System and method for determining and utilizing time constant of variable frequency drive

Abstract

A variable frequency drive system (400) includes a power converter (410) having a plurality of power cells that power one or more output phases, each power cell having a plurality of switching devices, a plurality of sensors (420) that monitor values of the power converter, and a control system (430) in communication with the power converter (410) and controlling operation of the plurality of power cells, wherein the control system (430) is configured by computer executable instructions to access and utilize a multidimensional response surface (RS) (440) to obtain an internal coolant flow.

Description

Technical Field

[0001] Various aspects of this disclosure relate to a variable frequency drive, also known as a VFD, which is powered by a motor to drive a load such as a pump, compressor, fan, or reciprocating compressor system. Throughout the specification, the terms “drive,” “drive system,” “multilevel power converter,” “converter,” “power supply,” and “variable frequency drive (VFD)” are used interchangeably. Background Technology

[0002] Examples of variable frequency drives include medium-voltage (MV) variable frequency drives, such as multilevel power converters, which are used in medium-voltage AC drives, flexible AC delivery systems (FACTS), and high-voltage DC (HVDC) delivery systems, because a single power semiconductor device is not suitable for high voltage. Multilevel power converters typically comprise multiple power units for each phase, each power unit including an inverter circuit with semiconductor switches that can change the voltage output of the individual unit. An example of a multilevel power converter is a cascaded H-bridge converter system with multiple H-bridge units, such as that described in U.S. Patent No. 5,625,545 to Hammond. However, it should be noted that the systems and methods described herein can be applied to any drive system / converter, including but not limited to low-voltage or medium-voltage converters, and for single-converter or multi-converter systems. Summary of the Invention

[0003] Various aspects of this disclosure generally relate to a variable frequency drive, and to determining and utilizing the time constants of one or more components or devices of the variable frequency drive. The methods disclosed herein can be used to evaluate various selected elements (outputs) in a drive system, such as power unit outputs (temperature), power transformer winding temperatures, and motor outputs of interest, such as winding temperatures.

[0004] A first aspect of this disclosure provides a variable frequency drive (VFD) comprising: a power converter including a plurality of power units supplying power to one or more output phases, each power unit including a plurality of switching devices; a plurality of sensors monitoring values ​​of the power converter; a control system communicating with the power converter and controlling the operation of the plurality of power units; and a memory storing one or more time constants, wherein the control system is configured by computer-executable instructions to use the time constants to determine transient temperature behavior.

[0005] A second aspect of this disclosure provides a method for determining and utilizing a time constant associated with a variable frequency drive (VFD), the method comprising creating a transient waveform of a device for the VFD by operating at least one processor, extracting the time constant from the transient waveform, and storing the time constant and a multidimensional RS in the memory of the VFD. Attached Figure Description

[0006] Figure 1 A block diagram of an example multi-unit power supply according to an exemplary embodiment of the present disclosure is shown.

[0007] Figure 2A An exemplary embodiment according to this disclosure is shown. Figure 1 A block diagram of an example power supply circuit with multiple units.

[0008] Figure 2B An exemplary embodiment according to this disclosure is shown. Figure 1 A block diagram of an alternative power supply circuit for a multi-unit power supply.

[0009] Figure 2C An exemplary embodiment according to this disclosure is shown. Figure 1 A block diagram of another alternative example of a multi-unit power supply circuit.

[0010] Figure 3A An exemplary embodiment according to this disclosure is shown. Figure 1 Example current sensor circuit and power unit block diagram of a multi-unit power supply.

[0011] Figure 3B An exemplary embodiment according to this disclosure is shown. Figure 1 Block diagram of an alternative example of a multi-unit power supply: a current sensor circuit and a power unit.

[0012] Figure 4 A simplified block diagram of a power supply associated with a response surface (RS) according to an exemplary embodiment of the present disclosure is shown.

[0013] Figure 5 A graph showing a time constant associated with the transformer windings of a frequency converter driver, according to an exemplary embodiment of the present disclosure, is illustrated.

[0014] Figure 6 The housing of a power supply including a cooling device according to an exemplary embodiment of the present disclosure is shown, and Figure 7 Showing Figure 6 The outer shell, in which the individual doors and panels were removed.

[0015] Figure 8 A flowchart illustrating a method for controlling power supplies associated with the response surface (RS) according to embodiments of the present disclosure is shown. Detailed Implementation

[0016] To facilitate understanding of the embodiments, principles, and features of this disclosure, they will be explained below with reference to implementations in illustrative embodiments. Specifically, they are described in the context of systems and methods for determining and utilizing time constants associated with VFD.

