Abstract
This study proposes a control scheme for high power grid-connected wind power converters, which is oriented to enhance their performance when connected to weak grids with low short circuit ratio. The proposed controller consists of an outer current reference generation loop and an inner current loop, working in stationary reference frame. In the outer loop, the current reference is calculated to comply simultaneously with the grid code requirements, the control of the DC link, and the operational safety margins of the converter during faulty conditions. On the other hand, the proposed inner current loop consists of a proportional resonant controller, a capacitor voltage feedforward and a phase shifter. Moreover, simulation results considering different weak grid conditions, as well as experimental results of a full-scale 4 MW converter test-bench are presented to validate the good performance of the proposed method.
Highlights
Nowadays, high power photovoltaic and wind generation power plants play an important role in the electric power system, covering a significant percentage of the power demand [1, 2]
Since these plants are often located in remote areas, where the grid has low short circuit ratio (SCR), the control of the power conversion systems has a significant influence on the performance of the grid at the point of common coupling (PCC), especially under fault conditions [10, 11]
Two experimental cases have been selected in this validation stage, a non-distorted scenario, where a sudden active power step of 1 MW is performed and a faulty situation consisting of severe three-phase voltage sag
Summary
High power photovoltaic and wind generation power plants play an important role in the electric power system, covering a significant percentage of the power demand [1, 2]. The use of grid feeding voltage source converters is a widespread solution for connecting high power RES-based plants to the grid, due to the good trade-off that such system offers between cost, safe-operation, controllability and dynamic behaviour [8, 9] Since these plants are often located in remote areas, where the grid has low short circuit ratio (SCR), the control of the power conversion systems has a significant influence on the performance of the grid at the point of common coupling (PCC), especially under fault conditions [10, 11]. To work in a wellreferenced scenario, the current references will be found considering the constraints of the German grid code VDE-ARN-4120, which is oriented to set the operation boundaries of gridconnected converters under grid fault conditions In this controller, the proposed inner loop is based on a proportional resonant (PR) controller combined with a voltage feedforward and a new phase shifter for tracking the current reference.
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