Power electronic transformer prediction control method and device

Abstract

The invention belongs to the technical field of power electronic transformers, and particularly relates to a power electronic transformer prediction control method and device, and the method comprises the steps: collecting the intermediate DC side voltage of each cascade unit in a power electronic traction transformer; obtaining a power increment reference value of the cascaded H-bridge converter by using the intermediate direct current side voltage of each cascaded unit; according to the power increment reference value of the cascaded H-bridge converter, determining the modulation voltage of the H-bridge converter in each cascade unit and the phase shift value of the dual-active bridge converter in each cascade unit; and controlling the dual-active bridge converter of each cascade unit of the H-bridge converter of each cascade unit based on the modulation voltage of the H-bridge converter in each cascade unit and the phase shift value of the dual-active bridge converter in each cascade unit. According to the technical scheme provided by the invention, voltage balance and power balance of each unit of the power electronic transformer are guaranteed, the voltage of the middle direct current side is stable, and the dynamic characteristics of the system are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic transformers, and particularly relates to a predictive control method and device for a power electronic transformer. Background Art

[0002] A power electronic transformer is a power conversion device that realizes high-voltage and high-power electric energy transmission through technologies such as unit cascading technology, high-frequency link technology, and power electronics technology and has electrical isolation performance. The concept of a power electronic transformer has a long history. With the gradual in-depth research of different institutions and scholars at home and abroad, the application fields of power electronic transformers have been continuously broadened and are widely used in many fields such as smart distribution networks and rail transit traction.

[0003] A power electronic transformer is composed of a cascaded H-bridge converter and multiple isolated DC / DC converters, and can convert high-voltage AC electric energy into medium- and low-voltage DC electric energy. The control objective of the power electronic transformer control system is to ensure the stability of the system output voltage and the intermediate DC side voltage, maintain the input unity power factor, the balance of the intermediate DC side voltages of each unit, and the balance of the transmission powers of each unit. However, the current control method still adopts a separate control strategy, and the control of the H-bridge is independent of the control of the isolated DC / DC converter. Traditional proportional-integral controllers or proportional-resonant controllers are used, and the control effect is average, with problems such as slow dynamic response speed, steady-state error, unbalanced voltages of each unit, unstable intermediate DC side voltage, and unbalanced powers of each unit. Therefore, a new control method is needed to control the power electronic transformer to solve the above problems. Summary of the Invention

[0004] To overcome at least to some extent the problems existing in the related art, the present application provides a predictive control method and device for a power electronic transformer.

[0005] According to the first aspect of the embodiments of the present application, a predictive control method for a power electronic transformer is provided. The topological structure involved in the method includes: a plurality of cascaded units connected in parallel; each cascaded unit includes: an H-bridge converter and a dual-active-bridge converter connected in parallel; all the H-bridge converters are cascaded, and the first H-bridge converter in the cascade and the last H-bridge converter in the cascade are respectively connected to the traction network;

[0006] The predictive control method for the power electronic transformer includes:

[0007] Collect the intermediate DC side voltages of each cascaded unit in the power electronic traction transformer;

[0008] Utilize the intermediate DC side voltages of each cascaded unit to obtain the power increment reference value of the cascaded H-bridge converter;

[0009] Determine the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift value of the dual-active-bridge converter in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter;

[0010] Control the H-bridge converter of each cascaded unit and the dual-active-bridge converter of each cascaded unit respectively based on the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift value of the dual-active-bridge converter in each cascaded unit.

[0011] Preferably, the H-bridge converter includes: a four-quadrant converter and a first capacitor connected in parallel; the four-quadrant converter includes: a first bridge arm and a second bridge arm; the first bridge arm, the second bridge arm and the first capacitor are connected in parallel in sequence;

[0012] Both the first bridge arm and the second bridge arm include: two switching devices connected in series; the connection point of the two switching devices in the first bridge arm is the midpoint of the first bridge arm, and the connection point of the two switching devices in the second bridge arm is the midpoint of the second bridge arm;

[0013] The midpoint of the first bridge arm of the first H-bridge converter for cascading is connected to one end of the traction network through a first inductor, and the midpoint of the second bridge arm of the last H-bridge converter for cascading is connected to the other end of the traction network;

[0014] The midpoint of the second bridge arm of each H-bridge converter for cascading is connected to the midpoint of the first bridge arm of the next H-bridge converter for cascading.

[0015] Preferably, the dual-active-bridge converter includes: a transformer, a primary full-bridge circuit and a secondary full-bridge circuit; the primary full-bridge circuit includes: a third bridge arm and a fourth bridge arm; the secondary full-bridge circuit includes: a fifth bridge arm and a sixth bridge arm;

[0016] Each bridge arm in each full-bridge circuit includes: two switching devices connected in series; the connection point of the two switching devices in the third bridge arm is the midpoint of the third bridge arm, the connection point of the two switching devices in the fourth bridge arm is the midpoint of the fourth bridge arm, the connection point of the two switching devices in the fifth bridge arm is the midpoint of the fifth bridge arm, and the connection point of the two switching devices in the sixth bridge arm is the midpoint of the sixth bridge arm;

[0017] One end of the primary side of the transformer is connected to the midpoint of the third bridge arm, and the other end is connected to the midpoint of the fourth bridge arm;

[0018] One end of the secondary side of the transformer is connected to the midpoint of the fifth bridge arm, and the other end is connected to the midpoint of the sixth bridge arm.

[0019] Preferably, the dual-active-bridge converter further includes: a second inductor and a second capacitor;

[0020] One end of the second inductor is connected to one end of the primary side of the transformer, and the other end is connected to the midpoint of the third bridge arm;

[0021] The second capacitor is connected in parallel across both ends of the sixth bridge arm;

[0022] One ends of the second capacitors in each dual-active-bridge converter are connected to each other, and the other ends of the second capacitors in each dual-active-bridge converter are connected to each other.

[0023] Preferably, obtaining the power increment reference value of the cascaded H-bridge converter by using the intermediate DC side voltage of each cascaded unit includes:

[0024] Calculating the total DC side voltage of all cascaded units according to the intermediate DC side voltage of each cascaded unit;

[0025] Subtracting the total DC side voltage of all cascaded units from the intermediate DC side total voltage reference value to obtain a first difference;

[0026] After passing through a first proportional-integral controller, the first difference obtains the power increment reference value of the cascaded H-bridge converter.

[0027] Preferably, determining the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift value of the dual-active-bridge converter in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter includes:

[0028] Collecting the output voltage of the power electronic traction transformer;

[0029] Subtracting the output voltage of the power electronic traction transformer from the output voltage reference value to obtain a second difference;

[0030] After passing through a second proportional-integral controller, the second difference is superimposed on the power increment reference value of the cascaded H-bridge converter to obtain the power command of the dual-active-bridge converter;

[0031] Using the intermediate DC side voltage of each cascaded unit to obtain the power increment commands of the dual-active-bridge converters in the first n-1 cascaded units, where n is the total number of cascaded units;

[0032] Using the power command of the dual-active-bridge converter and the power increment commands of the dual-active-bridge converters in the first n-1 cascaded units to determine the phase-shift values of the dual-active-bridge converters in each cascaded unit.

[0033] Preferably, obtaining the power increment commands of the dual-active-bridge converters in the first n-1 cascaded units by using the intermediate DC side voltage of each cascaded unit includes:

[0034] Subtract the average value of the intermediate DC side voltage from the intermediate DC side voltages of the previous n - 1 cascaded units to obtain a third difference value;

[0035] After passing through a third proportional-integral controller, the third difference value gives the power increment command for the bidirectional active bridge converters in the previous n - 1 cascaded units.

[0036] Preferably, determining the phase-shift values of the bidirectional active bridge converters in each cascaded unit by using the power command of the bidirectional active bridge converter and the power increment commands of the bidirectional active bridge converters in the previous n - 1 cascaded units includes:

[0037] Divide the power command of the bidirectional active bridge converter by the total number n of cascaded units, and then subtract the power increment commands of the bidirectional active bridge converters in the previous n - 1 cascaded units to obtain the power reference values of the previous n - 1 cascaded units, where n is the total number of cascaded units;

[0038] Subtract the sum of the power reference values of the previous n - 1 cascaded units from the power command of the bidirectional active bridge converter to obtain the power reference value of the nth cascaded unit;

[0039] Using the power reference values of each cascaded unit, the intermediate DC side voltages of each cascaded unit, and the output voltage of the power electronic traction transformer as the inputs of the three-phase-shift predictive control strategy of the bidirectional active bridge converter to obtain the phase-shift values of the bidirectional active bridge converters in each cascaded unit.

[0040] Preferably, the phase-shift values of the bidirectional active bridge converters in each cascaded unit include:

[0041] The phase-shift angle between the drive signal of the third bridge arm and the drive signal of the fifth bridge arm of the bidirectional active bridge converter in each cascaded unit, the phase-shift angle between the drive signal of the third bridge arm and the drive signal of the fourth bridge arm of the bidirectional active bridge converter in each cascaded unit, and the phase-shift angle between the drive signal of the third bridge arm and the drive signal of the sixth bridge arm of the bidirectional active bridge converter in each cascaded unit.

