Thyristor-based three-phase bridge type slow start controller and control method

Abstract

The invention discloses a thyristor-based three-phase bridge type slow start controller and a control method, and the controller comprises an ADC collection module which is used for collecting any two line voltages of three-phase power; the main module is used for controlling the on or off of the timer 1 and the timer 2; according to the timing flag bit of the timer 1, monitoring the time interval between the change of the current line voltage from the negative voltage to the zero rising edge and the change of the last line voltage from the negative voltage to the zero rising edge; when the line voltage acquired by the ADC acquisition module is from the negative voltage to the zero rising edge and the time interval meets the condition, a starting signal is sent to the PWM1 interrupt module; according to a count value of a timer 2, when slow starting is completed, a starting signal is sent to a PWM1 interrupt module; the PWM1 interrupt module is used for outputting a PWM pulse signal to the PWM module according to the starting signal sent by the main module and a control time sequence; and the PWM module is used for turning on or turning off a thyristor in the three-phase bridge circuit according to the PWM pulse signal.

Description

Technical Field

[0001] This invention relates to a thyristor-based three-phase bridge soft-start controller and control method, belonging to the field of rectifier technology. Background Technology

[0002] In AC-to-DC power converters, large capacitors are used for filtering to stabilize the DC output voltage. Since the voltage across a capacitor cannot change abruptly, a large inrush current is generated at the moment the AC power is applied, potentially damaging electronic components. Therefore, surge suppression circuits are added to the circuit. This is typically achieved by limiting the current using a power resistor connected in series in the circuit, bypassing the resistor once the capacitor is fully charged. The disadvantages of this approach are: 1. Large power resistor size; 2. Thermal damage due to slow internal heat dissipation after repeated short-term surge currents; 3. Difficulty in detecting resistor failure; 4. The power rating of the resistor is limited by the capacitor value, charging time, and inrush current.

[0003] The patent [Soft-start circuit, method, switching power supply, device and storage medium, ZL202210221124.7, authorized invention] proposes to control the thyristors to alternately conduct in the positive and negative half-cycles of the AC voltage in a single-phase semi-controlled bridge topology to achieve surge suppression function. Although the principle is feasible, it does not clearly indicate how the DC side voltage is slowly increased, and it cannot be applied to high-power three-phase rectifier bridges.

[0004] The patent [Thyristor Rectifier Soft-Start Control Method, Device and Storage Medium, ZL202010742189.7, Authorized Invention] proposes controlling the thyristor to conduct when the phase voltage phase is within a preset conduction angle range, and increasing the thyristor conduction angle until the soft start is complete. While this allows for a slow rise in the DC-side output voltage, it has three problems: 1. Since the phase voltage is calculated and digitally filtered after acquiring the line voltage, there is inevitably a delay in data processing in the CPU. 2. Because the phase voltage phase is obtained by calculating the number of sampling cycles between two phase voltage zero-crossing points, sampling delays will inevitably lead to phase lead or lag, potentially causing incorrect thyristor control timing. 3. Due to the large amplitude of the input and output voltages, and the CPU's maximum voltage being 3.3V, a large attenuation ratio is required for digital-to-analog conversion. This conversion itself has some error; using the input and output voltage difference as a judgment condition may lead to erroneous thyristor turn-on or turn-off. Summary of the Invention

[0005] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a three-phase bridge soft start control method based on thyristors to achieve reliable soft start control.

[0006] The technical solution of this invention is: This invention discloses a soft-start controller based on a thyristor-driven three-phase bridge circuit, comprising: a main module, Timer 1, Timer 2, an ADC acquisition module, a PWM module, and a PWM1 interrupt module; wherein, The PWM module includes PWM1, PWM2, PWM3, PWM4, PWM5, and PWM6 modules; PWM1, PWM2, PWM3, PWM4, PWM5, and PWM6 modules are respectively connected to the six thyristors of the three-phase bridge circuit. The ADC acquisition module is used to acquire the line voltages of any two three-phase power lines. The main module controls the opening and closing of Timer 1 and Timer 2; based on the timing flag sent by Timer 1, it monitors the time interval between the current line voltage change from negative to zero rising edge and the previous line voltage change from negative to zero rising edge; when the line voltage acquired by the ADC acquisition module changes from negative to zero rising edge and the time interval meets the condition, it sends an enable signal to the PWM1 interrupt module; based on the count value of Timer 2, it sets the initial phase angle for each cycle and sends an enable signal to the PWM1 interrupt module. The PWM1 interrupt module outputs PWM pulse signals to the PWM module according to the control timing, based on the enable signal sent by the main module. The PWM module turns the thyristors in the three-phase bridge circuit on or off according to the PWM pulse signal. Timer 1 is used for timing and sends the timing flag to the main module. Timer 2 is used for timing and sends the count value to the main module.