[0017] The components and materials that constitute the various embodiments described below are intended to be illustrative and not limiting. Many suitable components and materials that will perform the same or similar functions as the materials described herein are intended to be covered within the scope of the embodiments of this disclosure.

[0018] refer to Figure 1 An exemplary multi-unit power supply 100a includes a transformer 14, a power supply circuit (also referred to herein as a power converter) 160, a controller 18, and feedback resistors R1 and R2. Power supply 100a provides output power to a load 12.

[0019] Now for reference Figure 2A An example embodiment of a power supply circuit 160 is described. The power supply circuit 160a includes nine power units 16a1, 16b1, ..., 16c3, which are coupled to a transformer 14 (not shown to avoid obscuring the figures) and coupled to a controller 18 via a communication link. Those skilled in the art will understand that more or fewer than nine power units 16a1, 16b1, ..., 16c3 may be used.

[0020] Each output phase of the power supply circuit 160a is fed by a set of power units 16a1, 16b1, ..., 16c3 connected in series. Power units 16a1, 16a2, and 16a3 are coupled in the first phase group, power units 16b1, 16b2, and 16b3 are coupled in the second phase group, and power units 16c1, 16c2, and 16c3 are coupled in the third phase group, wherein the three phase groups are connected in a WYE manner at reference node 42. Those skilled in the art will understand that more or fewer than three output phases can be used.

[0021] The power supply circuit 160a also includes a current sensing circuit 40 coupled to current sensors 20b1 and 20c1, power unit 16c1, controller 18, and reference node 42. Current sensors 20b1 and 20c1 can be conventional current sensors. Current sensors 20b1 and 20c1 are adjacent reference nodes 42, and each current sensor has a power supply terminal p and provides a measurement output signal at an output terminal m.

[0022] Now for reference Figure 3AExample current sensor circuit 40 is described. Current sensor circuit 40 includes a power supply 44, a processor 46, and a fiber optic interface 48. Power supply 44 contains a first input signal coupled to one or more phases of the three-phase input of power unit 16c1 and a second input signal coupled to reference node 42, and provides power (e.g., +15 VDC) to the power supply terminals p of current sensors 20b1 and 20c1. Power supply 44 can be any conventional AC-DC converter or other similar power source.

[0023] Processor 46 has input terminals coupled to the output terminals m of current sensors 20b1 and 20c1, and output terminals coupled to fiber optic interface 48. Processor 46 provides the measured output signals from current sensors 20b1 and 20c1 to controller 18 via fiber optic interface 48. Processor 46 may be a microprocessor, a programmable gate array device (such as an FPGA) configured to perform processor functions, an op-amp-based circuit with a V / f converter for transmitting sensed feedback via fiber optic cable, or other similar processors or circuits. Fiber optic interface 48 is coupled between processor 46 and controller 18 and provides electrical isolation between current sensor circuit 40 and controller 18.

[0024] Power unit 16c1 can be a conventional power unit comprising rectifier 50, DC bus capacitor 52, inverter 54, processor 56, and fiber optic interface 58. Rectifier 50 converts the three-phase input AC signal into a substantially constant DC voltage coupled to DC bus capacitor 52. Inverter 54 converts the DC voltage across DC bus capacitor 52 into an AC output.

[0025] Rectifier 50, DC bus capacitor 52, and inverter 54 share a common floating ground node. The first output terminal of power unit 16c1 is coupled to reference node (WYE connection) 42, and the second output terminal of power unit 16c1 is coupled to power unit 16c2. Processor 56 can be coupled to controller 18 via fiber optic interface 58. Processor 56 can transmit status information about power unit 16c1 to controller 18, and controller 18 can transmit control signals to processor 56 to control the operation of power unit 16c1.

[0026] Current sensor 20b1 is coupled between the first output terminal of power unit 16b1 and reference node 42, current sensor 20c1 is coupled between the first output terminal of power unit 16c1 and reference node 42, and power supply 44 is coupled to reference node 42. This balances the isolation voltage stress on current sensors 20b1 and 20c1.

