DC microgrids provide a coordinated paradigm to facilitate the penetration of photovoltaic (PV) sources due to their direct current essence. Along with the sustained growth of PV penetration, there is an increasing demand on PV sources to participate in dc bus voltage regulating, especially in small-sized or islanded dc microgrids. This paper develops a decentralized coordination control strategy that applies V-I droop concept to cooperate multiple PV sources in a dc microgrid. The proposed method enables PV sources to regulate the dc bus voltage and share their output power in an expected proportion. Furthermore, the maximum power point tracking (MPPT) function is unified in the suggested control method with a dp/dv regulator, which means multiple PV sources can work in the MPPT mode when they are grid-connected or shift with load demands in an coordinated way while keeping the dc bus voltage without switching the control configuration. Hardware-in-loop tests for different scenarios are conducted to validate the feasibility and effectiveness of the proposed control strategy.

Direct current (dc) microgrids are highly compatible with photovoltaic (PV) sources due to their dc nature. However, as PV penetration increases, conventional current-source control configurations tracking the maximum power point may encounter the overvoltage problem, among others. This paper presents a V- dp/dv droop control strategy, which enables the PV sources to work in the maximum power point tracking (MPPT) mode, as well as behave as voltage sources to participate in dc-bus voltage regulating. The V-dp/dv droop method unifies MPPT and dc-bus voltage regulating in the sense of using the same control configuration, which avoids the controller reconfiguration during the PV mode switching. Further, the coordinated operation of multiple PV sources in the dc microgrid, including autonomous mode switching and primarily power sharing, is achieved by the proposed control strategy without any communication. Hardware-in-loop tests are presented to demonstrate the effectiveness of the proposed control scheme.

In the last several years, the coordination control of hybrid AC/DC microgrids (HMGs) has been gaining increasingly more attention. However, most of these discussions are focused on single-bus HMGs whose AC or DC bus is not sectionalized by AC or DC breakers. Compared with these single-bus HMGs, the bus-sectionalized HMG has more flexible topologies, more diverse operation modes, and consequently higher service reliability. However, meanwhile, these benefits also bring challenges to the stable operation of bus-sectionalized HMGs, particularly for mode switching. Relying on the national HMG demonstrative project in Shaoxing, China, this paper makes efforts to present the hierarchical control paradigm of a typical bus-sectionalized HMG toward standardization. The test results demonstrate that the proposed system provides seamless switching and uninterrupted power supply without controller reconfiguration among different operation modes. The operational data are also brought forth and analyzed to provide significant and useful experiences for designing and developing similar HMGs in the future.

The large-scale integration of Photovoltaic (PV) sources may reduce system inertia and power quality, resulting in increased frequency fluctuations and diminished system stability due to lack of the primary frequency regulation (FR) capability. To address these challenges, this paper proposes a unified strategy for frequency regulating and Maximum Power Point Tracking (MPPT) for PV sources to provide ancillary services to the power grid. The strategy employs a specifically designed active power control (APC) method to enable rapid and flexible power adjustments of PV sources, with which further FR function may be achieved. The presented APC algorithm adopts an iterative technique with a novel three-parameter PV characteristic curve, making it possible to reconstruct the real-time PV generation model, clarify the relationship between the system frequency, output power, and operating voltage. Its high control accuracy, fast convergence rate, and strong explainability offer significant practical value. Additionally, this adaptive control strategy features autonomous switch between the FR and MPPT modes adapting to real-time irradiation changes, without the need for additional irradiation or temperature sensors. The integration enhances both solar utilization efficiency and the FR capability, while eliminating the controller transitions during operating mode switches. Hardware-in-the-loop tests validate the feasibility and effectiveness of the proposed strategy.

Recently, distributed cooperative control has been popularly used in the secondary control of microgrids due to its reliability and flexibility. However, traditional distributed control schemes based on fixed‐cycle communication usually result in a waste of communication resources. Thus, this paper proposes an event‐triggered distributed control strategy that can significantly reduce the requirements of communication. In addition, compared with existing schemes, the proposed algorithm can achieve the secondary control goal in a directed graph, which can be applied to more scenarios, especially for weaker communication conditions. The stability of the strategy is investigated with the Lyapunov method. The simulation results verify the validity and effectiveness of the proposed scheme.

DC microgrids are highly compatible with photovoltaic (PV) generation because of their direct-current properties. However, with the increasing integration of PV sources into DC microgrids, traditional maximum power point tracking (MPPT) algorithms may cause problems such as overvoltage and power fluctuation, which makes it challenging to keep the stability of the DC-bus voltage due to the intermittent and stochastic nature of PVs. Consequently, in order to reduce the investment and maintenance costs of storage systems, innovative control methods are required for PVs to provide DC-bus voltage regulation services. In this paper, a novel active power control (APC) strategy, based on characteristic curve fitting, is proposed to flexibly regulate the PV output power. The transient process performance and robustness of the system are improved with the proposed APC strategy. Based on it, a V-P droop mechanism is designed to provide voltage regulating (DVR) service for the DC microgrid. The overall control strategy unifies the DVR function with the traditional MPPT function in the same control structure; thus, the PV source either works in the MPPT mode if the DC-bus is at its nominal value, or it works in the DVR mode if the DC-bus exceeds it. Switching between MPPT and DVR is autonomous, and it is fully decentralized, which improves the PV generation efficiency as well as ensures generation fairness among different parallel PV sources. Case studies including a real-world project analysis are carried out to validate the feasibility and effectiveness of the proposed strategy.