[0007] Furthermore, in the aforementioned controller, the step of outputting PWM pulse signals to the PWM module according to the control timing sequence specifically includes: S91. Set the Pwm1IntCount counter to 0; S92, Pwm1IntCount counter increments by one; S93. Determine whether all PWM modules are turned off. If so, clear the Pwm1IntCount counter and disable the PWM1 interrupt. Otherwise, proceed to step S94. S94. Determine whether the Pwm1IntCount counter has reached the set value. If so, turn the PWM module on or off by outputting a PWM pulse signal; otherwise, proceed to step S92.

[0008] Furthermore, in the aforementioned controller, determining whether the Pwm1IntCount counter has reached a set value, and if so, turning the PWM module on or off by outputting a PWM pulse signal, specifically involves: If Pwm1IntCount=31, set the FLAG flag to 1 and simultaneously turn off the PWM1 module and the PWM6 module; If Pwm1IntCount=61, set the FLAG flag to 2 and simultaneously enable PWM1 and PWM2 modules; If Pwm1IntCount=91, set the FLAG flag to 3 and simultaneously turn off the PWM1 module and the PWM2 module; If Pwm1IntCount=121, set the FLAG flag to 4 and simultaneously turn on the PWM2 and PWM3 modules; If Pwm1IntCount=151, set the FLAG flag to 5, and simultaneously turn off the PWM2 and PWM3 modules; If Pwm1IntCount=181, set the FLAG flag to 6 and simultaneously enable the PWM3 and PWM4 modules; If Pwm1IntCount=211, set the FLAG flag to 7 and simultaneously turn off the PWM3 and PWM4 modules; If Pwm1IntCount=241, set the FLAG flag to 8 and simultaneously enable the PWM4 and PWM5 modules; If Pwm1IntCount=271, set the FLAG flag to 9, and simultaneously turn off the PWM4 and PWM5 modules; If Pwm1IntCount=301, set the FLAG flag to 10 and simultaneously enable the PWM5 and PWM6 modules; If Pwm1IntCount=331, set the FLAG flag to 11 and simultaneously turn off the PWM5 and PWM6 modules.

[0009] This invention discloses a control method for a soft-start controller using a thyristor-based three-phase bridge circuit, comprising: S1. Set the Timer1 flag bit Timer1Flag=1, initialize the Timer1 count value Timer1Count and the Timer2 count value Timer2Count, and set the FLAG bit to 0; S2. Determine whether the line voltage output by the three-phase bridge circuit acquired by the ADC acquisition module is the rising edge from negative voltage to zero voltage. If yes, proceed to step S3; otherwise, repeat step S2. S3. Determine if the Timer1Flag flag is 1; if yes, enable the Timer1 interrupt, update the Timer1 count value Timer1Count, enable the Timer2 interrupt, update the Timer2 count value Timer2Count, set Timer1Flag=0, and proceed to step S4; otherwise, proceed directly to step S4. S4. Determine whether the Timer2Count value is equal to 0 and whether the flag bit FLAG is 11. If yes, the soft start is completed, Timer2 is turned off, PWM1 interrupt is enabled to turn the thyristor on or off, and the value of the flag bit FLAG is updated. Otherwise, repeat step S2.

[0010] Furthermore, in the above method, the interruption of Timer 1 is specifically as follows: S21. Decrement the Timer1Count value by 1; S22. Determine if the Timer1Count value is 0. If it is, set Timer1Flag=1 and disable the Timer1 interrupt; otherwise, repeat step S21.

[0011] Furthermore, in the above method, the interruption of Timer 2 is specifically as follows: S31. Decrement the Timer2Count value by 1; S32. Determine if the Timer2Count value is 0. If it is, disable the Timer2 interrupt. Assign an initial value to the Timer2Count value according to the initial phase angle of each cycle. Enable the PWM1 interrupt. Otherwise, repeat step S31.

[0012] Furthermore, in the above method, the PWM1 interrupt specifically refers to: S41, Pwm1IntCount counter increments by one; S42. Determine whether all PWM modules are turned off. If so, clear the Pwm1IntCount counter and disable the PWM1 interrupt. Otherwise, proceed to step S43. S43. Determine whether the Pwm1IntCount counter has reached the set value. If so, turn the PWM module on or off by outputting a PWM pulse signal; otherwise, proceed to step S41.

