A method and system for controlling a current transformer

Abstract

The present application belongs to the field of converter control, and particularly relates to a kind of converter control method and system.The present application carries out double-loop control by voltage outer loop and current inner loop, adds current feedforward value into current inner loop to generate corresponding control instruction;Current feedforward value is determined according to system influence factor;System influence factor includes the deviation degree of actual voltage of DC bus connected with converter compared with corresponding set value;In the case of meeting set limit condition, the positive and negative of current feedforward value is consistent with the positive and negative of the difference between actual voltage of DC bus and corresponding set value;That is, the current feedforward value that changes with the deviation degree of actual voltage of DC bus compared with corresponding set value is added into current inner loop, and the positive and negative of the current feedforward value is also consistent with the deviation direction of actual voltage compared with corresponding set value, so that the current inner loop control can respond more quickly to voltage fluctuation caused by DC bus voltage change through the current feedforward value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of converter control, and particularly relates to a converter control method and system. BACKGROUND

[0002] The AC power grid connected to the subway and the DC bus corresponding to the AC power grid are often connected through a bidirectional converter; when the subway starts, the AC power grid energy can be provided to accelerate the start of the subway; since a large amount of regenerative braking energy is generated when the subway brakes, the bidirectional converter feeds back the subway braking energy to the AC power grid; the bidirectional conversion characteristic of the bidirectional converter can realize the feedback characteristic of the energy feedback converter and also can take into account the function of stabilizing the DC bus voltage of the traction converter, which becomes a new trend of energy transfer of subway systems in the future.

[0003] However, when the subway brakes and brakes, due to the rapidity of the braking energy and the traction energy, the bidirectional converter will cause a large fluctuation of the voltage of the catenary between the AC power grid connected to the DC bus and the DC bus when the bidirectional converter is put into operation, thereby causing oscillation fluctuation of the DC bus voltage; therefore, the subway converter generally adopts a double-loop control scheme of a voltage outer loop and a current inner loop to suppress the fluctuation of the DC bus voltage, as shown in FIG. 1. Figure 1 When the voltage fluctuates, the voltage outer loop sends the output to the current inner loop as a reference value corresponding to the active part of the current, and adjusts the current command to suppress the voltage fluctuation; however, in the case of a large fluctuation energy and a rapid voltage fluctuation, the response speed of this control mode is slow, and it is difficult to quickly and effectively suppress the fluctuation of the DC bus voltage, and the overvoltage condition occurs still frequently. SUMMARY

[0004] The purpose of the present application is to provide a converter control method and system to solve the problem that the response speed of the control mode of the existing subway converter is slow, which makes it difficult to quickly and effectively suppress the fluctuation of the DC bus voltage.

[0005] In order to achieve the above-mentioned purpose, the present application provides a converter control method, which performs double-loop control through a voltage outer loop and a current inner loop, and adds a current feedforward value to the current inner loop to generate a corresponding control command.

[0006] The current feedforward value is determined according to a system influence factor; the system influence factor includes the deviation degree of the actual voltage of the DC bus connected to the converter from the corresponding set value; in the case of satisfying the set limit condition, the positive and negative of the current feedforward value is consistent with the positive and negative of the difference between the actual voltage of the DC bus and the corresponding set value.

[0007] Further, the greater the deviation, the greater the absolute value of the current feedforward value is, when the set limit condition is met.

[0008] The current feedforward value is added to the active current part of the current inner loop, and the sum of the current feedforward value and the reference value corresponding to the current active part is subtracted by the actual value of the current active part to generate the corresponding control instruction.

[0009] Further, the system influence factor further comprises a current operating state of the converter; the operating state comprises a feedback state, an intermediate state and a traction state; and the deviation of the actual voltage of the DC bus connected to the converter from the corresponding set value comprises a deviation of the actual voltage of the DC bus from a feedback set value when the current operating state is the feedback state and a deviation of the actual voltage of the DC bus from a traction set value when the current operating state is the traction state.

[0010] Further, the set limit condition comprises that the current operating state of the converter is the feedback state or the traction state.

