Wind Power Providing Flexible Ramp Product

Abstract

Abstract-The deepening penetration of renewables in power systems has contributed to the increasing needs for generation scheduling flexibility. Specifically, for short-term operations, flexibility here indicates that sufficient ramp capacities should be reserved to respond to the expected changes in the load and intermittent generation, also covering a certain amount of their uncertainty. To address the growing requirements for flexible ramp capacity, markets for ramp products have been launched in practice such as the ones in California ISO and Midcontinent ISO. Sometimes, to guarantee sufficient ramp capacity, expensive fast-start units have to be committed in real-time. Moreover, with higher penetration of renewable generation, the flexibility provided by the conventional units might not be enough. Actually, wind power producers are physically capable of offering flexibility, which is sometimes also economically efficient to the entire system. In this paper, we aim to explore the mechanism and possibility of including wind power producers as ramp providers to increase the supply of flexibility. To conduct the analyses, a two-stage stochastic real-time unit commitment model considering ramp capacity adequacy is formulated. Case studies indicate that both the system and the wind power producers can benefit if the wind power is allowed to provide flexible ramp products.Index Minimum system upward and downward regulation reserve requirements. Ramping rate limit of a unit. Ramping rate limit of a WPP. s, SIndex and set of scenarios. SDRRMaximum shutdown ramping rate of a unit. SURRMaximum startup ramping rate of a unit., T Index and set of time periods.

Simultaneous Provision of Flexible Ramping Product and Demand Relief by Interruptible Loads Considering Economic Incentives

“…The system-level ramp capability requirements are set for both upward and downward directions for each interval in RT dispatch and can vary between different intervals, as shown in Figure 2a. Note that in t 5 , there is only requirement for upward FRP because the net load is expected to increase steeply in this period and no downward FRP is needed. In contrast, only requirement for downward FRP is needed in t 2 and for other intervals such as t 1 and t 4 , FRPs for both directions are required.…”

“…The general UC constraints include unit ramping up/down limits, unit generation limits, the maximum limits on base load shedding and RES output curtailment, and power balance constraint [5,25]. The FRP-related constraints reflect the system-wide ramp capability requirement, the impacts of FRP on unit generation and the maximum limits on interruptible load shedding.…”

“…Constraints (15) and (16) define the system-level ramp capability requirements which are composed of the forecasted net load variability (∆L NL t,s ) and additional uncertainty. The magnitude of surrounding uncertainty (φ UP t,s and φ DN t,s ), as explained in Section 2.2, can be constant based on the system scale [26] or is the function of forecasted load and RES output [5]. Finally, constraint (17) points out the positive variables.…”

“…Successful implementations by two ISOs in the United States, i.e., the California ISO (CAISO) and Midcontinent ISO (MISO), have proven the feasibility and practicality of this product [1,2]. FRP is the ramp capability targeting the net system load change between adjacent intervals in real-time (RT) dispatch (e.g., 5-min in CAISO [1] or 10-min in MISO [2]). The net system load, defined as the difference between the actual system load and the total output of variable generation plus scheduled interchanges, always possesses more significant variability and uncertainty than the actual load alone [3].…”

A Flexible Ramping Capacity Model for Generation Scheduling with High Levels of Wind Energy Penetration

“…Their results illustrate how "flexiramp" can improve system flexibility and market efficiency. Chen, R., et al [19] explored the mechanism and possibility of including wind power producers (WPPs) as ramping capacity providers. In [20], the impacts of ramping services on the thermal generation scheduling which include hourly demand response in the deregulated environment were addressed.…”