Dead-zone compensation method for common-mode voltage suppression PWM (Pulse Width Modulation) of two-level four-leg converter

Abstract

The invention relates to a dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-bridge-arm converter. The dead-zone compensation method comprises the steps that the current duty ratio, the current output current value and circuit parameters of each phase of bridge arm of the two-level four-bridge-arm converter are acquired; according to the current duty ratio, the current output current value and the current circuit parameter of each phase of bridge arm, predicting an instantaneous current value of each phase of bridge arm switch action moment in the next period; and screening out a target bridge arm based on the absolute value of the instantaneous current value at the switching action moment of each phase of bridge arm in the next period, and injecting disturbance voltage bias bridge arm current into the target bridge arm, so that the instantaneous current value at the switching action moment of each phase of bridge arm is greater than a preset current threshold value. And performing dead zone compensation according to the current direction corresponding to the instantaneous current value at the switching action moment of each phase of bridge arm. Therefore, the dead-zone compensation method based on four-bridge-arm common-mode voltage suppression PWM solves the problem that common-mode voltage suppression PWM fails due to the dead-zone effect. And the safety and the stability of the system are improved.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a dead zone compensation method for common mode voltage suppression PWM of a two-level four-bridge arm converter. Background Art

[0002] The two-level four-bridge-arm converter can be used for AC / DC conversion in three-phase four-wire systems, and is suitable for a variety of medium and low voltage application scenarios such as flexible interconnection of distribution stations and DC remote supply. Due to the need for grounding, if the ordinary PWM working mode is used, a high-frequency common-mode voltage will be excited between the neutral point of the AC side and the DC side, generating leakage current, causing the leakage protection system to operate and the system to shut down.

[0003] In the related art, a common-mode voltage suppression PWM method is used to eliminate the common-mode voltage and leakage current from the source.

[0004] However, the two-level four-arm common-mode voltage suppression PWM in the related art only suppresses the common-mode voltage in steady state, and does not consider the influence of the dead zone. Moreover, the dead zone compensation methods for the common-mode voltage suppression PWM are mostly based on the three-phase three-wire system, which is very different from the three-phase four-wire common-mode voltage suppression PWM and cannot be universally used, which needs to be solved urgently. Summary of the invention

[0005] The present invention provides a dead zone compensation method for common mode voltage suppression PWM of a two-level four-bridge arm converter, so as to solve the problem of common mode voltage suppression PWM failure caused by dead zone effect and improve the safety and stability of the system.

[0006] The first aspect of the present invention provides a dead zone compensation method for common mode voltage suppression PWM of a two-level four-bridge arm converter, comprising the following steps: obtaining the current duty cycle, current output current value and current circuit parameters of each phase bridge arm of the two-level four-bridge arm converter; predicting the instantaneous current value of each phase bridge arm at the switching action moment of the next cycle according to the current duty cycle, current output current value and current circuit parameters of each phase bridge arm; screening out the target bridge arm based on the absolute value of the instantaneous current value of each phase bridge arm at the switching action moment of the next cycle, and injecting a disturbance voltage bias bridge arm current into the target bridge arm, so that the instantaneous current value of each phase bridge arm at the switching action moment is greater than a preset current threshold, and performing dead zone compensation according to the current direction corresponding to the instantaneous current value of each phase bridge arm at the switching action moment.

[0007] Further, in some embodiments, the target bridge arm is screened out based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm, including: judging in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than the preset current threshold; and taking the bridge arm whose absolute value of the instantaneous current value is less than the preset current threshold as the target bridge arm.

[0008] Furthermore, in some embodiments, after determining in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than the preset current threshold, it also includes: obtaining the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold; and performing dead zone compensation according to the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold.

[0009] Further, in some embodiments, the injecting of a disturbance voltage biasing bridge arm current into the target bridge arm includes: determining the current interval in which the target bridge arm is located; injecting a first additional disturbance vector into a reference voltage vector in a direction of at least one first switching cycle according to the current interval in which the target bridge arm is located, and injecting a second additional disturbance vector into the reference voltage vector in a direction of at least one second switching cycle, wherein the first additional disturbance vector and the second additional disturbance vector are opposite.

