RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application No. 63/399,934, filed August 22, 2022.

FIELD OF THE DISCLOSURE

[0002] The present disclosure relates to multiphase drive systems. More particularly, the present disclosure relates to multiphase drive systems comprising multilevel inverters for converting DC power to multiphase AC power.

BACKGROUND

[0003] Conventional motors or other loads may typically be configured to be driven by three-phase Alternating Current (AC) power. Three-phase systems may be adapted for variable speed applications. Three-phase variable speed drive systems have remained popular due to wide off-the-shelf availability of the drive systems. However, multiphase machines with phase numbers of more than three may have advantages over traditional three-phase systems, such as when the system demands higher power.

[0004] Conventional systems may only be operable in a single multiphase and multilevel inverter configuration. It may be desirable to modify a drive system to change the number of phases generated by the drive system and/or other features of the system. Adapting some conventional systems to change the number of phases to accommodate different multiphase load configurations or multilevel conversion may require arduous rewiring, reprogramming, and/or other reconfiguration, or may otherwise require significant redesign of the drive system.

[0005] Multilevel inverters are discussed by B. Nia Roodsari, "Computationally Efficient Space Vector Modulation for Multilevel Inverters and Improved Capacitor Voltage Control" MSc thesis, University of Calgary, Calgary, Canada, May 2012, the entire contents of which are incorporated herein by reference. SUMMARY

[0006] To facilitate utilization and simplification of applications of multilevel- multiphase drives, there is disclosed herein a modular, expandable multiprocessor (microcontroller) based controller.

[0007] According to an aspect, there is provided a multiphase Alternating Current (AC) drive system, comprising: a master controller module; a plurality of drive modules operatively coupled to the master controller module, each drive module comprising a respective multilevel inverter and a respective drive module controller; and wherein the master controller module sends control signalling to the drive module controllers of the drive modules for generating a multiphase AC output, and the drive module controllers control, as a function of the control signalling, the corresponding multilevel inverters to collectively generate the multiphase AC output.

[0008] In some embodiments, each drive module generates a respective at least one phase of the multiphase AC output.

[0009] In some embodiments, for each drive module, the at least one phase of the multiphase AC output comprises two phases of the multiphase AC output.

[0010] In some embodiments, for each drive module, the respective inverter of the drive module individually generates output based on a first number of discrete voltage levels, and each subset of drive modules collectively generates output based on a second number of discrete voltage levels, and the second number is lower than the first number.

[0011] In some embodiments, the inverters of the drive modules comprise 3-level inverters, and the multiphase AC output is generated by 2-level voltage modulation.

[0012] In some embodiments, the drive modules comprise a plurality of subsets of drive modules, each subset of drive modules being controlled by the master controller to generate a respective phase of the multiphase AC output. [0013] In some embodiments, for each drive module, the respective inverter of the drive module individually generates output based on a first number of discrete voltage levels, and each subset of drive modules collectively generates output based on a second number of discrete voltage levels, and the second number is higher than the first number.

[0014] In some embodiments, each subset of drive modules comprises a respective pair of drive modules.

[0015] In some embodiments, the inverters of the drive modules comprise 3-level inverters, and the multiphase AC output is generated by 5-level voltage modulation.

[0016] In some embodiments, the master controller module sends control signaling to each drive module individually.

[0017] In some embodiments, for each subset of drive modules, the drive modules of the subset are connected to the master controller module in series.

[0018] In some embodiments, the master controller module detects a number of the drive modules and controls the drive modules as a function of the detected number of drive modules.

[0019] In some embodiments, the drive modules generate the AC voltage output using at least one of: quasi-square waveform modulation; multicarrier Pulse Width Modulation (PWM); and Space vector modulation.

[0020] In some embodiments, the PWM is level-shifted PWM or phase- shifted PWM.

[0021] According to another aspect, there is provided method of generating a multiphase AC output using the multiphase AC drive system as described herein, comprising: generating, by the master controller module, control signalling for each of the drive modules to control the drive modules to generate the multiphase AC output; sending, by the master controller module, the control signalling to the drive module controllers of the drive modules; and for each drive module, controlling, by the respective drive module controller, the respective inverter as a function of the respective control signalling received by the respective drive module controller, such that the drive modules collectively generate the multiphase AC output.

[0022] In some embodiments, the respective drive module controller controlling the respective inverter comprises generating switching states for the respective inverter as a function of the control signalling.

