Patent ID: 12249921

It is noted that the drawings of the disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.

DETAILED DESCRIPTION

As an initial matter, in order to clearly describe the current disclosure, it will become necessary to select certain terminology when referring to and describing relevant machine components within the illustrative embodiments. When doing this, if possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular component may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.

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. Further, the terms “first,” “second,” and “third,” may be used interchangeably to distinguish one component from another and are not intended to signify location or importance of the individual components. It will be further understood that the terms “comprises” 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. “Optional” or “optionally” means that the subsequently described event may or may not occur or that the subsequently described feature may or may not be present and that the description includes instances where the event occurs, or the feature is present and instances where the event does not occur, or the feature is not present.

Where an element or layer is referred to as being “on,” “engaged to,” “connected to,” “coupled to,” or “mounted to” another element or layer, it may be directly on, engaged, connected, coupled, or mounted to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. The verb forms of “couple” and “mount” may be used interchangeably herein.

FIG.1is a schematic diagram of a drive system100for an electrical machine102according to embodiments of the disclosure. As shown, the drive system100includes a plurality of load commutated inverter (LCI) systems104(e.g.,104-1,104-2) arranged in parallel. Although two LCI systems104are depicted in the drive system100, more than two LCI systems104may be included in the drive system100(e.g., depending on the current and power (e.g., torque) requirements of the electrical machine102). InFIG.1, the electrical machine102is depicted as a synchronous motor (e.g., an alternating current (AC) electric motor in which, at steady state, the rotation of a shaft of the electrical machine102is synchronized with the frequency of the supply current).

According to embodiments, the drive system100may be used as a starting converter, a continuous duty drive, or similar system for controlling the source of power, and by extension, the speed and torque provided to various industrial machinery such as the electrical machine102. When the drive system100is a starting converter, for example, (e.g., when a rotating machine (e.g., gas turbomachine) is initially started up from a generally stationary position), the drive system100may function as a variable speed AC drive system. Similarly, the drive system100may operate as a continuous duty drive. For example, the drive system100may operate continuously at the rated torque of the electrical machine102, for example, from near zero to the optimal rated speed of the electrical machine102. The drive system100may also include high starting and accelerating torque capabilities, which for example, may be useful for large conveyors, metal processing, rod, bar, and wire mills, as well as various extrusion, mixing, grinding and compressor applications. In certain embodiments, the drive system100may also include high power capability, as the drive system100may control both the current and power factor of the electrical machine102to control the torque and speed of the electrical machine102. For example, the electrical machine102may be a three-phase synchronous machine, and the drive system100, for example, may be used to start or continuously drive one or more electrical machines102rated at 44 mega-watts (MW) or more.

Referring concurrently toFIGS.1and2, each LCI system104includes a source bridge106(e.g.,106-1,106-2), which is configured as a source converter to convert a 3-phase AC voltage to a DC voltage, and a load bridge108(e.g.,108-1,108-2) that is configured as a load inverter to convert the DC voltage provided by the source bridge106to a variable frequency 3-phase AC voltage, which is supplied to the electrical machine102. The source bridge106and load bridge108of each LCI system104are interconnected by a respective DC link reactor110(e.g.,110-1,110-2). In general, the source bridges106of the LCI systems104may be controlled to vary the amount of current (and torque) that is furnished to the electrical machine102, while the load bridges108of the LCI systems104may be controlled to vary the frequency of the power that is supplied to the electrical machine102.

The source bridge106in each LCI system104generates a current I (e.g., I1, I2) that flows through the DC link reactor110to the load bridge108. The DC link reactor110in each LCI system104provides inductance to smooth the current I delivered by the source bridge106to the load bridge108. For example, the DC link reactor110of each LCI system104may limit ripple current that may flow between the source bridge106and the load bridge108as the input power is rectified from AC to DC. In operation, in each LCI system104, the source bridge106regulates the magnitude of the current I flowing from the source bridge106to the load bridge108through the DC link reactor110. The total current ITotalprovided by the drive system100to the electrical machine102is equal to the sum of the currents I1, I2produced by the LCI systems104.

