An energy feedback and harmonic suppression method for electric vehicle electric drive system loading test room

Abstract

The present application relates to the electric automobile electric drive system test technical field, disclose a kind of for electric automobile electric drive system loading test laboratory energy feedback and harmonic suppression method.This method obtains loading test operating condition instruction, generates load mutation pre-registration record according to the dynamic operating condition change information and switching time of adjacent operating condition section;Start sampling window before and after switching time, collect the operating state parameters of variable-frequency feeding network and the electrical signal of grid-connected point;Extract current harmonic component and construct operating condition harmonic fingerprint table according to the component and pre-registration record;According to the fingerprint table, generate at least containing grid-connected side compensation sub-instruction and loading side smoothing sub-instruction Double-end collaborative control instruction and execute.The present application effectively reduces the control response lag of energy feedback and harmonic suppression during operating condition alternation.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle electric drive system testing technology, and in particular to an energy feedback and harmonic suppression method for an electric vehicle electric drive system loading test chamber. Background Technology

[0002] In the field of electric vehicle testing technology, electric drive system loading test chambers are typically used to perform load tests on the operating status of electric drive systems under different speeds, torques, and dynamic operating conditions. These loading test chambers generally include a test bench, a test motor, the electric drive system under test, and a variable frequency power supply network for energy transfer. During testing, the test motor and the electric drive system under test form a tandem structure. The test bench controls the test motor to apply mechanical loads to the electric drive system under test according to the loading test command, and the operating status of the electric drive system under test under different operating conditions is evaluated by collecting parameters such as speed, torque, voltage, and current.

[0003] In existing technologies, electric vehicle powertrain testing devices typically consist of a dynamometer, a test motor, a motor controller, a DC power supply or a power battery pack, and an energy feedback device. For example, the electric vehicle powertrain testing device disclosed in CN106441925A can control the testing process through testing software, simulating operating conditions such as constant speed, constant torque, and low-speed start-up. During energy feedback testing, the test motor acts as a generator, feeding the generated electrical energy back to the power grid or power battery pack through the energy feedback device. The energy feedback device can also filter and compensate for reactive power in the testing system. This type of solution can achieve operating condition simulation and energy feedback during electric vehicle powertrain testing, and is suitable for bench testing scenarios of electric vehicle powertrains or electric drive systems.

[0004] However, in actual testing of electric vehicle electric drive systems in a test laboratory, to simulate dynamic driving states such as rapid acceleration, rapid deceleration, sudden load changes, and reverse switching of speed and torque, the load test command typically includes multiple time-sequential condition segments. Adjacent condition segments need to switch between target speeds and target torques within a short period. During this alternation of conditions, the load state of the test motor and the regenerative energy output state will change abruptly with the test conditions, and the voltage state of the DC bus, as well as the voltage and current signals at the grid connection point, will also experience transient changes.

[0005] Existing energy feedback devices or grid-connected converters typically rely on real-time voltage and current signals acquired at the grid connection point, along with the DC bus status, for closed-loop control. Their control logic primarily responds to existing electrical quantity changes. This type of control lacks a direct correspondence with the load test condition commands at the test bench front end, making it difficult to proactively predict upcoming load surges before the transition between current and next operating conditions. Because the operating condition information at the test end and the electrical feedback information at the grid connection end are disconnected, the grid-connected converter can usually only perform compensation calculations after an abnormal change in the grid connection point current has already occurred, leading to a lag in compensation response during load test condition transitions.

[0006] The aforementioned lag in compensation response makes it difficult to promptly correlate transient current harmonics generated during loading tests with specific test condition changes. This results in the grid-connected side compensation control and the test-side loading control being unable to coordinate their execution around the same alternating operating condition. When operating condition switching is frequent or the target speed and target torque vary significantly, there is a lack of unified operating condition timing correlation between the loading execution process of the test bench, the energy feedback process of the DC bus, and the harmonic suppression process at the grid connection point. This, in turn, affects the continuity of the electric vehicle drive system loading test process and the traceability of the test results.

[0007] Therefore, how to coordinate the changes in load test conditions, the load status of the accompanying motor, the DC bus energy feedback status, and the changes in the electrical quantities at the grid connection point during the load test of the electric drive system of an electric vehicle under the same test sequence, so as to reduce the response lag between energy feedback control and harmonic suppression control during the alternation of operating conditions, is a technical problem that needs to be solved in the load test laboratory of the electric drive system of an electric vehicle. Summary of the Invention

[0008] To overcome the aforementioned technical deficiencies, the present invention aims to provide an energy feedback and harmonic suppression method for a load testing laboratory of an electric vehicle drive system. This invention employs a technical solution that generates a pre-registered record of load mutations based on load test condition commands, and constructs a harmonic fingerprint table of the test conditions using sampling windows before and after the switching time. This, in turn, generates and executes a dual-end coordinated control command containing grid-connected side compensation sub-commands, load-side smoothing sub-commands, and feedback window sub-commands. This allows for coordinated processing of changes in load test conditions, load parameters of the test motor, DC bus voltage status, and changes in electrical quantities at the grid connection point within the same test sequence, thereby reducing the response lag between energy feedback control and harmonic suppression control during condition transitions.

[0009] This invention discloses an energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system. The loading test chamber includes a frequency converter power supply network, which includes a test-side frequency converter, a DC bus, and a grid-connected converter connected to the AC power grid. The grid-connected converter is connected to the AC power grid through a grid connection point. The method includes the following steps:

[0010] Obtain the load test condition instruction, which contains multiple condition segments arranged in chronological order. Determine two consecutive condition segments as adjacent condition segments, determine the time of condition alternation between adjacent condition segments as the switching time, and generate a load mutation pre-registration record based on the dynamic condition change information of adjacent condition segments and the switching time.

[0011] Before the switching time, the pre-sampling window is started, and after the switching time, the response sampling window is started, and the operating status parameters of the frequency converter power supply network and the electrical signals of the grid connection point are collected.

[0012] Harmonic components are extracted from the electrical signals collected in the pre-sampling window and the response sampling window, and a working condition harmonic fingerprint table is constructed based on the extracted current harmonic components. The working condition harmonic fingerprint table associates the current harmonic components with the pre-registration record of load mutation.

