CN118432458A - Control method, control device, control equipment, control medium and control program product for Vienna rectifier - Google Patents

Abstract

The application relates to a control method, a control device, a control medium and a control program product of a Vienna rectifier. Wherein the Vienna rectifier is for a charging device, the method comprising: acquiring working electrical parameters of the Vienna rectifier under the conditions that the network side voltage is sinusoidal and three phases are balanced; determining zero sequence modulation quantity required to be injected for inhibiting the median voltage fluctuation of the Vienna rectifier according to a preset functional relation between the median voltage fluctuation and the working electrical parameter of the Vienna rectifier, and injecting the zero sequence modulation quantity into an initial modulation wave of the Vienna rectifier to obtain a target modulation wave; and acquiring network side current of the Vienna rectifier, determining the duty ratio of each phase of switch in the Vienna rectifier according to the network side current and the target modulation wave, determining the switching function of each phase of switch according to the duty ratio, and controlling the running state of the Vienna rectifier through the switching function. The method can inhibit the fluctuation of the neutral point position of the direct-current side capacitor and the distortion of the emission current, and can improve the stability of the charging process and the safety of the charging equipment.

Description

Vienna rectifier control method, device, equipment, medium and program product

Technical Field

The present application relates to the field of power electronics technology, and in particular to a control method, device, computer equipment, storage medium and computer program product of a Vienna rectifier.

Background technique

Vienna rectifier is a bridge rectifier that can be used to convert AC power into DC power. By adding inductance elements and additional capacitors to the bridge rectifier, Vienna rectifier can improve the output voltage quality and reduce harmonic distortion. By adopting vector control strategy, it can achieve precise control of voltage and current and improve the dynamic response and stability of the system. Vienna rectifier has the advantages of high power factor, few switching devices, low switching stress, no switching dead zone problem, and high reliability, which makes it widely used in DC charging of electric vehicles, power transmission and distribution, energy conversion and storage, industrial drives and other fields.

When Vienna rectifier is applied to DC charging equipment, its charging efficiency can be improved through power factor correction. However, when the load changes or the conditions of the power grid change, the potential of the neutral point of the DC side capacitor will fluctuate. The fluctuation of potential may cause the DC voltage output by the charging equipment to change or the emission current to be distorted, affecting the stability of the charging process and the safety of the charging equipment, and even causing harmonic pollution in the power grid or affecting the normal operation of other power equipment.

Summary of the invention

Based on this, it is necessary to provide a control method, device, computer equipment, computer-readable storage medium and computer program product for a Vienna rectifier that can suppress the point fluctuation and harmonic emission of the neutral point of the DC side capacitor in the charging device in order to solve the above-mentioned technical problems.

In a first aspect, the present application provides a control method for a Vienna rectifier, wherein the Vienna rectifier is used for a charging device, and the method includes:

Obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced; wherein the working electrical parameters include the grid-side voltage amplitude and phase angle, charging power and grid-side inductance value;

Determine the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, inject the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier, and obtain the target modulation wave;

The grid-side current of the Vienna rectifier is obtained, the duty cycle of each phase switch in the Vienna rectifier is determined according to the grid-side current and the target modulation wave, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function.

In one embodiment, the method further comprises:

Obtaining a voltage difference between a first capacitor and a second capacitor on a DC side of a Vienna rectifier;

The capacitor voltage difference control amount for suppressing the voltage fluctuation at the neutral point of the Vienna rectifier is determined according to the voltage difference.

In one embodiment, when the grid-side voltage is a sinusoidal quantity and the three phases are balanced, obtaining the working electrical parameters of the Vienna rectifier includes:

Obtain the three-phase voltage and three-phase current of the main circuit of the Vienna rectifier;

The three-phase voltage and the three-phase current are transformed from three-phase to two-phase to obtain the main circuit current and the main circuit voltage in the two-phase coordinate system. The main circuit current and the main circuit voltage in the two-phase coordinate system are used as the working electrical parameters of the Vienna rectifier.

In one embodiment, the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier is determined according to a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters; including:

Obtaining a relationship function between the zero-sequence component of the target modulation wave and the capacitor pressure difference control amount;

With the goal of eliminating the voltage fluctuation at the neutral point, the relationship function is solved to obtain the zero-sequence component;

The zero-sequence modulation quantity is composed of the zero-sequence component and the capacitor pressure difference control quantity.

