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

Abstract

The invention provides a seven-level vibration table power supply and a prediction control method thereof. The power supply comprises a first capacitor, a second capacitor, a seven-level converter, a first filter inductor, a second filter inductor and a filter capacitor. Wherein the seven-level converter is bridged on positive and negative electrodes of a direct-current power supply, and the first capacitor and the second capacitor are bridged on the positive and negative electrodes of the direct-current power supply after being connected in series; the first filter inductor, the filter capacitor and the second filter inductor are sequentially connected in series and then connected between two output ports of the seven-level converter, and a load is connected to the two ends of the filter capacitor in parallel. The required filtering inductance value is only one third of the filtering inductance value of a traditional single-phase two-level converter, and therefore the size and cost of the inductor are effectively reduced. Besides, a model predictive control (MPC) strategy is adopted, and the stability, the efficiency and the electric energy quality of the power supply system are further improved by optimizing a cost function and determining an optimal input index.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply control, and in particular to a seven-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] Compared with the traditional topology, the seven-level vibration table power supply topology significantly reduces the harmonic content of the output voltage by providing seven voltage levels, thereby improving the accuracy and stability of the output. This topology is particularly suitable for high-precision vibration testing needs, ensuring the accuracy of the vibration table drive and the stability of the test process while reducing errors and energy losses. Its low harmonic characteristics also reduce the dependence on external filters, thereby reducing the system size and simplifying the design, providing an ideal solution for efficient vibration test systems.

[0004] At present, the commonly used control methods for vibration table power supplies include PI control, PR control, zero-beat control and repetitive control. However, traditional control methods often face the problems of large output voltage fluctuations and high harmonic content, which directly affect the accuracy and reliability of the test. Among them, PI control is widely used due to its simple structure and wide range of applications, but it is not good enough in zero-error tracking of AC signals, harmonic suppression and high-frequency control effects. Due to the phase lag caused by the integral link, PI control is difficult to meet the requirements of low harmonic output of the vibration table power supply in a wide frequency range. Summary of the invention

[0005] In order to solve these problems, this paper proposes a new seven-level vibration table power supply and its predictive control strategy. This strategy significantly improves the stability, efficiency and power quality of the power supply system, and provides more accurate and efficient power support for the vibration test system, thus meeting the high standards and high reliability requirements of modern vibration testing.

[0006] The present invention provides a seven-level vibration table power supply, comprising:

[0007] A first capacitor, a second capacitor, a seven-level converter, a first filter inductor, a second filter inductor, and a filter capacitor; wherein the seven-level converter is connected across the positive and negative electrodes of a DC power supply, and the first capacitor and the second capacitor are connected in series and connected across the positive and negative electrodes of the DC power supply;

[0008] The first filter inductor, the filter capacitor and the second filter inductor are sequentially connected in series and then connected between the two output ports of the seven-level converter, and the load is connected in parallel to both ends of the filter capacitor.

[0009] Furthermore, the seven-level converter includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, and a third capacitor.

[0010] Furthermore, the first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are insulated gate bipolar transistors, and the third switch tube, the fourth switch tube, the seventh switch tube, and the eighth switch tube are bidirectional switch triodes; wherein,

[0011] The source of the first switch tube is connected to the drain of the second switch tube and the first filter inductor, and the point where the source of the first switch tube is connected to the drain of the second switch tube serves as a first output port;

[0012] The first main electrode of the third switch tube is connected to the positive electrode of the DC power supply, and the second main electrode is connected to the drain of the first switch tube;

[0013] The first main electrode of the fourth switch tube is connected to the negative electrode of the DC power supply, and the second main electrode is connected to the source electrode of the second switch tube;

[0014] The drain of the fifth switch tube is connected to the positive electrode of the DC power supply, and the source is connected to the source of the second switch tube;

[0015] The source of the sixth switch tube is connected to the negative electrode of the DC power supply, and the drain is connected to the drain of the first switch tube;

[0016] The first main electrode of the seventh switch tube is connected to the second filter inductor and the second output port, and the second main electrode is connected to the drain of the first switch tube;

[0017] The first main electrode of the eighth switch tube is connected to the second filter inductor and the second output port, and the second main electrode is connected to the source of the second switch tube; the second output port is where the first capacitor is connected to the second capacitor;

[0018] One end of the third capacitor is connected to the drain of the first switch tube, and the other end is connected to the source of the second switch tube.

[0019] Furthermore, through different switch combinations, the seven-level vibration table power supply outputs 3 / 2V DC 、V DC , 1 / 2V DC , 0, -1 / 2V DC , -V DC 、-3 / 2V DC Seven levels and eight switching states, among which V DC is the voltage of the DC power supply.

