A method for composite control of a VIENNA rectifier

Abstract

The present application relates to the technical field of power electronic converter control, and proposes a VIENNA rectifier composite control method, which comprises: collecting three-phase alternating current voltage and three-phase filter inductance current on the grid side, and obtaining current feedback signals through coordinate transformation; obtaining bus voltage and load current on the DC side, superimposing after processing by a voltage outer loop proportional integral regulator and a load current feedforward unit, and obtaining current reference signals; performing error calculation, state observation and active disturbance rejection through a current inner loop active disturbance rejection controller, and obtaining voltage control signals; and performing modulation operation through a pulse width modulation unit, obtaining three-phase switch driving signals, and inputting control to power switch tubes. The present application improves the dynamic regulation capability of the three-phase VIENNA rectifier under the scene of frequent load mutation as a whole, so that it can meet the performance requirements of bus voltage dynamic stability and grid side power quality in practical applications such as electric vehicle charging piles and communication base station power supply.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter control technology, and in particular to a composite control method for a VIENNA rectifier. Background Technology

[0002] The VIENNA rectifier is a three-phase, three-level power factor correction rectifier. Due to its advantages such as fewer switching devices, low harmonic content, and high power factor, it is widely used in DC power supply scenarios such as electric vehicle charging piles, communication base station power supply, and industrial frequency converter drives. Currently, in engineering practice, a dual-loop control scheme combining an outer voltage loop and an inner current loop is commonly used. The outer voltage loop uses a proportional-integral regulator to maintain stable output by adjusting the DC bus voltage, while the inner current loop uses a proportional-integral regulator to achieve unity power factor operation by tracking the current reference signal.

[0003] However, in real-world applications such as charging piles and communication power supplies where loads frequently change abruptly, the dynamic adjustment capability of traditional dual-loop proportional-integral control schemes is insufficient. The outer voltage loop relies solely on passive adjustment based on the bus voltage deviation, failing to compensate for the power gap in a timely manner during the initial stage of load changes, resulting in a large dynamic drop in bus voltage. Meanwhile, the inner current loop proportional-integral regulator has limited disturbance rejection capability, leading to aggravated distortion of the zero-crossing point of the input current during current transients caused by load changes, resulting in a decline in overall control performance. Summary of the Invention

[0004] In view of this, the present invention proposes a composite control method for VIENNA rectifiers, which solves the problems of insufficient dynamic adjustment capability of traditional dual-loop proportional-integral control schemes. The voltage outer loop relies solely on the bus voltage deviation for passive adjustment, which cannot compensate for the power gap in time during the initial stage of load change, resulting in a large dynamic drop in bus voltage. At the same time, the current inner loop proportional-integral regulator has limited anti-disturbance capability, and the zero-crossing distortion of the input current is aggravated during the current transient process caused by load change, resulting in a decrease in overall control performance.

[0005] The technical solution of this invention is implemented as follows: This invention provides a composite control method for a VIENNA rectifier, comprising the following steps: The three-phase AC voltage and the three-phase filter inductor current on the grid side of the three-phase VIENNA rectifier are collected, and the coordinate transformation of the three-phase AC voltage and the three-phase filter inductor current is performed to obtain the current feedback signal. The DC-side bus voltage, DC-side bus voltage reference value, and DC-side load current of the three-phase VIENNA rectifier are obtained. The difference between the DC-side bus voltage and the DC-side bus voltage reference value is calculated and proportional-integral operation is performed by the voltage outer loop proportional-integral regulator to obtain the voltage outer loop regulating current. The DC-side load current is fed forward by the load current feedforward unit to obtain the feedforward compensation current. The voltage outer loop regulating current and the feedforward compensation current are superimposed by addition operation to obtain the current reference signal. The voltage control signal is obtained by performing error signal calculation, state observation operation and active disturbance rejection adjustment operation on the current feedback signal and current reference signal through the current inner loop active disturbance rejection controller. The voltage control signal is modulated by the pulse width modulation unit to obtain the three-phase switch drive signal, and the three-phase VIENNA rectifier power switch is controlled based on the three-phase switch drive signal.

[0006] In some embodiments, the process of acquiring the DC-side bus voltage, DC-side bus voltage reference value, and DC-side load current of the three-phase VIENNA rectifier, performing difference calculation and proportional-integral operation on the DC-side bus voltage and the DC-side bus voltage reference value through a voltage outer loop proportional-integral regulator to obtain the voltage outer loop regulating current, performing feedforward operation on the DC-side load current through a load current feedforward unit to obtain the feedforward compensation current, and superimposing the voltage outer loop regulating current and the feedforward compensation current through an addition operation to obtain the current reference signal includes: The DC bus voltage and DC bus voltage reference value of the three-phase VIENNA rectifier are obtained. The difference between the DC bus voltage and the DC bus voltage reference value are calculated by the difference calculation unit, and the bus voltage error signal is output. The bus voltage error signal is sent to the voltage outer loop proportional-integral regulator, and the voltage outer loop regulating current is output. Obtain the DC-side load current of the three-phase VIENNA rectifier, send the DC-side load current to the load current feedforward unit for feedforward calculation, and output the feedforward compensation current. The voltage outer loop regulating current and the feedforward compensation current are fed into the addition unit, and the voltage outer loop regulating current and the feedforward compensation current are superimposed through addition operation to output a current reference signal.

[0007] In some embodiments, the voltage outer loop proportional-integral regulator includes an error signal limiting unit, a proportional operation unit, and an integral operation unit. The error signal limiting unit limits the bus voltage error signal and outputs a limited error signal. The proportional operation unit performs proportional operation on the limited error signal and outputs a proportional current component. The integral operation unit performs integral operation on the limited error signal and outputs an integral current component. The proportional current component and the integral current component are added together by an addition operation to output the voltage outer loop regulating current.

[0008] In some embodiments, the load current feedforward unit includes a load current filtering unit and a load current gain adjustment unit. The load current filtering unit performs filtering calculations on the DC-side load current and outputs a filtered load current. The load current gain adjustment unit performs gain adjustment calculations on the filtered load current and outputs a feedforward compensation current.

[0009] In some embodiments, the addition unit includes a current superposition unit and a current reference limiting unit. The current superposition unit performs an addition operation on the voltage outer loop regulation current and the feedforward compensation current to output a current superposition signal. The current reference limiting unit limits the current superposition signal according to a preset upper current limit value and a preset lower current limit value to output a current reference signal.

[0010] In some embodiments, the step of performing error signal calculation, state observation operation, and active disturbance rejection adjustment operation on the current feedback signal and the current reference signal through the current inner loop active disturbance rejection controller to obtain the voltage control signal includes: The current reference signal and the current feedback signal are sent to the current reference tracking unit, and the current reference signal and the current feedback signal are dynamically shaped to output the current reference tracking signal. The historical values ​​of the current feedback signal and the voltage control signal are sent to the extended state observation unit, and the historical values ​​of the current feedback signal and the voltage control signal are jointly observed and calculated to output the current observation signal and the disturbance estimation signal. The current reference tracking signal, the current observation signal, and the disturbance estimation signal are sent to the state error feedback adjustment unit. Error signal calculation is performed on the current reference tracking signal and the current observation signal, and disturbance compensation calculation is performed based on the disturbance estimation signal to output the voltage control signal.

[0011] In some embodiments, the current reference tracking unit includes a reference limiting unit, a dynamic weighting unit, and a tracking calculation unit; The current reference signal is limited by the reference limiting unit to output a limited current reference signal. The dynamic weighting unit performs weight adjustment calculations on the limiting current reference signal based on the current feedback signal, and outputs a weighted current reference signal. The tracking calculation unit performs tracking calculations on the weighted current reference signal and outputs a current reference tracking signal.

[0012] In some embodiments, the extended state observation unit includes a current state estimation unit and a disturbance estimation unit; The current state estimation unit performs state estimation calculations on the historical values ​​of the current feedback signal and the voltage control signal, and outputs the current observation signal. The disturbance estimation unit performs disturbance estimation calculations on the current feedback signal and the current observation signal, and outputs a disturbance estimation signal.

[0013] In some embodiments, the state error feedback adjustment unit includes an error signal calculation unit, a disturbance compensation unit, and a voltage control generation unit; The error signal calculation unit performs a difference calculation on the current reference tracking signal and the current observation signal, and outputs a basic error signal. The disturbance compensation unit performs compensation calculations on the basic error signal and the disturbance estimation signal, and outputs a compensated error signal. The voltage control generation unit performs feedback calculations and amplitude limiting on the compensation error signal, and outputs a voltage control signal.