[0011] Further, the judgment of the current operating state of the converter comprises:

[0012] If the actual voltage of the DC bus is greater than or equal to the feedback set value, the current operating state of the converter is judged to be the feedback state; if the actual voltage of the DC bus is less than or equal to the traction set value, the current operating state of the converter is judged to be the traction state; and the feedback set value is greater than the traction set value.

[0013] If the actual voltage of the DC bus is less than the feedback set value and greater than the traction set value, the current operating state of the converter is judged to be the intermediate state.

[0014] Further, the system influence factor further comprises a DC bus rated voltage; and the method for determining the current feedforward value according to the system influence factor comprises:

[0015] judging the current operating state of the converter;

[0016] If the current operating state of the converter is the feedback state, a current reference feedforward value is calculated according to the difference between the actual voltage of the DC bus and the feedback set value and the rated voltage of the DC bus; the current reference feedforward value is multiplied by the corresponding weight to obtain a feedforward calculation value; the greater the deviation of the actual voltage of the DC bus from the feedback set value, the greater the corresponding weight; and the corresponding weight is greater than or equal to 1.

[0017] If the current operation state of the converter is the traction state, a current reference feedforward value is calculated according to a difference between the actual voltage of the DC bus and a traction set value and a rated voltage of the DC bus; the current reference feedforward value is multiplied by a corresponding weight feedforward calculation value to obtain a feedforward calculation value; the greater the deviation of the actual voltage of the DC bus from the traction set value, the greater the corresponding weight.

[0018] After the feedforward calculation value is obtained, a current feedback value is obtained according to the feedforward calculation value; if the current operation state of the converter is the intermediate state, the set feedforward value is taken as the current feedback value.

[0019] Further, the set limit condition further comprises that the feedforward calculation value is greater than a set lower threshold value and less than a set upper threshold value.

[0020] Further, the manner of obtaining the current feedback value according to the feedforward calculation value comprises:

[0021] If the feedforward calculation value is less than the set upper threshold value and greater than the set lower threshold value, the feedforward calculation value is taken as the current feedback value; if the feedforward calculation value is greater than or equal to the set upper threshold value, the current feedback value is limited to be below the set upper threshold value; if the feedforward calculation value is less than or equal to the set lower threshold value, the current feedback value is limited to be above the set lower threshold value.

[0022] Further, the feedback set value and the traction set value are determined according to a rectified voltage of a power supply system in which the DC bus is located.

[0023] The above technical solution of the present application is based on the existing double-loop control scheme of the converter through the voltage outer loop and the current inner loop, and the control of the current inner loop is improved, and the beneficial effects thereof include:

[0024] The current feedback value that changes with the deviation of the actual voltage of the DC bus from the corresponding set value is added to the current inner loop, and the positive and negative of the current feedback value are also consistent with the deviation direction (i.e., the positive and negative of the difference between the actual voltage of the DC bus and the corresponding set value) of the actual voltage from the corresponding set value, so that the current inner loop control can respond more quickly to voltage fluctuations caused by changes in the DC bus voltage by adding the current feedback value that can reflect the change trend of the DC bus voltage, and thus the DC bus voltage fluctuations can be quickly and effectively suppressed in a timely manner.

[0025] The present application also provides a converter control system, comprising a processor, wherein executable program instructions are stored in the processor, and the program instructions are used to be executed to realize the converter control method according to the above.

[0026] The converter control system has the same beneficial effects as the converter control method. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A schematic diagram of a principle of a double-loop control scheme of a voltage outer loop and a current inner loop commonly used in the background art of the present application;

[0028] Figure 2 A flowchart of the converter control method in the embodiment of the present application;

[0029] Figure 3 A schematic diagram of a principle of a double-loop control scheme of a voltage outer loop and a current inner loop after adding a current feedforward value in the embodiment of the present application;

[0030] Figure 4 A flowchart of a judging mode of a current operating state of the converter in the embodiment of the present application;

[0031] Figure 5 A flowchart of determining a feedforward calculation value in the case that the current operating state of the converter is a feedback state in the embodiment of the present application;

[0032] Figure 6 A flowchart of determining a feedforward calculation value in the case that the current operating state of the converter is a traction state in the embodiment of the present application. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed descriptions will be given to the present application in combination with the accompanying drawings and embodiments.

