A grid-connected inverter predictive current control method considering inductance parameter correction

Abstract

This invention discloses a predictive current control method for grid-connected inverters that considers inductor parameter correction, relating to the field of inverter control technology. The invention includes: acquiring information such as DC-side voltage, AC-side current, and voltage of the inverter; calculating the AC-side voltage phase angle; and calculating the AC-side voltage and current... dq Shaft component; Calculate AC side current dq The method involves: setting reference values ​​for the shaft components; correcting inductor parameters; calculating the predicted AC current values ​​corresponding to the zero voltage vector and six non-zero voltage vectors; selecting the optimal voltage vector and applying it to the inverter. This method overcomes the parameter sensitivity of traditional model-based predictive current control by correcting inductor parameters online, effectively improving system robustness.

Description

Technical Field

[0001] This invention relates to the field of inverter control, and more specifically to a predictive current control method for grid-connected inverters that takes into account inductor parameter correction. Background Technology

[0002] With the accelerating pace of global energy transition, new energy power generation and related technologies have received widespread attention. New energy power generation is shifting from centralized to distributed generation, placing more stringent demands on the performance of small and medium-power grid-connected inverters. As research deepens, model predictive control (MDC) has garnered significant attention from scholars both domestically and internationally for its application in grid-connected inverters. Compared to traditional voltage-oriented control (VOC) and direct power control (DPC) algorithms, MDC offers significant advantages in dynamic response speed and multi-objective control. The key to MDC lies in predicting the system state at the next moment and selecting the optimal control input. The accuracy of the model parameters directly determines the control precision of the method. Improving the sensitivity of MDC to model parameters, thereby enhancing system robustness, has become a research hotspot for scholars worldwide. Especially for grid-connected inverters, the predictive model mainly involves two parameters: the inductance and internal resistance of the grid-side filter inductor. Comparatively, the inductance of the grid-side filter inductor has a much greater impact on control precision than its internal resistance. Summary of the Invention

[0003] Technical problem: The purpose of this invention is to provide a predictive current control method for grid-connected inverters that takes into account inductor parameter correction, so as to correct the inductor parameters in real time and improve the robustness of the system.

[0004] Technical solution: To achieve the above objectives, the present invention provides a predictive current control method considering inductor parameter correction, comprising the following steps: Step 1: Collect information on the inverter's DC side voltage, AC side three-phase current, and AC side three-phase voltage through the sensing unit; Step 2: Calculate the phase angle of the AC side voltage based on the AC side phase A voltage to provide a phase reference for the system; Step 3: Calculate the AC side voltage and AC side current based on the AC side voltage phase angle. dq Axial components; Step 4: Calculate the AC side current based on the grid-connected power reference value. dq Axis component reference values; Step 5, based on the AC side current q Shaft component reference value and AC side current q The error between the actual values ​​of the shaft components is used to correct the inductance parameters; Step 6: Using the prediction model, calculate the predicted AC side current values ​​corresponding to the zero voltage vector and the six non-zero voltage vectors. dq Axial components; Step 7: Calculate the value function based on the predicted AC current value and select the optimal voltage vector, apply its switching state to the inverter, and control the system operation.

[0005] In step 1, the three-phase current on the AC side of the inverter is acquired by a current sensor.

[0006] Step 2 involves calculating the AC side voltage phase angle, specifically including the following steps: The in-phase virtual voltage, which is in phase with the AC side phase A voltage, is calculated using a second-order generalized integrator. u α Vertical virtual voltage lagging behind the AC side A-phase voltage u β : (1) In the formula, e a This refers to the AC phase A voltage. ω g The angular frequency of the AC side voltage. k s is an adjustable coefficient, and s is a complex frequency; Calculate the phase angle of the AC side voltage using the arctangent function: (2) In the formula, θ This represents the phase angle of the grid-side voltage.

[0007] In step 3, the AC side voltage and AC side current are calculated. dq The specific method for shaft component is as follows: The AC side voltage is calculated using the following formula. dq Axis components: (3) In the formula, e d and e q For AC side voltage dq Axial components, e a , e b , e c These are the AC phase A, phase B, and phase C voltages, respectively. The AC side current is calculated using the following formula. dq Axis components: (4) In the formula, i a , i b and i c This indicates the three-phase current value on the AC side. i d and iq For AC side current dq Axial components.

[0008] In step 4, calculate the AC side current. dq The specific method for setting the shaft component reference values ​​is as follows: Based on the reference values ​​of grid-connected active and reactive power P * and Q * Calculate the AC side current dq Axis component reference values: (5) In the formula, and These are the AC side currents. dq Axis component reference values.

