A five-level vibration table power supply and its predictive control method

Abstract

A five-level shaker power supply and its predictive control method, the method comprising: a five-level converter, a first filter inductor, a second filter inductor, and a filter capacitor connected across the two poles of a DC power supply; wherein, the first filter inductor, the filter capacitor, and the second filter inductor are connected in series and then connected to two output ports of the five-level converter, and a load is connected in parallel across the two ends of the filter capacitor. For the five-level shaker power supply topology of the present invention, the inductance value of the filter inductor used in this device is approximately half of the inductance value of the filter inductor in a traditional single-phase two-level converter, greatly reducing the inductance value and volume of the filter inductor, saving costs, and having good application prospects in renewable energy power generation systems. At the same time, the present invention adopts an MPC control strategy, finds the optimal input index by minimizing the cost function, improves the stability, efficiency, and power quality of the power supply system, generates an output voltage waveform with a certain quality, and thus provides more accurate and efficient power support for the vibration test system.

Description

Technical Field

[0001] The present invention relates to the technical field of power control, and particularly relates to a five-level vibration table power supply and its predictive control method. Background Art

[0002] With the continuous progress of technology, vibration testing, as an indispensable technology in modern industry and scientific research, is widely used in fields such as aerospace, automotive manufacturing, electronic equipment, and precision machinery. It plays a crucial role, especially in verifying reliability and durability. The harm caused by vibration cannot be underestimated. In the field of machining, vibration often causes wear of mechanical structures, resulting in a decrease in accuracy. In the field of transportation, vibration will lead to a decrease in the safety and comfort of vehicles during driving. Sinusoidal vibration is an important vibration form in ground vibration environment simulation tests, and the electro-vibration table system is the main system for generating sinusoidal vibration. Among them, the vibration table power supply is the core part of the entire vibration system. With the development of fields such as new energy and intelligent manufacturing, the future vibration table power supply system will play an important role in a wider range of fields, especially in aerospace, automotive, electronic products, and precision manufacturing, providing strong technical support for achieving higher standards of product testing and quality assurance.

[0003] Common control methods for vibration table power supplies include PI control, PR control, deadbeat control, repetitive control, etc. Traditional vibration table power control methods often face problems such as large output voltage fluctuations and high harmonic content, which have a negative impact on test accuracy and reliability. PI control is widely used in engineering practice due to its simple control structure and diverse applicable scenarios. However, this control strategy cannot achieve zero-static error tracking for AC signals, cannot effectively suppress harmonics, and the integral term will cause phase lag problems, seriously affecting the control effect when the system output frequency is high. Therefore, single PI control cannot meet the requirements of a wide output frequency range and low output harmonic content for vibration table power supplies. Summary of the Invention

[0004] To solve these problems, the present invention proposes a novel five-level vibration table power supply and its predictive control strategy, aiming to improve the stability, efficiency, and power quality of the power supply system, thereby providing more accurate and efficient power support for the vibration test system.

[0005] The present invention provides a five-level vibration table power supply, including:

[0006] A five-level converter, a first filter inductor, a second filter inductor, and a filter capacitor connected across the two poles of a DC power supply; wherein,

[0007] The first filter inductor, filter capacitor, and second filter inductor are connected in series and then connected to two output ports of the five-level converter, and the load is connected in parallel across both ends of the filter capacitor.

[0008] Further, the five-level converter includes a first bridge arm and a second bridge arm with the same structure, and both the first bridge arm and the second bridge arm include:

[0009] The first power electronic switch tube, the second power electronic switch tube, the third power electronic switch tube, and the fourth power electronic switch tube connected in series in the forward direction; the drain of the first power electronic switch tube is connected to the positive pole of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative pole of the DC power supply;

[0010] The first flying capacitor, whose positive pole is connected to the drain of the first power electronic switch tube and whose negative pole is connected to the source of the fourth power electronic switch tube;

[0011] The second flying capacitor, whose positive pole is connected to the drain of the second power electronic switch tube and whose negative pole is connected to the source of the third power electronic switch tube.