[0014] In some embodiments, the step of modulating the voltage control signal using a pulse width modulation unit to obtain a three-phase switch drive signal, and then controlling the three-phase VIENNA rectifier power switch transistors based on the three-phase switch drive signal, includes: The voltage control signal is subjected to amplitude limiting and biasing operations by the modulation signal preprocessing unit, and the modulation signal is output. The carrier generation unit performs carrier generation calculations on the preset modulation frequency and outputs a carrier signal. The modulation signal and the carrier signal are compared and calculated by the pulse width comparison unit, and a three-phase switch drive signal is output. The three-phase switch drive signal is used as the control input for the three-phase VIENNA rectifier power switch.

[0015] The VIENNA rectifier composite control method of the present invention has the following advantages over the prior art: (1) By introducing a load current feedforward unit on the basis of the voltage outer loop proportional-integral regulator, the feedforward compensation current obtained by the DC side load current through feedforward calculation is superimposed with the voltage outer loop regulation current to generate a current reference signal. This enables the voltage outer loop to sense the load current change in advance and actively compensate for the power gap when the load changes suddenly, thereby significantly suppressing the dynamic drop amplitude of the DC side bus voltage under the load change condition. At the same time, by using the current inner loop active disturbance rejection controller to perform error signal calculation, state observation calculation and active disturbance rejection regulation calculation on the current feedback signal and current reference signal, the extended state observer is used to estimate and compensate for the comprehensive disturbances such as grid voltage fluctuation, load change and parameter uncertainty online, which enhances the active suppression capability of the current inner loop against external disturbances, effectively reduces the distortion degree of the input current near the zero crossing point, and improves the waveform quality of the grid current. This improves the dynamic regulation capability of the three-phase VIENNA rectifier under the scenario of frequent load changes, so that it can take into account the performance requirements of both the dynamic stability of the bus voltage and the power quality of the grid side in practical applications such as electric vehicle charging piles and communication base station power supply. (2) By refining the voltage outer loop proportional-integral regulator into a series structure of error signal limiting unit, proportional operation unit and integral operation unit, the bus voltage error signal is limited before entering the proportional-integral operation, avoiding the distortion caused by integral saturation when the error is too large, and ensuring that the output range of the voltage outer loop regulation current is controllable; by refining the load current feedforward unit into a cascade structure of load current filtering unit and load current gain adjustment unit, the DC side load current is filtered before participating in the feedforward compensation operation, effectively suppressing the influence of measurement noise on the accuracy of feedforward compensation current, enabling the feedforward compensation current to accurately reflect the low-frequency change trend of the load current, and improving the accuracy of the feedforward compensation response to load sudden changes; by refining the addition operation unit into a series structure of current superposition unit and current reference limiting unit, on the basis of completing the superposition of voltage outer loop regulation current and feedforward compensation current, upper and lower limit constraints are applied to the superposition result, ensuring that the final output current reference signal is always within the range of the rated current of the power device and the safe operation of the system, thereby improving the dynamic response capability of the bus voltage while taking into account the safety and reliability of the system. (3) By refining the current reference tracking unit into a cascaded structure of a reference limiting unit, a dynamic weighting unit, and a tracking operation unit, the current reference signal undergoes amplitude constraint and dynamic weight adjustment based on the current feedback signal before entering the tracking operation, thereby generating a current reference tracking signal that can adaptively shape with load changes, avoiding transient impacts on the inner loop controller when the current reference signal changes abruptly; by refining the extended state observation unit into a parallel structure of a current state estimation unit and a disturbance estimation unit, and introducing historical values ​​of the voltage control signal to participate in the joint observation operation, the observer can more accurately assess the current state and the overall disturbance based on the prior information of the control quantity. Online estimation improves the accuracy of current observation signals and disturbance estimation signals. By refining the state error feedback adjustment unit into a series structure of error signal calculation unit, disturbance compensation unit, and voltage control generation unit, the basic error signal undergoes active compensation of the disturbance estimation signal before entering the feedback calculation, thus eliminating the disturbance influence from the error channel in advance. The compensated error signal is then subjected to feedback calculation and amplitude limiting to generate the voltage control signal. This ensures the amplitude safety of the output voltage control signal while suppressing transient disturbances caused by grid voltage fluctuations and load changes, thereby improving the active suppression capability and current tracking accuracy of the current inner loop active disturbance rejection controller under complex disturbance conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of a composite control method for a VIENNA rectifier according to the present invention; Figure 2 This is a schematic diagram of the sampling and coordinate transformation system structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the current reference generation system structure according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the current inner loop active disturbance rejection control system according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the pulse width modulation and driving system structure according to an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] In practical applications, in order to achieve high-quality energy interaction between the three-phase VIENNA rectifier and the power grid, a dual-loop control structure combining an outer voltage loop and an inner current loop is usually adopted in engineering: by detecting the DC bus voltage and comparing it with the bus voltage reference value, the outer voltage loop adjusts the output current reference value; then the inner current loop adjusts the three-phase filter inductor current on the grid side according to the current reference value to control the working state of the rectifier.

[0020] However, under the condition of simultaneous grid voltage fluctuations and DC-side load changes, the traditional PI dual-loop control structure often fails to compensate for the power imbalance caused by load changes in a timely manner. The DC-side bus voltage may drop or rise significantly in a short period of time. At the same time, the current inner loop has limited ability to suppress disturbances, and the grid-side input current is prone to distortion near the zero crossing point, affecting the quality of the grid-connected current.

[0021] Based on this, please refer to Figure 1 This invention provides a composite control method for a VIENNA rectifier, comprising the following steps: The three-phase AC voltage and the three-phase filter inductor current on the grid side of the three-phase VIENNA rectifier are collected, and the coordinate transformation of the three-phase AC voltage and the three-phase filter inductor current is performed to obtain the current feedback signal.

[0022] It is understood that in this embodiment, the three-phase AC voltage and the three-phase filter inductor current on the grid side of the three-phase VIENNA rectifier are obtained by voltage and current sensors, respectively. The collected three-phase AC voltage and three-phase filter inductor current signals are processed by coordinate transformation, for example, synchronous rotating coordinate transformation, to convert the three-phase signals into a two-phase rotating coordinate system or other equivalent coordinate system, thereby forming a current feedback signal for subsequent control calculations, which is convenient for the current inner loop active disturbance rejection controller to process uniformly.

[0023] The DC-side bus voltage, DC-side bus voltage reference value, and DC-side load current of the three-phase VIENNA rectifier are obtained. The difference between the DC-side bus voltage and the DC-side bus voltage reference value is calculated and proportional-integral operation is performed by the voltage outer loop proportional-integral regulator to obtain the voltage outer loop regulating current. The DC-side load current is fed forward by the load current feedforward unit to obtain the feedforward compensation current. The voltage outer loop regulating current and the feedforward compensation current are superimposed by addition operation to obtain the current reference signal.

[0024] As can be understood, in this embodiment, the DC-side bus voltage is obtained through a DC voltage detection unit, and a reference value for the DC-side bus voltage is given by a host controller or a preset strategy. Simultaneously, the DC-side load current is obtained through a current detection unit. The voltage outer-loop proportional-integral regulator performs proportional-integral calculations based on the difference between the DC-side bus voltage and the reference value to generate the voltage outer-loop regulating current. The load current feedforward unit performs feedforward calculations based on the change or trend of the DC-side load current to generate a feedforward compensation current. Then, the voltage outer-loop regulating current and the feedforward compensation current are superimposed through addition to obtain a current reference signal, thus balancing the bus voltage regulation requirements with the power disturbances caused by load changes.

[0025] The voltage control signal is obtained by performing error signal calculation, state observation operation, and active disturbance rejection adjustment operation on the current feedback signal and current reference signal through the current inner loop active disturbance rejection controller.

[0026] It is understood that in this embodiment, the inner-loop active disturbance rejection controller can calculate the current error signal based on the current reference signal and the current feedback signal, and on this basis, construct an extended state observation structure to perform state observation calculations on the rectifier current state and disturbances introduced by grid fluctuations, load changes, etc., to obtain disturbance-related quantities for compensation. Subsequently, the active disturbance rejection regulation section performs comprehensive regulation calculations based on the current error signal and disturbance observation results, and outputs a voltage control signal for controlling the modulation voltage of the VIENNA rectifier, so that it can still maintain good current tracking performance and dynamic response characteristics under grid voltage fluctuations and load abrupt changes.