[0027] Now for reference Figure 2BAn alternative example embodiment of the power supply circuit 160b is described. The power supply circuit 160b includes a first current sensor circuit 40b1 coupled to current sensor 20b1 and power unit 16b1, and a second current sensor circuit 40c1 coupled to current sensor 20c1 and power unit 16a1. In this respect, each of the current sensors 20b1 and 20c1 is powered by a power supply to the corresponding power unit and measures the output current of power units 16b1 and 16c1, respectively.

[0028] Now for reference Figure 3B An example current sensor circuit 40c1 is described. The current sensor circuit 40c1 includes a power supply 44 having a first input signal coupled to one or more phases of the three-phase input of the power unit 16c1, a second input signal coupled to a floating ground of the power unit 16c1, and providing power (e.g., +15 VDC) to the power supply terminal p of the current sensor 20c1. The output terminal m of the current sensor 20c1 is coupled to the input terminal of the processor 56 of the power unit 16c1.

[0029] Processor 56 provides the output signal measured from current sensor 20c1 to controller 18 via fiber optic interface 58. In this respect, the second current sensor circuit 40c1 does not require its own dedicated processor and fiber optic link, but instead uses the existing processor 56 and fiber optic link 58 of power unit 16c1 to transmit the output signal measured by current sensor 20c1 to controller 18. Although Figure 3B As not shown, the first current sensor circuit 40b1 can be the same as the second current sensor circuit 40c1, and the output signal measured by the current sensor 20b1 can be transmitted to the controller 18 using the processor of the power unit 16b1 and the fiber optic link. Figure 2B The isolation requirement for each current sensor in current sensors 20b1 and 20c1 is equal to the rated output voltage of power units 16b1 and 16c1, respectively.

[0030] Current sensor 20b1 measures the output current of power unit 16b1, and current sensor 20c1 measures the output current of power unit 16a1. The measured output current of power unit 16b1 is substantially equal to the "b" phase output current of power circuit 160b, and the measured output current of power unit 16c1 is substantially equal to the "c" phase output current of power circuit 160a. Therefore, power units 16b1 and 16c1 provide current feedback to controller 18 without requiring high-voltage isolation corresponding to the rated voltage of the power circuit.

[0031] The power unit according to this disclosure may include more than two current sensors. For example, now refer to Figure 2CAnother alternative example embodiment of the power supply circuit 160c is described. Specifically, the power supply circuit 160c includes current sensor circuits 40a1, 40b1, ..., 40b3, 40c3, which are respectively coupled to the corresponding power units 16a1, 16b1, ..., 16b3, 16c3 and respectively coupled to the corresponding current sensors 20a1, 20b1, ..., 20b3, 20c3. In this respect, each current sensor 20a1, 20b1, ..., 20b3, 20c3 is powered by the corresponding power unit 16a1, 16b1, ..., 16b3, 16c3 and measures its output current. In addition, the power units 16a1, 16b1, ..., 16b3, 16c3 are used to transmit the output signals measured by the corresponding current sensors 20a1, 20b1, ..., 20b3, 20c3 to the controller 18. This configuration can be used to provide redundancy for current sensing. Figure 2A and Figure 2B As shown in the embodiment, the isolation requirement for each of the current sensors 20a1, 20b1, ..., 20b3, 20c3 in FIG. 3C is equal to the rated output voltage (e.g., 480 V) of the corresponding power unit 16a1, 16b1, ..., 16b3, 16c3. Those skilled in the art will understand that individual current sensors 20a1, 20b1, ..., 20b3, 20c3 and current sensor circuits 40a1, 40b1, ..., 40b3, 40c3 can be used with all or fewer of the power units 16a1, 16b1, ..., 16b3, 16c3, depending on the required redundancy.

[0032] Figure 4 A simplified block diagram of a driver system (VFD) 400 relating to response surface (RS) and time constant according to an exemplary embodiment of the present disclosure is shown.

[0033] Typically, and as previously described, the drive system 400 includes: a power converter 410 comprising a plurality of power units supplying power to one or more output phases, each power unit including a plurality of switching devices; a plurality of sensors 420 monitoring values ​​of the power converter 410; and a control system 430 communicating with the power converter 410 and controlling the operation of the plurality of power units. The control system 430 is configured via computer-executable instructions to access and utilize a multidimensional response surface and / or time constant 440, for example, the time constants of one or more components of the drive system 400, to estimate or determine coolant flow rate and transient temperature behavior.

