PV Plant Inverter Transients — Power-Frequency Surge Analysis

Power-frequency (industrial-frequency) overvoltage surges were being observed on the regional network, with Celsia's photovoltaic plants the suspected source. Rather than treat the inverters as black boxes, Gridradix modelled the control systems of the plants' DC/AC converters in MATLAB/Simulink and ran electromagnetic-transient simulations in EMTP to reproduce the surges, identify the operating conditions and control interactions that produced them, and define corrective settings — a class of overvoltage that conventional load-flow and short-circuit tools cannot see.

• Root-cause analysis of industrial-frequency surges attributed to photovoltaic power plants, using electromagnetic-transient simulation in EMTP.
• Modelling of the control systems of the plants' DC/AC converters in MATLAB/Simulink for transient analysis, including current control, phase-locked loop and anti-islanding behaviour.
• Reproduction of the observed surge events in simulation, with sensitivity studies across grid strength, irradiance and fault scenarios.
• Identification of the control and network interactions responsible for the overvoltages, and definition of mitigation measures — inverter settings and protection coordination.
• Support for the operator's power-quality compliance reporting and client-compensation review (SAIDI, SAIFI, DIU and FIU indicators).

By modelling inverter control explicitly instead of assuming ideal sources, the study explained overvoltages that steady-state tools cannot reproduce — and gave the operator concrete settings and a repeatable model for evaluating new PV connections.