A networked converter current reconstruction method and system of a single current sensor

Abstract

The application provides a network configuration type converter current reconstruction method and system of a single current sensor, and belongs to the technical field of power electronics. The method comprises the following steps: first, sampling a direct current bus current and reconstructing a temporary three-phase current, and converting to a dq0 coordinate system; then, judging whether the action time of an effective voltage vector is less than a preset minimum sampling time; if yes, keeping the d and q axis current reconstruction values of the last switching period unchanged, otherwise updating the d and q axis current reconstruction values with the current temporary values; finally, inversely converting to obtain three-phase alternating current reconstruction values. The application solves the problem of current reconstruction distortion of the traditional method when the sampling time is too short, and realizes high-precision reconstruction in the full working range. Compared with the traditional scheme, the number of sensors is reduced by more than 70%, the steady-state power control error is less than 1%, and the system cost and volume are reduced.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology, specifically relating to a current reconstruction method and system for a grid-type converter with a single current sensor. Background Technology

[0002] As a key technology in highly electronic power systems, grid-connected converters need to perform multiple functions, including power control, voltage control, and virtual impedance control. Traditional grid-connected converters typically require a large number of sensors, including three-phase inverter-side current sensors, three-phase filter capacitor voltage sensors, three-phase grid-side current sensors, DC bus voltage sensors, and DC bus current sensors, totaling more than ten sensors. The use of a large number of sensors not only increases the hardware cost and size of the system but also introduces sampling inconsistency errors and additional points of failure, reducing the overall reliability of the system.

[0003] To reduce the number of sensors, existing research has proposed observer-based current estimation methods that simplify system configuration by reducing the number of AC current or voltage sensors. Among these, the method of reconstructing three-phase AC current using a single DC bus current sensor has attracted attention due to its low cost and simple structure. This method uses a space vector pulse width modulation strategy to sample the DC bus current under different switching states and then deduce the three-phase AC current based on the correspondence between the switching states and the three-phase currents.

[0004] However, existing single DC bus current reconstruction methods have the following problems in practical applications: when the effective voltage vector used for sampling has too short an action time to complete current sampling, the existing methods cannot guarantee that the reconstructed current will not be distorted. Specifically, during space vector pulse width modulation, the action time of the two effective voltage vectors varies within each switching cycle. When the action time of a certain effective voltage vector is too short, the DC bus current cannot be established and sampled within such a short time, resulting in the inability to obtain an effective current sample value in that switching state. This region where sampling is impossible due to insufficient effective vector action time usually appears near the peaks and troughs of the modulation signal. In such regions, DC bus current sampling information is missing, and traditional reconstruction methods cannot accurately calculate the three-phase AC current, leading to distortion or error in the reconstructed current and affecting the control performance of the grid-type converter. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a current reconstruction method and system for a grid-type converter using a single current sensor.

[0006] To achieve the above objectives, the present invention provides a current reconstruction method for a grid-type converter using a single current sensor, comprising: The DC bus current signal of the target grid converter is acquired in real time by a single current sensor, and the three-phase modulation signal of the target grid converter is obtained.

[0007] The effective voltage vectors within the current switching cycle are calculated based on the three-phase modulation signal, and their respective durations are denoted as the first duration and the second duration. The sampleable time of the DC bus current signal is determined based on the first duration and the second duration. The DC bus current signal is sampled based on the sampleable time to obtain multiple instantaneous values ​​of the DC bus current and the switching state corresponding to each sampling time.

[0008] The instantaneous values ​​of the three-phase AC current are reconstructed based on the instantaneous values ​​of multiple DC bus currents and the corresponding switch states at each sampling time to obtain the temporary three-phase current. The temporary three-phase current is transformed into the synchronously rotating dq0 coordinate system to obtain the temporary d-axis current component and the temporary q-axis current component. If either the first action time or the second action time in the current switching cycle is less than the preset minimum sampling time, the values ​​of the d-axis current component and the q-axis current component of the previous switching cycle are kept unchanged. Otherwise, the temporary d-axis current component and the temporary q-axis current component of the current switching cycle are used as the updated values ​​of the d-axis current component and the q-axis current component of this cycle.