[0034] The driver system 400 can be referenced as follows Figure 1 , Figure 2A , Figure 2B , Figure 2C , Figure 3A and Figure 3B Implemented as described. Specifically, when referring to the sensing circuits in each power unit (such as sensing circuits 40, 40a1, 40b1, 40c1, etc.), the local processor (controller) within each power unit can determine / provide the coolant flow rate using the described system and method, and send it to the main controller (such as...). Figure 1 , Figure 2A , Figure 2B , Figure 2C , Figure 3A and Figure 3B Controller 18 or Figure 4 The control system 430 in the system is used to protect each power unit and the entire drive system.

[0035] In one embodiment, the drive system 400 includes a plurality of sensors 420 to monitor various characteristics and values ​​of the drive system 400. For example, the plurality of sensors 420 include sensors for measuring and monitoring the input voltage, output voltage, input current, output current, and internal temperature of the transformer and / or power converter 410 and / or cooling assembly of the power converter 410. The sensors 420 provide feedback data, such as values ​​and / or measurements of temperature, vibration, current, and voltage, to a control system (e.g., control system 430) via a data bus. The data bus may be one or more hardwired connections with sufficient voltage isolation.

[0036] Additionally, the drive system 400 includes (or is accessible) one or more reduced-order models (ROMs), such as those stored in the memory of the control system 430 or VFD 400. Reduced-order models are complex models that can be used to predict accurate information about key variables, such as the temperature within a component or subassembly that handles or dissipates power when using a cooling medium such as air or water. These models use measured or estimated power passing through the component or power dissipation within the component, as well as the flow rate of the coolant, as inputs.

[0037] In this document, a component or subassembly is referred to as an "apparatus," and the apparatus can be assembled with other components (including additional apparatus) to form a "product." The product contains software that provides the following functions: (a) Monitor internal and external variables, (b) Controlling the operation of the product, and (c) Communicate with internal and external components.

[0038] In theory, the coolant flow rate of a power unit can be measured using differential pressure sensors and / or flow sensors. However, these methods are prone to significant errors due to the turbulence of coolant flow in the area of ​​interest, and are also negatively affected by localized measurements that cannot provide the required averaging information above the surface or location of interest. Such measurements are possible in laboratory testing, for example, by using a long air tunnel, which is impractical in products installed at customer sites.

[0039] Within this disclosure, a response surface (hereinafter referred to as "RS") concept, designated as response surface 440, is provided, using several connections to the external physical world, which may be referred to as global input-output. This practically means that RS 440 is created using some input terminals (or variables) and other terminals as outputs. However, when RS 440 is used in an application (such as in a driver), it is used as a lookup table (hereinafter referred to as "LUT"), where one of the aforementioned inputs is used as the (LUT) output, and the remaining input selections and (raw) outputs are used as (LUT) inputs. In a practical sense or in practical applications, the goal is to obtain a coolant flow rate, such as air flow or water flow, corresponding to the input power and the measured (not simulated) temperature.

[0040] According to an exemplary embodiment of this disclosure, the described method and system utilize an accurate computational fluid dynamics (CFD) simulation of the device, which creates a multidimensional RS 440 with a power input and a coolant flow input, as well as a corresponding temperature output, which is also the actual measurement location of the internal temperature of the device.

[0041] As an alternative to the LUT representation of RS 440, RS 440 can be derived as a functional model unit (also referred to herein as "FMU") entity and used in a controller (e.g., control system 430 of driver 400) using compiled code (such as C code). This approach is suitable for carefully crafted digital models, such as CFDs of the entity of interest, in this case, the power unit.

[0042] The RS 440 method eliminates the inaccuracies of directly measuring coolant flow using differential pressure sensors and / or flow sensors.

[0043] Because the measured temperature is dependent on both power and coolant flow rate, the response surface connecting these three parameters can be obtained through various engineering methods, such as laboratory testing, engineering calculations, or numerical simulations. Within the product software, the actual coolant flow rate is reliably obtained by using the known power and the measured temperature from a fixed location inversely applying the RS (e.g., in the form of a multidimensional lookup table).

[0044] In one embodiment, numerical simulations are used to create RS entities, for example, in reverse within a drive system in the form of a multidimensional lookup table. In one example, the lookup table could be a 3-dimensional (3-D) lookup table. The 3-D lookup table entity could have a graphical representation with selected outputs on the z-axis, while selected pairs of inputs are located on the x and y axes, respectively. However, it should be noted that the actual lookup table is a multidimensional entity containing multiple inputs and outputs, and interpolation mechanisms will be used to find the output value of interest for a given combination of all available inputs. The multidimensional table is created to specify ranges for all used inputs; therefore, extrapolation is not used for the safety of the calculated outputs. Efficient design of experimental techniques is employed to minimize the computational cost of numerical simulations involving scanning reasonable (functional) ranges of input power and coolant flow during the simulation.

