System and method for obtaining coolant flow rate of power battery of variable frequency drive

Abstract

A variable frequency drive system comprising a power converter (160a) comprising a plurality of power cells (16a1-16c3) powering one or more output phases, each power cell comprising a plurality of switching devices, a plurality of sensors for monitoring a value of the power converter, and a control system (18) in communication with the power converter and controlling the operation of the plurality of power cells, where the control system is configured to access and utilize the multi-dimensional response surface via computer executable instructions to obtain the internal coolant flow rate.

Description

Technical Field

[0001] Various aspects of the present disclosure relate to a variable frequency drive, also referred to as a VFD, powered by an electric motor, driving a load such as a pump, compressor, fan, or reciprocating compressor system. In the specification, the terms "drive," "drive system," "multi-stage power converter," "converter," "power supply," and "variable frequency drive (VFD)" may be used interchangeably. Background Art

[0002] Examples of variable frequency drives include medium voltage (MV) variable frequency drives, such as multi-level power converters, which are used in applications such as medium voltage AC (AC) drives, flexible AC transmission systems (FACTS), and high voltage DC (HVDC) transmission systems, because individual power semiconductor devices are not rated for high voltage. Multi-level power converters typically include multiple power cells for each phase, each power cell including an inverter circuit with a semiconductor switch that can change the voltage output of each individual cell. An example of a multi-level power converter is, for example, a cascaded H-bridge converter system with multiple H-bridge cells as described in Hammond's patent US 5,625,545. 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, as well as individual converters or multi-converter systems. Summary of the invention

[0003] Various aspects of the present disclosure are generally directed to a variable frequency drive and method for controlling a variable frequency drive, obtaining an internal coolant flow rate of the variable frequency drive in connection with accessing and utilizing a response surface.

[0004] A first aspect of the present disclosure provides a variable frequency drive system, comprising a power converter, the power converter comprising a plurality of power batteries for powering one or more output phases, each power battery comprising a plurality of switching devices, a plurality of sensors for monitoring a value of the power converter, and a control system for communicating with the power converter and controlling the operation of the plurality of power batteries, wherein the control system is configured to obtain an internal coolant flow rate by accessing and utilizing a multidimensional response surface through computer-executable instructions.

[0005] A second aspect of the present disclosure provides a method for controlling a variable frequency drive, the method comprising accessing and utilizing a multi-dimensional response surface by executing at least one processor to obtain an internal coolant flow rate.

[0006] Other aspects of the present disclosure provide a non-transitory computer-readable medium storing executable instructions, which, when executed by a computer, perform a method for controlling a variable frequency drive, the method comprising accessing and utilizing a multi-dimensional response surface to obtain an internal coolant flow rate by executing at least one processor. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 shows a block diagram of an exemplary multi-battery power supply according to an exemplary embodiment of the present disclosure,

[0008] Figure 2A Shows Figure 1 A block diagram of an exemplary power supply circuit of a multi-battery power supply according to an exemplary embodiment of the present disclosure,

[0009] Figure 2B Shows Figure 1 A block diagram of an alternative exemplary power supply circuit for a multi-battery power supply according to an exemplary embodiment of the present disclosure,

[0010] Figure 2C Shows Figure 1 A block diagram of another alternative exemplary power supply circuit of a multi-battery power supply according to an exemplary embodiment of the present disclosure,

[0011] Figure 3A Shows Figure 1 A block diagram of an exemplary current sensor circuit and a power battery of a multi-battery power supply according to an exemplary embodiment of the present disclosure,

[0012] Figure 3B Shows Figure 1 A block diagram of an alternative exemplary current sensor circuit and a power battery of a multi-battery power supply according to an exemplary embodiment of the present disclosure,

[0013] Figure 4 shows a simplified block diagram of a power supply associated with a response surface (RS) according to an exemplary embodiment of the present disclosure,

[0014] Figure 5 A housing for a power supply including a cooling device according to an exemplary embodiment of the present disclosure is shown. Figure 6 Shows the various doors and panels removed Figure 5 The shell,

[0015] Figure 7 A flow chart of a method for controlling a power supply in relation to a response surface (RS) according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0016] To facilitate understanding of the embodiments, principles and features of the present disclosure, the following is an explanation of the implementation schemes in the illustrative embodiments. These embodiments, principles and features are particularly described in relation to a system and method for obtaining a coolant flow rate of a power battery of a variable frequency drive.

[0017] The components and materials described herein that make up the various embodiments are intended to be illustrative and not limiting. Various suitable components and materials that perform the same or similar functions as the materials described herein are intended to be included within the scope of the embodiments of the present disclosure.