[0009] Step 5 involves correcting the inductor parameters, specifically including the following steps: Calculate the AC side current q Error between reference and actual values ​​of shaft components: (6) In the formula, Δ i q AC side current q Error between the reference value and the actual value of the shaft component i q For AC side current q Axial components, For AC side current q Axis component reference values; Calculate the feedback values ​​of the inductor parameters: (7) In the formula, Δ L This is the inductor parameter feedback value. k i The integral coefficient; Correct inductor parameters: (8) In the formula, This is the inductance parameter correction value. L 0 represents the initial value of the inductance parameter.

[0010] In step 6, the predicted AC side current values ​​corresponding to the zero voltage vector and the six non-zero voltage vectors are calculated. dq The specific method for shaft component is as follows: Calculate the dq-axis components of the predicted current using a current prediction model: (9) In the formula, T s The sampling period is and Voltage vectors V i The corresponding predicted current values, d-axis and q-axis components, R The internal resistance of the AC-side filter inductor, and Voltage vectors V i of d, q Axis components, subscript .

[0011] Step 7 involves selecting the optimal voltage vector, which specifically includes the following steps: Calculate the value functions corresponding to the zero voltage vector and the six non-zero voltage vectors: (10) Compare the value function values ​​and select the optimal voltage vector: (11) In the formula, V opt For the optimal voltage vector, and These are the AC side currents. d, q Axis component reference values.

[0012] The optimal voltage vector, if the optimal voltage vector is a zero vector V If 0, then by judging the applied voltage vector situation at the previous moment, further... V 0 and V Selecting the zero vector in 7: (12) In the formula, This is the voltage vector applied at the previous moment.

[0013] The switching state of the voltage vector is specifically as follows: The switch status is determined by a three-bit binary number. S a S b S c ]express, S k = 1 indicates inverter k The upper bridge arm switch is on and the lower bridge arm switch is off. k = a , b , c This refers to the abc three-phase inverter; S k = 0 indicates inverter k The upper bridge arm switch is off and the lower bridge arm switch is on; V The inverter switching state corresponding to 0 is [0 0 0]. VThe inverter switching state corresponding to 1 is [1 0 0]. V The inverter switching state corresponding to 2 is [1 1 0]. V The inverter switching state corresponding to 3 is [0 1 0]. V The inverter switching state corresponding to 4 is [0 1 1]. V The inverter switch state corresponding to 5 is [0 0 1]. V The inverter switch state corresponding to 6 is [1 0 1]. V The inverter switching state corresponding to 7 is [1 1 1].

[0014] Beneficial effects: This invention provides a predictive current control method for grid-connected inverters that takes into account inductor parameter correction, based on the AC side current. q The error between the reference value and the actual value of the shaft component is used to correct the inductance parameter in real time. The structure is simple, requiring only the addition of an integral element to correct the inductance parameter, which can significantly improve the robustness of the system. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the implementation of the present invention; Figure 2 The simulation results of the phase-locked loop of this invention are shown below; Figure 3 The simulation results for inductor parameter correction of this invention; Figure 4 The AC side current of this invention dq Simulation results of axis components; Figure 5 AC side current for traditional model predictive control dq The simulation results for the shaft component show that the inductance parameter is 150% of the rated value. Figure 6 AC side current for traditional model predictive control dq The simulation results for the axial component show that the inductance parameter is 50% of the rated value. Detailed Implementation

[0016] Combination Figure 1 As shown, the present invention provides a predictive current control method for grid-connected inverters that takes into account inductor parameter correction, comprising the following steps: Step 1: Collect information such as DC side voltage, AC three-phase current and AC three-phase voltage of the inverter through the sensing unit. Specifically, the DC side voltage and AC three-phase voltage of the inverter are collected through the voltage sensor, and the AC three-phase current of the inverter is collected through the current sensor. Step 2: Calculate the AC side voltage phase angle based on the AC side phase A voltage to provide a phase reference for the system. Specifically, calculating the AC side voltage phase angle includes the following steps: The in-phase virtual voltage, which is in phase with the AC side phase A voltage, is calculated using a second-order generalized integrator. u α Vertical virtual voltage lagging behind the AC side A-phase voltage u β : (1) In the formula, e a This refers to the AC phase A voltage. ω g The angular frequency of the AC side voltage. k s is an adjustable coefficient, and s is a complex frequency; Calculate the phase angle of the AC side voltage using the arctangent function: (2) In the formula, θ This represents the phase angle of the grid-side voltage.

[0017] Step 3: Calculate the AC side voltage and AC side current based on the AC side voltage phase angle. dq The axial component, specifically, is used to calculate the AC side voltage and current. dq The method for shaft component is as follows: The AC side voltage is calculated using the following formula. dq Axis components: (3) In the formula, e d and e q For AC side voltage dq Axial components, e b and e c These are the AC phase B and phase C voltages, respectively. The AC side current is calculated using the following formula. dq Axis components: (4) In the formula, i a , i b and i c This indicates the three-phase current value on the AC side. i d and i q For AC side current dq Axial components.