[0023] In some embodiments, the method further comprises obtaining, by the master controller module, one or more characteristics of the multiphase AC output to be generated, wherein generating the control signalling comprises generating the control signalling as a function of the one or more characteristics of the multiphase AC output to be generated.

[0024] In some embodiments, the one or more characteristics include at least one of: a number of phases of the multiphase AC output to be generated; a phase shift; and a number of discrete voltage levels for modulation by the inverters.

[0025] In some embodiments, obtaining the characteristics of the multiphase AC output comprises determining, by the master controller module, a number of phases of the multiphase AC output as a function of a number of drive modules coupled to the master controller module.

[0026] Other aspects and features of the present disclosure will become apparent to those ordinarily skilled in the art upon review of the following description of the specific embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present disclosure will be better understood having regard to the drawings in which:

[0028] Figure 1A is a functional block diagram of an example modular, multiphase, multilevel AC drive system;

[0029] Figure 1 B is a schematic diagram of example inverter circuitry; [0030] Figure 1 C is a diagram of an example implementation of the system of Figure 1 showing connections between a master controller module drive modules according to some embodiments;

[0031] Figure 2 is a functional block diagram of an example 3-phase, 5-level AC drive system;

[0032] Figure 3 is a functional block diagram of an example 6-phase, 2-level AC drive system;

[0033] Figure 4 is a functional block diagram of an example 6-phase, 3-level AC drive system;

[0034] Figure 5 is a functional block diagram of an example 6-phase, 5-level AC drive system;

[0035] Figure 6 is a functional block diagram of an example 9-phase, 3-level AC drive system;

[0036] Figure 7 is a functional block diagram of an example 9-phase, 5-level AC drive system;

[0037] Figure 8A is a schematic diagram of an example 3-level drive module;

[0038] Figure 8B is a schematic diagram of an example 5-level drive module;

[0039] Figure 9 is a schematic diagram of an example m-phase inverter connected to an example m-phase machine;

[0040] Figures 10 to 12 illustrate example inverter and drive circuitry configurations;

[0041] Figure 13 is a flowchart of an example method according to some embodiments; [0042] Figure 14 is a functional block diagram of a drive module according to some embodiments; and

[0043] Figure 15 is a functional block diagram of a master controller module according to some embodiments.

DETAILED DESCRIPTION

[0044] Multi-phase loads (e.g., motors) having more than three phases may be beneficial or advantageous for some applications. Multi-phase AC drive systems capable of more than three phases may be used to drive such loads. Increasing the number of phases may be a promising method to increase the system's power rating. Therefore, multiphase machines with phase numbers of more than three may be preferred when the system demands higher power. In the following disclosure, like reference numbers denote like or elements.

[0045] An m-level inverter creates a modulated voltage based on “m” discrete voltage levels, where the modulation as averaged over time provides AC power output from the inverter. The m-level inverter may comprise a plurality of switches that are controllable to generate modulated output using the “m” different voltage levels voltage(s).

[0046] Figure 1 A is a block diagram of an example modular, multiphase, AC multilevel drive system 100 (which may simply be referred to as a “modular drive system” herein). The modular drive system 100 described herein may be an expandable variable speed drive system that converts DC voltage to an AC voltage to drive one or more multiphase loads. The modular drive system 100 comprises a “master” controller module 102 (or “master controller module”) and a plurality of “slave” drive modules 104 operatively coupled to the master controller module 102. Each drive module 104 comprises respective inverter and drive circuitry 106 and a drive module controller 108. The inverter and drive circuitry 106 may collectively be referred to simply as “inverter” 106 herein.

[0047] The inverters 106 may each be 3-level IGBT inverters, although embodiments are not limited to a particular type of inverter circuitry. Additionally, other multilevel configurations (e.g., 2-level, 5-level, 7-level, and so on) may be used in the individual drive modules 104 in other embodiments.

[0048] The drive modules 104 are coupled to the master controller module 102 via connection 105. The connection 105 may include a serial bus, digital connections, and/or analog connections, for example, although embodiments are not limited to a particular connection type. By way of example, the drive modules 104a to 104f may communicate with the master controller module 102 based on a serial communication protocol. Alternatively, as in examples described below, an analog connection having variable voltage levels may be used to communicate between the master controller module 102 and the drive modules.

[0049] The modular drive system 100 in this example is configured to generate a 3-phase, 3-level AC output to a multiphase load 110. The multiphase load 110 shown in Figure 1 is connected to, but external to the modular drive system 100. The multiphase load 110 may be a multiphase motor, for example, and the 3-phase, 3-level AC output may be provided to windings of the motor.

