Regulation is one of the ancillary services that hydropower plants can supply in addition to power to increase the reliability and flexibility of the power system to adjust to fluctuations in power demand and supply. When a plant is regulating it will follow the load within some prescribed band of power rather than generating a fixed amount of power. Typically, regulation is a valuable service that can be provided efficiently by hydropower compared to alternative power sources. In locations where regulation is marketed it usually commands a solid premium above the price of the power generated. This value is partially reduced by the increased maintenance costs associated with regulation.

There are three methods in this category: One Sided Regulation, Two sided Regulation and One and Two Sided Regulation. The design of one sided regulation is almost identical to two sided regulation except that there are separate calculations for regulation up and regulation down. The One and Two Sided Regulation method will allow the user to use both approaches within a single model.

Regulation services are not evaluated.

Regulation services are valued as a piecewise linear function of the amount of regulation provided minus the additional operating costs (wear and tear, maintenance, and so on) associated with regulation. The piecewise linear valuation is analogous to the block hydro method of valuing generation (see Preferred Customer for details). All of the associated slots for this method have a compatible slot in the block hydro method. The operating costs are simply the sum of individual operating costs calculated on the power reservoirs that are providing regulation.

Two sided regulation assumes that frequency regulation is scheduled with an equal amount of regulation up and regulation down available, and a single valuation for this ancillary service. In contrast, one sided regulation allows regulation up and regulation down to be separate ancillary services with separate amounts scheduled and usually valued differently.

The System Regulation slot holds the total two sided regulation for all power reservoirs linked to it. The value of marginal value of regulation is a non-increasing function of the amount of regulation. In RiverWare, this function is modeled as a series of discrete blocks with decreasing (or equal) marginal values of regulation. These values are in the Regulation Block Costs slot. The amount of each block used in the valuation is in the Block Regulation slot. These blocks are used in order of most valuable to least valuable.

The Regulation Marginal Value and Previous Regulation Marginal Value slots hold the marginal value of increasing and decreasing regulation respectively. If the valuation partially uses a block, then both the Regulation Marginal Value and Previous Regulation Marginal Value slots will have the value of that block. If instead, say N blocks are fully used, and Block N+1 is unused, then Regulation Marginal Value will have the value of Block N+1 and Previous Regulation Marginal Value will have the value of Block N.

This method requires either Calculate Linear Economic Value or Calculate Block Economic Value or method to be selected. See Calculate Linear Economic Value and Calculate Block Economic Value for details.

Simulation and Optimization use the following equation to calculate the value of regulation by summing over blocks.

The energy in the regulation blocks is constrained to equal the total system regulation (converted from power to energy by multiplying by the timestep).

The value of one sided regulation is philosophically similar to two sided regulation. The only difference is that regulation up and regulation down have separate slots and separate valuations. Physically, this may lead either to solutions that use only one side of regulation or solutions that use both sides, but perhaps unevenly. For one sided regulation, there are two slots for every analogous slot in two sided regulation, an Up slot and a Down slot. Similarly, the System Regulation Up and System Regulation Down slots should be linked to Regulation Up and Regulation Down respectively on power reservoirs. For more detail on the specific calculations, see the description of two sided regulation.

This method allows the user to perform both one and two sided regulation in a single model. The slots added by this method include all of those for one sided regulation listed above and those for two sided regulation listed in the online help. This method will simply call the two sided regulation method, then call the one sided regulation method.