[0020] Furthermore, among the eight switch states, the third capacitor is in a discharging state in state 1, state 2, and state 8, the third capacitor is in a charging state in state 3 and state 6, and the third capacitor is not affected in state 4, state 5, and state 7.

[0021] Furthermore, the first filter inductor and the second filter inductor have the same value.

[0022] On the other hand, the present invention also provides a predictive control method for the seven-level vibration table power supply, comprising the following steps:

[0023] The power supply topology of the seven-level vibration table is systematically modeled and a discrete mathematical model is obtained;

[0024] Constructing a cost function through the discretized mathematical model;

[0025] 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 seven-level converter;

[0026] According to the expression, a set of input voltages is obtained through SPWM modulation so that the output voltage of the seven-level vibration table power supply is closest to the expected value.

[0027] The advantages of the present invention are as follows: the present invention proposes a new seven-level vibration table power supply topology, and its design significantly optimizes the parameter configuration of the filter inductor. The filter inductance value required by this topology is only one-third of the filter inductance value of the traditional single-phase two-level converter, thereby effectively reducing the volume and cost of the inductor, showing good application potential in renewable energy power generation systems. In addition, the present invention adopts a model predictive control (MPC) strategy to further improve the stability, efficiency and power quality of the power supply system by optimizing the cost function and determining the optimal input index. This control method generates a high-quality output voltage waveform, providing more accurate and efficient power support for the vibration test system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] 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:

[0029] Figure 1 A seven-level vibration table power supply circuit diagram according to an embodiment of the present invention is shown.

[0030] Figure 2 This is a flow chart of the predictive control algorithm proposed in the present invention.

[0031] Figure 3 It is a schematic diagram of the output voltage effect of the new seven-level vibration table power supply predictive control strategy of the present invention.

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

[0033] Figure 5 Schematic diagram of the output voltage THD value under nonlinear load conditions of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] A new seven-level vibration table power supply topology Figure 1 As shown. This topology is composed of 8 power electronic switch tubes. The 8 switch tubes are S1, S2, S3, S4, S5, S6, S7, S8, among which S3, S4, S7, S8 are bidirectional switch tubes. Specifically, the power supply structure is as follows:

[0037] The first capacitor C1, the second capacitor C2, the seven-level converter, the first filter inductor L1, the second filter inductor L2, and the filter capacitor C; wherein the seven-level converter is connected across the DC power supply V DC On the positive and negative electrodes, the first capacitor and the second capacitor are connected in series and then bridged across the positive and negative electrodes of the DC power supply;

[0038] The first filter inductor L1, the filter capacitor C, and the second filter inductor L2 are sequentially connected in series and then connected between the two output ports a and b of the seven-level converter, and the load is connected to both ends of the filter capacitor C in parallel.

[0039] The seven-level converter includes a first switch tube S1, a second switch tube S2, a third switch tube S3, a fourth switch tube S4, a fifth switch tube S5, a sixth switch tube S6, a seventh switch tube S7, an eighth switch tube S8, and a third capacitor C3.

[0040] The first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are insulated gate bipolar transistors, and the third switch tube, the fourth switch tube, the seventh switch tube, and the eighth switch tube are bidirectional switch triodes; wherein,

[0041] The source of the first switch tube S1 is connected to the drain of the second switch tube S2 and the first filter inductor L1, and the point where the source of the first switch tube S1 is connected to the drain of the second switch tube S2 serves as a first output port a;

[0042] The first main electrode of the third switch tube S3 is connected to the positive electrode of the DC power supply, and the second main electrode is connected to the drain of the first switch tube S1;

[0043] The first main electrode of the fourth switch tube S4 is connected to the negative electrode of the DC power supply, and the second main electrode is connected to the source electrode of the second switch tube S2;

[0044] The drain of the fifth switch tube S5 is connected to the positive electrode of the DC power supply, and the source is connected to the source of the second switch tube S2;

[0045] The source of the sixth switch tube S6 is connected to the negative electrode of the DC power supply, and the drain is connected to the drain of the first switch tube S1;

[0046] The first main electrode of the seventh switch tube S7 is connected to the second filter inductor L2 and the second output port b, and the second main electrode is connected to the drain of the first switch tube S1;

[0047] The first main electrode of the eighth switch tube S8 is connected to the second filter inductor L2 and the second output port b, and the second main electrode is connected to the source of the second switch tube S2; the second output port b is where the first capacitor C1 is connected to the second capacitor C2;

[0048] One end of the third capacitor C3 is connected to the drain of the first switch tube S1 , and the other end is connected to the source of the second switch tube S2 .

