Field of the Disclosure

[0001] The present disclosure is related to systems and methods for power management, and in particular to power management for energy storage elements.

Background

[0002] Power management systems may be used to control the amount of energy stored by one or more energy storage elements such as batteries. The power management system may determine when energy is released from the energy storage element to power a load, and when energy is stored by the energy storage element. Power management systems may make decisions regarding whether to store or release energy from an energy storage element based upon remotely measured conditions of a power grid to which the power management system is connected. Specifically, a remote device may monitor one or more conditions of the power grid and provide commands to a power management system, which are used to adjust the operating parameters thereof. Operating in this manner may result in efficiency and economic losses due to delayed changes in the operating parameters of the power management system as well as a failure to change operating parameters when local conditions are not precisely reflected in the remotely monitored conditions. In particular, remote devices that monitor the power grid and provide commands to power management systems are often provided and operated by third parties with respect to the power management systems. The commands provided therefrom may not accurately reflect the dynamic conditions of the power grid with necessary resolution to make optimal power management decisions.

Accordingly, there is a need for improved systems and methods for power management. Summary

[0003] In one embodiment, a power management system includes alternating current (AC) to direct current (DC) converter circuitry and control circuitry. The AC to DC converter circuitry is configured to convert AC signals from an AC power source to DC signals. The control circuitry is coupled to the AC to DC converter circuitry. The control circuitry is configured to measure a frequency of AC signals from the AC power grid, and operate the AC to DC converter circuitry to change an amount of energy stored by an energy storage element based on the frequency of the AC signals from the AC power grid. By locally measuring the frequency of the AC signals and operating the AC to DC converter circuitry accordingly, the power management system is able to quickly and dynamically respond to changing conditions of the AC grid. In some embodiments, a response time of the power management system is less than 1 second.

[0004] In one embodiment, a method includes the steps of measuring a frequency of AC signals from an AC power grid, and operating AC to DC converter circuitry to change an amount of energy stored by an energy storage element based on the frequency of the AC signals from the AC power grid. In one embodiment, the frequency is measured by frequency measurement circuitry that is collocated with the AC to DC converter circuitry. By locally measuring the frequency of the AC signals and operating the AC to DC converter based on the local measurements, the AC to DC converter circuitry is able to quickly and dynamically respond to changing conditions of the AC grid.

[0005] Those skilled in the art will appreciate the scope of the present disclosure and realize additional aspects thereof after reading the following detailed description of the preferred embodiments in association with the accompanying drawing figures.

Brief Description of the Drawing Figures

[0006] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. [0007] Figure 1 is a functional schematic illustrating a power management system according to one embodiment of the present disclosure.

[0008] Figure 2 is a functional schematic illustrating details of a power management system according to one embodiment of the present disclosure. [0009] Figure 3 is a functional schematic illustrating a power management system according to one embodiment of the present disclosure.

[0010] Figure 4 is a flow diagram illustrating a method for power management according to one embodiment of the present disclosure.

Detailed Description

[0011] The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

[0012] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present disclosure. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. [0013] It will be understood that when an element such as a layer, region, or substrate is referred to as being "on" or extending "onto" another element, it can be directly on or extend directly onto the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or extending "directly onto" another element, there are no intervening elements present. Likewise, it will be understood that when an element such as a layer, region, or substrate is referred to as being "over" or extending "over" another element, it can be directly over or extend directly over the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly over" or extending "directly over" another element, there are no intervening elements present. It will also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.

[0014] Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element, layer, or region to another element, layer, or region as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.

[0015] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" when used herein specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0016] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0017] Embodiments are described herein with reference to schematic illustrations of embodiments of the disclosure. As such, the actual dimensions of the layers and elements can be different, and variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are expected. For example, a region illustrated or described as square or rectangular can have rounded or curved features, and regions shown as straight lines may have some irregularity. Thus, the regions illustrated in the figures are schematic and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the disclosure. Additionally, sizes of structures or regions may be exaggerated relative to other structures or regions for illustrative purposes and, thus, are provided to illustrate the general structures of the present subject matter and may or may not be drawn to scale. Common elements between figures may be shown herein with common element numbers and may not be subsequently re described.

[0018] Figure 1 is a functional schematic illustrating a power management system 10 and accompanying context according to one embodiment of the present disclosure. The power management system 10 is coupled between an alternating current (AC) power source 12 and a direct current (DC) load 14. An AC load 16 is also coupled to the AC power source 12. One or more energy storage elements 18 are coupled between the power management system 10 and the DC load 14.

