A harmonic suppression system applied to power electronics

Abstract

The application discloses a harmonic suppression system applied to power electronics, and relates to the technical field of power electronic control, and comprises the following steps: a data acquisition module acquires voltage, current and operating state parameters of a power electronic device; a harmonic analysis module obtains harmonic components and energy of the harmonic components based on a continuous time window, and forms a harmonic state sequence; a migration determination module determines a current dominant harmonic component, a candidate harmonic component and a migration target harmonic component according to the change of harmonic energy before and after the change of the operating state, and determines a harmonic migration degree; an inhibition distribution module adjusts inhibition weights of different harmonic components according to the harmonic migration degree, and generates harmonic suppression parameters; and a feedback correction module re-corrects the migration target and the inhibition weights according to the reduction of the harmonic energy after inhibition. The application can reduce the adjustment lag of the harmonic suppression object in the process of the change of the operating state, and improve the continuity and adaptability of the harmonic suppression.

Description

Technical Field

[0001] This invention relates to the field of power electronic control technology, and more specifically to a harmonic suppression system applied to power electronics. Background Technology

[0002] With the widespread application of power electronic devices such as inverters, rectifiers, and converters in power systems and industrial power consumption scenarios, factors such as the periodic switching of power switching devices, pulse width modulation, and load changes can cause harmonics of different orders to be generated. High harmonic content can increase device losses and heat generation, and may affect power quality and the stable operation of related electrical equipment. Therefore, it is usually necessary to detect and suppress harmonics during the operation of power electronic devices.

[0003] Existing harmonic suppression techniques typically decompose the acquired voltage or current into harmonics, set corresponding compensation parameters based on the amplitude of each harmonic detected, and reduce the target harmonics through active filtering, resonant control, or compensating current injection. When a harmonic exceeds the set range, the compensation amount corresponding to that harmonic is increased. Some schemes also adaptively adjust the compensation parameters according to load changes.

[0004] However, when the load rate, DC bus voltage, modulation ratio, switching frequency, or operating mode of a power electronic device changes, the energy distribution of each harmonic does not always remain fixed. The original dominant harmonic may gradually decrease, while other harmonics simultaneously increase and become new dominant harmonics. Existing solutions typically focus on the current harmonic amplitude or over-limit results, making it difficult to promptly identify this changing relationship between different harmonic components before and after changes in operating conditions. Often, it is necessary to wait for a significant increase in the new target harmonic before adjusting the suppression parameters, resulting in a lag in the adjustment of the suppression target. At the same time, directly switching the compensation parameters of different harmonics may also lead to an unreasonable distribution of suppression capabilities.

[0005] Therefore, there is still room for improvement in how to adjust the suppression capability of different harmonic components in a timely manner according to the changes in harmonic energy during the operation process. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a harmonic suppression system for power electronics.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A harmonic suppression system for power electronics includes: The data acquisition module is used to acquire voltage, current, and operating status parameters of power electronic devices; The harmonic analysis module is used to perform harmonic decomposition on voltage and current according to a continuous time window, obtain each harmonic component and its energy, and form a harmonic state sequence. The migration determination module is used to determine the current dominant harmonic component based on the harmonic state sequence, and to determine the change time when the operating state parameters change. A first window group and a second window group are formed with the change time as the boundary. The reduction degree of the current dominant harmonic component and the increase degree of the other harmonic components are determined based on the energy changes of the two window groups. The components whose increase degree reaches the first threshold are selected as candidate harmonic components. From the candidate harmonic components whose proportion of the total harmonic energy reaches the second threshold, they are sorted from high to low according to the energy increase rate. The harmonic component with the first position in the sort is determined as the target harmonic component for migration. The degree of harmonic migration is determined based on the reduction degree and the increase degree of the target harmonic component for migration. The suppression allocation module is used to reduce the suppression weight of the current dominant harmonic component and increase the suppression weight of the target harmonic component based on the degree of harmonic migration. It determines the compensation command amplitude and generates harmonic suppression parameters based on the adjusted suppression weight and harmonic amplitude. The feedback correction module is used to determine the energy reduction rate of the target harmonic component to be migrated based on the suppressed harmonic state sequence. When the energy reduction rate does not reach the third threshold, the target harmonic component to be migrated is re-determined and fed back to the suppression allocation module to update the suppression weight and harmonic suppression parameters.

[0008] Preferably, in the harmonic analysis module, the method for forming a harmonic state sequence includes: Harmonic decomposition is performed on the voltage and current within each time window to obtain the voltage harmonic components and current harmonic components corresponding to the preset harmonic order. The sampled values ​​of each current harmonic component within the time window are squared and summed to obtain the corresponding harmonic energy. The sum of the harmonic energies is then determined as the total harmonic energy. The harmonic energies are arranged in chronological order according to their harmonic order and time window to form a harmonic state sequence.