[0042] Preferably, according to the power increment reference value of the cascaded H-bridge converter, determining the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift values of the bidirectional active bridge converters in each cascaded unit further includes:

[0043] Collect the traction network side voltage and traction network side current;

[0044] Based on the traction network side voltage and traction network side current, obtain the active power of the cascaded H-bridge converter and the reactive power of the cascaded H-bridge converter;

[0045] Obtain the modulation voltages of the H-bridge converters in each cascaded unit by using the power increment reference value of the cascaded H-bridge converter, the active power of the cascaded H-bridge converter, and the reactive power of the cascaded H-bridge converter.

[0046] Preferably, obtaining the active power of the cascaded H-bridge converter and the reactive power of the cascaded H-bridge converter based on the traction network side voltage and the traction network side current includes:

[0047] The fundamental component of the traction network side voltage and the quadrature-axis component of the traction network side voltage are obtained by passing the traction network side voltage through a first second-order generalized integrator;

[0048] The fundamental component of the traction network side current and the quadrature-axis component of the traction network side current are obtained by passing the traction network side current through a second second-order generalized integrator;

[0049] The active power of the cascaded H-bridge converter and the reactive power of the cascaded H-bridge converter are respectively calculated by using the fundamental component of the traction network side voltage, the quadrature-axis component of the traction network side voltage, the fundamental component of the traction network side current, and the quadrature-axis component of the traction network side current.

[0050] Preferably, obtaining the modulation voltages of the H-bridge converters in each cascaded unit by using the power increment reference value of the cascaded H-bridge converter, the active power of the cascaded H-bridge converter, and the reactive power of the cascaded H-bridge converter includes:

[0051] Obtain the control variables of the H-bridge converters in each cascaded unit by using the power increment reference value of the cascaded H-bridge converter;

[0052] Taking the control variables of the H-bridge converters in each cascaded unit, the active power of the cascaded H-bridge converter divided by the total number n of cascaded units, and the reactive power of the cascaded H-bridge converter divided by the total number n of cascaded units as the inputs of the predictive control method of the cascaded H-bridge to obtain the modulation voltages of the H-bridge converters in each cascaded unit.

[0053] Preferably, obtaining the control variables of the H-bridge converters in each cascaded unit by using the power increment reference value of the cascaded H-bridge converter includes:

[0054] After dividing the power increment reference value of the cascaded H-bridge converter by the total number n of cascaded units, superimpose the power increment commands of the bi-directional active bridge converters in the first n - 1 cascaded units to obtain the control variables of the H-bridge converters in the first n - 1 cascaded units;

[0055] After dividing the power increment reference value of the cascaded H-bridge converter by the total number n of cascaded units and subtracting the sum of the power reference values of the first n - 1 cascaded units, the control variable of the H-bridge converter in the nth cascaded unit is obtained.

[0056] Preferably, the calculation formula for the total DC-side voltage of all cascaded units includes:

[0057]

[0058] The calculation formula for the power increment reference value of the cascaded H-bridge converter includes:

[0059] P add,CHB = PI(nu dc,ref - nu dc )

[0060] In the above formula, i ∈ [1, n], n is the total number of cascaded units; u dc,i is the intermediate DC-side voltage of the ith cascaded unit, nu dc is the total DC-side voltage of all cascaded units, P add,CHB is the power increment reference value of the cascaded H-bridge converter, PI is a proportional-integral controller, and nu dc,ref is the reference value of the intermediate DC-side total voltage.

[0061] Preferably, the calculation formula for the power command of the dual-active-bridge converter includes:

[0062] P DAB = PI(u o,ref - u o ) + P add,CHB

[0063] In the above formula, P DAB is the power command of the dual-active-bridge converter, PI is a proportional-integral controller, u o,ref is the output voltage reference value, u o is the output voltage of the power electronic traction transformer, and P add,CHB is the power increment reference value of the cascaded H-bridge converter.

[0064] Preferably, the calculation formula for the average value of the intermediate DC-side voltage includes:

[0065]

[0066] The calculation formula for the power increment command of the dual-active-bridge converter in each cascaded unit includes:

[0067] P add,i = PI(u dc,avg - u dc,i )

[0068] In the above formula, i ∈ [1, n], where n is the total number of cascaded units; P add,i is the power increment command of the dual active bridge converter in the i-th cascaded unit, u dc,avg is the average value of the intermediate DC side voltage, u dc,i is the intermediate DC side voltage of the i-th cascaded unit.

[0069] Preferably, the calculation formula for the power reference value of each cascaded unit includes:

[0070]

[0071] In the above formula, i ∈ [1, n], where n is the total number of cascaded units; P DAB,i is the power reference value of the i-th cascaded unit, P DAB,n is the power reference value of the n-th cascaded unit, P DAB is the power command of the dual active bridge converter, P add,i is the power increment command of the dual active bridge converter in the i-th cascaded unit.

[0072] Preferably, the calculation formula of the first second-order generalized integrator includes:

[0073]

[0074] The calculation formula of the second second-order generalized integrator includes:

[0075]

[0076] The calculation formula of the fundamental component of the traction network side voltage includes:

[0077] u gα = G α (s)u g

[0078] The calculation formula of the quadrature axis component of the traction network side voltage includes:

[0079] u gβ = G β (s)u g

[0080] The calculation formula of the fundamental component of the traction network side current includes:

[0081] i gα = G α (s)i g

[0082] The calculation formula of the quadrature axis component of the traction network side current includes:

[0083] igβ = G β (s)i g

[0084] In the above formula, G α (s) is the first second-order generalized integrator, G β (s) is the second second-order generalized integrator, k is the weight coefficient, w g is the fundamental angular velocity of the power grid, s is the differential operator; u gα is the fundamental component of the voltage on the traction network side, u gβ is the quadrature-axis component of the voltage on the traction network side, i gα is the fundamental component of the current on the traction network side, i gβ is the quadrature-axis component of the current on the traction network side, u g is the voltage on the traction network side, i g is the current on the traction network side.

[0085] Preferably, the calculation formula of the active power of the cascaded H-bridge converter includes:

[0086]

[0087] The calculation formula of the reactive power Q CHB of the cascaded H-bridge converter includes:

[0088]

[0089] In the above formula, P CHB is the active power of the cascaded H-bridge converter, Q CHB is the reactive power of the cascaded H-bridge converter, u gα is the fundamental component of the voltage on the traction network side, u gβ is the quadrature-axis component of the voltage on the traction network side, i gα is the fundamental component of the current on the traction network side, i gβ is the quadrature-axis component of the current on the traction network side.

[0090] According to the second aspect of the embodiments of the present application, a power electronic transformer predictive control device is provided. The topological structure involved in the device includes: a plurality of cascaded units connected in parallel; each cascaded unit includes: an H-bridge converter and a dual-active-bridge converter connected in parallel; all the H-bridge converters are cascaded, and the first H-bridge converter for cascading and the last H-bridge converter for cascading are respectively connected to the traction network;

[0091] The power electronic transformer predictive control device includes:

[0092] An acquisition unit, configured to acquire the intermediate DC-side voltage of each cascaded unit in the power electronic traction transformer;

[0093] An acquisition unit, configured to acquire a power increment reference value of the cascaded H-bridge converter by using the intermediate DC-side voltage of each cascaded unit;

[0094] A determination unit, configured to determine a modulation voltage of the H-bridge converter in each cascaded unit and a phase shift value of the dual-active-bridge converter in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter;

[0095] A control unit, configured to control the H-bridge converter of each cascaded unit and the dual-active-bridge converter of each cascaded unit respectively based on the modulation voltage of the H-bridge converter in each cascaded unit and the phase shift value of the dual-active-bridge converter in each cascaded unit.

[0096] According to a third aspect of the embodiments of the present application, there is provided a computer device, including: one or more processors;

[0097] The processor is configured to store one or more programs;

[0098] When the one or more programs are executed by the one or more processors, the power electronic transformer prediction control method as described above is implemented.

[0099] According to a fourth aspect of the embodiments of the present application, there is provided a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed, the power electronic transformer prediction control method as described above is implemented.