In one embodiment, the method further comprises:

According to the working electrical parameters, the initial component of the modulation wave of the Vienna rectifier in the two-phase coordinate system is obtained through proportional-integral control;

The initial components of the modulation wave in the two-phase coordinate system are subjected to a three-phase-to-two-phase inverse transformation to obtain the initial components of the modulation wave of each phase in the three-phase coordinate system.

In one embodiment, determining the switching function of each phase switch according to the duty cycle and controlling the operating state of the Vienna rectifier by the switching function includes:

The single-phase carrier PWM control is performed on the initial components of the modulation waves of each item in the three-phase coordinate system according to the duty cycle, and the switching function of the Vienna rectifier is obtained;

A switching signal is generated according to the switching function, and the switching signal is used to control the on and off of each phase switch in the Vienna rectifier.

In a second aspect, the present application further provides a control device for a Vienna rectifier, comprising:

The parameter acquisition module is used to obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is sinusoidal and the three-phase is balanced;

A first modulation control module is used to determine the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, and inject the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier to obtain a target modulation wave;

The second modulation control module is used to obtain the grid-side current of the Vienna rectifier, determine the duty cycle of each phase switch in the Vienna rectifier according to the grid-side current and the target modulation wave, determine the switching function of each phase switch according to the duty cycle, and control the operating state of the Vienna rectifier through the switching function.

In a third aspect, the present application further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

Obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is sinusoidal and the three-phase is balanced;

Determine the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, inject the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier, and obtain the target modulation wave;

The grid-side current of the Vienna rectifier is obtained, the duty cycle of each phase switch in the Vienna rectifier is determined according to the grid-side current and the target modulation wave, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function.

In a fourth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the following steps are implemented:

Obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is sinusoidal and the three-phase is balanced;

Determine the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, inject the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier, and obtain the target modulation wave;

The grid-side current of the Vienna rectifier is obtained, the duty cycle of each phase switch in the Vienna rectifier is determined according to the grid-side current and the target modulation wave, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function.

In a fifth aspect, the present application further provides a computer program product, including a computer program, which implements the following steps when executed by a processor:

Obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is sinusoidal and the three-phase is balanced;

Determine the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, inject the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier, and obtain the target modulation wave;

The grid-side current of the Vienna rectifier is obtained, the duty cycle of each phase switch in the Vienna rectifier is determined according to the grid-side current and the target modulation wave, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function.

The control method, device, computer equipment, storage medium and computer program product of the Vienna rectifier can obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced; the working electrical parameters of the charging device under normal operating conditions can be obtained, and the accuracy of the control can be improved by using the electrical parameters under normal operating conditions as the data basis of the control method; the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier is determined according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, and the zero-sequence modulation amount is injected into the initial modulation wave of the Vienna rectifier to obtain the target modulation wave; the harmonics in the system can be effectively reduced, the mid-point voltage fluctuation can be suppressed, the power factor of the charging device can be improved, and the energy efficiency of the system can be improved; the grid-side current of the Vienna rectifier is obtained, the duty cycle of each phase switch in the Vienna rectifier is determined according to the grid-side current and the target modulation wave, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function, so that the output current can be accurately controlled to improve the stability and energy efficiency of the system. The above method combines the midpoint potential balance control with the current feedback to obtain the modulation wave during the control process, which can suppress the neutral point potential fluctuation of the DC side capacitor and the emission current distortion, and can improve the stability of the charging process and the safety of the charging equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the related technical descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is an application environment diagram of a control method for a Vienna rectifier in one embodiment;

FIG2 is a circuit diagram of a Vienna rectifier in one embodiment;

FIG3 is a schematic flow chart of a control method for a Vienna rectifier in one embodiment;

FIG4 is a schematic diagram of a DC side midpoint potential balance control method of a Vienna rectifier control method in one embodiment;

FIG5 is a schematic diagram of the AC side current feedback control principle of a control method for a Vienna rectifier in one embodiment;

FIG6 is a control principle diagram of a control method for a Vienna rectifier in one embodiment;

FIG7 is a block diagram of a control device for a Vienna rectifier in one embodiment;

FIG. 8 is a diagram showing the internal structure of a computer device in one embodiment.