[0009] The updated d-axis and q-axis current component values ​​are inversely transformed back to the three-phase stationary coordinate system to obtain the final reconstructed three-phase AC current values.

[0010] Preferably, the preset minimum sampling time is obtained by adding the dead time, the current settling time, and the analog-to-digital conversion time; wherein, the dead time is the delay time set to prevent the power switch from shooting through, the current settling time is the time required for the DC bus current to reach stability after the switch action, and the analog-to-digital conversion time is the time required to convert the sampled analog current signal into a digital quantity.

[0011] Preferably, the first action time is obtained by multiplying the switching period by the difference between the median value and the minimum value of the three-phase modulation signal, and then dividing by two; the second action time is obtained by multiplying the switching period by the difference between the maximum value and the median value of the three-phase modulation signal, and then dividing by two.

[0012] Preferably, the temporary three-phase current is transformed to a synchronously rotating dq0 coordinate system using a phase angle, which is provided by the power controller of the grid converter.

[0013] Preferably, the method for determining the sampleable time includes: determining four sampling times within one switching cycle based on the first action time and the second action time, wherein two sampling times correspond to the middle region of the first action time, and the other two sampling times correspond to the middle region of the second action time.

[0014] Preferably, the step of reconstructing the instantaneous value of the three-phase AC current based on multiple instantaneous values ​​of DC bus current and the corresponding switch states at each sampling time specifically includes: assigning the instantaneous value of the DC bus current at each sampling time to the temporary current value of the corresponding phase according to the correspondence table between switch states and three-phase AC current, wherein when the switch state is that only one phase upper bridge arm is conducting, the DC bus current is equal to the current of that phase; when the switch state is that two phase upper bridge arms are conducting, the DC bus current is equal to the reverse value of the current of the unconducted phase.

[0015] Preferably, in the process of keeping the values ​​of the d-axis current component and the q-axis current component unchanged in the previous switching cycle, the d-axis current component and the q-axis current component are DC quantities during steady-state operation, and their rate of change during transient operation is less than a set speed.

[0016] The present invention also provides a current reconstruction system for a grid-type converter with a single current sensor, comprising: The data acquisition module is used to acquire the DC bus current signal of the target grid converter in real time using a single current sensor, and to obtain the three-phase modulation signal of the target grid converter.

[0017] The sampling module is used to calculate the duration of each of the two effective voltage vectors in the current switching cycle based on the three-phase modulation signal, and denoted as the first duration and the second duration, respectively; determine the sampleable time of the DC bus current signal based on the first duration and the second duration; sample the DC bus current signal based on the sampleable time to obtain multiple instantaneous values ​​of DC bus current and the switching state corresponding to each sampling time.

[0018] The reconstruction module is used to reconstruct the instantaneous values ​​of the three-phase AC current based on multiple instantaneous values ​​of DC bus current and the corresponding switch states at each sampling time, to obtain temporary three-phase currents; transform the temporary three-phase currents to the synchronously rotating dq0 coordinate system to obtain temporary d-axis current components and temporary q-axis current components; if either the first action time or the second action time in the current switching cycle is less than the preset minimum sampling time, the d-axis current component and q-axis current component values ​​of the previous switching cycle are kept unchanged; otherwise, the temporary d-axis current component and temporary q-axis current component of the current switching cycle are used as the updated d-axis current component and q-axis current component values ​​for this cycle; the updated d-axis current component and q-axis current component values ​​are inversely transformed back to the three-phase stationary coordinate system to obtain the final reconstructed three-phase AC current values.

[0019] The present invention also provides a computer device, including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement any of the steps in the single-current sensor grid converter current reconstruction method.

