A GROUND TERMINAL

BACKGROUND

[0001] Embodiments of the present specification generally relate to a power generation system and, in particular, to a power generation system having a direct current (DC) link connected to a ground terminal.

[0002] Some currently available hybrid power generation systems employ a doubly-fed induction generator (DFIG), a prime mover and an auxiliary power source, such as photovoltaic (PV) power source. In some configurations of a power generation system, the auxiliary power source is coupled to the DFIG via one or more power converter(s). During operation of the power generation system, electrical power is generated by one or both of the DFIG and the auxiliary power sources. The electrical power thus generated is supplied to electrical loads and/or an electric grid coupled to the power generation system.

[0003] Typically, the auxiliary power source, such as, the PV power source suffers from potential induced degradation (PID) due to leakage currents flowing to a ground. In some PV power sources, the PV modules with a positive or negative voltage to the ground are exposed to the PID. In some instances, the PID may be accelerated due to increase in temperature and/or voltage of the PV power source. Disadvantageously, such PID leads to losses in the power generated by the PV power source.

BRIEF DESCRIPTION

[0004] In accordance with one embodiment of the present specification, a power generation system is presented. The power generation system includes a doubly-fed induction generator (DFIG) operable via an engine, where the DFIG includes a stator winding and a rotor winding. The power generation system further includes a point of common coupling (PCC) electrically coupled to the stator winding of the DFIG. The power generation system also includes a rotor-side converter electrically connected to the rotor winding of the DFIG. Furthermore, the power generation system includes a line-side converter electrically connected to the PCC. The line-side converter is also electrically connected to the rotor-side converter via a direct-current (DC) link. The DC-link includes a plurality of electrical conductors, and where one electrical conductor of the plurality of electrical conductors of the DC-link is connected to a first ground terminal. Moreover, the power generation system includes a power source electrically coupled to the DC-link.

[0005] In accordance with one embodiment of the present specification, a power generation system is presented. The power generation system includes a doubly-fed induction generator (DFIG) operable via an engine, where the DFIG includes a stator winding and a rotor winding. The power generation system further includes a point of common coupling (PCC) electrically coupled to the stator winding of the DFIG. The power generation system also includes a rotor-side converter electrically connected to the rotor winding of the DFIG. Furthermore, the power generation system includes a line-side converter electrically connected to the PCC. The line-side converter is also electrically connected to the rotor-side converter via a direct-current (DC) link. The DC-link includes a plurality of electrical conductors, and where one electrical conductor of the plurality of electrical conductors of the DC-link is connected to a first ground terminal. Moreover, the power generation system includes a transformer electrically connected between the line-side converter and the PCC. Additionally, the power generation system includes a power source electrically coupled to the DC-link.

DRAWINGS

[0006] These and other features, aspects, and advantages of the present specification will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0007] FIG. 1 is a block diagram representation of a power generation system, in accordance with one embodiment of the present specification;

[0008] FIGS. 2 A, 2B, and 2C represent schematic diagrams depicting a direct current (DC) link of the power generation system of FIG. 1 and connection of the DC-link with a ground terminal, in accordance with some embodiments of the present specification.

[0009] FIG. 3 is a block diagram representation of a power generation system, in accordance with another embodiment of the present specification;

[0010] FIG. 4 is a block diagram representation of a power generation system, in accordance with yet another embodiment of the present specification; and

[0011] FIG. 5 is a schematic diagram representing an electrical equivalent of a doubly-fed induction generator (DFIG) employed in the power generation systems of FIGS. 1, 3, and/or 4, in accordance with one embodiment of the present specification.

DETAILED DESCRIPTION

[0012] In the effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made to achieve the developer's specific goals such as compliance with system-related and business-related constraints. [0013] When describing elements of the various embodiments of the present specification, the articles "a", "an", and "the" are intended to mean that there are one or more of the elements. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0014] As used herein, the terms "may" and "may be" indicate a possibility of an occurrence within a set of circumstances; a possession of a specified property, characteristic or function; and/or qualify another verb by expressing one or more of an ability, capability, or possibility associated with the qualified verb. Accordingly, usage of "may" and "may be" indicates that a modified term is apparently appropriate, capable, or suitable for an indicated capacity, function, or usage, while taking into account that in some circumstances, the modified term may sometimes not be appropriate, capable, or suitable.