[0034] Embodiment of the converter control method

[0035] The embodiment provides a converter control method, which performs double-loop control through a voltage outer loop and a current inner loop; referring to Figure 2 The converter control method also adds a current feedforward value to the current inner loop to generate a corresponding control instruction (such as a current instruction);

[0036] The current feedforward value is determined according to a system influence factor; the system influence factor includes a deviation degree of an actual voltage of a DC bus connected to the converter from a corresponding set value; in the case of satisfying a set limit condition, the positive and negative of the current feedforward value are consistent with the positive and negative of a difference between the actual voltage of the DC bus and the corresponding set value. It should be noted that all the “DC bus” mentioned in the embodiment refers to the DC bus connected to the converter.

[0037] Therefore, the current feedforward value varying with the deviation degree of the actual voltage of the DC bus from the corresponding set value is added to the current inner loop, and the positive and negative of the current feedforward value is consistent with the deviation direction of the actual voltage of the DC bus from the corresponding set value (i.e. the positive and negative of the difference between the actual voltage of the DC bus and the corresponding set value), so that the current inner loop control can respond more quickly to the voltage fluctuation caused by the change of the DC bus voltage by adding the current feedforward value reflecting the change trend of the DC bus voltage, and thus the DC bus voltage fluctuation can be quickly and effectively suppressed in a timely manner.

[0038] In addition, in the embodiment, when the set limit condition is met, the greater the deviation degree, the greater the absolute value of the current feedforward value; therefore, the degree of change of the DC bus voltage can be further reflected by the current feedforward value which increases with the increase of the deviation degree, so that the control amount generated by the current inner loop control can be increased in suppression strength according to the greater fluctuation of the DC bus voltage, and the DC bus voltage fluctuation caused by the change of the DC bus can be suppressed more quickly, and thus the suppression efficiency of the DC bus voltage fluctuation can be improved.

[0039] In the embodiment, the deviation degree of the actual voltage of the DC bus from the feedback set value is obtained according to the absolute value of the difference between the actual voltage of the DC bus and the feedback set value, and the deviation degree of the actual voltage of the DC bus from the traction set value is obtained according to the absolute value of the difference between the actual voltage of the DC bus and the traction set value. In other embodiments, the deviation degree of the actual voltage of the DC bus from the feedback set value and the traction set value can also be in the form of proportion, logarithm, etc., as long as it can reflect the deviation degree of the actual voltage of the DC bus from the corresponding set value and ensure that the positive and negative of the current feedforward value is consistent with the positive and negative of the difference between the actual voltage of the DC bus and the corresponding set value, without affecting the concept of the present application.

[0040] The way of adding the current feedforward value to the current inner loop is referred to Figure 3 , specifically: the current feedforward value is added to the active current part of the current inner loop, and the sum of the reference value corresponding to the current active part and the current feedforward value is subtracted by the actual value of the current active part to generate the corresponding control instruction. Figure 3 In comparison with Figure 1 , the Im_value' newly added to the current inner loop is the current feedforward value.

[0041] In order to make the determined current feedforward value more suitable for the actual working condition, the system influence factor further comprises a current operating state of the converter; wherein, the operating state comprises a feedback state, an intermediate state and a traction state; in the case that the current operating state is the feedback state, the corresponding set value in the deviation degree of the actual voltage of the DC bus from the corresponding set value is the feedback set value, and in the case that the current operating state is the traction state, the corresponding set value in the deviation degree of the actual voltage of the DC bus from the corresponding set value is the traction set value; that is, the deviation degree of the actual voltage of the DC bus from the corresponding set value comprises the deviation degree of the actual voltage of the DC bus from the feedback set value in the case that the current operating state is the feedback state and the deviation degree of the actual voltage of the DC bus from the traction set value in the case that the current operating state is the traction state.

[0042] The set limit condition mentioned above comprises: the current operating state of the converter is the feedback state or the traction state. Since the DC bus will only produce a large energy change when the converter is in the feedback state or the traction state, resulting in a large voltage fluctuation on the DC bus side that is difficult to suppress in time, only when the current operating state of the converter is the feedback state or the traction state, the current feedforward value is increased accordingly with the increase of the deviation degree, so as to avoid the occurrence of over-suppression that affects the normal operation of the DC bus when the fluctuation on the DC bus side is small.