[0012] Further, among the two output ports of the five-level converter, one output port is arranged at the drain of the third power electronic switch tube of the first bridge arm, and the other output port is arranged at the drain of the third power electronic switch tube of the second bridge arm.

[0013] Further, all the power electronic switches adopt insulated gate bipolar transistors.

[0014] Further, through different switching combinations, the five-level vibration table power supply outputs 、 、 、 、 five levels and 8 switching states, where is the voltage of the DC power supply.

[0015] On the other hand, the present invention also provides a predictive control method for the five-level vibration table power supply as described above, including the following steps:

[0016] Perform system modeling on the five-level vibration table power supply topology to obtain a discretized mathematical model;

[0017] Construct a cost function through the discretized mathematical model;

[0018] Take the first derivative and the second derivative of the cost function, select the optimal state equation to minimize the cost function, and obtain the expression of the voltage between the two output ports of the five-level converter;

[0019] According to the expression, a set of input voltages are obtained through SPWM modulation so that the output voltage of the five-level vibration table power supply is closest to the expected value.

[0020] Further, the cost function is:

[0021] (3)

[0022] Wherein, is the voltage reference value of the filter capacitor C at time k + 2, is the predicted voltage value of the filter capacitor C at time k + 2.

[0023] Further, the expression is:

[0024] (11)

[0025] Where represents the voltage between two output ports ab of the five-level converter, represents the value of the first filter inductor or the second filter inductor, represents the voltage of the filter capacitor C, represents the filter capacitor, represents the current flowing through the first filter inductor L1 or the second filter inductor L2, represents the current flowing through the load, is the sampling period, is the voltage reference value of the filter capacitor C, and k represents time.

[0026] Further, the values of the first filter inductor and the second filter inductor are equal.

[0027] The advantages of the present invention are as follows: The five-level vibration table power supply topology of the present invention. The inductance value of the filter inductor used in this device is about half of the inductance value of the filter inductor in the traditional single-phase two-level converter, greatly reducing the inductance value and volume of the filter inductor, saving costs, and having good application prospects in renewable energy power generation systems. At the same time, the present invention adopts the MPC control strategy. By minimizing the cost function, the optimal input index is found, improving the stability, efficiency, and power quality of the power supply system, generating an output voltage waveform with a certain quality, so as to provide more accurate and efficient power support for the vibration test system. Description of the Drawings

[0028] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0029] Figure 1 Shows the five-level vibration table power supply circuit diagram according to an embodiment of the present invention.

[0030] Figure 2 Is the flow chart of the predictive control algorithm proposed by the present invention.

[0031] Figure 3 Is the schematic diagram of the output voltage effect of the novel five-level vibration table power supply predictive control strategy of the present invention.

[0032] Figure 4 Is the schematic diagram of the output voltage THD value under the resistive load condition of the present invention.

[0033] Figure 5 Is the schematic diagram of the output voltage THD value under the non-linear load condition of the present invention. Detailed implementation manners

[0034] Hereinafter, the exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be completely conveyed to those skilled in the art.

[0035] The model predictive control strategy (Model Predictive Control, abbreviated as MPC) is an advanced control method for dynamic system control. It uses the mathematical model of the system for multi-step prediction and then optimizes the control input at the current moment to minimize the performance index within the prediction period. MPC is re-optimized at each sampling moment, so as to be able to cope with the system dynamic changes and uncertainties and better handle the continuous state and control input of the system.

[0036] A novel five-level vibration table power supply topology is as Figure 1 shown. This topology is composed of 8 power electronic switching tubes in total. The 8 switching tubes are . The novel five-level vibration table power supply topology consists of upper and lower parts. In the novel seven-level vibration table power supply topology of the present invention, the power electronic switches all adopt insulated-gate bipolar transistors (IGBTs).

[0037] Specifically, as Figure 1As shown in the figure, a five-level vibration table power supply of the present invention includes: a five-level converter connected across the two poles of a DC power supply, a first filter inductor L1, a second filter inductor L2, and a filter capacitor C; wherein, the first filter inductor, the filter capacitor, and the second filter inductor are connected in series and then connected to two output ports a and b of the five-level converter, and a load is connected in parallel across the two ends of the filter capacitor.