[0010] According to the dead zone compensation method of the common mode voltage suppression PWM of the two-level four-bridge arm converter provided by the embodiment of the present invention, the instantaneous current prediction method of the traditional three-phase three-wire system is extended to the three-phase four-wire system, and the dead zone compensation method of the instantaneous current prediction and active disturbance detection is combined, and the one-beat delay of the control system is considered, and the calculation is simple and fast, which solves the problem of common mode voltage suppression PWM failure caused by the dead zone effect. The safety and stability of the system operation are improved.

[0011] The second aspect of the present invention provides a dead zone compensation device for common mode voltage suppression PWM of a two-level four-bridge arm converter, including: an acquisition module, used to obtain the current duty cycle, current output current value and current circuit parameters of each phase bridge arm of the two-level four-bridge arm converter; a calculation module, used to predict the instantaneous current value of each phase bridge arm at the switching action moment of the next cycle according to the current duty cycle, current output current value and current circuit parameters of each phase bridge arm; a control module, used to screen out the target bridge arm based on the absolute value of the instantaneous current value of each phase bridge arm at the switching action moment of the next cycle, and inject a disturbance voltage bias bridge arm current into the target bridge arm, so that the instantaneous current value of each phase bridge arm at the switching action moment is greater than a preset current threshold, and dead zone compensation is performed according to the current direction corresponding to the instantaneous current value of each phase bridge arm at the switching action moment.

[0012] Further, in some embodiments, the target bridge arm is screened out based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm, and the control module is specifically used to: determine in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than the preset current threshold; and take the bridge arm whose absolute value of the instantaneous current value is less than the preset current threshold as the target bridge arm.

[0013] Furthermore, in some embodiments, after successively determining whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than the preset current threshold, the control module is also used to: obtain the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold; and perform dead zone compensation according to the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold.

[0014] Furthermore, in some embodiments, the control module is further used to inject a disturbance voltage biasing the bridge arm current into the target bridge arm, and to: determine the current interval in which the target bridge arm is located; and inject a direction of a first additional disturbance vector into a reference voltage vector in at least one first switching cycle and a second additional disturbance vector into the reference voltage vector in at least one second switching cycle according to the current interval in which the target bridge arm is located, wherein the first additional disturbance vector and the second additional disturbance vector are opposite.

[0015] According to the dead zone compensation device of the common mode voltage suppression PWM of the two-level four-bridge arm converter provided by the embodiment of the present invention, the instantaneous current prediction method of the traditional three-phase three-wire system is extended to the three-phase four-wire system, and the dead zone compensation method of the instantaneous current prediction and active disturbance detection is combined, and the one-beat delay of the control system is considered, and the calculation is simple and fast, which solves the problem of common mode voltage suppression PWM failure caused by the dead zone effect. The safety and stability of the system operation are improved.

[0016] A third aspect of the present invention provides an electronic device, comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are configured to execute the dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-arm converter as described in the above embodiment.

[0017] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which is executed by a processor to implement the dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-arm converter as described in the above embodiment.

[0018] A fifth aspect of the present invention provides a computer program product, comprising a computer program, which, when executed by a processor, implements the dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-bridge-arm converter as described in the above embodiment.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0021] Figure 1 A flowchart of a dead zone compensation method for common mode voltage suppression PWM of a two-level four-bridge-arm converter provided according to an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of a circuit topology structure provided according to a specific embodiment of the present invention;

[0023] Figure 3 A schematic diagram of partitioning of a common mode voltage suppression PWM according to a specific embodiment of the present invention;

[0024] Figure 4 A schematic diagram of waveforms of the A-phase output voltage and the bridge arm output current when the reference voltage vector is located in the "X-" region, X=A, B, C, provided according to a specific embodiment of the present invention;

[0025] Figure 5 A schematic diagram of waveforms of the A-phase output voltage and the bridge arm output current when the reference voltage vector is located in the "X+" region, X=A, B, C, according to a specific embodiment of the present invention;

[0026] Figure 6 A schematic diagram of common mode voltage and grid-connected current waveforms after using an instantaneous current prediction method + dead zone compensation according to a specific embodiment of the present invention;

[0027] Figure 7 A schematic diagram of common mode voltage and grid-connected current waveforms after instantaneous current prediction + active disturbance + dead zone compensation according to a specific embodiment of the present invention;

[0028] Figure 8 A flow chart of a dead zone compensation method provided according to a specific embodiment of the present invention;