[0020] The present invention also provides a computer-readable storage medium storing a computer program that, when loaded by a processor, can execute any of the steps in the single-current-sensor grid converter current reconstruction method.

[0021] The present invention provides a current reconstruction method for a grid-type converter using a single current sensor, which has the following advantages: First, the reconstructed temporary three-phase current is transformed to a synchronously rotating dq0 coordinate system, converting the time-varying sinusoidal AC quantity into approximately DC d-axis and q-axis components under steady-state conditions. Then, it is determined whether the first or second action time within the current switching cycle is less than a preset minimum sampling time. If it is less, it indicates that the current state is in an unobservable region where effective sampling is not possible. In this case, the d-axis and q-axis current values ​​of the previous switching cycle are kept unchanged; otherwise, the current temporary d-axis and q-axis current values ​​are used as the reconstructed values ​​updated for this cycle. Finally, the updated d-axis and q-axis current values ​​are transformed back to the three-phase stationary coordinate system to obtain the final reconstructed three-phase AC current values. This method does not require any additional hardware; it solves the problem of reconstruction distortion in traditional methods when the sampling time is too short by using only logical judgment and numerical holding operations.

[0022] This method completely eliminates current reconstruction distortion in unobservable regions, achieving continuous and accurate reconstruction across the entire operating range. Since the dq-axis current is a DC current in steady state and changes slowly in transient state, the error introduced by the strategy is minimal. Experiments show that the steady-state power control error is less than 1%, comparable to the accuracy of traditional schemes using all sensors. Only a single DC bus current sensor is needed to complete the three-phase current reconstruction. Combined with one DC bus voltage sensor and two AC voltage sensors, the total number of sensors is only four, a reduction of more than 70% compared to the 14 sensors in traditional schemes, significantly reducing system cost, size, and failure rate. Attached Figure Description

[0023] To more clearly illustrate the embodiments and design schemes of the present invention, the accompanying drawings required for this embodiment will be briefly described below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a flowchart of a current reconstruction method for a grid-type converter with a single current sensor according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the overall structure of the grid-type converter system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the converter-side current path in the switching state (100) provided in an embodiment of the present invention; Figure 4This is a schematic diagram of the converter-side current path in the switching state (110) provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a three-phase modulation signal under the space vector pulse width modulation (SVPWM) strategy provided in an embodiment of the present invention; Figure 6 This is a waveform diagram of the PWM wave and DC bus current during a switching cycle provided in an embodiment of the present invention; Figure 7 This is a comparison diagram of the simulated waveforms of the reconstructed current and the measured current, and the reconstructed power and the measured power provided in the embodiments of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0026] like Figure 2 As shown, the grid-type converter system used in this embodiment includes a DC power supply, a three-phase voltage source converter, an LCL filter, and a power grid. The three-phase voltage source converter consists of six power switching transistors S... g1 To S g6 The LCL filter is composed of converter-side inductor L... gi Filter capacitor C gf and grid-side inductance L gg Composition. Regarding sensor configuration, unlike traditional solutions that require multiple AC current sensors, this embodiment of the invention configures only one current sensor i on the DC bus. gdc A voltage sensor v is configured on the DC bus. gdc And configure two voltage sensors (e.g., V) on the AC side. gfa and v gfb The phase angle θ of the power controller output. g Used for subsequent coordinate transformation, converting the three-phase current to the synchronously rotating dq0 coordinate system.

[0027] To reconstruct the three-phase AC current using a single DC bus current sensor, this embodiment employs a space vector pulse width modulation (SVPWM) strategy. Figure 3 and Figure 4 The relationship between DC bus current and converter-side current under different switching states is shown. Figure 3 When the switch state is (100), only the upper bridge arm of phase A is conducting, and the DC bus current i gdc Equal to phase A current + i gia . Figure 4When the switch state is (110), the upper bridge arms of phases A and B are on, the lower bridge arm of phase C is on, and the DC bus current i gdc Equal to the reverse of the C-phase current −i gic .

