High-power traction power supply bidirectional converter control method, device, system and medium

Abstract

The present invention discloses a control method and device, system and medium for a high-power traction power supply bidirectional converter. The method comprises: collecting the AC three-phase grid voltage and the AC side three-phase current of each parallel converter, and calculating the predicted values ​​of active current, reactive current and midpoint voltage through coordinate transformation; defining the three-phase unbalanced current of the parallel converter according to the collected AC side three-phase current of each parallel converter, and obtaining the predicted values ​​of active current, reactive current and midpoint voltage through coordinate transformation; defining the three-phase unbalanced current of the parallel converter according to the collected AC side three-phase current of each parallel converter, and obtaining the predicted values ​​of active current, reactive current and midpoint voltage through coordinate transformation; dq The active component and reactive component of the uneven current in the coordinate system; construct a cost function based on the predicted values ​​of the active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current; obtain the optimal switching state by optimizing the cost function. The present invention improves the rapidity of control system adjustment through model predictive control, enhances the stability of the system, reduces the complexity of the system, and has a wide market demand.

Description

Technical Field

[0001] The present invention belongs to the field of subway power supply systems, and in particular relates to a control method and device, a system and a medium for a high-power traction power supply bidirectional converter. Background Art

[0002] The subway power supply system is an important part of urban rail transit, and its power supply mode is DC power supply. In this system, the function of the converter is to convert AC power into DC power to meet the power demand of the subway train, and when the subway train decelerates and brakes, the converter can feed energy back to the power grid, so it is also called a bidirectional converter. Due to the large power demand of the bidirectional converter, a high-power converter is required in the rail transit traction power supply, generally with a rated power of more than 3MW and a peak power of more than 6MW.

[0003] Limited by the safe working area of ​​power electronic devices, high-power converters are often expanded in parallel. However, parallel connection of converters will cause power imbalance, which not only affects the stability of the system, but also reduces the life of power semiconductor devices, seriously affecting the reliability of bidirectional converters. In order to solve the problem of uneven current caused by parallel connection of converters, the prior art usually adopts the same current setting method, that is, the parallel converters use the same current setting in the hope of obtaining the same current feedback. However, due to the accuracy error of the detection link of the parallel converter and the difference in resistance and inductance parameters, such as slight differences in the inductance of the reactor, and even different resistances of the cable connectors, the parallel converter will cause uneven current.

[0004] Therefore, how to solve the problem of uneven current caused by parallel connection of high-power converters is an urgent problem to be solved in the current field of subway high-power power supply. Summary of the invention

[0005] The object of the present invention is to provide a high-power traction power supply bidirectional converter control method and device, system and medium to solve the above-mentioned problems.

[0006] The present invention is implemented according to the following technical solutions:

[0007] In a first aspect, the present invention provides a high-power traction power supply bidirectional converter control method, the method is applicable to a three-level converter topology, and the method comprises:

[0008] The three-phase grid voltage on the AC side and the three-phase current on the AC side of each parallel converter are collected and converted into The state equation of the component current is obtained;

[0009] The predicted values ​​of active current, reactive current and midpoint voltage are obtained by discretizing the state equation of current;

[0010] The three-phase unbalanced current of the parallel converter is defined according to the three-phase current of the AC side of each parallel converter, and the coordinate transformation is used to obtain Active and reactive components of unequal current in the coordinate system;

[0011] A cost function is constructed according to the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current;

[0012] Calculate the cost function values ​​corresponding to all switch states, and take the switch state that minimizes the cost function value as the optimal switch state;

[0013] The on / off state of the semiconductor switch device of each parallel converter is controlled in each control cycle according to the optimal switch state, thereby realizing the current sharing control of the bidirectional converter.

[0014] In one embodiment, the three-phase AC grid voltage and the three-phase AC current of each parallel converter are collected and converted into The state equations for component acquisition current include:

[0015] The collected three-phase AC grid voltage and the three-phase AC current of each parallel converter are The coordinate transformation formula is converted to Quantity;

[0016] [ e d e q ] = 2 3 [ cos i cos( i − 2 π 3 ) cos( i + 2 π 3 ) − sin i − sin( i − 2 π 3 ) − sin( i + 2 π 3 ) ] [ e a e b e c ] = C 3 s / 2 r [ e a e b e c ] ,