[0050] The modular drive system 100 includes three drive modules 104a to 104c. The inverters 106 are 3-level inverters in this example. The drive module controller 108 of each drive module 104a to 104c is coupled to the corresponding inverter 106 and to the master controller module 102. The inverters 106 receive DC voltage from one or more DC voltage sources and modulate the DC voltage to generate an AC voltage. The DC voltage source(s) may include any suitable source. By way of example, the one or more DC voltage sources may include one or more thermovoltaic arrays (such as shown in Figures 8A and 8B).

[0051] The master controller module 102 may control the drive modules 104a to 104c to each generate a respective phase of 3-phase AC drive output. For example, the master controller module 102 may generate control signals for each drive module 104a to 104c. Each drive module controller 108 may, in turn, control the corresponding 3-level inverter 106 to output one phase of the AC drive output.

[0052] Figure 1 B is a schematic diagram of example 3-level inverter circuitry 150 that receives DC voltage from DV voltage source Vdc. The inverter circuitry 150 includes switches Sa1 , Sa2, Sal , and Sa2. The inverters 106 of Figure 1A may each include the circuitry 150 shown in Figure 1 B, although embodiments are not limited to this configuration. With the four switches (Sa1 , Sa2, Sal , and Sa2), three different discrete voltage levels can be generated.

[0053] Turning again to Figure 1A, the master controller module 102 is coupled to each drive module 104 and is operable to communicate with the drive module controllers 108 thereof. The master controller module 102 may generate and calculate normalized output voltage levels and corresponding time intervals for each of the phases to be generated by the drive modules 104. For example, the master controller module 102 may generate, for each drive module 104, respective control signalling. The control signaling may indicate inverter voltage levels and/or time intervals for example. Each “slave” drive module controller 108 receives the respective control signalling and generates corresponding switching states for the corresponding inverter 106 to generate the voltage levels over the time intervals set by the master controller module 102.

[0054] As an example, for the 3-level system of Figure 1 , the master controller module 102 may calculate that the voltage levels for a first phase, referred to herein as “phase ‘A’”, should have a first voltage level (e.g. “level 1” corresponding to a set positive voltage) from 1 microsecond to 10 microseconds and a second voltage level (e.g. “level 0” corresponding to 0 V) from 10 to 20 microseconds. “Slave” drive module controller 108 of the first drive module 104a responsible for phase “A” may then set switching states of the corresponding inverter 106. In the above example, the inverter 106 of the drive module 104 may include insulated-gate bipolar transistors (IGBT) switches Sa1 , Sa2, Sal , and Sa2 shown in Figure 1 B. The drive module controller 108 may generate voltage level 1 by setting switches Sa1 and ~Sa2 closed and setting switches Sal and Sa2 open from 1 to 10 microseconds. To generate voltage level 0, the drive module controller 108 may set switches Sa1 and Sa2 closed and set switches Sal and ~Sa2 open from 10 to 20 microseconds. These switching states may be set accordingly by the “slave” drive module controller 108 responsive to the control signalling from the master controller module 102. The drive module controller 108 may be programmed to control the inverter 106 switching states as a function of the control input received from the master controller module 102.

[0055] Each drive module 104 may set the switching states of switches of the inverter 106 as a function of the control signalling received from the master controller module 102. For an analog connection between the master controller module 102 and the drive module 104, the voltage level an analog pin of the drive module 104 connected to the master controller module 102 may have multiple possible values, with each possible voltage value of the analog signal corresponding to a different desired inverter voltage output level.

[0056] Figure 1C illustrates example pin connections between the master controller module 102 and drive modules 104a to 104c. The master controller module 102 includes “n” analog output pins (Ao1 , Ao2, Ao3, ... Aon). Each drive module 104a to 104c has a respective analog input pin (Ai1 , Ai2, Ai3) connected to a corresponding Analog output pin (Ao1 , Ao2, Ao3) of the master controller module 102. This system 100 may be expanded by adding drive modules up to a total of “n” drive modules 104. Figure 1C also illustrates example pin connections between the drive module controller 108 and the inverter 106. Specifically, each drive module includes switch control pins “a”, “b”, “c” and “d”, which are connected to inverter switches Sa1 , Sa2, Sal , and Sa2 respectively. An example of how an analog connection may be used for control signalling from the master controller module 102 to drive modules 104 is described below.