[0028] Table 1 summarizes the correspondence between DC bus current and three-phase current under all switching conditions.

[0029] Table 1 Relationship between switch state and DC link current However, in practical applications, due to the existence of dead time and current settling time, traditional reconstruction methods cannot accurately sample in certain intervals.

[0030] like Figure 5 As shown, in the three-phase modulation signal under the SVPWM strategy, τ1 and τ2 are two different time intervals. Figure 6 The figure shows the PWM waveform and DC bus current waveform during one switching cycle, with the dead time T marked. dt Current settling time T cst and analog-to-digital conversion time T ad The sum of these three factors constitutes the minimum sampling time T. min = T dt + T cst + T ad Where dt represents the dead time, cst represents the current settling time, and ad represents the analog-to-digital conversion time. To ensure sampling accuracy, the effective voltage vector's duration must be greater than T. min But... Figure 5 In the τ2 interval, the effective vector's duration is too short to allow for reliable sampling; this is known as the "unobservable region". Figure 5 Three-phase modulation signal u gia u gib u gic The amplitude is determined by the DC bus voltage v gdc The modulation ratio determines the relative magnitude of the voltage command for each phase.

[0031] To address the aforementioned problems, this invention provides a current reconstruction method for a grid-type converter using a single current sensor. Specifically, it relates to a method and system for current reconstruction of a grid-type converter based on a single DC bus current sensor, particularly a method for achieving accurate AC side current reconstruction using only a single DC bus current sensor. Through an improved reconstruction strategy, the problem of current reconstruction distortion in unobservable regions, a problem inherent in traditional methods, is effectively solved, achieving high-precision AC current and power measurement. Figure 1 As shown, it includes the following steps:

[0032] S1. Calculate the effective vector action time and sampling time. According to the three-phase modulation signal u output by the voltage controller gia u gib u gic Determine its maximum, median, and minimum values, denoted as max, mid, and min, respectively. Based on... Figure 6 Based on the waveform shown and the principle of similar triangles, the first effective time T is calculated using the following formula. eff1 Second effective time T eff2 .

[0033] (1) (2) Among them, T s T is the switching period; eff1 and T eff2 These represent the first effective time (corresponding to the τ1 interval) and the second effective time (corresponding to the τ2 interval), respectively, where eff represents the effective action time. Based on T eff1 and T eff2 Determine the four sampling times t within a switching cycle. s1 t s2 t s3 t s4 ,like Figure 6 As shown.

[0034] S2, Sample DC bus current Simultaneously with generating the PWM signal, at the sampling time t determined by S1... s1 To t s4 The DC bus current sensor samples the data to obtain the instantaneous value i of the DC bus current. gdc (t s1 ) to i gdc (t s4 ).

[0035] S3, Reconstruct temporary three-phase current Based on the relationship between the switch state and the DC bus current shown in Table 1, the i obtained by sampling using S2 is used... gdc The values ​​are used to reconstruct three temporary AC current values ​​i. gia _ temp i gib_temp i gic_temp In the subscripts gia_temp, gib_temp, and gic_temp, g represents the converter, i represents the converter side, a, b, and c represent the three phases A, B, and C respectively, and temp represents temporary. For example, when the switch state is (100), let i gia_temp = i gdcWhen the switch state is (110), let i gic_temp = − i gdc .

[0036] S4, Coordinate Transformation Based on the three-phase modulation signal of the converter, the duration of action of two effective voltage vectors in the next switching cycle of the space vector pulse width modulation (SVPWM) strategy is calculated; based on the duration of action of the effective voltage vectors, the sampleable time of the DC bus current is determined; at the sampleable time, the signal of a single DC bus current sensor is sampled to obtain multiple instantaneous values ​​of DC bus current; based on the multiple instantaneous values ​​of DC bus current and their corresponding switching states, the instantaneous values ​​of the three-phase AC current are reconstructed; the reconstructed instantaneous values ​​of the three-phase AC current are transformed to the synchronously rotating dq0 coordinate system to obtain the d-axis and q-axis current components.

