Patent Application
20050286274
The invention relates to power supplies, and more particularly, to testing of power supplies.
A typical conventional large-capacity “on-line” UPS may include an AC/DC converter (e.g., a rectifier) that is configured to be coupled to an AC power source, such as a utility source, and a DC/AC converter (e.g., an inverter) that is coupled to the AC/DC converter by a DC link and which produces an AC voltage at an output (load) bus of the UPS. The UPS may further include a bypass circuit, e.g., a static switch, which can be used to couple the AC power source directly to the output bus of the UPS, such that the AC/DC converter and DC/AC converter are bypassed. The bypass circuit can be used, for example, to provide an economy mode of operation and/or to provide power to the load when either or both of the converters are damaged or inoperative.
Factory testing of such a UPS is often performed with a resistive, reactive load and/or a non-linear test load. Performing such tests may require extensive infrastructure, including the loads themselves and a sufficiently high-capacity utility infrastructure to supply the power for the testing. Additionally, significant energy costs may be entailed in such testing, as the energy delivered to the test load in load testing is often dissipated as heat. Such costs may be replicated when the UPS is installed at the customer's premises, where a commissioning test may be performed at installation to ensure that the UPS and associate power delivery components, e.g., lines, switches, breakers and the like, operate as intended at rated load.
Techniques for recycling energy in UPS burn-in testing are described in articles entitled “The Burn-in Test of Three-Phase UPS by Energy Feedback Methods,” by Chen et al., PESC 93 in Seattle Wash., U.S.A., (1993), and “Self-load bank for UPS testing by circulating current method,” by Chu et al., IEE Proc.-Electr. Power Appl., Vol. 141, No. 4 (July 1994). Each of these techniques, however, utilize specialized test equipment that can lead to extra cost, and which can make the test techniques less useful for field testing.
In some embodiments of the invention, methods of operating are provided for a power supply apparatus, such as an on-line UPS, that includes an AC/DC converter circuit having an input configured to be coupled to an AC source, a DC/AC converter circuit having an input coupled to an output of the AC/DC converter circuit by a DC link, and a bypass circuit operative to couple and decouple the output of the DC/AC converter circuit to and from the input of the AC/DC converter circuit. Power is transferred from the output of DC/AC converter circuit via the bypass circuit to conduct a test of the apparatus, such as a factory or field load test. For example, power may be circulated around a loop including the AC/DC converter circuit, the DC/AC converter circuit and the bypass circuit to conduct the test in order to test these components under load. A status of such components may be determined responsive to the test. In further embodiments, such components may be calibrated responsive to the test.
According to some embodiments of the invention, the DC/AC converter circuit and/or the AC/DC converter circuit are controlled responsive to a power command, e.g., a command that represents a desired real power and/or reactive power transfer for conducting the test. The DC/AC converter circuit and/or the AC/DC converter circuit may include a bridge circuit, and controlling the DC/AC converter circuit and/or the AC/DC converter circuit responsive to a power command may include varying a magnitude and/or phase of an AC voltage at a node of the bridge circuit responsive to the power command using, for example, a current mode controlled pulse width modulation (PWM) control loop that receives the command. In further embodiments, power is transferred from the output of the DC/AC converter circuit to the input of the AC/DC converter circuit while concurrently operating the AC/DC converter circuit to regulate a DC voltage on the DC link for the test.
In some embodiments of the present invention, the DC/AC converter circuit and/or the AC/DC converter circuit may be controlled to produce a predetermined current for a test. For example, the DC/AC converter circuit may be controlled to produce a desired harmonic current at the output of the DC/AC converter circuit during a test to simulate a non-linear load, and this current may be compensated by a harmonic current produced by the AC/DC converter circuit.
