Five-level vibration table power supply and predictive control method thereof

Abstract

The invention discloses a five-level vibration table power supply and a prediction control method thereof. The method comprises a five-level converter, a first filter inductor, a second filter inductor and a filter capacitor which are bridged on two poles of a direct-current 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 to the two ends of the filter capacitor in parallel. According to the five-level vibration table power supply topology, the inductance value of the filter inductor used in the device is about one half of the filter inductance value in a traditional single-phase two-level converter, the inductance value and the size of the filter inductor are greatly reduced, cost is saved, and the five-level vibration table power supply topology has good application prospects in a renewable energy power generation system. Meanwhile, an MPC control strategy is adopted, the stability, efficiency and electric energy quality of a power supply system are improved by minimizing a cost function and finding an optimal input index, and an output voltage waveform with certain quality is generated, so that more accurate and efficient electric power support is provided for a vibration test system.

Description

Technical Field

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

[0002] With the continuous advancement of science and technology, vibration testing, as an indispensable technology in modern industry and scientific research, is widely used in aerospace, automobile manufacturing, electronic equipment, precision machinery and other fields, especially in verifying reliability and durability. The harm caused by vibration should not be underestimated. In the field of mechanical processing, vibration often causes wear of mechanical structures and leads to reduced precision; in the field of transportation, vibration will lead to reduced safety and comfort of vehicles during driving. Sinusoidal vibration is an important vibration form for ground vibration environment simulation tests, and the electric vibration table system is the main system for sinusoidal vibration. Among them, the vibration table power supply is the core part of the entire vibration system. With the development of new energy, intelligent manufacturing and other fields, the vibration table power supply system will play an important role in a wider range of fields in the future, especially in aerospace, automobile, 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 supply 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 advantages such as simple control structure and diverse application scenarios. However, this control strategy cannot achieve zero-error tracking of AC signals, cannot effectively suppress harmonics, and the integral term will cause phase lag problems, which seriously affects the control effect when the system output frequency is high. Therefore, a single PI control cannot meet the requirements of a wide output frequency range and low output harmonic content for the vibration table power supply. Summary of the invention

[0004] In order 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, comprising: A five-level converter, a first filter inductor, a second filter inductor, and a filter capacitor connected across the two poles of the 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 the load is connected in parallel to both ends of the filter capacitor.

[0006] Furthermore, the five-level converter includes a first bridge arm and a second bridge arm having the same structure, and the first bridge arm and the second bridge arm both include: A first power electronic switch tube, a second power electronic switch tube, a third power electronic switch tube, and a fourth power electronic switch tube connected in series in a forward direction; the drain of the first power electronic switch tube is connected to the positive electrode of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative electrode of the DC power supply; a first flying capacitor, a positive electrode of which is connected to the drain of the first power electronic switch tube, and a negative electrode of which is connected to the source of the fourth power electronic switch tube; A second flying capacitor, wherein a positive electrode thereof is connected to the drain of the second power electronic switch tube, and a negative electrode thereof is connected to the source of the third power electronic switch tube.

[0007] Furthermore, of 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.

[0008] Furthermore, the power electronic switches all adopt insulated gate bipolar transistors.

[0009] Furthermore, through different switch combinations, the five-level vibration table power output , , , , Five levels and eight switch states, including is the voltage of the DC power supply.

[0010] On the other hand, the present invention also provides a predictive control method for the five-level vibration table power supply, comprising the following steps: The five-level vibration table power supply topology is systematically modeled and a discrete mathematical model is obtained; Constructing a cost function through the discretized mathematical model; Calculating the first-order derivative and the second-order derivative of the cost function, selecting the optimal state equation to minimize the cost function, and obtaining an expression for the voltage between the two output ports of the five-level converter; According to the expression, a set of input voltages is obtained through SPWM modulation so that the output voltage of the five-level vibration table power supply is closest to the expected value.

[0011] Furthermore, the cost function is: (3) in, is the voltage reference value of the filter capacitor C at time k+2, It is the predicted value of the voltage of the filter capacitor C at time k+2.

[0012] Furthermore, the expression is: (11) in represents the voltage between the two output ports ab of the five-level converter, Indicates the value of the first filter inductor or the second filter inductor, Represents the voltage of the filter capacitor C, Represents the current flowing through the filter capacitor C, Represents filter capacitor, represents the current flowing through the first filter inductor L1 and 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 time.

[0013] Furthermore, the first filter inductor and the second filter inductor have the same value.