[0013] The dual-end collaborative control instructions are generated based on the operating condition harmonic fingerprint table. The dual-end collaborative control instructions include at least the grid-connected side compensation sub-instruction for controlling the grid-connected converter and the loading side smoothing sub-instruction for controlling the test-side frequency converter.

[0014] Execute dual-end coordinated control commands to coordinate the response of converter control and frequency converter load control during operating condition alternation.

[0015] Preferably, the loading test chamber also includes a test bench, a test motor, the electric drive system under test, and a data acquisition controller. The test motor and the electric drive system under test are connected in a toggle connection through the test bench, and the frequency converter on the test side is connected to the test motor. Each operating condition segment includes target speed, target torque, and operating condition timing markers. Dynamic operating condition change information includes the direction of target speed change and the direction of target torque change in adjacent operating condition segments. The operating status parameters of the frequency converter power supply network and the electrical signals of the grid connection point are collected, including: synchronously collecting the operating parameters of the electric drive system under test, the loading parameters of the test motor, the voltage status of the DC bus, and the voltage and current signals of the grid connection point through the data acquisition controller.

[0016] Preferably, adjacent operating segments include the current operating segment and the next operating segment; the load mutation pre-registration record includes the load mutation type, switching time, operating condition timing mark of the current operating segment, and operating condition timing mark of the next operating segment; generating the load mutation pre-registration record includes: reading the target speed, target torque, and end time of the current operating segment; reading the target speed, target torque, and start time of the next operating segment; determining the load mutation type based on the direction of change of target speed and the direction of change of target torque between the current operating segment and the next operating segment; and writing the load mutation type, switching time, operating condition timing mark of the current operating segment, and operating condition timing mark of the next operating segment into the load mutation pre-registration record.

[0017] Preferably, the load change type includes torque increase type, torque decrease type, target speed increase type, target speed decrease type, speed and torque change in the same direction type, speed and torque change in opposite direction type, and regenerative load switching type; the regenerative load switching type is determined by the speed direction of the accompanying motor, the electromagnetic torque direction of the accompanying motor, and the voltage change direction of the DC bus.

[0018] Preferably, the start time of the pre-sampling window is earlier than the switching time, and the start time of the response sampling window is the switching time. The data acquisition controller records the sampling data in the pre-sampling window and the response sampling window under the same time reference, and writes the sampling data into the window data buffer corresponding to the load mutation pre-registration record.

[0019] Preferably, constructing a harmonic fingerprint table for operating conditions includes: performing spectral analysis on the current signal of the grid-connected point collected within the pre-sampling window, extracting each harmonic component, and generating steady-state background harmonic data with harmonic order markers; performing spectral analysis on the current signal of the grid-connected point collected within the response sampling window, extracting each harmonic component, and generating abrupt response harmonic data with harmonic order markers; subtracting the abrupt response harmonic data from the steady-state background harmonic data according to the same harmonic order to obtain load abrupt related harmonic data; and writing the load abrupt related harmonic data, the load abrupt type, and the switching time into the harmonic fingerprint table for operating conditions.

[0020] Preferably, the load change-related harmonic data includes the harmonic number, the harmonic occurrence period, the harmonic current direction mark extracted based on the current harmonic component of the grid connection point, the voltage phase interval determined based on the voltage signal of the grid connection point, and the corresponding load change type; the harmonic occurrence period is divided into the pre-switching period, the switching period, and the post-switching period according to the switching time.

[0021] Preferably, the dual-end collaborative control command further includes: a feedback window sub-command determined based on the voltage state of the DC bus; generating dual-end collaborative control commands according to the operating condition harmonic fingerprint table, including: generating a grid-connected side compensation sub-command based on the harmonic number, harmonic current direction mark, and voltage phase interval; generating a load-side smoothing sub-command based on the load mutation type, harmonic occurrence time, and loading parameters of the accompanying motor; generating a feedback window sub-command based on the DC bus voltage state, load mutation type, and switching time; and binding the grid-connected side compensation sub-command, the load-side smoothing sub-command, and the feedback window sub-command to the load mutation pre-registration record.

[0022] Preferably, the grid-connected side compensation sub-instruction includes a compensation current instruction, a compensation execution start time, and a compensation execution termination time; the loading side smoothing sub-instruction includes a loading slope switching instruction, a loading hold period, and a loading recovery time; and the feedback window sub-instruction includes a feedback allow period, a feedback limit period, and a feedback path marker.

[0023] Preferably, the execution of dual-end collaborative control instructions includes: the data acquisition controller keeping the load test condition instruction unchanged, controlling the frequency converter on the test side to perform the transition load process according to the load-side smoothing sub-instruction, controlling the grid-connected converter to perform the compensation current output process according to the compensation current instruction in the grid-connected compensation sub-instruction, and controlling the grid-connected converter to perform the feedback time period constraint process according to the feedback window sub-instruction, so as to generate the test results of the electric drive system under test.

[0024] Preferably, the loading-side smoothing sub-command does not change the target speed and target torque of the next operating condition segment, and the loading-side smoothing sub-command limits the loading slope switching process corresponding to the loading slope switching command when the monitored motor enters the next operating condition segment from the current operating condition segment; the grid-connected side compensation sub-command does not change the loading slope switching process, and the grid-connected side compensation sub-command limits the compensation current output process of the grid-connected converter during the feedback allowable period.

[0025] Preferably, after completing the execution of the dual-end collaborative control command, the data acquisition controller starts the residual sampling window after responding to the sampling window, generates residual harmonic data based on the current signal of the grid connection point in the residual sampling window, and writes the residual harmonic data into the residual fingerprint record corresponding to the load mutation pre-registration record.

[0026] Preferably, the data acquisition controller matches the residual fingerprint record with the operating condition harmonic fingerprint table. When the two correspond to the same load mutation type and the execution record of the same feedback window sub-instruction, the controller updates the harmonic occurrence time, compensation execution start time, compensation execution end time, and feedback allowed time period corresponding to the load mutation type in the operating condition harmonic fingerprint table.