[0017] [ i d x i qx ] = 2 3 [ cos i cos( i − 2 π 3 ) cos( i + 2 π 3 ) − sin i − sin( i − 2 π 3 ) − sin( i + 2 π 3 ) ] [ i axe i bx i cx ] = C 3 s / 2 r [ i axe i bx i cx ] ,

[0018] In the formula, is the rotation angle of the grid voltage, , The grid voltage Quantity, , , is the three-phase grid voltage; , The grid current Quantity, , , is the three-phase current on the AC side of the parallel converter, Represents the number of the parallel-connected converter, ∈{1,2…};

[0019] Calculate the AC side voltage of each parallel converter corresponding to the switch state at the previous moment Component; AC side voltage of each parallel converter Serving size:

[0020] [ u dx u qx ] = C 3s / 2 r × 1 2 u dcx [ S axe S bx S cx ]

[0021] In the formula, , is the voltage on the AC side of the parallel converter Quantity, represents the number of the parallel converter, x∈{1,2…}, is the DC side voltage of the parallel converter, , , are the switching states of the parallel converters respectively;

[0022] The grid voltage and current Components and AC side voltage of parallel converters The state equation of the component current is:

[0023] L d dt [ i d x i qx ] = [ e d e q ] + oh L [ i qx − i dx ] − R [ i dx i qx ] − [ u dx u qx ] ,

[0024] In the formula, is the grid-side inductance value, is the grid angular frequency, is the equivalent resistance value of the grid-side filter.

[0025] In one embodiment, the predicted values ​​of active current and reactive current are obtained by discretizing the state equation of the current:

[0026] [ i d x ( k + 1 ) i qx ( k + 1 ) ] = ( 1 − T s R L ) [ i dx ( k ) i qx ( k ) ] + T s L [ e d ( k ) − u dx ( k ) e q ( k ) − u qx ( k ) ] ,

[0027] In the formula, is the predicted value of active current, is the predicted value of reactive current, is the grid-side inductance value, is the filter equivalent resistance value, To control the cycle, , for The grid current at the moment Quantity, , for The AC side voltage of the parallel converter at the moment Quantity, , for The grid voltage at the moment Quantity;

[0028] The predicted value of the midpoint voltage is:

[0029] ,

[0030] In the formula, is the predicted value of the midpoint voltage, , is the DC side midpoint current and midpoint voltage of the parallel converter at time k, , are the upper and lower bus capacitances of the three-level converter, Represents the number of the parallel-connected converter, ∈{1,2…}.

[0031] In one implementation, the three-phase unbalanced current of the parallel converter is defined according to the collected three-phase current of the AC side of each parallel converter as:

[0032] [ ] T ,

[0033] Phase unequal current , Phase unequal current and Phase unequal current They are:

[0034] ,

[0035] In the formula, , , , , , is the three-phase current on the AC side of the parallel converter;

[0036] After coordinate transformation, we get The active and reactive components of the unequal current in the coordinate system are:

[0037] [ d id d iq ] = C 3 s / 2 r [ d yes d ib d ic ] ,

[0038] In the formula, is the active component of the unequal current, is the reactive component of the unequal current, is the coordinate transformation formula.

[0039] In one implementation, in order to achieve control of unbalanced current and avoid the design of weight coefficients of unbalanced current optimization items, a cost function is constructed based on the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the unbalanced current: , where To consider the active current command after the uneven current, is the reactive current instruction after considering the uneven current; is the active current instruction after considering the uneven current , reactive power instruction , obtained by using the active current given value, the reactive current given value and the active component and reactive component of the unbalanced current; the active current given value and the reactive current given value are obtained by using the DC side voltage regulator and the reactive power regulator respectively; is the weight coefficient of the midpoint potential under a single weight coefficient, is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage.

[0040] In one embodiment, the active current instruction after considering the uneven current , reactive current command for:

[0041] [ i dx * ′ i qx * ′ ] = [ i dx * i qx * ] + ( − 1 ) x [ d id d iq ] ,

[0042] In the formula, is the active current given, is the reactive current given, is the active component of the unequal current, is the reactive component of the unequal current, Represents the number of the parallel-connected converter, ∈{1,2…}.

