Constant voltage method

Constant voltage method

Constant voltage method is a type of MPPT algorithm.[1] This method makes use of the fact that the ratio of maximum power point voltage and the open circuit voltage is 0.76.[2] It is the simplest MPPT control method.[3]

Algorithm

The operating point of the PV array is kept near the MPP by regulating the array voltage and matching it to a fixed reference voltage Vref. The Vref value is set equal to the maximum power point voltage of the characteristic PV module or to another calculated best fixed voltage. One of the approximations of this method is that, variations encountered by individual panels need not be considered as the constant reference voltage can be considered as the maximum power point voltage. The data for this method varies with geographical location and has to be processed differently for different geographical locations. The CV method does not require any input. It is important to observe that when the PV panel is in low insolation conditions, the CV technique is more effective than either the P&O method or the IC method (analyzed below) [13]. Thanks to this characteristic, CV is sometime combined together with other MPPT techniques.[3]

Drawbacks

  • The current from the photovoltaic array must be set to zero momentarily to measure the open circuit voltage and then afterwards set to 76% of the measured voltage.[2]
  • Energy is wasted during the time the current is set to zero.[2]
  • The approximation setting the voltage to 76% of the measured voltage is not accurate.[2]

References


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