Unit Commitment. We authorize you, acting as our agent and on our behalf, to receive in exchange for the Underlying Debt Obligations or the Underlying Securities, as defined in Section 3, the Units representing a fractional undivided interest in the Trust up to the number of Units which we have advised you by telegraph, telegram or other form of facsimile transmission substantially in the form of Schedule B hereto that we agree to purchase (the "Acceptance"). We understand that the Acceptance must be received by you by the close of business on the day preceding the Date of Deposit (as defined in the Indenture). We further agree that the Underwriters to be subject to this Agreement for the Trust shall be those who have given Acceptances and are named in the Prospectus. We hereby authorize you to cause the Registration Statement as first filed with the Securities and Exchange Commission in accordance with Paragraph 1 hereof (the "Registration Statement") to be amended to include in the Prospectus the amount of Units of the Trust which we have agreed to underwrite (our "Unit Commitment"). We agree that notwithstanding our failure to send the Acceptance to you in the manner set forth in this paragraph, our acceptance of delivery of the Units subsequent to the Date of Deposit shall be deemed to be an Acceptance in accordance with the provisions hereof. The number of Units of each Trust to be underwritten hereunder is unlimited and it is understood that you may increase the number of Units specified in the Registration Statement, or you may decrease the number of Units, if you shall deem it advisable and practicable to do so. You may permit any Underwriter to increase its Unit Commitment (by written agreement) or additional underwriters to become parties to this Agreement (the addition of new parties hereto to be evidenced in each case by an agreement substantially in the form of this Agreement to be entered into between you and any such new party). You may decrease our Unit Commitment by any amount, including to zero, by notifying us by telephone, such notice to be confirmed in writing. Apart from the authorized decrease provided for in this Paragraph, the number of Units to be underwritten by each of us shall not be changed from the amount set forth in our Acceptance without our written consent.
Unit Commitment. The technological constraints of this socio-technical model arise in the unit- commitment problem. Traditionally, unit commitment models are used to determine a short-term (weekly) power generation schedule. While they have also been used to estimate annual production costs, the deterministic nature of the original models (e.g. Bertsekas et al. (1983)) do not lend themselves to mid- and long-term analysis. More recently, these models have been extended to accommodate uncertainty in load forecasts, fuel prices, etc. (Takriti, Birge, and Long (1996), Takriti, Krasenbrink, and Wu (2000), and Nowak and Romisch (2000)). Recent advances in unit commitment models are summarized in the edited volume by Hobbs et al (2001). The models mentioned above are typically focused on a short-term scheduling issue (a week or two at most). Due to the medium-term nature (i.e., one year) of many financial instruments, it is difficult to measure their impact using short-term models. Our multi-granularity approach integrates the unit- commitment model with financial decision-making by including the forwards and spot market activity within the scheduling decision model.
Unit Commitment. The 3rd Revised Straw Proposal includes a number of references to the ability of an EIM Entity to elect whether or not to participate in the ISO’s unit commitment process. The ISO makes it clear that if the EIM Entity elects to have the EIM commit generators in the real-time market, then the transfer will include bid cost recovery payment costs for both energy above minimum load and commitment costs. In section 3.4.3, the ISO also states that if the EIM Entity elects to allow unit commitment in RTUC, then all resources with economic bids that are available for the 15-minute RTUC commitment (online or offline) will be eligible to ensure sufficient ramping capability. In commenting on drafts of the ISO’s proposals on unit commitment, a number of parties raised concerns related to the ability of EIM Entities to choose whether or not to participate in unit commitment and the allocation of commitment costs. Upon review, and in order to resolve this key issue, PacifiCorp has decided that it will elect to have EIM Participating Resources within PacifiCorp’s BAAs included in the ISO’s unit commitment process. This decision is primarily based on the conclusion that this approach should provide the most efficient utilization of resources, especially with respect to management of flexible ramping needs across the EIM footprint. In addition, PacifiCorp is hopeful that resolution of this critical issue will narrow the list of remaining issues and may relieve some parties’ concerns with respect to the ISO’s stakeholder timelines. This decision also contributes to the resolution of other issues potentially created by allowing EIM Entities to elect whether or not to participate in unit commitment. For instance, in section 126.96.36.199 of the 3rd Revised Straw Proposal, the ISO indicates that it will combine the energy and commitment components after considering BAA transfers in to a single real-time bid cost recovery allocation amount and will allocate this amount to measured demand. Further, this section states that the two components for an EIM Entity BAA will be allocated to the EIM Entity Scheduling Coordinator and then allocated by the EIM Entity according to its tariff. If the EIM Participating Resources in all EIM BAAs are required to participate in unit commitment, the separation of the energy and commitment components, which PacifiCorp understands is a relatively difficult process, would be unnecessary. Additionally, PacifiCorp understands that only units that are ide...