[0038] The five-level converter includes a first bridge arm and a second bridge arm with the same structure. The first bridge arm includes: a first power electronic switch tube connected in series forward , a second power electronic switch tube , a third power electronic switch tube , a fourth power electronic switch tube ; the drain of the first power electronic switch tube is connected to the positive pole of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative pole of the DC power supply; a first flying capacitor C2, whose positive pole is connected to the drain of the first power electronic switch tube , and whose negative pole is connected to the source of the fourth power electronic switch tube ; a second flying capacitor C1, whose positive pole is connected to the drain of the second power electronic switch tube , and whose negative pole is connected to the source of the third power electronic switch tube .

[0039] The second bridge arm includes: a first power electronic switch tube connected in series forward , a second power electronic switch tube , a third power electronic switch tube , a fourth power electronic switch tube ; the drain of the first power electronic switch tube is connected to the positive pole of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative pole of the DC power supply; a first flying capacitor C4, whose positive pole is connected to the drain of the first power electronic switch tube , and whose negative pole is connected to the source of the fourth power electronic switch tube ; a second flying capacitor C3, whose positive pole is connected to the drain of the second power electronic switch tube , and whose negative pole is connected to the source of the third power electronic switch tube .

[0040] Among the two output ports of the five-level converter, one output port a is arranged at the drain of the third power electronic switch tube of the first bridge arm, and the other output port b is arranged at the drain of the third power electronic switch tube of the second bridge arm.

[0041] For Figure 1 the novel five-level vibration table power supply topology, the capacitor Divided separately voltages. It can be seen from Table 1 that through different switch combinations, the new five-level vibration table power supply can output 、 、 、 、 five levels and 8 switch states.

[0042] Table 1 Working states of the new five-level vibration table power supply

[0043]

[0044] First of all, the present invention conducts system modeling on the topology of the new five-level vibration table power supply. The relationship between the output voltage and current can be obtained from Figure 1 and is expressed as:

[0045] (1)

[0046] Where represents the voltage between the two output ports ab of the five-level converter, represents the value of the filter inductor L1 or L2 (L1 = L2 = L), represents the voltage of the filter capacitor C, represents the current flowing through the filter capacitor C, represents the filter capacitor, represents the current flowing through the filter inductors L1 and L2, represents the current flowing through the load.

[0047] By transforming formula (1), we get:

[0048] (2)

[0049] Secondly, enter the model predictive control algorithm part. Figure 2 is the flow chart of the predictive control algorithm proposed by the present invention. In this part, the present invention obtains the input voltage value by constructing a cost function and finding the extreme value by taking the derivative of the cost function. The purpose of the present invention is to obtain a set of input voltages through PWM regulation so that the output voltage is closest to the expected value. The cost function is constructed to quantify this requirement:

[0050] (3)

[0051] Where is the reference voltage value of the filter capacitor C at time k + 2, is the predicted voltage value of the filter capacitor C at time k + 2.

[0052] By discretizing equation (2), we get:

[0053] (4)

[0054] (5)

[0055] Among them is the sampling period of the entire system, including the output voltage, the inverter current, and the output current.

[0056] It is assumed that the load current does not change suddenly within the sampling period:

[0057] (6)

[0058] The constructed cost function is the mean square error of the load voltage. The selection of the k+2 moment is due to considering the control delay. To simplify the calculation, considering that the load current does not change suddenly, it can be approximated within one period. Combining equations 2, 4, and 5, the load voltage at the k+2 moment is obtained:

[0059] (7)

[0060] To obtain a set of input voltages that make the output voltage closest to the expected value, it is necessary to find the minimum value of the cost function. Finding the extreme value necessarily requires taking the derivative. Therefore, taking the first derivative and the second derivative of the cost function, it is obtained that the second derivative is greater than zero, indicating that the first derivative is monotonically increasing. That is, the zero crossing point of the first derivative is the minimum value point of the cost function, indicating that the zero crossing point of the first derivative is the required input voltage. Taking the partial derivative of the input voltage gives:

[0061] (8)

[0062] Combining equations 7 and 8, an equation about the input voltage is obtained:

[0063] (9)

[0064] It is obtained through the linear interpolation method:

[0065] (10)

[0066] Substitute it into equation (9):

[0067] (11)

[0068] Among them represents the voltage between the two output ports ab of the five-level converter, represents the value of the first filter inductor or the second filter inductor, represents the voltage of the filter capacitor C, represents the filter capacitor, represents the current flowing through the first filter inductor L1 or the second filter inductor L2 represents the current flowing through the load, is the sampling period, is the voltage reference value of the filter capacitor C, and k represents the moment.

