Voltage Support Technology for Renewable Energy Collection Stations with Synchronous Machine-like Characteristics

Abstract

To improve voltage support at the point of common coupling of renewable energy collection stations connected to weak grids, this paper proposes a synchronous machine-like outer reference generator for a conventional fixed-PQ voltage-source converter (VSC). The proposed versatile static synchronous machine (VSSM) emulates the excitation and reactive power-voltage regulation of a synchronous generator, maps the resulting transient internal electromotive force to an exact reactive power reference, and applies converter capability and ramp rate limits with an equivalent Q-tracking response. A two-stage strategy further uses fast dynamic compensation to clamp voltage and slower static compensation to release bidirectional dynamic reserve. In the WSCC nine-bus benchmark, all controllers use the same 100 MVA VSC, +/−80 Mvar limit, 0.04 s reactive power inner loop, and 10 pu/s ramp limit. After a three-phase fault and line tripping, the minimum post-fault bus 8 voltage is 0.9452 pu with the VSSM, compared with 0.8755 pu for the calibrated PI-SVG and 0.7660 pu for fixed Q; Q-U droop gives 0.9492 pu but requires 0.33 s for sustained recovery above 0.95 pu, compared with 0.23 s for the VSSM. A positive-, negative-, and zero-sequence extension also evaluates a single-line-to-ground fault. Finally, an anonymized actual receiving-end grid model shows an approximately 40 ms improvement in voltage recovery and reduced steady-state loading of dynamic reactive sources. All results are obtained from offline simulations.