Unit Commitment. PacifiCorp continues to evaluate whether it is appropriate for all EIM Entities to participate in the unit commitment of resources in the 15-minute Real Time Unit Commitment market. Although this requirement may eliminate an important seams issue, the costs and benefits associated with an EIM Entity’s participation in unit commitment are not yet clear, and require further assessment and evaluation. PacifiCorp will continue to evaluate and provide further comment on this issue, as necessary, in response to future revisions of the straw proposal. In any event, costs associated with unit commitment in the ISO or another EIM Entity should be limited to transfers into the EIM Entity paying the costs.
Unit Commitment. Unit Commitment optimization is the determination of the activation of power plants, in order to meet a certain demand for electricity at lowest cost. Economic dispatch on the other hand is defining how activated plants are dispatched in the cheapest way. The UC is a difficult problem to solve6, yet in the literature, a lot of possible strategies are described in order to solve this issue. Amongst the most well described methods, we find priority listing, Lagrange relaxation, dynamic programming, mixed integer programming, genetic algorithms etc. An overview of UC optimization methods is presented in . In this work, a Mixed Integer Linear Programming (MILP) model is developed. This model, which will be described further, solves both the UC as well as the economic dispatch problem in a single optimization.
Unit Commitment. Assessing these benefits requires a model that adequately represents the operational constraints of the system (such as the need to follow the load profile while maintaining enough spinning reserve) as well as the operating limits of the generating units (e.g. ramp rate and minimum up- and down- time). Unit Commitment (UC) programs are typically used to enforce these constraints but such programs consider only the cost of running the generating units over an optimization horizon ranging from a day to a week. Several extensions are required to transform such a UC program into a tool capable of balancing the long- and short-term costs of providing flexibility:• The objective function must include not only the operating cost but also the amortized investment cost of each generating unit• The optimization must be able to decide not only when a particular generating unit is started–up and shutdown, but also whether building that unit is optimal or not• The optimization horizon must be extended because the need for flexibility varies with the seasonal variations in load level, load profile and renewable generation.
Unit Commitment. There are two major options for scheduling in a day-ahead market: Self-Commitment or Centralized Unit Commitment. With Self-Commitment, generators are responsible for their own commitment, i.e., the decision of which generating units will run the next day. By contrast, with centralized Unit Commitment, these decisions are taken optimally by the TSO for all generating units based on their cost/bid information and their technical characteristics. The greatest disadvantage of self-commitment is its inconsistency with the must-offer obligation. Must-offer obligations have been increasingly used in the U.S. after the California energy crisis. A resource that is subject to the must-offer obligation must bid in every hour when it is available. Its only mechanism to incorporate technical constraints and internalize start-up and no-load costs is through the offer prices. The bidding process provides bidders the needed flexibility to internalize their constraints in their offers. Extreme offer prices, however, are problematic. High offer prices may interfere with market power mitigation mechanisms and market monitoring activities. Low offer prices, on the other hand, may interfere with regulatory limitations to protect against predatory pricing. Many market designs prohibit bids below the relevant variable cost. Self-commitment does not appear to be a viable option for the day- ahead market with must-offer obligations, as it would create large imbalances, considerable burden for operators during the balancing process, and great risk to generators, which could become a barrier for entry.In some markets that use self-commitment (e.g. ERCOT), the scheduling-feasibility risk is mitigated by allowing portfolio bidding. With portfolio bidding, generators submit aggregate offers for the portfolio of their generating units, and then specify the unit-specific schedules that comprise the accepted portfolio offer after the latter clears the day-ahead market. Portfolio bidding, however, is clearly not a good choice in market with one or two dominant players since it would give them a tremendous competitive edge compared to new entrants. Furthermore, experience in ERCOT shows that lack of unit-specific offers results in inefficient resource use and in cumbersome settlement procedures.In centralized markets, unit commitments selected by the TSO to ensure adequate reserve capacity can occasionally have severe effects on energy prices. The standard procedure is to select units acco...
Unit Commitment. Unit Commitment Problem (UCP) is solved to determine which generating units must be on and which should be off before optimization problem determines the level of generation by each unit. This problem takes a new twist when electricity is traded at power exchange and a possible solution is suggested in . If a generating unit is committed to run in a certain interval of time as a solution of UCP then it can not be shut down. In such a case, the generator must operate at or above its minimum capacity even if its operation is uneconomical. Such decisions are due to a variety of constraints imposed on generators and power system as a whole. There is a minimum spinning reserve that has to be maintained in view of system stability and reliability . Moreover, thermal unit constraints limit minimum up and down times to allow gradual temperature changes in generators .