[0029] Fig. 9 A block diagram of a dead zone compensation device for common mode voltage suppression PWM of a two-level four-bridge-arm converter provided according to an embodiment of the present invention;

[0030] Fig.10 The present invention is a block diagram of an electronic device provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0032] The following describes the dead zone compensation method of the common mode voltage suppression PWM of the two-level four-bridge arm converter according to the embodiment of the present invention with reference to the accompanying drawings. In view of the problem of the failure of the common mode voltage suppression PWM caused by the dead zone effect mentioned in the above background technology, the present invention provides a dead zone compensation method of the common mode voltage suppression PWM of the two-level four-bridge arm converter, in which the current direction at the switching moment is predicted, the characteristics of the common mode voltage suppression PWM are used to simplify the calculation, and the disturbance voltage is actively injected when the current is close to 0, and the bridge arm current is biased so that the direction of the bridge arm current is clear. At the same time, the one-beat delay of the control system is taken into account, and the calculation is simple and fast, thereby solving the problem of the failure of the common mode voltage suppression PWM caused by the dead zone effect.

[0033] Specifically, Figure 1 A schematic flow chart of a dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-bridge-arm converter provided by an embodiment of the present invention.

[0034] In this embodiment, the circuit topology of the two-level four-bridge-arm converter can be as follows: Figure 2 Shown

[0035] Specifically, in the circuit topology diagram, point a is the output point of the A-phase bridge arm of the converter, point b is the output point of the B-phase bridge arm of the converter, point c is the output point of the C-phase bridge arm of the converter, point f is the output point of the neutral line bridge arm of the converter, point O is the midpoint of the DC side of the converter, and point N is the neutral point of the AC side. According to the basic principle of common-mode voltage suppression PWM of a two-level four-bridge-arm converter, the neutral point N of the AC side and the midpoint O of the DC side are always at the same potential, so the circuit model can be greatly simplified.

[0036] like Figure 1 As shown, the dead zone compensation method of the common mode voltage suppression PWM of the two-level four-bridge arm converter includes the following steps:

[0037] In step S101, the current duty cycle, current output current value and current circuit parameters of each phase bridge arm of the two-level four-bridge arm converter are obtained.

[0038] Specifically, the two-level four-bridge converter has four bridge arms, each of which contains two switching devices, such as IGBTs or MOSFETs, capable of switching between two levels. The duty cycle refers to the ratio of the on-time of the switching device to the entire cycle time in a switching cycle, which can be completed through the built-in algorithm of the relevant registers in the microcontroller or digital signal processor. The bridge arm output current refers to the outflow current at the output end of the converter bridge arm. In order to obtain the current bridge arm output current value, it is usually necessary to install a current sensor at the output end of the converter, such as a Hall current sensor. The current sensor converts the current value into a voltage or digital signal, which can be read by the microcontroller or DSP for further processing and analysis. Circuit parameters include voltage, resistance, inductance, etc., which have an important influence on the performance and stability of the converter. For example, the voltage value can be obtained by a voltage sensor or a voltage divider circuit, and parameters such as resistance and inductance usually need to be measured and calculated when designing the converter.

[0039] In step S102, the instantaneous current value of each phase bridge arm at the switching action moment of the next cycle is predicted according to the current duty cycle of each phase bridge arm, the current output current value and the current circuit parameters.

[0040] It should be noted that due to the complexity and nonlinear characteristics of the two-level four-bridge-arm converter, in order to obtain the instantaneous current value at the switching action moment of each phase bridge arm, it is necessary to comprehensively consider the circuit topology and circuit characteristics to obtain the instantaneous current value.

[0041] Furthermore, according to Kirchhoff's law, combined with Figure 2 The circuit topology diagram of the two-level four-bridge-arm converter shown in FIG. 1 is a diagram showing the state equation of the output current of the four-phase bridge arms of the embodiment of the present invention:

[0042]

[0043] Among them, i a is the output current of the A-phase bridge arm of the converter, i b is the output current of the B-phase bridge arm of the converter, i c is the output current of the C-phase bridge arm of the converter, i f is the output current of the neutral bridge arm of the converter, u ao is the voltage between point a and point O, u bo is the voltage between point b and point O, u co is the voltage between point c and point O, u fo is the voltage between point f and point O, u Ca is the voltage on the A phase filter capacitor, u Cb is the voltage on the B phase filter capacitor, u Ccis the voltage on the C-phase filter capacitor, L1 is the single-phase inductance of the ABC three-phase inductance on the AC side, L0 is the inductance of the neutral line on the converter side, and t is the time.