[0045] An experimental design (DE) was created by providing relevant ranges for two input parameters: power and coolant flow rate, ranging from approximately 50% to 120%. For each combination of these two input parameters, a numerical simulation was initiated in the background to extract one or more temperatures of interest that were also actually measured inside the actual product. The result of these multiple simulations was the creation of an airflow rate (RS), which would be used in reverse by the product software: using power and the measured temperature as inputs to obtain the airflow rate used by the ROM or other processes within the product.

[0046] Examples of applications of the described system and method are: - A power unit with transistors / IGBTs / diodes that dissipates power on a heatsink cooled by airflow. - Transformer windings that dissipate power and are cooled by airflow.

[0047] Figure 5 A graph showing a time constant associated with the transformer windings of a frequency converter driver, according to an exemplary embodiment of the present disclosure, is illustrated.

[0048] Response surface methodology provides steady-state values ​​of the internal temperature of the device at the location of interest. In another exemplary embodiment of this disclosure, a system and method are disclosed for determining and utilizing a time constant of a selected output to estimate transient temperature behavior associated with one or more devices, such as transformer windings or power units.

[0049] The time constant (usually denoted by the Greek letter τ) describes the properties of an exponential function and is approximately 63.2% of the time it takes for a physical system's response to a stepwise change in an external variable to reach its final (asymptotic) value. More specifically, physically, in an increasing system, the time constant is 1 - 1 / τ = 1 / τ * ... e≈ 63.2% of the time. In a decreasing system, the time constant τ represents the elapsed time required for the system response to decay to zero if the system continues to decay at the initial rate. Due to the asymptotic change in the decay rate, the response value will decrease to 1 / e ≈ 36.8%.

[0050] Figure 5 Figure 500 shows the time constant τ associated with the transformer windings. The x-axis represents time (in seconds), and the y-axis represents the charge value / apparent power (kVA) of each transformer winding. The transformer can be a multiphase transformer comprising a primary winding and an excitation secondary winding, wherein power units are operatively coupled to the secondary winding.

[0051] This figure illustrates multiple transformer windings and their corresponding transient temperature behavior in response to step excitation. The time constant τ is extracted from a selected transient waveform 510 obtained as a response to step excitation, where the time constant τ is preserved and stored as part of the response surface, see [link to relevant documentation]. Figure 4 440.

[0052] The transformer windings include rated values ​​and normal operating temperatures, with the winding temperature setting being configured to ensure that overheating and damage to the windings will not occur. The temperature setting takes into account the average ambient temperature of the transformer / drive system. For example, considering an average ambient temperature of 30°C, the transformer winding temperature setting could include a temperature rise of 80°C, meaning the transformer can operate under normal conditions at a maximum of 110°C.

[0053] In one example, the multiphase transformer has a rating of 1 MVA and normal operating conditions of up to 100°C, with a critical temperature of 135°C, which is the highest permissible temperature at which the transformer should operate. The transformer is to be loaded (overloaded) by 1 MVA to 2 MVA, with the transformer temperature at 100°C at the start of the loading process. The time constant τ describes the time required for the voltage to rise to approximately 0.632 (63.2%) of the difference between its old and new values ​​after the application of a pulse that induces such a change, with the highest permissible temperature being 135°C. In our example, the time constant τ describes how long it takes for the voltage to rise to approximately 63.2% of the difference between 1000 kVA and 2000 kVA (the new steady-state voltage) before reaching the critical temperature of 135°C.

[0054] Furthermore, the time constant τ allows the response surface methodology used in the transient domain to be extended to drive controllers. There are several methods for evaluating the time constant when analyzing transient waveform 510. The time constant can be determined using a formula (e.g., multiplying by 0.632 / 63.2% of the new steady-state voltage) or by determining the derivative of transient waveform 510. Transient waveform 510 originates from a separate transient analysis of the corresponding device (e.g., transformer windings, power units, power unit objects such as silicon chips, etc.). The RS method is only applicable when obtaining steady-state values, such as temperature. In all cases where the transient aspect is of concern, these steady-state values ​​can be used in conjunction with the time constant data (obtained separately). In other words, RS provides information on where it begins and where it goes, while the time constant provides the time range for the transition between two steady states.

