Patent Application
20240006876
The present disclosure generally relates to the field of overvoltage protection, and more specifically to methods, devices, and systems for limiting a maximum voltage present to downstream components during input overvoltage conditions.
In an electricity meter connected to an electrical grid, a problem can arise in certain applications if there is no load on the electricity meter. For example, a ferroresonance situation can arise when an output wiring of the transformer has sufficient capacitance to cause an output of the transformer that is supplying the electricity meter to resonate, and cause abnormally high voltages to be presented at an input of the electricity meter. Unless the electricity meter is protected from this abnormally high voltage, damage to the electricity meter can occur.
To protect an electricity meter from this type of high voltage situation, some safety mechanisms include switches to disconnect a power supply of the electricity meter when the high voltage conditions occur, which powers down the electricity meter. By disconnecting the power supply and powering down the electricity meter, however, operation of the electricity meter is at least temporarily interrupted.
The detailed description is set forth with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items or features.
This application describes methods, apparatus, and systems for limiting a maximum voltage present to downstream components during input overvoltage conditions. When an input overvoltage condition occurs, an input overvoltage protection effectively limits an input voltage experienced by sensitive components downstream from the input overvoltage protection by limiting a charge on a bulk capacitor by providing a different ground for the bulk capacitor, thereby allowing the sensitive components to continue to function. In some instances, the techniques described herein may be applicable in the case of an extreme input overvoltage condition (e.g., an input overvoltage condition significantly above the maximum operating voltage of the meter power supply components), though the techniques may also be applicable to mitigate smaller input overvoltage situations as well.
As described above with reference to
Under normal operating conditions when there is no overvoltage or a ferroresonance condition, the ground switch 206 is biased “ON” through components that are connected to the high voltage DC 216, which allow current to flow from the power ground 228 to the rectifier ground 218. As current flows from the power ground 228 to the rectifier ground 218 through the ground switch 206, the current charges or maintains the charge on the bulk capacitor 220 during operation. The voltage monitor 204 monitors the AC input voltage at the AC input 118. For example, the voltage monitor 204 may be designed to monitor the AC input voltage and limit the high voltage DC 216 to a rated voltage for the downstream components, for example, 800 Vdc relative to the power ground 228, such that the bulk capacitor 220 and all other downstream components will not experience a voltage above 800 Vdc. When the AC input voltage begins to approach a preselected threshold level, which is a level near the maximum operating range specified for the downstream components, the ground switch 206 is turned “OFF.” By turning off the ground switch 206, the power ground 228 is disconnected from the rectifier ground 218, which prevents the bulk capacitor 220 from continuing to be charged and prevents excessive and damaging voltage from being provided to the downstream components. The ground switch 206 remains off until the AC input voltage at the AC input 118 falls to a safe voltage.
The voltage monitor 204 comprises a voltage input 302, which is connected to the rectifier 214 and receives high voltage DC 216 from the rectifier 214. The rectifier 214 also provides the rectifier ground 218 for the voltage monitor 204. The rectifier ground 218 may also be referred to as a first ground. The voltage monitor 204 may also comprise a voltage divider 304, which is coupled to the voltage input 302 and the rectifier ground 218. The voltage divider 304 may comprise one or more Zener diodes and one or more resistors. In this example, three Zener diodes 306, 308, and 310, and five resistors 312, 314, 316, 318, and 320 are shown. The voltage divider 304 is configured to provide a reference voltage at a first point 322 of the voltage divider 304, which is shown at a junction of the resistors 318 and 320 in this example. Characteristics of the Zener diodes 306, 308, and 310 and values of the resistors 312-320 are selected such that these Zener diodes block voltage low enough to be safe for the downstream components on the high voltage DC 216 from the rectifier 214, but begin to conduct as the voltage on the high voltage DC 216 approaches a critical voltage that is high enough to potentially damage the downstream components. As the Zener diodes 306, 308, and 310 begin to conduct, current flows through the voltage divider 304, and the reference voltage at the first point 322 begins to increase as the voltage on the high voltage DC 216 increases.
The voltage monitor 204 also includes a switch driver, shown in this example as a first field effect transistor (FET) 324, which is designed to control a second FET 326 of the ground switch 206. The second FET 326 is normally, when there is no input overvoltage situation, biased by resistors (three resistors 328, 330, and 332 are shown in this example) and a Zener diode 334, and is in an “ON” state and connects the power ground 228 to the rectifier ground 218. That is, the Zener diode 334 limits the voltage on a gate 336 of the second FET 326 to protect it and prevents current flow through the resistors 328, 330, and 332 to ensure that a voltage at the gate 336 is greater than a gate-source threshold voltage of the FET 326 even at lower AC input voltages. When the gate 336, which is connected to a second point 338, receives a voltage greater than or equal to the gate-source threshold voltage of the second FET 326 relative to a source 340 of the second FET 326, which is connected to the rectifier ground 218, current is allowed to flow from a drain 342 of the second FET 326, which is connected to the power ground 228, to the source 340. The current flow charges and/or maintains charge on the bulk capacitor capacitance 220 during operation. The bulk capacitor 220 in this example is shown to comprise two capacitors 344 and 346 in series.