[0057] The master controller model 102 may use one analog output pin to communicate with each drive module 104. As an example, for a single phase, the master controller module 102 may determine the following switching states to be followed by the drive module 104a in a sequence to generate the modulated output for its phase:

[0058] In the table above, the “Com Pin Analog Voltage Level” indicates which analog voltage level (of a discrete set of possible levels) of the control signaling from the master controller module 102. In this example, the desired output of the 3-level inverter 106 of drive module 104a follows this pattern: 0 V for 0.12 milliseconds, positive voltage for 0.22 milliseconds, negative voltage for 0.18 milliseconds, and back to 0 V zero for 0.15 milliseconds. Thus, the master controller module 102 may set its analog output pin Ao1 to voltage levels 1 , 2, 0, and 1 for 0.12, 0.22, 0.18, and 0.15 milliseconds, respectively.

[0059] The drive module controller 108 may monitor the voltage on the analog connection to the master controller module 102. Based on the state of this analog input pin Ai1 , the drive module controller 108 may generate four different sets of switching states. Consider “step 1” where the master controller module 102 sets the analog pin Ao1 to level 1 for 0.12 milliseconds. In response, the drive module 104a may set the four output pins: “a”, “b”, “c” and “d”. Specifically, pins “a”, “b”, “c” and “d” may be set to low, high, low, and high logic levels, respectively, for a duration of 0.12 milliseconds. When the master controller module 102 changes the voltage level of the analog connection to the drive module 104 for steps 2, 3, 4 and so on, the drive module 104 monitors this change and adjusts the four switching states accordingly. [0060] The master controller module 102 may also calculate or otherwise determine phase separation as a function of the number of phases. Consider, as another example, a 5-phase system in which five phases “A”, “B”, “C”, “D” and “E” are separated by 72-degree increments. Thus, a voltage level for phase “B” lags a voltage level of phase “A” by 72 degrees. The master controller module 102 may control the “slave” drive module controller 108 of the drive module 104 generating phase “B” may to this phase shift.

[0061] The modular drive system 100 in Figures 1A and 1C is modular in that the master controller module 102 may operate with variable numbers of drive modules 104 in various configurations based on a desired number of phases and/or number of DC voltage levels used to generate the AC output. For example, additional drive modules 104 may be added to the system to support more than three phases. Drive modules may be added and/or removed from the modular drive system 100 depending on the desired number of phases and/or voltage levels. Thus, the system may be configured to support various multiphase load configurations.

[0062] In some embodiments, the modular drive system 100 may operate in at least two modes. In an “initialization” mode, the drive module controllers 108 may send information to the master controller module 102, and the master controller module 102 may count the number of phases based on the input received from the drive modules 104. The modular drive system 100 may enter this initialization mode upon startup, for example.

[0063] In an “operating” mode (after the initialization mode is complete), the master controller module 102 may send instructions to the drive module controllers 108. Specifically, the master controller module 102 may send the control signalling indicating the required switching states to each drive module 104. The drive modules each follow their respective instructions from the master controller module to collectively generate the AC output.

[0064] The master controller module 102 may comprise a “master” processor and memory. The memory may store computer executable instructions thereon that, when executed cause the master processor to implement functionality of the master controller module 102 descried herein. The processor and memory may collectively be in the form of a microcontroller, for example. The drive module controllers 108 may likewise comprise a “slave” processor and memory. Each memory may store computer executable instructions thereon that, when executed cause the corresponding slave processor to implement functionality of the dive module controller 108 descried herein. The slave processor and memory may collectively be in the form of a microcontroller, for example. Embodiments are not limited to a particular hardware and/or software implementation of the master controller module 102 and the drive module controllers 108.

[0065] The connections between modules may include a simple wired connection, such as one wire for an analog pin connection, or one or more wires when for a digital pin connection. Take, for example, a 5-phase 3-level system using an analog pin connection, the master controller module 102 may use 5 analog pins for communication, with one analog pin for each drive module 104. For digital pin connections, the master controller module 102 may include 10 pins for communication with the drive modules 104, with each drive modules 104 using two pins for the respective connection. In some embodiments, the drive modules 104 may communicate with each other via optional communication links between the modules 104. The links may be simple wired connections, for example.

[0066] As also noted above, the modular drive system 100 is modular and expandable in that additional drive modules 104 may be added for more than 3- phase or more than 3-level multiphase drive configurations. The number and configuration of drive modules 104 may be selected to generate a multiphase output having a desired number of phases (e.g., 3-phase, 4-phase, 5-phase, etc.). The drive modules 104 may also be configurable for multiple different DC voltage level configurations (e.g., 3-level, 5-level, etc.). Additional drive modules 104 to form other configurations shown in Figures 2 to 7 and descried below for example.