[0013] Furthermore, in the above method, determining whether the Pwm1IntCount counter has reached the set value, and if so, turning the PWM module on or off by outputting a PWM pulse signal, specifically involves: If Pwm1IntCount=31, set the FLAG flag to 1 and simultaneously turn off the PWM1 module and the PWM6 module; If Pwm1IntCount=61, set the FLAG flag to 2 and simultaneously enable PWM1 and PWM2 modules; If Pwm1IntCount=91, set the FLAG flag to 3 and simultaneously turn off the PWM1 module and the PWM2 module; If Pwm1IntCount=121, set the FLAG flag to 4 and simultaneously turn on the PWM2 and PWM3 modules; If Pwm1IntCount=151, set the FLAG flag to 5, and simultaneously turn off the PWM2 and PWM3 modules; If Pwm1IntCount=181, set the FLAG flag to 6 and simultaneously enable the PWM3 and PWM4 modules; If Pwm1IntCount=211, set the FLAG flag to 7 and simultaneously turn off the PWM3 and PWM4 modules; If Pwm1IntCount=241, set the FLAG flag to 8 and simultaneously enable the PWM4 and PWM5 modules; If Pwm1IntCount=271, set the FLAG flag to 9, and simultaneously turn off the PWM4 and PWM5 modules; If Pwm1IntCount=301, set the FLAG flag to 10 and simultaneously enable the PWM5 and PWM6 modules; If Pwm1IntCount=331, set the FLAG flag to 11 and simultaneously turn off the PWM5 and PWM6 modules.

[0014] Furthermore, in the above method, the initialization of Timer1Count and Timer2Count specifically involves: initializing Timer1Count to the count value corresponding to 15ms, and initializing Timer2Count to the count value corresponding to the phase of the line voltage AC at 120 degrees. Furthermore, in the above method, the PWM pulse signal is a double narrow pulse, which turns off or on the PWM1~PWM6 modules, respectively triggering the thyristors T1~T6 to turn off or on.

[0015] The advantages of this invention over the prior art are as follows: (1) The present invention gradually increases the voltage across the output capacitor by controlling the phase of the input line voltage of the thyristor from 120 degrees to 0 degrees in cycle by cycle.

[0016] (2) The present invention can achieve soft start control without sampling the amplitude of multiple phase voltages or line voltages, which greatly reduces the resources of the CPU system and avoids phase lead or lag caused by ADC sampling delay or filtering circuit, thus greatly increasing the reliability of the system.

[0017] (3) In this invention, the RC slow-pull circuit connected in parallel across the two ends of the thyristor may cause the input line voltage to fluctuate up and down at the zero crossing point, thus affecting the control function. Using a time interval of more than 15ms to determine whether the zero crossing is valid is a simple, easy and reliable method.

[0018] (4) The present invention has a control strategy of reducing the phase by a fixed angle in the gradual start-up phase until it becomes zero. Since the phase decreases linearly to zero, the intermediate control link does not need to be superimposed with the voltage phase acquisition link. Therefore, the control process is simple and reliable, which is conducive to the slow increase of the voltage on the output capacitor until it reaches the full voltage state.

[0019] (5) The present invention uses the counting pulse count method to realize PWM control, which is conducive to the modularization of the program. It also uses 6 thyristor PWM drive series timing control logic to avoid bridge arm shoot-through phenomenon. At the same time, the series control flag bit method greatly improves the robustness of the system. Attached Figure Description

[0020] Figure 1 This is the schematic diagram of the three-phase thyristor circuit of the present invention; Figure 2 This is the timing control logic diagram of the three-phase thyristor of this invention (after soft start-up); Figure 3 This is a flowchart of the three-phase thyristor control strategy of the present invention; Figure 4 This is a flowchart of the counting pulse algorithm of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] This invention discloses a soft-start controller based on a thyristor-driven three-phase bridge circuit, comprising: a main module, Timer 1, Timer 2, an ADC acquisition module, a PWM module, and a PWM1 interrupt module; wherein, The PWM module includes PWM1, PWM2, PWM3, PWM4, PWM5, and PWM6 modules; PWM1, PWM2, PWM3, PWM4, PWM5, and PWM6 modules are respectively connected to the six thyristors of the three-phase bridge circuit. The ADC acquisition module is used to acquire the line voltages of any two three-phase power lines. The main module controls the opening and closing of Timer 1 and Timer 2; based on the timing flag sent by Timer 1, it monitors the time interval between the current line voltage change from negative to zero rising edge and the previous line voltage change from negative to zero rising edge; when the line voltage acquired by the ADC acquisition module changes from negative to zero rising edge and the time interval meets the condition, it sends an enable signal to the PWM1 interrupt module; based on the count value of Timer 2, when the soft start is completed, it sends an enable signal to the PWM1 interrupt module. The PWM1 interrupt module outputs PWM pulse signals to the PWM module according to the control timing, based on the enable signal sent by the main module. The PWM module turns the thyristors in the three-phase bridge circuit on or off according to the PWM pulse signal. Timer 1 is used for timing and sends the timing flag to the main module. Timer 2 is used for timing and sends the count value to the main module.