As depicted in detail inFIG.2, each source bridge106includes, for each phase of the 3-phase AC voltage, an upper leg112(e.g.,112-1,112-2) and a lower leg114(e.g.,114-1,114-2), where the upper and lower legs112,114of each source bridge106include one or a plurality (e.g.,6) of current switching devices116. According to embodiments, the current switching devices116may include, for example, silicon controlled rectifiers (SCRs)—thyristors. The gating of the current switching devices116of the source bridge106of each LCI system104is actuated by a respective gate driver118(e.g.,118-1,118-2).

In the illustrated example, the upper and lower legs112,114of each source bridge106include 6 current switching devices116. The current switching devices116are switched in sequence (e.g., every 60 degrees) to provide a 6-pulse waveform. By having two LCI systems104in parallel whose AC input is shifted by 30 degrees, this results in a 12-pulse output. Such a 12 pulse output provides a less harmonic output (e.g., a more efficient power output and less torque cogging on the electrical machine102). Additional LCI systems may be provided in parallel with the LCI systems104(with corresponding phase shifting of transformers) to provide a “24 pulse” or higher source bridge106.

Similar to the source bridge106, each load bridge108includes, for each phase of the 3-phase AC voltage, an upper leg120(e.g.,120-1,120-2) and a lower leg122(e.g.,122-1,122-2), where the upper and lower legs120,122of the load bridge108include one or a plurality (e.g., 6) of current switching devices116. The gating of the current switching devices116of the load bridge108of each LCI system104is actuated by the respective gate driver118of the LCI system104to convert the DC voltage output by the source bridge106to a variable frequency 3-phase AC voltage, which is provided to the electrical machine102.

As shown inFIG.1, the primary winding130of a source transformer132is connected to a 3-phase AC bus134(e.g., 2080 Vrms or higher). The source transformer132has two sets of 3-phase secondary windings136,138, where the secondary winding136may be delta connected and the secondary winding138may be wye connected. This results in a thirty degree phase shift in the voltages on the secondary windings136,138, which eliminates a large amount of the harmonic currents generated by the drive system100. According to embodiments, the LCI system104-1is connected to the delta connected secondary winding136and the LCI system104-2is connected to the wye connected secondary winding138.

According to embodiments, the drive system100further includes a single controller140(FIG.1) that provides gating instructions to the gate drivers118for controlling the gating of the current switching devices116in the source and load bridges106,108of the LCI systems104(e.g., which current switching devices116to gate and when to gate them). Each LCI system104also includes its own voltage and current feedback system142(e.g.,142-1,142-2) for providing feedback regarding various voltage and/or current values in the LCI system104to the controller140. In some embodiments, the controller140may communicate with the gate drivers118and the voltage and current feedback systems142of the LCI systems104via a high-speed interface144(e.g., a high-speed serial interface).

In the drive system100, the current I produced by the source bridge106in each LCI system104is independently controlled by a respective current regulator146(e.g.,146-1,146-2) of the controller140. A speed regulator148, coupled to the controller140, is provided for monitoring and controlling the speed (and thus the torque) of the electrical machine102. The speed regulator148compares a signal S representative of the speed of the electrical machine102to a signal S′ representative of the desired speed of the electrical machine102and outputs a signal to the controller140indicating the total current ITotalthat is required from the drive system100to operate the electrical machine102at the desired speed. The controller140subsequently divides the required value of the total current ITotalby the number of LCI systems104in the drive system100and sends the result to each current regulator146. In the embodiment depicted inFIGS.1and2, for example, the controller140sends the same value of ITotal/2 to each of the current regulators146-1,146-2(e.g., I1=I2=ITotal/2).

As will be further appreciated, each current regulator146is configured to independently control the current loop within a respective LCI system104. The source bridges106, controlled by the managing and regulating of the firing angle, control the current in the DC link reactors110by changing the voltage across the DC link reactors110. Similarly, the load bridges108, which may also be controlled by the managing and regulating of a firing angle, may maximize the power output and control the output power factor (i.e., the phase angle between the output voltage and current). As used herein, the term firing angle may refer to the angle of the AC voltage waveform at the electrical machine102at which the current switching devices116of the load bridges108are gated.