[0027] Preferably, the regenerative load switching type has a preset feedback allowable state. When executing the feedback window sub-instruction, if the voltage state of the DC bus does not correspond to the preset feedback allowable state, the data acquisition controller generates a condition holding instruction and sends the condition holding instruction to the test-side inverter and the grid-connected inverter. The condition holding instruction includes the current load holding period, the grid-connected side feedback prohibition period, and the resampling flag.

[0028] Preferably, after executing the operating condition hold command, the data acquisition controller re-acquires the voltage and current signals of the grid connection point according to the resampling mark, and generates replacement background harmonic data based on the re-acquired voltage and current signals; the replacement background harmonic data is used to replace the original steady-state background harmonic data in the calculation of load change-related harmonic data when the same type of load change occurs in the future.

[0029] Preferably, the test results include load mutation pre-registration records, operating condition harmonic fingerprint tables, dual-end collaborative control commands, residual fingerprint records, and DC bus energy flow records, grid connection point voltage and current records, and speed and torque response records of the tested electric drive system generated based on synchronously acquired sampling data; the test results are stored in association according to operating condition timing marks, switching times, and load mutation types.

[0030] Compared with existing technologies, the above technical solution has the following advantages:

[0031] I. This invention generates a pre-registration record of load mutation based on the load test condition command, and combines the pre-registration record of load mutation with the sampling window before and after the switching time. This enables the alternation process of the operating conditions in the load test of the electric drive system of electric vehicles to be identified and recorded under the same test sequence. This avoids the energy feedback control and harmonic suppression control from relying solely on the already occurred changes in the electrical quantity at the grid connection point for passive response, and helps to reduce the control response lag during the alternation of operating conditions.

[0032] Second, this invention constructs a harmonic fingerprint table for operating conditions, which associates the load change type, switching time, current harmonic components at the grid connection point, and corresponding test operating condition information. This allows the harmonic changes caused by sudden changes in operating conditions during the load test to correspond to the specific alternation process of the test operating conditions, which is beneficial to improving the matching between harmonic suppression control and the load test process of the electric drive system.

[0033] Third, by generating dual-end collaborative control commands including grid-connected side compensation sub-commands, loading side smoothing sub-commands, and feedback window sub-commands, this invention enables the compensation current output of the grid-connected converter, the transition loading process of the test-side inverter, and the energy feedback window of the DC bus to be executed collaboratively around the same load change pre-registration record, thereby reducing the mutual influence between load state changes, DC bus voltage fluctuations, and transient harmonics at the grid connection point.

[0034] Fourth, this invention sets a residual sampling window after the response sampling window and forms a residual fingerprint record based on the residual harmonic data. It updates the harmonic occurrence time, compensation execution start time, compensation execution end time and feedback allowable time period in the operating condition harmonic fingerprint table, so that when the same type of load mutation occurs again, the control parameters can be adjusted based on the historical execution results, thereby improving the control adaptability during continuous loading test.

[0035] Fifth, this invention links and stores load mutation pre-registration records, operating condition harmonic fingerprint tables, dual-end collaborative control commands, residual fingerprint records, and test records generated based on synchronously acquired sampling data according to operating condition timing marks, switching times, and load mutation types. This enables the operating condition changes, energy feedback processes, harmonic suppression processes, and test results during the load testing of electric vehicle electric drive systems to be traced back to each other, which is beneficial to improving the completeness and consistency of test result analysis. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the system hardware topology for a loading test chamber for an electric vehicle electric drive system provided in an embodiment of the present invention;

[0037] Figure 2 The main flowchart of the energy feedback and harmonic suppression method for the electric drive system loading test chamber of the present invention is provided in the embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the timing control of alternating operating conditions and sampling windows provided in an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of the dual-end cooperative control signal waveform provided in an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of the data structure and matching logic of the operating condition harmonic fingerprint table provided in an embodiment of the present invention. Detailed Implementation

[0041] The following description, in conjunction with the accompanying drawings, further illustrates this embodiment. It should be understood that the following embodiments are used to illustrate the implementation of this technical solution and are not intended to limit the scope of protection of this technical solution. Where there is no conflict, the technical features in the following embodiments can be combined with each other.

[0042] like Figure 1As shown, this embodiment provides an energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle's electric drive system. The loading test chamber includes a test bench, a test motor, the electric drive system under test, a data acquisition controller, and a variable frequency drive (VFD) power supply network. The VFD power supply network includes a test-side VFD, a DC bus, a grid-connected converter, and a grid connection point connected to the AC power grid. The grid-connected converter is connected to the AC power grid through the grid connection point. The test bench supports the test motor and the electric drive system under test. The test motor and the electric drive system under test are mechanically connected. The test-side VFD is electrically connected to the test motor and to the grid-connected converter via the DC bus. The grid-connected converter is connected to the AC power grid through the grid connection point. The data acquisition controller is communicatively connected to the test bench, the test-side inverter, the DC bus, the grid-connected converter, and the grid connection point, respectively. It is used to collect the operating parameters of the electric drive system under test, the loading parameters of the test motor, the voltage status of the DC bus, and the voltage and current signals of the grid connection point. It is also used to send control commands to the test-side inverter and the grid-connected converter.

[0043] In this embodiment, the data acquisition controller can be implemented using a real-time controller, such as a controller structure including a field-programmable gate array (FPGA) and a digital signal processing unit (DSP). The FPGA is used to perform high-speed synchronous acquisition of the voltage signal at the grid connection point, the current signal at the grid connection point, and the voltage state of the DC bus. The DSP is used to perform operating condition segment identification, harmonic component extraction, construction of the operating condition harmonic fingerprint table, and generation of dual-end collaborative control commands. To capture transient electrical quantity changes during the alternation of loading test operating conditions, the sampling frequency of the voltage and current signals at the grid connection point can be set to 20kHz, and the sampling frequency of the speed, torque, and DC bus voltage state can be set to 10kHz. Each acquisition channel is controlled by the same sampling clock or synchronous trigger signal, and the data acquisition controller adds a unified timestamp to the sampled data, so that sampled data from different sources can correspond under the same test timing. The same sampling clock can be provided by the internal clock source of the data acquisition controller or by the main control clock source of the loading test chamber; the synchronous trigger signal can be triggered by the operating condition timing mark in the loading test operating condition command.