[0043] Specifically, referring to Figure 4 , the judgment method of the current operating state of the converter comprises:

[0044] If the actual voltage of the current DC bus is greater than or equal to the feedback set value, it is judged that the current operating state of the current converter is the feedback state; if the actual voltage of the current DC bus is less than or equal to the traction set value, it is judged that the current operating state of the current converter is the traction state; wherein, the feedback set value is greater than the traction set value; the feedback set value and the traction set value are determined according to the rectified voltage of the power supply system where the DC bus is located. Since the entire metro DC bus voltage is rectified by the rectifier in the power supply system where the DC bus is located, the corresponding rectified voltage of the rectifier is equivalent to the reference voltage of the entire metro bus network, and the traction voltage threshold and the feedback voltage threshold will fluctuate with the voltage rectified by the rectifier in the power supply system where the DC bus is located; this part of the content belongs to the prior art in the field of metro design, and will not be described here.

[0045] If the actual voltage of the current DC bus is less than the feedback set value and greater than the traction set value, it is judged that the current converter is in the intermediate state.

[0046] The feedback setting value in the above judgment mode is the corresponding setting value in the deviation degree of the actual voltage of the DC bus from the corresponding setting value when the current operating state is the feedback state; the traction setting value is the corresponding setting value in the deviation degree of the actual voltage of the DC bus from the corresponding setting value when the current operating state is the traction state; in combination with the judgment mode, since the system influence factor also includes the DC bus rated voltage, the mode for determining the current feedforward value according to the system influence factor includes:

[0047] 1) judging the current operating state of the converter;

[0048] 2) if the current operating state of the converter is the feedback state, calculating the current reference feedforward value according to the difference between the actual voltage of the DC bus and the feedback setting value and the rated voltage of the DC bus; multiplying the current reference feedforward value by the corresponding weight to obtain the feedforward calculation value; the greater the deviation degree of the actual voltage of the DC bus from the feedback setting value, the greater the corresponding weight;

[0049] if the current operating state of the converter is the traction state, calculating the current reference feedforward value according to the difference between the actual voltage of the DC bus and the traction setting value and the rated voltage of the DC bus; multiplying the current reference feedforward value by the corresponding weight to obtain the feedforward calculation value; the greater the deviation degree of the actual voltage of the DC bus from the traction setting value, the greater the corresponding weight; and the corresponding weight is greater than or equal to 1;

[0050] 3) after obtaining the feedforward calculation value, obtaining the current feedforward value according to the obtained feedforward calculation value; if the current operating state of the converter is the intermediate state, taking the set feedforward value as the current feedforward value. In this embodiment, in order to avoid over-inhibition of the current feedforward value to a small degree of voltage fluctuation, the set feedforward value is 0 or a value less than a certain value.

[0051] Therefore, different calculation modes (different calculation modes when the current operating state of the converter is the feedback state, the traction state and the intermediate state) and different corresponding setting values (i.e. the feedback setting value and the traction setting value) are selected for different operating states of the converter, the corresponding current feedforward value is obtained, the obtained current feedforward value is more matched with the actual working condition of the converter; and the current reference feedforward value calculated by the difference between the actual voltage of the DC bus and the traction setting value which can reflect the deviation degree is multiplied by the weight which can also reflect the deviation degree to obtain the current feedforward value; therefore, when the DC bus voltage changes greatly, the increasing degree of the corresponding current feedforward value can be further improved, and the generated high degree of voltage fluctuation of the DC bus can be more quickly suppressed to a low level.

