WO2023201425A1

WO2023201425A1 - Power circuit and method of operating a power circuit connected to an x-phase electrical circuit

Info

Publication number: WO2023201425A1
Application number: PCT/CA2023/050525
Authority: WO
Inventors: Jean-François BISSON
Original assignee: Ecole De Technologie Superieure
Priority date: 2022-04-22
Filing date: 2023-04-19
Publication date: 2023-10-26

Abstract

There is described a power circuit for powering phases of an X-phase electric circuit. The X- phase electric circuit having a given number X of phases. The power circuit generally has: a recharge module; and a plurality of capacitor circuits operatively connectable to the X- phase electric circuit and to the recharge module, the plurality of capacitor circuits including a given number M of capacitor circuits exceeding by at least one the given number X of phases of the X-phase electric circuit; wherein, during operation of the power circuit, each phase of the X-phase electric circuit is powered by a corresponding one of the plurality of capacitor circuits and at least one excess capacitor circuit is rechargeably connected to the recharge module.

Description

POWER CIRCUIT AND METHOD OF OPERATING A POWER CIRCUIT CONNECTED TO AN X-PHASE ELECTRICAL CIRCUIT

FIELD

[0001] The present disclosure relates generally to electric circuit voltage control, and, more particularly, to controlling phase voltages of electric motors using the principle of capacitive voltage boost.

BACKGROUND

[0002] The transportation sector has been recognized as a main contributor of greenhouse gas emissions worldwide, representing a substantial part of global emissions. In order to mitigate the effects of climate change, the electrification of the transportation sector has been proposed as an alternative to the widespread use of traditional internal combustion engines. Major strides have been made in recent years in the development of electric cars and trucks, and several commercial models of electric vehicles are available on the market today, including hybrid vehicles. However, the electrification of air transport presents additional technical challenges. Indeed, the distance traveled and the energy consumption per distance is much greater, and minimizing aircraft weight is an important consideration. As a result, electric-powered aircraft remain relatively uncommon today. Manned electrical aviation is in its infancy. A significant milestone was crossed with the world tour of the solar powered electric aircraft Solar Impulse (2015-2016) and the crossing of the English Channel by the Airbus E- fan electric aircraft (2015). However, the performance of both aircraft lags behind that of comparable turbofan-powered commercial airliners. A parallel trend has been the rapid growth of electric-powered drones in the past years, a trend that is projected to increase, but a significant gap remains between unmanned drone technology and manned electric-powered aircraft.

[0003] An important obstacle of large scale commercial electric aviation is energy storage. Nowadays, the specific energy density and volumetric energy density of lithium-ion batteries remains well below that of widely used jet fuels. However, given that the efficiency of an electric motor drive system is typically higher than the efficiency of aviation turbomachines, less energy is required to be airborne. Therefore, electric motor drive systems used in aviation must be high-efficiency and have high power densities, because these factors have a direct impact on the airborne energy required for the trip. Furthermore, aeronautical propellers and fans must operate at high speeds to generate thrust, and the torque load generated by a propeller or fan increases with speed. To ensure a suitable power density, the electric machine must operate in the highest torque and highest speed simultaneously. For this reason, conventional electric motor control schemes may not be suitable for increasing the rotational speed of a propeller or fan.

[0004] Accordingly, there remains a need for further improvements in this area of electric motor control.

SUMMARY

[0005] The present disclosure describes a power circuit which can be used to power X- phase electric circuits such as X-phase electric motors. The power circuit described herein involves capacitive voltage boost in which the X phases of the X-phase electric circuit are powered by a corresponding capacitive circuit. It is noted that the power circuit includes one or more excess capacitive circuits which can be recharged using a recharge module. Accordingly, when one of the capacitive circuits powering one of the phases of the X-phase electric circuit is identified to be discharged, the power circuit is configured to power that one phase of the X-phase electric circuit using one of the recharged excess capacitive circuits and to recharge the discharged capacitive circuit using the recharge module. In some embodiments, a controller monitors the operation of the capacitive circuits which are powering the phases of the X phase-electric circuit in real time or quasi real time, and when deemed convenient, selectively switches the mode of operation of each capacitive circuit from a discharge mode, in which the capacitive circuit powers one of the phases of the X-phase electric circuit, to a recharge mode, in which the capacitive circuit recharges via the recharge module, or vice versa. In this way, the phases of the X-phase electric circuit can be powered by a sufficiently recharged capacitive circuit at almost all times which can in turn allow for smooth operation and high power density.

[0006] In accordance with a first aspect of the present disclosure, there is provided a power circuit for powering phases of an X-phase electric circuit, the X-phase electric circuit having a given number X of phases, the power circuit comprising: a recharge module; and a plurality of capacitor circuits operatively connectable to the X-phase electric circuit and to the recharge module, the plurality of capacitor circuits including a given number M of capacitor circuits exceeding by at least one the given number X of phases of the X-phase electric circuit such that M > X + 1 ; wherein, during operation of the power circuit, each phase of the X-phase electric circuit is powered by a corresponding one of the plurality of capacitor circuits and at least one excess capacitor circuit is rechargeably connected to the recharge module.

[0007] Further in accordance with the first aspect of the present disclosure, the X-phase electric circuit can for example be an X-phase electric motor.

[0008] Still further in accordance with the first aspect of the present disclosure, the power circuit can for example further comprise a resonant circuit including at least one of the plurality of capacitor circuits connected to one ofthe phases of the X-phase electric circuit, the resonant circuit operated at a resonant frequency thereof.

[0009] Still further in accordance with the first aspect ofthe present disclosure, the capacitor circuits can for example include a capacitor (e.g., a fixed capacitor, a variable capacitor); and an H-bridge including two pairs of switches connected between i) the capacitor and ii) selectably at least one of the phases of the X-phase electric circuit and the recharge module, the two pairs of switches operated to control a polarity of the capacitor.

[0010] Still further in accordance with the first aspect of the present disclosure, when fully recharged, the at least one excess capacitor circuit can for example have a voltage value corresponding to a back-electromotive force (back-emf) of the X-phase electric circuit.

[0011] Still further in accordance with the first aspect of the present disclosure, the given number M of capacitor circuits can for example exceed the given number X of phases by more than one, leading to at least two excess capacitor circuits, the recharge module having a plurality of recharge circuits operatively connectable to any of the plurality of capacitor circuits, with at least two of the plurality of recharge circuits being rechargeably connected to corresponding ones of the at least two excess capacitor circuits. [0012] Still further in accordance with the first aspect of the present disclosure, the capacitor circuit can for example include: a capacitor (e.g., a fixed capacitor, a variable capacitor); and a pair of discharge switches for each of the given number X of phases of the X-phase electric circuit, the pair of discharge switches operatively connectable to the capacitor and configured to be connectable to any of the phases of the X-phase electric circuit, wherein when operated in a discharge mode, the capacitor discharges in a given phase of the X-phase electric circuit via a given one of the pairs of discharge switches.

[0013] Still further in accordance with the first aspect of the present disclosure, the plurality of recharge circuits can for example include a given number Y of recharge circuits, the capacitor circuit can for example include: a capacitor; and a pair of recharge switches for each of the given number Y of recharge circuits, the pair of recharge switches operatively connectable to the capacitor and connectable to any of the plurality of recharge circuits, wherein when operated in a recharging mode, the capacitor recharges a given one of the plurality of recharge circuits via a given one of the pairs of recharge switches.

[0014] Still further in accordance with the first aspect of the present disclosure, at least one of the plurality of ca pa citor circuits can for example include a capacitor; and a polarity switching and disconnect circuit operatively connectable between the capacitor and one of any of the phases of the X-phase electric circuit and the recharge module, the polarity switching and disconnect circuit configured for at least one of switching the polarity of the capacitor, disconnecting the capacitor and bypassing the capacitor.

[0015] Still further in accordance with the first aspect of the present disclosure, the recharge module can for example include: an inductor; a freewheeling branch including a reverse current protection device; and a power branch including direct-current (DC) power terminals operatively connectable across the inductor and the capacitor being recharged.

