In this article, a novel switched-capacitor basic cell is introduced as the building block of a multilevel power-electronic inverter. Two distinct modulation strategies are proposed that control how the capacitors are charged. The two modulation strategies enable different utilization of capacitor voltages, number of voltage levels, and dc-to-ac voltage gains. The operations of the two-cell and three-cell topologies, yielding 4 and 5 ac voltage levels, and 7 and 8 ac voltage levels, respectively, are analyzed. The concept and analysis are experimentally validated through a 1-kW prototype, exhibiting superior maximum voltage gains, competitive levels of efficiency across a large power throughput range, high peak efficiencies, and low total harmonic distortions (THD) for the ac-side variables. The featured prototype exhibits peak efficiencies of about 97%, across-the-board efficiencies in excess of 94% for the majority of the power throughput range, and voltage THDs of the unfiltered ac voltage better than about 13%. This article aims to present an original basic cell, the modular development of topologies using this cell, two modulation options for these topologies that modify their gain characteristics and the number of output voltage levels, thus demonstrating a versatility not normally found in conventional topologies. This work is not intended to cover all the issues related to these topologies, such as closed-loop control, experimental optimization, capacitor voltage balancing when in closed loop; these issues will be discussed in future work. As shown in the article, the proposed inverter topology demonstrates superior software and hardware configurability and modularity, as compared with a number of well-known multilevel inverter topologies.

In order to ensure the reliability of through power supply lines for railways in areas with power shortages, this paper proposes a railway through power supply technology based on a series-parallel hybrid active voltage quality regulator. This technology enables ideal railway through power supply through direct power draw from the overhead contact system (OCS) and conversion along with series compensation. Building on an analysis on the topology of a series-parallel hybrid active voltage quality regulator, the design allocates parameters for its key components. The design also incorporates a repetitive control algorithm for the parallel converter and a dual closed-loop control strategy—encompassing both voltage and current—for the series converter, to accommodate the different control objectives of the series and parallel sections. The feasibility of the proposed series-parallel hybrid railway through power supply technology was verified through applications in typical engineering scenarios. The engineering application results show that the output voltage deviation of the railway through power supply does not exceed 6.7%, the three-phase voltage imbalance does not exceed 3.4%, and the harmonic voltage distortion rate does not exceed 3.9%. All power quality indicators of the railway through power supply utilizing the proposed technology meet the allowable limits specified in Chinese national standards.

In this article, a fast and parameter-intensive loss minimization algorithm (LMA) is proposed for the surface-mounted permanent magnet synchronous machine (PMSM). The algorithm utilizes ripple correlation control to steer the operating point toward the optimal solution by evaluating the correlation between the injected ripple on the control variable and its effect on the input power. Unlike model-based LMAs, this method does not rely on the motor loss model, its parameters, or precomputed information. Instead, it employs a high-speed search-based procedure to minimize the input power directly. The theoretical analysis includes a design procedure and a method for determining the upper bound of the injected ripple frequency based on the principles underlying loss minimization of PMSMs. Since the d-axis current does not contribute to torque production in surface-mounted PMSMs, the artificial perturbation introduced by the algorithm does not result in undesirable torque ripple. The analysis is supported by simulations and experimental tests. The results demonstrate that the proposed algorithm enables the system to converge to the optimum point within around 1.5 s, making it suitable for high-dynamic applications.

Abstract The main engine of construction machinery often involves the compound action of multi-action, such as excavator bucket rod, shovel bucket, and moving arm. Due to the matching relationship between the constant pressure differential valve and main valve, constant power limitation of a pump, load change, and other factors, it will cause the load with low pressure to move first and the load with high pressure to move later. To solve this problem, the existing speed control (or flow control) in the industry generally adopts pre-valve or post-valve compensation load-sensitive systems, positive flow control, negative flow control, constant power control, and so on. The speed control method can solve the coarse flow distribution under multi-load conditions, but is not suitable for working conditions with high precision of flow control or flow distribution, such as speed tracking, trajectory control, etc., and cannot meet the accurate control of flow or speed. In this paper, a speed decoupling control method based on hydraulic factors (such as pressure drop, flow rate, oil temperature, hydraulic pump speed, system pressure, etc.) is proposed. Through accurate modeling and simulation technology, the accuracy of compound action flow control is improved, and the anti-interference energy of the compound action system is enhanced, which lays a foundation for hydraulic speed tracking, displacement tracking, and so on.

