A Phase-Controlled Rectifier Control Method for an Auxiliary Converter

Abstract

The present invention relates to a rectification control method for an auxiliary converter of an electric locomotive, specifically a phase-controlled rectification control method for an auxiliary converter. To take the auxiliary converter as an overall control unit, the phase-controlled rectification is implemented by means of a fully digital control method of DSP+FPGA. The control program of the thyristor can be placed in the counting interrupt of the inverter, and the carrier wave of the thyristor is set to be the same as that of the inverter. The control frequency of the thyristor controller is set to 100 Hz. Since the variable that can be controlled is the firing angle of the thyristor, the target to be controlled stably is the output voltage on the DC side. By using a software phase-locked loop to obtain the current phase of the input voltage, it is ensured that the thyristor can conduct at the conduction angle. According to the characteristics of the thyristor itself, in the present invention, the DSP is used for operation to obtain the conduction angle of the thyristor, and then the FPGA emits a pulse wave with a width of 4 ms and a frequency of 23.5 kHz to ensure that the thyristor can be turned on at each conduction angle. It can be applied to engineering practice.

Description

Technical Field

[0001] The present invention relates to a rectification control method for an auxiliary converter of an electric locomotive, specifically a phase-controlled rectification control method for an auxiliary converter. Background Art

[0002] In recent years, with the continuous development of railway technology, electric locomotives have become the main models of railway transportation, and the modularization and high power of auxiliary converters of electric locomotives have become the development trend. The main circuit topology diagram of a high-power auxiliary converter is as Figure 1 shown. The figure includes four major modules: a thyristor rectification module D11, a DC bus filtering module L11, an inversion module POWER1, and an output filtering module TM1. Among them, the inversion module POWER1 and the thyristor rectification module D11 are controlled separately, and the high-power auxiliary converter cannot be controlled as a whole. Therefore, the present invention provides a phase-controlled rectification control method for an auxiliary converter of an electric locomotive. Summary of the Invention

[0003] The purpose of the present invention is to provide a phase-controlled rectification control method for an auxiliary converter that controls the auxiliary inverter and thyristors as a unified whole.

[0004] The present invention is implemented by adopting the following technical solutions: A phase-controlled rectification control method for an auxiliary converter includes the following steps:

[0005] Calculate the current phase of the grid-side input voltage of the thyristor rectification module;

[0006] After the DC-side voltage of the thyristor rectification module is sampled, it is compared with a reference value to generate an error value, and after passing through a PI controller, the trigger angle for controlling the thyristor is output.

[0007] Calculate the interval angle a = 180 / K1 / K2, where K1 is the interrupt frequency and K2 is the thyristor control frequency;

[0008] Compare the trigger angle with the current phase of the input voltage. If the absolute value of the difference is less than 0° or greater than 2a, no control is performed;

[0009] If the absolute value of the difference is less than a, immediately send out the trigger pulse wave of the thyristor;

[0010] If the absolute value of the difference is greater than or equal to a and less than or equal to 2a, assign a value to the register shadow. In the next interrupt cycle, update the Shadow register to the Active register and compare it with the carrier amplitude. When it is equal to the carrier amplitude, immediately send out the trigger pulse wave of the thyristor.

[0011] In the above-mentioned phase-controlled rectification control method for an auxiliary converter, the switching frequency of the inverter module is greater than the thyristor control frequency. The control program of the thyristor is placed in the counting interrupt of the inverter module, and the carrier wave of the thyristor is set to be the same as that of the inverter module. The auxiliary inverter and the thyristor are controlled as a unified whole.

[0012] In the above-mentioned phase-controlled rectification control method for an auxiliary converter, the thyristor control method is carried out in the DSP, and then the trigger pulse wave is sent out by the FPGA.

[0013] In the above-mentioned phase-controlled rectification control method for an auxiliary converter, the phase-locked loop in the DSP obtains the current phase of the grid-side input voltage of the thyristor rectification module.

[0014] In the above-mentioned phase-controlled rectification control method for an auxiliary converter, after the FPGA sends out the trigger pulse wave, the thyristor is driven through a pulse transformer.

