Systems and methods for shunt power factor correction

Abstract

Systems and methods are disclosed that operate to correct the electrical characteristics of an electric distribution system based on analysis at a particular point in the system, for example, at a customer's meter. To do so, the subject characteristic may be measured at the meter. The subject characteristic may be provided to a power inverter controller, which responds by modifying the characteristic of the inverter output to achieve the desired measurement at the meter.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims the benefit of priority to International Application No. PCT / US2016 / 024974, entitled “SYSTEMS AND METHODS FOR SHUNT POWER FACTOR CORRECTION”, filed Mar. 30, 2016, which claims priority to U.S. Provisional Application No. 62 / 140,725, entitled “SYSTEMS AND METHODS FOR SHUNT POWER FACTOR CORRECTION”, filed on Mar. 31, 2015, which claims priority to U.S. Provisional Application No. 62 / 047,443, entitled “SYNCHRONOUS BUCK INVERTER,” filed on Sep. 8, 2014, all of which are incorporated herein by reference as if set forth in their entireties.FIELD OF THE DISCLOSURE[0002]The present disclosure relates to power conversion, and more particularly to ensuring the connection of a load to an electric utility grid has an alternating current (AC) waveform at a desired (e.g., unity) power factor, regardless of the power factor of the load, and regardless of the power factor of the grid. The AC waveform may be generated by an inverte...

AI Technical Summary

Benefits of technology

The patent describes a system and method to improve the power consumption of an electricity distribution system by measuring the power factor at a meter and adjusting it to a desired level using a power inverter. The system includes a controller that analyzes current and sends signals to the power inverter to modify its output to achieve unity power factor at the meter. This results in better power factor and reduced distortion in the electricity distribution system.

Problems solved by technology

If a pure sine wave is desired at the output of the inverter, the effect of any harmonics in the output is a distortion of the desired waveform.

Providing reactive power with lagging current (e.g., by coupling motors containing wire windings to the grid) pulls AC voltage down, and is said to consume or subtract reactive power from the grid.

If the reactive power is not regulated, the grid voltage on the feeder may exceed its permitted level, with possible adverse consequences to loads coupled to the feeder.

This can be particularly problematic when power demand is low and solar power generation is high, such as on sunny weekends in the spring or early summer.

A utility might prevent such an outcome, for example, by upgrading the feeder with thicker cables, or by limiting how much solar power it will allow to be coupled to its distribution feeders.

The higher currents increase the energy lost in the distribution system, and may require larger, more expensive conductors and possibly other equipment as well, such as pole-top capacitor banks.

Because of the increased equipment costs and wasted energy of systems using such additional equipment, electrical utilities will usually charge industrial and commercial customers a penalty where the customer's load results in a low power factor at the respective meter.

Non-linear loads, such as rectifiers, distort the current drawn from the system, resulting in increasing harmonics in the system.

Images