[0067] The master controller module 102 may be coupled with “nxm” drive modules (such as drive modules 104 in Figure 1 ), where “m” is equal to the number of phases and “2xn+1” is the number of discrete voltage levels used to generate the AC drive output. The number of voltage levels may be referred to as the “level” system.

[0068] For the three-phase, three-level modular system 100 shown in Figure 1 : number of voltage level — 1 n = - = 1

2

[0069] Thus, one “master” controller module 102 and three “slave” drive modules 104 may be used, as shown in the system of Figure 1. A 9-phase, five- level voltage drive system, on the other hand, may comprise one “master” controller module 102 and 18 “slave” drive modules 104. An example system 700 with this configuration is shown in Figure 7, which will be described in more detail below.

[0070] Generally, a typical three phase motor with 2m stator slots may be converted to an m-phase (multiphase) motor with concentrated winding. Based on the proposed structure, one “master” controller module 102, and m “slave” drive modules may be used to build an m-phase, 3-level AC drive system, and 2m drive modules may be used to build an m-phase, 5-level AC drive system.

[0071] In some embodiments, the drive modules 104 are arranged one or more subsets, each subset including one, two or more drive modules 104 that collectively generate a phase of the AC voltage output of the system. For example, each subset may include two drive modules, although embodiments are not limited to pairs. For m-level inverters (i.e., inverters generating output based on a “m” discrete voltage levels), each subset of one or more drive modules may collectively generates n-level modulated output (i.e. based on “n” of discrete voltage levels). The “n” level modulation may be more than m-level (e.g. 3-level inverters arranged to generate 5-level modulated output). Alternatively, the “n” level modulation may be less than m-level (e.g. 3-level inverters arranged to generate 2-level modulated output). [0072] Figure 2 is a block diagram of an example 3-phase, 5-level AC drive system 200. The system 200 comprises the “master” controller module 102 and six “slave” drive modules 104 operatively coupled to the master controller module 102. Each drive module 104 comprises a respective 3-level inverter 106 and respective drive module controller 108.

[0073] The drive modules 104 are arranged in pairs (105a to 105c), and each pair is configured to collectively provide a respective phase of the AC drive output. Specifically, a first pair 105a of drive modules 104a and 104b collectively output a first phase of the 3-phase AC drive output, based on five DC voltage levels. The combination of two 3-level inverters 106 may thereby collectively function as a 5-level inverter. A second pair 105b of drive modules 104c and 104d and a third pair 105c of drive modules 104e and 104f generate the second and third phases respectively. The three pairs of drive modules 104 may thereby be controlled by the master controller module 102 to generate a 3-phase, 5-level AC output, including phases A, B and C, to example multiphase load 210.

[0074] The drive modules 104 may each be individually coupled to the master controller module 102 (essentially in parallel), as shown in Figure 2. Thus, the master controller module 102 may communicate directly and individually with each drive module 104. In other embodiments the drive modules 104 of each subset (e.g., pair) of drive modules 104 may be connected in series to the master controller module 102. That is, for each subset, one drive module 104 may receive signalling from the master controller module 102 and then send control signalling to the next drive module 104 connected in series. Optionally, one drive module 104 may include a plurality of inverters 106 coupled to a single drive module controller 108. See, for example, the example of Figure 8B described below.

[0075] The master controller module 102 may output control signalling or data messaging to the drive module controller 108 of each drive module 104a to 104f . The master controller module 102 may individually control each drive module 104a to 104f so that the drive modules 104 collectively generate the desired 3- phase AC drive output as a function of five DC voltage levels. Based at least in part on the output received from the master controller module 102, each drive module may apply respective inverter switching states. The inverter switching states for each drive module 104 may, for example, be calculated based on various factors including, but not limited to: the number of phases, number of DC voltage levels, AC frequency, and other parameters or variables received from the master controller modules 102.

[0076] Figure 3 is a block diagram of an example 6-phase, 2-level AC drive system 300. The system 300 comprises the “master” controller module 102 and three “slave” drive modules 104a to 104c, each with a respective 3-level inverter 106 and drive module controller 108. In this example, the drive modules 104 are controlled by the master controller module 102 to generate a 6-phase, 2-level AC output to example multiphase load 310, including phases A, B, C, D, E and F. As shown in Figure 3, each drive module 104 generates two phases of the 6-phase AC output. A 3-level inverter can produce two phases, each produce by 2-level modulation. That is, a single 3-level inverter can generate two 2-level phases of the AC output.