[0016] Still further in accordance with the first aspect of the present disclosure, the power circuit can for example further include a controller communicatively coupled to the plurality of capacitor circuits and to the recharge module, the controller having a processor and a non- transitory memory which has stored thereon instructions that when executed by the processor perform steps for operating the power circuit. [0017] Still further in accordance with the first aspect of the present disclosure, the steps can for example include: upon determining that one of the capacitor circuits powering one of the phases of the X-phase electric circuit is discharged: disconnecting the one of the capacitor circuits from the one of the phases of the X-phase electric circuit; rechargeably connecting the one of the capacitor circuits to the recharge module; and connecting a recharged one of the plurality of capacitor circuits to the one of the phases of the X-phase electric circuit.

[0018] Still further in accordance with the first aspect of the present disclosure, the power circuit can for example further include: controlling a polarity of the one of the capacitor circuits through a polarity and disconnect circuit such that a positive terminal of the capacitor is connected to an input terminal of the recharge circuit; and controlling a polarity of a recharged one of the plurality of capacitor circuits according to a polarity of the one of the phases of the X-phase electric circuit.

[0019] Still further in accordance with the first aspect of the present disclosure, the steps can for example further include, prior to said rechargeably connecting, disconnecting the fully recharged one of the plurality of capacitor circuits from the recharge module.

[0020] Still further in accordance with the first aspect of the present disclosure, the plurality of capacitor circuits can for example be operated in a discharge mode and a recharge mode in an alternating manner.

[0021] Still further in accordance with the first aspect of the present disclosure, the steps can for example further include: connecting the given number of capacitor circuits to corresponding ones of the phases of the X-phase electrical circuit and operating said connected capacitor circuits in a discharge mode; and rechargeably connecting the at least one excess capacitor circuit to the recharge module and operating the at least one excess capacitor circuit in a recharge mode.

[0022] In accordance with a second aspect of the present disclosure, there is provided a method of operating a power circuit connected to an X-phase electric circuit, the X-phase electric circuit having a given number X of phases, the power circuit having a plurality of capacitor circuits operatively connectable to the X-phase electric circuit, the method comprising: during operation of the power circuit: powering each phase of the X-phase electric circuit via a corresponding one of the plurality of capacitor circuits, the plurality of capacitor circuits including a given number M of capacitor circuits exceeding by at least one the given number X of phases of the X-phase electric circuit such that M > X + 1 ; and using a recharge module operatively connectable to any one of the plurality of capacitor circuits, recharging at least one excess capacitor circuit.

[0023] Further in accordance with the second aspect of the present disclosure, the method can for example further comprise: upon determining that one of the capacitor circuits powering one of the phases of the X-phase electric circuit is discharged: disconnecting the one of the capacitor circuits from the one of the phases of the X-phase electric circuit; rechargeably connecting the one of the capacitor circuits to the recharge module; and connecting a recharged one of the plurality of capacitor circuits to the one of the phases of the X-phase electric circuit.

[0024] Still further in accordance with the second aspect of the present disclosure, the method can for example further comprise, priorto said rechargeably connecting, rechargeably disconnecting the fully recharged one of the plurality of capacitor circuits from the recharge module.

[0025] Still further in accordance with the second aspect of the present disclosure, the method can for example further comprise alternating a mode of operation of each of the plurality of capacitor circuits between a discharge mode and a recharge mode.

[0026] Still further in accordance with the second aspect of the present disclosure, when operated in the discharge mode, each capacitor circuits can for example discharge in a given phase of the X-phase electric circuit via a corresponding pair of discharge switches, and when operated in the recharge mode, the recharge module recharges a capacitor of the at least one excess capacitor circuit via a corresponding pair of recharge switches.

[0027] Many further features and combinations thereof concerning embodiments described herein will appear to those skilled in the art following a reading of the instant disclosure. BRIEF DESCRIPTION OF THE FIGURES

[0028] In the figures,

[0029] Figs. 1A-1 C are block diagrams of exemplary phase voltage control systems, in accordance with an illustrative embodiment;

[0030] Figs. 2A-2B are block diagrams of exemplary power circuits, in accordance with an illustrative embodiment;

[0031 ] Figs. 3A-3B are schematic diagrams of exemplary configurable capacitor circuits, in accordance with an illustrative embodiment;

[0032] Figs. 4A-4B are schematic diagrams of exemplary recharge circuits, in accordance with an illustrative embodiment;

[0033] Fig. 5 is a schematic diagram of a modified 2-Level inverter, in accordance with an illustrative embodiment;

[0034] Fig. 6 is a block diagram of a controller, in accordance with an illustrative embodiment;

[0035] Fig. 7 is a state machine of a configurable capacitor circuit, in accordance with an illustrative embodiment;

[0036] Fig. 8 is a block diagram of an example computing device, in accordance with an illustrative embodiment;

[0037] Fig. 9 includes graphs showing speed and torque over time during a run-up of an X- phase electric motor powered using an exemplary power circuit, in accordance with an embodiment;

[0038] Fig. 10 includes graphs showing d-q axis phase voltage and d-q current over time during a run-up of the X-phase electric motor powered by the power circuit, in accordance with an embodiment; [0039] Fig. 11 includes graphs showing temporal evolution of phase A current, VSI phase A output voltage, phase A capacitor circuit voltage and PMSM phase A voltage at 6500 rpm and 14 N.m for the X-phase electric motor powered by the power circuit, in accordance with an embodiment;

[0040] Fig. 12 is a graph showing phase A current and sinusoidal phase current reference at 6500 rpm and 14 N.m for the X-phase electric motor powered by the power circuit, in accordance with an embodiment;

[0041] Fig. 13 includes graphs showing temporal evolution of capacitor circuit 1 current, voltage, PMRS and capacitor polarity selection switches at 6500 rpm and 14 N.m for the X- phase electric motor powered by the power circuit, in accordance with an embodiment;

[0042] Fig. 14 includes graphs showing temporal evolution of the operation of a recharge module at 6500 rpm and 14 N.m for the X-phase electric motor powered by the power circuit, in accordance with an embodiment; and

[0043] Fig. 15 is a graph showing recharged VC1 voltage and capacitor voltage request VCreq as a function of time for the X-phase electric motor powered by the power circuit, in accordance with an embodiment.

DETAILED DESCRIPTION

[0044] For purposes of illustration, reference is made in the present disclosure to systems and methods of controlling phase voltages in a permanent magnet synchronous machine (PMSM) with particular applications to the aeronautical industry, more specifically to electric- powered aircraft. However, it will be understood by the person skilled in the art that the systems and methods disclosed herein may be used for other purposes, such as for controlling phase voltages in an electric machine of any type, or in other industries or fields of technology altogether. The person skilled in the art will recognize the benefits and drawbacks of the embodiments described herein as they apply to a given application and be able to adapt the systems and methods of the present disclosure accordingly.

[0045] The permanent magnet synchronous machine (PMSM) has a favorable efficiency and power density when compared to the other types of electric machines. Additionally, the peak efficiency area of the PMSM occurs at a higher torque among the other types of electric machines, which may ultimately benefit the power density criteria. For these reasons, the PMSM may be an interesting candidate for aeronautical applications. Electric-powered drones are typically equipped with brushless DC motors, which are PMSMs.

[0046] The reliability of PMSMs is considered to be average. Safety and reliability are important factors to consider in the aviation industry. Successful commercial aviation is reliant upon stringent safety and reliability standards. The present disclosure does not deeply cover the safety and reliability aspects of the system. However, as the safety and reliability of a PMSM may be affected by design, many other non-functional aspects in the aviation industry ensure that the safety and reliability requirements are met, including quality control, design processes and certification processes. For those reasons, it is reasonably expected that PMSMs can achieve the levels of safety and reliability required by civil aviation.

[0047] Operating a PMSM at high speed and high torque represents a significant technical challenge. PMSMs generate a back-electromotive force (or back-emf) which is a function of speed, and this back-emf opposes the machine phase voltage.

