A motor towing test platform and a method for suppressing power oscillation thereof

Abstract

In the embodiment of the present application, a motor-to-motor test platform and a method for suppressing power oscillation thereof are provided, which belongs to the field of motor testing technology. The motor-to-motor test platform specifically includes a power grid and a power circulation loop, wherein the power circulation loop includes a motor under test, a load motor and a control system, wherein the control system includes a machine-side rectifier electrically connected to the load motor, and a trap is connected in series with the active current instruction front stage of the machine-side rectifier to damp the current on the active current component in the transmission path. Through the processing scheme of the present application, the power circulating in the motor-to-motor test platform is reduced to produce undesirable low-frequency oscillations, thereby ensuring the safe and limited operation of the motor-to-motor test platform.

Description

Technical Field

[0001] The invention relates to the field of motor testing, and in particular to a motor towing test platform and a power oscillation suppression method thereof. Background Art

[0002] As energy conversion devices, high-power motors and converters are increasingly widely used in industrial frequency conversion and electrified transportation. For their under-load testing, compared with directly connecting resistive loads, the power cycle solution based on converter and motor dragging can greatly reduce power loss and improve test flexibility.

[0003] The towing platform can be AC ​​coupled to the power grid to supplement the energy lost in the power cycle. The capacity of the power grid is usually smaller than the capacity of the power cycle loop, which causes the power circulating in the platform to produce low-frequency oscillations under this weak grid. This oscillation can cause the system to fail to operate to the rated power, and even motor shaft fatigue failure, converter fault protection or failure. Summary of the invention

[0004] On the one hand, the present application provides a motor-to-motor test platform to reduce the power circulating in the motor-to-motor test platform to generate undesirable low-frequency oscillations, thereby ensuring the safe and limited operation of the motor-to-motor test platform.

[0005] A motor towing test system adopts the following technical solution:

[0006] A motor-to-motor test platform comprises a power grid and a power circulation loop, wherein the power circulation loop comprises a motor to be tested, a load motor and a control system, wherein the control system comprises a machine-side rectifier electrically connected to the load motor, and a trap is connected in series before the active current instruction of the machine-side rectifier to damp the current on the active current component in the transmission path.

[0007] Optionally, the capacity of the power grid is less than the capacity of the power circulation rate.

[0008] Optionally, the machine-side rectifier includes a voltage loop controller and a current loop controller, and the trap is connected in series between the voltage loop controller and the current loop controller.

[0009] Optionally, the transfer function of the notch filter is 1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 ), where ω0 is the central angular frequency of the notch filter, ξ is the notch bandwidth, N is the notch depth, and s is the Laplace transform operator.

[0010] On the other hand, the present application provides a method for suppressing power oscillations of a motor-to-motor test platform, thereby reducing the power circulating in the motor-to-motor test platform to generate undesirable low-frequency oscillations, thereby ensuring the safe and limited operation of the motor-to-motor test platform.

[0011] A method for suppressing power oscillation of a motor-to-motor test platform adopts the following technical solution:

[0012] A method for suppressing power oscillation of a motor-to-drag test platform comprises the following steps:

[0013] Draw the Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output under the initial operating conditions;

[0014] Identify the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform from the Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output without a series notch filter;

[0015] A notch filter is connected in series before the active current command of the machine-side rectifier, and a Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output after the notch filter is connected in series is drawn;

[0016] Adjust the parameters of the notch filter until the difference between the resonant peaks of the two closed-loop transfer function Bode plots reaches the required value.

[0017] Optionally, ω0=2πf0, where f0 is in the range of 0.5-1.5 times f r , f0 is the center frequency of the notch filter, ω0 is the center angular frequency of the notch filter, f r is the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform, the range of the notch bandwidth ξ is 0-1, and the range of the notch depth N is 0-1.

[0018] Optionally, a method for adjusting the parameters of the notch filter is to increase f0 or reduce the DC voltage loop bandwidth.