[0019] In operation, AC signals from the AC power source 12 are delivered to the power management system 10 and the AC load 16. The AC signals power the AC load 16, which may include any number of individual loads configured to be powered by AC signals. The power management system 10 converts the AC signals to DC signals, which are provided to the DC load 14 and the one or more energy storage elements 18. The DC signals provided to the one or more energy storage elements 18 determine the amount of energy stored or released by the one or more energy storage elements 18. The energy storage elements 18 may be any suitable type of energy storage device, including batteries of all kinds (e.g., lead-acid, lithium, etc.), capacitors, and the like. For the sake of simplicity, the current drawn by the one or more energy storage elements 18 can be assumed to be proportional to a voltage of the DC signals provided by the power management system 10. However, the power management system 10 may utilize any number of methods for controlling the current drawn by the one or more energy storage elements 18 and thus how much energy is stored and released therefrom. For example, the power management system 10 may communicate using any number of analog or digital signals with control circuitry (not shown) for the one or more energy storage elements 18 in order to control the current drawn and thus the amount of energy stored or released therefrom. It can also be assumed that the current drawn by the DC load 14 remains constant over varying voltages of the DC signals provided by the power management system 10. The one or more energy storage elements 18 can be used as both a current source and a current sink, such that when the voltage of the DC signals provided by the power management system 10 is greater than a terminal voltage of the one or more energy storage elements 18, current flows into the one or more energy storage elements 18 such that energy is stored therein. When a voltage of the DC signals provided by the power management system 10 is less than a terminal voltage of the one or more energy storage elements 18, current flows out of the one or more energy storage elements 18 such that energy is released therefrom. The outgoing current from the one or more energy storage elements 18 may power the DC load 14, or may be converted back into AC signals by the power management system 10 and provided back towards the AC power source 12, which may be an AC power grid, such that it can power the AC load 16.

[0020] As discussed above, in conventional power management systems the voltage of the DC signals and thus the energy stored and released by the one or more energy storage elements 18 has been determined by remotely measured conditions of the AC power source 12. In particular, conditions of the AC power source 12 such as an AC power grid are monitored by a remote device and translated into commands that are delivered to the power management system 10. These commands may dictate the voltage of the DC signals provided by the power management system 10 and thus how much energy is stored and/or released by the one or more energy storage elements 18. However, as discussed above, operating in this manner may result in efficiency and economic losses due to delayed changes in the operation of the power management system 10 and a failure to act when local conditions are not precisely reflected in the remotely measured conditions.

[0021] To solve these problems, the power management system 10 is configured to locally monitor one or more conditions of the AC power source 12 and update one or more operating parameters based on the locally monitored conditions. In one embodiment, the power management system 10 locally monitors the frequency of AC signals provided from the AC power source 12 and changes one or more characteristics of the DC signals provided to the DC load 14 and the one or more energy storage elements 18 based on the measured frequency. As discussed above, this may in turn control the amount of current consumed or provided by the one or more energy storage elements 18 and thus the amount of energy stored or released therefrom. By using the frequency as measured locally by the power management system 10 to adjust the amount of energy stored or released from the one or more energy storage elements 18, changing conditions of the AC power source 12 may be readily adapted to.

[0022] Those skilled in the art will appreciate that AC signals from an AC power source 12 are provided having a nominal operating frequency. In the United States, for example, AC signals on the power grid are generally provided having a frequency of 60 Hz. In New Zealand, AC signals on the power grid are generally provided having a frequency of 50 Hz. Whatever the nominal operating frequency, the actual frequency of AC signals on the power grid may be lower or higher. When the frequency of AC signals on a power grid is lower than the nominal operating frequency, this may indicate a demand for power that is higher than the current supply. Conversely, when the frequency of AC signals on a power grid is higher than the nominal operating frequency, this may indicate that the supply of power is higher than the current demand. Power suppliers monitor these conditions and change the amount of power being supplied to maintain the frequency of AC signals as close to the nominal operating frequency as possible. [0023] Those skilled in the art will also appreciate that the wholesale price of electricity changes based on the supply and demand on a power grid. When demand is high and supply is low, the wholesale price of electricity may increase. Conversely, when demand is low and supply is high, the price of electricity may decrease. When buying electricity at wholesale prices, it is therefore desirable to consume electricity when demand is low and supply is high and, if possible, put electricity back onto the grid when demand is high and supply is low.