[0037] Specifically, the temporary three-phase current i obtained from S3 gia_temp i gib_temp i gic_temp Transform to the synchronously rotating dq0 coordinate system to obtain the temporary d-axis current component i. gid_temp and temporary q-axis current component i giq_temp The phase angle θ used for coordinate transformation g Provided by the active power controller.

[0038] S5. Determine if it is an unobservable region. Compare the T calculated by S1 eff1 T eff2 With the preset minimum sampling time T min If T is satisfied eff1 <T min or T eff2 <T min If the current time is within the unobservable region, then S6 is executed; otherwise, it is within the observable region, and S7 is executed.

[0039] S6. Maintain the reconstructed value from the previous time step. Determine whether the current moment is in an unobservable region, defined as an interval where the effective voltage vector action time is less than a preset minimum sampling time; if in an unobservable region, keep the d-axis and q-axis current reconstruction values ​​of the previous moment unchanged; if in an observable region, update the currently calculated d-axis and q-axis current components to the current reconstruction values; transform the updated d-axis and q-axis current reconstruction values ​​back to the three-phase stationary coordinate system to obtain the final three-phase AC current reconstruction values.

[0040] In the unobservable region, since reliable sampling values ​​cannot be obtained, the d-axis and q-axis current reconstruction values ​​remain unchanged to avoid current reconstruction distortion, i.e., they are not updated.

[0041] Within the observable region, the temporary values ​​calculated by S4 are updated with the reconstructed d-axis and q-axis current values ​​at the current moment, that is, let i gid_rec = i gid_temp i giq_rec = i giq_temp In the subscripts gid_rec, g represents the converter, i represents the converter side, d / q represents the d-axis and q-axis of the synchronous rotating coordinate system, and rec represents the reconstructed.

[0042] As an alternative implementation, the effective voltage vector's duration includes a first effective time T. eff1 Second effective time T eff2 The calculation formula is as follows: (3) (4) Among them, T s T is the switching period; eff1 and T eff2 These represent the first effective time (corresponding to the τ1 interval) and the second effective time (corresponding to the τ2 interval), respectively, where eff represents the effective action time; max(·), mid(·), and min(·) are the maximum, intermediate, and minimum values ​​of the three-phase modulated signal, respectively; u gia 、u gib 、u gic These represent the modulation wave voltages on the A, B, and C phase converter sides, respectively. v gdc This represents the DC bus voltage, where dc represents the DC bus.

[0043] Minimum sampling time T min Dead time T dt DC bus current settling time T cst and analog-to-digital conversion time T ad The sum. The unobservable region is T. eff1 <T min or T eff2 <T min The interval is defined. As an alternative implementation, within the observable region, the d-axis and q-axis current reconstruction values ​​are updated to the calculated values; within the unobservable region, the d-axis and q-axis current reconstruction values ​​remain unchanged. Since the current in the dq coordinate system is a DC quantity in steady state, this strategy can effectively improve the current reconstruction accuracy.

[0044] As an alternative implementation, the system also includes a Luhnberg Extended State Observer (LESO) to estimate the grid-side current based on the reconstructed converter-side current and existing voltage measurements, thereby achieving virtual impedance control. Since the current is DC in the dq coordinate system, the holding strategy in the unobservable region does not introduce significant errors, ensuring the continuity and accuracy of the reconstructed current across the entire operating range. Simulation and experimental results demonstrate that this reconstruction method achieves high-precision power control with a steady-state power control error of less than 1%.

[0045] This invention enables high-performance control of a grid-type converter using a total of 4 sensors (1 DC current, 1 DC voltage, and 2 AC voltages). Compared with the traditional 14-sensor scheme, the number of sensors is reduced by more than 70%, significantly reducing system cost, size, and failure rate.

