柔性直流电网基于交流母线分列运行策略的功率盈余控制方法

Power Surplus Control Method Based on AC Bus Parallel Operation Strategy in VSC-Based DC Grid

直流电网具有低惯性弱阻尼的特点,各种扰动引发的功率盈余问题发展迅速,可能导致电网崩溃。首先分析了通过交流母线并列转分列运行时解决功率盈余问题的机理:对于送端站单极闭锁故障,交流母线分列运行可以避免故障极承载的功率被健全极转带,保护健全极换流器;对于受端站单极闭锁故障,母线分列运行的条件下可以闭锁送端站对应极换流器,消除盈余功率。将该方案与直流耗能装置进行对比,比较了两者的优势和不足,提出了减小故障后电压波动的可行策略。在PSCAD/EMTDC仿真环境中建立了4端柔性直流电网模型,通过软件仿真的方式验证了解决方案的可行性。

DC power grid has the characteristics of low inertia and weak damping,and power surplus caused by disturbance may develop quickly and lead to the breakdown of the power system.Firstly,the mechanism of solving power surplus in voltage source converter(VSC)-based DC grid by AC bus independent operation changing from parallel operation is analyzed.When sending-end station monopolar blocks,AC bus independent operation can prevent the normal polar from loading power initially loaded by faulty polar,thus protecting the normal polar.When receiving-end station monopolar blocks,corresponding polar in normal station can be blocked to eliminate power surplus.DC energy consumption device and this scheme are contrasted and their advantages and disadvantages are analyzed.Strategies to reduce voltage vibrating are proposed.PSCAD simulation of a four-terminal VSC-based DC grid model is performed,which verifies the correctness of the theoretic analysis.