[0044] Furthermore, the instantaneous value of the current at the switching moment can be derived. For phase F, it can be seen from the above formula that in steady state, the current must be greater than 0 on the falling edge of the voltage of phase F, and the current must be less than 0 on the rising edge of the voltage. Therefore, the dead zone of phase F does not produce a dead zone effect, and dead zone compensation is not required. For three phases ABC, due to the common-mode voltage suppression PWM characteristic, the circuit can achieve three-phase decoupling, that is, the state equation of phase A only contains the variables of phase A, and does not contain the variables of two phases BC and phase F, so the three phases ABC can be calculated separately.

[0045] It should be noted that for the common-mode voltage suppression PWM of the two-level four-bridge-arm converter, the order of the vectors and the order of the increase and decrease of the current in each switching cycle are related to the sector where the current reference voltage vector is located. Figure 3 The common-mode voltage suppression PWM of the two-level four-leg converter is further explained.

[0046] Figure 3 A schematic diagram of partitioning of a common mode voltage suppression PWM according to an embodiment of the present invention.

[0047] like Figure 3 As shown, phase A is used as an example for explanation. Phases BC are similar. For phase A, when the reference voltage vector is located at Figure 2 When the reference voltage is in the A+ region (i.e., the upper half plane), the modulation wave of phase A is in the shape of "Λ", with the peak located in the center of the switching cycle and the trough located on both sides, which will make the output voltage of phase A present a "concave" shape, with high levels distributed on both sides of the switching cycle and low levels located in the center of the switching cycle. On the contrary, when the reference voltage is in the A- region (lower half plane), the modulation wave of phase A is in the shape of "V", with the peak located on both sides of the switching cycle and the trough located in the middle, which will make the output voltage of phase A present a "convex" shape, with low levels distributed on both sides of the switching cycle and high levels located in the center of the switching cycle. The increase and decrease trends of the current in these two cases are different, so they are discussed separately below.

[0048] Furthermore, when the reference voltage vector is located in the "X-" region, X = A, B, C, the waveforms of the A phase output voltage and the bridge arm output current are as follows: Figure 4 In the figure, the dotted line indicates the boundary of the switching cycle, α(n) is the duty cycle of the nth cycle, i(n) is the current sampling value at the beginning of the nth cycle, and i rs (n) is the current at the rising edge of the voltage (that is, the current when the lower tube is turned off and the upper tube is turned on), i fl(n) is the current at the falling edge of the voltage (that is, the current when the lower tube is turned on and the upper tube is turned off). Assuming that the current is the nth cycle, the duty cycle of the n+1th cycle and before is known, the current value before the nth cycle is known, and the current value after the nth cycle is unknown, which is marked with "*" in the figure, indicating that calculation and prediction are required.

[0049] Furthermore, by using formula (1) and formula (2), the current prediction value at the end of the nth cycle can be obtained:

[0050]

[0051] Among them, T sw is the switching period, U dc is the DC bus voltage. Then, the instantaneous current value at the rising and falling edges of the voltage in the next switching cycle can be calculated according to formula (3):

[0052]

[0053] Furthermore, when the reference voltage vector is located in the "X+" region, X = A, B, C, the waveforms of the A phase output voltage and the bridge arm output current are as follows: Figure 5 shown. Figure 5 The output voltage and current waveforms of phase A when the reference voltage is in the A+ region are shown in Figure 4. According to formula (4), the instantaneous current values ​​at the rising and falling edges of the voltage in the next switching cycle can be calculated:

[0054]

[0055] Thus, the instantaneous current value at the switching moment of a certain phase in the next cycle can be predicted.

[0056] In step S103, the target bridge arm is selected based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm in the next cycle, and a disturbance voltage is injected into the target bridge arm to bias the bridge arm current, so that the instantaneous current value at the switching action moment of each phase bridge arm is greater than the preset current threshold, and dead zone compensation is performed according to the current direction corresponding to the instantaneous current value at the switching action moment of each phase bridge arm.