[0018] refer to Figure 1 , the exemplary multi-battery power supply 100a includes a transformer 14, a power circuit 160, a controller 18, and feedback resistors R1 and R2. The power supply 100a provides output power to a load 12.

[0019] refer to Figure 2A , describes an exemplary embodiment of a power circuit 160. The power circuit 160a includes nine power batteries 16a1, 16b1, ... 16c3, which are coupled to the transformer 14 (to avoid obscuring the figure, the transformer 14 is not shown), and coupled to the controller 18 via a communication link. It will be appreciated by those skilled in the art that more or less than nine power batteries 16a1, 16b1, ... 16c3 may be used.

[0020] Each output phase of the power circuit 160a is powered by a group of power batteries 16a1, 16b1, ... 16c3 connected in series. Power batteries 16a1, 16a2 and 16a3 are coupled in a first phase group, power batteries 16b1, 16b2 and 16b3 are coupled in a second phase group, and power batteries 16c1, 16c2 and 16c3 are coupled in a third phase group, and the three phase groups are connected in a star connection at a reference node 42. It will be appreciated by those skilled in the art that more or less than three output phases may be used.

[0021] The power supply circuit 160a also includes a current sensing circuit 40 coupled to current sensors 20b1 and 20c1, a power battery 16c1, a controller 18, and a reference node 42. The current sensors 20b1 and 20c1 may be conventional current sensors. The current sensors 20b1 and 20c1 are adjacent to the reference node 42 and have power supply terminals p, respectively, and provide a measurement output signal at an output terminal m.

[0022] refer to Figure 3A, an exemplary current sensor circuit 40 is described. The current sensor circuit 40 includes a power supply 44, a processor 46, and an optical fiber interface 48. The power supply 44 includes a first input signal coupled to one or more of the three-phase inputs of the power battery 16cl, and a second input signal coupled to the reference node 42, and provides power (e.g., +15V DC) to the power terminals p of the current sensors 20bl and 20cl. The power supply 44 can be any conventional AC-DC converter or other similar power supply.

[0023] The processor 46 has an input coupled to the output m of the current sensors 20bl and 20cl, and has an output coupled to the fiber optic interface 48. The processor 46 provides the measured output signals from the current sensors 20bl and 20cl to the controller 18 through the fiber optic interface 48. The processor 46 can be a microprocessor, a programmable gate array device (e.g., FPGA) that can be configured to perform processor functions, an operational amplifier-based circuit with a V / f converter for transmitting sensed feedback through optical fiber, or other similar processors or circuits. The fiber optic interface 48 is coupled between the processor 46 and the controller 18 and provides electrical isolation between the current sensor circuit 40 and the controller 18.

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

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

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

[0027] refer to Figure 2B, describes an alternative exemplary embodiment of the power supply circuit 160. The power supply circuit 160b includes a first current sensor circuit 40b1 coupled to the current sensor 20b1 and the power battery 16b1, and a second current sensor circuit 40c1 coupled to the current sensor 20c1 and the power battery 16c1. In this regard, the current sensors 20b1 and 20c1 are respectively powered by the power supply supplying the corresponding power battery, and respectively measure the output current of the power batteries 16b1 and 16c1.

[0028] refer to Figure 3B , describes an exemplary current sensor circuit 40cl. The current sensor circuit 40cl includes a power supply 44 having a first input signal coupled to one or more phases of the three-phase input of the power battery 16cl, a second input signal coupled to the floating ground of the power battery 16cl, and providing power (e.g., +15V DC) to the power terminal p of the current sensor 20cl. The output terminal m of the current sensor 20cl is coupled to the input terminal of the processor 56 of the power battery 16cl.

[0029] The processor 56 provides the measured output signal from the current sensor 20cl to the controller 18 via the fiber optic interface 58. In this regard, the second current sensor circuit 40cl does not require its own dedicated processor and fiber optic link, but instead uses the existing processor 56 and fiber optic link 58 of the power battery 16cl to transmit the measured output signal of the current sensor 20cl to the controller 18. Figure 3B Not shown, the first current sensor circuit 40bl may be identical to the second current sensor circuit 40cl, and the measured output signal of the current sensor 20bl may be transmitted to the controller 18 using an optical fiber link between the processor and the power battery 16bl. Figure 2B The insulation requirement of each current sensor 20bl and 20cl is equal to the rated output voltage of the power batteries 16bl and 16cl respectively.