A fast and parameter-intensive maximum power point tracking (MPPT) technique is presented for a photovoltaic (PV) water pumping system, driven by the brushless dc motor (BLDCM). The technique is based on the application of “ripple correlation control”. As an advantage, rather than artificial signal injection, the proposed technique employs the inherent perturbations introduced due to phase commutation and nonsinusoidal back-EMF of BLDCM to determine the maximum power points of the PV system. The technique can be simply employed for different configurations of BLDCM-based PV water pumping systems. Experiments are performed to demonstrate the effectiveness of the proposed technique.

Parental care is essential for biological systems. Marital bliss is one of the ideal paradigms for parental care, in which males contribute in raising offspring and females require a courtship time. Yet marital bliss state is neither Nash equilibrium nor Pareto optimum for the classic Battle of the Sexes. It thus leads to a gap between evolutionary theory and marital bliss. Previous works concentrate on the pairwise interactions between the two sexes to fill this gap, such as the courtship time and encounter rate. The social relationships within the same sex, however, receives much less attention. Here we investigate how social relationships within the same sex change marital bliss by introducing the coevolution of strategy and social network. Based on the time scale separation, it is found that a symmetric game is emergent via social adjustments within each sex, and the evolutionary outcome is determined by the interplay between the emergent symmetric game and the Battle of the Sexes. We find that marital bliss can be promoted when males are rational (strong selection limit) and females are irrational (weak selection limit); the stable Coy-Coy social relationships both stabilize and speed up marital bliss; the general criterion of stabilizing marital bliss for arbitrary imitation function are found, which are verified by simulations. Furthermore, the emergent symmetric games are insightful for determining whether the stable marital bliss is global stable. Our work provides an alternative avenue to facilitate marital bliss, which can be applied for general asymmetric games on dynamical networks.

This article provides a detailed analysis of the power electronics solutions enabling bipolar dc grids. The bipolar dc grid concept has proven to be more efficient, flexible, and higher in quality than the conventional unipolar one. However, despite its many features, these systems still have to overcome their issues with asymmetrical loading to avoid voltage imbalances, besides meeting regulatory and safety requirements that are still under development. Advances in power electronics and the large-scale deployment of dc consumer appliances have put this growing architecture in the spotlight, as it has drawn the attention of different research groups recently. The following provides an insightful discussion regarding the topologies that enable these architectures and their regulatory requirements, besides their features and level of development. In addition, some future trends and challenges in the further development of this technology are discussed to motivate future contributions that address open problems and explore new possibilities.

永磁同步电机在零低速下的无传感器控制主要是基于电机凸极效应.传统高频信号注入法利用饱和凸极效应估计出转子位置,在电流环与信号处理环节使用滤波器,造成电流环响应与位置估计延迟.针对上述问题,对改进的高频方波信号注入的无传感器控制方法进行研究.采用方波信号代替传统正弦波信号,将方波信号频率提高至逆变器开关频率,避免滤波器的使用,提高了系统的带宽.在速度控制器方面,采用改进的线性自抗扰控制器代替PI控制器,将传统的PI、NLADRC、改进后的LADRC控制效果进行对比,仿真结果验证了改进后的系统具有更好的控制性能.

Model predictive control is an effective approach to achieve high performance on electric motor drives. In this study, a two-vector based low-complexity model predictive flux control (TVLC-MPFC) is proposed and introduced for low power current-source inverter (CSI)-fed induction motor (IM) drive. In contrast to conventional two-vector based model predictive flux control (TV-MPFC), TVLC-MPFC is a more simplified scheme with a lower calculation burden, which eliminates the requirement on the iteration procedures to obtain the results of the optimal current vector combination with optimal dwell time. Moreover, since TVLC-MPFC avoids the possibility of selecting the wrong vector combination in some cases, which would happen with conventional TV-MPFC, it presents better output performance than TV-MPFC. The robustness of TVLC-MPFC under parameter uncertainty is discussed as well. Experimental tests are carried out on a low power CSI-fed IM drive (5 kW/208 V/14.3 A) and verify the effectiveness of the proposed scheme.

