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This paper presents a single-phase photovoltaic (PV) system integrating segmented energy storages (SES) using cascaded multilevel inverter. The system is designed to coordinate power allocation among PV, SES, and utility grid, mitigate the overvoltage at the point of common coupling (PCC), and achieve wide range reactive power compensation. The power allocation principle between PV and SES is described by a vector diagram. Accordingly, a sophisticated power allocation strategy is developed to allocate power between PV and SES based on a novel discrete Fourier transform (DFT) phase-locked loop (PLL) method. An appropriate reactive power allocation coefficient (RPAC) is designed to avoid duty cycle saturation and overmodulation so that wide range reactive power compensation and good power quality can be achieved simultaneously. The self-regulating power allocation control system integrating the preferred RPAC and an advanced active power control algorithm is developed to achieve the aforesaid objective. A 3.5-kW single-phase grid-connected cascaded PV system was built and tested at 1.6 kW in the laboratory. Simulation and experimental results are provided to demonstrate the effectiveness of the proposed cascaded PV system integrating SES.Index Terms-Cascaded photovoltaic (PV) system, power allocation, reactive power compensation, segmented energy storages.

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This paper proposes an autonomous unified var controller to address the system voltage issues and unintentional islanding problems associated with distributed Photovoltaic (PV) generation systems. The proposed controller features integration of both voltage regulation (VR) and islanding detection (ID) functions in a PV inverter based on reactive power control. Compared with the individual VR or ID methods, the function integration exhibits several advantages in high PV penetration applications: 1) fast voltage regulation due to the autonomous control; 2) enhanced system reliability because of the capability to distinguish between temporary grid disturbances and islanding events; 3) negligible non-detection zone (NDZ) and no adverse impact on system power quality for ID and 4) no interferences among multiple PV systems during ID. As the VR and ID functions are integrated in one controller, the controller is designed to fulfill the requirement of VR dynamic performance and ensure small ID NDZ simultaneously. The interaction among multiple PV systems during VR is also considered in the design procedure. Finally, the feasibility of the proposed controller and the controller design method is validated with simulation using a real time digital simulator (RTDS) and a power hardware-in-the-loop (PHIL) testbed.

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A novel artificial cobweb routing algorithm (ACRA) for routing the tree-type physical topology of a low-voltage distribution network in a smart grid is proposed and analyzed in this paper. The establishment, maintenance and reconstruction of the route are presented. The artificial cobweb routing algorithm is shown to have broad general applicability for power line communication. To provide a theoretical foundation for further research, the communication delay of the network is calculated accurately. Simulation analysis of the communication delay and throughputs, which were based on Opnet14.5, demonstrate the accuracy of the theoretical calculation. For the performance evaluation of ACRA, a test-bed that includes PLC nodes with the ACRA is set up in a noisy environment. Experimental results show the feasibility of the ACRA algorithm. These indicate that ACRA is effective for guaranteeing Quality of Service (QoS) and reliability in power line communication.