A control method of a converter and related apparatus

Abstract

This application discloses a control method and related apparatus for a converter, relating to the field of power electronics technology. The method includes: acquiring a voltage loop control signal and a current loop control signal, and determining a limiting coefficient based on the voltage loop control signal; wherein the limiting coefficient is a coefficient that varies with the voltage loop control signal; using the limiting coefficient to limit the current loop control signal to obtain a modulation signal; obtaining a pulse width modulation signal based on the modulation signal, and controlling the switching state of the converter's switching transistors based on the pulse width modulation signal. This application effectively avoids the phenomenon of the current loop control signal going out of control and exceeding the safety boundary under certain specific operating conditions, thus solving the problems of poor total harmonic distortion (THD) index of the AC input current at the converter input terminal and the easy occurrence of overvoltage on the DC bus at the output terminal.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method and related apparatus for a converter. Background Technology

[0002] With the rapid development of power electronics technology, converters, as the core topology for AC-to-DC high-frequency power conversion, are widely used in industrial power supplies, new energy power generation, and electric vehicle charging facilities. To stabilize the DC voltage output and AC input current, converters typically employ a dual closed-loop control architecture with a bus voltage loop and an input current loop, combined with pulse width modulation (PWM) technology to drive the converter's switching transistors. The bus voltage loop calculates the bus voltage signal and outputs a voltage loop control signal. The input current loop calculates the voltage loop control signal and outputs a current loop control signal. In traditional control schemes, the current loop control signal is typically converted by a modulation module to obtain a PWM signal, which is then used to drive the AC-side switching transistors at high frequency to achieve power rectification and boost conversion.

[0003] However, in certain specific operating conditions (e.g., when the converter is under light load), the current loop control signal of the existing dual closed-loop control architecture is prone to runaway and over-adjustment, which in turn leads to poor total harmonic distortion of the AC input current at the input end of the converter and technical problems such as overvoltage at the DC bus at the output end. Summary of the Invention

[0004] In view of the above problems, this application provides a control method and related apparatus for a converter to effectively prevent the current loop control signal from going out of control and exceeding the safety boundary under certain operating conditions, thus solving the problems of poor total harmonic distortion of the AC input current at the converter input terminal and the DC bus at the output terminal being prone to overvoltage. The specific solution is as follows:

[0005] The first aspect of this application provides a control method for a converter, comprising:

[0006] The voltage loop control signal and the current loop control signal are acquired, and the limiting coefficient is determined based on the voltage loop control signal; wherein the limiting coefficient is a coefficient that varies with the voltage loop control signal.

[0007] The current loop control signal is limited according to the limiting coefficient to generate a modulation signal;

[0008] Based on the modulation signal, a pulse width modulation signal is obtained, and based on the pulse width modulation signal, the switching state of the switching transistor of the converter is controlled.

[0009] In one possible implementation, determining the limiting coefficient based on the voltage loop control signal includes:

[0010] Obtain the first preset coefficient and the second preset coefficient;

[0011] The voltage loop control signal and the first preset coefficient are multiplied to obtain the product result;

[0012] The limiting coefficient is determined based on the difference between the second preset coefficient and the product result;

[0013] Wherein, the first preset coefficient is used to control the slope of the limiting coefficient as it changes with the voltage loop control signal, and the second preset constant is used to set the upper limit boundary of the limiting coefficient.

[0014] In one possible implementation, the current loop control signal is limited according to the limiting coefficient to generate a modulated signal, including:

[0015] Obtain preset upper limit and preset lower limit values, and determine dynamic upper limit and dynamic lower limit values ​​based on the limiting coefficient, the preset upper limit and the preset lower limit values;

[0016] The current loop control signal is compared with the dynamic upper limit value and the dynamic lower limit value respectively;

[0017] If the current loop control signal is greater than the dynamic upper limit value, then the dynamic upper limit value is determined as the modulation signal;

[0018] If the current loop control signal is less than the dynamic lower limit value, then the dynamic lower limit value is determined as the modulation signal;

[0019] If the current loop control signal is between the dynamic upper limit value and the dynamic lower limit value, then the current loop control signal is determined as the modulation signal.

[0020] In one possible implementation, obtaining the voltage loop control signal includes:

[0021] The positive bus voltage signal and the negative bus voltage signal at the DC output terminal of the converter are acquired, and the bus voltage signal is obtained based on the positive bus voltage signal and the negative bus voltage signal.

[0022] The bus voltage signal is subjected to low-pass filtering to obtain the filtered bus voltage signal;

[0023] The bus voltage error signal is determined based on the difference between the preset target bus voltage and the filtered bus voltage signal.

[0024] The bus voltage error signal is input to the voltage loop controller, and the voltage loop controller outputs the voltage loop control signal.

[0025] In one possible implementation, obtaining the current loop control signal includes:

[0026] Acquire the AC input voltage signal and AC input current signal of the converter;

[0027] Based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal, the initial phase of the AC input voltage signal is corrected to obtain the voltage phase signal;

[0028] The voltage phase signal and the voltage loop control signal are input to the current loop controller, and the current loop controller outputs the current loop control signal.

[0029] In one possible implementation, the initial phase of the AC input voltage signal is corrected based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal to obtain a voltage phase signal, including:

[0030] Obtain the current fundamental frequency of the power grid and perform phase-locked loop processing on the AC input voltage signal to obtain the power grid phase angle;

[0031] The zero-crossing times of the AC input voltage signal and the AC input current signal are detected in the same period, and the zero-crossing time difference between the zero-crossing times of the AC input voltage signal and the AC input current signal is calculated.

[0032] Based on the zero-crossing time difference and the current grid fundamental frequency, the target compensation angle is determined, and the grid phase angle is corrected using the target compensation angle to obtain the voltage phase signal.