Detailed ways

In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

The control method of the Vienna rectifier provided in the embodiment of the present application can be applied to the application environment as shown in Figure 1. Among them, the terminal 102 communicates with the server 104 through the network. The data storage system can store the data that the server 104 needs to process. The data storage system can be integrated on the server 104, or it can be placed on the cloud or other network servers. Among them, the terminal 102 can be but is not limited to various charging piles, user terminals such as smart phones and tablets, personal computers and laptops, etc. The server 104 can be implemented with an independent server or a server cluster composed of multiple servers, and can include a background server, a payment gateway server, a data analysis server, and an energy management system server, etc.

With the increasing popularity of electrified transportation around the world, electric vehicles and their related charging facilities are connected to the power grid on a large scale. The access of large-scale electric vehicle charging clusters will bring power quality problems such as three-phase imbalance, voltage loss, and harmonic pollution to the power grid. Harmonic pollution refers to the presence of non-integer cycle voltage or current waveforms in the power system. Harmonic pollution will increase the internal loss of the equipment, reduce energy efficiency, and even affect the normal operation of the equipment, increase the energy consumption and resource waste of the power system. Therefore, how to reduce harmonic pollution in the power system is one of the urgent problems to be solved in the power system. Vienna rectifier is a three-phase three-level PWM rectifier, and its circuit structure is shown in Figure 2. It includes three power crystals, which can be used to generate sine wave input current and controllable voltage output. Vienna rectifier can achieve efficient bidirectional power conversion, so it is widely used in charging equipment such as car charging piles. However, Vienna type charging equipment has the problem of DC side capacitor neutral point potential fluctuation and emission current distortion, which affects the stability of the charging process and the safety of the charging equipment, and even causes harmonic pollution in the power grid or affects the normal operation of other power equipment.

In an exemplary embodiment, as shown in FIG3 , a control method for a Vienna rectifier is provided, which is described by taking the application environment in FIG1 as an example, and includes the following steps 202 to 206. The Vienna rectifier is used for a charging device, which may be a car charging pile, and the method includes:

Step 202: Obtain operating electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced.

Among them, the working electrical parameters may include the grid-side voltage amplitude phase angle, charging power, and grid-side inductance. The grid-side voltage amplitude phase angle refers to the voltage amplitude and phase angle of the grid or power supply injected into the Vienna rectifier. Charging power refers to the charging power of the electric vehicle. Grid-side inductance refers to the sum of the inductance values of the Vienna rectifier and the system. Three-phase balance means that the amplitudes of the voltage and current of each phase in the three-phase power system are the same.

For example, a sensing device such as a voltage sensor, a current sensor, a current transformer or an oscilloscope can be used to measure and record voltage data at a connection port where the Vienna rectifier is connected to the power grid, and to measure and record current data at the AC side.

Step 204, determining the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, injecting the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier to obtain the target modulation wave.

Among them, the zero-sequence modulation amount refers to the waveform used to adjust the neutral point voltage. The initial modulation wave refers to the modulation signal waveform generated when the Vienna rectifier starts working. The target modulation wave refers to the modulation signal waveform output by the Vienna rectifier that is expected to be obtained after adjustment according to the control target.

Exemplarily, the relationship between the mid-point voltage fluctuation and the working electrical parameters of the Vienna rectifier can be analyzed and modeled to obtain a preset functional relationship, and the mid-point voltage fluctuation and other working electrical parameters measured in the historical data are substituted into the function to calculate the required zero-sequence modulation amount. The target modulation wave can be obtained by controlling the modulation wave generation algorithm or directly modifying the modulation signal in the controller. During the operation of the rectifier, the mid-point voltage fluctuation and the working electrical parameters can be monitored in real time and the injected zero-sequence modulation amount and modulation waveform can be adjusted according to the actual situation to ensure the stable operation of the rectifier and the suppression effect of the mid-point voltage fluctuation.

Step 206, obtaining the grid-side current of the Vienna rectifier, determining the duty cycle of each phase switch in the Vienna rectifier according to the grid-side current and the target modulation wave, determining the switching function of each phase switch according to the duty cycle, and controlling the operating state of the Vienna rectifier through the switching function.