[0100] One or more of the above technical solutions of the present invention have at least one or more of the following beneficial effects:

[0101] The present invention provides a predictive control method and device for a power electronic transformer, including: collecting the intermediate DC side voltages of each cascaded unit in the power electronic traction transformer; using the intermediate DC side voltages of each cascaded unit to obtain the power increment reference value of the cascaded H-bridge converter; determining the modulation voltage of the H-bridge converter in each cascaded unit and the phase shift value of the dual-active-bridge converter in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter; and respectively controlling the H-bridge converters and the dual-active-bridge converters of each cascaded unit based on the modulation voltage of the H-bridge converter in each cascaded unit and the phase shift value of the dual-active-bridge converter in each cascaded unit. The present invention connects the control systems of the cascaded H-bridge converter and the dual-active-bridge converter through the power increment reference value of the cascaded H-bridge converter. The cascaded H-bridge can quickly track the power change of the dual-active bridge, effectively stabilizing the intermediate DC side voltage. Moreover, power balance is adjusted within each unit and jointly responsible by the cascaded H-bridge converter and the dual-active-bridge converter, with better stability and faster response speed. The predictive control of the dual-active-bridge converter increases the multi-output control degree and improves the control performance of the dual-active-bridge converter. The present invention ensures the voltage balance and power balance of each unit of the power electronic transformer and the stability of the intermediate DC side voltage, and improves the dynamic characteristics of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0103] Figure 1 It is a schematic diagram of the topology structure related to a predictive control method for a power electronic transformer provided by an embodiment of the present invention;

[0104] Figure 2 It is a flowchart of a predictive control method for a power electronic transformer provided by an embodiment of the present invention;

[0105] Figure 3 It is a flowchart of a predictive control method for a power electronic transformer provided by an embodiment of the present invention;

[0106] Figure 4 It is a structural block diagram of a predictive control device for a power electronic transformer provided by an embodiment of the present invention;

[0107] In the figure, 1 - cascade unit, 2 - H - bridge converter, 3 - dual - active - bridge converter, 4 - traction network, 5 - first inductor, 20 - first capacitor, 21 - first bridge arm, 22 - second bridge arm, 23 - switching device in the first bridge arm, 24 - switching device in the second bridge arm, 30 - transformer, 31 - primary full - bridge circuit, 32 - secondary full - bridge circuit, 33 - third bridge arm, 34 - fourth bridge arm, 35 - fifth bridge arm, 36 - sixth bridge arm, 37 - switching device in the third bridge arm, 38 - switching device in the fourth bridge arm, 39 - switching device in the fifth bridge arm, 40 - switching device in the sixth bridge arm, 41 - second inductor, 42 - second capacitor. Detailed implementation manners

[0108] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the following embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0109] Embodiment 1

[0110] The present invention provides a predictive control method for a power - electronic transformer 30. As Figure 1 shown, the topological structure involved in this method includes: a plurality of cascade units 1 connected in parallel; each cascade unit 1 includes: an H - bridge converter 2 and a dual - active - bridge converter 3 connected in parallel; all the H - bridge converters 2 are cascaded, and the first H - bridge converter 2 in the cascade and the last H - bridge converter 2 in the cascade are respectively connected to the traction network 4.

[0111] As Figure 2 shown, the predictive control method for the power - electronic transformer 30 includes the following steps:

[0112] Step 101: Collect the intermediate DC - side voltages of each cascade unit 1 in the power - electronic traction transformer 30.

[0113] Step 102: Use the intermediate DC - side voltages of each cascade unit 1 to obtain the power - increment reference value of the cascaded H - bridge converter 2.

[0114] Step 103: Determine the modulation voltage of the H - bridge converter 2 in each cascade unit 1 and the phase - shift value of the dual - active - bridge converter 3 in each cascade unit 1 according to the power - increment reference value of the cascaded H - bridge converter 2.

[0115] Step 104: Control the H-bridge converters 2 and the dual-active-bridge converters 3 in each cascaded unit 1 based on the modulation voltages of the H-bridge converters 2 in each cascaded unit 1 and the phase-shift values of the dual-active-bridge converters 3 in each cascaded unit 1 respectively.

[0116] Further, as Figure 1 shown, the H-bridge converter 2 includes: a four-quadrant converter and a first capacitor 20 connected in parallel; the four-quadrant converter includes: a first bridge arm 21 and a second bridge arm 22; the first bridge arm 21, the second bridge arm 22 and the first capacitor 20 are connected in parallel in sequence;

[0117] Both the first bridge arm 21 and the second bridge arm 22 include: two switching devices connected in series; the connection point of the two switching devices 24 in the first bridge arm 21 is the midpoint of the first bridge arm 21, and the connection point of the two switching devices 25 in the second bridge arm 22 is the midpoint of the second bridge arm 22;

[0118] The midpoint of the first bridge arm 21 in the first cascaded H-bridge converter 2 is connected to one end of the traction network 4 through a first inductor 5, and the midpoint of the second bridge arm 22 in the last cascaded H-bridge converter 2 is connected to the other end of the traction network 4;

[0119] The midpoint of the second bridge arm 22 in each cascaded H-bridge converter 2 is connected to the midpoint of the first bridge arm 21 in the next cascaded H-bridge converter 2.

[0120] It can be understood that the cascaded H-bridge converters 2 are formed by connecting the AC sides of multiple four-quadrant converters in series and serve as the input stage of the power electronic traction transformer 30. These four-quadrant converters jointly bear the high voltage on the input side and realize the conversion of electrical energy from high-voltage AC to DC. u g is the input voltage on the traction network 4 side, L g is the input inductor (i.e., the first inductor), R g is the line equivalent resistance, i g is the input current, C i is the support capacitor for the intermediate DC link (i.e., the first capacitor, both C1 and C in the figure are the first capacitor), u n is the voltage of the intermediate DC link, u dci is the PWM voltage at the port of the four-quadrant converter. convi is the PWM voltage at the port of the four-quadrant converter.

[0121] Further, as Figure 1 shown, the dual-active-bridge converter 3 includes: a transformer 30, a primary full-bridge circuit 31 and a secondary full-bridge circuit 32; the primary full-bridge circuit 31 includes: a third bridge arm 33 and a fourth bridge arm 34; the secondary full-bridge circuit 32 includes: a fifth bridge arm 35 and a sixth bridge arm 36;

[0122] Each arm in each full-bridge circuit includes: two switch devices connected in series; the connection point of the two switch devices 37 in the third arm 33 is the midpoint of the third arm 33, the connection point of the two switch devices 38 in the fourth arm 34 is the midpoint of the fourth arm 34, the connection point of the two switch devices 39 in the fifth arm 35 is the midpoint of the fifth arm 35, and the connection point of the two switch devices 40 in the sixth arm 36 is the midpoint of the sixth arm 36;

[0123] One end of the primary side of the transformer 30 is connected to the midpoint of the third arm 33, and the other end is connected to the midpoint of the fourth arm 34;

[0124] One end of the secondary side of the transformer 30 is connected to the midpoint of the fifth arm 35, and the other end is connected to the midpoint of the sixth arm 36.

[0125] Further, as Figure 1 shown, the dual-active-bridge converter 3 further includes: a second inductor 41 and a second capacitor 42;

[0126] One end of the second inductor 41 is connected to one end of the primary side of the transformer 30, and the other end is connected to the midpoint of the third arm 33;

[0127] The second capacitor 42 is connected in parallel across the two ends of the sixth arm 36;

[0128] One end of the second capacitor 42 in each dual-active-bridge converter 3 is connected to each other, and the other end of the second capacitor 42 in each dual-active-bridge converter 3 is connected to each other.

[0129] It can be understood that the output stage of the power electronic transformer 30 is formed by connecting multiple dual-active-bridge DC / DC converters in parallel, which has the functions of stabilizing the output DC voltage and isolating the front and rear stages. The dual-active-bridge converter 3 also has advantages such as bidirectional power flow and soft switching. The arms on the primary and secondary sides are both IGBT full-bridge circuits, and its input voltage u dci is the voltage of the intermediate DC link and also the output voltage of the cascaded H-bridge. L ri is the power transfer inductor of the dual-active-bridge converter 3 (i.e., the second inductor, L r1 and L rn are both the second inductor, i Lr1 the current of the second inductor is L r1 ), i Lrn the current of the second inductor is L rn ), and the turns ratio of the transformer 30 is k:1. The output DC voltage of the dual-active-bridge converter 3 is u o .

[0130] In some embodiments, the switch devices in the H-bridge converter 2 and the dual-active-bridge converter 3 can be, but are not limited to, IGBT switch devices.

[0131] Further, step 102 includes:

[0132] Step 1021: Calculate the total DC side voltage of all cascaded units 1 based on the intermediate DC side voltage of each cascaded unit 1;

[0133] Step 1022: Subtract the total DC side voltage of all cascaded units 1 from the intermediate DC side total voltage reference value to obtain a first difference;

[0134] Step 1023: After the first difference passes through a first proportional-integral controller, obtain the power increment reference value of the cascaded H-bridge converter 2;

[0135] Specifically, the calculation formula for the total DC side voltage of all cascaded units 1 includes:

[0136]

[0137] The calculation formula for the power increment reference value of the cascaded H-bridge converter 2 includes:

[0138] P add,CHB = PI(nu dc,ref - nu dc )

[0139] In the above formula, i ∈ [1, n], n is the total number of cascaded units 1; u dc,i is the intermediate DC side voltage of the i-th cascaded unit 1, nu dc is the total DC side voltage of all cascaded units 1, P add,CHB is the power increment reference value of the cascaded H-bridge converter 2, PI is the proportional-integral controller, and nu dc,ref is the intermediate DC side total voltage reference value.

[0140] Further, step 103 includes:

[0141] Step 1031: Collect the output voltage of the power electronic traction transformer 30;

[0142] Step 1032: Subtract the output voltage of the power electronic traction transformer 30 from the output voltage reference value to obtain a second difference;

[0143] Step 1033: After the second difference passes through a second proportional-integral controller, superimpose the power increment reference value of the cascaded H-bridge converter 2 to obtain the power command of the dual active bridge converter 3;

[0144] Specifically, the calculation formula for the power command of the dual active bridge converter 3 includes:

[0145] P DAB = PI(u o,ref - u o ) + Padd,CHB

[0146] In the above formula, P DAB is the power command of the dual-active-bridge converter 3, PI is the proportional-integral controller, u o,ref is the output voltage reference value, u o is the output voltage of the power electronic traction transformer 30, P add,CHB is the power increment reference value of the cascaded H-bridge converter 2;

[0147] Step 1034: Obtain the power increment commands of the dual-active-bridge converters 3 in the first n-1 cascaded units 1 by using the intermediate DC-side voltages of the cascaded units 1, where n is the total number of the cascaded units 1;

[0148] Step 1035: Determine the phase-shift values of the dual-active-bridge converters 3 in the cascaded units 1 by using the power commands of the dual-active-bridge converters 3 and the power increment commands of the dual-active-bridge converters 3 in the first n-1 cascaded units 1.