[0033] In one possible implementation, determining the target compensation angle based on the zero-crossing time difference and the current grid fundamental frequency includes:

[0034] The initial compensation angle is determined based on the zero-crossing time difference and the current fundamental frequency of the power grid;

[0035] The initial compensation angle is compared with the preset dead zone threshold;

[0036] If the initial compensation angle is greater than the dead zone threshold, then the initial compensation angle is subjected to first-order hysteresis filtering, and the filtered initial compensation angle is determined as the target compensation angle.

[0037] If the initial compensation angle is less than or equal to the dead zone threshold, then the target compensation angle is set to zero.

[0038] In one possible implementation, obtaining the current grid fundamental frequency includes:

[0039] The current fundamental frequency of the power grid is obtained in real time using a phase-locked loop module; or

[0040] The zero-crossing period is calculated based on the zero-crossing time of the AC input voltage signal, and the current grid fundamental frequency is determined based on the zero-crossing period.

[0041] A second aspect of this application provides a control device for a converter, comprising:

[0042] An acquisition module is used to acquire voltage loop control signals and current loop control signals, and determine a limiting coefficient based on the voltage loop control signals; wherein the limiting coefficient is a coefficient that varies with the voltage loop control signals;

[0043] A limiting module is used to limit the current loop control signal according to the limiting coefficient to generate a modulated signal;

[0044] The control module is used to obtain a pulse width modulation signal based on the modulation signal, and to control the switching state of the switching transistors of the converter based on the pulse width modulation signal.

[0045] The third aspect of this application provides an uninterruptible power supply and a control method for a converter configured to perform the first aspect or any implementation thereof.

[0046] A fourth aspect of this application provides a computer program product including computer-readable instructions that, when executed on an electronic device, cause the electronic device to implement the control method of the converter described in the first aspect or any implementation thereof.

[0047] A fifth aspect of this application provides an electronic device, comprising at least one processor and a memory connected to the processor, wherein:

[0048] The memory is used to store computer programs;

[0049] The processor is used to execute the computer program so that the electronic device can implement the control method of the converter of the first aspect or any implementation thereof.

[0050] The sixth aspect of this application provides a computer storage medium carrying one or more computer programs, which, when executed by an electronic device, enable the electronic device to control the converter of the first aspect or any implementation thereof.

[0051] The present application provides a converter control method based on the above technical solution. First, it acquires the voltage loop control signal and the current loop control signal, and dynamically calculates a limiting coefficient that changes with the voltage loop control signal based on the current voltage loop control signal. Next, it uses this limiting coefficient to limit the current loop control signal and outputs a modulation signal. Finally, it generates a pulse width modulation signal based on the modulation signal to control the switching state of the switching transistors in the converter. Based on the mechanism of boundary constraint of the current loop control signal by the voltage loop control signal (i.e., guiding the control logic of the input current loop through the bus voltage loop), under certain specific operating conditions of the converter (light load condition or operation in a low input voltage range, etc.), the value of the voltage loop control signal decreases accordingly, thereby driving the limiting coefficient to decrease synchronously. At this time, under such specific operating conditions, the converter may experience sudden amplitude changes or spikes in the current loop control signal due to nonlinear interference. Since the limiting coefficient has been dynamically reduced, the current loop control signal is clamped within the boundary established by the limiting coefficient. This effectively avoids the phenomenon of over-adjustment caused by the current loop control signal losing control under this specific operating condition, thereby solving the problems of poor total harmonic distortion index of AC input current at the input end and the easy occurrence of voltage overshoot on DC bus at the output end. Attached Figure Description

[0052] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0053] Figure 1 A flowchart illustrating a control method for a converter provided in this application;

[0054] Figure 2 A schematic diagram of the structure of a converter provided in this application;

[0055] Figure 3 A schematic diagram of another converter provided in this application;

[0056] Figure 4 This is a schematic diagram of the structure of a control device for a converter provided in an embodiment of this application;

[0057] Figure 5 This is a schematic diagram of the structure of a computer device provided in an embodiment of this application. Detailed Implementation

[0058] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.

[0059] The embodiments of this application will now be described with reference to the accompanying drawings. Those skilled in the art will recognize that, with technological advancements and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are equally applicable to similar technical problems.

[0060] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.

[0061] First, a definition of the terminology used in this application is provided:

[0062] UPS (Uninterruptible Power Supply): A power protection device that uses a converter as a front-end hub to convert AC power into DC power, and works in conjunction with energy storage units, inverter circuits, and bypass circuits. When the grid is normal, the converter supports the DC bus to achieve inverter-regulated output and energy storage charging. In case of grid anomalies, it instantly switches to the energy storage unit to supply power to the DC bus, which is then output via inverter, thus ensuring an absolutely safe and uninterrupted power supply to downstream load devices.

[0063] Rectifier: A power electronic conversion circuit that uses the unidirectional conductivity of power electronic switching devices (such as diodes, thyristors, or high-power switching transistors) to convert alternating current energy with alternating direction into unidirectional pulsating or steady direct current energy.

[0064] Bus voltage loop: The outer voltage loop in the dual closed-loop control architecture, which aims to build a full-process closed-loop control architecture covering DC bus voltage signal sampling, differential comparison with a given reference, outer loop adjustment calculation, and control command output.

[0065] Voltage loop controller: The core computing entity nested within the bus voltage loop architecture, used to carry and execute specific outer loop regulation algorithms (such as PI regulators and PR regulators) to drive the bus voltage loop to achieve the DC voltage regulation target.

[0066] Input current loop: The inner current loop in the dual closed-loop control architecture, designed to construct a full-process closed-loop control architecture covering AC input current signal sampling, command reference error calculation, inner loop adjustment calculation, and final control parameter output.