[0019] Optionally, after adjusting the parameter of the notch filter to the required value of the difference between the resonant peaks of the Bode diagrams of the two closed-loop transfer functions, the following steps are also included: testing the low-frequency oscillation of the towing platform to obtain the attenuation degree of the low-frequency oscillation;

[0020] When the attenuation degree of the low-frequency oscillation reaches the design requirement, the process ends;

[0021] When the attenuation degree of the low-frequency oscillation does not meet the design requirements, the parameters of the notch filter are adjusted in two stages until the difference between the resonant peaks of the two closed-loop transfer function Bode diagrams reaches the required value and the attenuation degree of the low-frequency oscillation reaches the design requirements.

[0022] Optionally, the method for performing two-stage adjustment on the parameters of the notch filter is any one or more of reducing f0, increasing ξ, and increasing N.

[0023] Optionally, the parameters of the notch filter are adjusted so that the absolute value of the difference between the resonant peaks of the two closed-loop transfer function Bode plots is 0-1 dB.

[0024] In summary, this application includes the following beneficial technical effects:

[0025] By adding a notch filter, the low-frequency oscillation of the towing test platform is suppressed, avoiding motor shaft fatigue failure, converter fault protection or failure caused by low-frequency oscillation, so that the towing test platform can run at full power under weak grid with limited capacity, so as to test various technical indicators of converter and motor to the maximum extent;

[0026] The system's low-frequency oscillation is suppressed only in the machine-side rectifier, while ensuring its ability to control the DC bus voltage. There is no need to change the control architecture of the grid-side rectifier, machine-side inverter, and grid-side inverter, so it has strong feasibility and wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 This is a schematic diagram of the motor towing test platform structure of the present application;

[0029] Figure 2 This is a control block diagram of the machine-side rectifier of this application;

[0030] Figure 3 This is a flow chart of the power oscillation suppression method of the motor towing test platform of the present application;

[0031] Figure 4 Bode plot of the closed-loop transfer function from DC current disturbance to AC current output for this application;

[0032] Figure 5 This is the current and power waveform diagram of the motor-to-motor test platform before and after the use of the trap.

[0033] Explanation of the accompanying drawings: 1. power grid; 2. transformer; 3. motor under test; 4. load motor; 5. control system; 51. grid-side rectifier; 52. machine-side inverter; 53. grid-side inverter; 54. machine-side rectifier; 6. Bode plot of the closed-loop transfer function of the DC current disturbance of the machine-side rectifier to the AC current output without a series trap; 7. Bode plot of the closed-loop transfer function of the DC current disturbance of the machine-side rectifier to the AC current output after a series trap. DETAILED DESCRIPTION

[0034] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0035] The following describes the implementation methods of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the following embodiments and the features in the embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.

[0036] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present application, it should be understood by those skilled in the art that an aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein can be used to implement this device and / or practice this method.

[0037] It should also be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application. The drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0038] Additionally, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, it will be understood by those skilled in the art that the aspects described may be practiced without these specific details.

[0039] An embodiment of the present application provides a motor pairing test platform.

[0040] like Figure 1 As shown, a motor-to-motor test platform includes a power grid 1, a transformer 2 and a power circulation loop. The power circulation loop is AC-coupled to the power grid 1 through the transformer 2. The capacity of the power grid 1 is smaller than the capacity of the power circulation loop.

[0041] The power circulation loop includes a motor under test 3, a load motor 4, a control system 5 and a detection system.

[0042] The output shaft of the motor under test 3 and the output shaft of the load motor 4 are connected by mechanical transmission. In this embodiment, the output shaft of the motor under test 3 and the output shaft of the load motor 4 are connected by a coupling, and the output shaft of the motor under test 3 and the output shaft of the load motor 4 are coaxially arranged. In other embodiments, the output shaft of the motor under test 3 and the output shaft of the load motor 4 can also be connected by a gear set transmission.

[0043] The control system 5 includes a machine-side inverter 52 and a grid-side rectifier 51 connected to the motor 3 under test in sequence, and the control system 5 also includes a machine-side rectifier 54 and a grid-side inverter 53 connected to the load motor 4 in sequence, and the grid-side rectifier 51 is electrically connected to the grid-side inverter 53. The detection system is a rotary encoder for detecting the rotor position information of the motor 3 under test and the load motor 4.