[0009] Preferably, the method for determining the first window group and the second window group in the migration determination module includes: Compare the running status parameters corresponding to adjacent time windows; For numerical operating status parameters, a change in the operating status parameter is determined when its change reaches the corresponding state change threshold; for state-type operating status parameters, a change in the operating status parameter is determined when its state value changes, and the corresponding change time is recorded. Two or more consecutive time windows are selected before the change time to form a first window group, and the same number of consecutive time windows are selected after the change time to form a second window group. The average harmonic energy of each harmonic component in the two window groups is determined respectively.

[0010] Preferably, the method for determining the current dominant harmonic component and candidate harmonic components in the migration determination module includes: The corresponding harmonic energy ratio is determined based on the average harmonic energy of each harmonic component in the first window group. The harmonic energy ratios are sorted from high to low, and the harmonic component at the top of the sort is determined as the current dominant harmonic component. For each harmonic component other than the currently dominant harmonic component, the degree of increase of the corresponding harmonic component is determined according to the ratio of the difference between the average harmonic energy of the second window group and the average harmonic energy of the first window group to the average harmonic energy of the first window group. The degree of increase is the harmonic energy increase rate. The harmonic component whose degree of increase reaches the first threshold is determined as a candidate harmonic component.

[0011] Preferably, the method for determining the degree of harmonic migration in the migration determination module includes: The degree of reduction of the current dominant harmonic component is determined based on the proportion of the average harmonic energy difference between the current dominant harmonic component and the second window group to the average harmonic energy of the first window group. The degree of reduction is the dominant harmonic energy reduction rate. Determine the proportion of harmonic energy of the target harmonic component in the second window group; After normalizing the reduction degree of the current dominant harmonic component, the increase degree of the target harmonic component, and the proportion of harmonic energy, the results are multiplied by the first weight, the second weight, and the third weight and summed to obtain the degree of harmonic migration. The first weight, the second weight, and the third weight are all greater than 0 and their sum is 1.

[0012] Preferably, in the suppression allocation module, the method for adjusting the suppression weights includes: The upper limit of the transferable suppression weight is determined based on the difference between the current suppression weight of the current dominant harmonic component and the preset retention weight, where the preset retention weight is less than the current suppression weight. The product of the harmonic migration degree and the upper limit of the transferable suppression weight is determined as the weight adjustment amount; The weight adjustment amount is deducted from the suppression weight of the current dominant harmonic component, and the weight adjustment amount is added to the suppression weight of the target harmonic component to keep the total suppression weight of each harmonic component unchanged.

[0013] Preferably, in the suppression allocation module, the method for determining the compensation command amplitude includes: The amplitude of each harmonic component is used as the corresponding basic compensation command amplitude. The product of the basic compensation command amplitude and the adjusted corresponding suppression weight is determined as the compensation command amplitude, and the reverse compensation phase is determined according to the phase of the corresponding harmonic component. Harmonic suppression parameters are generated based on the compensation command amplitude and the reverse compensation phase.

[0014] Preferably, in the feedback correction module, the method for determining the harmonic energy reduction rate includes: Determine the first average harmonic energy of the target harmonic component before applying the harmonic suppression parameters within two or more consecutive time windows, and determine the second average harmonic energy of the target harmonic component after applying the harmonic suppression parameters within the same number of consecutive time windows. The energy reduction rate is determined based on the ratio of the difference between the first average harmonic energy and the second average harmonic energy to the first average harmonic energy.

[0015] Preferably, the method for redetermining the harmonic components of the migration target in the feedback correction module includes: When the energy reduction rate does not reach the third threshold, the harmonic components that increase in harmonic energy sequentially within two or more consecutive time windows, reach the first threshold in the rate of increase in harmonic energy, and reach the second threshold in the proportion of harmonic energy to total harmonic energy are selected from the suppressed harmonic state sequence. The harmonic components are sorted from highest to lowest according to their harmonic energy increase rate. The harmonic component with the highest order is determined as the corrected target harmonic component and fed back to the suppression allocation module.

