Adaptive-MPPT-Based Control of Improved Photovoltaic Virtual Synchronous Generators

Abstract

The lack of inertia and damping mechanism of photovoltaic (PV) grid-connected systems controlled by maximum power point tracking (MPPT) poses a challenge for the safety and stability of the grid. Virtual synchronous generator (VSG) technology has attracted wide attention, since it can make PV grid-connected inverter present the external characteristics of a synchronous generator (SG). Nevertheless, traditional PV-VSG is generally equipped with an energy storage device, which leads to many problems, such as increased costs, space occupation, and post-maintenance. Thus, this paper proposes a two-stage improved PV-VSG control method based on an adaptive-MPPT algorithm. When PV power is adequate, the adaptive-MPPT allows the PV to change the operating point within a stable operation area to actualize system supply-demand, matching in accordance to the load or dispatching power demand; when PV power is insufficient, PV achieves traditional MPPT control to reduce power shortage; simultaneously, improved VSG control prevents the DC bus voltage from falling continuously to ensure its stability. The proposed control approach enables the two-stage PV-VSG to supply power to loads or connect to the grid without adding additional energy storage devices, the effectiveness of which in off-grid and grid-connected modes is demonstrated by typical simulation conditions.

Modeling and Mechanism Investigation of Inertia and Damping Issues for Grid-Tied PV Generation Systems with Droop Control

“…With the increase of K i , the oscillation period of P e changes significantly. While the oscillation amplitude and the attenuation speed of P e change little, Energies 2019, 12,1985 15 of 17 indicating that the system synchronization effect is enhanced. At the same time, it can be seen that with the enhancement of the system synchronization capability, U dc and P e change more obviously.…”

“…Reference [11] used virtual synchronous generator (VSG) technology to simulate the characteristics of traditional synchronous machines and improve the standby rotational inertia of the GPVGS. References [12,13] proposed a reactive standby PV-VSG strategy for variable step power tracking to provide inertia and damping support for the PV system. References [11][12][13] only made the system have certain inertia and damping characteristics from the perspective of the control method, and did not analyze the inertia and damping mechanism affecting the system from the physical mechanism level.…”

“…References [12,13] proposed a reactive standby PV-VSG strategy for variable step power tracking to provide inertia and damping support for the PV system. References [11][12][13] only made the system have certain inertia and damping characteristics from the perspective of the control method, and did not analyze the inertia and damping mechanism affecting the system from the physical mechanism level. In [14], the electric torque analysis method is used to analyze the inertia and damping characteristics of the grid-tied inverter itself, but the influence of the primary side energy was not considered.…”

“…References [15,16] combined with energy storage devices to analyze the effects of two different control strategies on the inertia and damping characteristics of grid-tied energy storage systems. Based on [11][12][13][14][15][16], we want to obtain a similar inertia expression (1) for PV systems compared to conventional synchronous generator:…”

Virtual Inertia-Based Control Strategy of Two-Stage Photovoltaic Inverters for Frequency Support in Islanded Micro-Grid

“…A voltage PI controller is employed in the literature [26] for an enhanced dynamic response; however, the power set point tracking performance is degraded. Furthermore, many methods have been developed for the PV's available power estimation [27][28][29][30], and most are realized through irradiance/temperature sensors and the PV array polynomial model; although they suffer from the deviation of the MPP under various changes in environmental conditions and a low estimation speed, this method has been widely used in reality because of its simplicity and practicality.…”