[0014] The advantages of the present invention are: 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 filter inductance value in the traditional single-phase two-level converter, which greatly reduces the inductance value and volume of the filter inductor, saves costs, and has a good application prospect in renewable energy power generation systems. At the same time, the present invention adopts the MPC control strategy, by minimizing the cost function, finds the optimal input index, improves the stability, efficiency and power quality of the power supply system, and generates an output voltage waveform with a certain quality, thereby providing more accurate and efficient power support for the vibration test system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings: Figure 1 A five-level vibration table power supply circuit diagram according to an embodiment of the present invention is shown.

[0016] Figure 2 This is a flow chart of the predictive control algorithm proposed in the present invention.

[0017] Figure 3 It is a schematic diagram of the output voltage effect of the novel five-level vibration table power supply predictive control strategy of the present invention.

[0018] Figure 4 It is a schematic diagram of the output voltage THD value under the resistive load condition of the present invention.

[0019] Figure 5 Schematic diagram of the output voltage THD value under nonlinear load conditions of the present invention. DETAILED DESCRIPTION

[0020] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0021] Model Predictive Control (MPC) is an advanced control method for dynamic system control. It uses the mathematical model of the system to make multi-step predictions and then optimizes the control input at the current moment to minimize the performance index within the prediction period. MPC re-optimizes at each sampling moment, so that it can cope with system dynamic changes and uncertainties to better handle the continuous state and control input of the system.

[0022] A new five-level vibration table power supply topology Figure 1 As shown in the figure. This topology is composed of 8 power electronic switch tubes. The 8 switch tubes are The novel five-level vibration table power supply topology consists of two parts, the upper and lower parts. In the novel seven-level vibration table power supply topology of the present invention, the power electronic switches all use insulated-gate bipolar transistors (IGBT).

[0023] Specifically, Figure 1 As shown, 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 the load is connected in parallel at both ends of the filter capacitor.

[0024] The five-level converter comprises a first bridge arm and a second bridge arm of the same structure, wherein the first bridge arm comprises: a first power electronic switch tube connected in forward series , the second power electronic switch tube 、Third power electronic switch tube 、The fourth power electronic switch tube The drain of the first power electronic switch tube is connected to the positive electrode of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative electrode of the DC power supply; the first flying capacitor C2, whose positive electrode is connected to the first power electronic switch tube The drain of the fourth power electronic switch tube is connected to the negative electrode of the fourth power electronic switch tube. The source of the second flying capacitor C1, whose positive electrode is connected to the second power electronic switch tube The drain of the third power electronic switch tube is connected to the negative electrode of the third power electronic switch tube. The source.

[0025] The second bridge arm comprises: a first power electronic switch tube connected in series in a forward direction , the second power electronic switch tube 、Third power electronic switch tube 、The fourth power electronic switch tube The drain of the first power electronic switch tube is connected to the positive electrode of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative electrode of the DC power supply; the first flying capacitor C4, whose positive electrode is connected to the first power electronic switch tube The drain of the fourth power electronic switch tube is connected to the negative electrode of the fourth power electronic switch tube. The source of the second flying capacitor C3, whose positive electrode is connected to the second power electronic switch tube The drain of the third power electronic switch tube is connected to the negative electrode of the third power electronic switch tube. The source.

[0026] Of the two output ports of the five-level converter, one output port a is provided on the third power electronic switch tube of the first bridge arm. The other output port b is set at the drain of the second bridge arm. at the drain.

[0027] for Figure 1 In the new five-level vibration table power supply topology, capacitor Divide As can be seen from Table 1, through different switch combinations, the new five-level vibration table power supply can output , , , , Five levels and eight switch states.

[0028] Table 1 Working status of the new five-level vibration table power supply

[0029] First, the present invention systematically models the power supply topology of the novel five-level vibration table. The relationship between the output voltage and current can be obtained from Figure 1 It is obtained, which is expressed as: (1) in represents the voltage between the two output ports ab of the five-level converter, Indicates 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 filter capacitor, represents the current flowing through the filter inductors L1 and L2, Indicates the current flowing through the load.

[0031] By transforming formula (1), we get: (2) Next, we will move on to the model predictive control algorithm. Figure 2 This 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 taking the derivative of the cost function to find the extreme value. 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, and construct a cost function to quantify this requirement: (3) in, is the voltage reference value of the filter capacitor C at time k+2, It is the predicted value of the voltage of the filter capacitor C at time k+2.

[0033] By discretizing equation (2), we get: (4) (5) in It is the sampling period of the whole system, including output voltage, inverter current and output current.

