单相光伏并网功率调节系统的研究

发布时间：2018-03-25 13:36

本文选题：光伏并网功率调节系统　切入点：功率前馈　出处：《天津大学》2014年硕士论文

【摘要】：随着能源和环境问题的日益突出,作为清洁能源的太阳能越来越受到重视。大量非线性和冲击性负载的出现,其产生的谐波及无功电流对公共电网的污染也日益严重。为缓解这一问题,电力有源滤波器成为国内外究的重点。常用的光伏发电中全桥拓扑结构与有源电力滤波器相同,将光伏发电和有源电力滤波器结合在一起,组成光伏并网功率调节系统(Photovoltaic power conditioning system,PVPCS),在向电网注入有功功率的同时,补偿非线性负载的无功和谐波电流。既提高了设备的利用率,节省了投资,又改善了配电网的电能质量。PVPCS采用传统PI电压外环和准比例谐振(Quasi Proportional Resonant,Quasi-PR)电流内环的双环控制策略。主要存在两方面的问题:一是当光照和温度等环境参数突变时,光伏输出功率与并网功率不平衡,在传统PI电压外环控制下,直流侧电压超调量大,动态响应时间长,并网电流的总谐波失真增大,甚至可能威胁PVPCS的稳定性。二是Quasi-PR电流内环往往采用数字控制实现,从而引入采样、零阶保持和滞后一拍等环节,使PVPCS电流内环稳态和动态性能下降,并网电流的总谐波失真增大,动态响应时间增大。针对以上存在的两方面问题,本文以两级式单相光伏并网功率调节系统为例,从理论上分析了传统控制策略造成直流侧电压波动的机理和数字控制对电流内环的影响,设计了功率前馈电压外环和预测控制电流内环的新型双环控制策略,并确定了控制参数。仿真结果表明,数字控制使电流内环控制器和控制对象特性发生变化,系统阶数升高,相位滞后增大,开关频率及其整数倍频率出现谐振,并伴随有相位的跳变,控制参数的稳定域缩小;受稳定性的制约,稳态精度和动态性能也下降,采样频率越低时上述影响越突出。功率前馈电压外环能减小直流侧电压的波动,并减少动态响应时间。预测控制的电流内环能够提前一拍输出控制量,从而减小数字控制的不利影响,减小并网电流的总谐波失真和动态响应时间。PVPCS系统在新型控制策略下,实现了对本地非线性负载无功与谐波电流的补偿,同时将光伏阵列发出的功率最大程度地注入到电网中。本文对PVPCS进行了仿真与实验的验证。在MATLAB中建立PVPCS的仿真模型,并对传统控制策略和新型控制策略进行比较。同时对基于DSP控制1kW的PVPCS实验平台进行了软硬件设计,通过实验验证本文分析正确性。
[Abstract]:With the increasingly prominent energy and environmental problems, solar energy, as a clean energy, has received more and more attention. A large number of nonlinear and impact loads appear. In order to alleviate this problem, active power filter (APF) has become the focus of research at home and abroad. The full-bridge topology of photovoltaic power generation is the same as active power filter (APF). Combining photovoltaic power generation with active power filter, the photovoltaic power conditioning system PVPCSs are formed to compensate the reactive power and harmonic current of nonlinear load while injecting active power into the power network. It saves the investment and improves the power quality of the distribution network. PVPCS adopts the traditional Pi voltage outer loop and the quasi-proportional resonant quasi Proportional Proportional quasi-PRA current inner loop. There are two main problems: first, when the environmental parameters such as light and temperature change, Under the traditional Pi voltage outer loop control, the DC side voltage overshoot is large, the dynamic response time is long, and the total harmonic distortion of grid-connected current increases. It may even threaten the stability of PVPCS. Second, the Quasi-PR current inner loop is often realized by digital control, thus introducing sampling, zero order holding and lagging one beat, so that the steady-state and dynamic performance of PVPCS current inner loop is reduced. The total harmonic distortion of grid-connected current increases and the dynamic response time increases. In view of the above two problems, this paper takes the two-stage single-phase photovoltaic grid-connected power regulation system as an example. The mechanism of DC side voltage fluctuation caused by traditional control strategy and the influence of digital control on current inner loop are analyzed theoretically. A new double loop control strategy for power feedforward voltage outer loop and predictive control current inner loop is designed. The simulation results show that the digital control changes the characteristics of the current inner loop controller and the control object, increases the system order, increases the phase lag, and resonates with the switching frequency and its integer frequency. Along with the jump of phase, the stable range of control parameters is reduced, and the steady-state precision and dynamic performance are also decreased due to the stability. The lower the sampling frequency is, the more obvious the effect is. The power feedforward voltage outer loop can reduce the fluctuation of DC side voltage. And reduce the dynamic response time. The inner loop of predictive control can beat out the control quantity in advance, thus reducing the adverse effect of digital control, reducing the total harmonic distortion of grid-connected current and dynamic response time. PVPCS system is under the new control strategy. The compensation of local nonlinear load reactive power and harmonic current is realized, and the maximum power emitted by photovoltaic array is injected into the power grid. The simulation and experiment of PVPCS are carried out. The simulation model of PVPCS is established in MATLAB. The traditional control strategy and the new control strategy are compared. At the same time, the software and hardware of the PVPCS experimental platform based on DSP control 1kW are designed, and the correctness of the analysis is verified by experiments.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM615

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