[0044] After the power circulation loop is powered on, the grid-side rectifier 51 converts the AC power into DC power and outputs it to the detection system, and then the machine-side inverter 52 converts the DC power into AC power and outputs it to the motor 3 under test. The rotation of the shaft of the motor 3 under test drives the shaft of the load motor 4, and the motor 3 under test works in the electric state, driving the load motor 4 to rotate, so that the load motor 4 is in the power generation state. The AC power generated by the load motor 4 is converted into DC power by the machine-side rectifier 54 and output to the detection system, and then the grid-side inverter 53 converts the DC power into AC power and outputs it to the grid-side rectifier 51, so that the power consumption and power generation of the two motors form a cycle. The power grid 1 supplements the loss of the power circulation loop.

[0045] In this embodiment, the machine-side rectifier 54 is a common three-phase two-level topology, and the three-phase AC current of the machine-side rectifier 54 is i a 、i b 、i c , the DC bus voltage is controlled by the rectifier to be u dc In other embodiments, the machine-side rectifier 54 may also be any AC / DC conversion topology.

[0046] Since the capacity of the power grid 1 is smaller than that of the power circulation loop, the power circulation loop generates negative damping at low frequencies, causing the power circulation loop to generate low-frequency oscillations. The oscillations may cause the system to be unable to operate to the rated power.

[0047] In order to suppress the low-frequency oscillation generated by the power circulation loop, such as Figure 2 As shown, a trap is connected in series before the active current instruction of the machine-side rectifier 54 to damp the current on the active current component in the transmission path to form a new active current. The machine-side rectifier 54 includes a voltage loop controller and a current loop controller, and the trap is connected in series between the voltage loop controller and the current loop controller.

[0048] In this embodiment, the transfer function of the notch filter is 1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 ), where ω0 is the center angular frequency of the notch filter, ξ is the notch bandwidth, ξ ranges from 0 to 1, N is the notch depth, N ranges from 0 to 1, and s is the Laplace transform operator; ω0 = 2πf0, where f0 is the center frequency of the notch filter, ω0 is the center angular frequency of the notch filter, and f0 ranges from 0.5 to 1.5 times f r , f r is the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform. In this embodiment, the notch bandwidth ξ is 0.4, the notch depth N is 0.6, and f r is 15Hz,f0 is 15Hz.

[0049] When there is no series trap, the active current command output by the voltage loop controller of the machine-side rectifier 54 is i d.Ref.Ori , the active current command i output by the voltage loop controller d.Ref.Ori A notch filter is added in the latter stage, and the output of the notch filter is used as the active current instruction i d.Ref ,i d.Ref =i d.Ref.Ori ×[1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 )].

[0050] like Figure 2 As shown, specifically, the DC voltage is sampled to obtain the DC bus voltage u dc , the initial active current command i is obtained through the voltage loop controller d.Ref.Ori , and then pass through the notch filter to obtain the new active current command i d.Ref , as the input of the current loop controller. In addition, the three-phase current sampling obtains the AC side current i a 、i b 、i c , and after abc / dq coordinate transformation, the current i in the synchronous coordinate system is obtained d 、i q , through the current loop controller, the modulation wave m in the synchronous coordinate system is obtained d 、m q , after dq / abc coordinate transformation, we get the three-phase modulation wave m a 、m b 、m c , and compared with the carrier in the modulation and drive module to generate a drive signal to drive the converter topology to achieve power conversion.

[0051] The present application also provides a method for suppressing power oscillation of a motor-to-drag test platform.

[0052] like Figure 3 As shown, a method for suppressing power oscillation of a motor-to-drag test platform comprises:

[0053] Step 1, such as Figure 4 and Figure 5 As shown, the Bode diagram of the closed-loop transfer function of the DC current disturbance of the machine-side rectifier to the AC current output under the initial working condition is drawn, that is, the Bode diagram 6 of the closed-loop transfer function of the DC current disturbance of the machine-side rectifier to the AC current output under the condition of no series notch filter, as well as the waveform diagram of current and power. The DC voltage loop bandwidth is 10Hz, and the attenuation at 15Hz is only -3dB. Combined with the state 0.2 seconds (s) ago in the current and power waveform diagram, the envelope of the three-phase current has low-frequency oscillation, and correspondingly, the power has a low-frequency oscillation of 15Hz. This oscillation may cause the system to fail to operate to rated power.