[0016] Preferably, the operating status parameters include at least one of DC bus voltage, load rate, modulation ratio, switching frequency, and operating mode.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention identifies harmonic migration trends by comparing harmonic state sequences before and after changes in operating state, combining the reduction degree of the current dominant harmonic component with the increase degree of other harmonic components. Compared to compensation based solely on the current harmonic amplitude or harmonic exceedance results, this invention can promptly determine the target harmonic component to migrate during changes in the operating state of power electronic devices, reducing the lag in harmonic suppression adjustments. The degree of harmonic migration is determined based on the reduction degree of the current dominant harmonic component, the increase degree of the target harmonic component, and the proportion of harmonic energy. Based on this degree of migration, a portion of the suppression weight is transferred from the current dominant harmonic component to the target harmonic component. This gradually improves the suppression capability of the target harmonic while preserving the original dominant harmonic suppression capability, reducing abrupt changes in compensation caused by direct switching between different harmonic suppression channels, and improving the efficiency of operating state transitions. The continuity of harmonic suppression during phase transition is ensured. Candidate harmonic components are screened by both the degree of increase in harmonic energy and the proportion of harmonic energy, and the target harmonic component for migration is determined from the candidate harmonic components that meet the conditions. This reduces the probability that low-energy harmonics are mistakenly identified as the main suppression targets due to their high short-term growth ratio, and makes the limited harmonic suppression capability more focused on the harmonic components that need to be prioritized at present. The migration target and suppression results are verified by feedback based on the harmonic energy reduction rate after the harmonic suppression parameters are applied. When the suppression effect does not meet the preset requirements, the target harmonic component for migration is re-determined and the suppression weight and harmonic suppression parameters are updated. This forms a closed loop of harmonic detection, migration judgment, suppression capability allocation and feedback correction, thereby improving the system's adaptability to changes in load rate, DC bus voltage, modulation ratio, switching frequency and operating mode. Attached Figure Description

[0018] Figure 1 This is a system framework diagram of the present invention. Detailed Implementation

[0019] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0020] Reference Figure 1 As shown, a harmonic suppression system for power electronics includes: The data acquisition module is used to acquire voltage, current, and operating status parameters of power electronic devices; Among them, power electronic devices can be inverters, rectifiers, converters, or other devices that use power switching devices to convert electrical energy.

[0021] The voltage and current acquired by the data acquisition module can include the three-phase voltage and three-phase current on the AC side of the power electronic device, or it can acquire voltage and current signals that can characterize the operating status of the device, depending on the specific device structure.

[0022] Operating status parameters are used to reflect the current power conversion status of the power electronic device, including at least one of the following: DC bus voltage, load rate, modulation ratio, switching frequency, and operating mode. The load rate can be obtained based on the ratio of the current output power to the rated output power; the modulation ratio can be directly read from the device's pulse width modulation control unit; and the operating mode can be determined using a mode identifier within the device controller, such as constant voltage operation mode, constant power operation mode, rectification operation mode, or inverter operation mode.

[0023] In one embodiment, the power electronic device is connected to a 50Hz AC system, and the voltage and current sampling frequency is set to 20kHz. A time window is defined as 10 consecutive fundamental frequency cycles, meaning the duration of a single time window is 0.2s. The controller sequentially forms time windows W1, W2, W3, etc., according to the sampling order. The above sampling frequency and window length are only for illustrating one possible implementation; in actual applications, they can be adjusted according to the power switching frequency, the AC fundamental frequency, and the controller's processing power.

[0024] The harmonic analysis module is used to perform harmonic decomposition on voltage and current according to a continuous time window, obtain each harmonic component and its energy, and form a harmonic state sequence. Specifically, harmonic decomposition is performed on the voltage and current data collected within each time window. In one implementation, a fast Fourier transform is used to perform a frequency domain transformation on the voltage and current data within the window. The corresponding voltage and current harmonic components are extracted according to the integer multiples of the fundamental frequency, and the amplitude and phase of each harmonic component are obtained.

[0025] In this embodiment, the current harmonic component is used as the object of subsequent harmonic migration determination and compensation control. Therefore, unless otherwise specified, the terms harmonic component, harmonic energy, and harmonic state sequence referred to below all refer to the data corresponding to the current harmonic component. The voltage harmonic component is used to assist in characterizing the AC side voltage harmonic state. In other embodiments employing voltage compensation control, the corresponding harmonic state sequence can also be formed based on the voltage harmonic component according to the same processing procedure.

[0026] The preset harmonic order can be set according to the harmonic distribution of the power electronic device to be suppressed. For example, in one embodiment, the 3rd, 5th, 7th, 11th, and 13th harmonics are analyzed. The preset harmonic order is not required to be fixed to the above-mentioned orders. When other harmonic orders have a high content in the target power electronic device, the corresponding harmonic order can also be added to the preset harmonic order set for migration determination.