[0067] Current loop controller: The core computing entity nested within the input current loop architecture, used to carry and execute specific inner loop waveform following algorithms (such as PI regulators, PR regulators, etc.), driving the input current loop to achieve high-frequency dynamic adjustment and error convergence.

[0068] A PI controller (Proportional-Integral Controller) is a closed-loop feedback controller in an automatic control system. It calculates the error between the setpoint and the actual feedback value, and uses both proportional (P) and integral (I) mathematical formulas to output a control quantity, thereby stabilizing the system in the desired state.

[0069] Secondly, to facilitate understanding of the technical solutions provided in the embodiments of this application by those skilled in the art, the relevant technologies are described below: The inventors have discovered that in UPS equipment, the converter typically employs a dual closed-loop control architecture for control. However, under this dual closed-loop control architecture, when the converter is under certain specific operating conditions (zero-crossing region), due to the inherent characteristics of the converter and the nonlinearity of the system, the current loop control signal is prone to malfunction and over-adjustment, resulting in a significant phase difference between the AC input voltage and the AC input current. This phase difference also shifts to varying degrees with changes in the load rate, leading to poor total harmonic distortion (THD) performance of the AC input current at the converter's input terminal and a high risk of overvoltage on the DC bus at the output terminal.

[0070] To address the aforementioned problems, this application provides a converter control method. The converter control method of this application embodiment will be described in detail below with reference to the accompanying drawings.

[0071] Reference Figure 1 , Figure 1 A flowchart illustrating a converter control method provided in an embodiment of this application is shown below. Figure 1 As shown, the converter control method provided in this application embodiment may include steps 101 to 103, which are described in detail below.

[0072] 101. Obtain the voltage loop control signal and the current loop control signal, and determine the limiting coefficient based on the voltage loop control signal. The limiting coefficient is a coefficient that varies with the voltage loop control signal.

[0073] Specifically, the voltage loop control signal is the control command output by the bus voltage loop during the operation of the outer voltage loop control algorithm, based on the DC voltage regulation requirements, to reflect the converter's current total input power demand. The current loop control signal is the control command output by the input current loop during the operation of the inner current loop control algorithm, after adjusting the aforementioned total demand based on waveform following requirements. The converter may include a rectifier, inverter, DC-DC converter, AC-DC converter, etc. Taking a rectifier as an example, the rectifier may be a single-phase Vienna rectifier topology circuit, a full-bridge pulse width modulation rectifier topology circuit, or a three-phase half-bridge pulse width modulation rectifier topology circuit, etc. In this embodiment, the bus voltage loop can be used as the outer voltage loop, and the input current loop can be used as the inner current loop. (Reference) Figure 2 First, the voltage loop control signal can be acquired, and then the limiting coefficient can be determined based on it. The limiting coefficient can refer to the numerical boundary used to constrain the current loop control signal, preventing it from going out of control under specific operating conditions. The limiting coefficient can also be a coefficient that varies with the voltage loop control signal. Specifically, when the load increases, causing the voltage loop control signal to increase, the limiting coefficient is increased accordingly, thereby widening the limiting range of the current loop control signal to ensure the circuit's dynamic response performance and power transmission capability. Conversely, when the load decreases, causing the voltage loop control signal to decrease, the limiting coefficient is decreased accordingly, thereby tightening the limiting range of the current loop control signal to prevent signal distortion due to over-modulation or entering the nonlinear operating region. In other words, the limiting coefficient corresponding to the converter under heavy load conditions is greater than that under light load conditions. How to determine the limiting coefficient will be described in the following embodiments and will not be repeated here.

[0074] In practical applications, the controller can acquire the voltage loop control signal through various methods, including hardware closed-loop sampling calculation, external host computer command reception, and internal state observer estimation. The following provides an example of a scheme for acquiring the voltage loop control signal based on hardware closed-loop sampling.

[0075] To further improve the control accuracy and anti-interference capability of the voltage loop control signal, refer to Figure 3 In one possible implementation, step 101 may include: acquiring the positive and negative bus voltage signals at the DC output of the converter, and obtaining a bus voltage signal based on the positive and negative bus voltage signals; performing low-pass filtering on the bus voltage signal to obtain a filtered bus voltage signal; determining a bus voltage error signal based on the difference between a preset target bus voltage and the filtered bus voltage signal; and inputting the bus voltage error signal to a voltage loop controller, which then outputs a voltage loop control signal.

[0076] Specifically, the switching transistors used to construct this converter can be insulated-gate bipolar transistors (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), and silicon carbide power devices, etc. The controller can acquire the positive bus voltage signal (corresponding to) in the DC bus at the converter output terminal through non-isolated voltage divider sampling or isolated sensor sampling. Figure 3 Ubus_P sampling in the middle) and negative bus voltage signal (corresponding to Figure 3 (Ubus_N sampling in the converter). Non-isolated voltage divider sampling refers to connecting a resistor divider network to the DC bus at the converter output. The resistor divider network outputs a low-voltage analog signal proportionally. The analog-to-digital converter channel inside the controller reads this low-voltage analog signal as the positive and negative bus voltage signals. Isolated sensor sampling refers to connecting an external Hall voltage sensor or optocoupler-isolated operational amplifier to the DC bus at the converter output. The Hall voltage sensor or optocoupler-isolated operational amplifier extracts the positive and negative bus voltage signals and converts them into corresponding electrically isolated signals input to the controller, thereby effectively preventing electromagnetic interference from the converter to the controller.