[0043] In one implementation, in order to achieve separate control of the active component and reactive component of the uneven current, a cost function is constructed based on the predicted values ​​of the active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current:

[0044] ,

[0045] In the formula, is the active current given, is the reactive current given, is the weight coefficient of the midpoint voltage under multiple weight coefficients, is the weight coefficient of the active component of the unequal current, is the weight coefficient of the reactive component of the uneven current, which is adjusted by To achieve the control of the midpoint voltage, by adjusting To achieve the control of the active component of the uneven current, by adjusting Realize the control of reactive component of uneven current; is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage; , are the allowable variation ranges of active current and reactive current unequal flow conditions, is the active component of the unequal current, is the reactive component of the unequal current;

[0046] The allowable variation range of the active current and reactive current unequal current situation , The setting is based on:

[0047] For the application scenario where the grid-side power factor is 1, the reactive current is controlled near zero. > ;

[0048] For the application scenario of reactive power compensation, > .

[0049] In a second aspect, the present invention provides a high-power traction power supply bidirectional converter control device, the device comprising: a prediction value module for collecting the AC three-phase grid voltage and the AC side three-phase current of each parallel converter, and converting it into The state equation of the current is obtained by the component, and the state equation of the current is discretized to obtain the predicted values ​​of the active current, reactive current and midpoint voltage;

[0050] The three-phase unbalanced current component acquisition module is used to define the three-phase unbalanced current of the parallel converter according to the collected three-phase current on the AC side of each parallel converter, and obtain the Active and reactive components of unequal current in the coordinate system;

[0051] A cost function module is used to construct a cost function according to the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current;

[0052] The optimization module is used to calculate the cost function values ​​corresponding to all switch states, and take the switch state that minimizes the cost function value as the optimal switch state. According to the optimal switch state, the on and off states of the semiconductor switch devices of each parallel converter are controlled within their respective control cycles, thereby realizing the current sharing control of the bidirectional converter.

[0053] In a third aspect, the present invention provides a high-power traction power supply bidirectional converter control system, comprising: at least two of the above-mentioned high-power traction power supply bidirectional converter control devices, and one high-power traction power supply bidirectional converter control device is correspondingly connected to a bidirectional converter.

[0054] In a fourth aspect, the present invention provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned high-power traction power supply bidirectional converter control method are implemented.

[0055] Beneficial effects of the present invention:

[0056] The present invention solves the current tracking control and midpoint potential control of the three-level converter topology through model predictive control, and realizes the control of the rectifier; and realizes the control of the current sharing of the converters in parallel by introducing the unequal current optimization item of the parallel converters in the cost function of the model predictive control; and realizes the high-power application of the traction power supply by realizing the parallel connection of the bidirectional converters in the traction power supply application; the present invention improves the stability and reliability of the system, increases the life of the power semiconductor device, and ensures the reliability of the high-power traction power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the accompanying drawings described below are only some embodiments. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0058] Figure 1 It is a three-level bidirectional converter topology;

[0059] Figure 2 A flow chart of a high-power traction power supply bidirectional converter control method provided by an embodiment of the present invention;

[0060] Figure 3 A block diagram of active current and reactive current calculation provided in one embodiment of the present invention;

[0061] Figure 4 A schematic structural diagram of a high-power traction power supply bidirectional converter control device provided in one embodiment of the present invention.

[0062] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0063] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0064] In traction power supply applications, in order to achieve power expansion of bidirectional converters, parallel connection is often used for capacity expansion. In order to solve the power imbalance problem caused by parallel connection of converters, a high-power traction power supply bidirectional converter control method is proposed. This method is aimed at the three-level bidirectional converter topology. Its topology structure is as follows: Figure 1 shown.

[0065] like Figure 2 As shown, the embodiment of the present disclosure provides a high-power traction power supply bidirectional converter control method, and the control method specifically includes the following steps:

[0066] Step S100: Collect the three-phase grid voltage on the AC side and the three-phase current on the AC side of each parallel converter, and convert them into The state equation of the current is obtained by using the components.

[0067] First, the AC three-phase voltage and the AC side three-phase current of each parallel converter are sampled and obtained. , , is the three-phase current on the AC side of the 1# parallel converter, , , The three-phase current on the AC side of the 2# parallel converter is recorded as , , .