[0036] Assume that the load current does not change suddenly during the sampling period: (6) The constructed cost function is the mean square error of the load voltage. The k+2 moment is selected because the control delay is taken into account. To simplify the calculation, considering that the load current will not change suddenly and can be approximated within one cycle, the load voltage at the k+2 moment is obtained by combining equations 2, 4, and 5: (7) To obtain a set of input voltages that makes the output voltage closest to the expected value, it is necessary to find the minimum value of the cost function. Finding the minimum value must be derived. Therefore, for the cost function, the first-order derivative and the second-order derivative are obtained. The second-order derivative is greater than zero, indicating that the first-order derivative is monotonically increasing, that is, the zero-crossing point of the first-order derivative is the minimum point of the cost function, indicating that the zero-crossing point of the first-order derivative is the required input voltage. The partial derivative of the input voltage is obtained: (8) Combining equations 7 and 8, we get the equation for input voltage: (9) By linear interpolation we get: (10) Substituting it into equation (9): (11) in represents the voltage between the two output ports ab of the five-level converter, Indicates the value of the first filter inductor or the second filter inductor, Represents the voltage of the filter capacitor C, Represents the current flowing through the filter capacitor C, Represents filter capacitor, represents the current flowing through the first filter inductor L1 and 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 time.

[0037] Through the above equation, SPWM can be used to control the input voltage.

[0038] Furthermore, the present invention also verifies the correctness of the theory by establishing a simulation model. Experiments show that the proposed strategy can output a voltage waveform with a certain quality under various load conditions, and the THD values ​​are 1.14% and 1.73% respectively, which is in line with expectations. Figure 3 is the voltage waveform output by the simulation experiment. Figure 4 , Figure 5 They are the THD values ​​of the output voltage under different working conditions.

[0039] Compared with the traditional topology, the five-level vibration table power supply topology can provide five voltage levels, significantly reducing the harmonic components in the output voltage, and improving the output accuracy and stability. It is especially suitable for high-precision vibration testing needs, ensuring the vibration table drive accuracy and stability during the test process, reducing errors and unnecessary energy loss. In addition, thanks to its low harmonic characteristics, this power supply topology can reduce the need for external filters, thereby reducing the size and complexity of the system, providing a more ideal solution for efficient vibration test systems.

[0040] 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 a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A five-level vibration table power supply, characterized in that: include: A five-level converter, a first filter inductor, a second filter inductor, and a filter capacitor are connected across the positive and negative electrodes of a DC power supply; wherein the first filter inductor, the filter capacitor, and the second filter inductor are sequentially connected in series and then connected to two output ports of the five-level converter, and the load is connected in parallel to both ends of the filter capacitor.

2. A five-level vibration table power supply according to claim 1, characterized in that: The five-level converter comprises a first bridge arm and a second bridge arm having the same structure, wherein the first bridge arm and the second bridge arm both comprise: A first power electronic switch tube, a second power electronic switch tube, a third power electronic switch tube, and a fourth power electronic switch tube connected in series in a forward direction; the drain of the first power electronic switch tube is connected to the positive electrode of the DC power supply; the source of the fourth power electronic switch tube is connected to the negative electrode of the DC power supply; a first flying capacitor, a positive electrode of which is connected to the drain of the first power electronic switch tube, and a negative electrode of which is connected to the source of the fourth power electronic switch tube; A second flying capacitor, wherein a positive electrode thereof is connected to the drain of the second power electronic switch tube, and a negative electrode thereof is connected to the source of the third power electronic switch tube.

3. A five-level vibration table power supply according to claim 2, characterized in that: Of 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.

4. A five-level vibration table power supply according to claim 2 or 3, characterized in that: The power electronic switches all adopt insulated gate bipolar transistors.

5. A five-level vibration table power supply according to claim 1, characterized in that: Through different switch combinations, the five-level vibration table power output , , , , Five levels and eight switch states, including is the voltage of the DC power supply.

6. A five-level vibration table power supply according to claim 1, characterized in that: The first filter inductor and the second filter inductor have the same value.

7. A predictive control method for a five-level vibration table power supply according to any one of claims 1 to 6, characterized in that: The steps include: The five-level vibration table power supply topology is systematically modeled and a discrete mathematical model is obtained; Constructing a cost function through the discretized mathematical model; Calculating the first-order derivative and the second-order derivative of the cost function, selecting the optimal state equation to minimize the cost function, and obtaining an expression for the voltage between the two output ports of the five-level converter; According to the expression, a set of input voltages is obtained through SPWM modulation so that the output voltage of the five-level vibration table power supply is closest to the expected value.

8. The method according to claim 7, characterized in that The cost function is: (3) in, is the voltage reference value of the filter capacitor C at time k+2, It is the predicted value of the voltage of the filter capacitor C at time k+2.

9. The method according to claim 7, characterized in that: The expression is: (11) in represents the voltage between the two output ports a and b of the five-level converter, Indicates the value of the first filter inductor or the second filter inductor, Represents the voltage of the filter capacitor C, Represents the current flowing through the filter capacitor C, Represents filter capacitor, represents the current flowing through the first filter inductor and 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 time.

Images