[0048] For a fixed voltage, once the battery voltage is not sufficient to inject enough q-axis current to generate the maximum motor torque, the PMSM control needs to be operated in field weaking current mode, which increases speed but reduces torque. Typically, field weakening control maintains the PMSM output power, which means that the motor torque shall decrease as the speed increases. When the PMSM is used for an aeronautical propeller, the load increases with speed, and therefore field weakening operation cannot reach the desired operating point, which is both a high torque and high speed operating point.

[0049] A PMSM is an alternating current electrical machine. However, in automotive vehicles, electrical energy is typically stored using a battery or a fuel cell, and both electrical energy storage technologies provide DC power. Therefore, a device to convert DC power into AC power, such as an inverter, is required between the battery and the motor in order to properly supply the electrical power to the PMSM. [0050] To reach the desired operating point, the phase voltage must be increased to at least the voltage of the back-emf at the desired operating speed. However, this has drawbacks. First, considering a fixed battery voltage, the DC link voltage to the inverter needs to be increased using a DC-DC converter. Energy conversion, including DC-DC step-up voltage conversion, generates losses and therefore reduces net efficiency of the system. Also, increasing the phase voltage generates more current harmonics, because the PWM switching generates higher voltage steps which in turn generates higher current ripples. To reduce the current harmonics in the PMSM, a multi-level inverter may be used. The multi-level inverter generates multiple levels of phase voltage, which improves the current harmonics of the motor.

[0051] While operating a PMSM at high speed, the resolution of the AC voltage sine wave generated by PWM switching is reduced, and therefore current harmonics may become significant. Pushing the PMSM speed further, one can understand that at some point, the benefits of the multi-level inverter will vanish if the inverter switching frequency does not allow to fully use the benefits of the multi-level voltage steps (i.e. if the half period of the back-emf is too short to modulate the phase voltage using all voltage levels). To counteract this issue, the multi-level inverter switching frequency must be increased, therefore increasing the switching losses to the benefit of reducing the phase current harmonics.

[0052] Bringing a PMSM to maximum speed at maximum torque requires significant energy conversion steps, and the sum of all losses dedicated to energy conversion (combined step- up voltage conversion and phase current modulation by the inverter) may become significant as the motor torque and speed both increase simultaneously. It can be easily understood that as the motor speed and torque increase, more input electrical power to the PMSM is required. This requires the DC-DC step-up conversion to increase its power conversion by converting more battery current to a higher voltage and a lower current at the inverter input. However, DC-DC step-up converters are not widely available for high power applications. The use of multiple DC-DC converters in parallel or in series would be impractical due to increased cost and additional weight. Figs. 1 A-C illustrate exemplary embodiments of a phase voltage control system 100 for controlling phase voltages (not shown) in an electric machine 104 using the principle of capacitive voltage boost. Fig. 1 A shows a schematic diagram of an embodiment of the phase voltage control system 100 wherein a DC source 110, a motor drive 120, and a mechanical load 122, are provided. The motor drive 120 may include a power circuit 102, an electric machine 104, an inverter 106, and a controller 114. The electric machine 104 may be mechanically coupled to a mechanical load 122 via coupling means 118 for providing mechanical power to the mechanical load 122. In some embodiments, the mechanical load may include, for example, an aeronautical propeller or fan. The coupling means 118 may include, for example, a shaft of electric machine 104. The power circuit 102 may be configured to be operatively connectable to the electric machine 104 by means of electric machine high power AC connections 82 and to the inverter 106 by means of input high power AC connections I O81. The DC source 1 10 may be configured to be operatively connectable to the inverter 106 and to the power circuit 102 by means of high power DC connections 112i and 1122 for supplying DC power to the inverter 106 and to the power circuit 102.

[0053] In one embodiment as illustrated in Fig. 1A, the DC source 1 10 may supply the inverter 106 at DC power terminals (+/-) of the inverter 106 via the high power DC connections 1 12i . In one embodiment, the DC source 110 may supply the power circuit 102 at DC power terminals (+/-) of the power circuit 102 via the high power DC connections 1122. It should be understood that each of the high power AC connections I O81 and 1082 and each of the high power DC connections 112i and 1 122 may include a plurality of phases; in one embodiment, the high power AC connections I O81 and 82 may each include X-phase connections A, B, while the high power DC connections 1 12i and 1 122 may each include positive (+) and negative (-) phases.

[0054] In some embodiments, the electric machine 104 may be an induction machine (IM), a permanent magnet synchronous machines (PMSM), a Brushless DC machine (BLDC), or a switch reluctance machine (SRM), among other possibilities. The electric machine 104 may be a multi-phase (or polyphase) electric machine, having, for instance, 1 , 2, 3, 5, 7, 9, 12, 15, or any number of phases. In one embodiment, the electric machine 104 may be an X-phase electric machine, where the X phases may be exemplarily labeled P1,P2, ... PX. In one embodiment, the electric machine 104 may be a 3-phase electric machine, where the 3 phases may be conventionally labeled A, B, and C. The X-phase electric machine may have conventional or reversed phase rotation (or phase sequence). In the 3-phase case, phase rotation may be commonly designated by “ABC” or “CBA”, respectively. [0055] In some embodiments, the inverter 106 may be provided between the DC source 110 and the power circuit 102, i.e. the inverter 106 may be provided as an intermediate stage in a multi-stage circuit including the DC source 110, the inverter 106 and the power circuit 102. The inverter 106 may convert the DC voltage received from the DC source 110 via high power DC connections 112i into AC voltage in order to power the electric machine 104 via input high power AC connections 1081, the power circuit 102, and electric machine high power AC connections I O82.

[0056] The inverter 106 may have a 2-level topology, a 3-level topology or a multi-level topology including any number of levels greater than three. Multi-level inverters can generate many voltage levels, and therefore may improve the resolution of the output voltage of the inverter 106. The selection of an inverter topology may increase the efficiency of the electrodynamic system. Aside from its own conversion efficiency, the inverter 106 may influence the efficiency of the electric machine 104 due to the current harmonics generated by the DC-AC conversion. In some embodiments, the inverter 106 may be a PWM inverter.

[0057] In some embodiments, the multi-level inverter may be used as an alternative to the two-level inverter. The multi-level inverter may reduce the current harmonics in the electric machine 104, reduce the switching losses, and reduce the voltage stress on the switches. Multi-level inverter topologies may include the Neutral-Point Clamped, l-Type (NPC-I), Neutral Point Clamped, T-Type (NPC-T), Flying Capacitor (FC) and H-Bridge (HB). The NPC-I, FC and HB topologies may allow for an unlimited number of levels. However, as the number of levels increases, the complexity and the number of components also increases. The NPC-I and NPC-T topologies may have similar efficiencies, with the NPC-T being slightly more efficient at low switching frequencies, and the NPC-I being slightly more efficient at high switching frequencies.

[0058] In some embodiments, the 2-level inverter may be used as an alternative to the multilevel inverter. The 2-level inverter may provide a lower complexity and cost.

[0059] In other embodiments, the 3-level inverter may be used as an alternative to the 2- level inverter. For a given switching frequency, the 3-level inverter may generate lower current harmonics compared to the 2-level inverter, therefore increasing the efficiency of the electric machine 104. The total harmonic distortion (THD) may be reduced by increasing the switching frequency of the multi-level inverter, at the cost of additional switching losses. The 3-level inverter may provide lower electromagnetic interference (EMI) emissions and reduce of voltage stress on the switches.

[0060] Fig. 1 B shows a schematic diagram of an embodiment of the phase voltage control system 100 wherein the DC source 110, the motor drive 120, and the mechanical load 122 are provided. The motor drive 120 may have the power circuit 102, the electric machine 104, and the controller 114, and the inverter 106 may be omitted. Accordingly, the high power DC connections 112i, control signals 1162 may be omitted and input high power AC connections I O81 may be connected together. In some embodiments, the DC source 110 may supply DC power directly to the power circuit 102 via high power DC connections 1 122.