[0027] The voltage control signal is modulated by the pulse width modulation unit to obtain the three-phase switch drive signal, and the three-phase VIENNA rectifier power switch is controlled based on the three-phase switch drive signal.

[0028] As can be understood, in this embodiment, the pulse width modulation unit generates a modulation waveform based on the voltage control signal and compares it with a preset carrier signal to obtain the three-phase switch drive signals corresponding to each arm of the three-phase VIENNA rectifier. These three-phase switch drive signals are used to drive the power switches in the three-phase VIENNA rectifier to turn on or off, thereby forming the desired voltage and current waveforms on the grid side and maintaining a predetermined bus voltage output on the DC side, thus achieving comprehensive control of the rectifier.

[0029] In summary, this embodiment of the invention collects three-phase AC voltage and three-phase filter inductor current on the grid side and performs coordinate transformation. Combined with DC bus voltage and load current information, it constructs a composite outer loop that combines voltage outer loop proportional-integral regulation with load current feedforward compensation to generate a current reference signal. Then, it uses an inner loop active disturbance rejection controller to coordinate and control the current feedback signal and the current reference signal, outputting a voltage control signal. A pulse width modulation unit generates a three-phase switch drive signal to drive the VIENNA rectifier power switch tubes. This enables the dynamic stability of the DC bus voltage and the waveform quality of the grid-side input current to be balanced under load changes and grid fluctuations, such as in electric vehicle charging devices and communication power supplies.

[0030] In some embodiments, based on the above embodiments, please refer to Figure 2 The process of acquiring the three-phase AC voltage and the three-phase filter inductor current on the grid side of the three-phase VIENNA rectifier, and performing coordinate transformation on the three-phase AC voltage and the three-phase filter inductor current to obtain the current feedback signal includes: The three-phase AC voltage on the grid side and the three-phase filter inductor current on the grid side of the three-phase VIENNA rectifier are sent to the signal acquisition unit for sampling and calculation, and the three-phase AC voltage sampling signal and the three-phase filter inductor current sampling signal are output.

[0031] It is understood that the signal acquisition unit includes a voltage sensor connected to the three-phase AC voltage on the grid side, a current sensor connected to the three-phase filter inductor on the grid side, and an analog-to-digital converter module connected to the controller. The signal acquisition unit discretely samples the continuous-time three-phase AC voltage and three-phase filter inductor current according to a preset sampling period, converting the continuous-time signal into discrete-time three-phase AC voltage sampling signals and three-phase filter inductor current sampling signals, so that subsequent digital control algorithms can be executed uniformly in the discrete-time domain. To facilitate understanding of the sampling operation by those skilled in the art, the sampling time and sampled value are characterized by the following mathematical expression:

[0032] ; ; ; ; ; ; ; in, Indicates the sampling index The sampling time is below. This represents a sample index in non-negative integer form, starting from zero. This indicates the sampling period time interval of the signal acquisition unit. , , These represent the continuous-time voltage waveforms of phase A, phase B, and phase C in the three-phase AC voltage on the grid side, respectively. , , These represent the continuous-time current waveforms of phase A, phase B, and phase C currents in the three-phase filter inductor current on the grid side, respectively. , , These represent the sampling indexes respectively. The sampled values ​​of phase A, phase B, and phase C voltages in the three-phase AC voltage sampling signal obtained at each time step. , , These represent the sampling indexes respectively. The sampled values ​​of phase A current, phase B current, and phase C current in the three-phase filtered inductor current sampling signal obtained at any time can be clearly distinguished from continuous-time physical quantities and discrete-time sampling signals through the above definition, avoiding ambiguity in the implementation process.

[0033] The three-phase AC voltage sampling signal is sent to the synchronization signal extraction unit for synchronization signal calculation and outputs the power grid synchronization signal. The three-phase filter inductor current sampling signal and the power grid synchronization signal are sent to the coordinate transformation unit for coordinate transformation and output the current feedback signal.

[0034] For example, the synchronization signal extraction unit uses a phase-locked loop (PLL) structure to process the three-phase AC voltage sampling signal, thereby obtaining a grid synchronization signal reflecting the instantaneous phase and angular frequency of the grid voltage. The PLL consists of a phase comparison module, a loop filtering module, and a numerically controlled oscillator module in sequence. The phase comparison module generates a phase-locked error signal based on the phase difference between the three-phase AC voltage sampling signal and the internal reference signal. The loop filtering module performs proportional-integral filtering on the phase-locked error signal. The numerically controlled oscillator module outputs a synchronization angular frequency signal and a phase signal consistent with the grid voltage frequency based on the filtered control quantity. To more clearly characterize the mathematical meaning of the grid synchronization signal, the grid phase signal and angular frequency signal output by the PLL are represented as follows: ; ; in, Indicates the time variable The power grid synchronization phase signal obtained from the phase-locked loop. This represents the initial grid synchronization phase at the start of time. Indicates the time variable The power grid synchronization angular frequency signal obtained by the lower phase-locked loop estimation. This represents the time independent variable in integration operations. This represents the rated angular frequency constant of the power grid selected during the design of the phase-locked loop. This represents the proportional coefficient parameter in the phase-locked loop filter module. This represents the integral coefficient parameter in the phase-locked loop filter module. Indicates the time variable The phase-locked error signal calculated by the phase comparison module can be seen from the above mathematical relationship as being jointly determined by the phase signal obtained by integrating the angular frequency signal with time and the angular frequency correction obtained by proportional-integral adjustment of the error signal.

[0035] After obtaining the grid synchronization signal, the coordinate transformation unit first performs a two-phase equivalent transformation in the stationary coordinate system on the three-phase filtered inductor current sampling signal, and then uses the phase information in the grid synchronization signal to complete the transformation from stationary coordinates to synchronous rotating coordinates, thereby obtaining a current feedback signal with the same frequency and phase as the grid voltage. The two-phase signal in the stationary coordinate system can be obtained by the following Clarke transformation: ; ; Subsequently, the current components in the synchronously rotating coordinate system can be calculated using the following Park transformation: ; ; in, Indicates the time variable The following is obtained by transforming the three-phase filter inductor current in the stationary coordinate system. Axis current components, Indicates the time variable The following is obtained by transforming the three-phase filter inductor current in the stationary coordinate system. Axis current components, Indicates the time variable Lower edge synchronous rotating coordinate system Current component in the axial direction, Indicates the time variable Lower edge synchronous rotating coordinate system Current component in the axial direction, and These represent the cosine and sine function values, respectively, with the grid synchronization phase signal as the independent variable.

[0036] Furthermore, the current feedback signal is defined as being generated by... Axis current components and Current vector composed of axial current components: ; in, Indicates the time variable The following is from Axis current components and The current feedback signal, which is a binary column vector composed of the shaft current components, can be represented in the same synchronous rotating coordinate system as the current reference signal obtained from the voltage outer loop and the feedforward unit in the subsequent steps, as defined above. This facilitates error signal calculation and state observation operations in the current inner loop active disturbance rejection controller.

[0037] In summary, in this embodiment, by setting up a signal acquisition unit, a synchronization signal extraction unit, and a coordinate transformation unit, and combining sampling operations, phase-locked loop operations, and coordinate transformation operations from three-phase stationary coordinates to synchronous rotating coordinates, the three-phase AC voltage and three-phase filter inductor current on the grid side are uniformly converted into current feedback signals represented in the synchronous rotating coordinate system. These current feedback signals are input into the subsequent voltage outer loop proportional-integral regulator and current inner loop active disturbance rejection controller in a clearly defined discrete-time mathematical form.

[0038] In some embodiments, based on the above embodiments, please refer to Figure 3The process involves acquiring the DC-side bus voltage, DC-side bus voltage reference value, and DC-side load current of the three-phase VIENNA rectifier; calculating the difference between the DC-side bus voltage and the DC-side bus voltage reference value using a voltage outer loop proportional-integral regulator and performing proportional-integral operations to obtain the voltage outer loop regulating current; performing feedforward operations on the DC-side load current using a load current feedforward unit to obtain a feedforward compensation current; and superimposing the voltage outer loop regulating current and the feedforward compensation current using an addition operation to obtain a current reference signal, including: The DC bus voltage and DC bus voltage reference value of the three-phase VIENNA rectifier are obtained. The difference between the DC bus voltage and the DC bus voltage reference value are calculated by the difference calculation unit, and the bus voltage error signal is output. The bus voltage error signal is sent to the voltage outer loop proportional-integral regulator, and the voltage outer loop regulating current is output.