[0077] Then, based on the positive and negative bus voltage signals, the bus voltage signal is obtained. Due to the inherent characteristics of the converter, high-frequency glitches and low-frequency voltage ripples generated by the switching frequency may be superimposed on the DC bus. Therefore, the bus voltage signal (corresponding to...) can be... Figure 3 The Ubus_sum_lpf1 in the middle is subjected to low-pass filtering (corresponding to Figure 3The controller can use digital filtering algorithms or hardware filtering networks to perform low-pass filtering on the bus voltage signal. Digital filtering algorithms can refer to the controller internally executing a first-order inertial low-pass filtering algorithm or a moving average filtering algorithm. The controller uses digital filtering algorithms to filter out high-frequency switching glitches and low-frequency ripples superimposed on the bus voltage signal, thereby outputting a filtered bus voltage signal. Hardware filtering networks refer to the bus voltage signal undergoing hardware smoothing through an external RC filter circuit before entering the controller for control logic operations, thus obtaining a filtered bus voltage signal. Then, the preset target bus voltage is subtracted from the filtered bus voltage signal to determine the bus voltage error signal. The bus voltage error signal is then input to the voltage loop controller, which outputs the voltage loop control signal. The preset target bus voltage can refer to a static voltage reference value fixed within the controller, or a DC voltage expectation value dynamically generated and issued based on the current operating conditions, load status, or peripheral commands, used as the closed-loop adjustment target for the bus voltage loop. In some embodiments, to effectively prevent integral saturation of the converter during startup or sudden load changes, the voltage loop controller may employ a proportional-integral algorithm with anti-integral saturation functionality. In some embodiments, when the calculated output value of the voltage loop controller exceeds a preset threshold, the voltage loop controller can be shut down, thereby effectively preventing overshoot oscillations in the voltage loop control signal and further ensuring the operational stability of the converter.

[0078] In this embodiment, the bus voltage signal is determined based on the positive and negative bus voltage signals. After performing low-pass filtering on the signal, the bus voltage error signal is calculated by combining it with the preset target bus voltage. Then, the voltage loop controller is driven to output the voltage loop control signal according to the bus voltage error signal, thereby effectively avoiding high-frequency jitter or waveform disorder in the voltage loop control signal and helping to maintain the dynamic balance of the converter output power.

[0079] The above describes how to obtain the voltage loop control signal. The following will describe in detail the specific operation process of obtaining the current loop control signal.

[0080] In one possible implementation, step 101 may include: acquiring the AC input voltage signal and AC input current signal of the converter; correcting the initial phase of the AC input voltage signal based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal to obtain a voltage phase signal; inputting the voltage phase signal and the voltage loop control signal to the current loop controller, and outputting the current loop control signal through the current loop controller.

[0081] Specifically, the AC input voltage signal can be extracted using an AC voltage transformer or a voltage divider network. The AC input current signal can be extracted using a Hall current sensor or a high-frequency shunt resistor. Taking the extraction of the AC input current signal using a Hall current sensor as an example, the Hall current sensor converts the large current on the input side of the converter into a low voltage level, and the analog-to-digital conversion module inside the controller then reads this low voltage level to obtain the AC input current signal.

[0082] Due to the inherent delay of the filter inductor and sampling capacitor within the converter, the AC input current signal often lags behind or leads the AC input voltage signal in time. Therefore, the phase shift caused by this inherent delay can be dynamically compensated by calculating the zero-crossing time difference between the AC input voltage and current signals. Specifically, the initial phase of the AC input voltage signal can be corrected based on the zero-crossing time difference to generate a voltage phase signal. After generating the voltage phase signal, the voltage phase signal and the voltage loop control signal are input to the current loop controller. In the internal control logic of the current loop controller, the voltage phase signal provides a phase reference for a standard sine wave, and the voltage loop control signal provides an amplitude reference for this standard sine wave. A target current reference command is generated using the voltage loop control signal and the voltage phase signal, and closed-loop error adjustment is performed in conjunction with the actual AC input current signal. Finally, the current loop controller outputs a current loop control signal.

[0083] In this embodiment, after obtaining the voltage phase signal through the zero-crossing time difference, the voltage phase signal is injected into the current loop control signal as a feedforward current loop controller, thereby realizing phase synchronization between AC input voltage and AC input current.

[0084] In practical applications, controllers can employ various methods to compensate for the initial phase of the AC input voltage signal to offset phase shifts caused by inherent delays. For example, the controller can compensate for the initial phase of the AC input voltage signal using a fixed angle. It can also compensate for the initial phase based on the zero-crossing time difference. Alternatively, it can perform address comparisons in a preset mapping table based on the real-time load rate, and smooth non-node data using interpolation algorithms (such as linear interpolation) to calculate the compensation parameters for the initial phase. To achieve high-precision dynamic compensation for phase drift under different operating conditions, a scheme for compensating the initial phase based on the zero-crossing time difference is provided below as an example.

[0085] In one possible implementation, the initial phase of the AC input voltage signal is corrected based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal to obtain a voltage phase signal. This includes: acquiring the current grid fundamental frequency and performing phase-locked loop processing on the AC input voltage signal to obtain the grid phase angle; detecting the zero-crossing times of the AC input voltage signal and the AC input current signal within the same period, and calculating the zero-crossing time difference between the zero-crossing times of the AC input voltage signal and the AC input current signal; determining a target compensation angle based on the zero-crossing time difference and the current grid fundamental frequency, and using the target compensation angle to correct the grid phase angle to obtain the voltage phase signal.

[0086] Specifically, the AC input voltage signal can be tracked using digital algorithms to extract the current grid fundamental frequency and grid phase angle. During zero-crossing detection, the moment when the AC input voltage signal changes from negative to positive or from positive to negative is extracted as the zero-crossing moment of the AC input voltage signal; similarly, the moment when the AC input current signal changes from negative to positive or from positive to negative is extracted as the zero-crossing moment of the AC input current signal. The zero-crossing moments of the AC input voltage signal and the AC input current signal are subtracted to obtain the zero-crossing time difference. Subsequently, this zero-crossing time difference is multiplied by the current grid fundamental frequency to obtain the target compensation angle. The formula for calculating the target compensation angle can be:

[0087] Δθ=2π*f_grid*Δt

[0088] In the above formula, Δθ represents the target compensation angle, f_grid represents the current grid fundamental frequency, and Δt represents the zero-crossing time difference. The value of the target compensation angle is superimposed on the value of the grid phase angle to correct the grid phase angle, thereby outputting the voltage phase signal.

