Power control device

Abstract

A power control device for regulating the power that a load consumes on the basis of the AC supply frequency. The system includes decision logic that responds to a frequency deviation to implement a power regulation strategy. The power regulation strategy includes a power compensation phase during which the electrical power that the load consumes is adjusted (reduced or increased) to balance the load on the grid. The power regulation strategy also includes a power restoration phase during which the power to the load is restored (either increased or decreased). The rate at which the power is adjusted during the power compensation phase is higher than the rate at which the power is restored during the power restoration phase.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a controller for controlling the power consumed by a load connected to an AC supply. The invention also extends to control strategies for such load control function. In a specific and non-limiting example of implementation, the invention finds applications in electrical power grids to improve the grid frequency stability.BACKGROUND OF THE INVENTION[0002]To ensure the reliability of an electric power grid, the administrator must continually maintain a power reserve in order to compensate for a possible failure of energy production units. The power reserve is essentially an excess production capacity on standby. In normal conditions, the power generation units are run at less than 100% such that a degree of reserve power is always available. However, the maintenance of this reserve capacity is an expensive proposition since the reserve constitutes a resource that cannot be effectively monetized by the utility company.[0003]A...

AI Technical Summary

Benefits of technology

[0020]The frequency encoded messages can thus be used to control the power regulation behavior of the power control devices. This can be useful for testing purposes or during contingencies when a certain type of response is more desirable than another. In the case of testing, the grid operator adjusts the frequency of the AC supply to impress on it the desired message which is then sensed by the multiplicity of power control devices connected to the grid. In a specific example, the message can be such as to direct the power control devices to reduce the power of the loads associated with them. By observing the resulting behavior of the grid, the operator can more precisely ascertain the collective level of load reduction that is available and that can be effectively relied upon to provide frequency stabilization. The operator can also ascertain the profile of the load reduction response, in particular the time to reduce the load by a certain amount.

[0021]In yet another broad aspect, the invention provides a method for a grid operator to determine the degree of load reduction available for frequency stabilization purposes, where the grid supplies electrical loads, some of which are controlled by power control devices that reduce the amount of electrical power available to the load when the AC frequency drops below a certain level. The method includes the step of impressing on the AC supply a frequency encoded message directing the power control devices to reduce the electrical power available for the load and observing the effect of the collective reduction on the grid.

Problems solved by technology

However, the maintenance of this reserve capacity is an expensive proposition since the reserve constitutes a resource that cannot be effectively monetized by the utility company.

Any sudden changes in generation or load resulting in an unbalance between generation and load will lead to a frequency instability during which the frequency deviates from its nominal value.

Large frequency variations are undesirable because they could lead to equipment trip or even a system collapse.

The speed governor however has some inherent limitations.

In particular, it is slow to respond since it involves certain mechanical constraints.

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