[0077] Figure 4 is a block diagram of an example modular system 400 configured to generate a 6-phase, 3-level AC output. The AC output is shown delivered to multiphase load 410 in this example. The system 400 comprises a “master” controller module 102 and six “slave” drive modules 104, each with a respective 3-level inverter 106 and drive module controller 108. Each drive module 104 is controlled by the master controller module 102 to generate a respective phase (A, B, C, D, E or F) of the 6-phase AC output.

[0078] Figure 5 is a block diagram of an example modular system 500 configured to generate a 6-phase, 5-level AC output. The AC output is shown delivered to multiphase load 510 in this example. The system 500 comprises the “master” controller module 102 and 12 “slave” drive modules 104, each with a respective 3-level inverter 106 and drive module controller 108. Similar to the system 200 in Figure 2, the system 500 of Figure 5 has drive modules 104 coupled to the master controller module 102 and arranged as pairs. Each pair is configured to collectively function as a 5-level inverter that generates a respective phase of the 6-phase AC drive output. [0079] The system 400 of Figure 4 may be converted to the system 500 of Figure 5 (generating a 6-phase, 5-level AC output) by adding six drive modules 104. The output connections from the inverters 106 may be rewired to the multiphase load 510. It should be highlighted that this 5-level inverter may be utilized with a 6-phase motor with distributed (more than 1 wire per phase) windings. Optionally, the drive modules 104 may be used to generate 2-level output voltage, in which each drive module 104 may be connected to two motor phases.

[0080] Figure 6 is a block diagram of an example modular system 600 configured to generate a 9-phase, 3-level AC output to multiphase load 610. The system 600 comprises a master controller module 102 and nine drive modules 104, each with a respective 3-level inverter 106 and drive module controller 108. The drive modules 104 are each coupled to the master controller module 102, with each drive module 104 generating a respective phase of the 9-phase AC output.

[0081] Figure 7 is a block diagram of an example modular system 700 configured to generate a 9-phase, 5-level AC output to multiphase load 710. The system includes 18 drive modules 108. Similar to the systems 200 and 500 of Figures 2 and 5, the drive modules 104 are arranged into pairs. The 18 drive modules are arranged as nine pairs in this example. Each pair is configured to collectively function as a 5-level inverter that generates a respective phase of the 9-phase AC drive output.

[0082] A user may connect a number of “slave” drive modules 104 to a “master” controller module according to a desired configuration (e.g. number of phases and DC voltage levels). The systems described above may further include a user interface coupled to the master controller module 102. The user may input one or more operation parameters to the master controller module 102. The operation parameters may comprise, for example, AC frequency, number of voltage levels, and/or other parameters or variables. In some embodiments, the master controller module 102 may automatically detect the number of drive modules and/or connected phases. The master controller module 102 may calculate initial variables for each drive module 104. The variables may be communicated from the master controller module 102 to corresponding individual drive modules 104. Each drive module 104 then sets respective multilevel inverter switching states as a function of the corresponding control signalling received from the master controller module 102. The multilevel inverter switching states control switches of the inverter 106 to generate AC drive output.

[0083] Figure 8A is a diagram of an example system 800 including drive module 804 coupled to a thermovoltaic (TV) array DC voltage source 809 and motor phase winding 810. The TV array DC voltage source provides DC power to the drive module 804, and the drive module 804 converts the DC power to AC power that is delivered to the motor phase winding 810. The modular drive systems 100 to 700 shown herein may be suited for use with such thermovoltaic voltage sources. The drive module includes a drive module controller 808 and an example implementation of a 3-level inverter 806. For clarity, the motor phase winding 810 is not part of the inverter 806. The drive modules 804 shown in Figures 1 to 7 may be in the form of the example drive module 804 shown in Figure 8A, although embodiments are not limited to this example.

[0084] The inverter 806 in this example comprises four IGBT switches 802a to 802d and four opto-isolator circuits 804a to 804d. The IGBT switches 802a to 802d are arranged in an inverter configuration, and each IGBT switch 802a to 802d is coupled to a respective one of the opto-isolator circuits 804a to 804d. The switching states generated by the drive module controller 108 may, for example, be used to control the IGBT switches 802a to 802d via opto-isolator circuits 804a to 804d. In Figure 8A, the example circuitry of the inverter 806 block is in the form shown in Southern Alberta Institute of Technology (SAIT), Power Electronics, "Lab 11 : Microcontroller Applications in Power Electronic" (2018), the entire content of which is incorporated herein by reference. However, the particular circuitry of the inverter 806 may vary, and embodiments are not limited to this example circuitry of the inverter 806.