[0039] It can be understood that the DC-side bus voltage is discretely sampled by the DC-side voltage sampling module, and a reference value for the DC-side bus voltage is provided by the upper-level control system or preset configuration parameters. The difference calculation unit performs a point-by-point subtraction operation on the two to obtain the bus voltage error signal. Then, the voltage outer loop proportional-integral regulator performs proportional-integral operation on the bus voltage error signal to obtain the voltage outer loop regulating current, which is used to subsequently superimpose with the feedforward compensation current to generate a current reference signal. To clarify the mathematical meaning of the difference calculation and proportional-integral operation for those skilled in the art, the above processing can be described in discrete-time form:

[0040] ; ; ; ; ; in, This represents a sample index in non-negative integer form, starting from zero. Indicates the sampling index The unlimited bus voltage error signal calculated at each moment. Indicates the sampling index Discrete-time representation of the DC-side bus voltage reference value obtained at time t. Indicates the sampling index Discrete-time representation of the DC-side bus voltage obtained from the voltage sampling module at any given time. Indicates the sampling index The limiting bus voltage error signal after being processed by the error signal limiting unit at any given time. This represents the preset lower limit value of the error signal. This represents the preset upper limit value of the error signal. Indicates the sampling index The proportional current component output by the voltage outer loop proportional calculation unit at any given time. This represents the proportional coefficient parameter of the voltage outer loop proportional calculation unit. Indicates the sampling index The integral current component output by the outer loop voltage integration unit at any given time. Indicates the sampling index Historical values ​​of the integral current component at time t. This represents the integration coefficient parameter of the voltage outer loop integration unit. This indicates the sampling period time interval of the digital control system. Indicates the sampling index The voltage outer loop regulation current, which is constantly output by the voltage outer loop proportional-integral regulator, can be more clearly defined in terms of the formal description of the above difference calculation, amplitude limiting operation, and proportional-integral operation. This makes the construction process and signal flow of the voltage outer loop clearer.

[0041] In some embodiments, to facilitate engineering implementation and parameter tuning, the voltage outer loop proportional-integral regulator can be regarded as a control model that needs to be constructed through a parameter tuning process. For a given DC bus voltage reference value sequence and load variation conditions, the DC bus voltage response curve is recorded by combining a simulation model or experimental platform, and the following performance index function is constructed: ; in, This represents the sum of squares of voltage deviation, a metric used to evaluate the performance of the outer loop voltage control. This represents the total number of sampling points selected during the offline evaluation phase. The proportional coefficient parameter was repeatedly adjusted while meeting engineering constraints such as overshoot and settling time. and integral coefficient parameters To improve performance indicators Minimizing this can be viewed as performing an offline training and tuning process on the voltage outer loop proportional-integral regulator, thereby obtaining control parameters suitable for the target rectifier and target application scenario.

[0042] The DC-side load current of the three-phase VIENNA rectifier is obtained, and the DC-side load current is sent to the load current feedforward unit for feedforward calculation, and the feedforward compensation current is output.

[0043] For example, the DC-side load current is sampled in real time by a DC-side current sampling module. The obtained DC-side load current sample value is used as the input of the load current feedforward unit. The load current feedforward unit filters and adjusts the gain of the DC-side load current to obtain the feedforward compensation current used to compensate for the impact of load power changes on the DC-side bus voltage. To improve the clarity of the load current feedforward calculation, a first-order discrete low-pass filter structure can be used to filter the DC-side load current, and the filtered load current can be linearly amplified or reduced based on a single gain coefficient. Its mathematical expression can be:

[0044] ; ; ; in, Indicates the sampling index The discrete-time representation of the DC-side load current obtained from the DC-side current sampling module at any given time. Indicates the sampling index The original DC-side load current sample value obtained at each moment is... Indicates the sampling index The filtered load current after being processed by the load current filtering unit at all times. Indicates the sampling index Historical value of filtered load current at any given time. This represents the first-order discrete low-pass filter coefficient of the load current filter unit. This filter coefficient determines the degree of suppression of high-frequency components and the tracking speed of dynamic components. Indicates the sampling index The feedforward compensation current is constantly output by the load current gain adjustment unit. This represents the current feedforward gain coefficient of the load current gain adjustment unit. Through the above filtering and gain adjustment steps, the load current feedforward unit can suppress measurement noise while retaining the low-frequency variation trend of the load current, providing a quantitative basis for active compensation of the DC bus voltage.

[0045] In some embodiments, to make the parameter setting of the load current feedforward unit have a repeatable engineering process, the filter coefficient parameters can be... With gain coefficient parameter The selection process is analogous to the steps of offline tuning of the feedforward model. For example, given multiple sets of load step change conditions, the DC bus voltage waveform is recorded through simulation or experiment, and the following performance evaluation index is constructed accordingly: ; in, This represents the sum of squares of the bus voltage deviation, a metric used to measure the effectiveness of load current feedforward compensation. This represents the total number of sampling points selected in the load step test. This represents the target value of the DC-side bus voltage set during the load step test, which is achieved by changing the filter coefficient parameters. and gain coefficient parameters Repeated calculation of indicators under multiple load step conditions Choose to make the indicator The parameter combination that is relatively small and whose bus voltage response curve overshoot and oscillation degree meet the engineering constraints can be regarded as a training and tuning process based on experimental data for the key parameters of the load current feedforward unit.

[0046] The voltage outer loop regulating current and the feedforward compensation current are fed into the addition unit, and the voltage outer loop regulating current and the feedforward compensation current are superimposed through addition operation to output a current reference signal.

[0047] It can be understood that the addition unit includes a current superposition unit and a current reference limiting unit. The current superposition unit performs a sample-by-sample addition operation on the voltage outer loop regulation current from the voltage outer loop proportional-integral regulator and the feedforward compensation current from the load current feedforward unit to obtain a current superposition signal. The current reference limiting unit then performs amplitude limiting processing on the current superposition signal according to preset upper and lower current limits, compressing the current superposition signal exceeding the limit range to the allowable range, thereby outputting a current reference signal that meets the current capability of the power device and the system safety constraints. To mathematically characterize the current superposition operation and limiting processing, the following discrete-time relationship is given:

[0048] ; ; in, Indicates the sampling index The current superposition signal output by the current superposition unit at all times. Indicates the sampling index The current reference signal output by the current reference limiting unit at all times. This represents the preset lower limit value of the current reference signal. This indicates the preset upper limit value of the current reference signal. Indicates the sampling index The voltage outer loop regulating current output by the voltage outer loop proportional-integral regulator at any given time is indicated by the symbol, which is consistent with the definition given above. Indicates the sampling index The feedforward compensation current output by the load current feedforward unit at any given time is represented by the same symbol as defined above. By providing a formal description of the addition and limiting operations described above, it can be clarified that the current reference signal is a superposition result jointly determined by the feedback channel and the feedforward channel, under the premise of satisfying the system current constraints. This avoids misunderstandings regarding the source and range of the current reference signal during engineering implementation.

[0049] In some embodiments, based on the above embodiments, the voltage outer loop proportional-integral regulator includes an error signal limiting unit, a proportional operation unit, and an integral operation unit. The error signal limiting unit performs amplitude limiting processing on the bus voltage error signal and outputs a limited error signal. The proportional operation unit performs proportional operation on the limited error signal and outputs a proportional current component. The integral operation unit performs integral operation on the limited error signal and outputs an integral current component. The proportional current component and the integral current component are added together by an addition operation to output the voltage outer loop regulating current.

[0050] For example, regarding the structure of the aforementioned voltage outer loop proportional-integral regulator, in implementation, the error signal limiting unit can be configured as a hard limiting module based on upper and lower threshold values. When the absolute value of the bus voltage error signal is too large, the limiting operation prevents the proportional current component and integral current component from becoming instantaneously too large, thereby protecting the downstream circuits and internal variables of the controller from saturation distortion. The proportional operation unit directly multiplies the limiting error signal by the proportional coefficient parameter to generate the proportional current component, while the integral operation unit performs discrete integration on the limiting error signal to generate the integral current component. Finally, the voltage outer loop regulating current is obtained by superimposing the components through the addition operation module. The calculation process has been carried out using the aforementioned formula. , , as well as Provided.