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

[0031] The power battery according to the present disclosure may include more than two current sensors. Figure 2CAnother alternative exemplary embodiment of the power supply circuit 160 is described. Specifically, the power supply circuit 160c includes current sensor circuits 40a1, 40bl, ... 40b3, 40c3, and corresponding current sensors 20al, 20bl, ... 20b3, 20c3, respectively coupled to corresponding power batteries 16a1, 16bl, ... 16b3, 16c3. In this regard, each current sensor 20a1, 20bl, ... 20b3, 20c3 is powered by the output current of the corresponding power battery 16a1, 16bl, ... 16b3, 16c3 and measures the output current of the corresponding power battery. In addition, the power batteries 16a1, 16bl, ... 16b3, 16c3 are used to transmit the measured output signals of the corresponding current sensors 20a1, 20bl, ... 20b3, 20c3 to the controller 18, respectively. This configuration can be used to provide redundancy for current sensing. As Figure 2A and Figure 2B In the embodiment, the insulation requirement of each current sensor 20a1, 20bl, ... 20b3, 20c3 is equal to the rated output voltage (e.g., 480V) of the corresponding power battery 16a1, 16bl, ... 16b3, 16c3. It will be appreciated by those skilled in the art that, depending on the required amount of redundancy, the separate current sensors 20a1, 20bl, ... 20b3, 20c3 and the current sensor circuits 40a1, 40bl, ... 40b3, 40c3 may be used with all or less than all of the power batteries 16a1, 16bl, ... 16b3, 16c3.

[0032] Figure 4 A simplified block diagram of a drive system 400 associated with a response surface (RS) according to an exemplary embodiment of the present disclosure is shown.

[0033] The drive system 400, such as a variable frequency drive system, generally includes a power converter 410, the power converter 410 including a plurality of power cells supplying power to one or more output phases, each power cell including a plurality of switch devices, a plurality of sensors 420 for monitoring the value 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 cells, wherein the control system 430 is configured to obtain the internal coolant flow rate by accessing and utilizing a multi-dimensional response surface 440 through computer-executable instructions. In one example, the response surface 440 may be a three-dimensional response surface.

[0034] The drive system 400 can be as shown in FIG. Figure 1 , Figure 2A , Figure 2B , Figure 2C , Figure 3A and Figure 3BSpecifically, if the sensing circuits in each power battery, such as sensing circuits 40, 40a1, 40b1, 40c1, etc., are involved, the local processor (controller) in each power battery can be used to determine / provide the coolant flow rate through 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 is used to protect each power battery and the entire drive system.

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

[0036] In addition, the drive system 400 includes one or more reduced order models (ROMs) received and stored by the control system. Reduced order models are complex models that can be used to predict accurate information about key variables, such as the temperature inside a component or subassembly that processes or consumes power when a cooling medium, such as air or water, is used. These models use measured or estimated power through a component or power consumption within a component and the flow rate of the coolant as input.

[0037] In this application, a component or subassembly is referred to as a "device", and the device may be assembled with other components including additional devices into a "product". The product contains software that provides the following functions:

[0038] (a) monitoring internal and external variables,

[0039] (b) control the operation of the Product, and

[0040] (c) Communicate with internal and external components.

[0041] In theory, it is possible to obtain measurements of the coolant flow rate of a power battery by using differential pressure sensors and / or flow sensors. However, these methods are prone to significant errors due to turbulent effects of the coolant flow in the area of ​​interest, and are also negatively affected by the fact that local measurements are unlikely to provide the required average information over the surface or location of interest. Such measurements are feasible in laboratory tests, for example by using long air tunnels, which is not practical for products installed at customer locations.

[0042] In the content of the present disclosure, a response surface (hereinafter referred to as "RS") concept is provided, which is labeled as a response surface 440, which uses multiple connections with the external physical world, which can be referred to as global input and output. This actually means that RS440 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 drive, it is used as a lookup table (hereinafter referred to as "LUT"), with one of the above-mentioned inputs as (LUT) output, and with the remaining selection of inputs and (original) output as (LUT) input. In a practical sense or in a practical application, the goal is to obtain a coolant flow rate, such as an air flow rate or a water flow rate, which corresponds to an input power and a measured temperature, rather than a simulated temperature.

[0043] According to an exemplary embodiment of the present disclosure, the described method and system utilize an accurate computational fluid dynamics (CFD) simulation of the device, which creates a multi-dimensional RS440 with power input and coolant flow rate input and associated temperature output, which is also the actual measurement location of the temperature within the device. As an alternative to the LUT representation of RS440, RS440 can be output as a functional entity model unit (also referred to as "FMU" herein) entity and used in a controller, such as a control system 430 of a drive 400, by using compiled code, such as C code. This method is suitable for carefully created digital models of entities of interest, such as CFD, which are power batteries in this case.