In further embodiments, power is transferred from the output of the DC/AC converter circuit to the input of the AC/DC converter circuit via the bypass circuit while the input of the AC/DC converter circuit is coupled to the AC power source, e.g., to perform load testing of the apparatus while receiving sufficient power from the AC source to make up for losses in the apparatus. In other embodiments, power is transferred from the output of the DC/AC converter circuit to the input of the AC/DC converter circuit via the bypass circuit while the input of the AC/DC converter circuit is decoupled from the AC power source, e.g., using a battery or other DC source to make up for system losses. In further embodiments, power may be transferred from the output of the DC/AC converter circuit via the bypass circuit for purposes of testing, while power is also provided to a load coupled to the output of the DC/AC converter circuit. In this manner, maintenance and other tests may be performed while maintaining a critical load. In further embodiments, power is transferred from the output of the inverter circuit via the bypass circuit to conduct a test of a DC power source coupled to the DC link, e.g., by conveying current from the DC source to an external AC source via the bypass circuit.
In additional embodiments of the invention, a power supply apparatus includes an AC/DC converter circuit having an input configured to be coupled to an AC source, a DC/AC converter circuit having an input coupled to an output of the AC/DC converter circuit by a DC link, and a bypass circuit operative to couple and decouple the output of the DC/AC converter circuit to and from the input of the AC/DC converter circuit. A test control circuit is operatively associated with the bypass circuit and at least one of the AC/DC converter circuit and the DC/AC converter circuit and configured to cause power transfer from the output of the DC/AC converter circuit via the bypass circuit to conduct a test of the apparatus.
In further embodiments of the invention, a UPS includes a rectifier circuit having an input configured to be coupled to an AC source, an inverter circuit having an output configured to be coupled to a load, a DC link coupled between an output the rectifier circuit and an input of the inverter circuit, a DC power source coupled to the DC link and a bypass circuit operative to couple and decouple the output of the inverter circuit to and from the input of the rectifier circuit. The UPS further includes a test control circuit operatively associated with the bypass circuit and at least one of the rectifier circuit and the inverter circuit and configured to cause power transfer from the output of inverter circuit via the bypass circuit to conduct a test of the apparatus. The test control circuit may be operative to circulate power around a loop including the rectifier circuit, the inverter circuit and the bypass circuit to conduct the test. In further embodiments, the test control circuit is operative to transfer power from the output of the inverter circuit via the bypass circuit to conduct a test of the DC power source, e.g., by conveying current from the DC source to an external AC source.
In still further embodiments of the invention, a computer program product is provided for controlling a power supply apparatus including an AC/DC converter circuit having an input configured to be coupled to an AC source, a DC/AC converter circuit having an input coupled to an output of the AC/DC converter circuit by a DC link, and a bypass circuit operative to couple and decouple the output of the DC/AC converter circuit to and from the input of the AC/DC converter circuit. The computer program product includes a computer readable storage medium having computer readable program code embodied therein, the computer readable program code including program code configured to cause power transfer from the output of DC/AC converter circuit via the bypass circuit to conduct a test of the apparatus. The computer readable program code may include, for example, program code configured to cause power to circulate around a loop including the AC/DC converter circuit, the DC/AC converter circuit and the bypass circuit to conduct the test.
Specific exemplary embodiments of the invention now will be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements. It will 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. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. As used herein the term “and/or” includes any and all combinations of one or more of the associated listed items.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including” and/or “comprising,” when used in this specification, 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.
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 invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As will be appreciated by one of skill in the art, the invention may be embodied as apparatus, methods and computer program products. Embodiments of the invention may include hardware and/or software. Furthermore, the invention may take the form of a computer program product on a computer-usable storage medium having computer-usable program code embodied in the medium. Any suitable computer readable medium may be utilized including hard disks, CD-ROMs, optical storage devices, a transmission media such as those supporting the Internet or an intranet, or magnetic storage devices.
Computer program code for carrying out operations of the invention may be written in an object oriented programming language such as Java®, Smalltalk or C++. However, the computer program code for carrying out operations of the invention may also be written in conventional procedural programming languages, such as the “C” programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).
Embodiments of the invention include circuitry configured to provide functions described herein. It will be appreciated that such circuitry may include analog circuits, digital circuits, and combinations of analog and digital circuits.
