturbance is demonstrated by constructing novel discrete-time Lyapunov-Krasovskii functionals, leading to a rigorous bound of ultimate states. Finally, a case study involving three-area interconnected power systems is presented to validate the feasibility of the designed control strategy.

For enhancing the capacity to optimize the control performance of the generalized predictive control (GPC) method, this paper proposes an adaptive horizon mechanism design methodology based on deep reinforcement learning (DRL). To handle the systems with the presence of mismatched disturbances, a baseline and secure environment for DRL training is established by constructing an offset-free GPC design framework. Furthermore, the proposed method incorporates a multi-objective reward function design into the twin-delayed deep deterministic policy gradient (TD3) algorithm, which explicitly considers multiple comprehensive performance indexes. This enables the ability to attain the desired level of control precision and meet diverse control requirements across various operating conditions. Besides, it attains the capability to adapt to various system parameters effectively. The proposed method is validated through a numerical simulation of a three-order numerical system and an application to a DC/DC boost converter feeding constant power loads (CPLs). Simulation and experimental comparison results with other controllers demonstrate the efficacy and performance improvements.

This paper presents a modified finite control set model predictive control (FCS-MPC) that can significantly reduce computation time and maintain good quality of output voltage. The switching states of a three-phase five-level current source converter (5L-CSC) are sorted according to the corresponding output converter current level. The influences of every switching state on the converter inductor current are analyzed. Then the optimal switching state can be anchored based on the converter current level that minimizes the cost function and converter inductor current conditions. The proposed method eliminates the need for the discrete-time model establishment for the converter. It avoids the ergodic search through all switching states, easing the controller's computation burden. Besides, this algorithm achieves multiple control goals without assigning different weighting factors to various control objectives. The simulated output voltage total harmonics distortion (THD), the inductor current ripple, and the execution time of the modified model predictive control and traditional model predictive control are compared to validate the effectiveness of the proposed algorithm.

The multiple control objective, balancing of flying capacitor (FC) voltages and the output current sets the challenge to controller design for the FC converter. The finite-control-set model predictive control (MPC) has emerged as a popular control method for the FC converter. However, the original cost function design often faces the issue of selecting suitable weighting factors. To address this challenge, this paper proposes an offline and an online strategy that utilise the principle of Pareto optimality and a knee-based Pareto pruning method. The offline approach uses the non-dominated sorting genetic algorithm (NSGA-II) to explore the optimal weighting factors. In contrast, the online strategy employs the knee-based decision-making method that avoids weighting factors. Simulation results are provided to validate the feasibility of both approaches.

The concept of smart grid has been introduced as a new vision of the conventional power grid to figure out an efficient way of integrating green and renewable energy technologies. In this way, Internet-connected smart grid, also called energy Internet, is also emerging as an innovative approach to ensure the energy from anywhere at any time. The ultimate goal of these developments is to build a sustainable society. However, integrating and coordinating a large number of growing connections can be a challenging issue for the traditional centralized grid system. Consequently, the smart grid is undergoing a transformation to the decentralized topology from its centralized form. On the other hand, blockchain has some excellent features which make it a promising application for the smart grid paradigm. In this article, we aim to provide a comprehensive survey on the application of blockchain in smart grid. As such, we identify the significant security challenges of smart grid scenarios that can be addressed by blockchain. Then, we present a number of blockchain-based recent research works presented in different literature addressing security issues in the area of smart grid. We also summarize several related practical projects, trials, and products that have emerged recently. Finally, we discuss essential research challenges and future directions of applying blockchain to smart grid security issues.

A new dual-output multilevel converter topology based on neutral point connection is introduced. The topology significantly reduces the switch count, especially with increasing output voltage levels. Hence, it is referred to as the Reduced Switch Count Dual-output T-type (RSC-DT) multilevel converter. A level detection PD-PWM modulation technique was implemented to drive the converter's output and maintain the dc-link capacitor voltage balancing. The neutral point voltage balancing was achieved by utilizing the redundant states occurring under three-phase operation. The simulation results shows an effective control algorithm and normal operation of the converter. A study on the dc-link capacitor balancing limitation has also been carried out.