[0023] Preferably, PWM pulse signals are output to the PWM module according to the control timing sequence, specifically as follows: S91. Set the Pwm1IntCount counter to 0; S92, Pwm1IntCount counter increments by one; S93. Determine whether all PWM modules are turned off. If so, clear the Pwm1IntCount counter and disable the PWM1 interrupt. Otherwise, proceed to step S94. S94. Determine whether the Pwm1IntCount counter has reached the set value. If so, turn the PWM module on or off by outputting a PWM pulse signal; otherwise, proceed to step S92.

[0024] Preferably, it is determined whether the Pwm1IntCount counter has reached the set value. If so, the PWM module is turned on or off by outputting a PWM pulse signal. Specifically: If Pwm1IntCount=31, set the FLAG flag to 1 and simultaneously turn off the PWM1 module and the PWM6 module; If Pwm1IntCount=61, set the FLAG flag to 2 and simultaneously enable PWM1 and PWM2 modules; If Pwm1IntCount=91, set the FLAG flag to 3 and simultaneously turn off the PWM1 module and the PWM2 module; If Pwm1IntCount=121, set the FLAG flag to 4 and simultaneously turn on the PWM2 and PWM3 modules; If Pwm1IntCount=151, set the FLAG flag to 5, and simultaneously turn off the PWM2 and PWM3 modules; If Pwm1IntCount=181, set the FLAG flag to 6 and simultaneously enable the PWM3 and PWM4 modules; If Pwm1IntCount=211, set the FLAG flag to 7 and simultaneously turn off the PWM3 and PWM4 modules; If Pwm1IntCount=241, set the FLAG flag to 8 and simultaneously enable the PWM4 and PWM5 modules; If Pwm1IntCount=271, set the FLAG flag to 9, and simultaneously turn off the PWM4 and PWM5 modules; If Pwm1IntCount=301, set the FLAG flag to 10 and simultaneously enable the PWM5 and PWM6 modules; If Pwm1IntCount=331, set the FLAG flag to 11 and simultaneously turn off the PWM5 and PWM6 modules.

[0025] This invention discloses a control method for a soft-start controller using a thyristor-based three-phase bridge circuit, comprising: S1. Set the Timer1 flag bit Timer1Flag=1, initialize the Timer1 count value Timer1Count and the Timer2 count value Timer2Count, and set the FLAG bit to 0; S2. Determine whether the line voltage output by the three-phase bridge circuit acquired by the ADC acquisition module is the rising edge from negative voltage to zero voltage. If yes, proceed to step S3; otherwise, repeat step S2. S3. Determine if the Timer1Flag flag is 1; if yes, enable the Timer1 interrupt, update the Timer1 count value Timer1Count, enable the Timer2 interrupt, update the Timer2 count value Timer2Count, set Timer1Flag=0, and proceed to step S4; otherwise, proceed directly to step S4. S4. Determine whether the Timer2Count value is equal to 0 and whether the flag bit FLAG is 11. If yes, the soft start is completed, Timer2 is turned off, PWM1 interrupt is enabled to turn the thyristor on or off, and the value of the flag bit FLAG is updated. Otherwise, repeat step S2.

[0026] Preferably, the Timer 1 interrupt is as follows: S21. Decrement the Timer1Count value by 1; S22. Determine if the Timer1Count value is 0. If it is, enter the Timer1 interrupt subroutine and set Timer1Flag=1 to disable the Timer1 interrupt. Otherwise, repeat step S21.

[0027] Preferably, the timer 2 interrupt is as follows: S31. Decrement the Timer2Count value by 1; S32. Determine if the Timer2Count value is 0. If it is, enter the Timer2 interrupt subroutine and disable the Timer2 interrupt. Each time the interrupt subroutine is entered, the Timer2Count value is reassigned. The new value is the time from when the timer is started to when Timer2 is entered, which is the phase angle of the line voltage. In other words, each time Timer2 is entered, the initial phase angle of the line voltage is shifted forward from the initial 120 degrees to 0 degrees when the soft start is completed. At the same time, the PWM1 interrupt needs to be enabled each time Timer2 is entered. Otherwise, repeat step S31.

[0028] Preferably, the PWM1 interrupt is as follows: S41, Pwm1IntCount counter increments by one; S42. Determine whether all PWM modules are turned off. If so, clear the Pwm1IntCount counter and disable the PWM1 interrupt. Otherwise, proceed to step S43. S43. Determine whether the Pwm1IntCount counter has reached the set value. If so, turn the PWM module on or off by outputting a PWM pulse signal; otherwise, proceed to step S41.

