单相光伏并网逆变器共模漏电流和无功补偿的研究

发布时间：2018-02-15 03:18

本文关键词： 光伏并网发电漏电流新型双BUCK逆变器无功补偿数字控制　出处：《扬州大学》2014年硕士论文　论文类型：学位论文

【摘要】：逆变器是太阳能光伏并网发电系统的重要组成部分,在太阳能的发展和利用过程中占有核心地位。为确保光伏并网发电系统的可靠运行,传统的并网逆变器使用变压器进行电气隔离,因此系统存在体积大、重量重、效率低、成本高等诸多缺点,而非隔离型光伏并网逆变器均克服了已上缺点,已成为当前研究的热点。非隔离光伏并网逆变器由于变压器的去除会在电路中产生共模干扰,并会使并网逆变系统和地之间形成共模漏电流而带来安全隐患。因此,解决并网逆变器共模漏电流至关重要。论文首先以单相全桥非隔离光伏并网逆变器为例,对其建立共模漏电流模型,分析了该逆变器在不同的PWM调制方式下的共模特性,总结出了消除共模漏电流的方法。随后,论文研究了四种改进型非隔离光伏并网逆变器的共模特性,通过仿真比较了这四种逆变器的漏电流抑制效果,并总结出它们各自的优缺点。为了提高系统的效率和避免同一桥臂的功率管直通问题,本文重点研究了一种新型双BUCK非隔离光伏并网逆变器拓扑,它具有输入直流电压利用率高,无桥臂功率管直通、共模漏电流小等优点。论文对这种新型双BUCK逆变器的工作原理进行了分析,对主要参数进行了设计,通过对该逆变器的效率分析和计算,优化选择了功率开关器件。实验表明新型双BUCK逆变器的漏电流抑制效果和效率均优于目前使用较多的H6桥逆变器。德国于2011年8月颁布了《分布式电源接入低压配电网运行管理规定》,即VDE-AR-N4105标准。该规定明确表明总视在功率大于4.6kVA的并网逆变器,均要求能够对电网实施无功补偿。为了使逆变器做到低漏电流和高效率,大部分非隔离型并网逆变器均采用传统的单极性调制,但在进行无功功率补偿时,并网电流在电网电压过零点发生畸变,因此在很大程度上加大了并网电流的总谐波畸变率,同时还会导致功率因数不能满足±0.01的误差范围要求。本文以新型双BUCK非隔离光伏并网逆变器为例,在实施无功补偿时存在的并网电流畸变问题进行了详细的分析和研究,并提出了一种新的调制策略改变低频管的控制方式,有效的解决了该问题。仿真和实验验证了本文所研究方法的正确
[Abstract]:Inverter is an important part of solar photovoltaic grid-connected power generation system and plays a core role in the development and utilization of solar energy. In order to ensure the reliable operation of photovoltaic grid-connected power generation system. Traditional grid-connected inverters use transformers for electrical isolation, so the system has many shortcomings, such as large volume, heavy weight, low efficiency, high cost and so on. It has become the hot spot of current research. The unisolated photovoltaic grid-connected inverter will cause common-mode interference in the circuit and cause the common mode leakage current between the grid-connected inverter system and the ground because of the removal of the transformer. Therefore, the common mode leakage current will be formed between the grid-connected inverter system and the ground. It is very important to solve the common mode leakage current of grid-connected inverter. Firstly, taking single-phase full-bridge non-isolated photovoltaic grid-connected inverter as an example, the common mode leakage current model is established, and the common-mode characteristics of the inverter under different PWM modulation modes are analyzed. The common mode characteristics of four improved non-isolated photovoltaic grid-connected inverters are studied, and the effects of the four kinds of inverters are compared by simulation. Their advantages and disadvantages are summarized. In order to improve the efficiency of the system and avoid the problem of passing through of power tube with the same bridge arm, a new type of double BUCK non-isolated photovoltaic grid-connected inverter is studied in this paper. It has high efficiency of input DC voltage, and no bridge arm power tube is straight through. In this paper, the working principle of this new double BUCK inverter is analyzed, the main parameters are designed, and the efficiency of the inverter is analyzed and calculated. The experimental results show that the leakage current suppression effect and efficiency of the new double BUCK inverter are better than that of the H6 bridge inverter which is widely used at present. In August 2011, Germany promulgated the "distributed Power supply access low Voltage Distribution Network Operation Management Regulation", or VDE-AR-N4105 Standard, which clearly indicates that the total apparent power is greater than 4.6 kVA for grid-connected inverters. In order to make the inverter achieve low leakage current and high efficiency, most non-isolated grid-connected inverters adopt traditional unipolar modulation, but in the reactive power compensation, The total harmonic distortion rate of grid-connected current is greatly increased due to the distortion of grid voltage over 00:00. At the same time, the power factor can not meet the 卤0. 01 error range. In this paper, the problem of grid-connected current distortion existing in the implementation of reactive power compensation is analyzed and studied in detail, taking a new type of double BUCK non-isolated photovoltaic grid-connected inverter as an example. A new modulation strategy is proposed to change the control mode of the low frequency tube, which effectively solves the problem. The simulation and experiment verify the correctness of the method studied in this paper.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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