[0057] Furthermore, in some embodiments, the target bridge arm is selected based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm, including: judging in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than a preset current threshold; and taking the bridge arm whose absolute value of the instantaneous current value is less than the preset current threshold as the target bridge arm.

[0058] It should be noted that since the instantaneous current value may be positive or negative, in order to eliminate the influence of direction, it is necessary to take the absolute value of the monitored instantaneous current value. In this way, no matter what the direction of the current is, it can be compared and screened according to its magnitude. If the absolute value of the instantaneous current of a bridge arm is less than the preset current threshold, then the bridge arm is regarded as the target bridge arm. This means that under the current control strategy or operating conditions, the current level of this bridge arm is low and needs to be actively biased. In this way, the bridge arm with a low current level in the multi-phase bridge arm system can be accurately identified, thereby achieving effective control and optimization of the current.

[0059] Further, in some embodiments, injecting a disturbance voltage to bias the bridge arm current into the target bridge arm includes: determining the current interval in which the target bridge arm is located; injecting a first additional disturbance vector into the reference voltage vector in at least one first switching cycle according to the current interval in which the target bridge arm is located, and injecting a second additional disturbance vector into the reference voltage vector in at least one second switching cycle, wherein the first additional disturbance vector and the second additional disturbance vector are opposite.

[0060] Specifically, the current interval can be divided according to the specific needs and conditions of the system, for example, it can be divided into a low current interval, a medium current interval, and a high current interval. The purpose of determining the current interval is to control the current more accurately and adopt different control strategies for different current levels. According to the current interval in which the target bridge arm is located, the additional disturbance vector injected into the reference voltage vector in multiple switching cycles can be determined, wherein the first additional disturbance vector and the second additional disturbance vector are opposite to each other in order to balance the current fluctuation and reduce the harmonic component. If the target bridge arm is in a high current interval, it may be necessary to inject a larger disturbance vector to reduce the current level; if it is in a low current interval, it may be necessary to inject a smaller disturbance vector or keep the original control strategy unchanged. At the same time, by injecting disturbance vectors in opposite directions, the current waveform can be further smoothed to reduce fluctuations and distortion.

[0061] Furthermore, if Figure 6 As shown, Figure 6 (a) is the voltage and current waveform of the dead zone compensation algorithm. Figure 6 (b) shows the voltage and current waveforms predicted by increasing the instantaneous current.

[0062] It should be noted that due to the inevitable errors in the system, such as sampling current errors, circuit parameter errors, various interferences, etc., the current prediction cannot be completely accurate. Therefore, when the current is close to 0, the predicted direction may be wrong, resulting in wrong current direction judgment, wrong dead zone compensation, and failure to eliminate or even causing common mode voltage spikes. Therefore, when the predicted current value of the current ripple prediction method of the present invention satisfies that its absolute value is less than the threshold current i thWhen the prediction is considered not accurate enough to determine the current direction, an active disturbance detection method is needed.

[0063] First, determine the threshold current i according to the actual situation of the system th Its specific value is affected by various factors such as current measurement accuracy, interference conditions, and system parameter accuracy, and represents the maximum error of the predicted current. Taking phase A as an example: When any predicted current of phase A (including i fl and i rs , uniformly denoted as i prid ) satisfies the relation 0 prid th When the positive additional disturbance vector V is injected into the reference voltage vector for the next N1 consecutive switching cycles, irpt , so that the predicted current value at the switching moment of the next N1 cycles is always greater than i th ; Then, a negative additional disturbance vector -N1 / N2*V is injected into the reference voltage vector for N2 consecutive switching cycles irpt , so that the current quickly passes through zero and is less than -i th On the contrary, when the A phase arbitrarily predicted current satisfies the relation -i th prid <0, a negative additional disturbance vector -V is injected into the reference voltage vector for N1 consecutive switching cycles. irpt , so that the predicted current value at the switching moment of the next N1 cycles is always less than -i th ; Then, a positive additional disturbance vector N1 / N2*V is injected into the reference voltage vector for N2 consecutive switching cycles irpt , so that the current quickly passes through zero and is less than -i th .

[0064] Specifically, N2 is as small as possible within the range of the PWM modulator not exceeding the linear modulation ratio, and is preferably 1. After determining N2, N1 needs to satisfy the relationship shown in formula (5):

[0065]

[0066] Among them, I nom is the effective value of the fundamental current under the current working condition. In order to minimize the impact of the disturbance on the power quality of the power grid, N1 should be taken as the minimum integer that satisfies formula (5).

