A New PV Converter for Grid Connection Through a High‐Leg Delta Transformer Using Cooperative Control of Boost Converters and Inverters

This paper proposes a new high‐efficiency photovoltaic (PV) converter for grid connection through a high‐leg delta transformer, which is composed of a symmetrically connected boost converter and three half‐bridge inverters. One of the three half‐bridge inverters is connected to the boost converter, and the others are directly connected to the PV terminals. This circuit configuration enables to reduce the power losses in both boost converter and inverter. This paper also proposes a new cooperative control method between the symmetrically connected boost converter and inverter. The control method can reduce the average switching frequency to 75% of that in a conventional one, resulting in a great reduction in switching power loss. Experimental results show that the proposed circuit improves its European efficiency from 91.6% to 94.5%.     

面向需求响应的变频空调负荷建模与运行控制

近年来,空调类电力用户数量迅速增加,成为了电网高峰负荷的主要组成部分。空调负荷作为典型柔性负荷,可利用其热惯性参与需求响应,为电网提供有效可调容量。区别于有关定频空调的研究,基于变频空调的负荷特性构建其物理模型,从控制后总功率和最大控制时长两个维度对变频空调集群的调节潜力进行评估。在此基础上,根据变频空调负荷聚合商在需求响应日前市场的成交量,以变频空调集群功率削减量与成交量偏差以及用户舒适度变化量最小化为目标,提出了基于双层分组轮控的变频空调负荷优化控制策略。仿真结果表明,所提策略不仅能够通过分组轮控延长变频空调集群最大控制时长,还具有良好的用户友好性,对于变频空调集群参与电网需求响应具有指导意义。     

参与调峰控制的空调负荷建模仿真研究

调控空调负荷参与电网削峰填谷对于维持系统稳定运行、减少发电机备用容量提高效率,从而增大电网运行效益具有巨大潜力。基于家用分散式空调的工作原理,在MATLAB/Simulink环境下搭建了简化空调房调温模型,以该模型为基础依次探究了定/变频空调调温、增大变频区间调温的特性。考虑空调的工作特性,提出了一种对空调控制系统进行简单改造,使其自适应电网预测负荷大小进行互补运行的策略。最后开展基于RT-LAB实时仿真平台的模型仿真测试与试验,验证了仿真模型的正确性以及控制策略促进空调负荷参与调峰控制的有效性。     

Interleaved step-up converter with a single-capacitor snubber for PV energy conversion applications

In this paper, an interleaved step-up converter with a single-capacitor snubber for PV energy conversion applications is proposed. The step-up converter adopts two sets of boost converters with an interleaved fashion and coupled-inductor technology to reduce output ripple current and increase output power level. To achieve higher conversion efficiency and reduce switching losses of the proposed converter, a lossless single-capacitor turn-off snubber is introduced. Therefore, the conversion efficiency can be increased significantly. In order to draw the maximum power from the PV arrays, a perturbation-and-observation method and a microcontroller are associated to implement maximum power point tracking (MPPT) algorithm and power regulating scheme. Finally, a prototype of a soft-switching interleaved soft-switching boost converter with coupled inductors has been built and implemented. Experimental results have obtained to verify the performance and feasibility of the proposed converter for PV arrays applications.     

Boost型无频闪谐振降压式LED驱动电源分析与设计

传统的二次型Boost功率因数校正变换器只能实现升压输出,在一定程度上限制了其在LED驱动电源中的应用。本文基于二次型Boost变换器提出了一种Boost型无频闪谐振降压式LED驱动电源,并分析了其工作原理及特性。该LED驱动电源利用一个有源开关管将二次型Boost变换器与一个谐振网络进行整合。与传统的二次型Boost变换器相类似,该LED驱动电源可以实现高效率和高功率因数。此外,该LED驱动电源可实现低电流纹波和降压变换输出。最后,搭建了一台84W的实验样机,最高效率可达到92.88%,验证了理论分析的正确性及可行性。     

A novel active‐clamp zero‐voltage‐switching buck‐boost converter

An active‐clamp zero‐voltage‐switching (ZVS) buck‐boost converter is proposed in this paper to improve the performance of converter in light load condition. By employing a small resonant inductor, the ZVS range of switches could be adjusted to very light load condition. Moreover, 2 clamping capacitors are added in the converter to eliminate the voltage spike on the switches during transition. The operating principle of the proposed converter is analyzed, and the optimal design guide for full range ZVS is also provided. A 60‐W output prototype is experimentally built and tested in laboratory to verify the feasibility of proposed converter. The measured results show the critical ZVS operation of power switches at 1 and 0.7‐W output power for buck and boost mode, respectively. The peak conversion efficiency is up to 92.3%.     

需求响应参与电力系统调频的模糊控制策略

针对传统电力系统调频响应延时长、机组能耗大的问题,提出了一种需求响应参与电力系统调频的模糊控制策略。该策略从需求侧入手,将变频空调作为可控负荷;按照变频空调的出力能力,将参与电力系统调频的所有变频空调进行分类,并引入权重因子,实现对不同类型变频空调的聚合控制;根据系统的运行状态,通过模糊控制规则调节参与需求响应中各类变频空调的出力,辅助发电机组改善系统的动态调频性能。仿真实验结果表明,采用该策略可显著提高频率调节速度和降低超调,并在一定程度上降低调频能耗,有助于改善电网的调频性能。     

变频空调器节能分析

变频空调器节能问题到目前为止还有不少争论,国家标准对变频空调器和定频空调器的能效指标不同,没有可比性。文章通过对变频空调器和定频空调器在同等条f#-T进行测试和计算对比,对变频空调器节能情况和优缺点进行客观评价,对各类人群选用空调器具有一定指导作用。     

Advanced power conditioner using sinewave modulated buck–boost converter cascaded polarity changing inverter

This paper presents an advanced power converter employs a sinusoidal voltage absolute value tracking buck–boost DC–DC converter in the first power processing stage and a polarity changing full-bridge inverter in the second stage. The proposed power conversion system has the capability of delivering good quantitative and qualitative sinusoidal output current and voltage waveforms with good output voltage regulation. Consequently, the complete voltage regulator system, which is mainly suitable for new energy generation systems as well as energy storage systems, can be constructed compactly and inexpensively without DC link electrolytic capacitor. Also, the paper presents an auxiliary passive resonant circuit for soft switching operation. Simulation results using PSIM software are presented to verify the operation principles and feasibility of the proposed power conversion system. Finally, these results are verified by means of an experimental prototype.     

Extend output voltage range of AC/AC converters using a reversible indirect matrix converter

This paper proposes a reversible indirect matrix converter that expands the output voltage range. The proposed circuit has two operation modes. A buck mode that supplies an output voltage lower than the input voltage, and a boost mode that supplies an output voltage higher than the input voltage. In the boost mode, the proposed circuit has the characteristics of the current type inverter therefore, it is possible to obtain an output voltage with less harmonics. The proposed system is validated with a 2 kW prototype. The proposed circuit shows that the input/output voltage ratio of AC/AC direct conversion obtained is 0 to 1.2 or more. Moreover, the conversion efficiency of the proposed circuit is 92.8%.