随着分布式光伏发电的逐渐兴起，光伏微电网作为连接分布式能源的小型电网已经被广泛应用，作为一种新型的发电系统，光伏微电网可以使得偏远山区的供电得到解决，并且可以通过自然能源来解决电力系统能源问题。但是光伏发电系统中由于日照因素、负载因素及设备等影响，使得光伏微电网对电压、电流等电能质量问题要求较为严格，当所接入的不平衡负载时，光伏微电网输出的电压就不平衡，用户短电压也不平衡，给设备寿命造成了严重的影响；同样当接入的负载不平衡或故障发生，会使得输出的故障电流远远超出了不平衡电流值，极容易烧坏设备。PCC点电能质量差，在孤岛运行或并网运行情况时，对用户或电网造成严重影响，导致电网波动及不稳定。 根据上述情况，结合电压、电流的不稳定影响，本文提出一种结合不平衡电压和故障电流的控制方法。电压控制是通过一次控制和二次控制完成的，一次控制进行P/Q功率计算和虚拟下垂控制，P/Q功率计算将PCC点的电压电流进行功率计算，得到的功率经过下垂控制进而转换成电压和频率，下垂控制能对光伏逆变器输入、输出功率进行分配，由于一次控制中的电压和频率存在不稳定性，在二次控制中通过二次控制的标准判断进而进一步消除电压幅值和频率的偏差，使得偏差在一定的偏差范围内。故障电流控制法通过在二次控制中加入对故障电流的判断，当负载不平衡或故障时不稳定电流会远超过额定电流，如果故障电流超过额定电流的两倍，则切换到故障电流限制器进行控制，以此始终保障故障电流在额定电流的两倍范围内进行工作。 最后在MATLAB/Simulink仿真平台上搭建三个DG的仿真模型，设置其中一个DG工作在电压控制下，另外的工作在电流控制下，通过对三相平衡情况下、电压控制的三相负载不平衡情况及电压、电流控制的三相不平衡三种情况进行仿真对比。三相平衡情况下加入负载前后电压、电流的波形，证明加入负载影响了电压但电流波形影响更大，都在一定的控制范围内；在电压控制的三相负载不平衡情况中通过加入补偿前后的波形进行对比，证明所提控制方法的合理；在电压、电流控制的三相不平衡三种情况下，分别对三相对地及两相对地、两相之间故障情况进行验证，波形能很好的说明了电压电流控制法不仅对电压而且对电流有很好的控制效果。

With the gradual rise of distributed photovoltaic power generation, photovoltaic microgrid has been widely used as a small grid connecting distributed energy. As a new generation system, photovoltaic microgrid can make the power supply in remote mountainous areas be solved, and can solve the energy problem of power system through natural energy. However, due to the influence of sunshine, load and equipment in photovoltaic power generation system, photovoltaic microgrid requires more stringent power quality problems such as voltage and current. When the unbalanced load is connected, the output voltage of photovoltaic microgrid is unbalanced, and the short voltage of users is unbalanced, which has a serious impact on the life of the equipment. If the fault occurs, the output fault current will exceed the unbalanced current value, and it will burn the equipment easily. The poor power quality of PCC points has a serious impact on users or power grids, resulting in fluctuation and instability of power grids. According to the above situation, combined with the unstable influence of voltage and current, a control method combining unbalanced voltage and fault current is proposed in this paper. Voltage control is accomplished by primary control and secondary control. Primary control carries out P/Q power calculation and virtual sag control. P/Q power calculation calculates the voltage and current of PCC points. The power obtained is converted into voltage and frequency through sag control. Sag control can distribute the input and output power of photovoltaic inverters. Because of the voltage and frequency in primary control, sag control can distribute the input and output power of photovoltaic inverters. The rate is unstable. In the secondary control, the deviation of voltage amplitude and frequency is further eliminated by the standard judgement of the secondary control, so that the deviation is within a certain range of deviation. Fault current control method by adding fault current judgment in secondary control, when the load is unbalanced or when the fault occurs, the unstable current will far exceed the rated current. If the fault current exceeds twice the rated current, it will be switched to the fault current limiter to control, so as to always ensure that the fault current works within twice the rated current. Finally, three DG simulation models are built on MATLAB/Simulink simulation platform. One DG works under voltage control and the other under current control. The three-phase load imbalance under voltage control and three-phase unbalance under voltage and current control are simulated and compared. The waveforms of voltage and current before and after adding load in three-phase balancing situation prove that adding load affects voltage but current waveform has greater influence, which is within a certain control range. In the three-phase unbalanced situation of voltage control, the waveforms before and after adding compensation are compared to prove the rationality of the proposed control method; in the three-phase unbalanced situation of voltage and current control, the three-phase unbalanced situation is proved. Then, the fault of three-phase to ground, two-phase to ground and two-phase to ground are verified respectively. The waveform shows that the voltage and current control method not only has a good control effect on voltage but also on current.