[0018] Step 4: Calculate the AC side current based on the grid-connected power reference value. dq Shaft component reference values, specifically, for calculating the AC side current. dq The specific method for setting the shaft component reference values ​​is as follows: Based on the reference values ​​of grid-connected active and reactive power P * and Q * Calculate the AC side current dq Axis component reference values: (5) In the formula, and For AC side current dq Axis component reference values.

[0019] Step 5, based on the AC side current q Shaft component reference value and AC side current q The error between the actual values ​​of the shaft components is used to correct the inductance parameters, which includes the following steps: Calculate the AC side current q Error between reference and actual values ​​of shaft components: (6) In the formula, Δ i q AC side current q Shaft component error; Calculate the feedback values ​​of the inductor parameters: (7) In the formula, Δ L This is the inductor parameter feedback value. k i The integral coefficient; Correct inductor parameters: (8) In the formula, This is the inductance parameter correction value. L 0 represents the initial value of the inductance parameter.

[0020] Step 6: Using the prediction model, calculate the predicted AC side current values ​​corresponding to the zero voltage vector and the six non-zero voltage vectors. dq The axis component, specifically, is as follows: Calculate the predicted current value using a current prediction model: (9) In the formula, T s The sampling period is and Voltage vector V i The corresponding predicted current value, R The internal resistance of the AC-side filter inductor, and Voltage vector V i of dq Axis components, subscript .

[0021] Step 7: Based on the predicted AC current, calculate the value function and select the optimal voltage vector, apply its switching state to the inverter, and control the system operation. This specifically includes the following steps: Calculate the value functions corresponding to the zero voltage vector and the six non-zero voltage vectors: (10) Compare the value function values ​​and select the optimal voltage vector: (11) In the formula, V opt The optimal voltage vector; like V opt = V If 0, then by judging the applied voltage vector situation at the previous moment, further selection is made from... V 0 and V Selecting the zero vector in 7: (12) In the formula, This is the voltage vector applied at the previous moment; The switch state is determined by a three-bit binary number. S a S b S c ]express, S k = 1( k = a , b , c ) indicates inverter k The upper bridge arm switch is on and the lower bridge arm switch is off. S k = 0 indicates inverter k The upper bridge arm switch is off and the lower bridge arm switch is on. V The inverter switching state corresponding to 0 is [0 0 0]. V The inverter switching state corresponding to 1 is [1 0 0]. V The inverter switching state corresponding to 2 is [1 1 0]. V The inverter switching state corresponding to 3 is [0 1 0]. V The inverter switching state corresponding to 4 is [0 1 1]. V The inverter switch state corresponding to 5 is [0 0 1]. V The inverter switch state corresponding to 6 is [1 0 1]. V The inverter switching state corresponding to 7 is [1 1 1].

[0022] The simulation conditions for this invention embodiment are shown in Table 1. The simulation results are as follows: Figures 2 to 4 As shown, the method provided by this invention can accurately lock the grid phase, quickly correct the inductance value to the true value, and the AC side current... dq The axis components accurately track their given values.

[0023] Table 1 Grid-side voltage 311V / 50Hz Peak / Frequency Grid-side filter inductor 5mH / 0.1Ω Inductance / Internal Resistance <![CDATA[Initial value of inductor L 0]]> 7.5mH 150% of rated value Grid-connected power reference value 10kW / 0Var Meritorious / Ineffective DC bus voltage 700V Sampling frequency 10kHz Figure 5 As shown L = 7.5mH (150% of rated value) AC side current without correction circuit dq Axis component simulation waveforms Figure 6 As shown L = 2.5mH ​​(50% of rated value) AC side current without correction circuit dq The simulated waveforms of the axial components show that when the inductance parameters are mismatched, d The axis components exhibit significant steady-state tracking error and cannot track to the reference value. q The shaft component control effect is poor. In contrast, the method provided by this invention achieves this by correcting the inductance parameters online. dq Accurate tracking of shaft current.