[0029] Preferably, it is determined whether the Pwm1IntCount counter has reached the set value. If so, the PWM module is turned on or off by outputting a PWM pulse signal. Specifically: If Pwm1IntCount=31, set the FLAG flag to 1 and simultaneously turn off the PWM1 module and the PWM6 module; If Pwm1IntCount=61, set the FLAG flag to 2 and simultaneously enable PWM1 and PWM2 modules; If Pwm1IntCount=91, set the FLAG flag to 3 and simultaneously turn off the PWM1 module and the PWM2 module; If Pwm1IntCount=121, set the FLAG flag to 4 and simultaneously turn on the PWM2 and PWM3 modules; If Pwm1IntCount=151, set the FLAG flag to 5, and simultaneously turn off the PWM2 and PWM3 modules; If Pwm1IntCount=181, set the FLAG flag to 6 and simultaneously enable the PWM3 and PWM4 modules; If Pwm1IntCount=211, set the FLAG flag to 7 and simultaneously turn off the PWM3 and PWM4 modules; If Pwm1IntCount=241, set the FLAG flag to 8 and simultaneously enable the PWM4 and PWM5 modules; If Pwm1IntCount=271, set the FLAG flag to 9, and simultaneously turn off the PWM4 and PWM5 modules; If Pwm1IntCount=301, set the FLAG flag to 10 and simultaneously enable the PWM5 and PWM6 modules; If Pwm1IntCount=331, set the FLAG flag to 11 and simultaneously turn off the PWM5 and PWM6 modules.

[0030] Preferably, the timer 1 count value Timer1Count and the timer 2 count value Timer2Count are initialized as follows: the timer 1 count value Timer1Count is initialized to the count value corresponding to 15ms time, and the timer 2 count value Timer2Count is initialized to the count value corresponding to the phase of the line voltage AC at 120 degrees. Preferably, the PWM pulse signal is a double narrow pulse, which turns off or on the PWM1~PWM6 modules, respectively triggering the thyristors T1~T6 to turn off or on.

[0031] Example In this embodiment, as Figure 1 As shown, a three-phase bridge circuit based on thyristors includes: thyristors T1, T2, T3, T4, T5, T6 and capacitor C1; wherein, A in the three-phase circuit is connected to the anode of T1 and the cathode of T4; B in the three-phase circuit is connected to the anode of T3 and the cathode of T6; C in the three-phase circuit is connected to the anode of T5 and the cathode of T2; T1, T3, and T5 share a common cathode connected to the positive terminal of C1, and T2, T4, and T6 share a common anode connected to the negative terminal of C1.

[0032] The controller performs soft-start timing control on thyristors T1, T2, T3, T4, T5, and T6.

[0033] like Figure 3 As shown, this embodiment provides a three-phase bridge soft-start control method based on thyristors, comprising the following steps: 1. The preset initial phase (less than 120 degrees, i.e. 6.66ms) is calculated starting from the moment the line voltage crosses zero (from negative to positive). Once the initial phase is reached, the 6 PWM channels are turned on sequentially with a fixed number of pulses.

[0034] 2. Timing starts when the line voltage crosses zero. If the line voltage crosses zero again (from negative to positive) after more than 15ms, the zero-crossing time is valid; otherwise, it is invalid.

[0035] 3. Decrease the initial phase at a fixed angle (which can be set arbitrarily) cycle by cycle until it is reduced to zero, thus completing the soft start.

[0036] 4. After the start-up is completed, the zero-crossing moment of the line voltage is detected cycle by cycle, and the 6 PWM channels are turned on sequentially with a fixed number of pulses cycle by cycle.

[0037] like Figure 1 The diagram shows the schematic of a three-phase thyristor circuit, mainly composed of thyristors T1, T2, T3, T4, T5, and T6. Phase A of the three-phase circuit is connected to the anode of T1 and the cathode of T4; phase B is connected to the anode of T3 and the cathode of T6; and phase C is connected to the anode of T5 and the cathode of T2. T1, T3, and T5 share a common anode and are connected to the positive terminal of capacitor C1, while T2, T4, and T6 share a common cathode and are connected to the negative terminal of C1.

[0038] Timer 1 is used to determine the time interval of the line voltage to avoid external interrupts being falsely triggered by oscillations when the line voltage crosses zero; Timer 2 is used to set the line voltage phase corresponding to the soft start and control the soft start process.

[0039] Determine the time interval between the current interrupt entry and the previous interrupt entry. If the condition is met, start Timer 1 and Timer 2.

[0040] Determine if the count value of Timer 2 has decreased to zero (soft start complete). If the condition is met, turn off Timer 2, send PWM1 and PWM6 pulses, and enable PWM1 interrupt at the same time.

[0041] like Figure 2 The diagram shown is the timing control logic diagram of the three-phase thyristors after the soft start-up is completed. The specific steps are as follows.