[0027] For the k-th harmonic component within the j-th time window, the squared values ​​of the sampled values ​​of this harmonic component within the current time window are summed to obtain the corresponding harmonic energy:

[0028] In the formula, Let be the harmonic energy of the k-th harmonic component within the j-th time window; is the nth sample value of the kth harmonic component within the j-th time window; N is the number of sample points involved in the calculation within a time window.

[0029] The total harmonic energy of the current time window is obtained by summing the harmonic energies of each harmonic component in the preset harmonic order set. The total harmonic energy referred to in this paper is the sum of the harmonic energies of each harmonic component in the preset harmonic order set currently involved in migration determination, excluding the fundamental frequency energy. The proportion of harmonic energy corresponding to any harmonic component is obtained by dividing the harmonic energy of that harmonic component by the total harmonic energy.

[0030] The harmonic analysis module stores the harmonic energy corresponding to each harmonic component in the order of harmonic order and time window. For example, the harmonic energy of the 5th harmonic in a continuous time window is recorded as E5,1, E5,2, E5,3..., and the harmonic energy of the 7th harmonic in a continuous time window is recorded as E7,1, E7,2, E7,3..., forming a harmonic state sequence from the harmonic energy of each harmonic component changing with the continuous time window.

[0031] The harmonic state sequence can be used to obtain the increase, decrease, and stability of the same harmonic during continuous operation of the device, and provide a data basis for subsequent judgment of the dominant relationship between different harmonic components.

[0032] The migration determination module is used to determine the current dominant harmonic component based on the harmonic state sequence, and to determine the change time when the operating state parameters change. A first window group and a second window group are formed with the change time as the boundary. The reduction degree of the current dominant harmonic component and the increase degree of the other harmonic components are determined based on the energy changes of the two window groups. The components whose increase degree reaches the first threshold are selected as candidate harmonic components. From the candidate harmonic components whose proportion of the total harmonic energy reaches the second threshold, they are sorted from high to low according to the energy increase rate. The harmonic component with the first position in the sort is determined as the target harmonic component for migration. The degree of harmonic migration is determined based on the reduction degree and the increase degree of the target harmonic component for migration. Specifically, the migration determination module continuously compares the running status parameters corresponding to adjacent time windows.

[0033] For numerical operating status parameters such as DC bus voltage, load factor, modulation ratio, and switching frequency, corresponding state change thresholds are set according to the normal fluctuation range of each parameter during the stable operation phase of the device. When the change of any numerical operating status parameter between adjacent time windows reaches the corresponding state change threshold, the operating status parameter is determined to have changed.

[0034] For example, in one implementation, a 10 percentage point change in load rate is used as a criterion for determining a change in load status; and a change in DC bus voltage in an adjacent time window reaching 3% of the DC bus voltage in the previous time window is used as a criterion for determining a change in bus status.

[0035] For state-based operating parameters such as operating modes, a change in operating status is determined when the state value corresponding to adjacent time windows changes. For example, when the operating mode recorded by the device controller changes from constant power operating mode to constant voltage operating mode, or from rectification operating mode to inverter operating mode, it is determined that a state-based operating parameter has changed.

[0036] The migration determination module records the moment when the corresponding state change condition is first met and determines that moment as the change moment.

[0037] Using the moment of change as a boundary, select two or more consecutive time windows before the moment of change to form a first window group, and select the same number of consecutive time windows after the moment of change to form a second window group.

[0038] In a preferred embodiment, the first window group and the second window group each contain three consecutive time windows. The average harmonic energy of the same harmonic in each of the three time windows is calculated to obtain the first average harmonic energy of the harmonic in the first window group and the second average harmonic energy in the second window group.

[0039] Averaging over multiple consecutive time windows can reduce the impact of energy fluctuations caused by load transients, sampling noise, or short-term switching disturbances within a single time window on the migration determination results. The specific number of time windows included in a window group can be set based on the device's response speed. Fewer windows can be used when high response speed is required, while the number of windows can be appropriately increased when high resistance to transient disturbances is required.

[0040] After determining the first window group, the corresponding harmonic energy ratio is calculated based on the average harmonic energy of each harmonic component in the first window group, and the harmonic energy ratios are sorted from high to low. The harmonic component with the highest ranking is determined as the current dominant harmonic component.

[0041] The dominant harmonic component refers to the harmonic component that contributes significantly to the current total harmonic energy and is preferentially allocated harmonic suppression capability by the system before the change in operating state.

[0042] For harmonic components other than the currently dominant harmonic component, compare the average harmonic energy in the first window group and the second window group respectively.

[0043] When the average harmonic energy of the second window group of a certain harmonic component is higher than the average harmonic energy of the first window group, the degree of increase of the harmonic component is determined according to the ratio of the difference between the two to the average harmonic energy of the first window group. The degree of increase is the harmonic energy increase rate.

