A control strategy for 
distributed power generation modules in a power 
system that varies the line frequency or 
voltage according to a predetermined pattern to cause a PV 
inverter to modify its 
power output and thereby avoid overcharging a battery. When the power 
system operates in islanded mode, the AC load demand can be lower than the available energy from the PV array, causing the battery to become overcharged. To avoid this 
scenario, a 
hybrid inverter executes a pattern generator 
algorithm that varies the line frequency or 
voltage linearly, exponentially or any mathematical function or look-up tables. The PV 
inverter executes a 
pattern detection algorithm that detects the linear, exponential, or any mathematical function or look-up table change in the line frequency. In response, the PV inverter modifies its 
power output until an overcharging condition of the battery is removed. The line frequency / 
voltage can be varied within the anti-
islanding limits to avoid premature disruption of the power 
system, and no additional settings are required at the device level in order to operate in any mode of operation: islanded, grid-connected or genset-connected.