The voltage and current feedback system142-1provides feedback regarding various voltage and current values in the LCI system104-1to the current regulator146-1. Likewise, the voltage and current feedback system142-2provides feedback regarding various voltage and current values in the LCI system104-2to the current regulator146-2. The voltage and current feedback systems142may be located on the AC side of each of the source and load bridges106,108, measuring the AC line current and AC line voltages.

According to embodiments, the current regulators146-1,146-2operate completely independently from each other. In operation, based on the current feedback received from the voltage and current feedback system142-1, the current regulator146-1determines and instructs the gate driver118-1when to gate the current switching devices116-1in the source bridge106-1to provide the required current I1(e.g., ITotal/2) in the DC link reactor110-1. Similarly, based on the current feedback received from the voltage and current feedback system142-2, and independent of the current regulator146-1, the current regulator146-2determines and instructs the gate driver118-2when to gate the current switching devices116-2in the source bridge106-2to provide the required current I2(e.g., ITotal/2) in the DC link reactor110-2. Advantageously, this ensures that there are no circulating currents between the current regulators146-1,146-2. Further, by using a plurality of independent current regulators146, the source bridge106in each LCI system104will provide the same current in the DC link reactor110independent of the type of components used to implement the source bridges106and any associated cabling.

Unlike the source bridges106, the load bridges108in the LCI systems104of the drive system100may not be controlled independently. According to embodiments, since the load bridges108are connected to the same load (e.g., electrical machine102), a single load bridge control routine may be used. For example, a load bridge controller152may be configured to receive feedback from the voltage and current feedback systems142of the LCIs104regarding the load output voltage and the output current I1, I2(I1=I2) of each load bridge108. Based on this feedback and the total load current (ITotal=I1+I2) output by the load bridges108, the load bridge controller152determines when to gate the current switching devices116-1,116-2in the load bridges108-1,108-2(which current switching devices116-1,116-2to gate and when to gate them) to provide maximum torque to the electrical machine102. The load bridge controller152subsequently sends the same gating instructions to both gate drivers118-1,118-2, such that the same current switching devices116-1,116-2of the load bridges108-1,108-2are synchronized and gated at the same time. Thus, both load bridges108-1,108-2are gated in an identical manner based on the same gating instructions.

As will be appreciated by one skilled in the art, the present disclosure may be embodied as a system, method, or controls that may utilize a computer program product. Accordingly, the present disclosure may include hardware embodiments, software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, the present disclosure may take the form of a computer program enabled control embodied in any tangible medium of expression having computer-usable program code embodied in the medium.

Any combination of one or more computer usable or computer readable medium(s) may be utilized. The computer-usable or computer-readable medium may be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium. More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a transmission media such as those supporting the Internet or an intranet, or a magnetic storage device. Note that the computer-usable or computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted, or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory. In the context of this document, a computer-usable or computer-readable medium may be any medium that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer-usable medium may include a propagated data signal with the computer-usable program code embodied therewith, either in baseband or as part of a carrier wave. The computer usable program code may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc.

Computer program code for carrying out operations of the present disclosure may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++, or the like and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including 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).

The present disclosure is described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the disclosure. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. Also, one of ordinary skill in the art will recognize that additional blocks that describe the processing may be added. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

As discussed herein, various systems and components are described as “determining” or “obtaining” data. It is understood that the corresponding data can be obtained using any solution. For example, the corresponding system/component can generate and/or be used to generate the data, retrieve the data from one or more data stores (e.g., a database), receive the data from another system/component (e.g., a sensor), and/or the like. When the data is not generated by the particular system/component, it is understood that another system/component can be implemented apart from the system/component shown, which generates the data and provides it to the system/component and/or stores the data for access by the system/component.

Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged; such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. “Approximately” or “about” as applied to a particular value of a range, applies to both end values and, unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s).

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiments were chosen and described in order to best explain the principles of the disclosure and their practical application and to enable others of ordinary skill in the art to understand the disclosure such that various modifications to the embodiments as are suited to a particular use may be contemplated.