[0069] Through the above equations, SPWM can be used to control the input voltage.

[0070] Furthermore, the present invention also verifies the correctness of the theory by establishing a simulation model. Experiments show that the proposed strategy can output voltage waveforms with certain quality under various load conditions, and the THD values are 1.14% and 1.73% respectively, meeting the expectations. Figure 3 is the voltage waveform output by the simulation experiment, Figure 4 、 Figure 5 are the THD values of the output voltage under different conditions respectively.

[0071] Compared with the traditional topology, the five-level shaker power supply topology can provide five voltage levels, significantly reducing the harmonic components in the output voltage, improving both the output accuracy and stability. It is especially suitable for high-precision vibration test requirements, ensuring the driving accuracy of the shaker and the stability during the test process, reducing errors and unnecessary energy losses. In addition, due to its low harmonic characteristics, this power supply topology can reduce the demand for external filters, thereby reducing the system volume and complexity, providing a more ideal solution for an efficient vibration test system.

[0072] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A predictive control method for a five-level vibration table power supply, characterized in that, The steps are as follows: Systematically model the five-level vibration table power supply topology to obtain a discretized mathematical model; Construct a cost function through the discretized mathematical model; Take the first derivative and second derivative of the cost function, select the optimal state equation to minimize the cost function, and obtain the expression of the voltage between the two output ports of the five-level converter; According to the expression, obtain a set of input voltages through SPWM modulation so that the output voltage of the five-level vibration table power supply is closest to the expected value; The expression is: (11) Among them represents the voltage between two output ports a and b of the five-level converter, represents the value of the first filter inductor or the second filter inductor, represents the voltage of the filter capacitor C, represents the filter capacitor, represents the current flowing through the first filter inductor or the second filter inductor, represents the current flowing through the load, is the sampling period, is the voltage reference value of the filter capacitor C, and k represents the moment; The five-level vibration table power supply includes: a five-level converter connected across the positive and negative poles of a DC power supply, a first filter inductor, a second filter inductor, and a filter capacitor; where The first filter inductor, the filter capacitor, and the second filter inductor are connected in series in sequence and then connected to the two output ports of the five-level converter, and the load is connected in parallel across the two ends of the filter capacitor; The five-level converter includes a first bridge arm and a second bridge arm with the same structure, and both the first bridge arm and the second bridge arm include: First power electronic switch tubes, second power electronic switch tubes, third power electronic switch tubes, and fourth power electronic switch tubes connected in series in the forward direction; the drain of the first power electronic switch tube is connected to the positive pole of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative pole of the DC power supply; A first flying capacitor, whose positive pole is connected to the drain of the first power electronic switch tube and whose negative pole is connected to the source of the fourth power electronic switch tube; A second flying capacitor, whose positive pole is connected to the drain of the second power electronic switch tube and whose negative pole is connected to the source of the third power electronic switch tube; Through different switch combinations, the five-level vibration table power supply outputs , , , , five levels and eight switch states, where is the voltage of the DC power supply; Among the two output ports of the five-level converter, one output port is set at the drain of the third power electronic switch tube of the first bridge arm, and the other output port is set at the drain of the third power electronic switch tube of the second bridge arm.

2. The method according to claim 1, wherein The cost function is: (3) Among them, is the voltage reference value of the filter capacitor C at the (k + 2)th moment, is the predicted voltage value of the filter capacitor C at the (k + 2)th moment.

3. The method according to claim 1 or 2, wherein All the power electronic switch tubes adopt insulated gate bipolar transistors.

4. The method according to claim 1, wherein The values of the first filter inductor and the second filter inductor are equal.

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