低压微电网分布式单元并联运行的控制策略研究

发布时间：2018-11-11 21:54

【摘要】：可再生能源与储能装置、电力电子装置等相结合构成微电网，逆变器是微电网能够实现并网的电力电子接口，在微电网的运行与控制中起着重要作用。当微电网运行于孤岛模式时，下垂控制是实现多DG间功率均分的常用方法，但由于线路阻抗和本地负荷的不一致将会产生环流，降低系统效率。为了减小或消除环流、实现各逆变器输出功率均分，本文提出了基于自适应调节下垂系数的控制方法。考虑到低压系统线路阻抗呈阻性，因此该策略是在P-V下垂控制基础上实现的。实现过程为：以任一台逆变器为主机，对其采用传统P-V下垂控制，将其输出有功功率传送到从机中，从机以两台逆变器输出有功功率差值来自适应调节自身的P-V下垂系数，最终使系统输出有功功率一致、系统环流减小。该策略与现有环流抑制方法相比简单易行、输出电压精度高并在考虑本地负荷的情况下仍能实现功率均分。但以上方法的实现需要线路阻抗参数，同时考虑到在并网模式下线路阻抗检测准确度受电网等效阻抗(包括电网阻抗和公共耦合点到电网的线路阻抗)的影响，本文提出了在并网模式下考虑电网等效阻抗的多机线路阻抗检测方法。其采用下垂控制策略并通过参考电压变化的手段，在构建的虚拟单机阻抗网络等效模型基础上，实现电网等效阻抗和各线路阻抗的检测。该检测方法简单可靠，，并在考虑了电网等效阻抗的基础上，只需通过一次扰动便能检测出电网等效阻抗和各线路阻抗。以上控制方案通过了仿真和基于TMS320F2812DSP控制芯片的三相逆变器并联实验平台的验证，仿真和实验结果都验证了理论分析的准确性和可行性。
[Abstract]:The combination of renewable energy and energy storage devices, power electronic devices and so on constitutes a microgrid. The inverter is a power electronic interface that can be connected to the grid, and plays an important role in the operation and control of microgrid. When microgrid operates in isolated island mode, droop control is a common method to realize power equalization between multiple DG. However, because of the inconsistency of line impedance and local load, circulation will be produced and system efficiency will be reduced. In order to reduce or eliminate the circulation and realize the average output power distribution of each inverter, a control method based on adaptive regulation of sag coefficient is proposed in this paper. Considering that the line impedance of low voltage system is resistive, this strategy is realized on the basis of P-V droop control. The realization process is as follows: take any inverter as the host, adopt the traditional P-V droop control, and transfer the output active power to the slave. The difference of active power output from two inverters comes from adjusting their P-V sag coefficient, which finally makes the output active power of the system consistent and the circulation of the system reduced. Compared with the existing current suppression methods, the proposed strategy is simple and feasible, with high output voltage accuracy and the ability to achieve power equalization even when local load is taken into account. However, the realization of the above method requires line impedance parameters, and considering that the accuracy of line impedance detection in grid-connected mode is affected by the equivalent impedance of the power network (including the network impedance and the line impedance from the common coupling point to the power network). In this paper, a multi-machine line impedance detection method considering grid equivalent impedance in grid-connected mode is proposed. Based on the virtual single-machine impedance network equivalent model, the equivalent impedance of the power network and the impedance of each line can be detected by using the droop control strategy and the reference voltage variation method. The method is simple and reliable. On the basis of considering the equivalent impedance of the power network, the equivalent impedance and the impedance of each line can be detected by only one disturbance. The control scheme is verified by simulation and parallel experiment platform of three-phase inverter based on TMS320F2812DSP control chip. Both simulation and experimental results verify the accuracy and feasibility of theoretical analysis.
【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】：TM732

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