[0015] In accordance with some embodiments of the present specification, a power generation system is presented. The power generation system includes a doubly -fed induction generator (DFIG) operable via an engine, where the DFIG includes a stator winding and a rotor winding. The power generation system further includes a point of common coupling (PCC) electrically coupled to the stator winding of the DFIG. The power generation system also includes a rotor-side converter electrically connected to the rotor winding of the DFIG. Furthermore, the power generation system includes a line-side converter electrically connected to the PCC. The line-side converter is also electrically connected to the rotor-side converter via a direct-current (DC) link. The DC-link includes a plurality of electrical conductors, and where one electrical conductor of the plurality of electrical conductors of the DC-link is connected to a first ground terminal. Moreover, the power generation system includes a power source electrically coupled to the DC-link.

[0016] FIG. 1 is a block diagram representation of a power generation system 100 in accordance with one embodiment of the present specification. The power generation system 100 may be configured to generate an alternating current (AC) electrical power and provide the AC electrical power from an output power port 102 of the power generation system 100. The AC electrical power at the output power port 102 may be a single phase or multi -phase, for example, a three-phase electrical power.

[0017] In some embodiments, the output power port 102 of the power generation system 100 may be connected to an electric grid (not shown). Such a power generation system 100 is sometimes also interchangeably referred to as a "grid connected power generation system". The electric grid may be representative of an interconnected network of electrical power sources, electrical power processing systems, and an electrical power distribution systems for delivering a grid power (e.g., electricity) from one or more power generation stations to consumers through high/medium voltage transmission lines. In some embodiments, the power generation system 100 is an islanded power generation system, sometimes also referred to as an isolated power generation system which not connected to the electric grid. By way of example, the isolated power generation system may be deployed where connection of power generation system to the electric grid is not desired or the electric grid is not available. In such a configuration, the output power port 102 of the power generation system 100 may be coupled to an electrical load (not shown). The electrical load may include one or more devices/equipment that consumes electricity when operated. In certain embodiments, the power generation system 100 may be coupled to both the electrical load and the electric grid.

[0018] The power generation system 100 includes one or more of an engine 104, a DFIG 106, a rotor-side converter 108, a line-side converter 110, a power source 112, a DC-link 114, and a PCC 116. In some embodiments, the power generation system 100 may optionally include a switching unit 118 disposed between the DFIG 106 and the PCC 116 to selectively connect the DFIG 106 to the PCC 116. Additionally, in certain embodiments, the power generation system 100 may also include a controller 120. The controller 120 may be operatively coupled to one or more of the rotor-side converter 108, the line-side converter 110, the power source 112, and the switching unit 118 to control operations thereof by communicating appropriate control signals. The controller 120 may include a specially programmed general-purpose computer, an electronic processor such as a microprocessor, a digital signal processor, and/or a microcontroller. Further, the controller 120 may include input/output ports, and a storage medium, such as an electronic memory. Various examples of the microprocessor include, but are not limited to, a reduced instruction set computing (RISC) architecture type microprocessor or a complex instruction set computing (CISC) architecture type microprocessor. Further, the microprocessor may be a single-core type or multi-core type. Alternatively, the controller 120 may be implemented as hardware elements such as circuit boards with processors or as software running on a processor such as a personal computer (PC), or a microcontroller.

[0019] As depicted in FIG. 1, the DFIG 106 is mechanically coupled to the engine 104. The DFIG 106 is also electrically coupled to the PCC 116 via a link 122 and to the rotor-side converter 108 via a link 124, as depicted in FIG. 1. The line-side converter 110 may be electrically coupled to the PCC 116 via a link 126 as shown in FIG. 1. In some embodiments, the line-side converter 110 is electrically coupled to the PCC 116 via the link 126 through a transformer {see FIG. 2). Each of the links 122, 124, and 126 may be a multi-phase link, for example, a three-phase electrical link as shown in FIG. 1. The PCC 116 may be connected to the output power port 102 of the power generation system 100. In some embodiments, the power generation system 100 may optionally include a transformer 128. The transformer 128 may be connected between the PCC 116 and the output power port 102.

