In this letter, two new improved pulsewidth modulation (PWM) techniques are proposed for single-phase cascaded H-bridge inverter. Compared with the conventional modulation methods, including phase-shifted PWM (PS-PWM), level-shifted PWM (LS-PWM), discontinuous modulation (D-PWM), only PS-PWM can ensure the output quality and maintain the power balance between each module. That is why it is widely used. However, the switch with PS-PWM always operates in a high-frequency mode, resulting in the high switching losses and low efficiency. In order to solve the problem, two improved cascaded H-bridge multilevel PWM methods are proposed in this letter. With the proposed PWM methods, the power can be evenly distributed among modules, the utilization rate of switching devices is the same, while the switching times are reduced, which improves the system efficiency. Finally, the experimental tests are carried out on a digital-control single-phase cascaded H-bridge seven-level inverter. And the experimental results verify the effectiveness of the proposed solution.

Transformerless inverters, most of which are H-bridge inverters, have been widely used and studied in grid-connected power systems in the last decades. However, the H-bridge inverter is affected by the low- and high-frequency common-mode voltage between the input and output terminals, resulting in a large common-mode leakage current. An alternative solution is to connect the ground of the input terminal to the output load or grid, that is, the dual-grounded inverter. In this case, the low- and high-frequency common-mode voltages can be mitigated or eliminated. As a matter of fact, scholars have made several research results on dual-grounded inverters. However, as of now, there is still no literature that comprehensively and systematically summarizes these research results. To fill this gap, this article classifies different types of dual-grounded inverters from the perspective of topology for the first time, and compares and summarizes their advantages and disadvantages. More than 60 works of literature have been reviewed to identify the practical implementation challenges and research opportunities in the application of dual-grounded inverters.

With the further development of the smart grid, the modern power system has evolved into a cyber-physical power system (CPPS). In order to accurately quantify the resilience of a CPPS under cyber attacks, in this article, a resilience evaluation method for the CPPS considering the whole process of cyber attacks is proposed. First, the calculation model of successful attack probability is proposed based on the Markov node transition probability matrix and depth-first search algorithm. Second, based on the idea of nonsequential Monte-Carlo simulation, a mixed sampling method is proposed to determine the fault occurrence time and repair time of each circuit breaker in the fault set. In order to describe the change process of load after a successful attack, the response model of the power system is proposed using the optimal load reduction model based on the dc power flow. Four resilience evaluation indices for attack risk resistance, system adaptability, repair rate, and comprehensive weighted index are proposed to evaluate the resilience of CPPS considering cyber attacks. Finally, a case study is carried out based on the IEEE RTS 79 system to verify the effectiveness of the proposed resilience evaluation method.

Economic dispatch (ED) problem with valve-point effects of generation units is a non-smooth and non-convex problem. This paper presents a differential evolution algorithm based on multi-population (MPDE) to solve ED problems with valve-point effects. The proposed MPDE algorithm employs the evolutional methodology of multiple populations to overcome the limitations of the traditional differential evolution algorithm. In multiple populations, each population has its mutation strategy and parameters to enhance the searching ability. Moreover, information exchange among multiple populations to increase the diversity of individuals in a single population. In addition, the algorithm also introduces the normal distribution function to dynamically adjust the scaling factor and crossover rate to accelerate convergence speed. The proposed algorithm is tested on the 13-, 40-, 80-, and 140-unit test systems. The simulation results show that the MPDE algorithm can achieve much smaller variances compared with other intelligent algorithms. The proposed algorithm has significant performance in accuracy for solving economic dispatch problems with valve-point effects.

Based on the benefits of real‐time pricing both to individual users and the society as a whole, this study introduces a real‐time charging price (RTCP) mechanism supported by an intelligent charging management module into plug‐in hybrid electric vehicles (PHEVs) charging environment. The optimal RTCP is executed by a distributed algorithm using a utility model to maximise the whole charging system welfare. The willingness‐to‐charge parameter is derived to reflect the charging preferences of PHEV users and their different responses to the RTCP. Several scenarios are established to discuss the effect of both the RTCP and willingness‐to‐charge on charging load. The simulation results show that reasonable charging will be realised based on the optimal RTCP mechanism.