[0042] 1) When the phase of the online voltage AC is 0 degrees, turn on thyristors T1 and T6 simultaneously; 2) When the phase of the online voltage AC is 60 degrees, turn on thyristors T1 and T2 simultaneously (turn off thyristor T6 before this). 3) When the phase of the online voltage AC is 120 degrees, turn on thyristors T3 and T2 simultaneously (turn off thyristor T1 before this). 4) When the phase of the online voltage AC is 180 degrees, turn on thyristors T3 and T4 simultaneously (turn off thyristor T2 before this). 5) When the phase of the online voltage AC is 240 degrees, turn on thyristors T5 and T4 simultaneously (turn off thyristor T3 before this). 6) When the phase of the online voltage AC is 300 degrees, turn on thyristors T5 and T6 simultaneously (turn off thyristor T4 before this). 7) When the phase of the online voltage AC is 360 degrees, turn on thyristors T6 and T1 simultaneously (turn off thyristor T5 before this). 8) Repeat steps 1 through 7.

[0043] like Figure 3 The diagram shown is a flowchart of the three-phase thyristor control strategy. The specific steps are as follows.

[0044] 1) Set the initial value of the timer. In Timer 1, set the count value corresponding to 15ms time. Set the Timer 1 flag bit Timer1Flag=1. In Timer 2, set the count value corresponding to the phase of the line voltage AC at 120 degrees (i.e., (120 degrees / 360 degrees)*20ms=6.66ms) (let's call it Timer2Count, say 6000). Set the PWM1 interrupt count value Pwm1IntCount=1.

[0045] 2) Initialize Timer 1 module, Timer 2 module, ADC acquisition module, PWM1 module, PWM2 module, PWM3 module, PWM4 module, PWM5 module, PWM6 module, and external interrupt module.

[0046] 3) Set Timer1Flag=1 in the Timer1 interrupt subroutine.

[0047] 4) In the Timer 2 interrupt subroutine, set: 1. Enable PWM1 interrupt; 2. Initial phase angle of line voltage, i.e., reassign initial value; Timer2Count count value, each time Timer 2 is entered, it will be reduced from 6000 to 60. That is to say, the time taken to enter Timer 2 for the first time is 6000 count points, the time taken to enter Timer 2 for the second time is 5940 count points, and so on, until it is reduced to 0, i.e., the soft start is completed.

[0048] 5) When the line voltage AC meets the condition of rising edge from negative to zero, the external interrupt module is triggered. The external interrupt performs two functions: First, it checks if the time interval between the current interrupt entry and the previous entry is greater than 15ms (checking if Timer1Flag equals 1). If the condition is met, Timer 1 and Timer 2 are started, and Timer1Flag is set to 0. If the condition is not met, the interrupt is exited and awaits a second re-entry. Second, it checks if the soft start is complete (checking if Timer2Count equals 0). If the condition is met, Timer 2 is turned off, PWM1 and PWM6 pulses are emitted, and PWM1 interrupt is enabled. If the condition is not met, the interrupt is exited and awaits a second re-entry.

[0049] 6) In the PWM1 interrupt subroutine, set: 1. Increment the Pwm1IntCount counter by one each time an interrupt is entered; 2. When the Pwm1IntCount counter reaches the set value, turn on or off the corresponding PWM pulse; 3. Clear the Pwm1IntCount counter to zero after all PWM pulses are turned off.

[0050] like Figure 4 The diagram shows the flowchart of the three-phase thyristor counting pulse algorithm. The specific steps are as follows.

[0051] Note: This article uses 55.5µs (20ms / 360 degrees, approximately 1 degree) as one interrupt cycle (i.e., the switching cycle of PWM1~PWM6 is 55.5µs, equivalent to a switching frequency of 18kHz). Each PWM1 interrupt increments the count value (PWM1Count) by 1. A dual narrow pulse method is used to trigger the thyristors: one thyristor turns on for 30 degrees, turns off for 30 degrees, turns on again for 30 degrees, and then turns off again. PWM1 controls thyristor T1, PWM2 controls thyristor T2, PWM3 controls thyristor T3, PWM4 controls thyristor T4, PWM5 controls thyristor T5, and PWM6 controls thyristor T6.

