分体式储能VSG功率转换系统输出电压鲁棒控制器设计

Output Voltage Robust Controller Design for the Power Converter System in the Assembled VSG

分体式储能虚拟同步发电机(virtualsynchronous generator,VSG)的前、后级子系统级联稳定对其可靠实现调频、调压等辅助服务功能至关重要。为了确保储能接口变换器与控制参数未知的VSG在整个工作条件范围内均级联稳定,提出了前级变换器输出电压鲁棒PI控制器参数设计方法:首先,求取前级变换器带理想电流源型负载时的输出电压PI参数稳定区;然后,将后级VSG视为恒功率负载,计算其最大负载条件下的VSG闭环输入阻抗(即为负电阻R_(eq))和最小负载情况下的前级变换器闭环输出阻抗Z_(oc)(s),得出满足阻抗约束关系|Z_(oc)(s)|<|R_(eq)|的输出电压PI参数区域;其与前述稳定区的交叠区域即为级联鲁棒稳定区。该设计方法的正确性通过10kVA的仿真模型得到了验证。

The interactive stability of the front-end dc-dc converter and the rear-end virtual synchronous generator(VSG) is critical for the assembled energy storage VSG to reliably supply the auxiliary services such as frequency regulation, voltage regulation, and so on. In order to ensure that the energy storage interface converter operates stably throughout the entire working conditions when connected with the VSG with unknown control parameters, this paper proposes a design of the output voltage robust PI controller parameters for the front-end converter. There are three steps in this design.Step 1: The stable region of the output voltage PI parameters is calculated when the front-end converter has an ideal current source load. Step 2: Regarding the VSG as a constant power load, the closed-loop input impedance of the VSG(i.e. negative resistance, R_(eq)) under the maximum load and the closed-loop output impedance of the front-end converter Z_(oc)(s) under the minimum load are determined. Step 3: the output voltage PI parameter region is obtained which satisfies the impedance constraint(|Z_(oc)(s)|<|R_(eq)|). The parameters in the overlap part of these two stable regions can ensure the robust cascade stability.The correctness of the design is verified with a 10 kVA simulation model.