[0085] In some embodiments, a drive module may include more than one inverter. By way of example, a drive module may include two 3-level inverters similar to the inverters 106 shown in Figures 1 to 7. [0086] Figure 8B is a schematic diagram of an example drive module 854, in which two 3-level inverters 856a and 856b (each similar to the inverter 806 in Figure 8a) is connected to the drive module controller 858. The drive module controller 858 may comprise circuitry (e.g. microprocessor) having sufficient inputs to connect two or more inverters 856a and 856b in this fashion to function collectively as a 5-level inverter module. Each inverter 106 is shown connected to a respective TV array (809a, 809b) as a DC power source. In other embodiments, the same DC power source (e.g. a single TV array) may be connected to both inverters. In still other embodiments, the drive module may include more than two inverters may be connected to a single drive module controller.

[0087] The drive modules described herein may, for example, generate or set switching states for at least one of the following DC to AC modulation methods: quasi-square waveform modulation; and/or multicarrier Pulse Width Modulation (PWM), such as level-shifted PWM or phase-shifted PWM; and/or Space vector modulation, to name a few examples. These modulation methods for AC generation may have relatively low computational burden appropriate for the drive modules 104 described herein. Embodiments are not limited to a particular DC to AC modulation method. The drive module controllers 108 may only need to perform a few simple tasks to generate appropriate switching states for each inverter 106 connected to a typical phase. These simple tasks may be performed by a simple and inexpensive processor (i.e. microcontroller). The master controller module 102 on the other hand may handle more computationally intensive tasks, such as, fast communication methods, optional sensor control functions (e.g., temperature, current, and/or vibration sensors), and reinitializing all drive module controllers 108. In The master controller module 102 may also set timing and manage synchronization between phases.

[0088] The modular AC drive systems described herein may provide one or more of the following advantages. The modular design may be customized for use with rotating machines having various numbers of phases. The modular design may be configured to have an inverter system with 2, 3, 5, 7 or 9 levels (or more). For higher levels (e.g., 7, 9, etc.), the master controller module’s processor’s functions may be modified to support the higher levels. The drive modules may each function similar to a computer “plug-and-play” device, meaning that the required phase shift may be calculated automatically with increasing the slave modules as an initial variable for each inverter. If the number of desired phases is changed, rather than modifying and designing an entire new inverter system, the drive system may be modified by adding additional drive modules. The drive modules may be programmed to generate quasi-square voltage, PWM such as level-shifted PWM or phase-shifted PWM, and/or Space vector modulation voltage. Speed sensor output may be monitored by the master processor, and a frequency adjustment signal may be sent to reduce the speed error. For example, the system may monitor motor speed and adjust the drive frequency to have the desired speed. Cost of production and maintenance of the modular system described herein may be much lower than conventional inverter systems. The modular system described herein may be powered by a few battery banks (electric car), a few PV modules, and/or with TV arrays. The drive modules may be programed to change the number of motor phases and poles electronically. Fault tolerant capability may be added to the system, when faults occur slave modules will be reinitialized by master processor to work with m-1 phases.

[0089] Figure 9 is a schematic diagram of an example m-phase inverter 900 connected to an example m-phase machine 902 having “n” windings (w1 , w2, .... wn). Voltage source Vdc provides DC power to the inverter, which is converted to m-phase AC power for the m-phase machine.

[0090] Figure 10 is a schematic of an example modular drive system 100 including a multiphase full bridge inverter 1001 with one DC source 1002. The DC source 1002 may be a TV array, for example. The inverter 1000 includes a plurality of full inverter bridges 1004a to 1004c. For use with one DC source 1002, each full bridge (1004a, 1004b, 1004c) may be connected to a respective one typical phase winding (not shown) and windings may not have any star point connection.

[0091] Figure 11 shows another example multiphase full bridge inverter 1100 with one DC source 1102. The example of Figure 11 is similar to Figure 10, but also shows a buck or boost converter 1104 to adjust the DC voltage amplitude. Using buck or boost converter 1104 may be helpful to set the drive output voltage level when we are using a simple modulation method similar to quasi-square waveform modulation.