[0015] According to the control requirements of the auxiliary converter of an electric locomotive and in combination with the overall control of the auxiliary converter, the present invention takes the auxiliary inverter and the thyristor rectification as a unified whole, and adopts the software phase-locked loop control technology to omit the hardware zero-point detection circuit in engineering, and can be widely applied to engineering practice. Description of the Drawings

[0016] Figure 1 It is the main circuit topology diagram of a high-power auxiliary converter.

[0017] Figure 2 It is the thyristor control block diagram.

[0018] Figure 3 It is the register assignment diagram.

[0019] Figure 4 It is the phase diagram of the grid-side voltage.

[0020] Figure 5 It is the pulse trigger program logic diagram of the method of the present invention. Detailed Embodiment

[0021] The present invention will be further described in detail below in conjunction with the drawings of the specification.

[0022] Figure 1 The main circuit topology diagram of a high-power auxiliary converter is given. The figure contains 4 major modules, namely the thyristor rectification module D11, the DC bus filtering module L11, the inverter module POWER1, and the output filtering module TM1.

[0023] The input rated voltage of the auxiliary converter is 1000AC. After phase-controlled rectification by the thyristor rectification module D11, the intermediate bus voltage of 750V is obtained and then passed through the three-phase bridge inverter module POWER1, and then the AC380 voltage is obtained through the output filter module TM1. The control of the thyristor is achieved by controlling the trigger angle of the thyristor to stabilize the output voltage. To use the auxiliary converter as an overall ACU control unit, the phase-controlled rectification of the thyristor rectification module D11 is realized by the fully digital control method of DSP+FPGA. Since the switching frequency of the inverter is 750Hz, the control program of the thyristor can be placed in the counting interrupt of the inverter, and the carrier of the thyristor is set to be the same as that of the inverter. According to the thyristor trigger characteristics and the rated input network voltage frequency of 50Hz, the control frequency of the controller is set to 100Hz. Since the variable that can be controlled is the trigger angle of the thyristor and the target to be stabilized by control is the output voltage on the DC side, the trigger angle can be adjusted through a PI closed-loop controller, and then the output voltage on the DC side can be controlled. Attached Figure 2 as shown. After sampling the DC side voltage, it is compared with the reference value to generate an error value, which is amplified after passing through the PI controller H(s), and the output of the PI link is used to control the trigger angle of the thyristor to control the output reference value voltage of the controlled object. By using a software phase-locked loop to obtain the current phase of the input voltage, it is ensured that the thyristor can conduct at the conduction angle. According to the characteristics of the thyristor itself, in the present invention, the DSP is used for calculation to obtain the conduction angle of the thyristor, and then the FPGA sends out a pulse wave with a width of 4ms and a frequency of 23.5kHz to ensure that the thyristor can be turned on at each conduction angle.

[0024] Two conditions need to be met when triggering the thyristor:

[0025] 1. The forward voltage drop of the thyristor is greater than zero.

[0026] 2. The thyristor receives a trigger signal.

[0027] Since the switching frequency of the inverter module is 750Hz, the control program of the thyristor can be placed in the counting interrupt of the inverter module, and the carrier of the thyristor is set to be the same as that of the inverter module. The triggering principle is as attached Figure 3 as shown. For the upper tube of the thyristor, when it is not triggered within one cycle, the value of the CMPR register is greater than the peak value of the carrier. When at the trigger angle (78° in the figure), CMPR is assigned a value for comparison, generating a pulse sequence of 23.5kHz.

[0028] Due to the previous principle analysis of the thyristor and the design of the generation of the control pulse, the theoretical control strategy has been obtained, and the control strategy needs to be realized through a program. It mainly includes several aspects:

[0029] 1. Calculation of the PI control program. Since the actual control frequency of the thyristor is 100 Hz, that is, it is only necessary to calculate the triggering of the upper tube in the positive half-wave and calculate the triggering of the lower tube in the negative half-wave. And the calculation interruption frequency is 1500 Hz. Excessive calculations cannot improve the control performance but increase the useless calculation burden. Therefore, only two calculations are required per cycle.