Recently, a star-channel modular multilevel converter (MMC) was proposed for zero/low-fundamental-frequency operation. However, it is companied by two potential issues in practices: the star-channel branch suffers from submodule capacitor voltage deviations and the entire-speed-range operation for motor drive is not confirmed. This paper investigates the control degrees of freedom, and proposes control algorithms for star-channel branch and main arms. These control algorithms cascaded with advanced motor controls form the overall control scheme for drive system. Simulation and experimental results show that the star-channel MMC along with the proposed algorithms successfully maintain the SM capacitor voltages, and achieves the variable speed operation from standstill to rated speed.

为了准确分析分布式光伏接入导致的配电网不平衡,针对配电网三相不平衡,给出了一种基于分布式光伏接入配电网的优化配置.选择三个目标函数(光伏容量比、系统网络损耗、电压稳定裕度),并且建立考虑三相不平衡的分布式光伏多目标优化配置模型.为了解决粒子之间互不占优的问题,使用最小角度的多目标粒子群算法求解,通过算例验证模型和方法的有效性.结果表明,配电系统三相不平衡得到了有效改善.所做研究工作为我国分布式电源接入配电网的发展提供了参考和借鉴.

This paper presents a novel load frequency control (LFC) model for a stand-alone hybrid micro-grid in the presence of renewable energy resources. A perilous fact in operation of isolated micro-grid is to deal with a low-inertia system owing to the unpredictable structure and the intermittent fluctuation of RESs. In comparison to the conventional power system, the rate of change of frequency (RoCoF) is high in isolated micro-gird. Therefore, the need for fast frequency response provision delivered by existing distributed energy resources, which are inverter-connected technologies, arises. Some distributed energy resources (DERs) can be considered as potential reserves for active power injection in the load frequency control scheme. The simulation results depict that renewable energy resources like diesel engine generator (DEG), Fuel Cell (FC), Flywheel Energy Storage System (FESS) and Wind Turbine Generator (WTG) have the capability to improve frequency excursion during various operating conditions if comprehensive small-signal dynamic models for RESs are introduced in isolated micro-grid and proper contribution of them in load frequency control studies is considered.

This manuscript details a design method for a 500kW solar power based microgrid system for space applications. The design method utilizes multi-objective optimization with the Genetic Algorithm considering four parameters that characterize solar power based microgrids (battery voltage, PV maximum power, PV maximum power point voltage, and number of panels per string). The final optimization metric is the ratio of daily average deliverable power to total system mass (W/kg) metric. The microgrid system is composed of a number of modular DC-DC micro-converters, of which four topologies (buck, boost, buck-boost and non-inverting buck-boost) are evaluated and compared. The non-inverting buck-boost converter is determined to be the best candidate, and the optimal system characteristics are provided and analyzed. The final system design achieves a specific power of 35.56W/kg, with optimized result of 743.7V battery voltage, 439.5W PV maximum power, 182.7V PV maximum voltage, and three panels per string. Based on the optimizations results, a prototype is designed, tested, and analyzed in terms of efficiency and low temperature reliability. The converter achieved a peak efficiency of 98.4%, a power density of 3.54W/cm3, a specific power of 3.76W/g, and operated for over 267 hours of Ll-minute low temperature cycles from 0°C to -140°C.