[0044] like Figure 2As shown, the energy feedback and harmonic suppression method in this embodiment includes the following process: First, the load test condition command of the electric vehicle's electric drive system is acquired. The load test condition command contains multiple condition segments arranged in chronological order, each including a target speed, a target torque, and a condition timing marker. The data acquisition controller determines two consecutive condition segments as adjacent condition segments, which include the current condition segment and the next condition segment. The data acquisition controller determines the condition transition time between the end time of the current condition segment and the start time of the next condition segment as the switching time, and generates a load mutation pre-registration record based on the target speed change direction, target torque change direction, and switching time of the adjacent condition segments. The load mutation pre-registration record includes the load mutation type, switching time, the condition timing marker of the current condition segment, and the condition timing marker of the next condition segment.

[0045] In one specific implementation, the target speed of the current operating condition segment in the load test command is 3000 rpm, the target torque is 100 Nm, and the operating condition timing is marked as S1; the target speed of the next operating condition segment is 3000 rpm, the target torque is -50 Nm, and the operating condition timing is marked as S2. The end time of the current operating condition segment is 5.0 s, and the start time of the next operating condition segment is 5.0 s. The data acquisition controller determines 5.0 s as the switching time. Since the target speed remains unchanged, the target torque changes from 100 Nm to -50 Nm, and the test motor switches from absorbing mechanical work to regenerative electrical energy output, the data acquisition controller determines this load change type as regenerative load switching type and records the switching time 5.0 s, the operating condition timing mark S1 of the current operating condition segment, and the operating condition timing mark S2 of the next operating condition segment in the load change pre-registration record.

[0046] In another implementation, the load change type can include torque increase type, torque decrease type, target speed increase type, target speed decrease type, speed and torque change in the same direction type, speed and torque change in opposite direction type, and regenerative load switching type. Specifically, the torque increase type corresponds to a target torque in the next operating condition being greater than the target torque in the current operating condition; the torque decrease type corresponds to a target torque in the next operating condition being less than the target torque in the current operating condition; the target speed increase type corresponds to a target speed in the next operating condition being greater than the target speed in the current operating condition; the target speed decrease type corresponds to a target speed in the next operating condition being less than the target speed in the current operating condition; the speed and torque change in the same direction type corresponds to a target speed change direction that is the same as the target torque change direction; the speed and torque change in opposite direction type corresponds to a target speed change direction that is opposite to the target torque change direction. The regenerative load switching type is determined by the speed direction of the monitored motor, the electromagnetic torque direction of the monitored motor, and the voltage change direction of the DC bus. When the speed direction of the monitored motor is opposite to the electromagnetic torque direction, and the voltage change direction of the DC bus is increasing, the data acquisition controller can determine the corresponding load change type as regenerative load switching type.

[0047] like Figure 3 As shown, after determining the switching time, the data acquisition controller starts a pre-sampling window before the switching time and a response sampling window after the switching time. In this embodiment, the switching time is 5.0s, the pre-sampling window is set to 100ms before the switching time, i.e., 4.90s to 5.00s; the response sampling window is set to 200ms after the switching time, i.e., 5.00s to 5.20s; after completing the execution of the dual-end coordinated control command, a residual sampling window can also be started, set to 5.20s to 5.30s. The data acquisition controller records the sampling data in the pre-sampling window and the response sampling window under the same time reference, and writes the sampling data into the window data buffer corresponding to the load mutation pre-registration record. In order to meet the data length required for harmonic component extraction, the time length of the pre-sampling window, the response sampling window, and the residual sampling window can cover an integer multiple of the fundamental period of the AC power grid; when the window length is not an integer multiple of the fundamental period, the data acquisition controller can perform synchronous resampling based on the voltage signal at the grid connection point.

[0048] Within the pre-sampling window and the response sampling window, the data acquisition controller synchronously acquires the operating parameters of the tested electric drive system, the loading parameters of the accompanying motor, the voltage status of the DC bus, and the voltage and current signals at the grid connection point. The operating parameters of the tested electric drive system may include the actual speed, actual torque, input current, and bus voltage of the tested motor. The loading parameters of the accompanying motor may include its speed, electromagnetic torque, loading slope, and output current of the inverter on the accompanying side. The voltage status of the DC bus may include the real-time DC bus voltage, the direction of DC bus voltage change, and the amplitude of DC bus voltage change. The voltage and current signals at the grid connection point may include three-phase voltage sampling signals and three-phase current sampling signals.

[0049] In this embodiment, the data acquisition controller extracts harmonic components from the current signals of the grid-connected point collected in the pre-sampling window and the response sampling window to obtain the current harmonic components of the grid-connected point. Based on the pre-sampling window, the response sampling window, and the current harmonic components of the grid-connected point, a working condition harmonic fingerprint table is constructed. This working condition harmonic fingerprint table binds the current harmonic components of the grid-connected point to a pre-registration record of load mutations. Specifically, the data acquisition controller performs spectral analysis on the current signals of the grid-connected point collected in the pre-sampling window, extracts each harmonic component, and generates steady-state background harmonic data with harmonic order markers. It also performs spectral analysis on the current signals of the grid-connected point collected in the response sampling window, extracts each harmonic component, and generates mutation response harmonic data with harmonic order markers. The mutation response harmonic data and the steady-state background harmonic data are then subtracted according to the same harmonic order to obtain load mutation-related harmonic data. Finally, the load mutation-related harmonic data, the load mutation type, and the switching time are written into the working condition harmonic fingerprint table.

[0050] The operating condition harmonic fingerprint table may include load mutation pre-registration records, steady-state background harmonic data, mutation response harmonic data, load mutation-related harmonic data, execution records of grid-connected side compensation sub-instructions, execution records of load-side smoothing sub-instructions, execution records of feedback window sub-instructions, and residual fingerprint records. Therefore, the operating condition harmonic fingerprint table is not only used to record load mutation-related harmonic data, but also to establish associations between harmonic data and corresponding control commands and execution results.