This paper presents an improved phase-disposition pulse width modulation for the Cascaded Dual-Output Multilevel (CDOM) converter. Additionally, the traditional CDOM converter is modified to be operated with reduced switching components without effecting the system operation. A phase-disposition pulse width modulation is modified for optimal state to operate the converter under minimized average power device switching frequency. A cost function based on hamming distance of the switching states is utilized to control the proposed converter. The performance of the converter is demonstrated and evaluated for common and different frequency outputs using MATLAB simulations. The converter is operational under a wide variety of operation points and the modulation scheme is shown to be effective in significantly reducing the average device switching frequency.

In this paper, a finite control set model predictive control (FCS-MPC) is developed and applied to the hybrid Nine-level Active Nested Neutral-Point Piloted (9L-ANNPP) voltage source converter. A mathematical model for the converter is derived and then incorporated in the FCS-MPC. The objective of the control algorithm is to operate the converter at the desired reference output current while balancing the dc-link and flying capacitors' voltages. The balancing of the capacitors is achieved by utilizing the redundant switching states of the converter. The control algorithm is also applied to a similar hybrid 9-level converter to compare the output quality of both topologies. The effectiveness of the implemented FCS-MPC is evaluated by computer simulation under different operating conditions. The control algorithm is able to produce high quality output while maintaining the capacitors at the target voltage levels. The comparison of the two topologies shows that the 9L-ANNPP can produce similar output waveform quality despite of its reduced component count.

This paper presents a fixed frequency model predictive control (FFMPC) of a three-level bi-directional flying capacitor DC-DC converter for energy management application in a DC microgrid. The presence of three voltage levels give the converter advantage of having reduced voltage stress on the power switches and low ripple in its inductor current. Additionally, the capability of having bi-directional power flow enables the converter to integrate energy storage devices such as the battery to a DC microgrid effectively. An FFMPC algorithm is formulated using the developed mathematical model in order to yield the dual objective of bi-directional power flow and flying capacitor voltage balancing. In this paper the performance of the FFMPC algorithm is compared with the conventional finite control set model predictive control (FCS-MPC) algorithm in terms of dynamic response and inductor current ripple. A significant reduction in current ripple was observed using the proposed algorithm. Furthermore, a DC microgrid comprising photo-voltaic (PV) system, load, and battery are considered to assess the effectiveness of the designed FFMPC algorithm under varying load and PV power injections.

This paper presents a finite control set model predictive control (FCS-MPC) of a three-level bi-directional flying capacitor DC-DC converter for energy management application in a DC microgrid. The presence of three voltage levels give the converter advantage of having reduced voltage stress on the power switches and low ripple in its inductor current. Additionally, the capability of having bi-directional power flow enables the converter to integrate energy storage devices such as the battery to a DC microgrid effectively. An FCS-MPC algorithm is formulated using the developed mathematical model in order to yield the dual objective of bi-directional power flow and flying capacitor voltage balancing. Furthermore, a DC microgrid comprising photo-voltaic (PV) system, load, and battery are considered to assess the effectiveness of the designed FCS- MPC algorithm under varying load and PV power injections.

This paper proposes an open-loop approach for selective harmonic detection from the single-phase power system under changeable frequency environment. It consists of a frequency tracking algorithm relying on a fixed tuned demodulation method and a selective harmonic detection scheme based on an adaptively tuned cascaded delayed signal cancellation (CDSC) strategy. It can be easily arranged to detect one or several harmonic(s) from the input signal contaminated by different harmonics. The open-loop configuration makes the proposed technique robust, free of interdependent loop, easy tuning, and unconditionally stable. The real-time utilization of trigonometric and inverse trigonometric functions is also avoided in the technique. When compared with the discrete Fourier transform and CDSC-based technique reported in the technical literature, it demands less computational effort and can create faster dynamics and better steady-state accuracy in the estimated frequency. The usefulness of the technique is confirmed by simulation and real-time experimental results.

This paper presents the design and implementation of a grid-connected permanent magnet synchronous generator wind power system with low-voltage ride-through. A control system regulates the constant dc-link voltage and provides the maximum power transfer to the grid by controlling unity power factor. The active power is regulated to reduce the current excess, and the reactive power is injected into the grid to avoid the inverter damage under grid faults. A dc-link voltage controller maintains a constant dc voltage during faults. The proposed control system is experimentally validated for the normal and faulty conditions on a grid-connected wind power system. Experimental results demonstrate the effectiveness and robustness of the proposed system regarding voltage and power control.