[0030] 2. Assignment of CMPR. As shown in the appendix Figure 3 It can be seen that in the thyristor pulse triggering logic, the comparison is only carried out within half of the carrier period. At other times, the value of the CMPR register is greater than the carrier PRD. Therefore, it is necessary to determine when to update the value of the CMPR register.

[0031] Based on the above control strategy, the control logic is designed. Since the thyristor control frequency is 100 Hz and the interruption frequency is 1500 Hz, each time the interruption is entered, the phase information read should differ by 180 / 15 = 12° under the ideal condition of 50 Hz network voltage. In the actual process, there will be certain fluctuations. Therefore, it needs to be considered in the design of the control program.

[0032] 1. PI calculation time.

[0033] Due to the previous design, the control frequency is 100 Hz. In theory, it is only necessary to calculate at the zero-crossing point, but it is difficult to detect the actual zero-crossing point. The phase of the grid-side input voltage obtained through the phase-locked loop is as shown in the appendix Figure 4 It is shown that it is from -90° to 270°. And the control requires two calculations to be entered within one cycle. Then, it can be calculated once when the phase is less than zero, and then the phase information is delayed. When the processed phase is less than zero, it is calculated again, which can also meet the PI calculation requirements. Moreover, there is a 90° margin in the interval where the phase information is less than zero, avoiding the situation where the fluctuation of the phase information may cause the calculation point to be skipped when making the zero-crossing judgment with a 12° margin.

[0034] 2. Update of the register.

[0035] After PI control, the output information is understood as the triggering angle, and its range is from 0° to 180°. The interruption is triggered when the count value is equal to zero or PRD. At the same time, the assignment of CMPR is first saved in the Shadow register. When the count value is equal to zero or PRD, the Shadow register is updated to the Active register. Therefore, the delay caused by the counter update delay needs to be considered when assigning values. The pulse triggering program logic in one interruption is as shown in the appendix Figure 5 It is shown.

[0036] Through the above strategy, the problems of missing calculation points and pulse loss can be effectively avoided.

Claims

1. A phase-controlled rectification control method for an auxiliary converter, characterized in that: It includes the following steps: Calculate the current phase of the grid-side input voltage of the thyristor rectifier module; After the DC-side voltage of the thyristor rectifier module is sampled, it is compared with the reference value to generate an error value, and the trigger angle of the thyristor is output after passing through a PI controller; Calculate the interval angle a = 180 / K1 / K2, where K1 is the interrupt frequency and K2 is the thyristor control frequency; Compare the trigger angle with the current phase of the input voltage. If the difference is less than 0° or greater than 2a, no control is performed; If the difference is less than a, immediately issue the trigger pulse wave of the thyristor; If the difference is greater than or equal to a and less than or equal to 2a, assign a value to the register Shadow. In the next interrupt cycle, the Shadow register is updated to the Active register and compared with the carrier amplitude. When it is equal to the carrier amplitude, immediately issue the trigger pulse wave of the thyristor.

2. The phase-controlled rectification control method of an auxiliary converter according to claim 1, wherein: The switching frequency of the inverter module is greater than the thyristor control frequency. Place the control program of the thyristor in the counting interrupt of the inverter module. Set the carrier of the thyristor to be the same as that of the inverter module, and control the auxiliary inverter and the thyristor as a unified whole.

3. A phase-controlled rectification control method for an auxiliary converter according to claim 2, characterized in that: The thyristor control method is carried out in the DSP, and then the trigger pulse wave is issued by the FPGA.

4. An auxiliary converter phase-controlled rectification control method according to claim 3, characterized in that: The phase-locked loop in the DSP obtains the current phase of the grid-side input voltage of the thyristor rectifier module.

5. A phase-controlled rectification control method for an auxiliary converter according to claim 3 or 4, characterized in that: After the FPGA issues the trigger pulse wave, it drives the thyristor through a pulse transformer.

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