[0068] Secondly, the collected three-phase AC grid voltage and the three-phase AC current of each parallel converter are The coordinate transformation formula is converted to Component, the conversion formula is as follows:

[0069] [ e d e q ] = 2 3 [ cos i cos( i − 2 π 3 ) cos( i + 2 π 3 ) − sin i − sin( i − 2 π 3 ) − sin( i + 2 π 3 ) ] [ e a e b e c ] = C 3 s / 2 r [ e a e b e c ] ,

[0070] [ i d x i qx ] = 2 3 [ cos i cos( i − 2 π 3 ) cos( i + 2 π 3 ) − sin i − sin( i − 2 π 3 ) − sin( i + 2 π 3 ) ] [ i axe i bx i cx ] = C 3 s / 2 r [ i axe i bx i cx ] ,

[0071] In the formula, is the rotation angle of the grid voltage, , The grid voltage Quantity, , , is the three-phase grid voltage; , The grid current Quantity, , , is the three-phase AC current of the parallel converter, Represents the number of the parallel-connected converter, ∈{1,2…}, is the coordinate transformation formula;

[0072] C 3 s / 2 r = 2 3 [ cos i cos( i − 2 π 3 ) cos( i + 2 π 3 ) − sin i − sin( i − 2 π 3 ) − sin( i + 2 π 3 ) ] .

[0073] Calculate the AC side voltage of each parallel converter corresponding to the switch state at the previous moment Component; AC side voltage of each parallel converter Serving size:

[0074] [ u dx u qx ] = C 3s / 2 r × 1 2 u dcx [ S axe S bx S cx ]

[0075] In the formula, , is the voltage on the AC side of the parallel converter Quantity, Represents the number of the parallel-connected converter, ∈{1,2…}, is the DC side voltage of the parallel converter, , , They are the switching states of the parallel converters, respectively. The coordinate transformation is converted to Quantity.

[0076] The grid voltage and grid current Components and AC side voltage of parallel converters The state equation of the component current is:

[0077] L d dt [ i d x i qx ] = [ e d e q ] + oh L [ i qx − i dx ] − R [ i dx i qx ] − [ u dx u qx ] ,

[0078] is the grid-side inductance value, is the grid angular frequency, is the equivalent resistance value of the grid-side filter.

[0079] Step S200: Obtain predicted values ​​of active current, reactive current and midpoint voltage by discretizing the state equation of the current.

[0080] Furthermore, the predicted values ​​of active current, reactive current and midpoint voltage are:

[0081] [ i d x ( k + 1 ) i qx ( k + 1 ) ] = ( 1 − T s R L ) [ i dx ( k ) i qx ( k ) ] + T s L [ e d ( k ) − u dx ( k ) e q ( k ) − u qx ( k ) ] ,

[0082] In the formula, is the predicted value of active current, is the predicted value of reactive current, is the grid-side inductance value, is the filter equivalent resistance value, To control the cycle, , for The grid current at the moment Quantity, , for The AC side voltage of the parallel converter at the moment Quantity, , for The grid voltage at the moment Quantity.

[0083] The predicted value of the midpoint voltage at time k+1 is:

[0084] ,

[0085] In the formula, is the predicted value of the midpoint voltage, , For parallel converters The midpoint current and midpoint voltage of the DC side at the moment, , are the upper and lower bus capacitances of the three-level converter, Represents the number of the parallel-connected converter, ∈{1,2…}.

[0086] Step S300: define the three-phase unbalanced current of the parallel converter according to the collected three-phase current of the AC side of each parallel converter, and obtain the three-phase unbalanced current of the parallel converter through coordinate transformation. The active and reactive components of the unequal current in the coordinate system.

[0087] like Figure 1 As shown, the three-phase AC current of the parallel converter is obtained , , , , , .

[0088] Furthermore, in the three-phase coordinate system, the three-phase unbalanced current of the parallel converter is defined as follows according to the collected three-phase current of the AC side of each parallel converter:

[0089] [ ] T ,

[0090] Phase unequal current , Phase unequal current and Phase unequal current They are:

[0091] ,

[0092] In the formula, , , , , , is the three-phase current on the AC side of the parallel converter.

[0093] After coordinate transformation, we can get The active and reactive components of the unequal current in the coordinate system are:

[0094] [ d id d iq ] = C 3 s / 2 r [ d yes d ib d ic ] ,

[0095] In the formula, is the active component of the unequal current, is the reactive component of the unequal current, is the coordinate transformation formula.

[0096] Step S400: constructing a cost function according to the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current.

[0097] Model predictive control has the characteristics of multi-objective optimization, and realizes rolling optimization of optimization targets by establishing a cost function with multiple optimization targets. The present invention utilizes this characteristic to design a model predictive control based on uneven current optimization.