Among them, the grid-side current refers to the current received by the rectifier from the power grid. The switches of each phase in the rectifier refer to the power switching devices used to control the rectifier, such as IGBT (insulated gate bipolar transistor) or MOSFET (metal oxide semiconductor field effect transistor), GTO (gate controlled thyristor) or IGCT (insulated gate double controlled thyristor), etc. For Vienna rectifier, the power switching device mainly refers to IGBT. Duty cycle refers to the ratio of the conduction time of the switching device in one cycle to the total cycle time. The switching function refers to the function or algorithm that describes the switching state of each phase in the rectifier.

For example, the grid-side current value can be obtained through measuring devices such as current sensors, and the duty cycle of each phase switch can be determined based on the current demand and the modulation waveform. A PID controller, model predictive controller or other control algorithms can be used to generate a switching function based on the duty cycle and system control strategy, and then the working state of each phase switch device in the rectifier is controlled by a controller or logic circuit.

In the control method of the Vienna rectifier, the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced are obtained; the working electrical parameters of the charging device under normal operating conditions can be obtained, and the accuracy of the control can be improved by using the electrical parameters under normal operating conditions as the data basis of the control method; the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier is determined according to the preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, and the zero-sequence modulation amount is injected into the initial modulation wave of the Vienna rectifier to obtain the target modulation wave; the harmonics in the system can be effectively reduced, the mid-point voltage fluctuation can be suppressed, the power factor of the charging device can be improved, and the energy efficiency of the system can be improved; the grid-side current of the Vienna rectifier is obtained, the duty cycle of each phase switch in the Vienna rectifier is determined according to the grid-side current and the target modulation wave, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function, so that the output current can be accurately controlled to improve the stability and energy efficiency of the system. The above method combines the midpoint potential balance control with the current feedback to obtain the modulation wave during the control process, which can suppress the neutral point potential fluctuation of the DC side capacitor and the emission current distortion, and can improve the stability of the charging process and the safety of the charging equipment.

In an exemplary embodiment, the method further includes: obtaining a voltage difference between a first capacitor and a second capacitor on a DC side of the Vienna rectifier; and determining a capacitor voltage difference control amount for suppressing voltage fluctuations at a neutral point of the Vienna rectifier according to the voltage difference.

The first capacitor and the second capacitor refer to two capacitors connected through a neutral point in the Vienna rectifier, which can play a role in voltage division. The capacitor voltage difference control amount refers to a control amount used to change the voltage difference between the first capacitor and the second capacitor.

Exemplarily, the voltage difference between the first capacitor and the second capacitor can be determined by historical operating parameters or by simulation calculation, and the capacitor voltage difference control amount for suppressing the voltage fluctuation at the center point of the Vienna rectifier can be determined by a feedback control method based on the voltage difference.

In an exemplary embodiment, when the grid-side voltage is a sinusoidal quantity and the three-phases are balanced, the operating electrical parameters of the Vienna rectifier are obtained, including: obtaining the three-phase voltage and three-phase current of the main circuit of the Vienna rectifier; performing a three-phase-to-two-phase transformation on the three-phase voltage and the three-phase current to obtain the main circuit current and the main circuit voltage in a two-phase coordinate system, and using the main circuit current and the main circuit voltage in the two-phase coordinate system as the operating electrical parameters of the Vienna rectifier.

Among them, three-phase-to-two-phase transformation refers to converting three-phase current or voltage into two equivalent two-phase currents or voltages. A two-phase coordinate system refers to a coordinate system of two-phase current or voltage.

Exemplarily, the acquired three-phase current or voltage can be subjected to park transformation, that is, the three-phase current or voltage is converted from the stationary ABC coordinate system to the rotating dq coordinate system, thereby converting the time-varying problem into a relatively simple constant coefficient problem to simplify the analysis and calculation process.

In an exemplary embodiment, the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier is determined based on a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters; including: obtaining the relationship function between the zero-sequence component of the target modulation wave and the capacitor pressure difference control amount; solving the relationship function with the goal of eliminating the mid-point voltage fluctuation to obtain the zero-sequence component; and forming the zero-sequence modulation amount with the zero-sequence component and the capacitor pressure difference control amount.

