基于直流微网虚拟电容控制的等效电容计算方法

Equivalent Capacitance Calculation Method Based on Virtual Capacitance Control of DC Microgrid

相较于交流电网,直流微网结构简单、效率高,且能够更好地消纳光伏、风电等分布式新能源,但其几乎不具有惯性。通过对端口换流器施加虚拟电容控制策略,使其可模拟电容充放电特性,能够改善直流电压质量,增强直流微网稳定性。但该控制方法对系统惯性提升机理暂不明确,虚拟电容控制策略所虚拟出电容值大小等问题也有待进一步探究。据此,类比于交流电网在负荷突变瞬间发电机按照惯性大小分担负荷的特性,提出直流微网中各端功率调节初期按照端口电容值比例进行分配,并在此基础上提出基于虚拟电容控制策略的等效电容计算方法,探究虚拟电容与等效电容间的对应关系。最后,搭建了控制器级的硬件在环测试平台,验证了虚拟电容控制策略的有效性、直流微网功率调节分配依据及所提等效电容计算方法的正确性。

Compared with AC power grid,DC microgrid not only has simple structure and high efficiency,but also can better absorb distributed new energy such as photovoltaic and wind power generation,while it has almost no inertia.The port converter can simulate the charging and discharging characteristics of capacitors when the virtual capacitor control is applied,which can improve the quality of DC voltage and enhance the stability of DC microgrid.However,the mechanism of inertia enhancement under virtual capacitance control is not clear.The problem that how much capacitance can be produced by virtual capacitor control remains to be further explored.Accordingly,analogous to the variation of load sharing by generators in AC microgrid according to inertia,the power regulation at each side of DC micro grid in the initial stage is allocated according to the proportion of capacitance value.And on this basis,the equivalent capacitance calculation method based on virtual capacitance control is proposed to explore the corresponding relationship between virtual capacitor and equivalent capacitor.Finally,the hardware-in-loop test platform in controller level is established to verify the effectiveness of virtual capacitance control,the correctness of the basis for power regulation allocation in DC micro grid and the corresponding relationship between virtual capacitance and equivalent capacitance.