[0046] S7, Inverse Coordinate Transformation The final determined dq-axis current reconstructed value i gid_rec and i giq_rec By inverse transformation back to the three-phase stationary coordinate system, the final reconstructed three-phase AC current value i is obtained. gia_rec i gib_rec i gic_rec .

[0047] Through the above steps, this embodiment effectively solves the problem of the unobservable region in traditional current reconstruction methods. Since the dq-axis current is a DC current in steady state and changes slowly in transient state, the error introduced by the holding strategy in S6 is minimal, ensuring the continuity and accuracy of the reconstructed current throughout the entire operating range.

[0048] Figure 7 The simulation waveforms comparing the reconstructed current and reconstructed power obtained using the method of this embodiment with the measured values ​​are shown. As can be seen from the figures, the reconstructed values ​​and measured values ​​almost perfectly match, and the steady-state power control error is less than 1%, verifying the effectiveness of the method proposed in this embodiment. Wherein, i gia i is the measured current of phase A. gia _rec is the reconfiguration current of phase A; P g For the measured power, P g _ rec The reconfigured power is calculated using the reconfigured current. As shown in the figure, the reconfigured value almost perfectly matches the measured value, and the steady-state power control error is less than 1%, verifying the effectiveness of the method proposed in this embodiment.

[0049] This embodiment provides a grid-type converter current reconfiguration system based on a single DC bus current sensor to implement the above method. For example... Figure 2As shown, the system includes: a single DC bus current sensor, a single DC bus voltage sensor, two AC voltage sensors, a modulation and timing calculation module, a sampling control module, and a current reconstruction module. Their connections are as follows: Figure 2 The area within the dashed box and the controller section are shown.

[0050] The data acquisition module includes a modulation and time calculation module. Its input receives the d-axis and q-axis reference voltages output from the voltage controller, and its output is connected to a PWM generator. This module generates a three-phase modulation signal and calculates the effective voltage vector action time T according to formulas (3) and (4). eff1 and T eff2 .

[0051] The sampling module includes a sampling control module, whose input is connected to the modulation and timing calculation module, and whose output is connected to the DC bus current sensor. This module receives T... eff1 and T eff2 and the preset minimum sampling time T min A comparison is made to precisely control the sampling timing of the current sensor. The reconstruction module includes a current reconstruction module, whose input is connected to the DC bus current sensor and the sampling control module, and whose output is connected to the power calculation unit of the converter. This module is used to execute S3 to S8 as described in Embodiment 1, processing the sampled DC bus current signal into accurate three-phase AC current reconstruction values.

[0052] Through the coordinated operation of the above modules, this system can obtain key current information that traditional solutions require 14 sensors using only 4 sensors (1 DC current, 1 DC voltage, and 2 AC voltages). The number of sensors is reduced by more than 70%, which significantly reduces the hardware cost and failure risk of the system.

[0053] Compared with the prior art, the present invention has the following advantages: First, the number of sensors is significantly reduced. This invention requires only a single DC bus current sensor to achieve three-phase current reconstruction. Combined with a single DC bus voltage sensor and two AC voltage sensors, the total number of sensors is only four, a reduction of over 70% compared to the approximately 14 sensors in traditional grid-type converters. This significantly reduces system hardware costs, size, and failure rate. Second, it solves the problem of current reconstruction distortion in unobservable regions. This invention identifies intervals where the effective voltage vector's action time is too short and maintains the previous cycle's current reconstruction value in the dq coordinate system within these intervals, avoiding reconstruction errors caused by missing sampling and achieving continuous and accurate reconstruction across the entire operating range. Third, it achieves high reconstruction accuracy. Since the current in the dq coordinate system is DC in steady state and changes slowly in transient state, the error introduced by the holding strategy employed in this invention is minimal. Experimental results show that the steady-state power control error is less than 1%, comparable to the accuracy of traditional schemes using all sensors. Fourth, it is simple to implement. This invention does not require complex observers or estimation algorithms; it only requires adding comparison judgment and register hold logic, making it easy to implement in existing controllers and lowering the barrier to engineering applications.