To control “on/off” state of the second FET 326, “ON/OFF” state of the first FET 324 based on the input AC input voltage is utilized. As described above, the reference voltage at the first point 322 increases as the voltage on the high voltage DC 216 increases, that is, as the AC voltage at the AC input 118 increases. A gate 348 of the first FET 324 is connected to the first point 322 and receives the reference voltage from the voltage divider 304. When the reference voltage reaches a gate-source threshold voltage of the first FET 324, the FET 324 is turned “ON” and current is allowed to flow from a drain 350 of the first FET 324 to a source 352 of the first FET 324. Because the drain 350 is connected to the second point 338 that is also connected to the gate 336 of the second FET 326, and the source 352 is connected to the rectifier ground 218, the Zener diode 334 is shunted when the first FET 324 is “ON” and the gate 336 is grounded. As the gate 336 becomes grounded, the second FET 326 is turned “OFF” and effectively disconnects the power ground 228 from the rectifier ground 218, thereby preventing the voltage between the high voltage DC 216 and the power ground 228 from further increase. By preventing the voltage from further increase, the bulk capacitor 220 is prevented from continuing to charge beyond a predetermined level, which may be set at the highest DC voltage the downstream components can safely tolerate, and the downstream components are prevented from experiencing excessive voltage. A Zener diode 354 is connected to the gate 348 to protect the gate 348.
At block 410, whether the reference voltage is less than or equal to a threshold voltage is determined. When the reference voltage is less than or equal to the threshold voltage (“YES” branch), the rectifier ground 218 may be electrically connected to a second ground, such as the power ground 228, at block 412. As discussed above with reference to
However, when the reference voltage is not less than or equal to the threshold voltage, that is, the reference voltage is higher than the threshold voltage (“No” branch), the rectifier ground 218 may be electrically disconnected form the power ground 228, at block 418. By disconnecting the rectifier ground 218 from the power ground 228, current is prevented from continuing to flow from the power ground 228 to the rectifier ground 218, and, at block 420, the bulk capacitor 220 is charged up to a predetermined level at which the downstream components can safely tolerate. The voltage of the charged capacitor is made available for the downstream components, for example, the power supply of the electricity meter 116 at block 416.
The components of the electricity meter 116 coupled to the processors 502 and the memory 504 may comprise a metrology module 506, an AC input 118, a rectifier 214 providing a high voltage DC 216 and a rectifier ground 218, an input overvoltage protection module 202 comprising a voltage monitor 204 and a ground switch 206, a power supply 508 having ground connection to a power ground 228, and a communication module 510. The metrology module 506 may be capable of measuring various metrology parameters, such as voltage, current, power consumption, and the like associated with the power line 112 and the premises 114 connected to the electricity meter 116. The communication module 510 may communicate with a control center 512 of a utility service provider and provide metrology data associated with the premises 114. In this example, the communication between the communication module 510 and the control center 512 is shown as wireless communication 514, however, the communication may also be made over a wired network, such as the Internet, a cable network, a landline telephone network, and the like.
As discussed above, with reference to
Some or all operations of the methods described above can be performed by execution of computer-readable instructions stored on a computer-readable storage medium, as defined below. The terms “computer-readable medium,” “computer-readable instructions,” and “computer executable instruction” as used in the description and claims, include routines, applications, application modules, program modules, programs, components, data structures, algorithms, and the like. Computer-readable and -executable instructions can be implemented on various system configurations, including single-processor or multiprocessor systems, minicomputers, mainframe computers, personal computers, hand-held computing devices, microprocessor-based, programmable consumer electronics, combinations thereof, and the like.
The computer-readable storage media may include volatile memory (such as random-access memory (RAM)) and/or non-volatile memory (such as read-only memory (ROM), flash memory, etc.). The computer-readable storage media may also include additional removable storage and/or non-removable storage including, but not limited to, flash memory, magnetic storage, optical storage, and/or tape storage that may provide non-volatile storage of computer-readable instructions, data structures, program modules, and the like.
A non-transitory computer-readable storage medium is an example of computer-readable media. Computer-readable media includes at least two types of computer-readable media, namely computer-readable storage media and communications media. Computer-readable storage media includes volatile and non-volatile, removable and non-removable media implemented in any process or technology for storage of information such as computer-readable instructions, data structures, program modules, or other data. Computer-readable storage media includes, but is not limited to, phase change memory (PRAM), static random-access memory (SRAM), dynamic random-access memory (DRAM), other types of random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, compact disk read-only memory (CD-ROM), digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. In contrast, communication media may embody computer-readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave, or other transmission mechanism. As defined herein, computer-readable storage media do not include communication media.
The computer-readable instructions stored on one or more non-transitory computer-readable storage media, when executed by one or more processors, may perform operations described above with reference to
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the claims.