[0051] In a specific spectrum analysis method, the data acquisition controller uses Fast Fourier Transform (FFT) to extract each harmonic component. To ensure accurate correspondence between harmonic orders and spectral frequencies, the pre-sampling window, response sampling window, and residual sampling window can be truncated according to the integer period of the AC power grid's fundamental frequency. When the start and end times of the window cannot directly meet the integer period truncation requirement, the data acquisition controller can determine the fundamental period based on the voltage signal at the grid connection point and synchronously resample the sampled data. For the current signal at the grid connection point within any sampling window, the spectral data at the corresponding frequency point can be obtained using the following formula:

[0052]

[0053] in, Indicates the first The complex value of the current spectrum at each frequency point is expressed in amperes (A). Indicates the number of samples within the sampling window. Each current sample value is in amperes (A). This indicates the total number of sampling points within the sampling window; Indicates the frequency point number; Represents the imaginary unit; The above symbols represent the sampling point number only in this calculation formula and do not directly replace the technical names in the specification.

[0054] For the The magnitude of the harmonic current can be obtained from the following formula:

[0055]

[0056] in, Indicates the first The amplitude of the second harmonic current, in amperes (A); Indicates the first The complex value of the current spectrum at the frequency corresponding to the subharmonic is expressed in A. This indicates the total number of sampling points within the sampling window; Indicates the harmonic order.

[0057] To distinguish between harmonic changes caused by load mutations and steady-state background harmonics already present in the pre-sampling window, this implementation uses a corresponding subtraction method to generate load mutation-related harmonic data. For mutation response harmonic data and steady-state background harmonic data of the same harmonic order, a complex difference method can be used for calculation:

[0058]

[0059] in, Indicates the first The load mutation associated with the next harmonic is a complex value, in amperes (A). Indicates the first response within the sampling window The complex value of the abrupt response harmonic corresponding to the second harmonic, in Å; Indicates the first sampling window The steady-state background harmonic complex value corresponding to the subharmonic is expressed in A; This indicates the harmonic order. Using the complex difference method can simultaneously retain harmonic amplitude and phase information, which facilitates subsequent determination of harmonic current direction markings and voltage phase intervals.

[0060] In this embodiment, the total harmonic distortion rate of the grid connection point can also be calculated according to the following formula, which is used to record the changes in the electrical quantities of the grid connection point during the test process:

[0061]

[0062] in, Indicates the total harmonic distortion rate; Indicates the first The amplitude of the second harmonic current, in amperes (A); This represents the amplitude of the fundamental current, expressed in amperes (A). Indicates the highest harmonic order involved in the calculation; Indicates the harmonic order.

[0063] Table 1 shows a set of example data from the operating condition harmonic fingerprint table under the following conditions: a switching time of 5.0s, a target speed of 3000rpm and a target torque of 100Nm in the current operating condition segment, and a target speed of 3000rpm and a target torque of -50Nm in the next operating condition segment.

[0064] Table 1. Example Data Table of Harmonic Fingerprint Representation under Operating Conditions

[0065] Regenerative Loading Switching 5 1.2 3.5 2.3 Injection direction of the power grid 30° to 90° Regenerative Loading Switching 7 0.9 2.9 2 Injection direction of the power grid 90° to 150° Regenerative Load Switching 11 0.4 4.1 3.7 Injection direction of the power grid 150° to 210° Regenerative Loading Switching 13 0.3 3.6 3.3 Injection direction of the power grid 210° to 270°

[0066] The load mutation-related harmonic data in the aforementioned operating condition harmonic fingerprint table includes the harmonic number, harmonic occurrence period, harmonic current direction marker extracted based on the current harmonic component at the grid connection point, voltage phase interval determined based on the voltage signal at the grid connection point, and the corresponding load mutation type. The harmonic occurrence period is divided into the pre-switching period, the immediate switching period, and the post-switching period according to the switching time. For example, if a harmonic component occurs between 4.90s and 5.00s, it is recorded as the pre-switching period; if it occurs within a preset short time range around 5.00s, it is recorded as the immediate switching period; and if it occurs between 5.00s and 5.20s, it is recorded as the post-switching period.

[0067] When determining the harmonic current direction marker, the data acquisition controller uses the fundamental voltage phase at the grid connection point as the reference phase and determines the harmonic current direction marker based on the active component direction of the complex value of the load mutation-related harmonics in the direction of the reference phase. When the active component direction of the corresponding harmonic current component is from the grid-connected converter to the AC grid, the harmonic current direction marker is recorded as the grid injection direction; when the active component direction of the corresponding harmonic current component is from the AC grid to the grid-connected converter, the harmonic current direction marker is recorded as the grid absorption direction. The voltage phase interval can be extracted from the fundamental phase based on the voltage signal at the grid connection point, and the positive zero-crossing point of the fundamental voltage at the grid connection point is taken as the zero phase, divided according to a preset angle range. In this embodiment, a fundamental frequency cycle can be divided into multiple voltage phase intervals such as 0° to 30°, 30° to 90°, 90° to 150°, 150° to 210°, 210° to 270°, 270° to 330°, and 330° to 360°. In other embodiments, other phase interval division methods can be adopted according to the control cycle of the test bench or the control cycle of the grid-connected converter.

[0068] like Figure 5 As shown, after constructing the operating condition harmonic fingerprint table, the data acquisition controller generates dual-end collaborative control commands based on the operating condition harmonic fingerprint table. These dual-end collaborative control commands include a grid-connected side compensation sub-command sent to the grid-connected converter, a load-side smoothing sub-command sent to the test-side inverter, and a feedback window sub-command determined based on the DC bus voltage state. The grid-connected side compensation sub-command, the load-side smoothing sub-command, and the feedback window sub-command are bound to the load mutation pre-registration record. All three sub-commands carry the same operating condition timing flag and the same switching time, enabling them to execute around the same load mutation pre-registration record.