Among them, the zero-sequence component refers to the component without symmetry in the three-phase voltage or current. Introducing the zero-sequence component in the control link can adjust the voltage distribution and reduce the voltage fluctuation at the midpoint.

Exemplarily, the relationship function between the zero-sequence component of the target modulation wave and the capacitor pressure difference control amount can be obtained through mathematical modeling and the like, the mid-point voltage fluctuation can be used as a feedback signal, the voltage tolerance can be adjusted through a controller to minimize the mid-point voltage fluctuation, and the zero-sequence component and the capacitor pressure difference control amount can be directly added to obtain the zero-sequence modulation amount.

In an exemplary embodiment, the method further includes: obtaining the initial components of the modulation wave of the Vienna rectifier in a two-phase coordinate system through proportional-integral control according to the working electrical parameters; performing a three-phase-to-two-phase inverse transformation on the initial components of the modulation wave in the two-phase coordinate system to obtain the initial components of the modulation wave of each phase in the three-phase coordinate system.

Among them, proportional integral control refers to a control method that generates a control output based on the difference between the size of the error and the reference value and the accumulated amount of the error. Three-phase to two-phase inverse transformation refers to the process of converting three-phase voltage or current into two-phase voltage or current, which can be achieved by vector rotation or transformation matrix. The initial component of the modulation wave refers to the basic waveform used to generate the PWM signal.

For example, a proportional-integral (PI) controller can be designed according to the control objective and system characteristics, and the proportional and integral parameters can be adjusted so that the proportional term is responsible for generating output according to the current error size, and the integral term is responsible for eliminating static errors. The output generated by the controller is the initial component of the modulation wave of the Vienna rectifier in the two-phase coordinate system, and the three-phase to two-phase inverse transformation can be achieved through the park inverse transformation.

In an exemplary embodiment, the switching function of each phase switch is determined according to the duty cycle, and the operating state of the Vienna rectifier is controlled by the switching function, including: performing single-phase carrier PWM control on the initial components of the modulation waves of each item in the three-phase coordinate system according to the duty cycle to obtain the switching function of the Vienna rectifier; generating a switching signal according to the switching function, and the switching signal is used to control the conduction and cutoff of each phase switch in the Vienna rectifier.

Among them, single-phase carrier PWM (Pulse Width Modulation) control refers to a signal modulation process of modulating a high-frequency carrier signal into a pulse sequence having a pulse width related to the AC voltage to be controlled.

Exemplarily, the PWM signal of each phase can be calculated based on the duty cycle and the modulation wave, and based on the obtained PWM signal, a switching signal for controlling the conduction and cutoff of each switching device in the Vienna rectifier is generated according to the topology structure of the Vienna rectifier, and the switching signal generated by the drive circuit is converted into an actual switching control signal to control the conduction and cutoff of the power switching device.

In an exemplary embodiment, a control method for a Vienna rectifier is provided, comprising the following steps:

Step 402, the voltage fluctuation at the neutral point of the DC side of Vienna rectifier and the corresponding solution are theoretically derived. Assuming that the voltage on the grid side is a sinusoidal quantity and the three phases are balanced, the voltage of phase A is:

(1)

Where: is the grid-side voltage amplitude, is the angular frequency of the power frequency, is the initial phase angle of voltage.

When the three-phase output power is P, the power factor is 1 in steady state, and the inductance resistance is ignored, the initial modulation wave at this time is:

(2)

Where: is the initial modulation wave, is the effective value of the network voltage, is the modulation wave amplitude, is the initial phase angle of the modulation wave, For AC inductance measurement, is the charging power.

The state equation of the DC side is:

(3)

When there is a neutral point balance control, the latter part of the above formula can be ignored, and considering that the power factor of the control system is 1, the following expression exists:

(4)

Where: is the DC side capacitance, is the AC side current value, is a symbolic function

Solving the above differential equation yields:

(5)

From the theoretically derived expression, it can be seen that if neutral point balance control is added or the control is added improperly, there will be a voltage difference between the upper and lower capacitor voltages on the DC side, that is, the midpoint voltage fluctuates, and the main component of the main fluctuation is the third component. When the midpoint voltage fluctuates, it will have different degrees of impact on the charging effect of the charger, harmonic emission pollution, and the tolerance limit of the device, so targeted control needs to be set.