[0061] Fig. 1 C shows a schematic diagram of an embodiment of the phase voltage control system 100 wherein the DC sources 1 10i and H O2, a high speed PMSM motor drive 120_x, and an aeronautical propeller 122_x are provided. The high speed PMSM motor drive 120_x may include the power circuit 102, the PMSM 104_x, the modified 2-level inverter 106_x, and the controller 114. The 2-level inverter 106_x may be further modified to connect to DC sources 110i and H O2 neutral connection 117i and to the PMSM wye neutral connection 1172 as described hereinbelow. In some embodiments, an optional current sensor 119 may be installed on the PMSM wye neutral connection 1172 to ease system diagnostic.

[0062] In the embodiment of the phase voltage control system 100 illustrated in Fig. 1 C involving the high speed PMSM motor drive 120_x, a multi-level inverter may be advantageous to reduce the current harmonics, which increase iron losses as speed increases. As the back- emf of a PMSM increases with speed, the DC-link voltage must be increased accordingly, which results in higher voltage stress on the switches of the inverter. As mentioned previously, a multi-level inverter may reduce the voltage stress on the switches.

[0063] Referring now to Figs. 2A and 2B, with additional reference to Figs. 1 A-C , different embodiments of the power circuit 102 will be described. Fig. 2A shows a schematic diagram of an embodiment of the power circuit 102 wherein the power circuit 102 may have M configurable capacitor circuits 202i, 2022, ... , 202M, where M = X + Y, X being the number of phases of the X-phase electric machine 104 and Y being a number of recharge circuits 204i, 204_Y. The capacitor circuits 202i, 2022, .... 202M can form a configurable capacitor module 203. In some embodiments, the power circuit 102 may have M < X + Y configurable capacitor circuits, in which case one or more of the recharge circuits 204i, ... , 204y may be permanently inactive, for instance as a spare provided for the remaining recharge circuits. In some embodiments, the power circuit 102 may have M = X + 1 configurable capacitor circuits, as described below with reference to Fig. 2B. The configurable capacitor circuits 202i are configured to be operatively connectable to the input high power AC connections 1081 and to the electric machine high power AC connections 82 such that, during operation, any X of the configurable capacitor circuits 202i are connected to the input high power AC connections I O81 and to the electric machine high power AC connections I O82 and the remaining of the capacitor circuits 202i is recharging. The power circuit 102 may additionally have Y recharge circuits 204i, ... , 204y, where Y > 1. The recharge circuits 204i, ... , 204y can form a recharge module 205. The recharge circuits 204i may be operatively connectable to any of the configurable capacitor circuits 202i via recharge connections 206i and 2062, such that, during operation, one or more of the configurable capacitor circuits 202i is connected to one or more of the recharge circuits 204i. In some embodiments, the recharge connection 2062 can act as an input terminal for the corresponding recharge circuit. As further described hereinbelow, the power circuit 102 uses the properties of capacitive voltage boost for supplying electrical power to the electric machine 104.

[0064] Fig. 2B shows a schematic diagram of an embodiment of the power circuit 102 wherein the power circuit 102 may have four configurable capacitor circuits 202i, 2022, 202s and 2024, and one recharge circuit 204i. The embodiment of Fig. 2B may be used to supply electrical power to an electric machine 104 having 3 phases, such as the PMSM 104_x. That is, the embodiment of Fig. 2B corresponds to an embodiment of the phase voltage control system 100 wherein M = 4, X = 3 and Y = 1. Other possibilities may apply, for instance wherein M = 7, X = 5 and Y = 2, as will be recognized by the person skilled in the art having the benefit of the present disclosure.

[0065] Referring now to Figs. 3A and 3B, different embodiments of the configurable capacitor circuit 202 will be described. In the embodiment illustrated in Fig. 3A, the configurable capacitor circuit 202 may have one or more capacitor(s) 302. In some embodiments, the capacitor(s) 302 may have a fixed or variable capacitance depending on the application, and it may be provided as a capacitor bank having a plurality of capacitors in a parallel configuration, a series configuration, or a combination of parallel and series configurations. The capacitor(s) 302 may be operatively connectable to a polarity switching and disconnect circuit 304 for switching the polarity of the capacitor(s) 302, for disconnecting (i.e. open-circuiting) the capacitor(s) 302 or to bypass the capacitor(s) 302. In one embodiment, the polarity switching and disconnect circuit 304 includes capacitor first polarity switches 304i and 3044 and capacitor second polarity switches 3042 and 304s arranged in an H-bridge configuration, as will be recognized by the person skilled in the art, the function of which is briefly described herein. When the capacitor first polarity switches 304i and 304 are closed (and the capacitor second polarity switches 3042 and 304s are open), the capacitor 302 is configured in a first polarity. Conversely, when the capacitor first polarity switches 304i and 3044 are open (and the capacitor second polarity switches 3042 and 304s are closed), the capacitor 302 is configured in a second polarity different from the first polarity. As further described hereinbelow, in some embodiments the capacitor first polarity switches 304i and 3044 and the capacitor second polarity switches 3042 and 304s are configured to be mutually exclusive (i.e. open and closed simultaneously) when the configurable capacitor circuit 202 is in a Recharging state (e.g. Recharging state 708) or Discharging state (e.g. Discharging state 720); that is, the capacitor first polarity switches 304i and 3044 will be either open or closed at a given time, while the capacitor second polarity switches 3042 and 304s will be in the opposite state to the capacitor first polarity switches 304i and 3044 at the same given time. The capacitor first polarity switches 304i and 3044 and the capacitor second polarity switches 3042 and 304s may be configured to be in opposite states; that is, when the capacitor first polarity switches 304i and 3044 are closed, the capacitor second polarity switches 3042 and 304s are open, and vice versa. In some embodiments, when the configurable capacitor circuit 202 is in a Recharged state (e.g. Recharged state 714) or in a Discharged state (e.g. the Discharged state 702), the polarity switches 304I,2,3,4 may all be open. Conversely, to bypass the capacitor(s) 302, the polarity switches 304i ,2,3,4 may all be closed.

[0066] With continued reference to Fig. 3A, the configurable capacitor circuit 202 additionally includes first phase switches 306i (exemplarily labeled P1 , P2, ... PX), second phase switches 3062 (exemplarily labeled P1 , P2, PX), first recharge switches 308i (R1 ,

RY), and second recharge switches 3082 (exemplarily labeled R1 , ... , RY) operatively connectable to the capacitor(s) 302 and to the polarity switching and disconnect circuit 304. In some embodiments, the input terminals 2062 of the recharge circuits are accessible through the second recharge switches 3082. The capacitor(s) 302 and the polarity switching and disconnect circuit 304 are operatively connectable to the input high power AC connections I O81 via the first phase switches 306i and to the electric machine high power AC connections 82 via the second phase switches 3062. The capacitor(s) 302 and the polarity switching and disconnect circuit 304 are operatively connectable to any of the Y recharge circuits 204i, ... , 204y via the first recharge switches 308i and second recharge switches 3082. For an X-phase electric machine 104, the first phase switches 306i and second phase switches 3062 may each include at least X phase switches (i.e. at least 2X phase switches in total). The first phase switches 306i are provided upstream of the capacitor(s) 302 (i.e. on the side of the capacitor(s) 302 corresponding to the inverter 106), while the second phase switches 3062 are provided downstream of the capacitor(s) 302 (i.e. on the side of the capacitor(s) 302 corresponding to the electric machine 104).

[0067] In the embodiment illustrated in Fig. 3B, the configurable capacitor circuit 202 has a variable capacitor 302_x. The variable capacitor 302_x is operatively connectable to a polarity switching and disconnect circuit 304H exemplarily has capacitor first polarity switches 304m and 3044H and capacitor second polarity switches 3042H and 3043H arranged in an H-bridge configuration. The configurable capacitor circuit 202 additionally includes first phase switches 306ip (exemplarily labeled AX, BX, and CX), second phase switches 3062P (exemplarily labeled AX, BX, and CX), first recharge switch 308IR (exemplarily labeled RX) and second recharge switch 3082R (exemplarily labeled RX) operatively connectable to the variable capacitor 302_x and to the polarity switching and disconnect circuit 304H. The variable capacitor 302_x and the polarity switching and disconnect circuit 304H are operatively connectable to the input high power AC connections via the first phase switches 306ip and to the electric machine high power AC Connections via the second phase switches 3062P. The variable capacitor 302_x and the polarity switching and disconnect circuit 304H are operatively connectable to a recharge circuit 204i via the first recharge switch 308IR and the second recharge switch 3082R. The first phase switches 306IP and second phase switches 3O62P may each include at least 3 phase switches (i.e. at least 6 phase switches total). The first phase switches 306IP are provided upstream of the variable capacitor 302_x (i.e. on the side of the variable capacitor 302_x corresponding to the inverter 106), while the second phase switches 3062P are provided downstream of the variable capacitor 302_x (i.e. on the side of the variable capacitor 302_x corresponding to the electric machine 104). Other embodiments may apply depending on the application.

