Patent CA-3037183-A1 (CA)
Title: Control approach for power modulation of end-use loads
Inventor: LIAN JIANMING
IPC: H02J3/24
Filed: 2019-03-19
Abstract: In the management of modern power grids, inter-area oscillations are a growing problem stemming from reductions in stability margins arising as power grids are pushed ever closer to their operating limits. The degree of damping of these oscillations typically decreases as power transfers between areas grow larger, especially over weak transmission connections and longer distances. Such oscillations may lead to system breakup and even cascading blackouts.     Apparatus and methods are disclosed for power modulation of a power grid comprising a plurality of end-use loads. Examples of practical applications of the disclosed technology include apparatus and methods for implementing demand-side control to achieve direct modulation of real power demand in order to damp inter-area oscillations or provide frequency regulation. Certain disclosed apparatus and methods can be used for practical applications including active control of devices such as air conditioners, water heaters, plug-in electric vehicles, etc. In some examples, both primary frequency response (rapid) and secondary frequency regulation (slower) become practical on a large scale. Desired goals of speed, accuracy and magnitude can all be achievable through real-time modulation of this heterogeneous collection of multiple types of end-use loads. In some examples of the disclosed technology, three aspects of the power system (generation, transmission and distribution, and demand) can participate in the control of power distribution over large distances and with substantially improved robustness with respect to variations in load and topology in order to prevent or reduce the occurrences of system break up and possible resultant blackouts.     affected by drop-outs or restorations of tie-lines or buses to the grid). For simplicity, the modeling in FIGS. 10-15 assumes only one mode to be lightly damped, thus this mode will dominate over more strongly damped additional modes. [0106] Predominant oscillatory mode: The Alberta mode at 0.324 Hz with 0.5%  damping. [0107] Contingencies: These parameters are assumed fault conditions applied to the system in the MiniWECC model: [0108] Contingency #1: A sudden loss of generator #4 (1275 MW) on bus #9. [0109] Contingency #2: A three-phase fault on the 500 kV line connecting bus #89 and bus #90 resulting in the line tripping after three cycles. [0110] Cases specifying the end-use loads participating in power modulation:  These parameters are the numbers and types of end-use loads (e.g., water heaters, air conditioners, plug-in electric vehicles, etc.) and their power levels which are participating in power modulation. Water heaters located on the six load buses 902-912 are assumed, with 2 GigaWatt (GW) per area in case #1 and 5 GW per area in case #2. [0111] Case #0: No demand-side control is assumed ¨ this is the base-line for comparison with cases #1 and #2. [0112] Case #1: Demand-side control is implemented with a low penetration of a population of water heaters in each area (e.g., a relatively small fraction giving a total of 2 GW per area). With low penetration, the potential damping effectiveness is expected to be lower.  Whether this lower effectiveness is still adequate to modulate power depends on the magnitude of the oscillations in the power grid. [0113] Case #2: A higher penetration of water heaters in each area (a total of 5 GW per area).  The damping effectiveness of case #2 is thus expected to be higher, as illustrated in FIGS. 11-12 and 14-15.     [0114] Coordination period: This is the length of time over which power modulation is effected, after which all end-use loads participating in power modulation are released from the lockout state, and then a new interval of power modulation is started.  End-use loads not participating in power modulation for this coordination period are not affected by this procedure.