[0092] Figure 12 shows a full bridge 1200 of an inverter with one voltage source 1202. If there are sufficient DC voltage source(s) available, configurations similar to the example of Figures 10 to 12 may be used for higher numbers of phases. With help of buck-boost converter amplitude of the DC may be adjustable. For example, with enough DC voltage sources and a DC to DC boost converter, separate DC voltage sources (e.g. separate TV arrays) may be used for each phase.

[0093] The inverters discussed herein may have various multilevel inverter topologies, including but not limited to: Diode Clamped inverter; Active Diode clamped inverter; Flying capacitor inverter; Stacked Multi-cell inverter; and Cascaded H-bridge inverter.

[0094] Figure 13 is a flowchart of an example method that may be performed by the modular drive systems described herein (e.g. with reference to Figures 1 to 7).

[0095] At block 1302, the master controller module generates control signalling for each of the drive modules to control the drive modules to generate a multiphase AC output. Prior to generating the control signalling, the master controller module may obtain one or more characteristics of the multiphase AC output to be generated, which may include but are not limited to: a number of phases of the multiphase AC output to be generated; a phase shift; timing; and/or a number of discrete voltage levels for modulation by the inverters. Obtaining the characteristics may include automatically determining one or more of the characteristics as described above. By way of example, obtaining the characteristics may include determining, by the master controller module, a number of phases of the multiphase AC output as a function of a number of drive modules coupled to the master controller module. Obtaining the characteristics may include receiving input indicating the one or more characteristics (e.g., from a user or from another device). Generating the control signalling in block 1302 may comprise generating the control signalling as a function of the characteristics of the multiphase AC output to be generated.

[0096] At block 1304, the master controller module sends the control signalling to the drive module controllers of the drive modules.

[0097] At block 1306, for each drive module, the respective drive module controller controls the respective inverter as a function of the respective control signalling received by the drive module such that the drive modules collectively generate the multiphase AC output. This step may comprise determining or setting switching states for the respective inverter as a function of the control signalling, as described herein.

[0098] Figure 14 is a functional block diagram of an example drive module 1400 according to some embodiments. The drive modules (104, 804, 854) of Figures 1 to 8B described above may have the form of the drive module 1400 shown in Figure 14. The drive module 1400 includes an inverter 1406 and a drive module controller 1408. The drive module controller 1408 includes processor 1402 and memory 1404. The memory 1404 stores processor-executable instructions thereon that, when executed by processor 1402, may cause the processor to perform operations of the example drive module controllers (108, 808, 858) described above with reference to Figures 1 to 8B and/or 13. Embodiments are not limited to this particular hardware arrangement.

[0099] Optionally, the drive module 1400 may include one or more sensors to measure one or more characteristics such as electrical current, temperature, motor speed, and/or other characteristics.

[00100] Figure 15 is a functional block diagram of an example master controller module 1500 according to some embodiments. The master controller module 102 of Figures 1 to 7 described above may have the form of the master controller module 1500 shown in Figure 15. The master controller module 1500 includes processor 1502 and memory 1504. The memory 1504 stores processorexecutable instructions thereon that, when executed by processor 1502, may cause the processor to perform operations of the example master controller module 102 described above with reference to Figures 1 to 7 and/or 13. The master controller module 1500 also includes pins or other interface hardware for connecting with the drive modules or is otherwise operable for connection to the drive module(s). Optionally, the master controller module 1500 may include one or more sensors (not shown) to measure one or more characteristics. The master controller module may include other elements such as a user interface and/or hardware for communication with external devices.

[00101] Referring to Figures 14 and 15, a system including the master controller module 1500 and one or more drive modules 1400 may adapt to a fault condition detected by a sensor. As an example, the drive module controller 1408 may receive data from the sensor(s) 1410 and may communicate condition information to the master controller module 1500. For example, if the measured characteristics are outside of set parameters or thresholds, then the drive module controller 1408 may inform the master controller module 1500 of a fault condition. When the master controller module 1500 receives the fault condition report, the master controller module 1500 may reconfigure the system. For example, the master controller module 1500 may remove the faulty phase drive module 1400 from operation and/or recalculate the switching states and time based on the fault condition and/or remaining drive modules.

[00102] It is to be understood that a combination of more than one of the embodiments described above may be implemented. Embodiments are not limited to any particular one or more of the approaches, methods or apparatuses disclosed herein. One skilled in the art will appreciate that variations, alterations of the embodiments described herein may be made in various implementations without departing from the scope of the claims.