[0069] When generating the grid-connected side compensation sub-command, the data acquisition controller generates the compensation current command based on the harmonic order, harmonic current direction marker, and voltage phase interval. For the first... The subharmonic can be compensated for by the following formula:

[0070]

[0071] in, Indicates the first The complex value of the compensation current corresponding to the subharmonic is expressed in A. Indicates the first The compensation coefficient corresponding to the subharmonic; Indicates the first The load mutation associated with the next harmonic is a complex value, in amperes (A). This indicates the harmonic order. The compensation coefficient can be determined based on the upper limit of the allowable compensation current of the grid-connected converter, the amplitude of the load mutation-related harmonic of the corresponding harmonic order, and the proportion of residual harmonics. The upper limit of the allowable compensation current of the grid-connected converter can be determined by the rated current of the grid-connected converter and the current feedback current. In this embodiment, the compensation coefficients corresponding to the 5th, 7th, 11th, and 13th harmonics can be set to values ​​between 0.85 and 0.95. For example, in the embodiment shown in Table 1, the amplitude of the load mutation-related harmonic corresponding to the 11th harmonic is 3.70A. If the compensation coefficient corresponding to the 11th harmonic is 0.90, then the amplitude of the compensation current corresponding to the 11th harmonic is 3.33A, and the direction of the compensation current is opposite to the direction of the load mutation-related harmonic. The grid-connected compensation sub-instruction can include a compensation current instruction, a compensation execution start time, and a compensation execution end time. For example, the compensation execution start time can be set to 5.00s, and the compensation execution end time can be set to 5.12s.

[0072] When generating the load-side smoothing sub-instruction, the data acquisition controller generates a load slope switching instruction, a load holding period, and a load recovery time based on the load mutation type, harmonic occurrence time, and load parameters of the monitored motor. In this embodiment, the target torque for the current operating condition is 100 Nm, and the target torque for the next operating condition is -50 Nm. If the switching is completed directly within 20 ms, the torque change slope will be large, which may easily lead to a sudden change in the loading state of the monitored motor. The data acquisition controller can set the transition loading time to 80 ms based on the operating condition harmonic fingerprint table and determine the loading slope according to the following calculation formula:

[0073]

[0074] in, This indicates the loading slope, in Nm / s. This indicates the target torque for the next operating condition, in Nm. This indicates the target torque for the current operating condition, expressed in Nm. The transition loading time is expressed in seconds. According to the data in this embodiment, the target torque for the next operating condition is -50 Nm, the target torque for the current operating condition is 100 Nm, and the transition loading time is 0.08 s, resulting in a loading slope of -1875 Nm / s. The data acquisition controller generates a loading slope switching command based on this loading slope and sends it to the frequency converter on the test side, causing the test motor to execute the loading slope switching process when entering the next operating condition from the current operating condition. This loading-side smoothing sub-command does not change the target speed and target torque of the next operating condition; it only limits the transition loading process when the test motor enters the next operating condition.

[0075] When the target speed changes, the data acquisition controller can use the same transient control logic to generate a loading slope switching command corresponding to the target speed. The speed change slope can be determined using the following formula:

[0076]

[0077] in, This represents the slope of the speed change, in rpm / s. Indicates the target speed for the next operating condition, in rpm; This indicates the target speed for the current operating condition, in rpm; This indicates the transition loading time, measured in seconds. Using the above method, the loading-side smoothing sub-command can be applied simultaneously to loading test conditions where the target torque changes, the target speed changes, and both the target speed and target torque change simultaneously.

[0078] When generating the feedback window sub-instruction, the data acquisition controller generates the feedback allowable period, feedback restriction period, and feedback path marker based on the DC bus voltage state, load change type, and switching time. For example, under the operating condition corresponding to regenerative load switching, if the DC bus rated voltage is 650V, and the preset feedback allowable state is that the DC bus real-time voltage is between 620V and 690V, the grid connection point voltage is within the allowable grid connection voltage range of the grid-connected converter, the grid-connected converter has no blocking signal, and the grid-connected converter is in a grid-connectable state, then the data acquisition controller can set 5.02s to 5.15s as the feedback allowable period, 5.00s to 5.02s as the feedback restriction period, and set the feedback path marker to the AC grid feedback path. When the DC bus voltage state does not correspond to the preset feedback allowable state, the data acquisition controller generates an operating condition hold instruction and enters the grid-connected side feedback prohibition period and resampling process.

[0079] like Figure 4 As shown, when executing the dual-end coordinated control command, the data acquisition controller maintains the load test condition command unchanged, controls the frequency converter on the test side to perform the transition loading process according to the load-side smoothing sub-command, controls the grid-connected converter to perform the compensation current output process according to the compensation current command in the grid-connected compensation sub-command, and controls the grid-connected converter to perform the feedback time constraint process according to the feedback window sub-command. Since all three types of sub-commands are bound to the same load change pre-registration record, the grid-connected compensation process, the load-side smoothing process, and the energy feedback window control process can be executed around the same operating condition alternation process. The grid-connected compensation sub-command does not change the load slope switching process, and the load-side smoothing sub-command does not change the target speed and target torque of the next operating condition segment, thus keeping the original test target of the tested electric drive system unchanged.

[0080] After executing the dual-end coordinated control command, the data acquisition controller initiates a residual sampling window after responding to the sampling window. It generates residual harmonic data based on the current signal at the grid connection point within the residual sampling window and writes this data into the residual fingerprint record corresponding to the load mutation pre-registration record. The data acquisition controller matches the residual fingerprint record with the operating condition harmonic fingerprint table. When both records correspond to the same load mutation type and the execution record of the same feedback window sub-instruction, it updates the harmonic occurrence time, compensation execution start time, compensation execution end time, and feedback allowed time period corresponding to that load mutation type in the operating condition harmonic fingerprint table.

[0081] In one specific implementation, the residual harmonic ratio can be calculated according to the following formula:

[0082]

[0083] in, Indicates the first The proportion of residual harmonics corresponding to the subharmonics; Indicates the number of samples within the residual sampling window. The complex value of the residual harmonic corresponding to the second harmonic, in Å; Indicates the first The load mutation associated with the next harmonic is a complex value, in amperes (A). Indicates the harmonic order. When the th harmonic... When the residual harmonic ratio corresponding to the 11th harmonic is greater than a preset residual ratio limit, the data acquisition controller can advance the start time of the compensation execution for the next load mutation type of the same kind, or extend the end time of the compensation execution. In this embodiment, the preset residual ratio limit can be set to 15%. For example, if the residual harmonic ratio corresponding to the 11th harmonic is 18%, the data acquisition controller adjusts the start time of the compensation execution for this load mutation type from 5.00s to 4.995s, and adjusts the end time of the compensation execution from 5.12s to 5.14s; if the residual harmonic ratio is greater than the preset residual ratio limit twice consecutively, the feedback allowable period corresponding to the same load mutation type can also be adjusted from 5.02s to 5.15s to 5.03s to 5.16s, or the compensation coefficient corresponding to this harmonic number can be increased by a preset amount within the upper limit of the allowable compensation current of the grid-connected converter.