[0067] Furthermore, the disturbance vector V irpt The direction is the positive direction of the α axis, and the vector length satisfies the inequality shown in formula (6):

[0068]

[0069] In order to minimize the impact of disturbance on the power quality of the grid, V​​​irpt It should be selected as the minimum value of the full formula (6). After completing the above design, if the modulation is saturated, increase N2 and repeat the above design process until saturation no longer occurs in the modulation.

[0070] Furthermore, when the instantaneous current prediction method and the active disturbance detection method are used simultaneously, various parameters in the active disturbance detection are reasonably set, such as Figure 7 As shown, Figure 7 (a) is the voltage and current waveform of the dead zone compensation algorithm. Figure 7 (b) is a voltage and current waveform diagram with the addition of instantaneous current prediction and active disturbance methods. After dead zone compensation, the common-mode voltage spikes caused by the dead zone effect can be completely eliminated, thereby greatly suppressing the leakage current and ensuring that the low-impedance grounding system will not be shut down due to leakage current protection. After adopting the active disturbance detection method, the quality of the grid-connected current is reduced compared to when only the instantaneous current prediction method is adopted, but the current quality is still improved compared to before any dead zone compensation algorithm is adopted. Therefore, it can be considered that the instantaneous current prediction + active disturbance detection method of the present invention can eliminate the common-mode voltage spikes caused by the dead zone effect without affecting the quality of the grid-connected current.

[0071] It should be noted that the dead zone compensation method based on active disturbance provided in the embodiment of the present invention is an optional method, not a mandatory method.

[0072] In order to enable relevant technical personnel in the art to better understand the dead-zone compensation method of the common-mode voltage suppression PWM of the two-level four-bridge-arm converter according to the embodiment of the present invention, it will be further described below in combination with specific implementations.

[0073] Figure 8 The dead zone compensation method flow chart provided in a specific embodiment of the present invention includes the following steps:

[0074] In step S801, the three-phase duty cycle is obtained according to the position of the current reference voltage vector, and the instantaneous current value at each switch action moment is obtained by combining the sampled current value and the circuit parameter model.

[0075] In step S802, it is determined whether the instantaneous current is less than a threshold value. If the instantaneous current is less than the threshold value, step S803 is executed. If the instantaneous current is greater than the threshold value, step S804 is executed.

[0076] In step S803, since the instantaneous current is less than the threshold at this time, an active disturbance detection method is added, and the bridge arm current is biased by actively injecting a disturbance voltage to increase the current amplitude and control the direction.

[0077] In step S804, the current direction is determined.

[0078] In step S805, dead zone compensation is performed and a three-phase modulated wave is output.

[0079] Thus, according to the current direction at the switching moment, the dead zone effect compensation can be completed to suppress the common mode voltage spike. The present invention is used for the dead zone compensation of the common mode voltage suppression PWM of the two-level four-bridge arm converter, which can effectively suppress the common mode voltage spike caused by the dead zone effect, improve the effect of common mode voltage suppression, and does not require additional hardware cost.

[0080] Furthermore, in some embodiments, after determining in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than a preset current threshold, it also includes: obtaining the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold; and performing dead zone compensation according to the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold.

[0081] Among them, the purpose of dead zone compensation is to adjust the switching moment of the switching device to eliminate the current waveform distortion caused by factors such as switching delay and conduction voltage drop. Specifically, if the current direction is positive (for example, flowing from the power supply to the load), it may be necessary to turn on the corresponding switching device in advance to ensure that the current can flow smoothly through the bridge arm. On the contrary, if the current direction is negative (for example, flowing from the load back to the power supply), it may be necessary to delay turning off the corresponding switching device to avoid truncation or distortion of the current waveform.

[0082] It should be noted that the preset current threshold can be set manually or determined through experimental data, and there is no limitation here.

[0083] According to the dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-arm converter provided by an embodiment of the present invention, the instantaneous current prediction method of a traditional three-phase three-wire system is extended to a three-phase four-wire system, and the dead-zone compensation method of combining instantaneous current prediction and active disturbance detection takes into account the one-beat delay of the control system, and the calculation is simple and fast, which solves the problem of common-mode voltage suppression PWM failure caused by the dead-zone effect and improves the safety and stability of system operation.