[0068] The functionality of a discharging mode of the phase voltage control system 100 will now be described herein with reference to the embodiment Figs. 1 C, 2B and 3B, although it should be understood that other embodiments may apply, for instance the embodiment illustrated in Figs. 1A, 2A and 3A. In the discharging mode, the power circuit 102 may be used to increase the phase voltage of the PMSM 104_x by adding the voltage of a pre-charged capacitor (for instance, the capacitor 302_x embedded within the configurable capacitor circuit 202) to the phase voltage of the PMSM 104_x. In the discharging mode, one of the set of capacitor first polarity switches 304m and 3044H or capacitor second polarity switches 3042H and 3043H is closed, i.e. the capacitor 302_x is configured with either a first or second polarity. The ith configurable capacitor circuit 202i may be connected to the ith phase of the PMSM 104_x and to ith phase of the modified 2-level inverter 106_x via the ith of the first phase switches 306ip and the ith second phase switches 3062P. For instance, the first capacitor circuit 202i may be operatively connected to phase A of the PMSM 104_x and to phase A of the modified 2-level inverter 106_x via the first of the first phase switches 306IP (labeled AX) and the first of the second phase switches 3062P (labeled AX). The second capacitor circuit 2022 may be operatively connected to phase B of the PMSM 104_x and to phase B of the modified 2-level inverter 106_x via the second of the first phase switches 306IP (labeled BX) and the second of the second phase switches 3062P (labeled BX). The third capacitor circuit 202s may be operatively connected to phase C of the PMSM 104_x and to phase C of the modified 2-level inverter 106_x via the third of the first phase switches 306IP (labeled CX) and the third of the second phase switches 3062P (labeled CX). One or more capacitor circuits, for instance the fourth capacitor circuit 2024 does not participate in the discharge mode as it is recharging.

[0069] The functionality of a recharging mode of the phase voltage control system 100 will now be described herein with reference to the embodiment Figs. 1 C, 2B and 3B, although it should be understood that other embodiments may apply, for instance the embodiment illustrated in Figs. 1 A, 2A and 3A. In a recharging mode, one or more capacitors, for instance capacitor 302_x of the fourth capacitor circuit 2024 may be operatively connected to the recharge circuit 204i via the recharge switches 308IR (labeled RX). The dynamic behavior of RLC circuits may be used to recharge the capacitor 302_x before it is discharged in the phases of the PMSM 104_x. The use of an RLC circuit as the capacitor recharge circuit allows the precharged capacitor 302_x to reach voltages above the voltage of the DC supply 110.

[0070] The capacitor circuits 202i alternate between the discharge mode and recharge mode as described herein.

[0071] Referring now to Figs. 4A and 4B, different embodiments of the recharge circuit 204 will be described. The recharge circuit 204 may be configured to recharge the capacitor(s) 302i of the configurable capacitor circuit 202i before the capacitor(s) 302i are discharged in an ith a phase of the X-phase electric machine 104, for instance the PMSM 104_x. In the embodiment illustrated in Fig. 4A, the recharge circuit 204 may include one or more inductors 402 having a recharge inductance L_r. In some embodiments, the inductor(s) 402 may be provided as an inductor bank including a plurality of inductors in a parallel configuration, a series configuration, or a combination of parallel and series configurations. The inductor(s) 402 may be operatively connectable to a DC voltage source 404 generating a DC voltage conventionally labeled Vdc, a reverse current protection device such as a freewheeling diode 406 (also referred to as a flyback diode, snubber diode, commutating diode, suppressor diode, clamp diode, or catch diode, among others) and to a semiconductor device 408. In some embodiments, the semiconductor device 408 may be a MOSFET. The recharge circuit 204 may be configured to apply eitherthe DC voltage Vdc across the inductor402 and capacitor(s) 302i of the configurable capacitor circuit 202i or else to apply zero voltage. When the DC voltage Vdc is applied, the current circulates in a first direction 410 across the recharge circuit 204 through the inductor 402, the DC voltage source 404 and the semiconductor device 408. When zero voltage is applied, the current circulates in a second direction 412 across the recharge circuit through the inductor 402 and the free-wheeling diode 406. In some embodiments, the DC voltage source 404, and semiconductor device 408 may be provided in a power branch 416. The power branch 416 of the recharge circuit 204 may be operatively connected to the inductor(s) 402 via the semiconductor device 408 and to the capacitor(s) 302i of the configurable capacitor circuit 202i via recharge connections 206i and 2062. In some embodiments, the freewheeling diode 406 may be provided in a freewheeling branch 418 according to the embodiment illustrated in Fig. 4A. In some embodiments, the semiconductor device 408 is instructed to apply, via the DC voltage source 404, a given voltage Vdc across the inductors 402, which will activate the power branch 416. In some embodiments, the semiconductor device 408 is instructed to apply a null voltage across the inductor 402 through the freewheeling branch, which will deactivate the power branch 416.

[0072] In the embodiment illustrated in Fig. 4B, the recharge circuit 204 includes an inductor bank 420, an optional protection diode 414, the semiconductor device 408, the high power DC connections 1122, and the freewheeling diode 406. The inductor bank 420 includes inductors 402i, 4022 and 402s each exemplarily having a recharge inductance L_r = 1 mH. Other embodiments may apply depending on the application.

[0073] Referring now to Fig. 5, an embodiment of the modified 2-level inverter 106_x as illustrated in Fig. 1 C will be described. As described previously, in one embodiment the modified 2-level inverter 106_x may be operatively connected to the power circuit 102 and to the PMSM 104_x. In one embodiment, the modified 2-level inverter 106_x may include six semiconductor devices 502i, 5022, 502s, 5024, 5025, and 502e (conventionally labeled S1 , S2, S3, S4, S5, and S6) and three (3) bi-directional switches 504i, 5042, and 5043 according to a Three-Level Neutral Point Clamped T-Type 3 phase inverter topology, as will be recognized by the person skilled in the art.

[0074] The inverter 106_x may have three branches conventionally labeled A, B, C, where branch A has the semiconductor devices 502i and 502 , branch B has the semiconductor devices 5022 and 5025, and branch C has the semiconductor devices 5023 and 502e. In some embodiments, the semiconductor devices 502i, 5022, 5023, 5024, 502s, and 502e may include MOSFETs. The neutral connection 117i of the inverter 106_x may be connected to the PMSM wye neutral connection 1172 of the PMSM 104_x (conventionally labeled N). In some embodiments, the bi-directional switches 504i, 5042, and 5043 may be commanded by a NOR gate of both MOSFET commands on the same branch (e.g. bi-directional switch 504i may be commanded by the NOR gate of MOSFETs 502i and 5024, indicated by the label “S1 & S4”). The bi-directional switches 504i, 5042, and 504s may be configured to be ON when the MOSFETs on the same leg are OFF. The output voltage of the inverter 106_x as a function of its semiconductor device status can be found in Table 1 below.

Table 1

[0075] The inverter 106_x as shown in Fig. 5 may allow independent control of the voltage of each motor phase of PMSM 104_x. The inverter 106_x may generate a phase to neutral voltage of 0V or +/- Vdc/2. The inverter 106_x may allow for freewheeling phase current when the phase voltage is 0V. The inverter 106_x may allow the phase current to be in the direction of the phase voltage or in the opposite direction of the phase voltage. The inverter may allow positive voltages to be generated on all 3 phases simultaneously or a negative phase voltage to be generated on all 3 phases simultaneously.