[0054] Based on the same inventive concept, this invention also provides a grid-type converter current reconstruction system with a single current sensor, comprising: The data acquisition module is used to acquire the DC bus current signal of the target grid converter in real time using a single current sensor, and to obtain the three-phase modulation signal of the target grid converter.

[0055] The sampling module is used to calculate the duration of each of the two effective voltage vectors in the current switching cycle based on the three-phase modulation signal, and denoted as the first duration and the second duration, respectively; determine the sampleable time of the DC bus current signal based on the first duration and the second duration; sample the DC bus current signal based on the sampleable time to obtain multiple instantaneous values ​​of DC bus current and the switching state corresponding to each sampling time.

[0056] The reconstruction module is used to reconstruct the instantaneous values ​​of the three-phase AC current based on multiple instantaneous values ​​of DC bus current and the corresponding switch states at each sampling time, to obtain temporary three-phase currents; transform the temporary three-phase currents to the synchronously rotating dq0 coordinate system to obtain temporary d-axis current components and temporary q-axis current components; if either the first action time or the second action time in the current switching cycle is less than the preset minimum sampling time, the d-axis current component and q-axis current component values ​​of the previous switching cycle are kept unchanged; otherwise, the temporary d-axis current component and temporary q-axis current component of the current switching cycle are used as the updated d-axis current component and q-axis current component values ​​for this cycle; the updated d-axis current component and q-axis current component values ​​are inversely transformed back to the three-phase stationary coordinate system to obtain the final reconstructed three-phase AC current values.

[0057] This invention also provides a computer device. At the hardware level, the computer device includes a processor, an internal bus, a network interface, memory, and non-volatile memory, and may also include other hardware required for business operations. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to implement the above-mentioned single-current sensor network converter current reconstruction method.

[0058] The present invention also provides a computer-readable storage medium storing a computer program that can be used to execute the above-described single-current sensor grid converter current reconstruction method.

[0059] Specific limitations on the calculation system for the single-current sensor-based grid-type converter current reconstruction method can be found in the limitations outlined above, and will not be repeated here. Each module in the aforementioned single-current sensor-based grid-type converter current reconstruction system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independent of the processor in a computer device, or stored in software within the computer device's memory, allowing the processor to call and execute the corresponding operations of each module.

[0060] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. Furthermore, the above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A current reconstruction method for a grid-type converter with a single current sensor, characterized in that, Includes the following steps: The DC bus current signal of the target grid converter is acquired in real time by a single current sensor, and the three-phase modulation signal of the target grid converter is obtained. The effective time of each of the two effective voltage vectors in the current switching cycle is calculated based on the three-phase modulation signal and recorded as the first effective time and the second effective time, respectively. The sampleable time of the DC bus current signal is determined based on the first effective time and the second effective time. The DC bus current signal is sampled based on the sampleable time to obtain multiple instantaneous values ​​of DC bus current and the switching state corresponding to each sampling time. The instantaneous values ​​of the three-phase AC current are reconstructed based on multiple instantaneous values ​​of DC bus current and the corresponding switch states at each sampling time to obtain temporary three-phase current. The temporary three-phase current is transformed to the synchronously rotating dq0 coordinate system to obtain temporary d-axis current components and temporary q-axis current components. If either the first action time or the second action time in the current switching cycle is less than the preset minimum sampling time, the values ​​of the d-axis current components and q-axis current components of the previous switching cycle are kept unchanged. Otherwise, the temporary d-axis current components and temporary q-axis current components of the current switching cycle are used as the updated values ​​of the d-axis current components and q-axis current components of this cycle. The updated d-axis and q-axis current component values ​​are inversely transformed back to the three-phase stationary coordinate system to obtain the final reconstructed three-phase AC current values.