[0054] Step 2: Identify the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform from the closed-loop transfer function Bode diagram 6 of the DC current disturbance of the machine-side rectifier to the AC current output without a series trap. The frequency f of the low-frequency oscillation of the power of the motor-to-drag test platform is r is 15Hz.

[0055] Step 3: Connect the above-mentioned trap filter in series before the active current instruction of the generator side rectifier. The transfer function of the series trap filter is 1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 ), resulting in significant attenuation at the oscillation frequency of 15 Hz. ω0 = 2πf0, where f0 is in the range of 0.5-1.5 times f r , the range of notch bandwidth ξ is 0-1, and the range of notch depth N is 0-1. Figure 4 As shown, the closed-loop transfer function Bode diagram 6 of the DC current disturbance of the machine-side rectifier to the AC current output after the series notch filter is drawn.

[0056] Step 4: Adjust the parameters of the notch filter until the absolute value of the difference between the resonant peaks of the two closed-loop transfer function Bode plots is 0-1dB. If the absolute value of the difference between the resonant peaks of the two closed-loop transfer function Bode plots is greater than 1dB, increase f0 or reduce the DC voltage loop bandwidth; adjust f0 to 15Hz and reduce the DC voltage loop bandwidth to 10Hz to obtain Figure 4 The Bode diagram of the closed-loop transfer function of the DC current disturbance of the machine-side rectifier to the AC current output after the series notch filter. The absolute value of the difference between the resonant peaks of the two closed-loop transfer function Bode diagrams is 0-1dB.

[0057] Step 5, test the low-frequency oscillation of the towing platform to obtain the attenuation degree of the low-frequency oscillation; when the attenuation degree of the low-frequency oscillation reaches the design requirement, the process ends; when the attenuation degree of the low-frequency oscillation does not meet the design requirement, the parameters of the notch filter are adjusted in two stages until the difference between the resonant peaks of the two closed-loop transfer function Bode diagrams reaches the required value and the attenuation degree of the low-frequency oscillation reaches the design requirement.

[0058] First, when the notch bandwidth ξ is set to 0.1 and the notch depth N is set to 0.1, f0 is 15Hz. After the test, the low-frequency oscillation of the motor towing the test platform is limited. When the notch bandwidth ξ is further increased to 0.4 and the notch depth N is increased to 0.6, f0 remains unchanged. The Bode plot of the closed-loop transfer function is as follows: Figure 4 As shown, in f r The attenuation at 15Hz increases from -2.5dB to -8dB, meeting the design requirements. Correspondingly, Figure 5 ,After 0.2s ,the 15Hz ,power oscillation of the motor-towed test platform was significantly ,suppressed.

[0059] The low-frequency oscillation of the motor-to-motor test platform is suppressed, avoiding motor shaft fatigue failure and converter fault protection or failure, so that the motor-to-motor test platform can operate at full power under a weak grid with limited capacity, and test various technical indicators of the converter and motor to the maximum extent.