[0076] Referring now to Fig. 6 with additional reference to Fig. 1A, an embodiment of a controller 114 for controlling the phase voltages in the electric machine 104 will be described. The controller 114 may be communicatively coupled to the electric machine 104, the power circuit 102, the inverter 106, and the DC source 110 via a plurality of control signals, for instance 1161 , 1162, 1163, and 1164. The plurality of control signals 1161 , 1162, 1 1 63, and 1164 may be one-way ortwo-way; that is, at least some of the plurality of control signals 1161 , 1162, 1163, and 1164 may be configured to transmit data from a first device (for instance the DC source 110 or the electric machine 104) to the controller 114 in a first direction, while the remaining of the plurality of control signals 1161, H62, H63, and 116 may be configured to transmit first data, for instance analog input from a plurality of sensors from a first device (for instance the inverter 106 or the power circuit 102) to the controller 114 in a first direction, and to transmit second data, for instance control instructions, from the controller 1 14 to the second device in a second direction opposite to the first direction. In some embodiments, the first device may include one or more of the electric machine 104 and the DC source 110, and the second device may include one or more of the power circuit 102 and the inverter 106.

[0077] In some embodiments, the controller 114 may have at least a first layer 602, a second layer 604, a third layer 606 and a fourth layer 608. A different number and configuration of layers may also be used depending on the application, as will be understood by the person skilled in the art having the benefit of the present disclosure.

[0078] In some embodiments, the at least first layer 602, second layer 604, third layer 606 and fourth layer 608 may be communicatively coupled via a first control interface 610, a second control interface 612, and a third control interface 614, each including a plurality of one-way or two-way control signals. In some embodiments, successive layers of the controller 114 may communicate via the corresponding control interface. For instance, the first layer 602 and the second layer 604 may communicate via the first control interface 610. In some embodiments, non-successive layers of the controller 114 may communicate; for instance, the second layer 604 may communicate directly with the fourth layer 608, bypassing the third layer 606. Other possibilities may also apply.

[0079] In the first layer 602 of the controller 1 14, the controller 114 may be configured to perform analog to digital signal conversion via an analog to digital signal conversion module 602i. The analog to digital signal conversion module 602i may retrieve analog signal data from a plurality of analog sensors (not shown), for instance current sensors, voltage sensors, and rotational position sensors provided with the electric machine 104, the power circuit 102, the inverter 106, and the DC source 110, via, for instance, the plurality of control signals, for instance 116i, 1162, 1163, and 1164 and convert the analog signal data to digital signal data that may be used by the controller 114 at a later stage, for instance by the second layer 604, the third layer 606 and the fourth layer 608. [0080] In the first layer 602 of the controller 1 14, the controller 114 may be configured to perform an electrical frequency calculation via an electrical frequency conversion module 6022, for instance using the formula: w_e = P_p ■ wjnotor

[0081] Where w_e is the electric frequency of the electric machine 104 (in rad/sec), P_p is the number of pole pairs of the electric machine 104, and w_motor is the motor angular speed (in rad/sec) of the electric machine 104.

[0082] It shall be recognized that the first layer 602 of the controller 114 may also have other functionalities not explicitly mentioned herein, e.g. input processing, conversion and calculation steps implemented via any number of modules.

[0083] In a second layer 604 of the controller 114, a main sequencer module 604i may be provided. The main sequencer module 604i may be configured to implement a plurality of functions. The main sequencer module 604i may be operatively connectable to the power circuit 102 and activate the power circuit 102, for instance when a speed threshold of the electric machine 104 is reached. The main sequencer module 604i may be operatively connectable to the first phase switches 306i and second phase switches 3062Of a configurable capacitor circuit 202i, and the main sequencer module 604i may actuate the first phase switches 306i and second phase switches 3062 for discharging the configurable capacitor circuit 202i into an 7th phase of the electric machine 104. The main sequencer module 604i may be operatively connectable to the first recharge switches 308i and the second recharge switches 3082 of the configurable capacitor circuit 202i, and the main sequencer module 604i may actuate the first recharge switches 308i and the second recharge switches 3082 to connect the configurable capacitor circuit 202ito any of the Y recharge circuits 204i, ... , 204y. The main sequencer module 604 may be used to toggle a Discharge Available signal (not shown) on the configurable capacitor circuit 202i to indicate that the configurable capacitor circuit 202i is available for discharging. The main sequencer module 604i may transmit the Recharge Available and Discharge Available signals to a capacitor control module 606i described in further detail hereinbelow. The main sequencer module 604 may be used to perform a Capacitor Voltage Request Calculation (not shown) to calculate a voltage at which the capacitor(s) 302i of the configurable capacitor circuit 202i must be charged before the discharge cycle begins. Similarly, the main sequencer module 604 may be used to toggle a Recharge Available signal (not shown) on the configurable capacitor circuit 202i to indicate that the configurable capacitor circuit 202i is available for recharging.

[0084] In a third layer 606 of the controller 1 14, a plurality of capacitor control modules may be provided. In some embodiments, M capacitor control modules 6O61, 6O62, ... , 606M, where M = X + Y, X being the number of phases of the X-phase electric machine 104. In some embodiments, there is a capacitor control module 606i for each configurable capacitor circuit 202i of the power circuit 102. In the embodiment of the controller 114 shown in Fig. 6, the third layer 606 includes four capacitor control modules 6O61, 6O62, 6O63 and 6O64. The embodiment of Fig. 6 may be applicable to an electric machine 104 having 3 phases, such as the PMSM 104_x. That is, the embodiment of Fig. 6 corresponds to an embodiment of controller 114 wherein M = 4, X = 3 and Y = 1. Other possibilities may apply, as will be recognized by the person skilled in the art having the benefit of the present disclosure.

[0085] The /th capacitor control module 606i may be used to control the /th configurable capacitor circuit 202i of the power circuit 102 as described herein. The capacitor control module 606i may process the Discharge Available and Recharge Available signals from the main sequencer module 604i, received for instance via the second control interface 612. In some embodiments, the capacitor control module 606i may determine a Recharge Cycle Done and Discharge Cycle Done parameter for the configurable capacitor circuit 202i indicating that the recharge cycle and discharge cycle have been completed. In some embodiments, the Recharge Cycle Done and Discharge Cycle done parameters may be boolean parameters. The capacitor control module 606i may be used to determine the state of the configurable capacitor circuit 202i . In some embodiments, the state of the configurable capacitor circuit 202i may include: Discharged, Recharging, Recharged, and Discharging states. In some embodiments, /th capacitor control module 606i may be operatively connectable to the polarity switching and disconnect circuit 304 for switching the polarity of the capacitor(s) 302i of the configurable capacitor circuit 202i, for disconnecting (i.e. open-circuiting) the capacitor(s) 302i or for bypassing the capacitor(s) 302i. In those embodiments wherein the polarity switching and disconnect circuit 304 includes capacitor first polarity switches 304i and 3044 and capacitor second polarity switches 3042 and 304s arranged in an H-bridge configuration, capacitor control module 606i may actuate the first polarity switches 304i and 304 and capacitor second polarity switches 3042 and 304s to change the polarity of the capacitor(s) 302i. In those embodiments wherein the capacitor 302_x has a variable capacitance, the capacitor control module 606i may be used to determine or change the capacitance of the capacitor 302_x. In some embodiments, the capacitor control module 606i may be used to manage the recharge process of the capacitor(s) 302i to ensure that the recharged capacitor voltage corresponds to the Capacitor Voltage Request Calculation. In some embodiments, the capacitor control module 606i may be operatively connectable to the semiconductor device 408 to apply DC voltage Vdc to the recharge inductance 402.

[0086] In some embodiments, the controller 1 14 may have a processor and a non-transitory memory having instructions stored thereon which when executed by the processor perform some method steps. In some embodiments, the controller 1 14 may incorporate hardware components provided in the form of a computing device and software components which can execute logic functions and the like. For instance, the software components may be implemented as VHSIC Hardware Description Language (VHDL) code for implementation in a Field-Programmable Gate Array (FPGA).