[0044] For example, if the average harmonic energy of the kth harmonic in the first window group is 10 and the average harmonic energy in the second window group is 13, then the corresponding harmonic energy increase rate is 30%.

[0045] Considering that the average harmonic energy of a certain harmonic in the first window group may be close to zero, to avoid abnormally amplifying the harmonic energy increase rate due to using an excessively small value as the denominator, a preset energy lower limit is set in one embodiment. When the average harmonic energy in the first window group is lower than the preset energy lower limit, the preset energy lower limit is used as the reference energy for calculating the harmonic energy increase rate. The preset energy lower limit can be determined based on voltage and current sampling noise and harmonic analysis error. For example, 1.2 times the upper limit of the harmonic analysis noise energy corresponding to the stable operation phase can be used as the preset energy lower limit.

[0046] The first threshold is used to exclude minor variations caused by normal fluctuations under stable operating conditions from other harmonic components. The first threshold can be determined based on historical data of the target power electronic device during stable operation. Specifically, it can be achieved by collecting the increase rate of each harmonic energy corresponding to multiple consecutive windows during stable operation, and setting a first threshold higher than the normal fluctuation range.

[0047] For example, in one implementation, the rate of increase in harmonic energy of each target harmonic during the stable operation phase between adjacent window groups is typically less than 10%, so the first threshold is set to 15%. When the increase of other harmonic components reaches 15%, the corresponding harmonic component is identified as a candidate harmonic component.

[0048] In other implementations, the first threshold can be set separately for different power levels and different operating modes. For example, different normal fluctuation ranges can be stored for high-load and low-load operating states, and the corresponding first threshold can be called according to the current operating state.

[0049] When judging solely based on the rate of increase of harmonic energy, it is possible that a harmonic component with a smaller base number may have a higher rate of increase, but its actual harmonic energy may be lower. Therefore, this embodiment further filters based on the proportion of the average harmonic energy of the candidate harmonic component in the second window group to the total harmonic energy of each order in the second window group.

[0050] The second threshold is used to limit the actual contribution of candidate harmonic components to the current total harmonic energy. In one embodiment, the second threshold is set to 15%. When the harmonic energy of a candidate harmonic component accounts for 15% of the total harmonic energy, the candidate harmonic component is retained to participate in the migration target ranking; if the second threshold is not reached, even if its increase reaches the first threshold, it will not be considered as a candidate for this migration target.

[0051] When there are multiple candidate harmonic components that meet the first and second thresholds, they are sorted from high to low according to the harmonic energy increase rate of each candidate harmonic component, and the candidate harmonic component ranked first is determined as the target harmonic component for migration.

[0052] Therefore, one or more candidate harmonic components may be generated during a single migration determination process, but only one migration target harmonic component is ultimately determined to avoid multiple migration targets participating in the suppression of weight transfer, which would result in an unclear weight adjustment target.

[0053] After determining the target harmonic component for migration, the reduction degree of the current dominant harmonic component is further calculated.

[0054] Specifically, the degree of reduction of the current dominant harmonic component is determined based on the difference between the first average harmonic energy of the current dominant harmonic component in the first window group and the second average harmonic energy in the second window group, which is the proportion of the first average harmonic energy. The degree of reduction is the dominant harmonic energy reduction rate.

[0055] For example, if the average harmonic energy of the current dominant harmonic component is 40 in the first window group and 30 in the second window group, then the reduction of the current dominant harmonic component is 25%.

[0056] Simultaneously, the degree of increase of the target harmonic component and the proportion of harmonic energy of the target harmonic component in the second window group are obtained.

[0057] To enable different parameters to participate in the same migration degree calculation, the reduction degree of the current dominant harmonic component, the increase degree of the migration target harmonic component, and the proportion of harmonic energy are normalized respectively.

[0058] In one implementation, for non-negative harmonic energy increase and decrease rates, r / (1+r) is used to convert them to the 0 to 1 range; when the harmonic energy percentage is already in the 0 to 1 range, it is directly used as the corresponding normalized value.

[0059] The three normalization results are assigned to the first, second, and third weights, respectively, and the harmonic migration degree M is determined according to the following formula:

[0060] In the formula, The degree of reduction in the current dominant harmonic component after normalization; The degree of increase in harmonic components of the normalized migration target; The proportion of harmonic energy of the target harmonic component in the second window group; It is the first weight; As the second weight; The third weight is the first weight; the first weight, the second weight, and the third weight are all greater than 0 and their sum is 1.

