Three-phase PWM rectifier control method based on improved mode switching

Abstract

The invention relates to the technical field of power electronics, in particular to a three-phase PWM (Pulse Width Modulation) rectifier control method based on improved mode switching, which comprises the following steps of: establishing a system state space model, compensating a dynamic voltage vector, predicting a control strategy, an improved mode switching method and a self-adaptive adjustment mechanism. A dynamic voltage vector compensation mechanism is introduced, and the amplitude and the phase angle of a voltage vector are adjusted in real time, so that errors are reduced, control precision is improved, and switching loss is further reduced. According to the change of the actual load and the input voltage, the mode switching sequence is adaptively adjusted, and the optimal control performance of the system under various working conditions is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a three-phase PWM rectifier control method based on improved mode switching. Background Art

[0002] The existing PWM rectifier control method is mainly based on SVPWM (space vector pulse width modulation) technology. The advantage of this method is that it can effectively reduce the harmonic components in the output current waveform and improve the utilization rate of the DC bus voltage. However, with the increase of rectifier power and switching frequency, the number of switching times of the switch tube increases significantly, resulting in increased switching losses, which has become a bottleneck restricting the development of high power density rectifiers.

[0003] In order to solve the problem of switching loss, existing improved technologies such as the three-phase three-level PWM rectifier control method based on multi-mode switching reduce the switching loss by reducing the switching state. However, these methods still have shortcomings in dynamic response and efficiency improvement.

[0004] Therefore, it is necessary to further optimize the mode switching sequence, reduce redundant switching operations, and introduce a dynamic compensation mechanism to improve the overall system performance. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a three-phase PWM rectifier control method based on improved mode switching to solve the problem that the existing methods are still insufficient in terms of dynamic response and efficiency improvement.

[0006] Based on the above purpose, the present invention provides a three-phase PWM rectifier control method based on improved mode switching, comprising the following steps:

[0007] S1. Establish a state space model of the PWM rectifier system to describe the dynamic changes of voltage and current;

[0008] S2, real-time detection of the deviation between the actual voltage vector and the ideal reference voltage vector, calculation of the error vector, and dynamic compensation of the voltage vector according to the error vector, generating a new PWM control signal according to the compensated voltage vector, and driving the switching device to correct the output voltage;

[0009] S3. Establish a prediction model based on historical load data and input voltage, use the model to estimate the load changes in the next few control cycles, and adjust the switch state in advance to adapt to different load conditions according to the predicted load changes;

[0010] S4, simplifying the working mode of the three-phase PWM rectifier system, and selecting a corresponding simplified mode for switching according to the position of the voltage vector in the simplified sector;

[0011] S5. Monitor the input voltage and load current of the three-phase PWM rectifier system in real time, and adaptively adjust the mode switching sequence according to the current voltage and current status.

[0012] Preferably, in step S1, the state space model of the PWM rectifier system includes a three-phase PWM rectifier, a current sensor, a voltage sensor, an SVPWM and a controller, the current sensor and the voltage sensor are respectively used to detect the real-time current and actual voltage vector of the three-phase PWM rectifier, the SVPWM is used to generate a PWM control signal, and the controller is used to adaptively adjust the mode switching sequence.

[0013] Preferably, in step S2, the compensated voltage vector U comp Determined by the following formula:

[0014] U comp =U actual +ΔU;

[0015] Among them, U actual Represents the actual voltage vector.

[0016] Preferably, step S4 specifically includes:

[0017] The original eighteen working modes of the three-phase PWM rectifier are simplified to twelve. In six sectors, the corresponding simplified mode is selected for switching according to the position of the voltage vector, and redundant switching operations are reduced during the switching process.

[0018] Preferably, step S5 specifically includes:

[0019] Determine whether the load prediction is consistent with the actual output. If they are consistent, end the adjustment. If they are inconsistent, perform feedback adjustment to ensure the accuracy of the prediction control. Beneficial effects of the present invention: Based on the existing multi-mode switching technology, the present invention introduces a dynamic voltage vector compensation mechanism to reduce errors, improve control accuracy, and further reduce switching losses by adjusting the amplitude and phase angle of the voltage vector in real time. According to the changes in the actual load and input voltage, the order of mode switching is adaptively adjusted to ensure the optimal control performance of the system under various working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 is a block diagram of a system state space model of an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of dynamic voltage vector compensation according to an embodiment of the present invention;

[0023] Figure 3 A flowchart of the predictive control strategy according to an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of an improved mode switching method according to an embodiment of the present invention; DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0026] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] like Figure 1-Figure 4 As shown, the embodiment of this specification provides a three-phase PWM rectifier control method based on improved mode switching, which is as follows:

[0028] like Figure 1 As shown, the state-space model of the PWM rectifier system monitors these variables in real time through voltage and current sensors and inputs them into the controller to generate control signals to drive the power switches.