[0020] The engine 104 may be configured to aid in imparting a rotational motion to rotary element (e.g., a rotor) of the DFIG 106. The engine 104 may be an internal combustion engine or an external combustion engine. Non-limiting examples of the internal combustion engine that may be used as the engine 104 may include a reciprocating engine such as a diesel engine or a petrol engine, or a rotary engine such as a compressor or a gas turbine. Moreover, the engine 104 may be operated by combustion of various fuels including, but not limited to, diesel, natural gas, petrol, liquefied petroleum gas (LPG), liquefied natural gas (LNG), biogas, producer gas, and the like. The engine 104 may also be operated using waste heat cycle. It is to be noted that the scope of the present specification is not limited with respect to the types of fuel and the engine 104 employed in the power generation system 100. Moreover, the engine 104 may be operable at variable speeds. Alternatively, the engine 104 is also referred to as a variable speed engine.

[0021] The DFIG 106 is operable via the engine 104. The DFIG 106 includes a stator winding 130 and a rotor winding 132. The stator winding 130 may be wound on a stator 134. The rotor winding 132 may be wound on a rotor 136. In some embodiments, both the stator winding 130 and the rotor winding 132 may be multi-phase windings such as a three-phase winding. Additional details of the stator winding 130 and the rotor winding 132 are described in conjunction with FIG. 5.

[0022] The DFIG 106 is mechanically coupled to the engine 104. For example, the rotor 136 of the DFIG 106 is mechanically coupled to a rotary element of the engine 104 via a shaft 138 such that rotations of the rotary element of the engine 104 cause rotations of the rotor 136 of the DFIG 106.

[0023] During operation, the rotor 136 of the DFIG 106 is operated at a rotational speed which may be a synchronous speed, a sub-synchronous speed, or a super-synchronous speed depending on the rotational speed of the rotary element of the engine 104. In one example, the synchronous speed of the rotor 136 may be defined using equation (1).

Equation (1)

[0024] In equation (1), N _s represents the synchronous speed of the rotor 136, p represents poles in the rotor 136, and F represents a frequency of a stator voltage. Accordingly, a sub-synchronous speed of the rotor 136 may be defined as a speed that is lower than the synchronous speed of the rotor 136. Similarly, a super-synchronous speed of the rotor 136 may be defined as a speed that is higher than the synchronous speed of the rotor 136.

[0025] The DFIG 106 is configured to generate an electrical power at the stator winding 130 depending on the rotational speed of the rotor 136. The electrical power that is generated at the stator winding 130 is hereinafter alternatively referred to as a "stator power." Further, the DFIG 106 is configured to generate or absorb electrical power at the rotor winding 132 depending on the rotational speed of the rotor 136. For example, the DFIG 106 is configured to generate electrical power at the rotor winding 132 when the rotor 136 is operated at a super-synchronous speed. The DFIG 106 is configured to absorb the electrical power at the rotor winding 132 when the rotor 136 is operated at a sub -synchronous speed. The electrical power that is generated or absorbed at the rotor winding 132 is hereinafter alternatively referred to as a "slip power." The magnitude of the slip power is dependent on a slip value of the DFIG 106. In one embodiment, the slip value S may be determined using equation (2).

S =— Equation (2) where ^represents the synchronous speed of the rotor 136 and N _r represents revolutions per minute (rpm) of the rotor 136.

[0026] The rotor-side converter 108 is electrically coupled to the rotor winding 132 of the DFIG 106 via the link 124. The rotor-side converter 108 may be an AC -DC converter and configured to convert an AC power into a DC power and vice-versa. The line-side converter 110 may be a DC-AC converter and configured to convert the DC power into an AC power and vice-versa. In some embodiments, each of the rotor-side converter 108 and the line-side converter 110 may include one or more switches, for example, semiconductor switches, configured to facilitate power conversion from AC to DC or vice-versa.

[0027] The rotor-side converter 108 is electrically connected to the line-side converter 110 via the DC-link 114. The DC-link 114 includes a plurality of electrical conductors (see FIGS. 2A-2C). In certain embodiments, the DC-link 114 may also include at least one DC-link capacitor (see FIGS. 2A- 2C) electrically coupled between two conductors of the DC-link 114. One electrical conductor of the plurality of electrical conductors of the DC-link 114 is connected to a first ground terminal, hereinafter referred to as a ground terminal 140, of the power generation system 100. Additional details of the DC-link 114 and the connection of the DC-link 114 with the ground terminal 140 are described in conjunction with FIG. 2.

