Adaptive Reactive Power Control of PV Power Plants for Improved Power Transfer Capability Under Ultra-Weak Grid Conditions

Abstract

This paper analyzes the power transfer limitation of the PV power plant under the ultra-weak grid condition, i.e., when the Short-Circuit Ratio (SCR) is close to 1. It explicitly identifies that a minimum SCR of 2 is required for the PV power plant to deliver the rated active power when operating with the unity power factor. Then, considering the reactive power compensation from PV inverters, the minimum SCR in respect to Power Factor (PF) is derived, and the optimized coordination of the active and reactive power is exploited. It is revealed that the power transfer capability of PV power plant under the ultra-weak grid is significantly improved with the low PF operation. An adaptive reactive power droop control is next proposed to effectively distribute the reactive power demands to the individual inverters, and meanwhile maximize the power transfer capacity of the PV power plant. Simulation results of a 200 MW PV power plant demonstrate that the proposed method can ensure the rated power transfer of PV power plant with the SCR of 1.25, provided that the PV inverters are operated with the minimal PF=0.9.

Voltage-Modulated Direct Power Control for a Weak Grid-Connected Voltage Source Inverters

“…pcc should have real value. That means the inverter has a maximum real power injecting to the weak grid, which has been discussed in [42].…”

“…To inject the rated real power to the weak grid, the reactive power should generate to compensate the voltage at the PCC [42]. Consequently, (26) is changed into relationship in (27) based on the phasor diagram, as shown in Fig.…”

Control the Voltage Instabilities of Distribution Lines using Capacitive Reactive Power

“…In the case of voltage disturbances, it is required to control the production of reactive power in the distribution lines. Several effective control algorithms have been proposed for this purpose [24][25][26][27][28]. These algorithms include Takagi-Sugeno-Kang probabilistic fuzzy neural network control [24], instantaneous active/reactive power control strategy for flicker mitigation [25], single-point reactive power control method [26], decoupled active and reactive power predictive control [27], adaptive reactive power control [28], etc.…”

Grid-Synchronization Stability Analysis for Multi DFIGs Connected in Parallel to Weak AC Grids

“…In many parts of the world, the rich wind energy resources are located far from the load centers, resulting in wind farms being integrated into a weak AC grid with a long transmission line. In particular, under some ultra-weak grid conditions, the short-circuit ratio (SCR), which is commonly used for describing grid strength, of transmission lines can even be close to 1.0 [1,2]. The connection to a weak grid significantly challenges the stable operation of wind power generation systems.…”