[0052] 1) When the program reaches the process of turning on the thyristor in the manner of counting pulses, PWM1 and PWM6 are turned on at the same time; 2) When PWM1Count=31 (equivalent to a phase of 30 degrees for the line voltage AC), set the FLAG flag to 1 and simultaneously turn off PWM1 and PWM6; otherwise, end the process. 3) When PWM1Count=61 (equivalent to a 60-degree phase of the line voltage AC), set the FLAG flag to 2 and simultaneously turn on PWM1 and PWM2; otherwise, end the process. 4) When PWM1Count=91 (equivalent to the phase of line voltage AC being 90 degrees), set the FLAG flag to 3 and simultaneously turn off PWM1 and PWM2; otherwise, end the process. 5) When PWM1Count=121 (equivalent to the phase of line voltage AC being 120 degrees), set the FLAG flag to 4 and simultaneously turn on PWM2 and PWM3; otherwise, end the process. 6) When PWM1Count = 151 (equivalent to a phase of 150 degrees for the line voltage AC), set the FLAG flag to 5 and simultaneously turn off PWM2 and PWM3; otherwise, end the process. 7) When PWM1Count=181 (equivalent to the phase of line voltage AC being 180 degrees), set the FLAG flag to 6 and simultaneously enable PWM3 and PWM4; otherwise, end the process. 8) When PWM1Count = 211 (equivalent to a phase of 210 degrees for the line voltage AC), set the FLAG flag to 7 and simultaneously turn off PWM3 and PWM4; otherwise, end the process. 9) When PWM1Count = 241 (equivalent to a phase of 240 degrees for the line voltage AC), set the FLAG flag to 8 and simultaneously enable PWM4 and PWM5; otherwise, end the process. 10) When PWM1Count = 271 (equivalent to a phase of 270 degrees for the line voltage AC), set the FLAG flag to 9 and simultaneously turn off PWM4 and PWM5; otherwise, end the process. 11) When PWM1Count=301 (equivalent to the phase of line voltage AC being 300 degrees), set the FLAG flag to 10 and simultaneously enable PWM5 and PWM6; otherwise, end the process. 12) When PWM1Count = 331 (equivalent to the phase of line voltage AC being 330 degrees), set the FLAG flag to 11 and simultaneously turn off PWM5 and PWM6; otherwise, end the process. After the soft start is complete, the FLAG flag is set to 11 as the condition for the next cycle. If this condition is met, execution will proceed. Figure 2 Timing control logic (i.e.) Figure 4 If the conditions for step 1 to step 12 are not met, the current cycle will end and a new start-up judgment will be performed.

[0053] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0054] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A soft-start controller for a three-phase bridge circuit based on thyristors, characterized in that, include: The main module, Timer 1, Timer 2, ADC acquisition module, PWM module, and PWM1 interrupt module; among them, The PWM module includes PWM1, PWM2, PWM3, PWM4, PWM5, and PWM6 modules; PWM1, PWM2, PWM3, PWM4, PWM5, and PWM6 modules are respectively connected to the six thyristors of the three-phase bridge circuit. The ADC acquisition module is used to acquire the line voltages of any two three-phase power lines. The main module controls the opening and closing of Timer 1 and Timer 2; based on the timing flag sent by Timer 1, it monitors the time interval between the current line voltage change from negative to zero rising edge and the previous line voltage change from negative to zero rising edge; when the line voltage acquired by the ADC acquisition module changes from negative to zero rising edge and the time interval meets the condition, it sends an enable signal to the PWM1 interrupt module; based on the count value of Timer 2, it sets the initial phase angle for each cycle and sends an enable signal to the PWM1 interrupt module. The PWM1 interrupt module outputs PWM pulse signals to the PWM module according to the control timing, based on the enable signal sent by the main module. The PWM module turns the thyristors in the three-phase bridge circuit on or off according to the PWM pulse signal. Timer 1 is used for timing and sends the timing flag to the main module. Timer 2 is used for timing and sends the count value to the main module.

2. The soft-start controller for a three-phase bridge circuit based on thyristors according to claim 1, characterized in that: The step of outputting PWM pulse signals to the PWM module according to the control timing sequence is as follows: S91. Set the Pwm1IntCount counter to 0; S92, Pwm1IntCount counter increments by one; S93. Determine whether all PWM modules are turned off. If so, clear the Pwm1IntCount counter and disable the PWM1 interrupt. Otherwise, proceed to step S94. S94. Determine whether the Pwm1IntCount counter has reached the set value. If so, turn the PWM module on or off by outputting a PWM pulse signal; otherwise, proceed to step S92.

3. A soft-start controller for a three-phase bridge circuit based on thyristors according to claim 2, characterized in that: The determination of whether the Pwm1IntCount counter has reached the set value, and if so, the PWM module is turned on or off by outputting a PWM pulse signal, specifically as follows: If Pwm1IntCount=31, set the FLAG flag to 1 and simultaneously turn off the PWM1 module and the PWM6 module; If Pwm1IntCount=61, set the FLAG flag to 2 and simultaneously enable PWM1 and PWM2 modules; If Pwm1IntCount=91, set the FLAG flag to 3 and simultaneously turn off the PWM1 module and the PWM2 module; If Pwm1IntCount=121, set the FLAG flag to 4 and simultaneously turn on the PWM2 and PWM3 modules; If Pwm1IntCount=151, set the FLAG flag to 5, and simultaneously turn off the PWM2 and PWM3 modules; If Pwm1IntCount=181, set the FLAG flag to 6 and simultaneously enable the PWM3 and PWM4 modules; If Pwm1IntCount=211, set the FLAG flag to 7 and simultaneously turn off the PWM3 and PWM4 modules; If Pwm1IntCount=241, set the FLAG flag to 8 and simultaneously enable the PWM4 and PWM5 modules; If Pwm1IntCount=271, set the FLAG flag to 9 and simultaneously turn off the PWM4 and PWM5 modules; If Pwm1IntCount=301, set the FLAG flag to 10 and simultaneously enable the PWM5 and PWM6 modules; If Pwm1IntCount=331, set the FLAG flag to 11 and simultaneously turn off the PWM5 and PWM6 modules.