[0049] The first filter inductor L1 and the second filter inductor L2 have the same value.

[0050] 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). Figure 1 In the new seven-level vibration table power supply topology, capacitors C1, C2, and C3 each receive 1 / 2V DC As can be seen from Table 1, the new five-level vibration table power supply can output 3 / 2V through different switch combinations. DC 、V DC , 1 / 2V DC , 0, -1 / 2V DC , -V DC 、-3 / 2V DC There are seven levels and eight switch states, wherein in states 1, 2, and 8, capacitor C3 is in a discharging state, in states 3 and 6, capacitor C3 is in a charging state, and in states 4, 5, and 7, capacitor C3 is not affected.

[0051] Table 1 The power supply working state of the seven-level vibration table of the present invention

[0052] <![CDATA[S1]]> <![CDATA[S2]]> <![CDATA[S3]]> <![CDATA[S4]]> <![CDATA[S5]]> <![CDATA[S6]]> <![CDATA[S7]]> <![CDATA[S8]]> <![CDATA[Output voltage (V DC )]]> Switch Status <![CDATA[Capacitor C3]]> 1 0 0 0 1 0 0 0 3 / 2 V1 Discharge 1 0 0 0 0 0 0 1 1 V2 Discharge 1 0 1 1 0 0 0 0 1 / 2 V3 Charge 1 0 0 0 0 0 1 0 0 V4 constant 0 1 0 0 0 0 0 1 0 V5 constant 0 1 1 1 0 0 0 0 -1 / 2 V6 Charge 0 1 0 0 0 0 1 0 -1 V7 constant 0 1 0 0 0 1 0 0 -3 / 2 V8 Discharge

[0053] First is the system modeling part. The relationship between output voltage and current can be obtained from Figure 1 It is obtained, which is expressed as:

[0054]

[0055] Where V ab represents the voltage between the two output ports ab of the five-level converter, L represents the value of the filter inductor L1 or L2 (L1 = L2 = L), V C Represents the voltage of filter capacitor C, i C represents the current flowing through the filter capacitor C, C represents the filter capacitor, i L represents the current flowing through the filter inductors L1 and L2, i O Indicates the current flowing through the load.

[0056] By transforming formula (1), the present invention obtains:

[0057]

[0058] Next, we will move on to the model predictive control algorithm. Figure 2The flow chart of the predictive control algorithm proposed by the present invention comprises the following steps:

[0059] The power supply topology of the seven-level vibration table is systematically modeled and a discrete mathematical model is obtained;

[0060] Constructing a cost function through the discretized mathematical model;

[0061] 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 seven-level converter;

[0062] According to the expression, a set of input voltages is obtained through SPWM modulation so that the output voltage of the seven-level vibration table power supply is closest to the expected value.

[0063] like Figure 2 As shown, in this part, the present invention obtains the input voltage value of the present invention by constructing a cost function and taking the derivative of the cost function to obtain 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 of the present invention:

[0064]

[0065] in, is the voltage reference value of the filter capacitor C at time k+2, V C (k+2) is the predicted voltage value of the filter capacitor C at time k+2.

[0066] By discretizing equation (2), the present invention obtains:

[0067]

[0068] Where T s It is the sampling period of the whole system, including output voltage, inverter current and output current.

[0069] Assume that the load current does not change suddenly during the sampling period:

[0070] i O (k+1)≈i O (k)(6)

[0071] 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 consideration. To simplify the calculation, considering that the load current will not change suddenly and can be approximated within one cycle, the present invention obtains the load voltage at the k+2 moment by combining equations 2, 4, and 5:

[0072]

[0073] 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, the present invention finds the first-order derivative and the second-order derivative of the cost function, and 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 input voltage required by the present invention. The present invention finds the partial derivative of the input voltage and obtains:

[0074]

[0075] Combining equations 7 and 8, the present invention obtains an equation for input voltage:

[0076]

[0077] Through linear interpolation, the present invention obtains:

[0078]

[0079] Substituting this into equation (9):

[0080]

[0081] Where V ab represents the voltage between the two output ports a and b of the seven-level converter, L represents the value of the first filter inductor or the second filter inductor, V C Represents the voltage of filter capacitor C, i C represents the current flowing through the filter capacitor C, C represents the filter capacitor, i L represents the current flowing through the first filter inductor and the second filter inductor, i O Represents the current flowing through the load, T s is the sampling period, is the voltage reference value of the filter capacitor C, and k represents the time.

[0082] Through the above equation, SPWM can be used to control the input voltage.