[0028] Moreover, the power generation system 100 also includes the power source 112 that is coupled to the DC-link 114. The power source 112 is capable of generating and/or supplying a secondary power such as a DC power to the DC-link 114. The power source 112 may include an energy storage device, an auxiliary power source, or a combination thereof (see FIG. 3). Non-limiting examples of auxiliary power source 348 may include a photovoltaic (PV) power source, a fuel cell, a renewable energy based power generator, a non-renewable energy based power generator, or combinations thereof. Further details of the power source 112 and the connection of the power source 112 with the DC-link 114 are described in conjunction with FIG. 3. [0029] In some embodiments, where the power source 112 is connected to the DC-link 114, connection of one conductor of the DC-link 114 to the ground terminal 140 may also facilitate a ground connection for the power source 112. Advantageously, a separate ground connection for the power source 112 may not be required. Moreover, the connection of one conductor of the DC-link 1 14 to the ground terminal 140 may also enable use of an ungrounded power source as the power source 112 which may be cheaper in comparison to grounded power source. In a non-limiting example, the ungrounded PV power source may be connected to the DC-link 114. Advantageously, as one conductor of the DC-link 114 is connected to the ground terminal 140, an effect of potential induced degradation (PID) for the ungrounded power source 112 may be minimized or eliminated. Moreover, as the ungrounded power source 112 is cheaper than the grounded PV power source, overall cost of the power generation system 100 is reduced in comparison to traditional power generation systems.

[0030] Furthermore, as one conductor of the DC-link 114 is connected to the ground terminal 140, a fixed potential is applied to the conductor of the DC-link 114 connected thereto. Such connection of the DC-link 114 also minimizes or eliminates generation of common-mode noise in the DC-link 114. Advantageously, additional common-mode filters are not required to be connected to the power source 112. Elimination of additional components leads to further reduction in the cost of the power generation system 100. Additionally, the reduction or elimination of the effect of the PID and/or common-mode noise prolongs a useful life of the power source 112.

[0031] Referring now to FIGS. 2A-2C, schematic diagrams 202, 204, 206 depicting the DC-link 114 of the power generation system 100 of FIG. 1 and connection of the DC-link 114 with the ground terminal 140, in accordance with some embodiments of the present specification are presented. In the embodiments of FIGS. 2A and 2B, the DC-link 114 includes a plurality of electrical conductors 208 and 210. In the embodiment of FIG. 2C, the DC-link 114 may additionally include an electrical conductor 212. The electrical conductor 208 may represent a positive link-conductor maintained at a positive potential, the electrical conductor 210 may represent a negative link-conductor maintained at a negative potential, and the electrical conductor 212 may represent a neutral terminal maintained at a neutral potential. In certain embodiments, the neutral potential may be a zero potential. One of the electrical conductors 208, 210, and 212 may be electrically connected to the ground terminal 140.

[0032] Further, in the embodiment of FIG. 2 A, the DC-link 114 includes a capacitor 214 electrically connected between the electrical conductors 208 and 210. Moreover, the positive link-conductor (i.e., the electrical conductor 208) is connected to the ground terminal 140. The DC-link 114 of FIG. 2B is similar to the DC-link of FIG. 2A. However, in the embodiment depicted in FIG. 2B, the negative link-conductor (i.e., the electrical conductor 210) is connected to the ground terminal 140. [0033] In the embodiment of FIG. 2C, the DC-link 114 includes two capacitors 216 and 218 coupled in series. The series combination of the capacitors 216 and 218 is electrically connected between the electrical conductors 208 and 210, as depicted in FIG. 2C. The electrical conductor 212 represents the neutral terminal which is an interconnection point of the capacitors 216 and 218. As depicted in FIG. 2C, the neutral terminal (i.e., the electrical conductor 212) is connected to the ground terminal 140. In FIG. 2C, although the electrical conductor 212 is shown coupled to the ground terminal 140, any of the other electrical conductors 208 and 210 may also be coupled to the ground terminal 140, without limiting the scope of the present specification.