[0052] To avoid the current feedforward value increasing unlimitedly in the case that the current operation state of the converter is the feedback state or the traction state, the limit condition further includes that the feedforward calculation value is greater than a set lower threshold value and less than a set upper threshold value. Correspondingly, the way of obtaining the current feedforward value according to the feedforward calculation value includes:

[0053] If the feedforward calculation value is less than the set upper threshold value and greater than the set lower threshold value, the feedforward calculation value is taken as the current feedforward value; if the feedforward calculation value is greater than or equal to the set upper threshold value, the current feedforward value is limited below the set upper threshold value; if the feedforward calculation value is less than or equal to the set lower threshold value, the current feedforward value is limited above the set lower threshold value. In this way, the current feedforward value can be limited within a certain range, avoiding the case that the current feedforward value is inhibited too much due to the current feedforward value increasing unlimitedly. Specifically, in the embodiment, the set upper threshold value is 1 per unit value and the set lower threshold value is -1 per unit value; the way of limiting the current feedforward value below the set upper threshold value is taking the set upper threshold value as the current feedforward value; the way of limiting the current feedforward value above the set lower threshold value is taking the set lower threshold value as the current feedforward value.

[0054] Specifically, the process of the converter control is fully demonstrated by the following example:

[0055] a) First, the actual voltage Udc of the DC bus to which the converter is connected is detected (the actual voltage Udc of the DC bus here can also be directly referred to as the bus voltage);

[0056] b) Then, the current operation state of the converter is judged according to the actual voltage Udc of the current DC bus:

[0057] If Udc is greater than or equal to the feedback voltage set value Vfeedback Set, it is judged that the current converter is in the feedback state;

[0058] If Udc is less than or equal to the traction voltage set value Vtraction Set, it is judged that the current converter is in the traction state;

[0059] If Udc is less than the feedback voltage set value Vfeedback Set and greater than the traction voltage set value Vtraction Set, it is judged that the current converter is in the intermediate state;

[0060] c) The current feedforward value is calculated according to the current operation state of the converter, the deviation degree of the actual voltage Udc of the DC bus compared with the corresponding set value (the feedback voltage set value Vfeedback Set and the traction voltage set value Vtraction Set), and the DC bus rated voltage Udc rate:

[0061] Referring to Figure 5If the current operation state of the converter is the feedback state, the current reference feedforward value Im_value0 = (Udc-Vfeedback_set)*(1 / Udc_rate) is calculated first; when the difference between the bus voltage and the feedback voltage set value is less than or equal to 25V, the feedforward calculation value Im_value is equal to the reference feedforward current value;

[0062] When the difference between the bus voltage and the feedback voltage set value is greater than 25V and not greater than 50V, the feedforward calculation value Im_value is equal to 1.3 times the reference feedforward current value Im_value0, i.e. Im_value = Im_value0*1.3;

[0063] When the difference between the bus voltage and the feedback voltage set value is greater than 50V and not greater than 75V, the feedforward calculation value is equal to 1.5 times the reference feedforward current value, i.e. Im_value = Im_value0*1.5;

[0064] When the difference between the bus voltage and the feedback voltage set value is greater than 75V and not greater than 100V, the feedforward calculation value is equal to 1.7 times the reference feedforward current value, i.e. Im_value = Im_value0*1.7;

[0065] When the difference between the bus voltage and the feedback voltage set value is greater than 100V and not greater than 125V, the feedforward calculation value is equal to 2.0 times the reference feedforward current value, i.e. Im_value = Im_value0*2.0;

[0066] When the difference between the bus voltage and the feedback voltage set value is greater than 125V and not greater than 150V, the feedforward calculation value is equal to 2.5 times the reference feedforward current value, i.e. Im_value = Im_value0*2.5;

[0067] When the difference between the bus voltage and the feedback voltage set value is greater than 150V, the feedforward calculation value is equal to 3.0 times the reference feedforward current value, i.e. Im_value = Im_value0*3.0;

[0068] When the feedforward calculation value Im_value is less than 1 per unit, the feedforward calculation value Im_value is taken as the current feedforward value Im_value'; when the feedforward calculation value Im_value is greater than or equal to 1 per unit, the current feedforward value Im_value' is limited to be below 1 per unit.