[0149] Further, step 1034 includes:

[0150] Step 1034a: Subtract the intermediate DC-side voltage of the first n-1 cascaded units 1 from the average value of the intermediate DC-side voltages to obtain a third difference;

[0151] Step 1034b: After passing the third difference through a third proportional-integral controller, obtain the power increment commands of the dual-active-bridge converters 3 in the first n-1 cascaded units 1;

[0152] Specifically, the calculation formula for the average value of the intermediate DC-side voltages includes:

[0153]

[0154] The calculation formula for the power increment commands of the dual-active-bridge converters 3 in the cascaded units 1 includes:

[0155] P add,i = PI(u dc,avg - u dc,i )

[0156] In the above formula, i ∈ [1, n], n is the total number of the cascaded units 1; P add,i is the power increment command of the dual-active-bridge converter 3 in the i-th cascaded unit 1, u dc,avg is the average value of the intermediate DC-side voltages, u dc,i is the intermediate DC-side voltage of the i-th cascaded unit 1.

[0157] Further, step 1035 includes:

[0158] Step 1035a: After dividing the power command of the dual-active-bridge converter 3 by the total number n of cascaded units 1, subtract the power increment commands of the dual-active-bridge converters 3 in the first n-1 cascaded units 1 to obtain the power reference values of the first n-1 cascaded units 1, where n is the total number of cascaded units 1;

[0159] Step 1035b: Subtract the sum of the power reference values of the first n-1 cascaded units 1 from the power command of the dual-active-bridge converter 3 to obtain the power reference value of the nth cascaded unit 1;

[0160] Specifically, the calculation formula for the power reference value of each cascaded unit 1 includes:

[0161]

[0162] In the above formula, i ∈ [1, n], and n is the total number of cascaded units 1; P DAB,i is the power reference value of the ith cascaded unit 1, P DAB,n is the power reference value of the nth cascaded unit 1, P DAB is the power command of the dual-active-bridge converter 3, P add,i is the power increment command of the dual-active-bridge converter 3 in the ith cascaded unit 1;

[0163] Step 1035c: Using the power reference values of each cascaded unit 1, the intermediate DC-side voltage of each cascaded unit 1, and the output voltage of the power electronic traction transformer 30 as the inputs of the three-phase-shift predictive control strategy of the dual-active-bridge converter 3, obtain the phase-shift values of the dual-active-bridge converters 3 in each cascaded unit 1.

[0164] It should be noted that the "three-phase-shift predictive control strategy of the dual-active-bridge converter 3" involved in the embodiments of the present invention is well known to those skilled in the art. Therefore, its specific implementation method will not be described in detail. For example, the relevant content of the three-phase-shift predictive control strategy of the dual-active-bridge converter 3 is recorded in the literature of the master's degree thesis "Research on the Application of Model Predictive Control in Dual-Active-Bridge Converter 3" of Beijing Jiaotong University.

[0165] Furthermore, the phase-shift values of the dual-active-bridge converters 3 in each cascaded unit 1 include:

[0166] The phase-shift angle between the driving signal of the third bridge arm 33 and the driving signal of the fifth bridge arm 35 of the dual-active-bridge converter 3 in each cascaded unit 1, the phase-shift angle between the driving signal of the third bridge arm 33 and the driving signal of the fourth bridge arm 34 of the dual-active-bridge converter 3 in each cascaded unit 1, and the phase-shift angle between the driving signal of the third bridge arm 33 and the driving signal of the sixth bridge arm 36 of the dual-active-bridge converter 3 in each cascaded unit 1.

[0167] Furthermore, step 103 also includes:

[0168] Step 1036: Collect the voltage on the 4th side of the traction network and the current on the 4th side of the traction network;

[0169] Step 1037: Based on the voltage on the 4th side of the traction network and the current on the 4th side of the traction network, obtain the active power of the cascaded H-bridge converter 2 and the reactive power of the cascaded H-bridge converter 2;

[0170] Step 1038: Use the power increment reference value of the cascaded H-bridge converter 2, the active power of the cascaded H-bridge converter 2, and the reactive power of the cascaded H-bridge converter 2 to obtain the modulation voltage of the H-bridge converter 2 in each cascaded unit 1.

[0171] Furthermore, step 1037 includes:

[0172] Step 1037a: The voltage on the 4th side of the traction network passes through a first second-order generalized integrator to obtain the fundamental component of the voltage on the 4th side of the traction network and the quadrature-axis component of the voltage on the 4th side of the traction network;

[0173] Step 1037b: The current on the 4th side of the traction network passes through a second second-order generalized integrator to obtain the fundamental component of the current on the 4th side of the traction network and the quadrature-axis component of the current on the 4th side of the traction network;

[0174] Specifically, the calculation formula of the first second-order generalized integrator includes:

[0175]

[0176] The calculation formula of the second second-order generalized integrator includes:

[0177]

[0178] The calculation formula of the fundamental component of the voltage on the 4th side of the traction network includes:

[0179] u gα =G α (s)u g

[0180] The calculation formula of the quadrature-axis component of the voltage on the 4th side of the traction network includes:

[0181] u gβ =G β (s)u g

[0182] The calculation formula of the fundamental component of the current on the 4th side of the traction network includes:

[0183] i gα =G α (s)i g

[0184] Calculation formula for the quadrature-axis component of the current on the traction network 4 side, including:

[0185] i gβ = G β (s)i g

[0186] In the above formula, G α (s) is the first second-order generalized integrator, G β (s) is the second second-order generalized integrator, k is the weighting coefficient, w g is the fundamental angular velocity of the power grid, s is the differential operator; u gα is the fundamental component of the voltage on the traction network 4 side, u gβ is the quadrature-axis component of the voltage on the traction network 4 side, i gα is the fundamental component of the current on the traction network 4 side, i gβ is the quadrature-axis component of the current on the traction network 4 side, u g is the voltage on the traction network 4 side, i g is the current on the traction network 4 side;

[0187] Step 1037c: Using the fundamental component of the voltage on the traction network 4 side, the quadrature-axis component of the voltage on the traction network 4 side, the fundamental component of the current on the traction network 4 side, and the quadrature-axis component of the current on the traction network 4 side, calculate respectively the active power of the cascaded H-bridge converter 2 and the reactive power of the cascaded H-bridge converter 2;

[0188] Specifically, the calculation formula for the active power of the cascaded H-bridge converter 2 includes:

[0189]

[0190] The calculation formula for the reactive power of the cascaded H-bridge converter 2 includes:

[0191]

[0192] In the above formula, P CHB is the active power of the cascaded H-bridge converter 2, Q CHB is the reactive power of the cascaded H-bridge converter 2, u gα is the fundamental component of the voltage on the traction network 4 side, u gβ is the quadrature-axis component of the voltage on the traction network 4 side, i gα is the fundamental component of the current on the traction network 4 side, i gβ is the quadrature-axis component of the current on the traction network 4 side.

[0193] Furthermore, step 1038 includes:

[0194] Step 1038a: Obtain the control variables of the H-bridge converters 2 in each cascaded unit 1 by using the power increment reference value of the cascaded H-bridge converter 2.

[0195] Step 1038b: Use the control variables of the H-bridge converters 2 in each cascaded unit 1, the active power of the cascaded H-bridge converter 2 divided by the total number n of cascaded units 1, and the reactive power of the cascaded H-bridge converter 2 divided by the total number n of cascaded units 1 as the inputs of the predictive control method for the cascaded H-bridge to obtain the modulation voltages of the H-bridge converters 2 in each cascaded unit 1.

[0196] It should be noted that the "predictive control method for cascaded H-bridge" involved in the embodiments of the present invention is well-known to those skilled in the art. Therefore, its specific implementation manner will not be described in detail. For example, the relevant content of the predictive control method for cascaded H-bridge is recorded in the literature named "A Simple Model Predictive Power Control Strategy for Single-Phase PWM Converters With Modulation Function Optimization" (Model Predictive Power Control for Single-Phase PWM Converters).

[0197] Further, step 1038a includes:

[0198] After dividing the power increment reference value of the cascaded H-bridge converter 2 by the total number n of cascaded units 1, superimpose the power increment commands of the dual-active-bridge converters 3 in the first n - 1 cascaded units 1 to obtain the control variables of the H-bridge converters 2 in the first n - 1 cascaded units 1.

[0199] After dividing the power increment reference value of the cascaded H-bridge converter 2 by the total number n of cascaded units 1, subtract the sum of the power reference values of the first n - 1 cascaded units 1 to obtain the control variable of the H-bridge converter 2 in the nth cascaded unit 1.

[0200] The present invention relates to a control method for a power electronic transformer 30. This method realizes the interconnection of the power of the system through the power predictive control of the front-stage cascaded H-bridge converter 2 and the predictive control of the rear-stage dual-active bridge, thereby realizing the overall power predictive control of the power electronic traction transformer 30 and simultaneously achieving the voltage balance and power balance of the system.