In this paper, a DC-bus microgrid, based on solar array and battery storage, is simulated and the control system is developed to operate the microgrid in grid-tied and islanded modes. Microgrid modules, including the electric elements, the converters and the local control units, have been developed with the focus on the control schematics. The control system provides the signals to the converters for DC-bus voltage regulation and current control, for power transfer, depending on the operation mode. The control configuration is flexible to allow operating the microgrid under different modes. This structure provides a mechanism to carry out any condition that can be developed by the power management system. The microgrid has been simulated using MATLAB/Simulink platform and different scenarios have been tested to verify the control system and the microgrid response.

This paper presents a voltage balancing method for stacked multicell converters based on phase disposition pulse-width modulation. This method is based on minimizing a cost function to determine the optimum redundant state for capacitor voltage balance for each particular voltage level. The robustness of the proposed voltage balancing method is verified against static and dynamic unbalanced load conditions. Furthermore, a significant reduction in the switching frequencies of the power devices is achieved by using sawtooth carriers instead of standard triangular carriers without affecting the voltage balancing capability.

This paper proposes a voltage balancing method for a seven-level stacked multicell converter (SMC) based on phase disposition pulse-width modulation (PD-PWM) using reduced switching transitions. This method is called optimal-transition voltage balancing method. The selection of the optimal transition sequence is performed by minimizing a cost function and the transitions that would result in more switchings of the converter semiconductor devices are avoided. The simulation results show a significant reduction of the average switching frequency as compared to the use of the optimal-state voltage balancing method, while maintaining the balance of the FC voltages. Moreover, the proposed PD-PWM voltage balancing method is robust to unbalanced linear loads, non-linear loads and transients.

This paper proposes an active voltage balancing method for stacked multicell converters (SMC) using phase-shifted pulse-width modulation, which is easy to implement and extend to high number of levels. The proposed method balances the voltages of the capacitors by modifying the duty cycle of each switch of the SMC using a proportional controller. The crossed effect between capacitor currents and duty cycles is considered and is used for optimal capacitor voltage balance. The performance of the proposed voltage balancing method is verified by simulation for different operating conditions, such as unbalanced linear loads, non-linear loads and load transients.

The flying capacitor (FC) multilevel converter requires a capacitor voltage balancing mechanism for proper operation. This paper proposes a voltage balancing scheme for a five-level FC converter based on phase disposition pulse-width modulation (PD-PWM) using transitions that produce the minimum number of switching events. This strategy will be called optimal-transition voltage balancing (OTVB) scheme. Since multiple optimum switching transitions between two consecutive voltage levels may be available, such a redundancy is used to regulate the FC voltages at their desired levels. Those transitions that produce more switching events are avoided. The rest of transitions are evaluated by means of a cost function and the one that produces the minimum value is selected. Simulation results show a significant reduction of the average switching frequency as compared to the use of the optimal-state voltage balancing (OSVB) scheme, while maintaining the balance of the FC voltages. Moreover, the proposed PD-PWM voltage balancing strategy is robust to static and dynamic load conditions.

The flying capacitor (FC) multilevel converter has attracted a great deal of interest in the recent years because of its easier extension to a higher number of levels (n>;3), as compared to its counterpart, the diode-clamped converter (DCC). The main focus of this paper is to develop a voltage balancing scheme of FCs for a five-level FC converter based on phase disposition pulse-width modulation (PD-PWM). Since there are multiple states that produce the same output voltage at the leg of the converter, such a redundancy is used to regulate the FC voltages at their desired levels. The selection of the optimal states is performed by minimizing a cost function. A drawback observed when using standard symmetrical triangular carriers for the PD-PWM, is the additional switching events that are produced due to transitions within the same voltage level. Nevertheless, this fact can be avoided by using sawtooth carrier waveforms instead. Simulation results verify the robustness of the proposed voltage balancing scheme against static and dynamic load conditions. Moreover, using sawtooth carriers a significant reduction of the switching frequency is achieved as compared to the use of standard triangle carriers while maintaining the FC voltage balanced.