LCL型光伏并网逆变器谐振抑制及锁相方法的研究

发布时间：2019-03-24 21:21

【摘要】：近年来，各国都加大了对太阳能、风能、地热、潮汐等新能源的开发和利用，然而，分布式电源所发出的直流电无法直接供给电网和交流负载，必须经过一定的接口设备方可实现并网，光伏(PV)发电并网通常采用的是电压源型电流控制逆变器。目前，LCL滤波型并网逆变器受到广泛应用，但是其结构决定了它会产生谐振，使得并网电流THD升高，甚至使其无法满足并网条件，为了保证并网电流质量，必须采取措施抑制谐振。此外，并网逆变器要想实现高效率并网，还必须保证并网电流与电网电压同频同相，因此同步锁相技术的研究尤为重要。所以，光伏并网逆变器如何实现谐振抑制与电网同步技术是本文的研究重点。本文从分析光伏发电原理及其数学模型入手，搭建了通用性很强的光伏电池模型，通过仿真对光伏电池特性以及扰动观察法进行了研究。建立了LCL型光伏并网逆变器模型，给出了LCL滤波参数的设计，，为研究光伏并网逆变器运行奠定了基础。详细分析了并网运行时采用的SVPWM调制策略和PQ控制方法，根据他们的实现原理建立了各自的仿真模型，通过仿真验证这两种控制模型的正确性，为并网运行提供了控制方法。针对LCL型光伏并网逆变器产生的谐振问题，采用阻尼控制策略，分别分析了电容支路串联电阻的无源阻尼法以及电容电流反馈的有源阻尼法机理，仿真从并网电流波形质量和谐波频谱方面验证了他们具有良好的谐振抑制效果。研究了逆变器功率变化时采用无源/有源阻尼双模式控制方法，对其切换过程进行了仿真，验证了其切换过程平滑，并网电流THD符合并网条件，方案具有可行性。分析了SSRF SPLL原理并进行了常见电网状况下的仿真，其在电网电压幅值不平衡和单相接地故障时锁相性能不理想，随后根据DDSRF SPLL锁相原理，建立解耦模型，通过仿真验证DDSR SPLL能够解决电网电压幅值不平衡及单相接地故障时的锁相问题。通过理论分析得到PI控制下并网电流与电网电压之间存在相位差，针对该问题采用相位补偿的方法实现并网电流与电网电压准确同步，保证了单位功率因数并网，仿真结果验证了方案的正确性。
[Abstract]:In recent years, countries have increased the development and utilization of new energy sources, such as solar energy, wind energy, geothermal energy, tidal energy, and so on. However, the direct current emitted by distributed power sources cannot be directly supplied to the grid and AC load. Grid-connected photovoltaic (PV) is usually connected with a voltage-source current-controlled inverter. At present, LCL filter grid-connected inverter is widely used, but its structure determines that it will produce resonance, make the grid-connected current THD increase, even make it unable to meet the grid-connected conditions, in order to ensure the quality of grid-connected current, Measures must be taken to suppress resonance. In addition, in order to achieve high-efficiency grid-connected inverter, grid-connected current and grid voltage must be in the same frequency and phase, so the research of synchronous phase-locked technology is particularly important. Therefore, how to achieve resonance suppression and grid synchronization technology of photovoltaic grid-connected inverter is the focus of this paper. Based on the analysis of the principle and mathematical model of photovoltaic power generation, a photovoltaic cell model with strong generality is built in this paper. The characteristics and disturbance observation method of photovoltaic cell are studied by simulation. The model of LCL photovoltaic grid-connected inverter is established, and the design of LCL filter parameters is given, which lays a foundation for studying the operation of photovoltaic grid-connected inverter. The SVPWM modulation strategy and PQ control method used in grid-connected operation are analyzed in detail, and their simulation models are established according to their realization principle. The correctness of these two control models is verified by simulation, which provides a control method for grid-connected operation. In order to solve the resonance problem of LCL photovoltaic grid-connected inverter, the passive damping method of capacitor branch series resistance and the active damping method of capacitor current feedback are analyzed by using damping control strategy. The simulation results show that the grid-connected current waveform quality and harmonic spectrum show that they have good resonance suppression effect. The passive / active damping dual-mode control method for inverter power change is studied. The simulation results show that the switching process is smooth and the grid-connected current THD accords with the grid-connected condition. The scheme is feasible. In this paper, the principle of SSRF SPLL is analyzed and the simulation of common grid conditions is carried out. The phase locking performance is not satisfactory when the voltage amplitude is unbalanced and the single phase to ground fault. Then, according to the principle of DDSRF SPLL phase locking, the decoupling model is established. The simulation results show that DDSR SPLL can solve the phase-locked problem of unbalanced voltage amplitude and single-phase-to-earth fault. The phase difference between grid-connected current and grid voltage under the control of PI is obtained by theoretical analysis. Aiming at this problem, phase compensation is adopted to realize accurate synchronization between grid-connected current and grid voltage, and the unit power factor is guaranteed to be connected to the grid. The simulation results verify the correctness of the scheme.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464;TM615

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