In a two-stage photovoltaic (PV) system, batteries are generally connected to the DC-link via a converter for buffering the power imbalance induced by the grid supportive services of grid-side inverter and the maximum power point tracking (MPPT) of PV source. Considering the limited battery capacity, the MPPT operation is easily compromised to avoid over-energizing the batteries in the conventional virtual synchronous generator (VSG) control, degrading the energy efficiency and extending the payback period. To concurrently achieve grid supporting and maximum PV power harvesting without increasing batteries, a coordinated VSG control for the photovoltaic/battery (PV/Bat) system is proposed in this paper. In the proposed strategy, the DC-link voltage level is segmented to differentiate the operations of converters. When the DC-link voltage is within the safety margin, the PV source operates at MPPT mode and the inverter output frequency is programmed proportionally to the DC-link voltage deviation. Meanwhile, droop control is implemented to associate the battery power with the DC-link voltage. When the DC-link voltage goes beyond the safety margin, PV de-loading and inverter rectification will be adaptively activated to restore DC-link voltage within the predefined range. The effectiveness and advantages of the proposed strategy are eventually verified by simulations and experiments.

中文翻译：

---

光伏/电池系统VSG协调控制，实现最大功率输出和电网支持


在两级光伏（PV）系统中，电池通常通过转换器连接到直流母线，以缓冲电网侧逆变器的电网支持服务和光伏最大功率点跟踪（MPPT）引起的功率不平衡来源。考虑到电池容量有限，MPPT运行很容易受到影响，以避免传统虚拟同步发电机（VSG）控制中的电池过度供电，从而降低能源效率并延长投资回收期。为了在不增加电池的情况下同时实现电网支持和最大程度的光伏发电收获，本文提出了一种光伏/电池（PV/Bat）系统的协调VSG控制。在所提出的策略中，直流母线电压水平被分段以区分转换器的操作。当直流母线电压在安全裕度范围内时，光伏电源在 MPPT 模式下运行，并且逆变器输出频率按照与直流母线电压偏差成比例的方式进行编程。同时，实施下垂控制以将电池功率与直流母线电压相关联。当直流母线电压超出安全裕度时，光伏减载和逆变器整流将自适应启动，将直流母线电压恢复到预定范围内。最终通过仿真和实验验证了所提出策略的有效性和优势。