[0034] FIG. 3 is a block diagram representation of a power generation system 300, in accordance with another embodiment of the present specification. The power generation system 300 of FIG. 3 is representative of one embodiment of the power generation system 100 of FIG. 1. In comparison to the power generation system 100 of FIG. 1, in some embodiments, the power generation system 300 includes an additional element such as a transformer 302. Internal elements of the power source 112 are depicted in FIG. 3. It may be noted that the components of the power generation system 300 that are already described in FIG. 1 are not described again in FIG. 3.

[0035] In some embodiments, the transformer 302 includes a primary side 304 and a secondary side 306. The primary side 304 includes a plurality of primary windings 308, 310, 312 and the secondary side 306 includes a plurality of secondary windings 314, 316, 318. In one embodiment, the plurality of primary windings 308 are connected in a delta configuration, as depicted in FIG. 3. By way of example, the delta configuration may be achieved by connecting the primary windings 308- 312 in a series loop and providing primary phase-terminals 320, 322, 324 at an interconnection of adjacent primary windings of the primary windings 308-312. As depicted in FIG. 3, the primary phase- terminal 320 is electrically connected to an interconnection of the primary windings 308, 312, the primary phase-terminal 322 is electrically connected to an interconnection of the primary windings 308, 310, and the primary phase-terminal 324 is electrically connected to an interconnection of the primary windings 310, 312.

[0036] Moreover, in some embodiments, the plurality of secondary windings 314, 316, 318 is connected in star configuration, as depicted in FIG. 3. By way of example, the star configuration may be achieved by connecting one terminal of each of the secondary windings 314, 316, 318 together at a secondary common terminal 319 and connecting other terminal of the each of the secondary windings 314, 316, 318 to secondary phase-terminals 326, 328, 330, respectively, of the transformer 302.

[0037] As depicted in FIG. 3, the transformer 302 is electrically connected between the line-side converter 110 and the PCC 116. More particularly, the primary side 304 having the primary windings 308 arranged in delta configuration is electrically connected to the line-side converter 110. For example, the primary phase-terminals 320, 322, 324 are respectively connected to phase-lines 332, 334, 336 of the line-side converter 110. Further, the secondary side 306 having the secondary windings 314, 316, 318 arranged in star configuration is electrically connected to the PCC 116. For example, the secondary phase-terminals 326, 328, 330 are respectively connected to phase-lines 338, 340, 342 of the PCC 116.

[0038] In certain embodiments, the secondary side 306 may be connected to a second ground terminal, hereinafter referred to as a ground terminal 344. In particular, the secondary common terminal 319 is connected to the ground terminal 344, where the ground terminal 344 is electrically isolated from the ground terminal 140. Advantageously, such electrical isolation between the first ground terminal 140 and the second ground terminal 344 facilitates galvanic isolation between the line-side converter 110 and the output power port 102 of the power generation systems 300. In instances where the power generation system 300 is a grid-connected power generation system, the electrical isolation between the first ground terminal 140 and the second ground terminal 344 facilitates galvanic isolation between the line-side converter 110 and the electric grid.

[0039] Moreover, the power source 112 may include an energy storage device, an auxiliary power source, or a combination thereof. By way of example, in the embodiment of FIG. 3, the power source 112 is shown to include an energy storage device 346 and an auxiliary power source 348 electrically connected to the DC-link 114. The energy storage device 346 may include one or more batteries, capacitors, or a combination thereof. Non-limiting examples of the auxiliary power source 348 may include a PV power source, a fuel cell, a renewable energy based power generator, a non-renewable energy based power generator, or combinations thereof. In the description, hereinafter, the auxiliary power source 348 is described as the PV power source without limiting the scope of the present specification. The PV power source 348 may include one or more PV arrays, where each PV array may include at least one PV module. A PV module may include a suitable arrangement of a plurality of PV cells. The PV power source 348 generates a DC voltage constituting a secondary electrical power that depends on solar insolation, weather conditions, and/or time of the day. Accordingly, the PV power source 348 is configured to supply at least a portion of the secondary electrical power to the DC-link 114.