[0055] Figure 6 The housing of a power supply including a cooling device according to an exemplary embodiment of the present disclosure is shown, and Figure 7 Showing Figure 6 The outer shell, in which the individual doors and panels were removed.

[0056] Another example is a multilevel converter with multiple power units housed in a rack and cooled by a device comprising multiple fans or blowers. Temperature sensing within each power unit is important for the driver because the airflow through each power unit may differ for several reasons: - The location of the power unit within the rack / enclosure (uneven air distribution). The number of fans in operation may vary based on available redundancy in cooling.

[0057] Figure 6 An illustrative power supply 300 enclosed within a single cabinet housing 302 is shown. The housing 302 may be adapted and configured to house various components of the power supply 300. The exterior of the housing 302 may include various control and information display devices 304, allowing customers or technicians to verify the operating parameters and current operating status of the power supply 300. Additionally, multiple doors or other access components may be provided for access to the various components included within the housing 302. A blower assembly 306 may be positioned adjacent to the housing 302 to provide airflow for cooling the various components of the power supply 300. The blower assembly 306 may be placed on top of the housing 302, thereby reducing the overall footprint of the completed power supply 300 assembly.

[0058] Figure 7 The power supply 300 is shown in enclosure 302, with various doors, access components, and blower assembly 306 removed. Enclosure 302 can be arranged and configured to house the various functional components of the power supply 300 in a single cabinet.

[0059] By providing the transformer chamber 314 and power unit chamber 316 in a vertical configuration, improved airflow through the housing 302 can be achieved. For example... Figure 6 and Figure 7 As shown, a parallel linear path can be followed from the bottom of housing 302 through transformer chamber 314 and power unit chamber 316, passing through a uniform rear air collection chamber to reach blower assembly 306. This provides a highly efficient cooling system because a single blower can simultaneously cool each component of the power supply. Depending on the operating parameters of the power supply, additional cooling systems (such as liquid cooling, radiators, or other similar systems) can be integrated to provide additional cooling for operating components such as transformers.

[0060] Figure 6 and Figure 7 The location of the cooling fans (blower assembly 306) above the unit and transformer sections 316, 314 is shown. Typically, two of the three fans are operational (the third is redundant and remains off), but depending on which two fans are operating (left, center, or right), the airflow through the unit (power unit chamber 316 located below the fans) is different; that is, the airflow through unit section 316 is uneven. Therefore, it is important to measure the airflow through each unit to ensure sufficient cooling is available.

[0061] The disclosed methods and systems allow the use of ROMs or other suitable models capable of providing the internal temperature of the drive system, a temperature that is currently unmeasurable but crucial for advanced (intelligent) operation. Additionally, it is possible to implement subassemblies capable of performing artificial intelligence (AI).

[0062] The proposed method provides the necessary answer for the correct airflow rate in each power unit very quickly, almost instantaneously, because the process of identifying the required value in the lookup table (or RS) is extremely fast. This is important, especially in drives with many power units (thus providing the required value to the drive controller almost in real time). Currently, there is no available method to evaluate the actual airflow rate of the power units in a drive. Furthermore, the method is equally applicable to water-cooled units.

[0063] Furthermore, the time constant τ allows the response surface methodology used in the transient domain to be extended to drive controllers. The time constant is part of the response surface and therefore can be evaluated in locations where there are no temperature sensors in the drive system.

[0064] Figure 8 A flowchart is shown of a method 800 for determining and utilizing a time constant associated with a response surface (RS) according to an embodiment of the present disclosure.

[0065] Although method 800 is described as a series of actions or steps performed in a certain order, it should be understood that method 800 may not be restricted by the order. For example, unless otherwise stated, some operations may occur in a different order than that described herein. Additionally, in some cases, an operation may occur simultaneously with another operation. Furthermore, in some cases, not all operations are required to implement the method described herein.

[0066] Method 800 may begin at 810 and includes operations 820 for creating a transient waveform of the device for the VFD, operations 830 for extracting a time constant from the transient waveform, and operations 840 for combining the time constant with the multidimensional RS and storing it in the memory of the VFD. Method 800 may end at 850.