According to the above derivation results, the present invention proposes to limit the voltage fluctuation at the neutral point by adding the corresponding zero-sequence component to the modulation wave and introducing the capacitor voltage difference to assist in the control. When the zero-sequence component is added, the following expression is obtained:

(6)

To eliminate the midpoint voltage fluctuation, the above expression can be solved to obtain:

(7)

In the present invention, the zero-sequence modulation amount is designed to be the zero-sequence component and the auxiliary part of the introduced capacitor pressure difference, and the zero-sequence component is a simplified expression of the above formula:

(8)

Step 404, midpoint balance control design. As shown in FIG4, based on the original modulation wave, the charging power is controlled by the function The modulation wave amplitude M, then through The voltage fluctuation feedback branch is added to the modulation wave branch to form the final modulation wave. The final output modulation wave is:

(9)

The functions in the design diagram are expressed as follows:

(10)

(11)

(12)

Step 406, theoretical derivation of self-harmonic current emission and corresponding solutions. This part mainly derives the self-harmonic emission of the main circuit of the rectifier of the Vienna DC charger through theoretical derivation, and designs the control part according to the analysis to minimize the current distortion of the charger as much as possible. The relationship between the switch AC side port voltage and the AC side current can be expressed as:

(13)

This expression shows that the current distortion on the grid side depends on the port voltage of the switching device, and the waveform of the port voltage depends on the sign of the grid-side current, the midpoint voltage fluctuation and the modulation wave.

According to the above derivation results, by adding the feedback of the grid-side current sign function to the modulation wave, the port voltage of the switching device is made as sinusoidal as possible, so as to reduce the distortion of the AC side current as much as possible. At this time, the corresponding modulation wave expression should be:

(14)

According to the steady-state condition, the port voltage of the switching device can be obtained as:

(15)

The state equation on the grid side is:

(16)

In the formula is the switching function. In order to reduce the current distortion, the relationship between the switching function expression and the modulation wave is as follows:

(17)

Step 408, circuit feedback design for reducing the emission current. The controller is designed according to the derivation process and conclusion of step 406. The design result is shown in FIG5. Based on the modulation wave generated in step 402 and step 404, the grid-side current passes through the sign function module. The duty cycle is formed under the action of , and finally the pulses required for each phase switch can be output through the PWM link. The functions in the figure are expressed as:

(18)

(19)

At this time, after the sign current changes based on the original modulation wave, the problem of inconsistent angles between the grid-side current and the port voltage can be reduced, thereby reducing the degree of current distortion.

Step 410, the overall rectifier control flow chart is designed. It mainly includes DC side voltage control, current tracking grid side voltage control under dq axis, neutral point voltage balance control, current feedback control and PWM modulation link. The implementation of this part is shown in Figure 6: the first part is the sampling and park transformation of each part of the main circuit to obtain each electrical variable under the dq axis; the second part is the DC side voltage constant voltage control and AC side current tracking control. This part is carried out in the dq coordinate system, and each part adopts PI control. The final result is obtained by the inverse park transformation to obtain the initial component of the modulation wave of each phase; the third part is the neutral point balance control part and the grid side current feedback part, and finally the switching function is obtained through single-phase carrier PWM control.

The above are the implementation principles and steps of the control method of the Vienna rectifier with midpoint potential balance for charger based on reducing harmonic emission of the present invention. The control method of the Vienna rectifier provided by the present invention is based on the theoretical derivation of midpoint potential fluctuation and self-current emission, and adds midpoint potential balance control and current feedback combined with modulation wave control method based on traditional dq control. Compared with SVM, natural coordinate system control and other control methods, it better limits the DC side midpoint voltage fluctuation and its own harmonic emission problems. This control method considers the problem more comprehensively and has a wider range of application.

It should be understood that, although the various steps in the flowcharts involved in the above-mentioned embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps does not have a strict order restriction, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above-mentioned embodiments can include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.

Based on the same inventive concept, the embodiment of the present application also provides a control device for a Vienna rectifier for implementing the control method for the Vienna rectifier involved above. The implementation scheme for solving the problem provided by the device is similar to the implementation scheme recorded in the above method, so the specific limitations in the control device embodiments of one or more Vienna rectifiers provided below can refer to the limitations of the control method for the Vienna rectifier above, and will not be repeated here.