[0087] In a fourth layer 608 of the controller 114, switch command signals (not shown) may be issued to the polarity switching and disconnect circuit 304, the first phase switches 306i the second phase switches 3062, the first recharge switches 308i, the second recharge switches 3082 and the semiconductor device 408 of the power circuit 102 via a switch command module 6O81.

[0088] Fig. 7 shows an embodiment of a state machine 700 of the configurable capacitor circuit 202i.

[0089] In the Discharged state 702, the capacitor(s) 302i of the configurable capacitor circuit 202i has the lowest voltage of the cycle described by the state machine 700. In the Discharged state 702, the capacitor control module 606i of the controller 114 is in a Standby state 704 for a Recharge Available signal 706 from the main sequencer module 604i. In the Discharged state 702, the first phase switches 306i, second phase switches 3062 , first recharge switches 308i and second recharge switches 308i are configured to be in an open state to disconnect (i.e. isolate) the capacitor(s) 302i of the configurable capacitor circuit 202i from input high power AC connections IO81, the electric machine high power AC connections 82 and the recharge connections 206i and 2062. Alternatively, in some embodiments the polarity switching and disconnect circuit 304 may be configured to disconnect (i.e. open-circuiting) the capacitor(s) 302i. In those embodiments wherein the capacitor(s) 302_x is has a variable capacitance, capacitance of the capacitor(s) 302_x may be set in the Discharged state 702.

[0090] In the Standby state 704, if a Recharge Available signal 706 from the main sequencer module 604i is received by the configurable capacitor circuit 202i, the state machine may advance to a Recharging state 708.

[0091] In the Recharging state 708, the capacitor(s) 302i of the configurable capacitor circuit 202i may be operatively connected to any of the Y recharge circuits 204i, ... , 204y. In the Recharging state 702, the first phase switches 306i and second phase switches 3062 are configured to be in an open state to disconnect (i.e. isolate) the capacitor(s) 302i of the configurable capacitor circuit 202i from the input high power AC connections IO81 and the electric machine high power AC connections I O82. When initiating the Recharging state 702, the polarity switching and disconnect circuit 304 may be configured such that the positive voltage terminal of the capacitor(s) 302i is connected to an input of any of the Y recharge circuits 204i, ... , 204y via the second recharge switches 3082. In the Recharging state 702, the capacitor control module 606i may monitor the recharge energy input and actuate (i.e. close) the semiconductor device 408 of the recharge circuit 204 while the energy of the capacitor(s) 302i is lower than a Capacitor Energy Request (not shown). The capacitor control module 606i may actuate (i.e. open) the semiconductor device 408 of the recharge circuit 204 when the energy of the capacitor(s) 302i reaches the Capacitor Energy Request (not shown). Current through the recharge circuit 204 may then circulate in the second direction 412 through the free-wheeling diode 406. The capacitor control module 606i may detect that the capacitor recharge is completed and set a Recharge Cycle Done parameter 712. [0092] The capacitor control module 606i of the controller 1 14 may remain in the Recharging state 708 until the Recharge Cycle Done parameter 712 is set, as indicated at 710.

[0093] In a Recharged state 714, the capacitor(s) 302i of the configurable capacitor circuit 202i have the highest voltage of the cycle described by the state machine 700. In the Recharged state 714, the capacitor control module 606i of the controller 114 may be in a Standby state 716 for a Discharge Available signal 718 to be set by the main sequencer module 604i. In the Recharged state 714, the first phase switches 306i, second phase switches 3062, first recharge switches 308i and second recharge switches 3082 are configured to be in an open state to disconnect (i.e. isolate) the capacitor(s) 302i of the configurable capacitor circuit 202i from the input high power AC connections 1081 , the electric machine high power AC connections 82 and the recharge connections 206i and 2062. Alternatively, in some embodiments the polarity switching and disconnect circuit 304 may be configured to disconnect (i.e. open-circuit) the capacitor(s) 302i.

[0094] In a Discharging state 720, the capacitor(s) 302i of the configurable capacitor circuit 202i may be operatively connected to the input high power AC Connections I O81 via the first phase switches 306i and to the electric machine high power AC connections 82 via the second phase switches 3062. The first phase switches 306i and second phase switches 3062 may be configured to be in a closed state to connect the capacitor(s) 302i of the configurable capacitor circuit 202ito the input high power AC connections I O81 and the rth phase of electric machine 104. The polarity switching and disconnect circuit 304 may be configured to set the capacitor(s) 302i Of the configurable capacitor circuit 202i to a desired capacitor polarity for a given discharge cycle. The capacitor control module 606i may detect that the capacitor discharge is completed and set a Discharge Cycle Done parameter 724.

[0095] The capacitor control module 606i of the controller 114 may remain in the Discharging state 720 until the Discharge Cycle Done parameter 712 is set, as indicated by at 722.

[0096] Fig. 8 is a schematic diagram of computing device 800, which may be used to implement the controller 114 of Figs. 1A-1 C and Fig. 6 and/orthe state machine 700 of Fig. 7. The computing device includes a processing unit 802 and a memory 804 which has stored therein computer-executable instructions 806. The processing unit 802 may include any suitable devices configured to implement the functionality of the controller 114 and state machine 800 such that instructions 806, when executed by the computing device 800 or other programmable apparatus, may cause the functions/acts/steps performed by the controller 1 14 and state machine 800 as described herein to be executed. The processing unit 802 may include, for example, any type of general-purpose microprocessor or microcontroller, a digital signal processing (DSP) processor, an integrated circuit, a field programmable gate array (FPGA), a reconfigurable processor, a programmable read-only memory (PROM), or any combination thereof.

[0097] The memory 804 may include any suitable known or other machine-readable storage medium. The memory 804 may include non-transitory computer readable storage medium, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. The memory 804 may include a suitable combination of any type of computer memory that is located either internally or externally to device, for example random-access memory (RAM), read-only memory (ROM), compact disc read-only memory (CDROM), electro-optical memory, magneto-optical memory, erasable programmable read-only memory (EPROM), and electrically-erasable programmable read-only memory (EEPROM), Ferroelectric RAM (FRAM) or the like. Memory 804 may include any storage means (e.g. devices) suitable for retrievably storing machine-readable instructions 806 executable by the processing unit 802.

[0098] The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure.

[0099] Example - Design and Simulation of a Resonant Power Processor for a Permanent Magnet Synchronous Motor [00100] In this example, an example power circuit has been modeled with Matlab/Simulink. The simulated operating condition is a propeller run-up from stall to 6500 rpm, which is the desired operating speed. The simulation has been performed at a fixed sample time of 10⁶ second and using the Runge-Kutta solver. The simulation parameters are described in Table 2.

[00101 ] Table 2 - Simulation Parameters

[00102] From the simulation results shown in Fig. 9, one can observe that the base speed is achieved around 2000 rpm, where the PMSM torque cannot be achieved due to the increasing Back-EMF. This is expected as below 2700 rpm, the RPP is offline and therefore does not add the capacitors voltages to the PMSM phases. When the RPP is activated, it can be observed that the PMSM torque overshoots the maximum continuous rating of 15.6 N.m. This is due to the FOC PI controller integrators which accumulated the torque error since the torque dropped at 2700 rpm. Once the RPP is activated, the PI controller catch-up and the PMSM torque is maintained at the maximum continuous rating. The capacitance shift from 1 12 mF to 56 mF is smooth from the PMSM point of view. This transition can be observed around t = 3.5 seconds. The proposed system achieves the maximum continuous rated torque over the whole speed range, until the run-up is completed. Once the run-up is completed, the control algorithm proposed in this paper successfully controls the PMSM speed at 6500 rpm and torque at 14 N.m. Looking at Fig. 10, one can observe that the ZDAC control technique is effective throughout the whole speed range. Looking at Fig. 11 , one can observe that the combined inverter and capacitor voltages are sufficient to oppose the Back-EMF and achieve the desired phase current. Looking at Fig. 12, one can observe that the profile of the phase current is sinusoidal with low current harmonics. Table 3 shows the PMSM torque and speed quality in steady state.