[0024] With the above in mind, the power management system 10 can locally monitor conditions of the AC power source 12, which, as discussed above may be an AC power grid, and make decisions regarding the storage or release of energy from the one or more energy storage elements 18 based thereon. For example, when the frequency of AC signals from the AC power source 12 is below a nominal operating frequency, the power management system 10 can cause the energy storage elements 18 to release energy as current. The current can power the DC load 14, can be converted back into AC signals and put back onto the grid to power the AC load 16, or both. The local measurement of frequency enables the power management system 10 to quickly and dynamically respond to changing conditions of the AC power grid, which may result in higher efficiency and better economic outcomes. In some embodiments, the response time of the power management system 10 is less than 1 second. That is, the power management system 10 is able to change the amount of energy stored in the energy storage elements 18 based on a change in the frequency of AC signals from the AC power source 12 in less than 1 second. The response time enabled by the local control mechanism discussed herein is significantly faster than conventional distributed approaches. In some embodiments, the response time of the power management system 10 may be 6 times faster than conventional approaches. [0025] As discussed above, the power management system 10 may be used with any suitable type of energy storage devices. In one embodiment, the one or more energy storage elements 18 are part of an uninterruptible power system (UPS). In another embodiment, the one or more energy storage elements 18 are part of an energy storage system (ESS). The type of energy storage devices including their capacity for holding a charge (storing energy), their charge time, etc. may be taken into account by the power management system 10 when making decisions regarding how much energy to store or release therefrom. [0026] In one exemplary embodiment, the power management system 10 may be used along with a UPS for a telecommunications base station. Those skilled in the art will appreciate that telecommunications base stations must have an associated UPS to maintain network uptime when a connected power grid is not available. Since there are a large number of telecommunications base stations distributed in any given developed area, the principles of the present disclosure may enable quick responses to changes in demand and supply on the power grid, improving the stability of power distribution and further enabling the owners of telecommunications base stations to save and/or make money by utilizing existing equipment.

[0027] In another exemplary embodiment, the power management system 10 may be used along with lithium-based batteries. Those skilled in the art will appreciate that lithium-based batteries may be capable of high-density energy storage, and that it is generally recommended not to charge these batteries to their full capacity in order to maintain the life thereof. For example, oftentimes lithium-based batteries will be charged only to 85-90% of their full storage capacity. The power management system 10 may be configured to utilize the 10-15% charge storage “headroom” of lithium-based batteries for the short-term storage of energy when the measured frequency of AC signals from the AC power source 12 is high, indicating increased supply and decreased demand and thus lower wholesale electricity prices, using the charge stored in this headroom when the measured frequency of AC signals from the AC power source 12 reduces. The short-term use of the battery headroom may result in minimal decrease in the life of the battery while allowing for significant cost savings in electricity.

[0028] In various embodiments, the amount of energy that may be released from the one or more energy storage elements 18 by the power management system 10 may be capped to a certain percentage of the overall charge storage capability thereof. For example, in the case of a UPS, it is undesirable to utilize all of the stored charge of the energy storage elements 18 thereof, as doing so will render the UPS unable to power the equipment it is meant to keep on. The power management system 10 may thus keep a minimum amount of charge in the one or more energy storage elements 18 at all times (e.g., 50%, 25%, 10%, or the like).

[0029] Figure 2 shows details of the power management system 10 according to one embodiment of the present disclosure. The power management system 10 includes AC to DC converter circuitry 20 and control circuitry 22. The AC to DC converter circuitry 20 is coupled between the AC power source 12 and the DC load 14. The AC to DC converter circuitry 20 includes rectifier circuitry 24 and inverter circuitry 26. The rectifier circuitry 24 is configured to receive AC signals from the AC power source 12, convert the AC signals into DC signals, and provide DC signals to the DC load 14 and one or more energy storage elements 18. Conversely, the inverter circuitry 26 is configured to receive DC signals from the one or more energy storage elements 18, convert the DC signals into AC signals, and provide the AC signals back towards the AC power source 12, where they can be used, for example, to power the AC load 16.