[0024] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

[0025] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0026] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0027] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A predictive current control method for grid-connected inverters that takes into account inductor parameter correction, characterized in that, The control method includes the following steps: Step 1: Collect information on the inverter's DC side voltage, AC side three-phase current, and AC side three-phase voltage through the sensing unit; Step 2: Calculate the phase angle of the AC side voltage based on the AC side phase A voltage to provide a phase reference for the system; Step 3: Calculate the AC side voltage and AC side current based on the AC side voltage phase angle. Axial components; Step 4: Calculate the AC side current based on the grid-connected power reference value. Axis component reference values; Step 5, based on the AC side current Shaft component reference value and AC side current The error between the actual values ​​of the shaft components is used to correct the inductance parameters; the correction of the inductance parameters specifically includes the following steps: Calculate the AC side current Error between reference and actual values ​​of shaft components: ， In the formula, AC side current The error between the reference value and the actual value of the shaft component For AC side current Axial components, This is the reference value for the q-axis component of the AC side current; Calculate the feedback values ​​of the inductor parameters: ， In the formula, This is the inductor parameter feedback value. The integral coefficient; Correct inductor parameters: ， In the formula, These are the correction values ​​for inductance parameters. These are the initial values ​​for the inductor parameters; Step 6: Using the prediction model, calculate the predicted AC side current values ​​corresponding to the zero voltage vector and the six non-zero voltage vectors. Axial components; calculate the predicted AC side current values ​​corresponding to the zero voltage vector and the six non-zero voltage vectors. The specific method for shaft component is as follows: Calculate the predicted current value using a current prediction model Axis components: ， In the formula, T s The sampling period is and Voltage vectors Corresponding predicted current value , The axial component, R is the internal resistance of the AC-side filter inductor. and Voltage vectors of , Axis components, subscript ; Step 7: Calculate the value function based on the predicted AC current value and select the optimal voltage vector, apply its switching state to the inverter, and control the system operation.

2. The predictive current control method for grid-connected inverters considering inductor parameter correction according to claim 1, characterized in that, In step 1, the three-phase current on the AC side of the inverter is acquired by a current sensor.

3. The predictive current control method for grid-connected inverters considering inductance parameter correction according to claim 1, characterized in that, Step 2 involves calculating the AC side voltage phase angle, specifically including the following steps: The in-phase virtual voltage, which is in phase with the AC side phase A voltage, is calculated using a second-order generalized integrator. Vertical virtual voltage lagging behind the AC side A-phase voltage : ， In the formula, This refers to the AC side A-phase voltage. The angular frequency of the AC side voltage. This is an adjustable coefficient. It is a complex frequency; Calculate the phase angle of the AC side voltage using the arctangent function: ， In the formula, This represents the phase angle of the grid-side voltage.

4. The predictive current control method for grid-connected inverters considering inductor parameter correction according to claim 3, characterized in that, In step 3, the AC side voltage and AC side current are calculated. The specific method for shaft component is as follows: The AC side voltage is calculated using the following formula. Axis components: ， In the formula, and For AC side voltage Axial components, , , These are the AC phase A, phase B, and phase C voltages, respectively. The AC side current is calculated using the following formula. Axis components: ， In the formula, , and This indicates the three-phase current value on the AC side. and For AC side current Axial components.

5. The predictive current control method for grid-connected inverters considering inductor parameter correction according to claim 4, characterized in that, In step 4, calculate the AC side current. The specific method for setting the shaft component reference values ​​is as follows: Based on the reference values ​​of grid-connected active and reactive power and Calculate the AC side current Axis component reference values: ， In the formula, and These are the AC side currents. Axis component reference values.

6. The predictive current control method for grid-connected inverters considering inductor parameter correction according to claim 5, characterized in that, Step 7 involves selecting the optimal voltage vector, which specifically includes the following steps: Calculate the value functions corresponding to the zero voltage vector and the six non-zero voltage vectors: ， Compare the value function values ​​and select the optimal voltage vector: ， In the formula, For the optimal voltage vector, and These are the AC side currents. , Axis component reference values.

7. The predictive current control method for grid-connected inverters considering inductance parameter correction according to claim 6, characterized in that, The optimal voltage vector, if the optimal voltage vector is a zero vector Then, by judging the voltage vector situation at the previous moment, further... and Select the zero vector: ， In the formula, This is the voltage vector applied at the previous moment.

8. The predictive current control method for grid-connected inverters considering inductor parameter correction according to claim 7, characterized in that, The switching state of the voltage vector is specifically as follows: The switch status is represented by a three-bit binary number. express, Indicates inverter The upper bridge arm switch is on and the lower bridge arm switch is off. This refers to the abc three-phase inverter; Indicates inverter The upper bridge arm switch is off and the lower bridge arm switch is on; The corresponding inverter switch state is [0 0 0]. The corresponding inverter switch state is [1 0 0]. The corresponding inverter switching state is [1 1 0]. The corresponding inverter switching states are [0 10]. The corresponding inverter switching state is [0 1 1]. The corresponding inverter switching state is [0 0 1]. The corresponding inverter switch state is [1 0 1]. The corresponding inverter switching state is [1 1 1].

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