[0089] In this embodiment, the target compensation angle is determined by the current grid fundamental frequency and the zero-crossing time difference of the AC input voltage signal and the AC input current signal to correct the grid phase angle, thereby achieving phase synchronization between the AC input voltage and the AC input current, which significantly improves the power factor of the converter and reduces losses.

[0090] There are several ways to obtain the current fundamental frequency of the power grid. For example, the controller can extract the current fundamental frequency of the power grid using the Discrete Fourier Transform algorithm, or calculate the current fundamental frequency of the power grid using the zero-crossing time interval. The following provides an example scheme for obtaining the current fundamental frequency of the power grid.

[0091] In some possible implementations, obtaining the current grid fundamental frequency includes: using a phase-locked loop module to obtain the current grid fundamental frequency in real time; or calculating the voltage zero-crossing period based on the zero-crossing time of the AC input voltage signal, and determining the current grid fundamental frequency based on the voltage zero-crossing period.

[0092] Specifically, refer to Figure 3 The phase-locked loop (PLL) module (e.g., SOGI) built into the controller can be used to lock the phase and frequency of the current AC input signal of the power grid, thereby obtaining the current fundamental frequency of the power grid. It can also record the times when two adjacent AC input voltage signals cross the zero-level line. Then, the time difference between two adjacent times is used as the voltage zero-crossing period. Taking the reciprocal of this voltage zero-crossing period yields the current fundamental frequency of the power grid.

[0093] In this embodiment, the current fundamental frequency of the power grid is obtained by real-time extraction through a phase-locked loop or by calculating the voltage zero-crossing period. This allows for flexible adaptation to different computing resource configurations and maintains continuous phase synchronization between the control logic and the power grid.

[0094] The above describes the specific implementation method for obtaining the current grid fundamental frequency. After obtaining the current grid fundamental frequency, there are various ways to determine the target compensation angle based on the zero-crossing time difference and the current grid fundamental frequency. For example, the converter's control logic can use a fixed angle as the target compensation angle. Alternatively, a lookup table can be used to obtain the target compensation angle. Another method is to calculate the target compensation angle based on the zero-crossing time difference. The following provides an example scheme for determining the target compensation angle.

[0095] In one possible implementation, determining the target compensation angle based on the zero-crossing time difference and the current grid fundamental frequency includes: determining an initial compensation angle based on the zero-crossing time difference and the current grid fundamental frequency; comparing the initial compensation angle with a preset dead-zone threshold; if the initial compensation angle is greater than the dead-zone threshold, performing a first-order lag filtering on the initial compensation angle, and determining the filtered initial compensation angle as the target compensation angle; if the initial compensation angle is less than or equal to the dead-zone threshold, assigning the target compensation angle a value of zero.

[0096] Specifically, the dead zone threshold can refer to the angular value boundary pre-stored in the controller's storage medium. The initial compensation angle is obtained by multiplying the zero-crossing time difference by the current grid fundamental frequency. Subsequently, the initial compensation angle is compared with the dead zone threshold. If the initial compensation angle is less than or equal to the dead zone threshold, the target compensation angle is set to zero, meaning no angle compensation is applied to the grid phase angle. If the initial compensation angle is greater than the dead zone threshold, a first-order hysteresis filtering algorithm is used to filter the initial compensation angle, and the output value of the first-order hysteresis filtering algorithm is determined as the target compensation angle.

[0097] In this embodiment, the initial compensation angle is calculated based on the zero-crossing time difference and the current grid fundamental frequency. The target compensation angle is established by introducing a dead zone threshold judgment and a first-order hysteresis filtering mechanism. This effectively shields small error disturbances while achieving a smooth transition of the compensation action.

[0098] The above describes the processing steps for obtaining the voltage loop control signal and the current loop control signal. After obtaining the voltage loop control signal, the limiting coefficient is determined based on the voltage loop control signal. The limiting coefficient is used to perform limiting processing on the current loop control signal when the value of the current loop control signal exceeds the constraint boundary. There are multiple ways to determine the limiting coefficient based on the voltage loop control signal. For example, (1) The controller has a pre-stored association mapping table, which records the correspondence between the voltage loop control signal value and the limiting coefficient. The controller compares the current voltage loop control signal value and searches for and extracts the corresponding limiting coefficient in the association mapping table. (2) The controller has a preset mathematical conversion function. The controller uses the current voltage loop control signal value as the input independent variable to perform mathematical operations, and outputs the corresponding limiting coefficient based on the result of the mathematical operations. (3) The controller has preset multiple value intervals. The controller determines the specific value interval into which the current voltage loop control signal value falls, and extracts the preset limiting coefficient based on the specific value interval into which it falls. The following provides an example implementation of obtaining the limiting coefficient.

[0099] In one possible implementation, step 101 may include: obtaining a first preset coefficient and a second preset coefficient; multiplying the voltage loop control signal and the first preset coefficient to obtain a product; and determining the limiting coefficient based on the difference between the second preset coefficient and the product. The first preset coefficient is used to control the slope of the limiting coefficient as it changes with the voltage loop control signal, and the second preset constant is used to set the upper limit boundary of the limiting coefficient.