The invention is described below with reference to block diagrams and/or operational illustrations of methods, apparatus and computer program products according to various embodiments of the invention. It will be understood that each block of the block diagrams and/or operational illustrations, and combinations of blocks in the block diagrams and/or operational illustrations, can be implemented by analog and/or digital hardware, and/or computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, ASIC, and/or other programmable data processing apparatus, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, create means for implementing the functions/acts specified in the block diagrams and/or operational illustrations. In some alternate implementations, the functions/acts noted in the figures may occur out of the order noted in the block diagrams and/or operational illustrations. For example, two operations shown as occurring in succession may, in fact, be executed substantially concurrently or the operations may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
The apparatus 100 also includes a test control circuit 140 that controls the AC/DC converter circuit 110 and/or the DC/AC converter circuit 120 (i.e., either or both, as shown by dashed lines), and which also controls the bypass circuit 130. More particularly, the test control circuit 140 is operative to cause the bypass circuit 130 to couple the output 124 of the DC/AC converter circuit 120 to the input 112 of the AC/DC converter circuit 110, and to control the AC/DC converter circuit 110 and/or the DC/AC converter circuit 120 to cause power transfer from the output 124 of the DC/AC converter circuit 120 to the input 112 of the AC/DC converter circuit 110 via the bypass circuit 130 to thereby conduct a test, e.g., a burn-in, commissioning, or other test, of the apparatus 100.
The apparatus 200 also includes a test control circuit 240 that controls the inverter circuit 220 and the bypass circuit 230. The test control circuit 240 includes a bypass control circuit 242 that is operative to cause the bypass circuit 230 to couple the output 224 of the inverter circuit 220 to the input 212 of the rectifier circuit 210, and a power control circuit 244 operative to control the inverter circuit 220 to cause power transfer from the output 224 of the inverter circuit 220 to the input 212 of the AC/DC converter circuit 210 via the bypass circuit 230 to conduct a test of the apparatus 200. In particular, the power control circuit 244 is operative to generate a command signal 243 for control circuitry (e.g., current mode PWM control loop circuitry) of the inverter circuit 220 responsive to a power command signal 241, which may, for example, include a real and/or reactive component. For example, the power command signal 241 may command the inverter circuit 220 to transfer power so as to effect a desired loading of the inverter circuit 220, such that components of the UPS, such as power transistors in the rectifier circuit 210 and/or the inverter circuit 220 and associated control electronics and sensors, may be tested at the desired load.
During such testing, the rectifier circuit 210 may operate as it would during normal operation of the UPS, e.g., the rectifier circuit 210 may operate to regulate a DC voltage on the DC link 215 in both normal and test modes. It will be appreciated that, in such an implementation, the rectifier circuit 210 may respond to current demands at the DC link 215 created by the power transfer operations of the inverter circuit 220. Alternatively, as discussed in detail below with reference to
The apparatus 300 also includes test control circuitry for the inverter circuit 320 and the bypass circuit 330 implemented as functional blocks embodied in a processor 350, such as a microprocessor, microcontroller, DSP, or combination thereof. The control circuitry includes a PWM control block 358 that provides one or more pulse-width modulation control signals 357 to the inverter circuit 320 to control operation of the bridge circuit 321. The PWM control block 358 operates responsive to an inverter command signal 355 and one or more feedback signals 359 (e.g., signals representative of voltage and/or currents) associated with operation of the inverter circuit 320. The inverter command signal 355 represents a reference for operation of a control loop for the inverter circuit 320 implemented by the PWM control block 358.