[0060] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A motor-to-motor test platform, comprising a power grid and a power circulation loop, wherein the power circulation loop comprises a motor to be tested, a load motor and a control system, characterized in that: The control system includes a machine-side rectifier electrically connected to a load motor, wherein a trap is connected in series before the active current instruction of the machine-side rectifier to damp the current on the active current component in the transmission path, and the transfer function of the trap is 1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 ), where ω0 is the central angular frequency of the notch filter, ξ is the notch bandwidth, N is the notch depth, and s is the Laplace transform operator; The motor-to-motor test platform is implemented based on a power oscillation suppression method of the motor-to-motor test platform. The specific steps of the method include: Draw the Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output without a series notch filter; Identify the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform from the Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output under the initial working condition; A notch filter is connected in series before the active current command of the machine-side rectifier, and a Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output after the notch filter is connected in series is drawn; Adjust the parameters of the notch filter until the difference between the resonant peaks of the two closed-loop transfer function Bode plots reaches the required value. The transfer function of the notch filter is 1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 ), where ω0 is the central angular frequency of the notch filter, ξ is the notch bandwidth, N is the notch depth, and s is the Laplace transform operator; The method of performing two-stage adjustment on the parameters of the notch filter is to reduce f0, increase ξ, increase N or any one or more thereof, wherein f0 is the center frequency of the notch filter; Adjust the parameters of the notch filter until the absolute value of the difference between the resonant peaks of the two closed-loop transfer function Bode plots is 0-1dB; After adjusting the parameters of the notch filter to the required value of the difference between the resonant peaks of the Bode diagrams of the two closed-loop transfer functions, the following steps are also included: testing the low-frequency oscillation of the towing platform to obtain the attenuation degree of the low-frequency oscillation; When the attenuation degree of the low-frequency oscillation reaches the design requirement, the process ends; When the attenuation degree of the low-frequency oscillation does not meet the design requirements, the parameters of the notch filter are adjusted in two stages until the difference between the resonant peaks of the two closed-loop transfer function Bode diagrams reaches the required value and the attenuation degree of the low-frequency oscillation reaches the design requirements.

2. The motor pair test platform according to claim 1, characterized in that: The capacity of the power grid is smaller than the capacity of the power circulation loop.

3. The motor towing test platform according to claim 1, characterized in that: The machine-side rectifier comprises a voltage loop controller and a current loop controller, and the trap is connected in series between the voltage loop controller and the current loop controller.

4. A method for suppressing power oscillation of a motor-to-motor test platform, characterized in that: The steps include: Draw the Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output without a series notch filter; Identify the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform from the Bode diagram of the closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output under the initial working condition; A notch filter as claimed in claim 3 is connected in series before the active current instruction of the machine-side rectifier, and a Bode diagram of a closed-loop transfer function from the DC current disturbance of the machine-side rectifier to the AC current output after the notch filter is connected in series is drawn; Adjust the parameters of the notch filter until the difference between the resonant peaks of the two closed-loop transfer function Bode plots reaches the required value. The transfer function of the notch filter is 1–2ξω0s·N / (s 2 +2ξω0s+ω0 2 ), where ω0 is the central angular frequency of the notch filter, ξ is the notch bandwidth, N is the notch depth, and s is the Laplace transform operator; The method of performing two-stage adjustment on the parameters of the notch filter is to reduce f0, increase ξ, increase N or any one or more thereof, wherein f0 is the center frequency of the notch filter; Adjust the parameters of the notch filter until the absolute value of the difference between the resonant peaks of the two closed-loop transfer function Bode plots is 0-1dB; After adjusting the parameters of the notch filter to the required value of the difference between the resonant peaks of the Bode diagrams of the two closed-loop transfer functions, the following steps are also included: testing the low-frequency oscillation of the towing platform to obtain the attenuation degree of the low-frequency oscillation; When the attenuation degree of the low-frequency oscillation reaches the design requirement, the process ends; When the attenuation degree of the low-frequency oscillation does not meet the design requirements, the parameters of the notch filter are adjusted in two stages until the difference between the resonant peaks of the two closed-loop transfer function Bode diagrams reaches the required value and the attenuation degree of the low-frequency oscillation reaches the design requirements.

5. The method for suppressing power oscillation of a motor-to-motor test platform according to claim 4, characterized in that: ω0=2πf0, where f0 is in the range of 0.5-1.5 times f r , ω0 is the central angular frequency of the notch filter, f r is the frequency of the low-frequency oscillation of the power of the motor-to-drag test platform, the range of the notch bandwidth ξ is 0-1, and the range of the notch depth N is 0-1.

6. The method for suppressing power oscillation of a motor-to-motor test platform according to claim 4, characterized in that: The method of adjusting the parameters of the notch filter is to increase f0 or reduce the DC voltage loop bandwidth.

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