[00103] Table 3. PMSM Steady State Torque and Speed Characteristics

[00104] From the simulation results shown in Fig. 13, one can observe that the RPP control algorithm successfully manages the different switches of the RPP to schedule the recharge cycles and discharge cycles. Fig. 13 also shows that the capacitor successfully goes through the recharge and discharge cycles. The PRMS switches are controlled such that only one pair of switches is activated at a time. The CPS switches are controlled such that the capacitor polarity is properly set for the intended usage. Fig. 14 shows the electrical behavior of the Recharge Module, where is can be observed that the control algorithm successfully schedules the recharge cycle of the CCMs by setting RON until the desired amount of energy has been injected in the capacitors. Fig. 15 shows the effectiveness of the energy-based recharge control algorithm, where is can be observed that the recharged capacitor voltage matches the capacitor voltage request, especially when the CCMs are configured to 56 mF.

[00105] This example proposes a PMSM power circuit drive which includes a capacitor based resonant phase voltage booster module, which is often times referred as the resonant power processor (or power circuit, equivalently). The RPP being connected between the VSI and the PMSM, the VSI voltage stresses and losses are not different to what they would be without the RPP. This proposed drive successfully achieves steady state operation of a PMSM driving a propeller at 6500 rpm and 14 N.m. For the given DC link voltage, the RPP allows to increase the power density of the PMSM to 325% of nominal rating, while generating low phase current harmonics. From the simulation results, one can conclude that a functional concept has been developed.

[00106] Various aspects of the systems and methods described herein may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. Although particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects. Although the examples above have been directed to X-phase electric motors, it is intended that the resonant power circuit described herein can be directed to any X-phase electric circuit including, but not limited to, X-phase electric induction heaters, X-phase electric telecom circuits (e.g., high frequency components), and the like. The scope of the following claims should not be limited by the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the description as a whole.

Claims

WHAT IS CLAIMED IS:

1 . A power circuit for powering phases of an X-phase electric circuit, the X-phase electric circuit having a given number X of phases, the power circuit comprising: a recharge module; and a plurality of capacitor circuits operatively connectable to the X-phase electric circuit and to the recharge module, the plurality of ca pa citor circuits including a given number M of capacitor circuits exceeding by at least one the given number X of phases of the X-phase electric circuit such that M > X + 1 ; wherein, during operation of the power circuit, each phase of the X-phase electric circuit is powered by a corresponding one of the plurality of capacitor circuits and at least one excess capacitor circuit is rechargeably connected to the recharge module.

2. The power circuit of claim 1 wherein the X-phase electric circuit is an X-phase electric motor.

3. The power circuit of claim 1 further comprising a resonant circuit including at least one of the plurality of capacitor circuits connected to one of the phases of the X-phase electric circuit, the resonant circuit operated at a resonant frequency thereof.

4. The power circuit of claim 1 wherein the capacitor circuits includes a capacitor; and an H- bridge including two pairs of switches connected between i) the capacitor and ii) selectably at least one of the phases of the X-phase electric circuit and the recharge module, the two pairs of switches operated to control a polarity of the capacitor.

5. The power circuit of claim 1 wherein the given number M of capacitor circuits exceeds the given numberX of phases by more than one, leading to at least two excess capacitor circuits, the recharge module having a plurality of recharge circuits operatively connectable to any of the plurality of capacitor circuits, with at least two of the plurality of recharge circuits being rechargeably connected to corresponding ones of the at least two excess capacitor circuits.

6. The power circuit of claim 5 wherein the capacitor circuit includes: a capacitor; and a pair of discharge switches for each of the given number X of phases of the X-phase electric circuit, the pair of discharge switches operatively connectable to the capacitor and configured to be connectable to any of the phases of the X-phase electric circuit, wherein when operated in a discharge mode, the capacitor discharges in a given phase of the X- phase electric circuit via a given one of the pairs of discharge switches.

7. The power circuit of claim 5 wherein the plurality of recharge circuits includes a given number Y of recharge circuits, the capacitor circuit including: a capacitor; and a pair of recharge switches for each of the given number Y of recharge circuits, the pair of recharge switches operatively connectable to the capacitor and connectable to any of the plurality of recharge circuits, wherein when operated in a recharging mode, the capacitor recharges a given one of the plurality of recharge circuits via a given one of the pairs of recharge switches.

8. The power circuit of claim 1 wherein at least one of the plurality of capacitor circuits has a capacitor; and a polarity switching and disconnect circuit operatively connectable between the capacitor and one of any of the phases of the X-phase electric circuit and the recharge module, the polarity switching and disconnect circuit configured for at least one of switching the polarity of the capacitor, disconnecting the capacitor and bypassing the capacitor.

9. The power circuit of claim 1 wherein the recharge module includes: an inductor; a freewheeling branch including a reverse current protection device; and a power branch including direct-current (DC) power terminals operatively connectable across the inductor and the at least one excess capacitor circuit.

10. The power circuit of claim 1 further comprising a controller communicatively coupled to the plurality of capacitor circuits and to the recharge module, the controller having a processor and a non-transitory memory which has stored thereon instructions that when executed by the processor perform steps for operating the power circuit.

1 1 . The power circuit of claim 10, wherein the steps include: upon determining that one of the capacitor circuits powering one of the phases of the X-phase electric circuit is discharged: disconnecting the one of the capacitor circuits from the one of the phases of the X- phase electric circuit; rechargeably connecting the one of the capacitor circuits to the recharge module; and connecting a recharged one of the plurality of capacitor circuits to the one of the phases of the X-phase electric circuit.

12. The power circuit of claim 11 further comprising: controlling a polarity of the one of the capacitor circuits through a polarity and disconnect circuit such that a positive terminal of the capacitor is connected to an input terminal of the recharge circuit; and controlling a polarity of a recharged one of the plurality of capacitor circuits according to a polarity of the one of the phases of the X-phase electric circuit.

13. The power circuit of claim 12 further comprising, prior to said rechargeably connecting, disconnecting the fully recharged one of the plurality of capacitor circuits from the recharge module.

14. The power circuit of claim 12 wherein the plurality of capacitor circuits are operated in a discharge mode and a recharge mode in an alternating manner.

15. The power circuit of claim 11 wherein the steps include: connecting the given number of capacitor circuits to corresponding ones of the phases of the X-phase electrical circuit and operating said connected capacitor circuits in a discharge mode; and rechargeably connecting the at least one excess capacitor circuit to the recharge module and operating the at least one excess capacitor circuit in a recharge mode.

16. A method of operating a power circuit connected to an X-phase electric circuit, the X- phase electric circuit having a given number X of phases, the power circuit having a plurality of capacitor circuits operatively connectable to the X-phase electric circuit, the method comprising: during operation of the power circuit: powering each phase of the X-phase electric circuit via a corresponding one of the plurality of capacitor circuits, the plurality of capacitor circuits including a given number M of capacitor circuits exceeding by at least one the given number X of phases of the X-phase electric circuit such that M > X + 1 ; and using a recharge module operatively connectable to any one of the plurality of capacitor circuits, recharging at least one excess capacitor circuit.

17. The method of claim 16 further comprising: upon determining that one of the capacitor circuits powering one of the phases of the X-phase electric circuit is discharged: disconnecting the one of the capacitor circuits from the one of the phases of the X- phase electric circuit; rechargeably connecting the one of the capacitor circuits to the recharge module; and connecting a recharged one of the plurality of capacitor circuits to the one of the phases of the X-phase electric circuit.

18. The method of claim 16 further comprising, prior to said rechargeably connecting, rechargeably disconnecting the fully recharged one of the plurality of capacitor circuits from the recharge module.

19. The method of claim 16 further comprising alternating a mode of operation of each of the plurality of capacitor circuits between a discharge mode and a recharge mode.

20. The method of claim 16 wherein when operated in the discharge mode, each capacitor circuits discharges in a given phase of the X-phase electric circuit via a corresponding pair of discharge switches, and when operated in the recharge mode, the recharge module recharges a capacitor of the at least one excess capacitor circuit via a corresponding pair of recharge switches.