[0201] The present invention overcomes the disadvantages of the traditional control method such as complex design and slow system dynamic response, and has the advantages of high control accuracy, fast response speed, more stable dynamic process, and good voltage and power balance effect.

[0202] A predictive control method for a power electronic transformer 30 provided by the present invention increases the control freedom of the dual active bridge converter 3 compared with the traditional predictive control method, and improves the control accuracy of the predictive control for the dual active bridge converter 3. The linkage relationship between the H-bridge converter 2 and the dual active bridge converter 3 is increased, and the voltage balance control method simultaneously links the dual active bridge converter 3 and the H-bridge converter 2, increasing the internal power matching relationship of each independent unit. The power link of the cascaded H-bridge converter 2 and the dual active bridge converter 3 increases the response speed of the converter to load changes.

[0203] To further illustrate the above predictive control method for the power electronic transformer 30, the present invention provides a specific example, such as Figure 3 shown, including the following steps:

[0204] Step 1: Collect the intermediate DC side voltage u of each cascaded unit 1 in the power electronic traction transformer 30 dc,i ; According to the intermediate DC side voltage u of each cascaded unit 1 dc,i , calculate the total DC side voltage nu of all cascaded units 1 dc ; Use the intermediate DC side total voltage reference value nu dc,ref minus the total DC side voltage nu of all cascaded units 1 dc , to obtain the first difference; After passing through the first proportional integral controller, the first difference obtains the power increment reference value P of the cascaded H-bridge converter 2 add,CHB ;

[0205] Step 2: Collect the output voltage u of the power electronic traction transformer 30 o ; Subtract the output voltage u of the power electronic traction transformer 30 from the output voltage reference value u o,ref to obtain the second difference; After passing through the second proportional integral controller, the second difference is superimposed on the power increment reference value P of the cascaded H-bridge converter 2 o add,CHB , to obtain the power command P of the dual active bridge converter 3 DAB ;

[0206] Step 3: Subtract the intermediate DC side voltage u of the previous n - 1 cascaded units 1 from the average value u of the intermediate DC side voltage dc,avg to obtain the third difference; After passing through the third proportional integral controller, the third difference obtains the power increment command P of the dual active bridge converter 3 in the previous n - 1 cascaded units 1 dc,i to obtain the third difference; After passing through the third proportional integral controller, the third difference obtains the power increment command P of the dual active bridge converter 3 in the previous n - 1 cascaded units 1 add,i ;

[0207] Step 4: Divide the power command P of the dual active bridge converter 3 by the total number n of cascaded units 1, and then subtract the power increment command P of each dual active bridge converter 3 in the previous n - 1 cascaded units 1 DAB divided by the total number n of cascaded units 1, and then subtract the power increment command P of each dual active bridge converter 3 in the previous n - 1 cascaded units 1​add,i , the power reference value P of the first n - 1 cascaded units 1 is obtained DAB,i , where n is the total number of cascaded units 1;

[0208] The power command P of the dual - active - bridge converter 3 DAB subtracts the sum P of the power reference values P of the first n - 1 cascaded units 1 DAB,i to obtain the power reference value P of the nth cascaded unit 1 DAB,rest ; DAB,n ;

[0209] Step 5: Using the power reference value P of each cascaded unit 1 DAB,i , the intermediate DC - side voltage u of each cascaded unit 1 dc,i and the output voltage u of the power - electronic traction transformer 30 o as the inputs of the three - phase - shift predictive control strategy of the dual - active - bridge converter 3 in each cascaded unit 1, the phase - shift angles D between the drive signal of the third bridge arm 33 and the drive signal of the fifth bridge arm 35 of the dual - active - bridge converter 3 in each cascaded unit 1 are obtained i0 , the phase - shift angles D between the drive signal of the third bridge arm 33 and the drive signal of the fourth bridge arm 34 of the dual - active - bridge converter 3 in each cascaded unit 1 i1 and the phase - shift angles D between the drive signal of the third bridge arm 33 and the drive signal of the sixth bridge arm 36 of the dual - active - bridge converter 3 in each cascaded unit 1 i2 ;

[0210] Step 6: Collect the voltage u on the traction network 4 side g and the current i on the traction network 4 side g ; The voltage u on the traction network 4 side g passes through the first second - order generalized integrator to obtain the fundamental - wave component u of the voltage on the traction network 4 side gα and the quadrature - axis component u of the voltage on the traction network 4 side gβ ;

[0211] The current i on the traction network 4 side g passes through the second second - order generalized integrator to obtain the fundamental - wave component i of the current on the traction network 4 side gα and the quadrature - axis component i of the current on the traction network 4 side gβ ;

[0212] Step 7: Using the fundamental - wave component u of the voltage on the traction network 4 side gα , the quadrature - axis component u of the voltage on the traction network 4 side gβ , the fundamental - wave component i of the current on the traction network 4 side gα and the quadrature - axis component i of the current on the traction network 4 side gβ , the active power P of the cascaded H - bridge converter 2 is calculated respectively CHB and the reactive power Q of the cascaded H - bridge converter 2CHB ;

[0213] Step 8: Divide the power increment reference value P of the cascaded H-bridge converter 2 by the total number n of the cascaded units 1, and then superimpose the power increment commands P of the dual-active-bridge converters 3 in the first n-1 cascaded units 1 add,CHB to obtain the control variable P of the H-bridge converter 2 in the first n-1 cascaded units 1 add,i ; CHB,i ;

[0214] Divide the power increment reference value P of the cascaded H-bridge converter 2 by the total number n of the cascaded units 1, and then subtract the sum P of the power reference values P of the first n-1 cascaded units 1 add,CHB to obtain the control variable P of the H-bridge converter 2 in the nth cascaded unit 1 DAB,i ; DAB,rest ; CHB,n ;

[0215] Step 9: Use the control variables of the H-bridge converters 2 in each cascaded unit 1, the active power P of the cascaded H-bridge converter 2 divided by the total number n of the cascaded units 1 CHB and the reactive power Q of the cascaded H-bridge converter 2 divided by the total number n of the cascaded units 1 as the inputs of the predictive control method of the cascaded H-bridge to obtain the modulation voltage u of the H-bridge converter 2 in each cascaded unit 1 CHB ; mdt,i ;

[0216] Step 10: Based on the modulation voltage u of the H-bridge converter 2 in each cascaded unit 1 mdt,i and the phase-shift values D of the dual-active-bridge converters 3 in each cascaded unit 1 i0 , D i1 , D i2 , respectively control the H-bridge converters 2 and the dual-active-bridge converters 3 of each cascaded unit 1 in each cascaded unit 1.

[0217] The present invention connects the control systems of the cascaded H-bridge converter 2 and the dual-active-bridge converter through the power command P add,CHB . The cascaded H-bridge can quickly track the power changes of the dual-active-bridge and effectively stabilize the intermediate DC-side voltage; the power balance of the present invention is adjusted inside each unit and is jointly responsible by the CHB and the DAB, with better stability and faster response speed; the predictive control of the DAB in the present invention increases the multi-output control degree and improves the control performance of the DAB converter.

[0218] Embodiment 2

[0219] The present invention provides a predictive control device for a power electronic transformer 30, as Figure 4As shown in the figure, the topological structure involved in the device includes: a plurality of cascaded units 1 connected in parallel; each cascaded unit 1 includes: an H-bridge converter 2 and a dual-active-bridge converter 3 connected in parallel; all the H-bridge converters 2 are cascaded, and the first H-bridge converter 2 in cascade and the last H-bridge converter 2 in cascade are respectively connected to the traction network 4;

[0220] The predictive control device of the power electronic transformer 30 includes:

[0221] An acquisition unit for acquiring the intermediate DC-side voltage of each cascaded unit 1 in the power electronic traction transformer 30;

[0222] An obtaining unit for obtaining the power increment reference value of the cascaded H-bridge converter 2 by using the intermediate DC-side voltage of each cascaded unit 1;

[0223] A determination unit for determining the modulation voltage of the H-bridge converter 2 in each cascaded unit 1 and the phase-shift value of the dual-active-bridge converter 3 in each cascaded unit 1 according to the power increment reference value of the cascaded H-bridge converter 2;

[0224] A control unit for respectively controlling the H-bridge converter 2 of each cascaded unit 1 and the dual-active-bridge converter 3 of each cascaded unit 1 based on the modulation voltage of the H-bridge converter 2 in each cascaded unit 1 and the phase-shift value of the dual-active-bridge converter 3 in each cascaded unit 1.

[0225] Further, the H-bridge converter 2 includes: a four-quadrant converter and a first capacitor 20 connected in parallel; the four-quadrant converter includes: a first bridge arm 21 and a second bridge arm 22; the first bridge arm 21, the second bridge arm 22 and the first capacitor 20 are connected in parallel in sequence;

[0226] Both the first bridge arm 21 and the second bridge arm 22 include: two switching devices connected in series; the connection point of the two switching devices in the first bridge arm 21 is the midpoint of the first bridge arm 21, and the connection point of the two switching devices in the second bridge arm 22 is the midpoint of the second bridge arm 22;

[0227] The midpoint of the first bridge arm 21 in the first H-bridge converter 2 in cascade is connected to one end of the traction network 4 through a first inductor 5, and the midpoint of the second bridge arm 22 in the last H-bridge converter 2 in cascade is connected to the other end of the traction network 4;

[0228] The midpoint of the second bridge arm 22 in each cascaded H-bridge converter 2 is connected to the midpoint of the first bridge arm 21 in the next cascaded H-bridge converter 2.