[0029] Detect the deviation between the output voltage and the reference voltage in real time and obtain the actual voltage vector U through the sensor actual and the ideal reference voltage vector U ref .

[0030] like Figure 2 As shown, according to the error vector ΔU, the compensation vector U is dynamically adjusted comp , so that it is consistent with the reference voltage vector U ref Try to overlap as much as possible. The compensated voltage vector U comp Determined by the following formula:

[0031] U comp =U actual +ΔU;

[0032] After compensation, U comp Used to generate new PWM control signals to drive switching devices to correct the output voltage.

[0033] like Figure 3 As shown, a prediction model is established through historical load data and input voltage, and the load changes in the next few control cycles are estimated using the model.

[0034] According to the predicted load changes, the switch status is adjusted in advance to adapt to different load conditions and reduce switching delays.

[0035] The accuracy of the prediction results is monitored in real time, and feedback adjustments are made based on the actual output voltage and current to ensure the accuracy of the predictive control.

[0036] like Figure 4 As shown, the original 18 working modes are simplified to 12. In the six sectors, the corresponding simplified modes are selected for switching according to the position of the voltage vector. During the switching process, redundant switching operations are minimized to reduce switching losses.

[0037] The adaptive adjustment mechanism monitors the input voltage, output voltage and load current in real time through voltage and current sensors, and determines the current working status based on these data.

[0038] If the adaptive adjustment mechanism detects a change in system load or input voltage, the controller will automatically adjust the mode switching sequence to adapt to the new operating conditions. For example, when the load suddenly increases, the system may need to switch to large vector mode more quickly to maintain output voltage stability.

[0039] Based on the adjustment decision, the controller dynamically changes the order of mode switching and generates corresponding control signals to ensure the stability and efficiency of the system under different working conditions.

[0040] The present invention effectively reduces switching losses and improves the control accuracy and dynamic response capability of the system by optimizing the mode switching sequence, introducing dynamic voltage vector compensation and adaptive adjustment mechanism. The simplified mode switching reduces redundant operations and significantly improves the power conversion efficiency. At the same time, real-time compensation and adaptive adjustment enable the system to quickly respond to load changes, ensure the stability and accuracy of the output voltage, and be applicable to a variety of complex working conditions.

[0041] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A three-phase PWM rectifier control method based on improved mode switching, characterized in that: The method comprises the following steps: S1. Establish a state space model of the PWM rectifier system to describe the dynamic changes of voltage and current; S2, real-time detection of the deviation between the actual voltage vector and the ideal reference voltage vector, calculation of the error vector, and dynamic compensation of the voltage vector according to the error vector, generating a new PWM control signal according to the compensated voltage vector, and driving the switching device to correct the output voltage; S3. Establish a prediction model based on historical load data and input voltage, use the model to estimate the load changes in the next few control cycles, and adjust the switch state in advance to adapt to different load conditions according to the predicted load changes; S4, simplifying the working mode of the three-phase PWM rectifier system, and selecting a corresponding simplified mode for switching according to the position of the voltage vector in the simplified sector; S5. Monitor the input voltage and load current of the three-phase PWM rectifier system in real time, and adaptively adjust the mode switching sequence according to the current voltage and current status.

2. The three-phase PWM rectifier control method based on improved mode switching according to claim 1, characterized in that: In step S1, the state space model of the PWM rectifier system includes a three-phase PWM rectifier, a current sensor, a voltage sensor, an SVPWM and a controller, wherein the current sensor and the voltage sensor are respectively used to detect the real-time current and the actual voltage vector of the three-phase PWM rectifier, the SVPWM is used to generate a PWM control signal, and the controller is used to adaptively adjust the mode switching sequence.

3. The three-phase PWM rectifier control method based on improved mode switching according to claim 1, characterized in that: In step S2, the compensated voltage vector U comp Determined by the following formula: U comp =U actual +ΔU; Among them, U actual Represents the actual voltage vector.

4. The three-phase PWM rectifier control method based on improved mode switching according to claim 1, characterized in that: Step S4 specifically includes: The original eighteen working modes of the three-phase PWM rectifier are simplified to twelve. In six sectors, the corresponding simplified mode is selected for switching according to the position of the voltage vector, and redundant switching operations are reduced during the switching process.

5. The three-phase PWM rectifier control method based on improved mode switching according to claim 1, characterized in that: Step S5 specifically includes: Determine whether the load prediction is consistent with the actual output. If they are consistent, end the adjustment. If they are inconsistent, perform feedback adjustment to ensure the accuracy of predictive control.

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