分布式风光互补微网系统双模式逆变器控制研究

发布时间：2018-04-10 19:35

本文选题：双模式逆变器 + 不平衡电网　；参考：《北方工业大学》2017年硕士论文

【摘要】：运行于微电网下独立和并网两种模式的双模式逆变器,难免会遇到电网三相电压不平衡的状况。三相电压对称度作为微电网电能质量的重要指标,对于微电网的正常运行有着重要的影响。此外,在实际用户的用电条件下,很容易因用户的用电分配不均或外界引起的各种故障导致负荷侧三相电压不平衡情况。目前,电网和负载平衡下的逆变器控制已经有了较为成熟的方法。比如离网运行时的恒压恒频Vf控制方法,还有并网时的恒功率PQ控制方法,此外还有下垂控制方法等。这些方法都是在三相电压平衡的基础上通过比例积分或者比例谐振等跟踪调节方式进行稳定控制调节。然而,当电压发生三相不平衡的情况时,相对于三相平衡条件,会出现电压的负序分量。目前的控制方法大都是建立在三相电压对称即只存在电压正序而不存在负序分量的基础上。如果存在电压不平衡的情况而仍然采用只控制正序分量的方法,会导致输出电压和电流的畸变、谐波增大等问题,无论对负载还是逆变器都会有很大的影响。所以需要将不平衡电压条件下的正序和负序电压分量分离并提取出来分别进行控制。其中使用的方法有滤波分离法、对称分量法和延迟信号方法等。此外,对于并网系统,还要考虑并网锁相环的设计,由于负序分量的存在,如果采用常规的正序分量的锁相环难免会出现锁相失败的情况,因此,本文研究了二阶广义积分、双同步解耦锁相环的方法用以在不平衡电网条件下的锁相。基于上述的正负序分离和锁相方法,本文采用了离网电压电流正负序双环控制法和并网瞬时功率控制及负序分量抑制方法,消除电压电流畸变,减小输出谐波,保持功率稳定和效率的最大化以改善不平衡负载和电网环境对逆变器的影响。最后,结合各种带载及并网的双模式逆变器的拓扑结构,基于Matlab/Simulink分别建立了并网和独立情况下的仿真模型,并进行了电网和负载不平衡条件下逆变器运行的仿真验证。此外,本文还介绍了以DSP28335为控制核心的电路实验平台及对以上的理论和仿真进行的实验工作,仿真和实验验证了本文控制策略的正确和可行性。
[Abstract]:The two-mode inverter running in the microgrid with independent and grid-connected modes will inevitably encounter the unbalanced three-phase voltage.As an important index of power quality, three-phase voltage symmetry plays an important role in the normal operation of micro-grid.In addition, under the condition of actual users' electricity consumption, it is easy to cause unbalanced three-phase voltages on the load side because of the uneven distribution of electricity by the users or various kinds of faults caused by the outside world.At present, inverter control under power grid and load balance has been more mature.For example, the constant voltage and constant frequency VF control method, the constant power PQ control method and the droop control method are used in off-grid operation.These methods are based on the three-phase voltage balance through the proportion integral or proportional resonance tracking regulation to achieve stable control.However, when the voltage is unbalanced, the negative sequence component of the voltage will appear relative to the three-phase equilibrium condition.Most of the current control methods are based on the three-phase voltage symmetry, that is, there is only a positive voltage sequence and no negative sequence component.If the voltage is unbalanced and only the positive sequence component is controlled, the output voltage and current will be distorted and the harmonic will increase, which will have a great influence on both the load and the inverter.So it is necessary to separate and extract the positive sequence and negative sequence voltage components under unbalanced voltage and control them separately.The methods used are filter separation, symmetrical component method and delay signal method.The method of double synchronous decoupling PLL is used in the condition of unbalanced power grid.Maintain power stability and maximize efficiency to improve the impact of unbalanced load and grid environment on the inverter.Finally, combined with the topology of various dual-mode inverters with load and grid-connected, the grid-connected and independent simulation models are established based on Matlab/Simulink, and the simulation verification of inverter operation under the condition of power grid and load imbalance is carried out.In addition, this paper also introduces the circuit experiment platform with DSP28335 as the control core, and the experimental work of the above theory and simulation. The simulation and experiment verify the correctness and feasibility of the control strategy in this paper.
【学位授予单位】：北方工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM727

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