Why anti-islanding testing is demanding
The anti-islanding tests in IEEE 1547, IEC 62116 and GB/T 30427 require an RLC resonant circuit with quality factor Qf around 1 on the inverter output, tuned so that both active and reactive power match the inverter output exactly, before the grid is opened and the trip time measured. If the match is not precise, the inverter trips quickly on an obvious voltage or frequency excursion and the genuine worst case is never reached.
The LANDI anti-islanding platform provides finely stepped adjustable R, L and C banks with an automatic tuning routine, so the worst-case balance point can be searched point by point as the standard requires, with the interval from grid opening to shutdown logged automatically.
Weak-grid capability
Large PV and storage plants often connect at the weak end of a network with a low short-circuit ratio. At low SCR the inverter control loop interacts with grid impedance and can produce sub-synchronous oscillation or outright instability. A weak-grid fixture inserts adjustable reactance to lower the effective SCR so these problems appear during factory testing rather than after energisation.
Cycling and efficiency
Round-trip efficiency and capacity fade need long charge-discharge cycles to establish. The test system must hold a defined power profile for hours or days while logging DC-side and AC-side voltage, current, power and temperature together, so the loss in each stage can be separated.