[0083] Furthermore, the present invention also verifies the correctness of the theory by establishing a simulation model. The study found that the proposed strategy can output a voltage waveform with a certain quality under various load conditions, and the THD values ​​are 0.24% and 0.51% 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.

[0084] Compared with the traditional topology, the present invention proposes a new seven-level vibration table power supply topology, and its design significantly optimizes the parameter configuration of the filter inductor. The filter inductance value required by this topology is only one-third of the filter inductance value of the traditional single-phase two-level converter, which effectively reduces the volume and cost of the inductor and shows good application potential in renewable energy power generation systems. In addition, the present invention adopts a model predictive control (MPC) strategy to further improve the stability, efficiency and power quality of the power supply system by optimizing the cost function and determining the optimal input index. This control method generates a high-quality output voltage waveform, providing more accurate and efficient power support for the vibration test system.

[0085] 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 seven-level vibration table power supply, characterized in that: include: A first capacitor, a second capacitor, a seven-level converter, a first filter inductor, a second filter inductor, and a filter capacitor; wherein the seven-level converter is connected across the positive and negative electrodes of a DC power supply, and the first capacitor and the second capacitor are connected in series and connected across the positive and negative electrodes of the DC power supply; The first filter inductor, the filter capacitor and the second filter inductor are sequentially connected in series and then connected between the two output ports of the seven-level converter, and the load is connected in parallel to both ends of the filter capacitor.

2. A seven-level vibration table power supply according to claim 1, characterized in that: The seven-level converter includes a first switch tube, a second switch tube, a third switch tube, a fourth switch tube, a fifth switch tube, a sixth switch tube, a seventh switch tube, an eighth switch tube, and a third capacitor.

3. A seven-level vibration table power supply according to claim 2, characterized in that: The first switch tube, the second switch tube, the fifth switch tube, and the sixth switch tube are insulated gate bipolar transistors, and the third switch tube, the fourth switch tube, the seventh switch tube, and the eighth switch tube are bidirectional switch triodes; wherein, The source of the first switch tube is connected to the drain of the second switch tube and the first filter inductor, and the point where the source of the first switch tube is connected to the drain of the second switch tube serves as a first output port; The first main electrode of the third switch tube is connected to the positive electrode of the DC power supply, and the second main electrode is connected to the drain of the first switch tube; The first main electrode of the fourth switch tube is connected to the negative electrode of the DC power supply, and the second main electrode is connected to the source electrode of the second switch tube; The drain of the fifth switch tube is connected to the positive electrode of the DC power supply, and the source is connected to the source of the second switch tube; The source of the sixth switch tube is connected to the negative electrode of the DC power supply, and the drain is connected to the drain of the first switch tube; The first main electrode of the seventh switch tube is connected to the second filter inductor and the second output port, and the second main electrode is connected to the drain of the first switch tube; The first main electrode of the eighth switch tube is connected to the second filter inductor and the second output port, and the second main electrode is connected to the source of the second switch tube; the second output port is where the first capacitor is connected to the second capacitor; One end of the third capacitor is connected to the drain of the first switch tube, and the other end is connected to the source of the second switch tube.

4. A seven-level vibration table power supply according to claim 2 or 3, characterized in that: Through different switch combinations, the seven-level vibration table power supply outputs 32V DC 、V DC , 12V DC , 0, -12V DC , -V DC 、-32V DC Seven levels and eight switching states, where V DC is the voltage of the DC power supply.

5. A seven-level vibration table power supply according to claim 4, characterized in that: Among the eight switch states, the third capacitor is in a discharging state in state 1, state 2, and state 8, the third capacitor is in a charging state in state 3 and state 6, and the third capacitor is not affected in state 4, state 5, and state 7.

6. A seven-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 seven-level vibration table power supply according to any one of claims 1 to 6, characterized in that: The steps include: The power supply topology of the seven-level vibration table 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 seven-level converter; According to the expression, a set of input voltages is obtained through SPWM modulation so that the output voltage of the seven-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: in, is the voltage reference value of the filter capacitor C at time k+2, V C (k+2) is the predicted voltage value of the filter capacitor C at time k+2.

9. The method according to claim 7, characterized in that: The expression is: Where V ab represents the voltage between the two output ports a and b of the seven-level converter, L represents the value of the first filter inductor or the second filter inductor, V C Represents the voltage of filter capacitor C, i C represents the current flowing through the filter capacitor C, C represents the filter capacitor, i L represents the current flowing through the first filter inductor and the second filter inductor, i O Represents the current flowing through the load, T s is the sampling period, V C * is the voltage reference value of the filter capacitor C, and k represents the time.

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