[0051] In some embodiments, based on the above embodiments, the load current feedforward unit includes a load current filtering unit and a load current gain adjustment unit. The load current filtering unit performs filtering calculations on the DC-side load current and outputs a filtered load current. The load current gain adjustment unit performs gain adjustment calculations on the filtered load current and outputs a feedforward compensation current.

[0052] For example, regarding the structure of the above-mentioned load current feedforward unit, in engineering implementation, the load current filtering unit can be constructed as a first-order digital low-pass filter module, and its calculation relationship has been obtained through... The updated formula is given, and the load current gain adjustment unit is constructed as a single-input, single-output linear proportional module. Its calculation relationship has been established through... The expression is given. This is achieved by adjusting the filter coefficient parameters. The selection of the gain coefficient parameter can be a trade-off between filtering out load current measurement noise and preserving the load current variation trend. The selection of the filter unit and the gain adjustment unit can be a compromise between the feedforward compensation to offset the load power disturbance in advance and the avoidance of oscillation introduced by over-compensation. This embodiment clearly describes the functional division and calculation relationship of the filter unit and the gain adjustment unit, which is helpful for those skilled in the art to make targeted parameter tuning under different DC load types and different power grid supply conditions.

[0053] In some embodiments, based on the above embodiments, the addition unit includes a current superposition unit and a current reference limiting unit. The current superposition unit performs an addition operation on the voltage outer loop regulation current and the feedforward compensation current to output a current superposition signal. The current reference limiting unit limits the current superposition signal according to a preset upper current limit value and a preset lower current limit value to output a current reference signal.

[0054] For example, in the implementation of the above addition unit, the current superposition unit can be configured to perform a simple scalar addition of the input voltage outer loop regulation current and feedforward compensation current at each sampling time. The calculation relationship has already been established through... The expression is explained, setting the current reference limiting unit as a limiting module based on preset upper and lower current limits. Its calculation relationship has been demonstrated through... The expression is explained. A current reference upper limit value is introduced in the specification. and current reference lower limit This clearly demonstrates that the current reference signal is not only determined by the control algorithm, but is also subject to the combined constraints of the rated current of the power devices and system safety constraints, thus making the physical meaning and engineering implementation boundaries of the current reference signal clearer.

[0055] In some embodiments, to ensure stable dynamic performance and convergence speed of the voltage outer loop and load current feedforward unit under different operating conditions, the value range of each weighting coefficient is constrained. The value ranges of the proportional and integral coefficient parameters in the voltage outer loop proportional-integral regulator can be defined as follows:

[0056] ; ; in, This represents the proportional coefficient parameter of the voltage outer loop proportional calculation unit. The integral coefficient parameters of the voltage outer loop integral operation unit are represented by... and By limiting the positive numbers to the above range, the steady-state error and dynamic response speed of the DC bus voltage can be balanced, and the output current of the proportional-integral regulator can be avoided from being excessively amplified when the bus voltage deviates significantly.

[0057] The range of values ​​for the filter coefficient and feedforward gain coefficient parameters in the load current feedforward unit can be limited as follows: ; ; in, This represents the first-order discrete low-pass filter coefficient of the load current filter unit. This represents the current feedforward gain coefficient of the load current gain adjustment unit, which is achieved by... Limiting the value between 0 and 1 ensures causal stability of the filter unit and achieves a trade-off between noise suppression and dynamic tracking. Limiting the feedforward compensation current to a finite positive range can prevent excessive feedforward compensation current from causing bus voltage oscillation.

[0058] In summary, this embodiment provides a detailed explanation of the processing procedures for DC-side bus voltage and DC-side load current. By constructing a composite current reference generation structure consisting of a difference calculation unit, a voltage outer loop proportional-integral regulator, a load current feedforward unit, and an addition unit, and combining a series of clearly defined mathematical operations such as discrete-time error signal calculation, proportional-integral operation, load current filtering and gain adjustment, current superposition and limiting, the synergistic relationship between the voltage outer loop and the load feedforward, as well as the formation mechanism of the current reference signal, are clearly presented in the specification. This provides a complete and reproducible input signal generation link for the error signal calculation and state observation operation of the current inner loop active disturbance rejection controller.

[0059] In some embodiments, based on the above embodiments, please refer to Figure 4 The step of performing error signal calculation, state observation operation, and active disturbance rejection adjustment operation on the current feedback signal and current reference signal through the current inner loop active disturbance rejection controller to obtain the voltage control signal includes: The current reference signal and the current feedback signal are sent to the current reference tracking unit, and dynamic shaping operations are performed on the current reference signal and the current feedback signal to output the current reference tracking signal.

[0060] The historical values ​​of the current feedback signal and the voltage control signal are sent to the extended state observation unit, and the historical values ​​of the current feedback signal and the voltage control signal are jointly observed and calculated to output the current observation signal and the disturbance estimation signal.

[0061] The current reference tracking signal, the current observation signal, and the disturbance estimation signal are sent to the state error feedback adjustment unit. Error signal calculation is performed on the current reference tracking signal and the current observation signal, and disturbance compensation calculation is performed based on the disturbance estimation signal to output the voltage control signal.

[0062] For example, the current inner-loop active disturbance rejection controller is considered as a composite control structure consisting of a current reference tracking unit, an extended state observation unit, and a state error feedback adjustment unit connected in series and parallel. The current reference tracking unit dynamically shapes the current reference signal to generate a smooth current reference tracking signal that adapts to load changes. The extended state observation unit constructs a discrete extended state observation model based on historical values ​​of the current feedback signal and the voltage control signal, jointly estimating the current state and the total disturbance. The state error feedback adjustment unit generates the voltage control signal based on the difference between the current reference tracking signal and the current observation signal, as well as the disturbance estimation signal. To facilitate understanding of the modeling concept of the current inner-loop active disturbance rejection controller by those skilled in the art, the current dynamics of the controlled object in the synchronous rotating coordinate system are approximated by the following discrete-time equation:

[0063] ; in, Indicates the sampling index Time along synchronous rotating coordinate system Current feedback component in the axial direction, symbol Indicates the sampling index Time along synchronous rotating coordinate system Current feedback component in the axial direction, symbol This indicates the sampling period time interval of the digital control system. This represents the first-order dynamic coefficient of the current obtained by equating the grid-side inductance of the three-phase VIENNA rectifier to a synchronous rotating coordinate system. This represents the equivalent amplification factor of the voltage control signal to the change in current. Indicates the sampling index The voltage control signal is constantly output by the state error feedback adjustment unit. Indicates the sampling index The total disturbance term constantly acts on the current path, which comprehensively represents factors such as grid voltage fluctuations, load changes, parameter uncertainties, and unmodeled dynamics. By representing the current dynamics as the sum of the known nominal part and the unknown disturbance part, the extended state observation unit can estimate the unknown disturbance part online, and the state error feedback adjustment unit uses the disturbance estimation signal for compensation when generating the voltage control signal, thus forming a complete inner-loop active disturbance rejection control closed loop for the current.

[0064] In some embodiments, based on the above embodiments, the current reference tracking unit includes a reference limiting unit, a dynamic weighting unit, and a tracking calculation unit; the reference limiting unit performs limiting processing on the current reference signal to output a limited current reference signal; the dynamic weighting unit performs weight adjustment calculation on the limited current reference signal based on the current feedback signal to output a weighted current reference signal; and the tracking calculation unit performs tracking calculation on the weighted current reference signal to output a current reference tracking signal.

[0065] For example, in the current reference tracking unit described above, the current reference signal is regarded as the aforementioned current reference limiting signal. The reference limiting unit first limits the original current reference signal according to preset upper and lower current reference limits. The dynamic weighting unit then adaptively adjusts the reference weights based on the deviation between the current feedback signal and the limited current reference signal. Finally, the tracking operation unit generates a smooth current reference tracking signal using a first-order discrete tracking structure. The operations of the reference limiting unit and the dynamic weighting unit can be mathematically described using the following relationship:

[0066] ; ; ; ; ; in, Indicates the sampling index The original current reference signal at time t is discretely represented. Indicates the sampling index The limiting current reference signal after being processed by the reference limiting unit at any given time. This represents the preset lower limit value of the current reference signal. This indicates the preset upper limit value of the current reference signal. Indicates the sampling index The current reference tracking error signal is calculated by the dynamic weighting unit at any given time. Indicates the sampling index Time along synchronous rotating coordinate system The current feedback component in the axial direction, the sign of which is consistent with the definition in the aforementioned current dynamic equation. Indicates the sampling index The reference weight coefficients output by the dynamic weighting unit at all times. This represents the dynamic weighting strength coefficient, which determines the degree to which the magnitude of the error signal affects the rate of change of the weights. Indicates the sampling index The absolute value of the current reference tracking error signal at any given time. Indicates the sampling index The weighted current reference signal is output by the dynamic weighting unit at all times.