[0061] In one implementation, the first weight is set to 0.4, the second weight to 0.35, and the third weight to 0.25. This set of weights is used to simultaneously consider the attenuation degree of the original dominant harmonic, the growth degree of the new target harmonic, and the current actual energy proportion of the new target harmonic.

[0062] The first to third weights are not limited to the values ​​mentioned above and can be calibrated based on historical operating data of the equipment. For example, the three parameters can be calculated for multiple known operating state switching events, and the correspondence between the three parameters and the actual dominant harmonic changes can be compared. The weights can be adjusted while ensuring that the sum of the three weights is 1.

[0063] The suppression allocation module is used to reduce the suppression weight of the current dominant harmonic component and increase the suppression weight of the target harmonic component based on the degree of harmonic migration. It determines the compensation command amplitude and generates harmonic suppression parameters based on the adjusted suppression weight and harmonic amplitude. During the stable operation phase of the system, each target harmonic component is pre-assigned a corresponding suppression weight, and the sum of the suppression weights of each harmonic component remains unchanged. The initial suppression weights can be set according to the energy proportion of each harmonic component during the stable operation phase, or according to the initial control parameters obtained during equipment commissioning.

[0064] When harmonic migration occurs, instead of directly canceling the suppression of the current dominant harmonic component, a preset retention weight is set for the current dominant harmonic component.

[0065] The upper limit of the transferable suppression weight is determined based on the difference between the current suppression weight and the preset retention weight of the current dominant harmonic component. Since the preset retention weight is less than the current suppression weight, the upper limit of the transferable suppression weight is a non-negative value.

[0066] For example, if the current dominant harmonic component has a suppression weight of 0.60 and a preset retention weight of 0.20, then the upper limit of the transferable suppression weight is 0.40.

[0067] Since the aforementioned harmonic migration degree M is within the range of 0 to 1, multiplying the harmonic migration degree by the upper limit of the transferable suppression weight yields the weight adjustment amount for this operation:

[0068] In the formula, This is the weight adjustment amount; The current suppression weight for the currently dominant harmonic component; Preset weights.

[0069] The weight adjustment amount is deducted from the suppression weight of the current dominant harmonic component, and the same weight adjustment amount is added to the suppression weight of the target harmonic component, thereby keeping the sum of the suppression weights of all harmonic components unchanged.

[0070] By setting preset retention weights, the suppression capability corresponding to the original dominant harmonic can be completely canceled before the harmonic migration is completed. By determining the weight adjustment amount based on the degree of harmonic migration, the suppression capability can be gradually transferred from the current dominant harmonic component to the target harmonic component as the harmonic migration trend progresses.

[0071] After the suppression weight adjustment is completed, the amplitude of each harmonic component is used as the corresponding basic compensation command amplitude, and the basic compensation command amplitude is multiplied by the adjusted corresponding suppression weight to obtain the actual compensation command amplitude.

[0072] For example, if the amplitude of a target harmonic component is 5A and the adjusted suppression weight is 0.35, then the compensation command amplitude corresponding to the target harmonic component is 1.75A.

[0073] The corresponding reverse compensation phase is determined based on the detection phase of the target harmonic component, so that the generated compensation harmonic is opposite in phase to the original target harmonic.

[0074] The compensation command amplitude and reverse compensation phase corresponding to each target harmonic together form the harmonic suppression parameters. In one embodiment, the compensation current command corresponding to each target harmonic is superimposed on the original current reference command of the power electronic device, and then the corresponding power switching device drive signal is formed by the original current controller and pulse width modulation control unit of the device.

[0075] For power electronic devices that employ voltage control or other control structures, the aforementioned compensation commands can also be converted into corresponding voltage compensation amounts or other control parameters that can act on the power conversion process, based on the current device control architecture.

[0076] The feedback correction module is used to determine the energy reduction rate of the target harmonic component to be migrated based on the suppressed harmonic state sequence. When the energy reduction rate does not reach the third threshold, the target harmonic component to be migrated is re-determined and fed back to the suppression allocation module to update the suppression weight and harmonic suppression parameters.

[0077] Specifically, after implementing the new harmonic suppression parameters, the data acquisition module continues to acquire voltage and current, and the harmonic analysis module forms a suppressed updated harmonic state sequence according to the same time window and harmonic analysis method as described above.

[0078] Before obtaining the harmonic suppression parameters, the feedback correction module migrates the first average harmonic energy of the target harmonic component in two or more consecutive time windows, and obtains the second average harmonic energy in the same number of consecutive time windows after obtaining the harmonic suppression parameters.