[0069] Referring to Figure 6If the current operation state of the converter is the traction state, the current reference feedforward value Im_value0 = (Udc-Vtraction_set)*(1 / Udc_rate) is calculated first; when the difference between the bus voltage and the feedback voltage set value is greater than or equal to -25V, the feedforward calculation value Im_value is equal to the reference feedforward current value;

[0070] When the difference between the bus voltage and the traction voltage set value is greater than -50V and not greater than -25V, the feedforward calculation value Im_value is equal to 1.3 times the reference feedforward current value Im_value0, i.e. Im_value = Im_value0*1.3;

[0071] When the difference between the bus voltage and the traction voltage set value is greater than -75V and not greater than -50V, the feedforward calculation value is equal to 1.5 times the reference feedforward current value, i.e. Im_value = Im_value0*1.5;

[0072] When the difference between the bus voltage and the traction voltage set value is greater than -100V and not greater than -75V, the feedforward calculation value is equal to 1.7 times the reference feedforward current value, i.e. Im_value = Im_value0*1.7;

[0073] When the difference between the bus voltage and the traction voltage set value is greater than -125V and not greater than -100V, the feedforward calculation value is equal to 2.0 times the reference feedforward current value, i.e. Im_value = Im_value0*2.0;

[0074] When the difference between the bus voltage and the traction voltage set value is greater than -150V and not greater than -125V, the feedforward calculation value is equal to 2.5 times the reference feedforward current value, i.e. Im_value = Im_value0*2.5;

[0075] When the difference between the bus voltage and the traction voltage set value is less than -150V, the feedforward calculation value is equal to 3.0 times the reference feedforward current value, i.e. Im_value = Im_value0*3.0;

[0076] When the feedforward calculation value Im_value is greater than -1 per unit, the feedforward calculation value Im_value is taken as the current feedforward value Im_value'; when the feedforward calculation value Im_value is less than or equal to -1 per unit, the current feedforward value Im_value' is limited to above -1 per unit.

[0077] If the current operation state of the converter is the intermediate state, the current feedforward value Im_value' is directly assigned as 0.

[0078] d) adding the current feedforward value Im_value' to the current loop of the converter control to generate corresponding current control instructions to suppress DC bus voltage fluctuation.

[0079] Converter control system embodiment

[0080] The embodiment provides a technical scheme of a converter control system, comprising a processor, and the processor stores executable program instructions, and the program instructions are used to be executed to implement the converter control method in the above-mentioned converter control method embodiment.

[0081] Since the specific working process and working principle of the converter control system in the embodiment have been described in detail in the above-mentioned converter control method embodiment, they will not be repeated here.

[0082] The application has the following characteristics:

[0083] ①The current feedforward value changing with the deviation degree of the actual DC bus voltage from the corresponding set value is added to the current inner loop, and the positive and negative of the current feedforward value is consistent with the deviation direction of the actual DC bus voltage from the corresponding set value (that is, the positive and negative of the difference between the actual DC bus voltage and the corresponding set value), so that on the basis of the existing double-loop control mode of the voltage outer loop and the current inner loop, the current inner loop control can respond more quickly to the voltage fluctuation caused by the change of the DC bus voltage by adding the current feedforward value reflecting the change trend of the DC bus voltage, and thus the DC bus voltage fluctuation can be quickly and effectively suppressed in a timely manner.

[0084] ②In the case of meeting the set limit condition, the greater the deviation degree, the greater the absolute value of the current feedforward value; thus, the degree of change of the DC bus voltage can be further reflected by the current feedforward value corresponding to the increase of the deviation degree, so that the control amount generated by the current inner loop control can be increased in suppression strength according to the greater fluctuation of the DC bus voltage that may occur, and the DC bus voltage fluctuation caused by the change of the DC bus can be suppressed more quickly, so that the suppression efficiency of the DC bus voltage fluctuation can be improved.

[0085] ③In order to make the determined current feedforward value more suitable for the actual working condition, the system influence factor further includes the current running state of the converter, and a set limit condition corresponding to the current running state of the converter being in the feedback state or the traction state is set; thus, the actual situation that the DC bus generates a larger energy change when the converter is in the feedback state or the traction state, resulting in a larger voltage fluctuation on the DC bus side that is difficult to suppress in time, can be considered, and only when the current running state of the converter is in the feedback state or the traction state, the current feedforward value is increased corresponding to the increase of the deviation degree, so as to avoid the over-suppression situation that the addition of the current feedforward value affects the normal operation of the DC bus when the fluctuation on the DC bus side is small.