[0067] The tracking operation unit can be constructed as a first-order discrete low-pass tracking structure to filter and dynamically track the weighted current reference signal. Its calculation relationship can be expressed as follows: ; in, Indicates the sampling index The current reference tracking signal is constantly output by the tracking calculation unit. Indicates the sampling index The current reference tracking signal historical value at any given time. This represents the first-order discrete tracking coefficient of the tracking operation unit. Adjusting this coefficient allows for a balance between tracking speed and smoothness.

[0068] To improve implementation consistency, different load variation conditions and current reference step signals are selected during the offline phase, and the following performance index function is constructed for tuning the parameters of the current reference tracking unit: ; in, This represents the sum of squared errors index used to evaluate the performance of current reference tracking. This indicates the total number of sampling points selected during the offline evaluation phase. Indicates the sampling index The desired current reference tracking target value is achieved by adjusting parameters while meeting the requirements for transient current overshoot and steady-state error. and To improve performance indicators To minimize this, it is considered as a process of building and training the current reference tracking unit based on sample data.

[0069] In some embodiments, based on the above embodiments, the extended state observation unit includes a current state estimation unit and a disturbance estimation unit; the current state estimation unit performs state estimation calculations on the historical values ​​of the current feedback signal and the voltage control signal, and outputs a current observation signal; the disturbance estimation unit performs disturbance estimation calculations on the current feedback signal and the current observation signal, and outputs a disturbance estimation signal.

[0070] For example, in the above-mentioned extended state observation unit, a discrete extended state observer structure is used to jointly estimate the current state and the total disturbance, unifying the current state estimation unit and the disturbance estimation unit into a discrete third-order state observer. The observer state vector can be defined as:

[0071] ; in, Indicates the sampling index At any given time, the state vector of the state observer is expanded. Indicates the sampling index The observed state variables used to estimate the current state at any given time. Indicates the sampling index The observed state variables used to estimate the rate of change of current at any given time. Indicates the sampling index The time is used to estimate the observed state quantities of the total disturbance.

[0072] The update relation of the extended state observer is represented as follows: ; ; ; ; in, Indicates the sampling index The observation error signal calculated by the extended state observation unit at any given time is the difference between the actual current feedback component and the observed current state. This represents the first observation gain parameter of the extended state observer. This represents the second observation gain parameter of the extended state observer. This represents the third observation gain parameter of the extended state observer. Indicates the sampling index The historical value of the voltage control signal input to the extended state observation unit at any given time can be selected as the sampling index. Voltage control signal output at all times This symbol is the same as the control input coefficient in the aforementioned current dynamic equation. Used in conjunction to characterize the effect of control inputs on the internal state of the controlled object.

[0073] The current observation signal and the disturbance estimation signal are defined as follows: ; ; in, Indicates the sampling index The current observation signal output by the current state estimation unit at any given time. Indicates the sampling index The disturbance estimation signal output by the disturbance estimation unit at any given time. To improve the design repeatability of the extended state observation unit, the observer bandwidth target is determined based on the nominal model of the controlled object during the offline phase, and the observation gain parameters are configured. , , To ensure that the eigenvalues ​​of the extended state observer satisfy a predetermined convergence rate requirement in the discrete domain, the following performance index function can be constructed to evaluate the estimation performance of the extended state observer unit:

[0074] ; in, This represents a comprehensive index value used to evaluate the performance of the extended state observation unit. This represents the total number of sampling points selected in the offline simulation or experiment. This represents the non-negative weighting coefficient used to balance the current observation error term and the disturbance estimation amplitude term. This is achieved by adjusting the observation gain parameter... , , Perform searches and adjustments to improve performance metrics. Meeting and minimizing the preset constraints can be viewed as an offline construction and training process for the structure and parameters of the extended state observation unit.

[0075] In some embodiments, based on the above embodiments, the state error feedback adjustment unit includes an error signal calculation unit, a disturbance compensation unit, and a voltage control generation unit; the error signal calculation unit performs difference calculation on the current reference tracking signal and the current observation signal to output a basic error signal; the disturbance compensation unit performs compensation calculation on the basic error signal and the disturbance estimation signal to output a compensated error signal; and the voltage control generation unit performs feedback calculation and amplitude limiting processing on the compensated error signal to output a voltage control signal.

[0076] For example, in the aforementioned state error feedback adjustment unit, the basic error signal between the current reference tracking signal and the current observation signal is obtained by the error signal calculation unit. Then, the disturbance compensation unit combines this error signal with the disturbance estimation signal to generate a compensation error signal. Finally, the voltage control generation unit performs proportional-integral feedback calculations on the compensation error signal and applies amplitude limiting constraints, thereby outputting a voltage control signal that meets the voltage capability and modulation range requirements of the power device. The error signal calculation and disturbance compensation process can be mathematically described by the following relationship:

[0077] ; ; in, Indicates the sampling index The basic error signal output by the error signal calculation unit at any given time. Indicates the sampling index The current reference tracking signal output by the current reference tracking unit at all times, the symbol of which is consistent with the definition in the aforementioned tracking calculation formula. Indicates the sampling index The current observation signal output by the current state estimation unit at any given time, the symbol of which is consistent with the definition in the aforementioned extended state observation unit. Indicates the sampling index The compensation error signal output by the disturbance compensation unit at all times. The disturbance compensation coefficient parameter in the disturbance compensation unit determines the proportion of the disturbance estimation signal in the compensation error signal. Indicates the sampling index The disturbance estimation signal output by the disturbance estimation unit at any given time.

[0078] The voltage control generation unit is constructed as a proportional-integral control structure with a limiting mechanism, and its calculation relationship is expressed as follows: ; ; ; ; in, Indicates the sampling index The proportional control component is constantly output by the proportional calculation section in the voltage control generation unit. This represents the inner loop proportional control coefficient parameter in the state error feedback control unit. Indicates the sampling index The integral control component is output by the integral calculation section in the voltage control generation unit at all times. Indicates the sampling index Historical value of integral control component at time step. This represents the inner-loop integral control coefficient parameter in the state error feedback control unit. Indicates the sampling index The intermediate signal for unlimited voltage control is obtained by superimposing the proportional and integral components at any given time. Indicates the sampling index The final voltage control signal after amplitude limiting is defined in the aforementioned dynamic equation of the controlled object's current, and its symbol is consistent with that of the control input. This indicates the preset lower limit value of the voltage control signal. This represents the preset upper limit value of the voltage control signal. To provide a repeatable engineering method for selecting parameters of the state error feedback regulation unit, the following performance index function is constructed using simulation or experimental data under multiple current reference step and grid voltage disturbance conditions:

[0079] ; in, This represents the index value used to evaluate the overall performance of the current inner loop. This indicates the total number of sampling points selected during the evaluation. This represents the weighting coefficient used to balance current tracking error and control signal amplitude. The coefficient is adjusted to meet constraints such as current overshoot, current harmonics, and control signal limiting. , and disturbance compensation coefficient To improve performance indicators Minimizing it as much as possible can be regarded as a systematic parameter tuning and training process for the state error feedback adjustment unit.

[0080] In some embodiments, to ensure that the current inner-loop active disturbance rejection controller balances the smoothness of the current reference signal and its fast tracking capability, the value ranges of the dynamic weighting strength coefficients and tracking operation coefficients of the current reference tracking unit are constrained. The dynamic weighting strength coefficient parameters and the first-order tracking coefficient parameters can be limited as follows:

[0081] ; ; in, This represents the dynamic weighting intensity coefficient in the dynamic weighting unit. The first-order discrete tracking coefficients of the tracking operation unit are represented by the above range constraints. This ensures that when the current reference signal undergoes a step change, the dynamic weighting unit can adaptively adjust the weights according to the error magnitude, and the tracking operation unit can approach the target reference in a stable manner, avoiding oscillations or excessive overshoot during the tracking process.