[0098] In order to achieve the control of unbalanced current and avoid the design of weight coefficients of unbalanced current optimization items. In one embodiment, a cost function for introducing unbalanced current factors is provided, and the cost function established by introducing active and reactive components of unbalanced current is:

[0099] ,

[0100] In the formula, To consider the active current command after the uneven current, is the reactive current instruction after considering the uneven current; is the active current instruction after considering the uneven current , reactive power instruction , obtained by using the active current given value, the reactive current given value and the active component and reactive component of the unbalanced current; the active current given value and the reactive current given value are obtained by using the DC side voltage regulator and the reactive power regulator respectively; is the weight coefficient of the midpoint potential under a single weight coefficient, is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage.

[0101] In the above cost function J, the current command , To consider the active current and reactive current instructions after the uneven current flow, they are obtained by the following formula:

[0102] [ i dx * ′ i qx * ′ ] = [ i dx * i qx * ] + ( − 1 ) x [ d id d iq ] ,

[0103] In the formula, To consider the active current command after the uneven current, To consider the active current command after the uneven current, is the active current given, is the reactive current given, is the active component of the unequal current, is the reactive component of the unequal current, Represents the number of the parallel-connected converter, ∈{1,2…}.

[0104] Active current set value and reactive current setpoint , respectively obtained by using the DC side voltage regulator and reactive power regulator.

[0105] In the double closed-loop control system, the outer loop of active current setting and reactive current setting calculation is composed of DC voltage regulator and reactive power regulator. The DC voltage regulator is composed of PI regulator in the outer loop 1, and the input is DC voltage command. With DC voltage The feedback difference, the DC voltage regulator output is the active current given value The reactive power regulator is in the outer loop 2 and is also composed of a PI regulator. The input is the reactive power given Reactive Power The difference in feedback, the reactive power regulator output is the reactive current given value . Figure 3This is the block diagram of the active current and reactive current calculation link.

[0106] It should be noted that the above-mentioned outer ring 1 and outer ring 2 and other related technologies are all existing technologies and will not be described in detail here.

[0107] In order to achieve separate control of the active component and reactive component of the uneven current, in another embodiment, another cost function for introducing uneven current factor is provided, and by directly introducing uneven current into the cost function, the optimization of uneven current between converters is intuitively reflected.

[0108] In order to achieve separate control of the active and reactive components of the uneven current, the following cost function is established for the three-level converter considering the influence of the midpoint potential:

[0109] ,

[0110] In the formula, is the active current given, is the reactive current given, is the weight coefficient of the midpoint voltage under multiple weight coefficients, is the weight coefficient of the active component of the unequal current, is the weight coefficient of the reactive component of the uneven current, which is adjusted by To achieve the control of the midpoint voltage, by adjusting To achieve the control of the active component of the uneven current, by adjusting Realize the control of reactive component of uneven current; is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage; , are the allowable variation ranges of active current and reactive current unequal flow conditions, is the active component of the unequal current, is the reactive component of the unequal current;

[0111] For the application scenario where the grid-side power factor is 1, the reactive current is controlled near zero, while the active current fluctuates greatly. The allowed fluctuation range is larger. The fluctuation range is small, and The constraint is more stringent, that is, > In the application scenario of reactive power compensation, the reactive current fluctuation is larger than the active current. The allowed fluctuation range is larger. The fluctuation range is small, and The constraint is more stringent, that is, > .

[0112] Therefore, the allowable range of variation of active current and reactive current unequal flow is summarized as follows: , The settings are based on:

[0113] For the application scenario where the grid-side power factor is 1, the reactive current is controlled near zero. > ;

[0114] For the application scenario of reactive power compensation, > .

[0115] This embodiment adjusts The midpoint voltage can be controlled by adjusting It can realize the control of the active component of uneven current by adjusting The reactive component of the uneven current can be controlled.

[0116] In a preferred embodiment, in order to reduce the difficulty of debugging the weight coefficient, , Can be configured to the same value, , Can be configured to the same value.

[0117] This embodiment can allow the uneven current to fluctuate within a certain range, and in particular, the active component and the reactive component of the uneven current can be controlled separately, so that the system has higher flexibility.

[0118] Step S500: Calculate the cost function values ​​corresponding to all switch states, and take the switch state that minimizes the cost function value as the optimal switch state.