[0229] Further, the dual-active-bridge converter 3 includes: a transformer 30, a primary full-bridge circuit 31, and a secondary full-bridge circuit 32; the primary full-bridge circuit 31 includes: a third bridge arm 33 and a fourth bridge arm 34; the secondary full-bridge circuit 32 includes: a fifth bridge arm 35 and a sixth bridge arm 36;

[0230] Each bridge arm in each full-bridge circuit includes: two serially-connected switching devices; the connection point of the two switching devices in the third bridge arm 33 is the midpoint of the third bridge arm 33, the connection point of the two switching devices in the fourth bridge arm 34 is the midpoint of the fourth bridge arm 34, the connection point of the two switching devices in the fifth bridge arm 35 is the midpoint of the fifth bridge arm 35, and the connection point of the two switching devices in the sixth bridge arm 36 is the midpoint of the sixth bridge arm 36;

[0231] One end of the primary side of the transformer 30 is connected to the midpoint of the third bridge arm 33, and the other end is connected to the midpoint of the fourth bridge arm 34;

[0232] One end of the secondary side of the transformer 30 is connected to the midpoint of the fifth bridge arm 35, and the other end is connected to the midpoint of the sixth bridge arm 36.

[0233] Further, the dual-active-bridge converter 3 further includes: a second inductor 41 and a second capacitor 42;

[0234] One end of the second inductor 41 is connected to one end of the primary side of the transformer 30, and the other end is connected to the midpoint of the third bridge arm 33;

[0235] The second capacitor 42 is connected in parallel across the two ends of the sixth bridge arm 36;

[0236] One ends of the second capacitors 42 in each dual-active-bridge converter 3 are connected to each other, and the other ends of the second capacitors 42 in each dual-active-bridge converter 3 are connected to each other.

[0237] Further, the acquisition unit includes:

[0238] A first calculation module, configured to calculate the total DC-side voltage of all cascaded units 1 according to the intermediate DC-side voltage of each cascaded unit 1;

[0239] A first acquisition module, configured to subtract the total DC-side voltage of all cascaded units 1 from the intermediate DC-side voltage reference value to obtain a first difference;

[0240] A second acquisition module, configured to obtain the power increment reference value of the cascaded H-bridge converter 2 after the first difference passes through a first proportional-integral controller.

[0241] Further, the determination unit includes:

[0242] A first acquisition module, configured to acquire the output voltage of the power electronic traction transformer 30;

[0243] A third acquisition module, configured to subtract the output voltage of the power electronic traction transformer 30 from the output voltage reference value to obtain a second difference value;

[0244] A fourth acquisition module, configured to, after the second difference value passes through a second proportional-integral controller, superimpose a power increment reference value of the cascaded H-bridge converter 2 to obtain a power command of the dual-active-bridge converter 3;

[0245] A fifth acquisition module, configured to use the intermediate DC side voltage of each cascaded unit 1 to obtain a power increment command of the dual-active-bridge converter 3 in the first n-1 cascaded units 1, where n is the total number of cascaded units 1;

[0246] A first determination module, configured to use the power command of the dual-active-bridge converter 3 and the power increment commands of the dual-active-bridge converter 3 in the first n-1 cascaded units 1 to determine a phase-shift value of the dual-active-bridge converter 3 in each cascaded unit 1.

[0247] Further, the fifth acquisition module includes:

[0248] A first acquisition sub-module, configured to subtract the intermediate DC side voltage of the first n-1 cascaded units 1 from the average value of the intermediate DC side voltage to obtain a third difference value;

[0249] A second acquisition sub-module, configured to, after the third difference value passes through a third proportional-integral controller, obtain a power increment command of the dual-active-bridge converter 3 in the first n-1 cascaded units 1.

[0250] Further, the first determination module includes:

[0251] A third acquisition sub-module, configured to divide the power command of the dual-active-bridge converter 3 by the total number n of cascaded units 1, and then subtract the power increment commands of the dual-active-bridge converter 3 in the first n-1 cascaded units 1 to obtain a power reference value of the first n-1 cascaded units 1, where n is the total number of cascaded units 1;

[0252] A fourth acquisition sub-module, configured to subtract the sum of the power reference values of the first n-1 cascaded units 1 from the power command of the dual-active-bridge converter 3 to obtain a power reference value of the nth cascaded unit 1;

[0253] A fifth acquisition sub-module, configured to use the power reference values of each cascaded unit 1, the intermediate DC side voltage of each cascaded unit 1, and the output voltage of the power electronic traction transformer 30 as inputs of a three-phase phase-shift prediction control strategy of the dual-active-bridge converter 3 to obtain a phase-shift value of the dual-active-bridge converter 3 in each cascaded unit 1.

[0254] Further, the phase-shift value of the dual-active-bridge converter 3 in each cascaded unit 1 includes:

[0255] The phase shift angles between the driving signals of the third bridge arm 33 and the fifth bridge arm 35 of the dual active bridge converter 3 in each cascaded unit 1, the phase shift angles between the driving signals of the third bridge arm 33 and the fourth bridge arm 34 of the dual active bridge converter 3 in each cascaded unit 1, and the phase shift angles between the driving signals of the third bridge arm 33 and the sixth bridge arm 36 of the dual active bridge converter 3 in each cascaded unit 1.

[0256] Further, the determination unit further includes:

[0257] A second acquisition module for acquiring the voltage on the traction network 4 side and the current on the traction network 4 side;

[0258] A sixth acquisition module for obtaining the active power of the cascaded H-bridge converter 2 and the reactive power of the cascaded H-bridge converter 2 based on the voltage on the traction network 4 side and the current on the traction network 4 side;

[0259] A seventh acquisition module for obtaining the modulation voltage of the H-bridge converter 2 in each cascaded unit 1 by using the power increment reference value of the cascaded H-bridge converter 2, the active power of the cascaded H-bridge converter 2, and the reactive power of the cascaded H-bridge converter 2.

[0260] Further, the sixth acquisition module includes:

[0261] A sixth acquisition sub-module for obtaining the fundamental component of the voltage on the traction network 4 side and the quadrature-axis component of the voltage on the traction network 4 side after the voltage on the traction network 4 side passes through a first second-order generalized integrator;

[0262] A seventh acquisition sub-module for obtaining the fundamental component of the current on the traction network 4 side and the quadrature-axis component of the current on the traction network 4 side after the current on the traction network 4 side passes through a second second-order generalized integrator;

[0263] A calculation sub-module for respectively calculating the active power of the cascaded H-bridge converter 2 and the reactive power of the cascaded H-bridge converter 2 by using the fundamental component of the voltage on the traction network 4 side, the quadrature-axis component of the voltage on the traction network 4 side, the fundamental component of the current on the traction network 4 side, and the quadrature-axis component of the current on the traction network 4 side.

[0264] Further, the seventh acquisition module includes:

[0265] An eighth acquisition sub-module for obtaining the control variables of the H-bridge converter 2 in each cascaded unit 1 by using the power increment reference value of the cascaded H-bridge converter 2;

[0266] The ninth acquisition sub-module is configured to use the control variables of the H-bridge converters 2 in each cascaded unit 1, the active power of the cascaded H-bridge converters 2 divided by the total number n of the cascaded units 1, and the reactive power of the cascaded H-bridge converters 2 divided by the total number n of the cascaded units 1 as the input of the predictive control method for the cascaded H-bridge, and acquire the modulation voltage of the H-bridge converters 2 in each cascaded unit 1.

[0267] Further, the eighth acquisition sub-module is specifically configured to:

[0268] After dividing the power increment reference value of the cascaded H-bridge converters 2 by the total number n of the cascaded units 1, superimpose the power increment commands of the bi-directional active bridge converters 3 in the first n-1 cascaded units 1 to obtain the control variables of the H-bridge converters 2 in the first n-1 cascaded units 1;

[0269] After dividing the power increment reference value of the cascaded H-bridge converters 2 by the total number n of the cascaded units 1, subtract the sum of the power reference values of the first n-1 cascaded units 1 to obtain the control variables of the H-bridge converters 2 in the nth cascaded unit 1.

[0270] Further, the calculation formula for the total DC-side voltage of all cascaded units 1 includes:

[0271]

[0272] The calculation formula for the power increment reference value of the cascaded H-bridge converters 2 includes:

[0273] P add,CHB =PI(nu dc,ref -nu dc )

[0274] In the above formula, i ∈ [1, n], n is the total number of cascaded units 1; u dc,i is the intermediate DC-side voltage of the i-th cascaded unit 1, nu dc is the total DC-side voltage of all cascaded units 1, P add,CHB is the power increment reference value of the cascaded H-bridge converters 2, PI is a proportional-integral controller, and nu dc,ref is the reference value of the intermediate DC-side total voltage.

[0275] Further, the calculation formula for the power command of the bi-directional active bridge converter 3 includes:

[0276] P DAB =PI(u o,ref -u o )+P add,CHB

[0277] In the above formula, P DABis the power command of the dual active bridge converter 3, PI is the proportional integral controller, u o,ref is the output voltage reference value, u o is the output voltage of the power electronic traction transformer 30, P add,CHB is the power increment reference value of the cascaded H-bridge converter 2.