[0084] Next, the dead-zone compensation device for common-mode voltage suppression PWM of a two-level four-bridge-arm converter proposed in accordance with an embodiment of the present invention will be described with reference to the accompanying drawings.

[0085] Fig. 9 It is a block diagram of a dead zone compensation device for common mode voltage suppression PWM of a two-level four-bridge-arm converter according to an embodiment of the present invention.

[0086] like Fig. 9 As shown, the dead zone compensation device 10 of the common mode voltage suppression PWM of the two-level four-bridge-arm converter includes: an acquisition module 100 , a calculation module 200 and a control module 300 .

[0087] Among them, the acquisition module 100 is used to obtain the current duty cycle, current output current value and current circuit parameters of each phase bridge arm of the two-level four-bridge arm converter; the calculation module 200 is used to obtain the instantaneous current value of each phase bridge arm at the switching action time according to the current duty cycle, current output current value and current circuit parameters of each phase bridge arm; the control module 300 is used to screen out the target bridge arm based on the absolute value of the instantaneous current value at the switching action time of each phase bridge arm, and inject a disturbance voltage to bias the bridge arm current into the target bridge arm until the instantaneous current value at the switching action time of each phase bridge arm is greater than the preset current threshold, and perform dead zone compensation according to the current direction corresponding to the instantaneous current value at the switching action time of each phase bridge arm.

[0088] Furthermore, in some embodiments, the control module 300 is specifically used to: determine in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than a preset current threshold; and take the bridge arm whose absolute value of the instantaneous current value is less than the preset current threshold as the target bridge arm.

[0089] Furthermore, in some embodiments, after determining in turn whether the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm is less than a preset current threshold, the control module 300 is also used to: obtain the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold; and perform dead zone compensation according to the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold.

[0090] Furthermore, in some embodiments, the control module 300 is also used to: determine the current interval in which the target bridge arm output current is located; and inject the direction of a first additional disturbance vector into the reference voltage vector in at least one first switching cycle according to the current interval in which the target bridge arm is located, and inject the direction of a second additional disturbance vector into the reference voltage vector in at least one second switching cycle, wherein the first additional disturbance vector and the second additional disturbance vector are opposite.

[0091] It should be noted that the above explanation of the dead-zone compensation method embodiment of the common-mode voltage suppression PWM of the two-level four-bridge-arm converter is also applicable to the dead-zone compensation device of the common-mode voltage suppression PWM of the two-level four-bridge-arm converter of this embodiment, and will not be repeated here.

[0092] According to the dead-zone compensation device for common-mode voltage suppression PWM of a two-level four-bridge-arm converter provided by an embodiment of the present invention, the instantaneous current prediction method of a traditional three-phase three-wire system is extended to a three-phase four-wire system, and the dead-zone compensation method of combining instantaneous current prediction and active disturbance detection is taken into account, the one-beat delay of the control system is taken into account, and the calculation is simple and fast, which solves the problem of common-mode voltage suppression PWM failure caused by the dead-zone effect and improves the safety and stability of system operation.

[0093] Fig.10 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. The electronic device may include:

[0094] A memory 1001 , a processor 1002 , and a computer program stored in the memory 1001 and executable on the processor 1002 .

[0095] When the processor 1002 executes the program, the dead zone compensation method of the common mode voltage suppression PWM of the two-level four-bridge-arm converter provided in the above embodiment is implemented.

[0096] Furthermore, the electronic device further comprises:

[0097] The communication interface 1003 is used for communication between the memory 1001 and the processor 1002 .

[0098] The memory 1001 is used to store computer programs that can be executed on the processor 1002 .

[0099] The memory 1001 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0100] If the memory 1001, the processor 1002 and the communication interface 1003 are implemented independently, the communication interface 1003, the memory 1001 and the processor 1002 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus or an Extended Industry Standard Architecture (EISA) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Fig.10 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0101] Optionally, in a specific implementation, if the memory 1001, the processor 1002 and the communication interface 1003 are integrated on a chip, the memory 1001, the processor 1002 and the communication interface 1003 can communicate with each other through an internal interface.

[0102] The processor 1002 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0103] An embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the program is executed by a processor, the dead zone compensation method of the common-mode voltage suppression PWM of the two-level four-bridge-arm converter as described above is implemented.