In an exemplary embodiment, as shown in FIG7 , a control device for a Vienna rectifier is provided, comprising: a parameter acquisition module, a first modulation control module and a second modulation control module, wherein:

The parameter acquisition module is used to obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced; the working electrical parameters include the grid-side voltage amplitude phase angle, charging power and grid-side inductance value.

A first modulation control module is used to determine the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameters, and inject the zero-sequence modulation amount into the initial modulation wave of the Vienna rectifier to obtain a target modulation wave;

The second modulation control module is used to obtain the grid-side current of the Vienna rectifier, determine the duty cycle of each phase switch in the Vienna rectifier according to the grid-side current and the target modulation wave, determine the switching function of each phase switch according to the duty cycle, and control the operating state of the Vienna rectifier through the switching function.

In an exemplary embodiment, the first modulation control module is also used to: obtain the voltage difference between the first capacitor and the second capacitor on the DC side of the Vienna rectifier; and determine the capacitor voltage difference control amount for suppressing the midpoint voltage fluctuation of the Vienna rectifier based on the voltage difference.

In an exemplary embodiment, the parameter acquisition module is also used to: obtain the three-phase voltage and three-phase current of the main circuit of the Vienna rectifier; perform a three-phase-to-two-phase transformation on the three-phase voltage and three-phase current to obtain the main circuit current and main circuit voltage in a two-phase coordinate system, and use the main circuit current and main circuit voltage in the two-phase coordinate system as the working electrical parameters of the Vienna rectifier.

In an exemplary embodiment, the first modulation control module is also used to: obtain a relationship function between the zero-sequence component of the target modulation wave and the capacitor pressure difference control amount; solve the relationship function with the goal of eliminating the midpoint voltage fluctuation to obtain the zero-sequence component; and form a zero-sequence modulation amount with the zero-sequence component and the capacitor pressure difference control amount.

In an exemplary embodiment, in one of the embodiments, the second modulation control module is also used to: obtain the initial components of the modulation wave of the Vienna rectifier in the two-phase coordinate system through proportional-integral control according to the working electrical parameters; perform a three-phase-to-two-phase inverse transformation on the initial components of the modulation wave in the two-phase coordinate system to obtain the initial components of the modulation wave of each phase in the three-phase coordinate system.

In an exemplary embodiment, the second modulation control module is also used to: perform single-phase carrier PWM control on the initial components of the modulation waves of each item in the three-phase coordinate system according to the duty cycle to obtain the switching function of the Vienna rectifier; generate a switching signal according to the switching function, and the switching signal is used to control the conduction and cutoff of each phase switch in the Vienna rectifier.

Each module in the control device of the Vienna rectifier can be implemented in whole or in part by software, hardware and a combination thereof. Each module can be embedded in or independent of a processor in a computer device in the form of hardware, or can be stored in a memory in a computer device in the form of software, so that the processor can call and execute operations corresponding to each module.

In an exemplary embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be shown in FIG8. The computer device includes a processor, a memory, an input/output interface (Input/Output, referred to as I/O) and a communication interface. Among them, the processor, the memory and the input/output interface are connected through a system bus, and the communication interface is connected to the system bus through the input/output interface. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The database of the computer device is used to store various data and working parameters involved in the charging control process or the Vienna rectifier control process, such as current, voltage, power, charging state and fault diagnosis information. The input/output interface of the computer device is used to exchange information between the processor and the external device. The communication interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a control method of a Vienna rectifier is implemented.

Those skilled in the art will understand that the structure shown in FIG. 8 is merely a block diagram of a partial structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different arrangement of components.

In one embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the steps in the above-mentioned method embodiments when executing the computer program. The computer device may be a computer device as shown in FIG8 .

In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps in the above method embodiments are implemented.

In one embodiment, a computer program product is provided, including a computer program, which implements the steps in the above method embodiments when executed by a processor.

It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to the memory, database or other medium used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in each embodiment provided in this application may include at least one of a relational database and a non-relational database. Non-relational databases may include distributed databases based on blockchains, etc., but are not limited to this. The processor involved in each embodiment provided in this application may be a general-purpose processor, a central processing unit, a graphics processor, a digital signal processor, a programmable logic device, a data processing logic device based on quantum computing, etc., but are not limited to this.