[0119] In the embodiment of the present application, the process of step S600 includes:

[0120] Calculate the AC side voltage of each parallel converter corresponding to the 27 switch states Quantity , , as follows:

[0121] [ u dx u qx ] = C 3s / 2 r × 1 2 u dcx [ S axe S bx S cx ] ,

[0122] In the formula, , is the voltage on the AC side of the parallel converter Quantity, Represents the number of the parallel-connected converter, ∈{1,2…}, is the DC side voltage of each parallel converter, , , are the switching states of each parallel converter, respectively. The coordinate transformation is converted to Quantity.

[0123] The components corresponding to different switch states , Substitute into the following formula to obtain the predicted values ​​of active current and reactive current corresponding to different switch states:

[0124] [ i dx ( k + 1 ) i qx ( k + 1 ) ] = ( 1 − T s R L ) [ i dx ( k ) i qx ( k ) ] + T s L [ e d ( k ) − u dx ( k ) e q ( k ) − u qx ( k ) ] ,

[0125] The predicted values ​​of active current and reactive current corresponding to different switch states are brought into the cost function to obtain an array of cost function values ​​corresponding to different switch states, which is named J array;

[0126] By comparing, the switch state corresponding to the minimum value in the J array is obtained as the code The optimal switching state of the converter ].

[0127] Switch status[[ ] is composed of 1 or 0, representing the on or off command of the semiconductor device. The optimal switching state is transmitted to the driver board of the semiconductor device to control the on or off of the semiconductor device.

[0128] Step S600: Control the on / off state of the semiconductor switch device of each parallel converter in each control cycle according to the optimal switching state, thereby realizing current sharing control of the bidirectional converter.

[0129] This embodiment adopts model predictive control, introduces converter current sharing optimization items, and implements optimized control of converter current sharing through rolling optimization of the cost function.

[0130] The present invention can be widely used in application fields such as subway power supply systems, power electronics technology, and control system optimization. With the development of urban rail transit, the demand for subway power supply systems is increasing day by day, and the present invention proposes to solve the problem of uneven current through an algorithm, which can not only improve the stability of the system, but also reduce the complexity of the system, and has a great market demand. At the same time, the implementation of the present invention can also improve the level of power electronics technology and control system optimization, which has an important role in promoting the development of related fields.

[0131] The following is an embodiment of a high-power traction power supply bidirectional converter control device of the present invention, which can be used to execute an embodiment of a high-power traction power supply bidirectional converter control method of the present invention. For details not disclosed in the embodiment of a high-power traction power supply bidirectional converter control device of the present invention, please refer to the embodiment of a high-power traction power supply bidirectional converter control method of the present invention.

[0132] In one embodiment, a high-power traction power supply bidirectional converter control device is proposed, referring to Figure 4 As shown, the device includes: a prediction value module for collecting the AC three-phase grid voltage and the AC side three-phase current of each parallel converter, and converting it into The state equation of the current is obtained by the component, and the state equation of the current is discretized to obtain the predicted values ​​of the active current, reactive current and midpoint voltage;

[0133] The three-phase unbalanced current component acquisition module is used to define the three-phase unbalanced current of the parallel converter according to the collected three-phase current on the AC side of each parallel converter, and obtain the Active and reactive components of unequal current in the coordinate system;

[0134] A cost function module is used to construct a cost function according to the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current;

[0135] The optimization module is used to calculate the cost function values ​​corresponding to all switch states, and take the switch state that minimizes the cost function value as the optimal switch state. According to the optimal switch state, the on and off states of the semiconductor switch devices of each parallel converter are controlled within their respective control cycles, thereby realizing the current sharing control of the bidirectional converter.

[0136] Figure 4 The given value module in is used to obtain the active current given value and the reactive current given value respectively by using the DC side voltage regulator and the reactive power regulator.

[0137] It should be noted that the high-power traction power supply bidirectional converter control device provided in the above embodiment only uses the division of the above-mentioned functional modules as an example when executing the high-power traction power supply bidirectional converter control method. In actual applications, the above-mentioned functions can be assigned to different functional modules as needed, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. In addition, the high-power traction power supply bidirectional converter control device provided in the above embodiment and the high-power traction power supply bidirectional converter control method embodiment belong to the same concept. The implementation process thereof is detailed in the high-power traction power supply bidirectional converter control method embodiment, which will not be repeated here.