[0040] In certain embodiments, the energy storage device 346 and the PV power source 348 of the power source 112 may be coupled to the DC-link 114 via respective DC-DC converters 350, 352 to control supply of the electrical power to the DC-link 114 and/or to control supply of the electrical power to the energy storage device 346 from DC-link 114. The controller 120 may also be operatively connected to the DC-DC converters 350, 352. The DC-DC converter 350, 352 may be operated as a buck converter, a boost converter, or a buck-boost converter, and may be controlled by the controller 120.

[0041] FIG. 4 is a block diagram representation of a power generation system 400, in accordance with another embodiment of the present specification. The power generation system 400 of FIG. 4 is representative of one embodiment of the power generation system 300 of FIG. 3. In comparison to the power generation system 300 of FIG. 3, in some embodiments, the power generation system 400 includes a prime mover 402 mechanically coupled to the DFIG 106. The components of the power generation system 400 that are already described in FIG. 3 are not described again in FIG. 4. The prime mover 402 may be configured to impart a rotational motion to the rotor 136 of the DFIG 106. Non-limiting examples of the prime mover 402 may include an engine such as the engine 104, a wind turbine, or a hydro turbine.

[0042] FIG. 5 is a schematic diagram representing an electrical equivalent 500 of the DFIG 106 employed in the power generation systems 100, 300, and/or 400 of FIGS. 1, 3, and 4, in accordance with one embodiment of the present specification. It may be noted that the electrical equivalent 500 of the DFIG 106, represents configuration of the stator winding 130 and the rotor winding 132 within the DFIG 106. The DFIG 106 may include stator winding terminals 502, 504, 506 and rotor winding terminals 508, 510, 512. The stator winding terminals 502, 504, 506 may be connected to the link 122 and the rotor winding terminals 508, 510, 512 may be connected to the link 124.

[0043] By way of example, in FIG. 5, the stator winding 130 and the rotor winding 132 are shown as three-phase windings. The stator winding 130 may include stator phase-windings 514, 516, 518. The stator phase-windings 514, 516, 518 may be arranged in a star configuration. The star configuration of the stator phase-windings 514, 516, 518 may be achieved by connecting one terminal of each of the stator phase-windings 514, 516, 518 together at a first common terminal 520 and connecting other terminal of the each of the stator phase-windings 514, 516, 518 to the stator winding terminals 502, 504, 506, respectively.

[0044] The rotor winding 132 may include rotor phase-windings 522, 524, 526. The rotor phase- windings 522, 524, 526 may be arranged in a star configuration. The star configuration of the rotor phase-windings 522, 524, 526 may be achieved by connecting one terminal of each of the rotor phase- windings 522, 524, 526 together at a second common terminal 528 and connecting other terminal of the each of the rotor phase-windings 522, 524, 526 to the rotor winding terminals 508, 510, 512, respectively.

[0045] In some embodiments, the first and second common terminals 520, 528 are electrically isolated from each other. In some embodiments, the first and second common terminals 520, 528 are electrically floating. The term "electrically floating" as used herein refers to electrical isolation of respective terminal from any ground terminal. Advantageously, as the rotor-side converter is connected to the rotor winding 132, such configuration of the stator and rotor windings 130, 132 may facilitate galvanic isolation between the rotor-side converter 108 and the output power port 102 of the power generation systems 100, 300, and/or 400. If the power generation systems 100, 300, and/or 400 are grid-connected power generation systems, such configuration of the stator and rotor windings 130, 132 may facilitate galvanic isolation between the rotor-side converter 108 and the electric grid.

[0046] In accordance with some embodiments described herein, a power generation system, such as the power generation systems 100, 300, 400, is provided. In some embodiments, the power generation system includes a DC-link such as the DC-link 114 having one conductor connected a ground terminal 140. Such a connection of the DC-link 114 to the ground terminal 140 may eliminate or minimize the common-mode noise on the DC-link 114 and effect of PID on the power source 112, for example, the PV power source 348. Advantageously, the useful life of the power source 112 may be enhanced. Moreover, use of an ungrounded power source 112, such as the PV power source 348, also results in a reduced overall cost of the power generation system. Additionally, the rotor-side converter 108 and the electric grid are galvanically isolated from each other. Furthermore, the line- side converter 110 and the electric grid are also galvanically isolated from each other. Consequently, reliability of the power generation system may be improved.

[0047] This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspects, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application.