[0100] Specifically, the first and second preset constants can be fixed parameters calibrated within the controller by technicians after synthesizing the theoretical model of the converter and repeatedly conducting dynamic response tests and fitting optimizations under actual multi-step load conditions. For example, the value range of the first preset constant can be [0.01, 0.03]; the value range of the second preset constant can be [0.4, 0.7]. This application embodiment does not limit the value range of the first and second preset constants; those skilled in the art can make adaptive adjustments based on actual hardware parameters. It should be noted that, in conjunction with the appendix... Figure 3 The control logic shown has a first preset constant that corresponds specifically to the product of the effective value and the adjustment coefficient in the diagram; where the effective value is the sampled effective value of the AC input voltage signal. To reduce the dynamic computational load of the controller, the sampled effective value can be a preset fixed constant. The first preset constant is obtained by multiplying the sampled effective value and the adjustment coefficient numerically. Then, the limiting coefficient can be determined based on the first preset coefficient, the second preset coefficient, and the voltage loop control signal. The formula for calculating the limiting coefficient is as follows:

[0101] K = C2 - C1 × U loop

[0102] Where K is the limiting coefficient; C1 is the first preset constant; C2 is the second preset constant; U loop This is the voltage loop control signal. The limiting coefficient is used to dynamically limit the modulation amount of the converter in real time, so as to suppress the pulse output near the zero crossing point of the grid voltage under no-load or light-load conditions, thereby preventing DC bus voltage overshoot.

[0103] In this embodiment, a linear mapping operation is performed on the voltage loop control signal using a first preset constant and a second preset constant to establish the corresponding limiting coefficient, thereby realizing the dynamic adaptive adjustment of the limiting boundary.

[0104] 102. The current loop control signal is limited according to the limiting coefficient to generate a modulation signal.

[0105] Specifically, a limiting processing module can be configured within the control logic. The limiting coefficient can be input to this module, which then outputs a limited current loop control signal. A modulation signal is then generated based on this limited current loop control signal. There are several ways to generate the modulation signal. For example, the limited current loop control signal can be directly used as the modulation signal for subsequent pulse width modulation (PWM) signal generation. Alternatively, the current DC bus voltage value of the converter can be obtained, and the limited current loop control signal and this DC bus voltage value can be divided to obtain the modulation signal. Alternatively, the AC voltage feedforward value of the converter's AC side can be obtained, and the limited current loop control signal and this AC voltage feedforward value can be summed to obtain the modulation signal. Alternatively, a preset gain coefficient can be obtained, and the limited current loop control signal and this gain coefficient can be multiplied to obtain the modulation signal. The modulation signal in this application only represents the input control parameter used to participate in subsequent pulse width modulation. As for the specific data type, physical unit, per-unit form of the modulation signal, and the intermediate mathematical transformation process that the modulation signal undergoes to obtain the modulation signal, this application does not make specific limitations on these aspects.

[0106] The limiting module can limit the current loop control signal according to the limiting coefficient in various ways. For example, the controller can use a unidirectional truncation limiting method, an asymmetric bidirectional limiting method, or a symmetrical bidirectional limiting method. The following provides an example implementation of a symmetrical bidirectional limiting method.

[0107] In one possible implementation, step 102 may include: obtaining a preset upper limit value and a preset lower limit value, and determining a dynamic upper limit value and a dynamic lower limit value based on the limiting coefficient, the preset upper limit value, and the preset lower limit value. The current loop control signal is compared with the dynamic upper limit value and the dynamic lower limit value respectively. If the current loop control signal is greater than the dynamic upper limit value, the dynamic upper limit value is determined as the modulation signal. If the current loop control signal is less than the dynamic lower limit value, the dynamic lower limit value is determined as the modulation signal. If the current loop control signal is between the dynamic upper limit value and the dynamic lower limit value, the current loop control signal is determined as the modulation signal.

[0108] Specifically, preset upper and lower limits are obtained. Then, a dynamic upper limit is obtained by multiplying the limiting coefficient and the preset upper limit. Similarly, a dynamic lower limit is obtained by multiplying the limiting coefficient and the preset lower limit. The current loop control signal is compared with the dynamic upper and lower limits to determine the modulation signal. This modulation signal is a reference control quantity used to determine the duty cycle of the switching transistors in the converter. This modulation signal is provided as an input variable to the subsequent pulse width modulation generator (PWM generator) to establish the corresponding pulse modulation signal in the subsequent calculations.

[0109] In this embodiment, by clamping the current loop control signal within the boundary defined by the limiting coefficient and its opposite to output the modulation signal, the out-of-bounds saturation distortion of the control parameters is effectively suppressed, ensuring the safety of subsequent wave generation operations.

[0110] 103. Based on the modulation signal, a pulse width modulation signal is obtained, and based on the pulse width modulation signal, the switching state of the switching transistor of the converter is controlled.

[0111] Specifically, the modulated signal output after amplitude limiting is acquired, and pulse width modulation (PWM) transformation is performed based on the numerical characteristics of the modulated signal to generate a time-domain pulse sequence (PWM signal) containing the corresponding duty cycle. The hardware driver circuit receives the PWM signal and generates a corresponding drive pulse based on the level state of the PWM signal. The drive pulse is then applied to the control terminal of the switch inside the converter to change the on or off state of the switch, thereby shaping the waveform of the input current at the converter input terminal and performing closed-loop stabilization regulation on the output voltage at the converter output terminal to convert the AC power received at the input terminal into DC power for supplying the downstream DC load.

[0112] The above describes a converter control method provided by the embodiments of this application. The following describes the apparatus for implementing the converter control method described above.

[0113] Please see Figure 4 , Figure 4 This is a schematic diagram of the structure of a control device for a converter provided in an embodiment of this application. Figure 4 As shown, the control device 400 of the converter includes:

[0114] The acquisition module 401 is used to acquire the voltage loop control signal and the current loop control signal, and determine the limiting coefficient based on the voltage loop control signal; wherein the limiting coefficient is a coefficient that varies with the voltage loop control signal.

[0115] Limiting module 402 is used to limit the current loop control signal according to the limiting coefficient to generate a modulation signal;

[0116] The control module 403 is used to obtain a pulse width modulation signal based on the modulation signal, and to control the switching state of the switching transistor of the converter based on the pulse width modulation signal.