[0138] In one embodiment, a high-power traction power supply bidirectional converter control system is proposed, and further reference is made to Figure 4 As shown, the system includes: at least two of the above-mentioned high-power traction power supply bidirectional converter control devices, and one high-power traction power supply bidirectional converter control device is correspondingly connected to a bidirectional converter.

[0139] The number of control devices for a high-power traction power supply bidirectional converter is determined by the number of components in the converter.

[0140] In one embodiment, a computer-readable storage medium is proposed, in which a computer program is stored. When the computer program is executed by a processor, the high-power traction power supply bidirectional converter control method described in any of the above embodiments is implemented.

[0141] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, the aforementioned storage medium can be a non-volatile storage medium such as a disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0142] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0143] In addition, those skilled in the art will understand that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments also means being within the scope of protection of the present invention and forming different embodiments. For example, in the above embodiments, those skilled in the art can use them in combination according to the known technical solutions and the technical problems to be solved by this application.

[0144] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A high-power traction power supply bidirectional converter control method, characterized in that: The method is applicable to a three-level converter topology, and the method comprises: The three-phase grid voltage on the AC side and the three-phase current on the AC side of each parallel converter are collected and converted into The state equation of the component current is obtained; The predicted values ​​of active current, reactive current and midpoint voltage are obtained by discretizing the state equation of current; The three-phase unbalanced current of the parallel converter is defined according to the three-phase current of the AC side of each parallel converter, and the coordinate transformation is used to obtain Active and reactive components of unequal current in the coordinate system; The three-phase unbalanced current of the parallel converter is defined according to the collected three-phase current of the AC side of each parallel converter as: [ ] T ， Phase unequal current , Phase unequal current and Phase unequal current They are: ， In the formula, , , , , , is the three-phase current on the AC side of the parallel converter; After coordinate transformation, we get The active and reactive components of the unequal current in the coordinate system are: ， In the formula, is the active component of the unequal current, is the reactive component of the unequal current, is the coordinate transformation formula; A cost function is constructed according to the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current; In order to control the unbalanced current and avoid the design of the weight coefficient of the unbalanced current optimization item, the cost function is constructed according to the predicted values ​​of the active current, reactive current and midpoint voltage and the active component and reactive component of the unbalanced current: ， In the formula, To consider the active current command after the uneven current, is the reactive current instruction after considering the uneven current; is the active current instruction after considering the uneven current , reactive power instruction , obtained by using the active current given value, the reactive current given value and the active component and reactive component of the unbalanced current; the active current given value and the reactive current given value are obtained by using the DC side voltage regulator and the reactive power regulator respectively; is the weight coefficient of the midpoint potential under a single weight coefficient, is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage; Calculate the cost function values ​​corresponding to all switch states, and take the switch state that minimizes the cost function value as the optimal switch state; The on / off state of the semiconductor switch device of each parallel converter is controlled in each control cycle according to the optimal switch state, thereby realizing the current sharing control of the bidirectional converter.

2. The high-power traction power supply bidirectional converter control method according to claim 1 is characterized in that: The three-phase grid voltage on the AC side and the three-phase current on the AC side of each parallel converter are collected and converted into The state equations for component acquisition current include: The collected three-phase AC grid voltage and the three-phase AC current of each parallel converter are The coordinate transformation formula is converted to Quantity; , , In the formula, is the rotation angle of the grid voltage, , The grid voltage Quantity, , , is the three-phase grid voltage, , The grid current Quantity, , , is the three-phase current on the AC side of the parallel converter, Represents the number of the parallel-connected converter, ∈{1,2…}; Calculate the AC side voltage of each parallel converter corresponding to the switch state at the previous moment Component; AC side voltage of each parallel converter Serving size: ， In the formula, , is the voltage on the AC side of the parallel converter Quantity, Represents the number of the parallel-connected converter, ∈{1,2…}, is the DC side voltage of the parallel converter, , , are the switching states of the parallel converters respectively; The grid voltage and current Components and AC side voltage of parallel converters The state equation of the component current is: ， In the formula, is the grid-side inductance value, is the grid angular frequency, is the equivalent resistance value of the grid-side filter.