Those skilled in the art will appreciate that there are countless circuit topologies for providing rectifier circuitry 24 and inverter circuitry 26 including both active and passive topologies, all of which are contemplated herein. The control circuitry 22 includes frequency measurement circuitry 28. The frequency measurement circuitry 28 is configured to locally measure a frequency of AC signals from the AC power source 12 and make decisions regarding how much energy to store or release from the one or more energy storage elements 18 based thereon as discussed above. To do so, the control circuitry 22 may be coupled to the AC to DC converter circuitry 20 in order to control the operation thereof. In particular, the control circuitry 22 may provide control signals to the AC to DC converter circuitry 20 which change the value of a variable component (e.g., variable resistor, capacitor, or inductor), open or close one or more switches, or the like. The power management system 10 can thus operate as described above to store and release energy from the one or more energy storage elements 18 based on dynamically changing conditions of the AC power source 12.

[0030] The control circuitry 22 may operate in a first mode of operation and a second mode of operation. In the first mode of operation, the control circuitry 22 is configured to cause the AC to DC converter circuitry 20 to increase the amount of energy in the one or more energy storage elements 18. As discussed above, this may be accomplished by increasing the voltage of DC signals provided to the one or more energy storage elements 18. This may also cause the one or more energy storage elements 18 to provide less power to the DC load 14, or to cease providing power to the DC load, since current is flowing into the one or more energy storage elements 18 instead of out of. In the first mode, the DC load 14 may thus be primarily powered by the AC to DC converter circuitry 20. In the second mode of operation, the control circuitry 22 is configured to cause the AC to DC converter circuitry to decrease the amount of energy stored in the one or more energy storage elements 18. As discussed above, this may be accomplished by decreasing the voltage of DC signals provided to the one or more energy storage elements 18. This may also cause the one or more energy storage elements 18 to provide more power to the DC load 14, and in some cases completely power the DC load 14, since current is flowing out of the one or more energy storage elements 18. In the second mode of operation, the control circuitry 22 may also cause the AC to DC converter circuitry 20 to convert DC signals from the one or more energy storage elements 18 to AC signals, which are provided back towards the AC power source 12 and thus may power the AC load 16. [0031] Notably, the configuration shown in Figure 2 for the power management system 10 is only exemplary. The various functional parts of the power management system 10 may be further separated into additional functional components, or combined into fewer functional components without departing from the principles of the present disclosure. Further, the power management system 10 may include other functional components that are not shown, such as communications circuitry for communicating with one or more remote devices such as control circuitry associated with the one or more energy storage elements 18 or a remote monitoring system to monitor for remote commands that may or may not be used to change the operation thereof.

[0032] Figure 3 is a functional schematic illustrating the power management system 10 and accompanying context according to an additional embodiment of the present disclosure. Notably, Figure 3 shows the power management system 10 integrated into a three-phase power system. As shown, the AC power source 12 is a three-phase power source providing a signal for each phase thereof. Those skilled in the art will appreciate that the AC signals at each phase are 120° or 2TT/3 radians out of phase with one another. Each phase includes an AC load 16 (individually labeled as 16A through 16C) and a power management system 10 (individually labeled as 10A through 10C). Each power management system connects to a single DC output, which may be referred to as a DC bus, where the DC load 14 and one or more energy storage elements 18 are coupled. Each power management system 10 operates as described above to control the storage or release of energy from the one or more energy storage elements 18. Each power management system 10 may operate independently from the other, monitoring the frequency of AC signals on the phase to which it is connected as described above. Each power management system 10 may also communicate with the other power management systems 10 to coordinate the operation thereof. While a separate power management system 10 is shown for each phase of the three-phase system shown in Figure 3, a single power management system 10 could also be provided to support all of the phases of a three-phase system in some embodiments. [0033] Figure 4 is a flow diagram illustrating a method for power management according to one embodiment of the present disclosure. First, the frequency of AC signals from an AC power source (step 100). Notably, as discussed above, the frequency of the AC signals is measured locally at a power management system 10. An AC to DC converter is then operated to change an amount of energy stored by one or more energy storage elements based on the measured frequency (step 102). As discussed above, the AC to DC converter can be operated to store energy in the one or more energy storage elements when the frequency is high and release energy from the one or more energy storage elements when the frequency is low. Further, this could change the amount of power delivered from the one or more energy storage elements to a DC load, and further can be used to provide power back towards an AC power source and thus power one or more AC loads.

[0034] It is contemplated that any of the foregoing aspects, and/or various separate aspects and features as described herein, may be combined for additional advantage. Any of the various embodiments as disclosed herein may be combined with one or more other disclosed embodiments unless indicated to the contrary herein.

[0035] Those skilled in the art will recognize improvements and modifications to the preferred embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.