[0067] It should be understood that the operations associated with the methods, features, and functions described above (other than any described manual operations) can be performed by one or more data processing systems by operating at least one processor. As used herein, a processor corresponds to any electronic device configured to process data via hardware circuitry, software, and / or firmware. For example, the processor described herein may correspond to one or more (or combinations of) a microprocessor, a CPU, or any other integrated circuit (IC) or other type of circuitry capable of processing data in a data processing system. At least one processor described or claimed to be configured to perform a particular described / claimed process or function may correspond to a CPU that executes computer / processor-executable instructions stored in memory in the form of software and / or firmware to perform such described / claimed processes or functions. However, it should also be understood that such a processor may correspond to an IC that is hardwired with a processing circuit system (e.g., an FPGA or ASIC IC) to perform such described / claimed processes or functions.

Claims

1. A variable frequency drive system (400), comprising: Power converter (410), the power converter including multiple power units supplying power to one or more output phases, each power unit including multiple switching devices, Multiple sensors (420) monitor the values ​​of the power converter (410), and Control system (430), which communicates with the power converter (410) and controls the operation of the plurality of power units, and The memory stores one or more time constants. The control system (430) is configured by computer-executable instructions to determine transient temperature behavior using the time constant.

2. The variable frequency drive system (400) according to claim 1, wherein, The plurality of switching devices in each power unit include insulated gate bipolar transistors (IGBTs) and diodes, wherein the control system is configured to use the time constant to determine the transient temperature behavior of the IGBTs and / or the diodes.

3. The variable frequency drive system (400) according to claim 1 further includes: A transformer (14) comprising windings, wherein the control system (430) is configured to use the time constant to determine the transient temperature behavior of the transformer windings.

4. The variable frequency drive system (400) according to claim 1, wherein, The time constant is an element of a multidimensional response surface (RS) (440) stored in the memory, and the control system (430) is configured to access and utilize the multidimensional RS (440) to obtain the internal coolant flow rate.

5. The variable frequency drive system (400) according to claim 4, wherein, The internal coolant flow rate is the internal air flow rate.

6. The variable frequency drive system (400) according to claim 4, wherein, The multidimensional RS (440) is designed as a multidimensional lookup table.

7. The variable frequency drive system (400) according to claim 6, wherein, The input values ​​of the multidimensional lookup table include power and measured internal temperature, and the output value is the internal coolant flow rate.

8. The variable frequency drive system (400) according to claim 4, wherein, The multidimensional RS (440) is designed as a functional model unit (FMU) containing compiled code.

9. The variable frequency drive system (400) according to claim 4, wherein, The multidimensional RS (440) is created using computational fluid dynamics (CFD) simulations with one or more selected devices.

10. The variable frequency drive system (400) according to claim 9, wherein, The CFD simulation uses power input and coolant flow input, as well as associated temperature output, which is also the actual measurement location of the temperature within the one or more selected devices.

11. A method (800) for determining and utilizing a time constant associated with a variable frequency drive (VFD), the method comprising operating at least one processor: The transient waveform of the device that creates the (820) VFD. Extract the (830) time constant from the transient waveform. The time constant and the multidimensional response surface (RS) (440) are stored (840) in the memory of the VFD.

12. The method (800) according to claim 11, further comprising: The time constant stored in the memory is accessed and utilized by the control system (430) to determine the transient temperature behavior of the device.

13. The method (800) according to claim 12, further comprising: The transient temperature behavior of the switching device of the power unit, which includes an insulated gate bipolar transistor (IGBT) and a diode, is determined using the time constant.

14. The method (800) according to claim 12, further comprising: The transient temperature behavior of the transformer windings is determined using the time constant.

15. The method (800) according to claim 14, wherein, The transient temperature behavior of the transformer windings is determined for the load process of the transformer (14).

16. The method (800) according to claim 12, wherein, The control system (430) is configured to access and utilize the multidimensional RS (440) to obtain the internal coolant flow rate.

17. The method (800) according to claim 11, wherein, The multidimensional RS (440) is designed as a multidimensional lookup table.

18. The method (800) according to claim 11, wherein, The multidimensional RS (440) is designed as a functional model unit (FMU) comprising compiled code, wherein the input values ​​of the multidimensional lookup table include power and measured internal temperature, and the output value is internal coolant flow rate.

19. The method (800) according to claim 11, further comprising: The multidimensional RS (440) is created using computational fluid dynamics (CFD) simulations of one or more selected devices.

20. The method (800) according to claim 19, wherein, The CFD simulation uses power input and coolant flow input, as well as associated temperature output, which is also the actual measurement location of the temperature within the one or more selected devices.

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