4. The control method for a thyristor-based three-phase bridge circuit soft-start controller as described in claim 1, characterized in that, include: S1. Set the Timer1 flag bit Timer1Flag=1, initialize the Timer1 count value Timer1Count and the Timer2 count value Timer2Count, and set the FLAG bit to 0; S2. Determine whether the line voltage output by the three-phase bridge circuit acquired by the ADC acquisition module is the rising edge from negative voltage to zero voltage. If yes, proceed to step S3; otherwise, repeat step S2. S3. Determine if the Timer1Flag flag is 1; if yes, enable the Timer1 interrupt, update the Timer1 count value Timer1Count, enable the Timer2 interrupt, update the Timer2 count value Timer2Count, set Timer1Flag=0, and proceed to step S4; otherwise, proceed directly to step S4. S4. Determine whether the Timer2Count value is equal to 0 and whether the flag bit FLAG is 11. If yes, the soft start is completed, Timer2 is turned off, PWM1 interrupt is enabled to turn the thyristor on or off, and the value of the flag bit FLAG is updated. Otherwise, repeat step S2.

5. The three-phase bridge soft-start control method based on thyristors according to claim 4, characterized in that: The interrupt of Timer 1 is specifically as follows: S21. Decrement the Timer1Count value by 1; S22. Determine if the Timer1Count value is 0. If it is, set Timer1Flag=1 and disable the Timer1 interrupt; otherwise, repeat step S21.

6. The three-phase bridge soft-start control method based on thyristors according to claim 4, characterized in that: The Timer 2 interrupt is specifically as follows: S31. Decrement the Timer2Count value by 1; S32. Determine if the Timer2Count value is 0. If it is, disable the Timer2 interrupt. Assign an initial value to the Timer2Count value according to the initial phase angle of each cycle. Enable the PWM1 interrupt. Otherwise, repeat step S31.

7. The three-phase bridge soft-start control method based on thyristors according to claim 4, characterized in that: The PWM1 interrupt is specifically as follows: S41, Pwm1IntCount counter increments by one; S42. Determine whether all PWM modules are turned off. If so, clear the Pwm1IntCount counter and disable the PWM1 interrupt. Otherwise, proceed to step S43. S43. Determine whether the Pwm1IntCount counter has reached the set value. If so, turn the PWM module on or off by outputting a PWM pulse signal; otherwise, proceed to step S41.

8. The three-phase bridge soft-start control method based on thyristors according to claim 7, characterized in that: The determination of whether the Pwm1IntCount counter has reached the set value, and if so, the PWM module is turned on or off by outputting a PWM pulse signal, specifically as follows: If Pwm1IntCount=31, set the FLAG flag to 1 and simultaneously turn off the PWM1 module and the PWM6 module; If Pwm1IntCount=61, set the FLAG flag to 2 and simultaneously enable PWM1 and PWM2 modules; If Pwm1IntCount=91, set the FLAG flag to 3 and simultaneously turn off the PWM1 module and the PWM2 module; If Pwm1IntCount=121, set the FLAG flag to 4 and simultaneously turn on the PWM2 and PWM3 modules; If Pwm1IntCount=151, set the FLAG flag to 5, and simultaneously turn off the PWM2 and PWM3 modules; If Pwm1IntCount=181, set the FLAG flag to 6 and simultaneously enable the PWM3 and PWM4 modules; If Pwm1IntCount=211, set the FLAG flag to 7 and simultaneously turn off the PWM3 and PWM4 modules; If Pwm1IntCount=241, set the FLAG flag to 8 and simultaneously enable the PWM4 and PWM5 modules; If Pwm1IntCount=271, set the FLAG flag to 9 and simultaneously turn off the PWM4 and PWM5 modules; If Pwm1IntCount=301, set the FLAG flag to 10 and simultaneously enable the PWM5 and PWM6 modules; If Pwm1IntCount=331, set the FLAG flag to 11 and simultaneously turn off the PWM5 and PWM6 modules.

9. A three-phase bridge soft-start control method based on thyristors according to claim 4, characterized in that: The initialization of Timer1Count and Timer2Count specifically involves: initializing Timer1Count to the count value corresponding to 15ms, and initializing Timer2Count to the count value corresponding to the phase of the line voltage AC at 120 degrees.

10. A three-phase bridge soft-start control method based on thyristors according to claim 4, characterized in that: The PWM pulse signal is a double narrow pulse, which turns off or on the PWM1~PWM6 modules, respectively triggering the thyristors T1~T6 to turn off or on.

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