[0117] In one possible implementation, determining the limiting coefficient based on the voltage loop control signal includes:

[0118] Obtain the first preset coefficient and the second preset coefficient;

[0119] The voltage loop control signal and the first preset coefficient are multiplied to obtain the product result;

[0120] The limiting coefficient is determined based on the difference between the second preset coefficient and the product result;

[0121] Wherein, the first preset coefficient is used to control the slope of the limiting coefficient as it changes with the voltage loop control signal, and the second preset constant is used to set the upper limit boundary of the limiting coefficient.

[0122] In one possible implementation, the acquisition module 401 is specifically used for:

[0123] Obtain preset upper limit and preset lower limit values, and determine dynamic upper limit and dynamic lower limit values ​​based on the limiting coefficient, the preset upper limit and the preset lower limit values;

[0124] The current loop control signal is compared with the dynamic upper limit value and the dynamic lower limit value respectively;

[0125] If the current loop control signal is greater than the dynamic upper limit value, then the dynamic upper limit value is determined as the modulation signal;

[0126] If the current loop control signal is less than the dynamic lower limit value, then the dynamic lower limit value is determined as the modulation signal;

[0127] If the current loop control signal is between the dynamic upper limit value and the dynamic lower limit value, then the current loop control signal is determined as the modulation signal.

[0128] In one possible implementation, the acquisition module 401 is specifically used for:

[0129] The positive bus voltage signal and the negative bus voltage signal at the DC output terminal of the converter are acquired, and the bus voltage signal is obtained based on the positive bus voltage signal and the negative bus voltage signal.

[0130] The bus voltage signal is subjected to low-pass filtering to obtain the filtered bus voltage signal;

[0131] The bus voltage error signal is determined based on the difference between the preset target bus voltage and the filtered bus voltage signal.

[0132] The bus voltage error signal is input to the voltage loop controller, and the voltage loop controller outputs the voltage loop control signal.

[0133] In one possible implementation, the acquisition module 401 is specifically used for:

[0134] Acquire the AC input voltage signal and AC input current signal of the converter;

[0135] Based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal, the initial phase of the AC input voltage signal is corrected to obtain the voltage phase signal;

[0136] The voltage phase signal and the voltage loop control signal are input to the current loop controller, and the current loop controller outputs the current loop control signal.

[0137] In one possible implementation, the initial phase of the AC input voltage signal is corrected based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal to obtain a voltage phase signal, including:

[0138] Obtain the current fundamental frequency of the power grid and perform phase-locked loop processing on the AC input voltage signal to obtain the power grid phase angle;

[0139] The zero-crossing times of the AC input voltage signal and the AC input current signal are detected in the same period, and the zero-crossing time difference between the zero-crossing times of the AC input voltage signal and the AC input current signal is calculated.

[0140] Based on the zero-crossing time difference and the current grid fundamental frequency, the target compensation angle is determined, and the grid phase angle is corrected using the target compensation angle to obtain the voltage phase signal.

[0141] In one possible implementation, determining the target compensation angle based on the zero-crossing time difference and the current grid fundamental frequency includes:

[0142] The initial compensation angle is determined based on the zero-crossing time difference and the current fundamental frequency of the power grid;

[0143] The initial compensation angle is compared with the preset dead zone threshold;

[0144] If the initial compensation angle is greater than the dead zone threshold, then the initial compensation angle is subjected to first-order hysteresis filtering, and the filtered initial compensation angle is determined as the target compensation angle.

[0145] If the initial compensation angle is less than or equal to the dead zone threshold, then the target compensation angle is set to zero.

[0146] In one possible implementation, obtaining the current grid fundamental frequency includes:

[0147] The current fundamental frequency of the power grid is obtained in real time using a phase-locked loop module; or

[0148] The zero-crossing period is calculated based on the zero-crossing time of the AC input voltage signal, and the current grid fundamental frequency is determined based on the zero-crossing period.

[0149] This application also provides an uninterruptible power supply, which can implement any of the converter control methods provided in this application.

[0150] This application also provides an electronic device in its embodiments. (See reference...) Figure 5 The diagram illustrates a structural schematic of an electronic device suitable for implementing the control method of the converter in the embodiments of this application. The electronic device in the embodiments of this application may include, but is not limited to, fixed terminals such as mobile phones, laptops, PDAs (personal digital assistants), PADs (tablet computers), desktop computers, etc. Figure 5 The electronic device shown is merely an example and should not impose any limitation on the functionality and scope of use of the embodiments of this application.

[0151] like Figure 5 As shown, the electronic device may include a processing unit (e.g., a central processing unit, a graphics processing unit, etc.) 501, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 502 or a program loaded from a storage device 508 into a random access memory (RAM) 503. When the electronic device is powered on, the RAM 503 also stores various programs and data required for the operation of the electronic device. The processing unit 501, ROM 502, and RAM 503 are interconnected via a bus 504. An input / output (I / O) interface 505 is also connected to the bus 504.

[0152] Typically, the following devices can be connected to I / O interface 505: input devices 506 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 507 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; storage devices 508 including, for example, memory cards, hard drives, etc.; and communication devices 509. Communication device 509 allows electronic devices and other devices to exchange data via wireless or wired communication. Although Figure 5Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown. More or fewer devices may be implemented or have alternatively.

[0153] This application also provides a computer program product including computer-readable instructions, which, when executed on an electronic device, cause the electronic device to implement any of the converter control methods provided in this application.

[0154] This application also provides a computer-readable storage medium that carries one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device can implement any of the converter control methods provided in this application.

[0155] It should also be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. In addition, in the device embodiment drawings provided in this application, the connection relationship between modules indicates that they have a communication connection, which can be implemented as one or more communication buses or signal lines.