[0086] ④On the basis of the current reference feedforward value calculated by the difference between the actual voltage of the DC bus capable of reflecting the deviation degree and the traction set value, the current feedforward value is multiplied by the weight also capable of reflecting the deviation degree; thus, when the DC bus voltage changes greatly, the increase degree of the corresponding current feedforward value can be further improved, and the generated higher degree of voltage fluctuation of the DC bus can be suppressed to a lower level more quickly.

[0087] ⑤A set limit condition that the feedforward calculation value is greater than the set lower threshold value and less than the set upper threshold value is further set, so that the current feedforward value is not increased unlimitedly when the current running state of the converter is in the feedback state or the traction state.

[0088] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes of the principles of the present application, and do not constitute a limitation on the present application.

Claims

1. A method for controlling a converter, which is controlled by a double-loop control of a voltage outer loop and a current inner loop, characterized in that, The current feedforward value is added to the current inner loop to generate a corresponding control instruction; In the case of meeting the set limit condition, the positive and negative of the current feedforward value is consistent with the positive and negative of the difference between the actual voltage of the DC bus and the corresponding set value; The determination method of the current feedforward value comprises: judging the current operating state of the converter; If the current operating state of the converter is the feedback state, the current reference feedforward value is calculated according to the difference between the actual voltage of the DC bus and the feedback set value and the rated voltage of the DC bus; the feedforward calculation value is obtained by multiplying the current reference feedforward value by the corresponding weight; the greater the deviation of the actual voltage of the DC bus from the feedback set value, the greater the corresponding weight; and the corresponding weight is greater than or equal to 1; If the current operating state of the converter is the traction state, the current reference feedforward value is calculated according to the difference between the actual voltage of the DC bus and the traction set value and the rated voltage of the DC bus; the feedforward calculation value is obtained by multiplying the current reference feedforward value by the corresponding weight; the greater the deviation of the actual voltage of the DC bus from the traction set value, the greater the corresponding weight; After obtaining the feedforward calculation value, the current feedforward value is obtained according to the feedforward calculation value; only when the current operating state of the converter is the feedback state or the traction state, the current feedforward value is increased accordingly with the increase of the deviation, so as to avoid the over-inhibition caused by the addition of the current feedforward value.

2. The converter control method according to claim 1, characterized by, The method for adding the current feedforward value to the current inner loop is to add the current feedforward value to the active current part of the current inner loop, and the sum of the corresponding reference value of the current active part and the current feedforward value is subtracted from the actual value of the current active part to generate a corresponding control instruction.

3. The method of claim 1, wherein, The judgment method of the current operating state of the converter comprises: If the current actual voltage of the DC bus is greater than or equal to the feedback set value, it is judged that the current operating state of the converter is the feedback state; if the current actual voltage of the DC bus is less than or equal to the traction set value, it is judged that the current operating state of the converter is the traction state; the feedback set value is greater than the traction set value; If the current actual voltage of the DC bus is less than the feedback set value and greater than the traction set value, it is judged that the current converter is in an intermediate state.

4. The method of claim 3, wherein, The method for determining the current feedforward value according to the system influence factor further comprises: if the current operating state of the converter is the intermediate state, the set feedforward value is taken as the current feedforward value.

5. The method of claim 1, wherein, The set limit condition comprises: the feedforward calculation value is greater than the set lower threshold and less than the set upper threshold.

6. The method of claim 5, wherein, The method for obtaining the current feedforward value according to the feedforward calculation value comprises: If the feedforward calculation value is less than the set upper threshold and greater than the set lower threshold, the feedforward calculation value is taken as the current feedforward value; if the feedforward calculation value is greater than or equal to the set upper threshold, the current feedforward value is limited below the set upper threshold; if the feedforward calculation value is less than or equal to the set lower threshold, the current feedforward value is limited above the set lower threshold.

7. The method of claim 1-6, wherein, The feedback set value and the traction set value are determined according to the rectified voltage of the power supply system in which the DC bus is located.

8. A converter control system characterized by, A processor having stored therein executable program instructions for execution to implement the converter control method according to any one of claims 1-7.

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