[0104] An embodiment of the present invention further provides a computer program product, including a computer program, which, when executed by a processor, implements the dead-zone compensation method for common-mode voltage suppression PWM of a two-level four-bridge-arm converter as described in the above embodiment.

[0105] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0106] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "N" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0107] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present invention belong.

[0108] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. If implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit with a logic gate circuit for implementing a logic function on a data signal, a dedicated integrated circuit with a suitable combination of logic gate circuits, etc.

[0109] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

Claims

1. A dead zone compensation method for common mode voltage suppression PWM of a two-level four-bridge-arm converter, characterized in that: The following steps are involved: Obtaining the current duty cycle, current output current value and current circuit parameters of each phase bridge arm of the two-level four-bridge arm converter; Predicting the instantaneous current value of the switching action moment of each phase bridge arm in the next cycle according to the current duty cycle of each phase bridge arm, the current output current value and the current circuit parameters; The target bridge arm is selected based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm in the next cycle, and a disturbance voltage is injected into the target bridge arm to bias the bridge arm current, so that the instantaneous current value at the switching action moment of each phase bridge arm is greater than the preset current threshold, and dead zone compensation is performed according to the current direction corresponding to the instantaneous current value at the switching action moment of each phase bridge arm.

2. The method according to claim 1, characterized in that: The step of selecting a target bridge arm based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm comprises: Determine in sequence whether the absolute value of the instantaneous current value of each phase bridge arm at the switching action moment is less than the preset current threshold; The bridge arm whose absolute value of the instantaneous current value is smaller than the preset current threshold is used as the target bridge arm.

3. The method according to claim 2, characterized in that After successively determining whether the absolute value of the instantaneous current value of the switching action moment of each phase bridge arm is less than the preset current threshold, the method further includes: Obtaining the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold; Dead zone compensation is performed according to the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold.

4. The method according to claim 1, characterized in that The injecting a disturbance voltage into the target bridge arm to bias the bridge arm current comprises: Determining the current interval in which the target bridge arm is located; According to the direction of the first additional disturbance vector injected into the reference voltage vector in at least one first switching cycle in the current interval where the target bridge arm is located, the direction of the second additional disturbance vector injected into the reference voltage vector in at least one second switching cycle, wherein the first additional disturbance vector and the second additional disturbance vector are opposite.

5. A dead zone compensation device for common mode voltage suppression PWM of a two-level four-bridge-arm converter, characterized in that: The device comprises: An acquisition module, used to acquire the current duty cycle, current output current value and current circuit parameters of each phase bridge arm of the two-level four-bridge arm converter; A calculation module, used for predicting the instantaneous current value of each phase bridge arm at the switching action moment of the next cycle according to the current duty cycle of each phase bridge arm, the current output current value and the current circuit parameters; A control module is used to select a target bridge arm based on the absolute value of the instantaneous current value at the switching action moment of each phase bridge arm in the next cycle, and inject a disturbance voltage bias bridge arm current into the target bridge arm, so that the instantaneous current value at the switching action moment of each phase bridge arm is greater than a preset current threshold, and dead zone compensation is performed according to the current direction corresponding to the instantaneous current value at the switching action moment of each phase bridge arm.

6. The device according to claim 5, characterized in that The control module is specifically used for: Determine in sequence whether the absolute value of the instantaneous current value of each phase bridge arm at the switching action moment is less than the preset current threshold; The bridge arm whose absolute value of the instantaneous current value is smaller than the preset current threshold is used as the target bridge arm.

7. The device according to claim 5, characterized in that After successively determining whether the absolute value of the instantaneous current value of the switching action moment of each phase bridge arm is less than the preset current threshold, the control module is further used to: Obtaining the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold; Dead zone compensation is performed according to the current direction corresponding to the bridge arm whose absolute value of the instantaneous current value is greater than or equal to the preset current threshold.

8. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the dead zone compensation method for common mode voltage suppression PWM of a two-level four-bridge arm converter as described in any one of claims 1 to 4.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: The program is executed by a processor to implement the dead zone compensation method of common mode voltage suppression PWM of a two-level four-bridge-arm converter as described in any one of claims 1 to 4.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the dead zone compensation method of the common mode voltage suppression PWM of the two-level four-bridge arm converter is implemented as described in any one of claims 1 to 4.

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