[0084] In this embodiment, the regenerative load switching type corresponds to a preset feedback allowable state. When executing the feedback window sub-instruction, if the DC bus voltage state does not correspond to the preset feedback allowable state, the data acquisition controller generates a condition maintenance instruction and sends it to the test-side inverter and the grid-connected converter. The condition maintenance instruction includes the current load maintenance period, the grid-connected side feedback prohibition period, and a resampling flag. For example, when the real-time DC bus voltage is higher than 690V, the data acquisition controller sets the grid-connected side feedback prohibition period to 50ms, sets the current load maintenance period to 50ms, and generates a resampling flag. The test-side inverter maintains the current load state according to the condition maintenance instruction, and the grid-connected converter does not execute the AC grid feedback path during the grid-connected side feedback prohibition period.

[0085] After executing the operating condition hold command, the data acquisition controller re-acquires the voltage and current signals at the grid connection point according to the resampling marker, and generates replacement background harmonic data based on the re-acquired voltage and current signals. This replacement background harmonic data is used to replace the original steady-state background harmonic data in the calculation of load change-related harmonic data when the same type of load change occurs subsequently. The original steady-state background harmonic data is retained as a historical test record in the operating condition harmonic fingerprint table, while the replacement background harmonic data is used as the background harmonic data for subsequent similar load change types in the calculation. Therefore, when the grid state or DC bus voltage state changes during the load test, the basic background harmonic data in the operating condition harmonic fingerprint table can be updated with the actual test environment, avoiding the use of outdated steady-state background harmonic data when the same type of load change occurs subsequently.

[0086] In this embodiment, the test results include load mutation pre-registration records, operating condition harmonic fingerprint tables, dual-end collaborative control commands, residual fingerprint records, and DC bus energy flow records, grid connection point voltage and current records, and the speed and torque response records of the tested electric drive system generated based on synchronously acquired sampling data. The test results are stored in association according to operating condition timing markers, switching times, and load mutation types. The DC bus energy flow record can be generated based on the DC bus voltage state, the output current of the inverter on the test side, and the input current of the inverter on the grid connection side; the grid connection point voltage and current record can be generated based on the three-phase voltage and current signals at the grid connection point; and the tested electric drive system speed and torque response record can be generated based on the actual speed and torque of the tested electric drive system. Through this associated storage method, the corresponding sampling window, harmonic fingerprint, dual-end collaborative control commands, and execution results can be traced according to the specific load mutation type in subsequent test analysis.

[0087] To verify the technical effectiveness of this embodiment, comparative tests were conducted in the same electric vehicle drive system loading test laboratory. Except for the different control strategies, the control method and this method used the same test bench, the accompanying motor, the drive system under test, the rated DC bus voltage, the sampling frequency, the current operating condition segment, the next operating condition segment, and the switching time. In the comparative test, the target speed for the current operating condition segment was 3000 rpm, the target torque was 100 Nm, the target speed for the next operating condition segment was 3000 rpm, the target torque was -50 Nm, the switching time was 5.0 s, and the rated DC bus voltage was 650 V. The control method used a passive closed-loop energy feedback control method based solely on the real-time voltage and current signals at the grid connection point and the DC bus status; this method used load mutation pre-registration records, a harmonic fingerprint table for operating conditions, and dual-end collaborative control commands for control. The test data in Table 2 are the statistical results of 50 similar operating condition switching tests. The maximum DC bus voltage fluctuation amplitude, DC bus voltage recovery time, peak value of transient total harmonic distortion rate at the grid connection point, and maximum torque tracking deviation of the tested electric drive system are the maximum values ​​of the 50 tests. The number of test interruptions and the completeness of traceable records after operating condition switching are obtained from the statistics of the 50 test processes.

[0088] Table 2 Comparison of test data between this method and the control method

[0089] Maximum voltage fluctuation of DC bus 50V 14V DC bus voltage recovery time 300ms 55ms Peak transient total harmonic distortion rate at grid connection point 8.50% 2.80% Maximum deviation in torque tracking of the tested electric drive system 12.5Nm 4.2Nm Number of test interruptions in 50 similar operating condition switches 3 times 0 times Completeness of traceable records after operating condition switch 82% 100%

[0090] As shown in Table 2, under the same test conditions, this method, through load mutation pre-registration records, operating condition harmonic fingerprint tables, and dual-end collaborative control commands, enables coordinated processing of changes in load test conditions, load parameters of the test motor, DC bus voltage status, and changes in grid connection point electrical quantities within the same test sequence. Compared to passive closed-loop adjustment based solely on real-time grid connection point electrical quantities, this method reduces the response lag between energy feedback control and harmonic suppression control during operating condition alternation, reduces DC bus voltage fluctuations and transient harmonic peak values ​​at the grid connection point, and maintains the continuity of the load test process for the tested electric drive system and the traceability of the test results.

[0091] The specific values ​​in this embodiment are only used to illustrate one possible implementation. In other embodiments, the sampling frequency, the width of the pre-sampling window, the width of the response sampling window, the width of the residual sampling window, the compensation coefficient, the feedback allowable state, and the residual proportional limit can be set according to the equipment capacity of the electric vehicle electric drive system loading test laboratory, the rated voltage of the DC bus, the power level of the test motor, and the test condition type. As long as a load mutation pre-registration record can be generated according to the loading test condition instruction, and a condition harmonic fingerprint table can be constructed based on the sampling window, and then a dual-end collaborative control instruction containing grid-connected side compensation sub-instruction, loading side smoothing sub-instruction, and feedback window sub-instruction can be generated, this method can be implemented.