[0082] In some embodiments, to ensure that the extended state observation unit has sufficient disturbance estimation bandwidth under different operating conditions without introducing excessive noise amplification, the range of the observation gain parameter and the weighting coefficients in the performance indicators of the extended state observation unit is limited. The observation gain parameter can be limited as follows:

[0083] ; ; ; in, , , Let represent the first, second, and third observation gain parameters of the extended state observer, respectively. By limiting these three parameters to large positive upper bounds, a sufficiently large observation bandwidth can be provided while ensuring that the discrete domain poles are located inside the unit circle, thereby accelerating the convergence speed of the current observation signal and the perturbation estimation signal. The perturbation estimation weight coefficient in the performance index of the extended state observer unit can be limited to the following range:

[0084] ; in, The non-negative weighting coefficients used to balance the current observation error term and the disturbance estimation magnitude term can be used to make a trade-off between the speed of disturbance estimation and the ability to suppress noise through the above range constraints.

[0085] In some embodiments, to improve the current tracking accuracy of the state error feedback control unit and suppress excessive fluctuations in the control signal, range constraints are imposed on the disturbance compensation coefficient parameter, the current inner loop proportional-integral coefficient parameter, and the weighting coefficients in the comprehensive performance index. The disturbance compensation coefficient parameter can be limited as follows:

[0086] ; in, This represents the disturbance compensation coefficient parameter in the disturbance compensation unit, which is obtained by... Limiting the value between 0 and 2 can prevent the disturbance estimation signal from being excessively amplified in the compensation channel, thus maintaining system stability while compensating for external disturbances in the current channel. The proportional-integral coefficient parameter for the inner current loop can be limited to:

[0087] ; ; in, This represents the inner loop proportional control coefficient parameter in the state error feedback control unit. The parameters representing the integral control coefficients of the inner loop in the state error feedback adjustment unit are constrained by the aforementioned range. This ensures sufficient bandwidth and zero steady-state error capability for the current inner loop while avoiding modulation saturation problems caused by excessive proportional-integral output amplitude. The weighting coefficients in the comprehensive performance index of the current inner loop can be limited as follows:

[0088] ; in, This represents the weighting coefficient used to balance the current tracking error and the control signal amplitude. By selecting appropriate coefficients... The value can be adjusted between current ripple and switching losses depending on the specific application scenario.

[0089] In one specific embodiment, a three-phase VIENNA rectifier with a rated power of 30KW, a rated DC bus voltage of 75V, a rated grid frequency of 50Hz, and a digital control sampling frequency of 20KHz is used as the controlled object. The proportional coefficient parameter of the voltage outer loop proportional-integral regulator can be selected. The integral coefficient parameter is 1.2. The filter coefficient parameter of the load current filter unit is 150. The load current feedforward gain coefficient parameter is 0.15. The dynamic weighting strength coefficient of the current reference tracking unit is 0.8. The first-order tracking coefficient is 2.0. The observation gain parameter of the extended state observer is 0.3. for , for , for Weighting coefficients of performance index of extended state observation unit The disturbance compensation coefficient parameter is 10. The current inner loop proportional coefficient parameter is 1.0. The integral coefficient parameter is 3.5. The weighting coefficient for the comprehensive performance index of the inner current loop is 1500. With a value of 20, all the above parameter values ​​fall within the aforementioned recommended range. Through simulation and prototype experiments of this embodiment, it can be observed that under the combined conditions of the load jumping from 20% to 80% of the rated value and the grid voltage dropping by 10%, the DC bus voltage drop is significantly smaller than that of the traditional scheme using only dual-loop proportional-integral control. The zero-crossing distortion of the input current is significantly suppressed, thus verifying that under the given value range and demonstration parameter configuration, the setting of the key weight coefficients of this invention can effectively support the realization of the composite control strategy.

[0090] In summary, this embodiment subdivides the current inner-loop active disturbance rejection controller into three functional modules: a current reference tracking unit, an extended state observation unit, and a state error feedback adjustment unit. It also constructs the current dynamic equation, the extended state observer update equation, and the state error feedback and disturbance compensation control law by combining the discrete-time controlled object model. In conjunction with multiple sets of performance index functions, the key parameters are tuned and trained offline, so that the dynamic shaping of the current reference signal, the online estimation of the current state and disturbance, and the generation process of the voltage control signal all have clear mathematical expressions and parameter definitions.

[0091] In some embodiments, based on the above embodiments, please refer to Figure 5The process of modulating the voltage control signal using a pulse width modulation unit to obtain a three-phase switch drive signal, and then controlling the three-phase VIENNA rectifier power switch transistors based on the three-phase switch drive signal, includes: The voltage control signal is subjected to amplitude limiting and biasing operations by the modulation signal preprocessing unit, and the modulation signal is output.

[0092] It can be understood that the voltage control signal is regarded as a discrete time series. The voltage control signal is first limited in amplitude, then normalized and biased to obtain a modulated signal that meets the modulation range constraints, which is convenient for comparison and calculation with the carrier signal.

[0093] The operation process of the modulation signal preprocessing unit is described by the following discrete-time relationship: ; ; ; in, This represents a sample index in non-negative integer form, starting from zero. Indicates the sampling index The voltage control signal is constantly output by the state error feedback adjustment unit. Indicates the sampling index The voltage control limiting signal after the limiting calculation at any given time. This indicates the preset lower limit value of the voltage control signal. This indicates the preset upper limit value of the voltage control signal. Indicates the sampling index The intermediate modulated signal after scaling and biasing operations at each moment. This represents the scaling factor from the voltage control signal to the modulation signal. This indicates the DC bias of the modulated signal. Indicates the sampling index The modulated signal is ultimately output by the modulation signal preprocessing unit at any given time. This indicates the preset lower limit value of the modulated signal. This represents the preset upper limit value of the modulation signal. Through the above limiting and biasing operations, the voltage control signal can be uniformly mapped to the allowable operating range of the modulation signal, avoiding the problems of modulation oversaturation or insufficient modulation depth in the subsequent carrier comparison process. At the same time, it provides a preprocessing framework that can be reused by adjusting parameters for rectifiers with different rated voltages and different modulation strategies.

[0094] The carrier generation unit performs carrier generation calculations on the preset modulation frequency and outputs a carrier signal.

[0095] For example, the carrier generation unit constructs a periodic triangular wave or sawtooth wave carrier signal in the discrete time domain according to a preset modulation frequency, which is then compared with the modulation signal to form a pulse width modulation waveform. The modulation frequency can be represented in the continuous time domain as... The sampling period is expressed as Then the number of sampling points contained in one modulation period can be expressed as discrete integers:

[0096] ; Subsequently, an auxiliary sequence that monotonically increases within each modulation period can be constructed using floor and modulo operations. This auxiliary sequence can then be mapped to a discrete carrier signal that varies within the range of minus one to plus one through linear scaling. Its mathematical expression can be: ; ; in, This indicates the preset modulation frequency used by the carrier generation unit. This represents the total number of sampling points contained within a modulation period. This indicates the rounding operation. Indicates the sampling index The relative sampling position index within the current modulation period, ranging from 0 to... ,symbol This represents the floor operation, which maps a real number to the largest integer not greater than that real number. (Symbol: floor) Indicates the sampling index The carrier signal is output by the carrier generation unit at any given time. Through the above construction method, a frequency of [frequency value] can be generated in the digital control platform with a uniform sampling period. Furthermore, discrete carrier signals with a fixed amplitude range are easy to keep the modulation frequency consistent under different operating conditions and provide a standardized reference waveform for subsequent pulse width comparison.

[0097] The modulation signal and the carrier signal are compared and calculated by the pulse width comparison unit, and a three-phase switch drive signal is output. The three-phase switch drive signal is used as the control input for the three-phase VIENNA rectifier power switch.