[0079] The energy reduction rate is determined based on the ratio of the difference between the first average harmonic energy and the second average harmonic energy to the first average harmonic energy.

[0080] The third threshold is used to determine whether the current migration target and the corresponding suppression weight adjustment have achieved the expected suppression result. The third threshold can be determined based on the equipment's allowable harmonic fluctuation range, historical suppression effects, or control targets.

[0081] In one implementation, the third threshold is set to 20%. When the energy reduction rate of the target harmonic component reaches 20%, it is considered that the suppression parameter corresponding to the current target can produce the expected suppression effect, the current target is continued to be used, and each harmonic state is continuously updated according to the subsequent harmonic state sequence.

[0082] When the energy reduction rate of the harmonic component of the migration target does not reach the third threshold, the migration target redetering process begins.

[0083] Specifically, based on the updated harmonic state sequence after suppression, the migration targets are re-screened, and harmonic components that have successively increased harmonic energy in two or more consecutive time windows, whose harmonic energy increase rate reaches the first threshold, and whose harmonic energy accounts for the proportion of total harmonic energy reaches the second threshold.

[0084] The harmonic components are sorted from highest to lowest according to their harmonic energy increase rate. The harmonic component with the highest order is determined as the corrected target harmonic component and fed back to the suppression allocation module.

[0085] During re-screening, the original target harmonic component is not forcibly excluded. If the original target harmonic component still meets the first and second thresholds in the updated harmonic state sequence and its harmonic energy increase rate is still ranked first, the original target harmonic component will continue to be used as the corrected target, and the corresponding harmonic migration degree and suppression weight will be recalculated. If the harmonic energy increase rate of other harmonic components is ranked first, the other harmonic component will be determined as the corrected target harmonic component.

[0086] The suppression allocation module redetermines the corresponding harmonic migration degree and weight adjustment amount based on the corrected target harmonic components, updates the suppression weight of each harmonic component, and regenerates the harmonic suppression parameters accordingly, thus forming a closed loop between harmonic detection, migration determination, suppression allocation, and feedback correction.

[0087] The first, second, and third thresholds mentioned above correspond to different judgment purposes. Specifically, the first threshold is used to determine whether a non-dominant harmonic has generated an energy increase exceeding the normal fluctuation range; the second threshold is used to determine whether the current actual energy of a candidate harmonic has reached a level requiring the reallocation of suppression resources; and the third threshold is used to determine whether the migrating target harmonic achieves the expected suppression effect after implementing new harmonic suppression parameters. These three thresholds are applied to migration screening, energy contribution screening, and suppression effect feedback, respectively, and are not mutually exclusive.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A harmonic suppression system for power electronics, characterized in that, include: The data acquisition module is used to acquire voltage, current, and operating status parameters of power electronic devices; The harmonic analysis module is used to perform harmonic decomposition on voltage and current according to a continuous time window, obtain each harmonic component and its energy, and form a harmonic state sequence. The migration determination module is used to determine the current dominant harmonic component based on the harmonic state sequence, and to determine the change time when the operating state parameters change. A first window group and a second window group are formed with the change time as the boundary. The reduction degree of the current dominant harmonic component and the increase degree of the other harmonic components are determined based on the energy changes of the two window groups. The components whose increase degree reaches the first threshold are selected as candidate harmonic components. From the candidate harmonic components whose proportion of the total harmonic energy reaches the second threshold, they are sorted from high to low according to the energy increase rate. The harmonic component with the first position in the sort is determined as the target harmonic component for migration. The degree of harmonic migration is determined based on the reduction degree and the increase degree of the target harmonic component for migration. The suppression allocation module is used to reduce the suppression weight of the current dominant harmonic component and increase the suppression weight of the target harmonic component based on the degree of harmonic migration. It determines the compensation command amplitude and generates harmonic suppression parameters based on the adjusted suppression weight and harmonic amplitude. The feedback correction module is used to determine the energy reduction rate of the target harmonic component to be migrated based on the suppressed harmonic state sequence. When the energy reduction rate does not reach the third threshold, the target harmonic component to be migrated is re-determined and fed back to the suppression allocation module to update the suppression weight and harmonic suppression parameters.

2. The harmonic suppression system for power electronics according to claim 1, characterized in that, The method for forming the harmonic state sequence in the harmonic analysis module includes: Harmonic decomposition is performed on the voltage and current within each time window to obtain the voltage harmonic components and current harmonic components corresponding to the preset harmonic order. The sampled values ​​of each current harmonic component within the time window are squared and summed to obtain the corresponding harmonic energy. The sum of the harmonic energies is then determined as the total harmonic energy. The harmonic energies are arranged in chronological order according to their harmonic order and time window, forming a harmonic state sequence.