[0278] Furthermore, the calculation formula of the average value of the intermediate DC side voltage includes:

[0279]

[0280] The calculation formula of the power increment command of the dual active bridge converter 3 in each cascaded unit 1 includes:

[0281] P add,i = PI(u dc,avg - u dc,i )

[0282] In the above formula, i ∈ [1, n], n is the total number of cascaded units 1; P add,i is the power increment command of the dual active bridge converter 3 in the i-th cascaded unit 1, u dc,avg is the average value of the intermediate DC side voltage, u dc,i is the intermediate DC side voltage of the i-th cascaded unit 1.

[0283] Furthermore, the calculation formula of the power reference value of each cascaded unit 1 includes:

[0284]

[0285] In the above formula, i ∈ [1, n], n is the total number of cascaded units 1; P DAB,i is the power reference value of the i-th cascaded unit 1, P DAB,n is the power reference value of the n-th cascaded unit 1, P DAB is the power command of the dual active bridge converter 3, P add,i is the power increment command of the dual active bridge converter 3 in the i-th cascaded unit 1.

[0286] Furthermore, the calculation formula of the first second-order generalized integrator includes:

[0287]

[0288] The calculation formula of the second second-order generalized integrator includes:

[0289]

[0290] The calculation formula of the fundamental component of the voltage on the traction network 4 side includes:

[0291] ugα = G α (s)u g

[0292] The calculation formula for the virtual-axis component of the voltage on the 4th side of the traction network includes:

[0293] u gβ = G β (s)u g

[0294] The calculation formula for the fundamental component of the current on the 4th side of the traction network includes:

[0295] i gα = G α (s)i g

[0296] The calculation formula for the virtual-axis component of the current on the 4th side of the traction network includes:

[0297] i gβ = G β (s)i g

[0298] In the above formula, G α (s) is the first second-order generalized integrator, G β (s) is the second second-order generalized integrator, k is the weighting coefficient, w g is the fundamental angular velocity of the power grid, s is the differential operator; u gα is the fundamental component of the voltage on the 4th side of the traction network, u gβ is the virtual-axis component of the voltage on the 4th side of the traction network, i gα is the fundamental component of the current on the 4th side of the traction network, i gβ is the virtual-axis component of the current on the 4th side of the traction network, u g is the voltage on the 4th side of the traction network, i g is the current on the 4th side of the traction network.

[0299] Furthermore, the calculation formula for the active power of the cascaded H-bridge converter 2 includes:

[0300]

[0301] The reactive power Q CHB of the cascaded H-bridge converter 2, the calculation formula includes:

[0302]

[0303] In the above formula, P CHB is the active power of the cascaded H-bridge converter 2, Q CHB is the reactive power of the cascaded H-bridge converter 2, u gα is the fundamental component of the voltage on the 4th side of the traction network, ugβ is the quadrature-axis component of the voltage on the traction network side 4, i gα is the fundamental component of the current on the traction network side 4, i gβ is the quadrature-axis component of the current on the traction network side 4.

[0304] It can be understood that the device embodiments provided above correspond to the method embodiments above, and the corresponding specific contents can be referred to each other, which will not be elaborated here.

[0305] It can be understood that the same or similar parts in the above embodiments can be referred to each other, and the content not described in detail in some embodiments can be seen in the same or similar content in other embodiments.

[0306] Embodiment III

[0307] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory. The memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of a power electronic transformer predictive control method in the above embodiments.

[0308] Embodiment IV

[0309] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in a computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and this storage space stores the operating system of the terminal. And, in this storage space, there are also stored one or more instructions suitable for being loaded and executed by the processor. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The one or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the steps of a power electronic transformer predictive control method in the above-mentioned embodiments.

[0310] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0311] The present invention is described with reference to the flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, as well as the combination of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or multiple flows and / or blocks

[0312] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the functions in Figure 1 one or more of the flows Figure 1The functions specified in one or more boxes.

[0313] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide for implementing the steps of the functions specified in Figure 1 one process or more processes and / or boxes Figure 1 the functions specified in one box or more boxes.

[0314] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A predictive control method for a power electronic transformer, characterized in that, The topological structure involved in the method includes: multiple cascaded units connected in parallel; each cascaded unit includes: an H-bridge converter and a dual-active-bridge converter connected in parallel; all the H-bridge converters are cascaded, and the first H-bridge converter in the cascade and the last H-bridge converter in the cascade are respectively connected to the traction network; The predictive control method for the power electronic transformer includes: Collecting the intermediate DC-side voltages of each cascaded unit in the power electronic traction transformer; Using the intermediate DC-side voltages of each cascaded unit to obtain the reference value of the power increment of the cascaded H-bridge converter; According to the reference value of the power increment of the cascaded H-bridge converter, determining the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift value of the dual-active-bridge converter in each cascaded unit; Controlling the H-bridge converter of each cascaded unit and the dual-active-bridge converter of each cascaded unit respectively based on the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift value of the dual-active-bridge converter in each cascaded unit.

2. The method according to claim 1, wherein The H-bridge converter includes: a four-quadrant converter and a first capacitor connected in parallel; the four-quadrant converter includes: a first bridge arm and a second bridge arm; the first bridge arm, the second bridge arm, and the first capacitor are connected in parallel in sequence; Both the first bridge arm and the second bridge arm include: two switching devices connected in series; the connection point of the two switching devices in the first bridge arm is the midpoint of the first bridge arm, and the connection point of the two switching devices in the second bridge arm is the midpoint of the second bridge arm; The midpoint of the first bridge arm in the first H-bridge converter in the cascade is connected to one end of the traction network through a first inductor, and the midpoint of the second bridge arm in the last H-bridge converter in the cascade is connected to the other end of the traction network; The midpoint of the second bridge arm in each H-bridge converter in the cascade is connected to the midpoint of the first bridge arm in the next H-bridge converter in the cascade.

3. The method according to claim 2, wherein The dual-active-bridge converter includes: a transformer, a primary full-bridge circuit, and a secondary full-bridge circuit; the primary full-bridge circuit includes: a third bridge arm and a fourth bridge arm; the secondary full-bridge circuit includes: a fifth bridge arm and a sixth bridge arm; Each bridge arm in each full-bridge circuit includes: two switching devices connected in series; the connection point of the two switching devices in the third bridge arm is the midpoint of the third bridge arm, the connection point of the two switching devices in the fourth bridge arm is the midpoint of the fourth bridge arm, the connection point of the two switching devices in the fifth bridge arm is the midpoint of the fifth bridge arm, and the connection point of the two switching devices in the sixth bridge arm is the midpoint of the sixth bridge arm; One end of the primary side of the transformer is connected to the midpoint of the third bridge arm, and the other end is connected to the midpoint of the fourth bridge arm; One end of the secondary side of the transformer is connected to the midpoint of the fifth bridge arm, and the other end is connected to the midpoint of the sixth bridge arm.

4. The method according to claim 3, wherein The dual-active-bridge converter further includes: a second inductor and a second capacitor; One end of the second inductor is connected to one end of the primary side of the transformer, and the other end is connected to the midpoint of the third bridge arm; The second capacitor is connected in parallel across the two ends of the sixth bridge arm; One end of the second capacitor in each dual-active-bridge converter is interconnected, and the other end of the second capacitor in each dual-active-bridge converter is interconnected.

5. The method according to claim 1, wherein The obtaining of the power increment reference value of the cascaded H-bridge converter by using the intermediate DC side voltage of each cascaded unit includes: Calculating the total DC side voltage of all cascaded units according to the intermediate DC side voltage of each cascaded unit; Subtracting the total DC side voltage of all cascaded units from the intermediate DC side voltage reference value to obtain a first difference; After passing through a first proportional-integral controller, the first difference obtains the power increment reference value of the cascaded H-bridge converter.

6. The method according to claim 1, characterized in that The determining of the modulation voltage of the H-bridge converter in each cascaded unit and the phase-shift value of the dual-active-bridge converter in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter includes: Collecting the output voltage of the power electronic traction transformer; Subtracting the output voltage of the power electronic traction transformer from the output voltage reference value to obtain a second difference; After passing through a second proportional-integral controller, the second difference is superimposed on the power increment reference value of the cascaded H-bridge converter to obtain the power command of the dual-active-bridge converter; Using the intermediate DC side voltage of each cascaded unit to obtain the power increment command of the dual-active-bridge converter in the first n-1 cascaded units, where n is the total number of cascaded units; Using the power command of the dual-active-bridge converter and the power increment commands of the dual-active-bridge converters in the first n-1 cascaded units to determine the phase-shift values of the dual-active-bridge converters in each cascaded unit.

7. The method according to claim 6, characterized in that The obtaining of the power increment command of the dual-active-bridge converter in the first n-1 cascaded units by using the intermediate DC side voltage of each cascaded unit includes: Subtracting the intermediate DC side voltage of the first n-1 cascaded units from the average value of the intermediate DC side voltage to obtain a third difference; After passing through a third proportional-integral controller, the third difference obtains the power increment command of the dual-active-bridge converter in the first n-1 cascaded units.