2. The current reconstruction method for a grid-type converter with a single current sensor according to claim 1, characterized in that, The preset minimum sampling time is obtained by adding the dead time, the current settling time, and the analog-to-digital conversion time. The dead time is the delay time set to prevent the power switch from shooting through, the current settling time is the time required for the DC bus current to reach stability after the switch is activated, and the analog-to-digital conversion time is the time required to convert the sampled analog current signal into a digital quantity.

3. The current reconstruction method for a grid-type converter with a single current sensor according to claim 1, characterized in that, The first action time is obtained by multiplying the switching period by the difference between the median value and the minimum value of the three-phase modulation signal, and then dividing by two; the second action time is obtained by multiplying the switching period by the difference between the maximum value and the median value of the three-phase modulation signal, and then dividing by two.

4. The current reconstruction method for a grid-type converter with a single current sensor according to claim 1, characterized in that, The temporary three-phase current is transformed into a synchronously rotating dq0 coordinate system using a phase angle, which is provided by the power controller of the grid converter.

5. The current reconstruction method for a grid-type converter with a single current sensor according to claim 1, characterized in that, The method for determining the sampleable time includes: determining four sampling times within one switching cycle based on the first action time and the second action time, wherein two sampling times correspond to the middle region of the first action time and the other two sampling times correspond to the middle region of the second action time.

6. The current reconstruction method for a grid-type converter with a single current sensor according to claim 1, characterized in that, The process of reconstructing the instantaneous values ​​of the three-phase AC current based on multiple instantaneous values ​​of DC bus current and the corresponding switch states at each sampling time specifically includes: assigning the instantaneous values ​​of the DC bus current at each sampling time to the temporary current values ​​of the corresponding phases according to the correspondence table between switch states and three-phase AC currents, wherein when the switch state is that only one phase upper bridge arm is conducting, the DC bus current is equal to the current of that phase; when the switch state is that two phase upper bridge arms are conducting, the DC bus current is equal to the reverse value of the current of the unconducted phase.

7. The current reconstruction method for a grid-type converter with a single current sensor according to claim 1, characterized in that, In the process of keeping the d-axis current component and q-axis current component values ​​unchanged from the previous switching cycle, the d-axis current component and q-axis current component are DC quantities during steady-state operation, and their rate of change during transient operation is less than the set speed.

8. A current reconstruction system for a grid-type converter with a single current sensor, characterized in that, include: The data acquisition module is used to acquire the DC bus current signal of the target grid converter in real time using a single current sensor, and to obtain the three-phase modulation signal of the target grid converter; The sampling module is used to calculate the duration of each of the two effective voltage vectors in the current switching cycle based on the three-phase modulation signal, and denoted as the first duration and the second duration, respectively; determine the sampleable time of the DC bus current signal based on the first duration and the second duration; sample the DC bus current signal based on the sampleable time to obtain multiple instantaneous values ​​of DC bus current and the switching state corresponding to each sampling time; The reconstruction module is used to reconstruct the instantaneous values ​​of the three-phase AC current based on multiple instantaneous values ​​of DC bus current and the corresponding switch states at each sampling time, to obtain temporary three-phase currents; transform the temporary three-phase currents to the synchronously rotating dq0 coordinate system to obtain temporary d-axis current components and temporary q-axis current components; if either the first action time or the second action time in the current switching cycle is less than the preset minimum sampling time, the d-axis current component and q-axis current component values ​​of the previous switching cycle are kept unchanged; otherwise, the temporary d-axis current component and temporary q-axis current component of the current switching cycle are used as the updated d-axis current component and q-axis current component values ​​for this cycle; the updated d-axis current component and q-axis current component values ​​are inversely transformed back to the three-phase stationary coordinate system to obtain the final reconstructed three-phase AC current values.

9. A computer device, comprising a memory, a processor, and a computer program stored in the memory, characterized in that, The processor executes the computer program to implement the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is loaded by the processor, it is able to perform the steps of the method according to any one of claims 1 to 7.

Images