A new model predictive control algorithm by reducing the computing time of cost function minimization for NPC inverter in three-phase power grids

This paper presents a new control strategy based on finite-control-set model-predictive control (FCS-MPC) for Neutral-point-clamped (NPC) three-level converters. Containing some advantages like fast dynamic response, easy inclusion of constraints and simple control loop, makes the FCS-MPC method attractive to use as a switching strategy for converters. However, the large amount of required calculations is a problem in the widespread of this method. In this way, to resolve this problem this paper presents a modified method that effectively reduces the computation load compare with conventional FCS-MPC method and at the same time does not affect on control performance. The proposed method can be used for exchanging power between electrical grid and DC resources by providing active and reactive power compensations. Experiments on three-level converter for three Power Factor Correction (PFC), inductive and capacitive compensation modes verify the good and comparable performance. The results have been simulated using MATLAB/SIMULINK software.     

Synthesis and design of tunable bandpass filters with constant absolute bandwidth using varactor‐loaded microstrip resonator

This article presents two new types of tunable filters with constant absolute bandwidth using varactor‐loaded microstrip resonators. First, the second‐ and third‐order Butterworth tunable filters are designed based on the parallel coupled‐line J inverters. Second, a fourth‐order Chebyshev tunable filter is designed based on the alternative J/K inverters, in this design, two adjacent resonators are coupled with each other through a short‐circuited transmission line as the K inverter. The proposed two topologies can be easily extended to high‐order tunable filter. Three tunable bandpass filters with J and alternative J/K inverters, respectively, are built with a tuning range from ～1.8 to ～2.3 GHz. The measured second‐order filter has a 3‐dB bandwidth of 160 ± 6 MHz and an insertion loss of 2.4–3.8 dB. The third‐order filter shows a 3‐dB bandwidth of 197 ± 5 MHz and an insertion loss of 3.8–4.8 dB. The fourth‐order filter shows a 3‐dB bandwidth of 440 ± 5 MHz and an insertion loss of 2.1–2.6 dB. For all the designed filters, the measured results are found in excellent agreement with the predicted and simulated results. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:681–689, 2014.     

基于合作博弈理论和马尔可夫过程融合的逆变器故障率动态分析

以光伏并网系统中三相电压型PWM逆变器为例,采用合作博弈理论和马尔可夫过程融合的故障率分析方法.首先,根据逆变器的基本工作原理,通过引入马尔可夫过程,得到逆变器工作状态转移概率图和转移概率矩阵,并设定转移概率矩阵的初始表达形式;然后,获得转移概率矩阵中关键元素m、n的3组常规不同值,并采用合作博弈理论确定m、n的最优值...     

Advances in reduction of total harmonic distortion in solar photovoltaic systems: A literature review

The use of photovoltaic (PV) systems has increased in recent years due to the high demand for clean energy sources. PV systems can utilize abundant and free energy from the sun, which is a substantial advantage. However, compared with other renewable technologies, the PV system still faces major obstacles such as high cost and low efficiency. In addition, fluctuating incident energy from the sun creates harmonics in the generated power that might lead to undesirable system performance. Total harmonic distortion (THD) is the ratio of distorted power to the main power of the signal, and is most commonly used to indicate the amount of signal distortion. THD has become a serious concern as more PV systems are integrated into grid systems. Previous research and reviews have attempted to reduce THD and its effect, but unfortunately focused on reducing THD at individual parts of the PV system. For the first time, this study holistically and systematically reviews the advances in THD reduction techniques for the entire PV system. The causes of harmonics, current solutions, and research gaps for further investigation are described in detail. Moreover, the current THD reduction techniques used in each stage of the PV system are compared, including their main benefits and drawbacks. Finally, this study recommends the use of adaptive filters as a possible solution for THD reduction because these filters have effectively reduced noise and disturbance in other systems.     

孤岛微电网逆变器不平衡负载下的控制策略

提出一种孤岛微电网逆变器在不平衡负载下的控制策略,采用分序网络解耦控制,在虚拟同步发电机(VSG)控制的基础上引入自适应负序补偿环.对三相负载不平衡下的电路进行分析,得到逆变器分序网络等效电路和逆变器间负序环流产生机理.通过分序网络解耦控制得到电压环参考电压各序分量,引入分序网络虚拟阻抗改进逆变器各序输出阻抗.正序网络...     

On‐site characterisation and energy efficiency of grid‐connected PV inverters

The size of inverters in large grid‐connected photovoltaic (PV) systems is increasing. At present, the largest installed inverters have nominal powers of several hundreds of kW, which makes their characterisation in the laboratory difficult. As an alternative, on‐site characterisation requires only measurement equipment and has the advantage that the inverter is tested in its own PV system under real operating conditions. This paper describes an on‐site testing procedure for assessing the power efficiency of an inverter and the results obtained for 13 inverters with nominal powers between 3.3 and 350 kW. The inverters were tested in PV grid‐connected systems whose aggregate power capacity is nearly 150 MW. The energy efficiency of the inverters tested was also calculated yearly, and the results were compared with both European and Californian energy efficiency parameters, which are widely used in the current PV market. Copyright © 2010 John Wiley & Sons, Ltd.