Unbalanced grids introduce performance deterioration for Vienna rectifier topology by producing twice fundamental frequency ripples in dc-link voltage and input active/reactive power. A common current reference generation for the purpose of eliminating the input power ripple, such as dual-frame hybrid vector control, can maintain constant input power and eliminate ripples in dc-link voltage under light voltage unbalanced grids. Under severe unbalanced grids, this type of a control method will fail to work. This paper first analyzes the theoretical operation area of a constant power control method under unbalanced grids, and then a novel control method is proposed. The proposed control method can work under severe unbalanced grids by injecting a small amount of input power ripple and balance the performance of working area and output dc voltage ripples. Finally, the experiment results using the constant power control method are given and validate the performance of the proposed control method.

This paper presents highly efficient three-phase high-power-factor hybrid rectifiers assembled by the parallel connection of a three-phase diode-bridge rectifier and series dc-dc boost converter with a two- or three-level unidirectional pulse width modulation (PWM) rectifier. The idea is to obtain a rectifier that is robust, highly efficient, and simple as a diode-based rectifier and also able to benefit from the PWM rectifier capability to reduce the line current harmonic content. Exemplary three-phase unidirectional hybrid systems built with a two-level delta-switch rectifier and three-level T-type or VIENNA six-switch rectifiers are suggested. Additionally, control schemes, which are appropriate for safeguarding the high-power-factor operation while improving the power sharing rating of the hybrid paralleled rectifier units and able to handle a phase loss without changing the controller structure, are proposed. In order to evaluate the studied hybrid rectifiers, first, an efficiency comparison between two- and three-level hybrid systems with conventional PWM rectifiers is performed. After that, the loss calculations are extended to a variable chip area to allow a fair comparison between these rectifiers. Interestingly, it is shown that the presented hybrid systems not only can achieve a higher efficiency but also require less silicon area than the single PWM rectifiers they are based on. Finally, experimental results obtained with an assembled unidirectional hybrid delta-switch rectifier prototype are presented in order to demonstrate the performance and advantages of this solution.

三相三电平VIENNA整流器作为三电平Boost型中点箝位(neutral point clamped，NPC)结构变换器一种，具有电路结构简单、开关电压应力小、输入电流谐波含量低、可实现输入单位功率因数校正等优点，适合应用于高压中大功率场合。同时，三相功率因数校正(power factor correction，PFC)整流器的单周期控制方案因其控制简单，无需乘法器及采用输入电压受到广泛研究。输出中点电位波动是NPC结构变换器的一个固有问题，以基于单周期控制的三相三电平VIENNA整流器为研究对象，详细地分析整流器输出中点电位波动机理，根据单周期控制方案的特点，提出在三相输入电流采样中注入三次谐波电流分量，同时分析三次谐波电流注入后对整流器输出中点电位的影响，给出三次谐波电流最佳注入系数。在此基础之上，向传统单周期控制系统中继续引入均压环路，使得最终改进后的三相三电平VIENNA整流器单周期控制系统一方面可以提高整流器直流母线电压利用率，另一方面可以有效抑制中点电位的直流和交流波动。仿真与实验验证了所提出的改进单周期控制策略对于整流器输出中点电位平衡控制的有效性。

三相三电平VIENNA整流器作为三电平Boost型中点箝位(neutral point clamped，NPC)结构变换器一种，具有电路结构简单、开关电压应力小、输入电流谐波含量低、可实现输入单位功率因数校正等优点，适合应用于高压中大功率场合。同时，三相功率因数校正(power factor correction，PFC)整流器的单周期控制方案因其控制简单，无需乘法器及采用输入电压受到广泛研究。输出中点电位波动是NPC结构变换器的一个固有问题，以基于单周期控制的三相三电平VIENNA整流器为研究对象，详细地分析整流器输出中点电位波动机理，根据单周期控制方案的特点，提出在三相输入电流采样中注入三次谐波电流分量，同时分析三次谐波电流注入后对整流器输出中点电位的影响，给出三次谐波电流最佳注入系数。在此基础之上，向传统单周期控制系统中继续引入均压环路，使得最终改进后的三相三电平VIENNA整流器单周期控制系统一方面可以提高整流器直流母线电压利用率，另一方面可以有效抑制中点电位的直流和交流波动。仿真与实验验证了所提出的改进单周期控制策略对于整流器输出中点电位平衡控制的有效性。

This study presents an analytical approach for proper selection of output functions to be regulated for the Vienna rectifier such that the resultant closed-loop systems are minimum phase. Specifically, two different adaptive control methodologies based on the input-output linearisation are developed and categorised. In the first category, three output functions are introduced and imposed to be zero by using three dynamic feedback laws. On the basis of states to be regulated, four different cases are studied and it is shown that only one of these cases results in a one-dimensional zero dynamics with an asymptotically stable equilibrium point. In the second category, two output functions are defined and output zeroing problem is solved with two control inputs. In addition, the remaining control is used to feedback linearise the resultant two-dimensional zero dynamics. Eighteen different cases are studied to demonstrate that only in one of these cases, the corresponding zero dynamics is feedback linearisable. Stability properties of the adaptive systems are investigated to show that the proposed adaptive controllers are capable of DC output voltage regulation and power factor correction in the presence of parametric and non-parametric uncertainties. Finally, simulation results are presented to confirm the validity of the developed approaches.

In view of the nonlinear mathematical model of the photovoltaic(PV) grid-connected inverter, the passivity-based control(PBC) is adapted for the inverter, and it can make the inverter possess excellent dynamic and static characteristics. In this paper the control law that can decouple dq axis currents at AC side of the grid based on the Euler-Lagrange(EL) model, and the passivity of inverter is proved. In order to improve the dynamic performance of the inverter, we can adopt the approach called injecting damping to optimize the controllerps adopted, and it can also make the current to fast track the desired one and track the PV array maximum power point. Simulation and 4kW prototype results show that the current control strategy of Photovoltaic grid-connected inverter based on passivity is practicable.

In view of the nonlinear mathematical model of the photovoltaic(PV) grid-connected inverter, the passivity-based control(PBC) is adapted for the inverter, and it can make the inverter possess excellent dynamic and static characteristics. In this paper the control law that can decouple dq axis currents at AC side of the grid based on the Euler-Lagrange(EL) model, and the passivity of inverter is proved. In order to improve the dynamic performance of the inverter, we can adopt the approach called injecting damping to optimize the controllerps adopted, and it can also make the current to fast track the desired one and track the PV array maximum power point. Simulation and 4kW prototype results show that the current control strategy of Photovoltaic grid-connected inverter based on passivity is practicable.

The effects of low-protein diet (LPD) on kidney function and nutrition in nephropathy are so far unclear.

The effects of low-protein diet (LPD) on kidney function and nutrition in nephropathy are so far unclear.