[0156] Through the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware, or it can be implemented by special-purpose hardware including application-specific integrated circuits, special-purpose CPUs, special-purpose memory, special-purpose components, etc. Generally, any function performed by a computer program can be easily implemented by corresponding hardware, and the specific hardware structure used to implement the same function can also be diverse, such as analog circuits, digital circuits, or special-purpose circuits. However, for this application, software program implementation is more often the preferred implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a readable storage medium, such as a computer floppy disk, USB flash drive, mobile hard disk, ROM, RAM, magnetic disk, or optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, training equipment, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0157] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product.

[0158] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions may be transmitted from one website, computer, training device, or data center to another website, computer, training device, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can store or a data storage device such as a training device or data center that integrates one or more available media. The available media may be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media (e.g., solid-state drives (SSDs)).

[0159] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0160] The above embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them. Although the embodiments of this application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of the embodiments of this application.

Claims

1. A control method for a converter, characterized in that, include: The voltage loop control signal and the current loop control signal are acquired, and the limiting coefficient is determined based on the voltage loop control signal; wherein the limiting coefficient is a coefficient that varies with the voltage loop control signal. The current loop control signal is limited according to the limiting coefficient to generate a modulation signal; Based on the modulation signal, a pulse width modulation signal is obtained, and based on the pulse width modulation signal, the switching state of the switching transistor of the converter is controlled.

2. The method according to claim 1, characterized in that, Based on the voltage loop control signal, the limiting coefficient is determined, including: Obtain the first preset coefficient and the second preset coefficient; The voltage loop control signal and the first preset coefficient are multiplied to obtain the product result; The limiting coefficient is determined based on the difference between the second preset coefficient and the product result; Wherein, the first preset coefficient is used to control the slope of the limiting coefficient as it changes with the voltage loop control signal, and the second preset constant is used to set the upper limit boundary of the limiting coefficient.

3. The method according to claim 1, characterized in that, The current loop control signal is limited according to the limiting coefficient to generate a modulation signal, including: Obtain preset upper limit and preset lower limit values, and determine dynamic upper limit and dynamic lower limit values ​​based on the limiting coefficient, the preset upper limit and the preset lower limit values; The current loop control signal is compared with the dynamic upper limit value and the dynamic lower limit value respectively; If the current loop control signal is greater than the dynamic upper limit value, then the dynamic upper limit value is determined as the modulation signal; If the current loop control signal is less than the dynamic lower limit value, then the dynamic lower limit value is determined as the modulation signal; If the current loop control signal is between the dynamic upper limit value and the dynamic lower limit value, then the current loop control signal is determined as the modulation signal.

4. The method according to claim 1, characterized in that, Obtain the voltage loop control signal, including: The positive bus voltage signal and the negative bus voltage signal at the DC output terminal of the converter are acquired, and the bus voltage signal is obtained based on the positive bus voltage signal and the negative bus voltage signal. The bus voltage signal is subjected to low-pass filtering to obtain the filtered bus voltage signal; The bus voltage error signal is determined based on the difference between the preset target bus voltage and the filtered bus voltage signal. The bus voltage error signal is input to the voltage loop controller, and the voltage loop controller outputs the voltage loop control signal.

5. The method according to claim 1, characterized in that, Acquiring the current loop control signal includes: Acquire the AC input voltage signal and AC input current signal of the converter; Based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal, the initial phase of the AC input voltage signal is corrected to obtain the voltage phase signal; The voltage phase signal and the voltage loop control signal are input to the current loop controller, and the current loop controller outputs the current loop control signal.

6. The method according to claim 5, characterized in that, Based on the zero-crossing time difference between the AC input voltage signal and the AC input current signal, the initial phase of the AC input voltage signal is corrected to obtain a voltage phase signal, including: Obtain the current fundamental frequency of the power grid and perform phase-locked loop processing on the AC input voltage signal to obtain the power grid phase angle; The zero-crossing times of the AC input voltage signal and the AC input current signal are detected in the same period, and the zero-crossing time difference between the zero-crossing times of the AC input voltage signal and the AC input current signal is calculated. Based on the zero-crossing time difference and the current grid fundamental frequency, the target compensation angle is determined, and the grid phase angle is corrected using the target compensation angle to obtain the voltage phase signal.

7. The method according to claim 6, characterized in that, Based on the zero-crossing time difference and the current grid fundamental frequency, the target compensation angle is determined, including: The initial compensation angle is determined based on the zero-crossing time difference and the current fundamental frequency of the power grid; The initial compensation angle is compared with the preset dead zone threshold; If the initial compensation angle is greater than the dead zone threshold, then the initial compensation angle is subjected to first-order hysteresis filtering, and the filtered initial compensation angle is determined as the target compensation angle. If the initial compensation angle is less than or equal to the dead zone threshold, then the target compensation angle is set to zero.

8. The method according to claim 6, characterized in that, Obtain the current fundamental frequency of the power grid, including: The current fundamental frequency of the power grid is obtained in real time using a phase-locked loop module; or The zero-crossing period is calculated based on the zero-crossing time of the AC input voltage signal, and the current grid fundamental frequency is determined based on the zero-crossing period.

9. A control device for a converter, characterized in that, include: An acquisition module is used to acquire voltage loop control signals and current loop control signals, and determine a limiting coefficient based on the voltage loop control signals; wherein the limiting coefficient is a coefficient that varies with the voltage loop control signals; A limiting module is used to limit the current loop control signal according to the limiting coefficient to generate a modulated signal; The control module is used to obtain a pulse width modulation signal based on the modulation signal, and to control the switching state of the switching transistors of the converter based on the pulse width modulation signal.

10. An uninterruptible power supply, characterized in that, Configured to perform the method as described in any one of claims 1 to 8.

Images