3. The high-power traction power supply bidirectional converter control method according to claim 2 is characterized in that: By discretizing the state equation of the current, the predicted values ​​of active current and reactive current are obtained as follows: ， In the formula, is the predicted value of active current, is the predicted value of reactive current, To control the cycle, , for The grid current at the moment Quantity, , for The AC side voltage of the parallel converter at the moment Quantity, , for The grid voltage at the moment Quantity; The predicted value of the midpoint voltage is: ， In the formula, is the predicted value of the midpoint voltage, , For parallel converters The midpoint current and midpoint voltage of the DC side at the moment, , are the upper and lower bus capacitances of the three-level converter, Represents the number of the parallel-connected converter, ∈{1,2…}.

4. The high-power traction power supply bidirectional converter control method according to claim 1, characterized in that: The active current instruction after considering the uneven current , reactive current command for: ， In the formula, is the active current given, is the reactive current given, is the active component of the unequal current, is the reactive component of the unequal current, Represents the number of the parallel-connected converter, ∈{1,2…}.

5. The high-power traction power supply bidirectional converter control method according to claim 1, characterized in that: In order to achieve separate control of the active and reactive components of the uneven current, the cost function constructed is: ， In the formula, is the active current given, is the reactive current given, is the weight coefficient of the midpoint voltage under multiple weight coefficients, is the weight coefficient of the active component of the unequal current, is the weight coefficient of the reactive component of the uneven current, which is adjusted by To achieve the control of the midpoint voltage, by adjusting To achieve the control of the active component of the uneven current, by adjusting Realize the control of reactive component of uneven current; is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage; , are the allowable variation ranges of active current and reactive current unequal flow conditions, is the active component of the unequal current, is the reactive component of the unequal current; The allowable variation range of the active current and reactive current unequal current situation , The setting is based on: For the application scenario where the grid-side power factor is 1, the reactive current is controlled near zero. > ; For the application scenario of reactive power compensation, > .

6. A high-power traction power supply bidirectional converter control device, characterized in that: The device comprises: The prediction value module is used to collect the three-phase grid voltage on the AC side and the three-phase current on the AC side of each parallel converter, and convert it into The state equation of the current is obtained by the component, and the state equation of the current is discretized to obtain the predicted values ​​of the active current, reactive current and midpoint voltage; The three-phase unbalanced current component acquisition module is used to define the three-phase unbalanced current of the parallel converter according to the collected three-phase current on the AC side of each parallel converter, and obtain the Active component and reactive component of the unbalanced current in the component coordinate system; the three-phase unbalanced current of the parallel converter is defined according to the collected three-phase current on the AC side of each parallel converter as: [ ] T ， Phase unequal current , Phase unequal current and Phase unequal current They are: ， In the formula, , , , , , is the three-phase current on the AC side of the parallel converter; After coordinate transformation, we get The active and reactive components of the unequal current in the coordinate system are: ， In the formula, is the active component of the unequal current, is the reactive component of the unequal current, is the coordinate transformation formula; A cost function module is used to construct a cost function according to the predicted values ​​of active current, reactive current and midpoint voltage and the active component and reactive component of the uneven current; In order to control the unbalanced current and avoid the design of the weight coefficient of the unbalanced current optimization item, the cost function is constructed according to the predicted values ​​of the active current, reactive current and midpoint voltage and the active component and reactive component of the unbalanced current: ， In the formula, To consider the active current command after the uneven current, is the reactive current instruction after considering the uneven current; is the active current instruction after considering the uneven current , reactive power instruction , obtained by using the active current given value, the reactive current given value and the active component and reactive component of the unbalanced current; the active current given value and the reactive current given value are obtained by using the DC side voltage regulator and the reactive power regulator respectively; is the weight coefficient of the midpoint potential under a single weight coefficient, is the predicted value of active current, is the predicted value of reactive current, is the predicted value of the midpoint voltage; The optimization module is used to calculate the cost function values ​​corresponding to all switch states, and take the switch state that minimizes the cost function value as the optimal switch state. According to the optimal switch state, the on and off states of the semiconductor switch devices of each parallel converter are controlled within their respective control cycles, thereby realizing the current sharing control of the bidirectional converter.

7. A high-power traction power supply bidirectional converter control system, characterized in that: include: At least two high-power traction power supply bidirectional converter control devices as described in claim 6, one high-power traction power supply bidirectional converter control device is connected to a corresponding bidirectional converter.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the high-power traction power supply bidirectional converter control method as claimed in any one of claims 1 to 5 are implemented.

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