One or more of the feedback signals 359 are also provided to a power control block 356, also implemented in the processor 350, which also receives a power command signal 353, e.g., a signal representative of a real and/or reactive power to be produced by the inverter circuit 320. Responsive to the power command signal 353 and the one or more feedback signals 359, the power control block 356 produces the inverter command signal 355 that is supplied to the PWM control block 358. In this manner, a voltage magnitude and phase at a node 325 of the bridge circuit 321 may be varied to effect a desired power transfer at the output 324 of the inverter circuit 320. A test executive block 352 produces the power command signal 353, and also provides a bypass command signal 351 to a bypass control block 354 implemented in the processor 350. The bypass control block 354 responsively controls the bypass circuit 330 to couple and decouple the output 324 of the inverter circuit 320 and the input 312 of the rectifier circuit 312.
It will be appreciated that the test executive block 352 may be configured to provide various configurations and operations of the apparatus 300 needed to conduct tests, such as loading tests, of the apparatus 300. The test executive block 352 may be further configured to monitor status of components of the apparatus 300 during testing, such as voltages and/or current produced by the apparatus 300, failures of components of the apparatus 300, temperatures of various locations in the apparatus, and the like. It will also be understood that several of the component blocks implemented in processor 350 may serve functions other than the test control functions described above. For example, the power control block 356 and/or the PWM control block 358 may also be used for inverter control during “normal” operations using control blocks other than the test executive block 352.
The phase offset signal θoffset is provided to another summing junction block 440, where it is subtracted from a phase error signal θerror produced by a phase/frequency detector block 435 responsive to a comparison of a signal vbypass, which is representative of a voltage at the input 312 of the rectifier circuit 310 (and, due to the closed state of the bypass circuit 330, of the output 324 of the inverter circuit 320), to a reference signal vref provided to the inverter PWM control circuit 358. The summing junction block 440 produces an adjusted error signal to an error controlled oscillator block 445, which also receives a frequency error signal ωerror from the phase/frequency detector block 435.
The error controlled oscillator block 445 responsively produces a frequency signal that is scaled by a gain block 450 before provision to an accumulator (integrator) including a summing junction block 455 and a zero-order hold (ZOH) block 460. In particular, the error controlled oscillator block 445 produces a signal representative of a desired frequency for the inverter reference signal vref, and the gain block converts this frequency signal into an angle per step signal θstep signal that represents the number of degrees of a sine wave that corresponds to a computational interval of the accumulator including the summing junction block 455 and the ZOH block 460. The accumulator produces an angle reference signal θref, which is converted into a sinusoidal reference signal Refsin by a sine function block 465, i.e., a block that computes sine values corresponding to the angle values of the angle reference signal θref. This sinusoidal reference signal Refsin is multiplied by the magnitude reference signal |Ref| in a multiplier block 470 to produce the inverter reference signal vref.
It will be appreciated that the functional blocks in
As shown in
The apparatus 500 also includes a processor 550 configured to provide control circuitry for the inverter circuit 520 and the bypass circuit 530, including a PWM control block 553, a power control block 552 and a bypass control block 556, which may operate along the lines discussed above with reference to
Still referring to
It will be appreciated that a variety of self-testing schemes fall within the scope of the invention. In some embodiments, if a rectifier of a UPS (or other power supply apparatus) has active components (e.g., along the lines illustrated in
Power supply configurations according to various embodiments of the invention, such as those described above with reference to
According to additional embodiments, a manufacturing facility, customer, or service organization may perform load testing while using reduced or minimal power to enable energy savings. A manufacturing facility that is load testing one of more UPS' would not be required to install a large utility feed that would normally have to supply enough energy for all the UPSs that are tested, as the utility feed would only need to be large enough to cover the losses in the UPS. Testing may be controlled remotely via modem, network, internet, wireless or other communications device.
According to further aspects of the invention, UPS calibration could be automated. For example, if a bypass circuit is used to measure voltage and current and was known to be accurate, this information could be used to calibrate voltage and current measurements in other portions of the UPS. For example, the inverter and rectifier could be turned off but connected via a bypass. In this case no current would be circulating and one could adjust voltage measurements made by the inverter and rectifier so that they match the know accurate bypass voltage. Using a configuration as illustrated in
In the drawings and specification, there have been disclosed exemplary embodiments of the invention. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined by the following claims.
