VIRTUAL STORAGE WITH FREQUENCY CONTROL CAPABILITIES
Publication Date: 2011-Nov-28
The IP.com Prior Art Database
AbstractGenerally intermittent renewable sources like wind or solar increase the spinning reserve requirements of the grid, which are usually covered by conventional (e.g. thermal) plants. A solution is disclosed in this publication that allows the wind turbines to produce power to full capacity. This is achieved by using the excess wind energy to produce a portion of the heat needed in the conventional "must run" thermal plants. This design is known as "virtual fuel storage" since it reduces the amount of fuel consumption in the system for same operating conditions. The resistive load in this configuration is able to provide an "inertia-like" response that improves system stability and reliability, while reducing wear and tear on conventional units, by reducing their responsive actions to frequency variations.
This publication relates to load balancing in power grids using wind or solar power. Generally intermittent renewable sources like wind or solar increase the spinning reserve requirements of the grid, which are usually covered by conventional (e.g. thermal) plants. In cases of high wind power penetration and favorable wind conditions a large portion of the load (especially during low load conditions) is supplied by wind power. Wind power is often curtailed, and hence wasted, in order to keep a minimum amount of conventional (e.g. thermal) units on-line, to be able to carry the required spinning reserve. A huge amount of freely available wind energy is wasted at high wind and low load conditions, due to the need for conventional "must run" units to provide spinning reserve.
When the critical wind speed is exceeded during high wind power penetration the conventional generators must nevertheless be kept running at minimum power to carry the spinning reserve needed in cases of either a major fast wind drop, or the worst case of a sudden shut off of the wind turbines. This results in reduced utilization of conventional thermal plants, and wasted fuel consumption. Another drawback of high wind penetration is the curtailment of wind power production when the conventional "must run" units are needed to provide the required spinning reserve to reach their minimum generation limits. This lowers the capacity factor of the wind farm. This curtailed (lost) wind energy at high-wind low-load conditions is shown in Figure 1.
Figure 1: Curtailed wind energy at high-wind low-load conditions
Thus energy storage devices like pump hydro, battery or compressed air are often needed to increase the overall capacity of renewable energy generation. These technologies, however, need a huge initial investment. In order to overcome the above drawbacks, a new approach of virtual storage with frequency control capabilities is disclosed.
BRIEF DESCRIPTION OF DRAWINGS
Virtual storage with frequency control capabilities is described further with reference to the following drawings:
Figure 1 illustrates curtailed wind energy at high-wind low-load conditions
Figure 2 illustrates the configuration of virtual storage with frequency control capabilities
Figure 3 illustrates improved system security and reliability by providing “inertia-like” response
Figure 4 illustrates reduced wear and tear of conventional units by reducing their responsive actions to frequency variations
This publication discloses a solution that allows the wind turbines to produce as much power as possible by absorbing the excess wind power through resistive loads in conventional "must-run" thermal plants. The configuration of virtual storage with frequency control capabilities is shown in Figure 2. A cheaper and more flexible solution is introduced for absorbing excess wind power, rather than wasting it through shutting do...