Marginal generating costs of multi-block power systems with and without partial outages

Marginal pricing of electricity calls for the determination of marginal energy costs over time or equivalently at any load level. This paper extends an earlier study which calculated the expected demand-related marginal energy costs to allow units to be loaded to generation in blocks. A computationally efficient procedure is developed to compute the probability that at any specified load level a given block will be the last block loaded. This then provides a straightforward method for calculating the expected marginal energy costs over time. Both complete forced outages and partial outages of units are stochastically considered.