“…In the Copula method, the joint cumulative distribution function (CDF) of the forecasted and actual PV unit productions is written as where F ( w a , i ) is the marginal CDF of actual power of PV units; F ( w f , i ) is the marginal CDF of forecast power of PV units; and the function C (⋅) is called the Copula function. Essentially, we transform the joint CDF F ( w a ,1 … w a , i … w a , I , w f ,1 … w f , i … w f , I ) to a function of the marginal CDFs F ( w a ,1 ) … F ( w a , i ) … F ( w a , I ), F ( w f ,1 ) … F ( w f , i ) … F ( w f , I ) linked by the Copula function C (⋅) . Similarly, the joint probability density function (PDF) is …”