[0098] It can be understood that the pulse width comparison unit adopts a carrier comparison type pulse width modulation structure, comparing the amplitude of the modulating signal and the carrier signal at each sampling time to obtain a switching control sequence in which the duty cycle varies between zero and one. For ease of mathematical characterization, the modulating signal mref(n) is first... m ref( nThe signal is mapped to a duty cycle reference signal, and then a step function is used to describe the comparison result. For example, the duty cycle reference signal and the single-phase switch drive signal can be defined as follows:

[0099] ; ; in, Indicates the sampling index The duty cycle reference signal, derived from the modulation signal, is theoretically limited to a range of 0 to 1. Indicates the sampling index The single-channel pulse width modulation switching signal is output by the pulse width comparison unit at all times. This represents a unit step function, outputting 1 when the input variable is greater than or equal to 0, and outputting 0 when the input variable is less than 0. For the specific implementation of the three-phase VIENNA rectifier, based on the single-channel pulse width modulation switching signal, and according to the pre-designed three-phase modulation strategy and power switch connection topology, the duty cycle reference signal and carrier comparison logic can be extended into three-way switch drive signal vectors for phases A, B, and C:

[0100] ; in, Indicates the sampling index The three-phase switch drive signal vector output at any given time, with the sign... Indicates the sampling index The switching drive signal corresponding to the A-phase power switch at any given time. Indicates the sampling index The switching drive signal corresponding to the B-phase power switch at any given time. Indicates the sampling index This corresponds to the switching drive signal of the C-phase power switch. In practical implementation, the single-phase pulse-width modulated switching signal can be used according to the topology of the three-phase VIENNA rectifier. By combining the grid synchronization phase signal and modulation strategy, three three-phase switch drive signals with a phase difference of 120 electrical angles are constructed. These three-phase switch drive signals are then used as control inputs for the power switching transistors, thereby obtaining the desired current waveform and power transmission direction on the grid side.

[0101] In summary, this embodiment introduces a modulation signal preprocessing unit, a carrier generation unit, and a pulse width comparison unit to perform amplitude limiting and biasing operations on the voltage control signal, discrete carrier generation operations on the preset modulation frequency, and comparison operations on the modulation signal and the carrier signal. This provides a complete discrete-time modulation link from the voltage control signal to the three-phase switch drive signal, and uses clear mathematical expressions to characterize the meaning of each intermediate quantity and parameter, ensuring that the power switches of the three-phase VIENNA rectifier obtain a drive signal sequence consistent with the control target.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite control method for a VIENNA rectifier, characterized in that, Includes the following steps: The three-phase AC voltage and the three-phase filter inductor current on the grid side of the three-phase VIENNA rectifier are collected, and the coordinate transformation of the three-phase AC voltage and the three-phase filter inductor current is performed to obtain the current feedback signal. The DC-side bus voltage, DC-side bus voltage reference value, and DC-side load current of the three-phase VIENNA rectifier are obtained. The difference between the DC-side bus voltage and the DC-side bus voltage reference value is calculated and proportional-integral operation is performed by the voltage outer loop proportional-integral regulator to obtain the voltage outer loop regulating current. The DC-side load current is fed forward by the load current feedforward unit to obtain the feedforward compensation current. The voltage outer loop regulating current and the feedforward compensation current are superimposed by addition operation to obtain the current reference signal. The voltage control signal is obtained by performing error signal calculation, state observation operation and active disturbance rejection adjustment operation on the current feedback signal and current reference signal through the current inner loop active disturbance rejection controller. The voltage control signal is modulated by the pulse width modulation unit to obtain the three-phase switch drive signal, and the three-phase VIENNA rectifier power switch is controlled based on the three-phase switch drive signal.

2. The VIENNA rectifier composite control method as described in claim 1, characterized in that, The process involves acquiring the DC-side bus voltage, DC-side bus voltage reference value, and DC-side load current of the three-phase VIENNA rectifier. A voltage outer-loop proportional-integral regulator calculates the difference between the DC-side bus voltage and the DC-side bus voltage reference value and performs proportional-integral operations to obtain the voltage outer-loop regulating current. A load current feedforward unit performs feedforward operations on the DC-side load current to obtain a feedforward compensation current. Finally, the voltage outer-loop regulating current and the feedforward compensation current are superimposed using an addition operation to obtain a current reference signal. This includes: The DC bus voltage and DC bus voltage reference value of the three-phase VIENNA rectifier are obtained. The difference between the DC bus voltage and the DC bus voltage reference value are calculated by the difference calculation unit, and the bus voltage error signal is output. The bus voltage error signal is sent to the voltage outer loop proportional-integral regulator, and the voltage outer loop regulating current is output. Obtain the DC-side load current of the three-phase VIENNA rectifier, send the DC-side load current to the load current feedforward unit for feedforward calculation, and output the feedforward compensation current. The voltage outer loop regulating current and the feedforward compensation current are fed into the addition unit, and the voltage outer loop regulating current and the feedforward compensation current are superimposed through addition operation to output a current reference signal.

3. The VIENNA rectifier composite control method as described in claim 2, characterized in that, The voltage outer loop proportional-integral regulator includes an error signal limiting unit, a proportional operation unit, and an integral operation unit. The error signal limiting unit limits the bus voltage error signal and outputs a limited error signal. The proportional operation unit performs proportional operation on the limited error signal and outputs a proportional current component. The integral operation unit performs integral operation on the limited error signal and outputs an integral current component. The proportional current component and the integral current component are added together by an addition operation to output the voltage outer loop regulating current.

4. The VIENNA rectifier composite control method as described in claim 2, characterized in that, The load current feedforward unit includes a load current filtering unit and a load current gain adjustment unit. The load current filtering unit performs filtering calculations on the DC-side load current and outputs a filtered load current. The load current gain adjustment unit performs gain adjustment calculations on the filtered load current and outputs a feedforward compensation current.

5. The VIENNA rectifier composite control method as described in claim 2, characterized in that, The addition unit includes a current superposition unit and a current reference limiting unit. The current superposition unit performs addition operations on the voltage outer loop regulation current and the feedforward compensation current to output a current superposition signal. The current reference limiting unit limits the current superposition signal according to a preset upper current limit value and a preset lower current limit value to output a current reference signal.

6. The VIENNA rectifier composite control method as described in claim 1, characterized in that, The process of calculating error signals, performing state observation operations, and conducting active disturbance rejection adjustment operations on the current feedback signal and the current reference signal through the current inner-loop active disturbance rejection controller to obtain the voltage control signal includes: The current reference signal and the current feedback signal are sent to the current reference tracking unit, and the current reference signal and the current feedback signal are dynamically shaped to output the current reference tracking signal. The historical values ​​of the current feedback signal and the voltage control signal are sent to the extended state observation unit, and the historical values ​​of the current feedback signal and the voltage control signal are jointly observed and calculated to output the current observation signal and the disturbance estimation signal. The current reference tracking signal, the current observation signal, and the disturbance estimation signal are sent to the state error feedback adjustment unit. Error signal calculation is performed on the current reference tracking signal and the current observation signal, and disturbance compensation calculation is performed based on the disturbance estimation signal to output the voltage control signal.

7. The VIENNA rectifier composite control method as described in claim 6, characterized in that, The current reference tracking unit includes a reference limiting unit, a dynamic weighting unit, and a tracking calculation unit; The current reference signal is limited by the reference limiting unit to output a limited current reference signal. The dynamic weighting unit performs weight adjustment calculations on the limiting current reference signal based on the current feedback signal, and outputs a weighted current reference signal. The tracking calculation unit performs tracking calculations on the weighted current reference signal and outputs a current reference tracking signal.

8. The VIENNA rectifier composite control method as described in claim 6, characterized in that, The extended state observation unit includes a current state estimation unit and a disturbance estimation unit; The current state estimation unit performs state estimation calculations on the historical values ​​of the current feedback signal and the voltage control signal, and outputs the current observation signal. The disturbance estimation unit performs disturbance estimation calculations on the current feedback signal and the current observation signal, and outputs a disturbance estimation signal.

9. The VIENNA rectifier composite control method as described in claim 6, characterized in that, The state error feedback adjustment unit includes an error signal calculation unit, a disturbance compensation unit, and a voltage control generation unit. The error signal calculation unit performs a difference calculation on the current reference tracking signal and the current observation signal, and outputs a basic error signal. The disturbance compensation unit performs compensation calculations on the basic error signal and the disturbance estimation signal, and outputs a compensated error signal. The voltage control generation unit performs feedback calculations and amplitude limiting on the compensation error signal, and outputs a voltage control signal.

10. The VIENNA rectifier composite control method as described in claim 1, characterized in that, The process of modulating the voltage control signal using a pulse width modulation unit to obtain a three-phase switch drive signal, and then controlling the three-phase VIENNA rectifier power switch transistors based on the three-phase switch drive signal, includes: The voltage control signal is subjected to amplitude limiting and biasing operations by the modulation signal preprocessing unit, and the modulation signal is output. The carrier generation unit performs carrier generation calculations on the preset modulation frequency and outputs a carrier signal. The modulation signal and the carrier signal are compared and calculated by the pulse width comparison unit, and a three-phase switch drive signal is output. The three-phase switch drive signal is used as the control input for the three-phase VIENNA rectifier power switch.

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