[0044] The RS 440's approach eliminates the inaccuracies of directly measuring coolant flow using differential pressure sensors and / or flow sensors.

[0045] Due to the dependence of the measured temperature on power and coolant flow rate, a response surface connecting the three parameters can be obtained by various engineering methods, such as laboratory tests, engineering calculations or numerical simulations. Inside the product software, the actual coolant flow rate is obtained in a reliable way using, for example, RS in the form of a multidimensional lookup table, inversely using the known power and the temperature measured from a fixed position.

[0046] In one embodiment, numerical simulation is used to create RS entities, for example in the form of multi-dimensional lookup tables, that are used inversely within the drive system. In one example, the lookup table can be a three-dimensional lookup table. An efficient design of experimental technique is used to minimize the computational cost of the numerical simulation, which includes sweeping a reasonable (function) range of input power and coolant flow rate during the simulation.

[0047] A Design of Experiments (DE) is created by providing relevant ranges of two input parameters (power and coolant flow rate), both ranging between approximately 50% and 120%. For each combination of these two input parameters, a numerical simulation is started in the background to extract one or more temperatures of interest that are actually measured inside the real product. The result of these multiple simulations is the creation of an RS that will be used in reverse by the product software: using the power and the measured temperatures as input to obtain the air flow rate used by the ROM or other processes inside the product.

[0048] Examples of applications of the described systems and methods are:

[0049] - a power cell with transistors / IGBTs / diodes dissipating power on a heat sink cooled by airflow,

[0050] - Transformer windings that consume power and are cooled by the air flow.

[0051] Figure 5 A housing for a power supply including a cooling device according to an exemplary embodiment of the present disclosure is shown. Figure 6 Shows the various doors and panels removed Figure 5 shell.

[0052] Another example is a multi-level converter with multiple power cells located within a cabinet and cooled by a device that includes multiple fans or blowers. Temperature sensing within each power cell is important to the driver because the airflow through each power cell may be different due to factors such as:

[0053] - The location of the power battery inside the cabinet / housing (uneven air distribution),

[0054] -The number of fans in operation may vary depending on the redundancy available in the cooling system.

[0055] Figure 5An exemplary power supply 300 is shown enclosed within a single cabinet housing 302. The housing 302 can be adapted and configured to house the various components of the power supply 300. The exterior of the housing 302 can include various controls and information displays 304, allowing a customer or technician to verify the operating parameters and current operating status of the power supply 300. In addition, a plurality of doors or other access devices can be provided to enable access to the various components contained within the housing 302. A blower assembly 306 can be located proximate the housing 302 to provide airflow for cooling the various components of the power supply 300. The blower assembly 306 can be disposed at the top of the housing 302, thereby reducing the overall footprint of the components of the completed power supply 300.

[0056] Figure 6 The power supply 300 is shown in a housing 302 with various doors, access features, and a blower assembly 306 removed. The housing 302 may be arranged and configured to house the various functional components of the power supply 300 in a single cabinet.

[0057] By providing the transformer chamber 314 and the power battery chamber 316 in a vertical design, improved airflow through the housing 302 can be achieved. Figure 5 and Figure 6 As shown, parallel linear paths can start from the bottom of the housing 302, through the transformer chamber 314 and the power battery chamber 316, and reach the blower component 306 via the uniform rear plenum. This provides an efficient cooling system because a single set of blowers can provide cooling for each component of the power supply at the same time. Depending on the operating parameters of the power supply, additional cooling, such as liquid cooling, radiators, or other similar cooling systems can be integrated to provide additional cooling for working components such as transformers.

[0058] Figure 5 and Figure 6 The location of the cooling fans (blower assembly 306) above the power battery and transformer sections 316, 314 is shown. Typically two of the three fans are running (the redundant third fan remains off), but depending on which two fans are running (left, center, or right), the airflow through the power battery (the power battery compartment 316 located below the fans) is different, i.e., the airflow through the power battery section 316 is non-uniform. Therefore, it is important to measure the airflow through each power battery to ensure adequate cooling.

[0059] With the disclosed methods and systems, a ROM or other suitable model can be used that can provide internal temperatures of the drive system that cannot be measured but are critical to advanced (intelligent) operation. In addition, sub-components that can implement artificial intelligence (AI) are possible.

[0060] Since the process of identifying the required value in the lookup table (or RS) is very fast, the proposed method provides the required answer for the correct air flow rate in each power cell very quickly, practically instantaneously. This is important especially in drives with multiple power cells, to provide the drive controller with the required values ​​almost in real time. There is currently no method available to evaluate the actual air flow in the power cells in a drive. Furthermore, the method is equally applicable to water-cooled units.