3. The harmonic suppression system for power electronics according to claim 1, characterized in that, The method for determining the first window group and the second window group in the migration determination module includes: Compare the running status parameters corresponding to adjacent time windows; For numerical operating status parameters, a change in the operating status parameter is determined when its change reaches the corresponding state change threshold; for state-type operating status parameters, a change in the operating status parameter is determined when its state value changes, and the corresponding change time is recorded. Two or more consecutive time windows are selected before the change time to form a first window group, and the same number of consecutive time windows are selected after the change time to form a second window group. The average harmonic energy of each harmonic component in the two window groups is determined respectively.

4. A harmonic suppression system for power electronics according to claim 1, characterized in that, The migration determination module includes the following methods for determining the current dominant harmonic component and candidate harmonic components: The corresponding harmonic energy ratio is determined based on the average harmonic energy of each harmonic component in the first window group. The harmonic energy ratios are sorted from high to low, and the harmonic component at the top of the sort is determined as the current dominant harmonic component. For each harmonic component other than the currently dominant harmonic component, the degree of increase of the corresponding harmonic component is determined according to the ratio of the difference between the average harmonic energy of the second window group and the average harmonic energy of the first window group to the average harmonic energy of the first window group. The degree of increase is the harmonic energy increase rate. The harmonic component whose degree of increase reaches the first threshold is determined as a candidate harmonic component.

5. A harmonic suppression system for power electronics according to claim 4, characterized in that, The method for determining the degree of harmonic migration in the migration determination module includes: The degree of reduction of the current dominant harmonic component is determined based on the proportion of the average harmonic energy difference between the current dominant harmonic component and the second window group to the average harmonic energy of the first window group. The degree of reduction is the dominant harmonic energy reduction rate. Determine the proportion of harmonic energy of the target harmonic component in the second window group; After normalizing the reduction degree of the current dominant harmonic component, the increase degree of the target harmonic component, and the proportion of harmonic energy, the results are multiplied by the first weight, the second weight, and the third weight and summed to obtain the degree of harmonic migration. The first weight, the second weight, and the third weight are all greater than 0 and their sum is 1.

6. A harmonic suppression system for power electronics according to claim 5, characterized in that, The method for adjusting the suppression weights in the suppression allocation module includes: The upper limit of the transferable suppression weight is determined based on the difference between the current suppression weight of the current dominant harmonic component and the preset retention weight, where the preset retention weight is less than the current suppression weight. The product of the harmonic migration degree and the upper limit of the transferable suppression weight is determined as the weight adjustment amount; The weight adjustment amount is deducted from the suppression weight of the current dominant harmonic component, and the weight adjustment amount is added to the suppression weight of the target harmonic component to keep the total suppression weight of each harmonic component unchanged.

7. A harmonic suppression system for power electronics according to claim 6, characterized in that, The method for determining the amplitude of the compensation command in the suppression allocation module includes: The amplitude of each harmonic component is used as the corresponding basic compensation command amplitude. The product of the basic compensation command amplitude and the adjusted corresponding suppression weight is determined as the compensation command amplitude, and the reverse compensation phase is determined according to the phase of the corresponding harmonic component. Harmonic suppression parameters are generated based on the compensation command amplitude and the reverse compensation phase.

8. A harmonic suppression system for power electronics according to claim 1, characterized in that, The method for determining the harmonic energy reduction rate in the feedback correction module includes: Determine the first average harmonic energy of the target harmonic component before applying the harmonic suppression parameters within two or more consecutive time windows, and determine the second average harmonic energy of the target harmonic component after applying the harmonic suppression parameters within the same number of consecutive time windows. The energy reduction rate is determined based on the ratio of the difference between the first average harmonic energy and the second average harmonic energy to the first average harmonic energy.

9. A harmonic suppression system for power electronics according to claim 8, characterized in that, The method for redetermining the harmonic components of the migration target in the feedback correction module includes: When the energy reduction rate does not reach the third threshold, the harmonic components that increase in harmonic energy sequentially within two or more consecutive time windows, reach the first threshold in the rate of increase in harmonic energy, and reach the second threshold in the proportion of harmonic energy to total harmonic energy are selected from the suppressed harmonic state sequence. The harmonic components are sorted from highest to lowest according to their harmonic energy increase rate. The harmonic component with the highest order is determined as the corrected target harmonic component and fed back to the suppression allocation module.

10. A harmonic suppression system for power electronics according to claim 1, characterized in that, The operating status parameters include at least one of the following: DC bus voltage, load rate, modulation ratio, switching frequency, and operating mode.

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