Failure detection‐less approach for wide sustained operation of MPPT based stand‐alone solar photovoltaic system during failure/disconnection of battery

Batteries play an important role in stand‐alone two‐stage converter (boost converter and inverter) based solar photovoltaic (SPV) systems. Here, the maximum power point tracking (MPPT) operation of a stand‐alone solar system is carried out with the usage of a battery by absorbing excess solar power. Nevertheless, instability (abnormal rise of DC link voltage) can appear during the real‐time operation of the battery‐based solar energy conversion system due to the action of the MPPT controller, if a sudden battery breakdown happens. In this respect, a failure detection‐less solution is proposed. The suggested strategy restricts operation of the MPPT and helps to settle the output power of the SPV at non‐maximum level on its P‐V curve as per necessity. Thus, voltage instability at DC bus (link between boost converter and three‐phase voltage source inverter [VSI]) is prevented. Here, the bus voltage can be kept within a predefined upper and lower limit. The limits are decided accordingly to the SPV characteristics. Simultaneously, the required load powers (both active and reactive portions) are supported by the VSI. In the proposed strategy, the output of the MPPT algorithm is restricted by adopting a saturation limit for a certain duty ratio. The critical task is to find the value of the saturation limit, as the limit supports all‐time operations (it allows desired performances under all maximum power situations and avoids instability under all non‐maximum operating conditions). The procedure of determining the limit is thoroughly described. The conventional approach uses a failure detection‐based separate control algorithm. At the same time, the proposed concept does not require a separate algorithm. The suggested concept is validated via a MATLAB‐SIMULINK‐based simulation study and down‐scaled experimental set up. Instability appears in the operation of two‐stage (DC‐DC and DC‐AC) converter based stand‐alone solar photovoltaic (SPV) system due to outage of battery when duty ratio of boost converter is controlled by maximum power point tracking (MPPT) algorithm. In this article, failure detection‐less strategy of battery is proposed for restricting operating point below than peak power even under running condition of MPPT algorithm by adopting saturation limit at its output. Thus, instability at DC link point between boost converter and three‐phase voltage source inverter (VSI) is prevented and the bus voltage can be kept within predefined upper and lower li