8. The method according to claim 6, characterized in that, The determining of the phase-shift values of the dual-active-bridge converters in each cascaded unit by using the power command of the dual-active-bridge converter and the power increment commands of the dual-active-bridge converters in the first n-1 cascaded units includes: Dividing the power command of the dual-active-bridge converter by the total number n of cascaded units and then subtracting the power increment commands of the dual-active-bridge converters in the first n-1 cascaded units to obtain the power reference values of the first n-1 cascaded units, where n is the total number of cascaded units; Subtracting the sum of the power reference values of the first n-1 cascaded units from the power command of the dual-active-bridge converter to obtain the power reference value of the nth cascaded unit; Taking the power reference values of each cascaded unit, the intermediate DC side voltage of each cascaded unit, and the output voltage of the power electronic traction transformer as the inputs of the three-phase-shift predictive control strategy of the dual-active-bridge converter to obtain the phase-shift values of the dual-active-bridge converters in each cascaded unit.

9. The method according to claim 3, wherein The phase-shift values of the dual-active-bridge converters in each cascaded unit include: The phase shift angles between the driving signals of the third bridge arm and the fifth bridge arm of the dual-active-bridge converter in each cascaded unit, the phase shift angles between the driving signals of the third bridge arm and the fourth bridge arm of the dual-active-bridge converter in each cascaded unit, and the phase shift angles between the driving signals of the third bridge arm and the sixth bridge arm of the dual-active-bridge converter in each cascaded unit.

10. The method according to claim 1, wherein The determining the modulation voltages of the H-bridge converters in each cascaded unit and the phase shift values of the dual-active-bridge converters in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter further includes: Collecting the traction network side voltage and the traction network side current; Based on the traction network side voltage and the traction network side current, obtaining the active power of the cascaded H-bridge converter and the reactive power of the cascaded H-bridge converter; Using the power increment reference value of the cascaded H-bridge converter, the active power of the cascaded H-bridge converter, and the reactive power of the cascaded H-bridge converter to obtain the modulation voltages of the H-bridge converters in each cascaded unit.

11. The method according to claim 10, characterized in that The obtaining the active power of the cascaded H-bridge converter and the reactive power of the cascaded H-bridge converter based on the traction network side voltage and the traction network side current includes: The traction network side voltage passes through a first second-order generalized integrator to obtain the fundamental component of the traction network side voltage and the quadrature-axis component of the traction network side voltage; The traction network side current passes through a second second-order generalized integrator to obtain the fundamental component of the traction network side current and the quadrature-axis component of the traction network side current; Using the fundamental component of the traction network side voltage, the quadrature-axis component of the traction network side voltage, the fundamental component of the traction network side current, and the quadrature-axis component of the traction network side current to calculate the active power of the cascaded H-bridge converter and the reactive power of the cascaded H-bridge converter respectively.

12. The method according to claim 10, wherein The obtaining the modulation voltages of the H-bridge converters in each cascaded unit using the power increment reference value of the cascaded H-bridge converter, the active power of the cascaded H-bridge converter, and the reactive power of the cascaded H-bridge converter includes: Using the power increment reference value of the cascaded H-bridge converter to obtain the control variables of the H-bridge converters in each cascaded unit; Taking the control variables of the H-bridge converters in each cascaded unit, the active power of the cascaded H-bridge converter divided by the total number n of cascaded units, and the reactive power of the cascaded H-bridge converter divided by the total number n of cascaded units as the inputs of the predictive control method of the cascaded H-bridge to obtain the modulation voltages of the H-bridge converters in each cascaded unit.

13. The method according to claim 12, wherein The obtaining the control variables of the H-bridge converters in each cascaded unit using the power increment reference value of the cascaded H-bridge converter includes: Dividing the power increment reference value of the cascaded H-bridge converter by the total number n of cascaded units and then superimposing the power increment commands of the dual-active-bridge converters in the previous n - 1 cascaded units to obtain the control variables of the H-bridge converters in the previous n - 1 cascaded units; After dividing the power increment reference value of the cascaded H-bridge converter by the total number n of cascaded units and subtracting the sum of the power reference values of the first n - 1 cascaded units, the control variable of the H-bridge converter in the nth cascaded unit is obtained.

14. The method according to claim 5, wherein The calculation formula for the total DC-side voltage of all cascaded units includes: The calculation formula for the power increment reference value of the cascaded H-bridge converter includes: P add,CHB = PI(nu dc,ref - nu dc ) In the above formula, i ∈ [1, n], where n is the total number of cascaded units; u dc,i is the intermediate DC-side voltage of the i-th cascaded unit, nu dc is the total DC-side voltage of all cascaded units, P add,CHB is the reference value of the power increment of the cascaded H-bridge converter, PI is the proportional-integral controller, nu dc,ref is the reference value of the total intermediate DC-side voltage.

15. The method according to claim 6, wherein The calculation formula for the power command of the dual-active-bridge converter includes: P DAB = PI(u o,ref - u o ) + P add,CHB In the above formula, P DAB is the power command of the dual active bridge converter, PI is the proportional integral controller, u o,ref is the output voltage reference value, u o is the output voltage of the power electronic traction transformer, P add,CHB is the power increment reference value of the cascaded H-bridge converter.

16. The method according to claim 7, characterized in that, The calculation formula for the average value of the intermediate DC-side voltage includes: The calculation formula for the power increment command of the dual-active-bridge converter in each cascaded unit includes: P add,i = PI(u dc,avg - u dc,i ) In the above formula, \(i\in[1,n]\), where \(n\) is the total number of cascaded units; \(P\) add,i is the power increment command of the dual-active-bridge converter in the \(i\)-th cascaded unit, \(u\) dc,avg is the average value of the intermediate DC-side voltage, \(u\) dc,i is the intermediate DC-side voltage of the \(i\)-th cascaded unit.

17. The method according to claim 8, characterized in that The calculation formula for the power reference value of each cascaded unit includes: In the above formula, \(i\in[1,n]\), where \(n\) is the total number of cascaded units; \(P\) DAB,i is the power reference value of the \(i\)-th cascaded unit, \(P\) DAB,n is the power reference value of the \(n\)-th cascaded unit, \(P\) DAB is the power command of the dual-active-bridge converter, \(P\) add,i is the power increment command of the dual-active-bridge converter in the \(i\)-th cascaded unit.

18. The method according to claim 11, wherein The calculation formula for the first second-order generalized integrator includes: The calculation formula for the second second-order generalized integrator includes: The calculation formula for the fundamental component of the traction network side voltage includes: u gα = G α (s)u g The calculation formula for the quadrature-axis component of the traction network side voltage includes: u gβ = G β (s)u g The calculation formula for the fundamental component of the traction network side current includes: i gα = G α (s)i g The calculation formula for the quadrature-axis component of the traction network side current includes: i gβ = G β (s)i g In the above formula, G α (s) is the first second-order generalized integrator, G β (s) is the second second-order generalized integrator, k is the weighting coefficient, w g is the fundamental angular velocity of the power grid, s is the differential operator; u gα is the fundamental component of the voltage on the traction network side, u gβ is the quadrature-axis component of the voltage on the traction network side, i gα is the fundamental component of the current on the traction network side, i gβ is the quadrature-axis component of the current on the traction network side, u g is the voltage on the traction network side, i g is the current on the traction network side.

19. The method according to claim 11, characterized in that, The calculation formula for the active power of the cascaded H-bridge converter includes: The reactive power Q of the cascaded H-bridge converter CHB The calculation formula includes: In the above formula, P CHB is the active power of the cascaded H-bridge converter, Q CHB is the reactive power of the cascaded H-bridge converter, u gα is the fundamental component of the traction network side voltage, u gβ is the quadrature-axis component of the traction network side voltage, i gα is the fundamental component of the traction network side current, i gβ is the quadrature-axis component of the traction network side current.

20. A predictive control device for a power electronic transformer, characterized in that, The topological structure involved in the device includes: a plurality of cascaded units connected in parallel; each cascaded unit includes: an H-bridge converter and a dual-active-bridge converter connected in parallel; all H-bridge converters are cascaded, and the first H-bridge converter in the cascade and the last H-bridge converter in the cascade are respectively connected to the traction network; The power electronic transformer predictive control device includes: An acquisition unit for acquiring the intermediate DC-side voltage of each cascaded unit in the power electronic traction transformer; An obtaining unit for obtaining the power increment reference value of the cascaded H-bridge converter by using the intermediate DC-side voltage of each cascaded unit; A determination unit for determining the modulation voltage of the H-bridge converter in each cascaded unit and the phase shift value of the dual-active-bridge converter in each cascaded unit according to the power increment reference value of the cascaded H-bridge converter; A control unit for respectively controlling the H-bridge converter of each cascaded unit and the dual-active-bridge converter of each cascaded unit based on the modulation voltage of the H-bridge converter in each cascaded unit and the phase shift value of the dual-active-bridge converter in each cascaded unit.

21. A computer device, characterized in that, Includes: One or more processors; The processor is used to store one or more programs; When the one or more programs are executed by the one or more processors, the power electronic transformer predictive control method described in any one of claims 1 to 19 is implemented.

22. A computer-readable storage medium, characterized in that, There is a computer program stored thereon, and when the computer program is executed, the power electronic transformer predictive control method described in any one of claims 1 to 19 is implemented.

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