The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims (10)

1. A control method for a Vienna rectifier, wherein the Vienna rectifier is used for a charging device, and the method comprises: Obtaining the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced; wherein the working electrical parameters include the grid-side voltage amplitude and phase angle, charging power and grid-side inductance value; Determining a zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameter, and injecting the zero-sequence modulation amount into an initial modulation wave of the Vienna rectifier to obtain a target modulation wave; Obtain the grid-side current of the Vienna rectifier, determine the duty cycle of each phase switch in the Vienna rectifier according to the grid-side current and the target modulation wave, determine the switching function of each phase switch according to the duty cycle, and control the operating state of the Vienna rectifier through the switching function. 2. The method according to claim 1, characterized in that the method further comprises: Obtaining a voltage difference between a first capacitor and a second capacitor on a DC side of the Vienna rectifier; A capacitor voltage difference control amount for suppressing voltage fluctuation at a neutral point of the Vienna rectifier is determined according to the voltage difference. 3. The method according to claim 1, characterized in that, when the grid-side voltage is a sinusoidal quantity and the three-phase is balanced, obtaining the working electrical parameters of the Vienna rectifier comprises: Obtaining three-phase voltage and three-phase current of a main circuit of the Vienna rectifier; The three-phase voltage and the three-phase current are transformed from three phases to two phases to obtain the main circuit current and the main circuit voltage in a two-phase coordinate system, and the main circuit current and the main circuit voltage in the two-phase coordinate system are used as the working electrical parameters of the Vienna rectifier. 4. The method according to claim 2, characterized in that the step of determining the zero-sequence modulation amount required to be injected to suppress the mid-point voltage fluctuation of the Vienna rectifier according to a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameter comprises: Obtaining a relationship function between a zero-sequence component of a target modulation wave and the capacitor pressure difference control amount; With the goal of eliminating the midpoint voltage fluctuation, solving the relationship function to obtain the zero-sequence component; The zero-sequence modulation amount is composed of the zero-sequence component and the capacitor pressure difference control amount. 5. The method according to claim 1, characterized in that the method further comprises: According to the working electrical parameters, an initial component of a modulation wave of the Vienna rectifier in a two-phase coordinate system is obtained through proportional-integral control; The initial components of the modulation waves in the two-phase coordinate system are subjected to a three-phase-to-two-phase inverse transformation to obtain the initial components of the modulation waves of each phase in the three-phase coordinate system. 6. The method according to claim 1, characterized in that the step of determining the switching function of each phase switch according to the duty cycle and controlling the operating state of the Vienna rectifier by the switching function comprises: Performing single-phase carrier PWM control on the initial components of the modulation waves of each item in the three-phase coordinate system according to the duty cycle to obtain a switching function of the Vienna rectifier; A switching signal is generated according to the switching function, and the switching signal is used to control the on and off of each phase switch in the Vienna rectifier. 7. A control device for a Vienna rectifier, characterized in that the Vienna rectifier is used for a charging device, and the device comprises: A parameter acquisition module, used to obtain the working electrical parameters of the Vienna rectifier under the condition that the grid-side voltage is a sinusoidal quantity and the three-phase is balanced; wherein the working electrical parameters include the grid-side voltage amplitude phase angle, charging power and grid-side inductance value; A first modulation control module, used for determining a zero-sequence modulation amount required to be injected for suppressing the mid-point voltage fluctuation of the Vienna rectifier according to a preset functional relationship between the mid-point voltage fluctuation of the Vienna rectifier and the working electrical parameter, and injecting the zero-sequence modulation amount into an initial modulation wave of the Vienna rectifier to obtain a target modulation wave; The second modulation control module is used to obtain the grid-side current of the Vienna rectifier, determine the duty cycle of each phase switch in the Vienna rectifier according to the grid-side current and the target modulation wave, determine the switching function of each phase switch according to the duty cycle, and control the operating state of the Vienna rectifier through the switching function. 8. A computer device, comprising a memory and a processor, wherein the memory stores a computer program, wherein the processor implements the steps of the method according to any one of claims 1 to 6 when executing the computer program. 9. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented. 10. A computer program product, comprising a computer program, characterized in that when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.