[0061] Figure 7 A flow chart of a method 700 for controlling a power supply in relation to a response surface (RS) according to an embodiment of the present disclosure is shown.

[0062] Although method 700 is described as a series of actions or steps performed in order, it should be understood that method 700 may not be limited by order. For example, unless otherwise specified, some actions may be performed in an order different from that described herein. In addition, in some cases, an action may occur simultaneously with another action. In addition, in some cases, all actions may not be required to implement the method described herein.

[0063] Method 700 may begin at 710 and include an act 720 of creating a multi-dimensional response surface 440 using a computational fluid dynamics (CFD) simulation of one or more selected devices using power input and coolant flow rate input and associated temperature output that is also an actual measurement location of the temperature inside the one or more selected devices, and an act 730 of accessing and utilizing the multi-dimensional response surface 440 to obtain the internal coolant flow rate. Method 700 may end at 740.

[0064] As previously described, the multi-dimensional response surface 440 may be designed as a multi-dimensional lookup table, wherein the input values ​​of the lookup table include power and measured internal temperature, and the output value is the internal coolant flow rate.

[0065] It should be understood that the actions associated with the above methods, features and functions (except for the described manual actions) can be performed by one or more data processing systems by running at least one processor. As used herein, a processor corresponds to an electronic device that processes data by hardware circuits, software and / or firmware configurations. The processor described herein may correspond to, for example, one or more microprocessors, CPUs or other integrated circuits (ICs) or other types of circuits (or combinations thereof) that can process data in a data processing system. At least one processor described or claimed as being configured to perform a specific described / claimed process or function may correspond to a CPU that executes instructions that can be executed by a computer / processor stored in a memory in the form of software and / or firmware to perform such described / claimed process or function. However, it should also be understood that such a processor may correspond to an IC (e.g., an FPGA or ASIC IC) that is hardwired to a processing circuit to perform such described / claimed process or function.

Claims

1. A variable frequency drive system, comprising: A power converter, the power converter comprising a plurality of power cells for supplying power to one or more output phases, each power cell comprising a plurality of switch devices, a plurality of sensors for monitoring values ​​of the power converter, and a control system that communicates with the power converter and controls the operation of the plurality of power batteries, in, The control system is configured to access and utilize the multi-dimensional response surface to obtain the internal coolant flow rate via computer executable instructions.

2. The variable frequency drive according to claim 1, wherein: The internal coolant flow rate is the internal air flow rate.

3. The variable frequency drive of claim 1, further comprising a reduced order model (ROM) stored in a memory of the control system, wherein: The reduced order model is configured for further processing using the internal coolant flow rate.

4. The variable frequency drive according to claim 1, wherein: The multidimensional response surface design is a multidimensional lookup table.

5. The variable frequency drive according to claim 4, wherein: The input values ​​of the multi-dimensional lookup table include power and measured internal temperature, and the output value is the internal coolant flow rate.

6. The variable frequency drive of claim 1, wherein: The multi-dimensional response surface is designed as a functional mock-up unit (FMU) including compiled code.

7. The variable frequency drive according to claim 1, wherein: Computational fluid dynamics (CFD) simulations of one or more selected devices are used to create a multi-dimensional response surface.

8. The variable frequency drive according to claim 7, wherein: The computational fluid dynamics simulation uses power input and coolant flow rate input and associated temperature output, which is also the actual measurement location of the temperature inside one or more selected devices.

9. A method for controlling a variable frequency drive, comprising, by executing at least one processor: Access and utilize multidimensional response surfaces for internal coolant flow rates.

10. The method according to claim 9, wherein: The multidimensional response surface design is a multidimensional lookup table.

11. The method according to claim 9, wherein: The multi-dimensional response surface is designed as a functional mock-up unit (FMU) including compiled code.

12. The method of claim 10, wherein The input values ​​of the multi-dimensional lookup table include power and measured internal temperature, and the output value is the internal coolant flow rate.

13. The method of claim 9, further comprising creating a multi-dimensional response surface using computational fluid dynamics (CFD) simulation of one or more selected devices.

14. The method of claim 13, wherein The computational fluid dynamics simulation uses power input and coolant flow rate input and associated temperature output, which is also the actual measurement location of the temperature inside one or more selected devices. 15 . A non-transitory computer readable medium storing executable instructions, which, when executed by a computer, perform the method for controlling a variable frequency drive according to claim 9 .

Images