[0092] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for energy feedback and harmonic suppression in a loading test chamber for an electric vehicle electric drive system, characterized in that, The loading test chamber includes a frequency converter power supply network, which includes a test-side frequency converter, a DC bus, and a grid-connected converter connected to the AC power grid. The grid-connected converter is connected to the AC power grid through a grid connection point. The method includes the following steps: Obtain a load test condition instruction, which includes multiple condition segments arranged in chronological order. Determine two consecutive condition segments as adjacent condition segments, determine the time of condition alternation between adjacent condition segments as the switching time, and generate a load mutation pre-registration record based on the dynamic condition change information of adjacent condition segments and the switching time. A pre-sampling window is started before the switching time, and a response sampling window is started after the switching time to collect the operating status parameters of the frequency converter power supply network and the electrical signals of the grid connection point. Harmonic components are extracted from the electrical signals collected in the pre-sampling window and the response sampling window, and a working condition harmonic fingerprint table is constructed based on the extracted current harmonic components. The working condition harmonic fingerprint table associates the current harmonic components with the load mutation pre-registration record. The dual-end collaborative control instructions are generated based on the operating condition harmonic fingerprint table. The dual-end collaborative control instructions include at least a grid-connected side compensation sub-instruction for controlling the grid-connected converter and a loading side smoothing sub-instruction for controlling the test-side frequency converter. The dual-end coordinated control command is executed to provide a coordinated response between converter control and frequency converter load control during operating condition alternation.

2. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 1, characterized in that, The loading test chamber also includes a test bench, a test motor, a tested electric drive system, and a data acquisition controller. The test motor and the tested electric drive system are connected in a toggle connection via the test bench, and the test-side inverter is connected to the test motor. Each operating condition segment includes a target speed, a target torque, and an operating condition timing marker. The dynamic operating condition change information includes the target speed change direction and the target torque change direction of adjacent operating condition segments. The acquisition of the operating status parameters of the variable frequency power supply network and the electrical signals of the grid connection point includes: synchronously acquiring the operating parameters of the tested electric drive system, the loading parameters of the test motor, the voltage status of the DC bus, and the voltage and current signals of the grid connection point through the data acquisition controller.

3. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 2, characterized in that, The adjacent operating condition segments include the current operating condition segment and the next operating condition segment; the load mutation pre-registration record includes the load mutation type, the switching time, the operating condition timing mark of the current operating condition segment, and the operating condition timing mark of the next operating condition segment; generating the load mutation pre-registration record includes: reading the target speed, target torque, and end time of the current operating condition segment; reading the target speed, target torque, and start time of the next operating condition segment; determining the load mutation type based on the target speed change direction and target torque change direction between the current operating condition segment and the next operating condition segment; and writing the load mutation type, the switching time, the operating condition timing mark of the current operating condition segment, and the operating condition timing mark of the next operating condition segment into the load mutation pre-registration record.

4. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 3, characterized in that, The load change types include torque increase type, torque decrease type, target speed increase type, target speed decrease type, speed and torque change in the same direction type, speed and torque change in opposite direction type, and regenerative load switching type; the regenerative load switching type is determined by the speed direction of the accompanying motor, the electromagnetic torque direction of the accompanying motor, and the voltage change direction of the DC bus.

5. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 3 or 4, characterized in that, The start time of the pre-sampling window is earlier than the switching time, and the start time of the response sampling window is the switching time. The data acquisition controller records the sampling data in the pre-sampling window and the response sampling window under the same time reference, and writes the sampling data into the window data buffer corresponding to the load mutation pre-registration record.

6. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 4, characterized in that, The construction of the operating condition harmonic fingerprint table includes: performing spectrum analysis on the current signal of the grid connection point collected within the pre-sampling window, extracting each harmonic component, and generating steady-state background harmonic data with harmonic order markers; performing spectrum analysis on the current signal of the grid connection point collected within the response sampling window, extracting each harmonic component, and generating abrupt response harmonic data with harmonic order markers; subtracting the abrupt response harmonic data from the steady-state background harmonic data according to the same harmonic order to obtain load abrupt related harmonic data; and writing the load abrupt related harmonic data, the load abrupt type, and the switching time into the operating condition harmonic fingerprint table.

7. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 6, characterized in that, The load mutation-related harmonic data includes the harmonic number, harmonic occurrence time period, harmonic current direction marker extracted based on the current harmonic component of the grid connection point, voltage phase interval determined based on the voltage signal of the grid connection point, and the corresponding load mutation type. The period in which the harmonics occur is divided into the period before switching, the period immediately after switching, and the period after switching, according to the switching time.

8. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 7, characterized in that, The dual-end collaborative control command further includes: a feedback window sub-command determined based on the voltage state of the DC bus; the generation of the dual-end collaborative control command based on the operating condition harmonic fingerprint table includes: generating the grid-connected side compensation sub-command based on the harmonic number, the harmonic current direction marker, and the voltage phase interval; generating the load-side smoothing sub-command based on the load mutation type, the harmonic occurrence period, and the loading parameters of the accompanying motor; generating the feedback window sub-command based on the voltage state of the DC bus, the load mutation type, and the switching time; and binding the grid-connected side compensation sub-command, the load-side smoothing sub-command, and the feedback window sub-command to the load mutation pre-registration record.

9. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle drive system according to claim 8, characterized in that, The grid-connected side compensation sub-instruction includes a compensation current instruction, a compensation execution start time, and a compensation execution termination time; the loading side smoothing sub-instruction includes a loading slope switching instruction, a loading hold period, and a loading recovery time; the feedback window sub-instruction includes a feedback allow period, a feedback limit period, and a feedback path marker.

10. The energy feedback and harmonic suppression method for a loading test chamber of an electric vehicle electric drive system according to claim 9, characterized in that, The execution of the dual-end collaborative control command includes: the data acquisition controller keeping the loading test condition command unchanged, controlling the test-side inverter to perform a transition loading process according to the loading-side smoothing sub-command, controlling the grid-connected inverter to perform a compensation current output process according to the compensation current command in the grid-connected side compensation sub-command, and controlling the grid-connected inverter to perform a feedback time period constraint process according to the feedback window sub-command, so as to generate the test results of the electric drive system under test.

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