The Z-source network idea has opened up a new research area in the power electronics field. In this paper, a new switched-inductor network, called extended switched-inductor quasi-Z-source inverter (ESL-qZSI), is proposed. From a topological point of view, the new inverter has an additional inductor and three diodes compared with the switched-inductor quasi-Z-source inverter (SL-qZSI). The suggested inverter has a DC source ground point, continuous input current, and no start-up inrush current. This proposed inverter compared with SL-qZSI in the two investigated scenarios. Scenario 1: the proposed inverter has lesser capacitor voltage stress at the voltage conversion ratio than the voltage stress of SL-qZSI, which results in lower DC-link voltage. Scenario 2: the proposed inverter has higher voltage gain with respect to the SL-qZSI, at the same input source and modulation index. Simulations are carried out using MATLAB/Simulink and compared with experimental ones, to show the validity and effectiveness of the proposed inverter. In order to estimate the losses and efficiency, calculations of power losses and efficiency of the ESL-qZSI and SL-ZSI are presented. Simulation and experimental results verify the effectiveness of the proposed inverter.

为了定性定量分析电动汽车大规模、高密度接入引起的电网谐波问题,提出了一种电动汽车快充充电站谐波分析模型.在综合考虑充电模式、电池特性、用户驾驶行为习惯的基础上,建立了快充充电站功率时序概率密度函数;然后,结合考虑充电机拓扑结构的谐波解析表达式,建立了计及时序特性的电动汽车充电站快充谐波分析模型;最后,以湖北某地区电动汽车充电站相关数据为依据,研究了电动汽车充电站各次谐波及总谐波畸变的时序变化规律.结果 表明,电动汽车充电机拓扑结构及数量对充电站谐波特性影响显著,谐波总畸变率(total harmonic distortion rate,THD)呈现明显的时序特性.在规划接入阶段应有意识的选取合适的时段分析,并合理搭配电动汽车充电站内的充电机种类以降低谐波影响.

Cascaded H-bridge (CHB) is a promising topology for medium-voltage high-power applications. CHB consists of low-power H-bridge modules in each phase, and these modules are connected in a cascade manner to achieve multilevel operation. However, CHB requires a phase-shifting transformer with multiple secondary windings to generate an isolated dc source for each module, and this requirement increases the overall system cost. In this paper, a series connection of low-power modules is employed to realize a new power converter called a series-connected multilevel converter. Each phase of the proposed topology requires a single isolated dc source. Hence, the required number of secondary windings is considerably reduced. This approach also minimizes the complexity and cost of the overall system. The operation of the proposed topology is presented by using three-level neutral point clamped modules in each phase. Model predictive control (MPC) is employed to control the dc-bus capacitor voltage and output currents of the proposed topology. A discrete-time mathematical model of the proposed topology is also developed to predict the future behavior of control variables. The performance of the proposed topology with MPC is verified through MATLAB simulations and a scaled-down laboratory prototype.

The modular medium-frequency transformer (MFT)-based current source converter is considered a promising topology for wind energy conversion systems. The use of modular MFT-based converter, however, introduces a potential issue, that is the capacitor voltage imbalance due to mismatches among the constituent modules of the modular converter. Model predictive control (MPC) with high dynamic performance is increasingly used in high power converters, but here, it suffers high computational burden and poor control performance due to high number of switching states. To solve this issue, a simplified MPC with better control performance is proposed to ensure capacitor voltage balancing without compromising the performance of traditional MPC. The operation principle and performance of the simplified MPC are illustrated and verified by experiments.

Suitable space vector modulation (SVM) schemes for current-source inverters (CSIs) with leakage current mitigation capability has not been well explored yet. In this study, a novel SVM scheme is proposed, with which the leakage current in a CSI-based transformerless photovoltaic system can be significantly suppressed. Finally, some simulations are carried out on a three-phase current-source converter (CSC), the results verify the effectiveness of the proposed SVM scheme.

Pulsewidth modulation current source converter (CSC)-based drive is one of the widely used drives in high-power (megawatt level) medium-voltage (MV) (2.3-6.6 kV) applications. The switching frequency of the MV CSC is limited to around 500 Hz to satisfy thermal requirement and reduce switching loss. Under such a condition, the overall performance of the used modulation scheme, especially its harmonics performance, is an important consideration for CSC-based drives. To date, a couple of modulation schemes have been proposed for MV CSCs, and this paper aims to present an overview of these modulation schemes. Traditional modulation schemes are reviewed, the recent advances are illustrated and analyzed, and the challenges and trends are discussed.