Conversion control method of power supply parallel conversion device and power supply parallel conversion device

Abstract

This invention discloses a conversion control method for a power supply parallel conversion device. By monitoring the actual driving voltage of the actuator switch and using the relationship data between the closing action time and the driving voltage, this invention obtains a more accurate closing action time for the actuator switch, thereby avoiding large circulating currents when power supplies are connected in parallel. Furthermore, this invention further corrects the relationship data between the closing action time and the driving voltage in real time based on historical data of the actual driving voltage and the actual closing action time, thus ensuring that the actuator switch can close at the desired closing phase angle within its electrical lifespan, avoiding excessive circulating currents and guaranteeing the normal operation of the power supply system.

Description

Technical Field

[0001] This invention relates to power conversion devices, and more particularly to a power parallel conversion device. Background Technology

[0002] Automatic power transfer switches are widely used in industrial power supply systems. When the main power supply fails, the main power switch is disconnected first, and then the standby power switch is closed to supply power to the load. When the main power supply is restored, the standby power switch is disconnected first, and then the main power switch is closed to supply power to the load. This operation of disconnecting and then closing can cause a short-term power outage to the load. For industries with high requirements for power supply continuity, such as petrochemicals, telecommunications, and hospitals, a power outage can cause significant losses. Therefore, in such situations, automatic transfer switches are needed to perform a pre-close-then-open operation. For example, when the main power supply is restored to normal, the main power switch is closed first, and then the standby power switch is opened. This parallel power transfer operation requires the phase sequence, voltage difference, frequency difference, and phase difference of the two power supplies to be detected before the closing operation. The transfer can only proceed when the conditions are met to avoid large loop currents that could cause the power switch to trip. However, the operating time of the power switch varies with each operation, and the operating time also varies under different driving voltages. Furthermore, as the number of times the power switch operates increases, the operating time at the end of the switch's lifespan may differ from that of a new switch. By the time the power switch completes its operation, the detection conditions may no longer meet the requirements, which could lead to a large circulating current between the two power supplies, causing the power switch to trip and preventing it from continuing to supply power to the load.

[0003] To address the aforementioned issues, some existing parallel power conversion devices take into account the closing action time of the actuator switches. However, the closing action time of the actuator switches used in these devices is a fixed value obtained through statistical analysis. It does not consider the differences in closing action time between different actuator switches, the impact of the actual driving voltage on the closing action time of the actuator switches, or the changes in the closing action time of the actuator switches after a certain electrical lifespan. These changes will affect the desired closing phase angle, thereby affecting the amplitude of the loop current and potentially causing the actuator switches to trip. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a conversion control method for a power supply parallel conversion device, which can more effectively avoid the situation where the large circulating current between the two power supplies causes the actuator switch to trip and the load to lose power.

[0005] The present invention specifically adopts the following technical solutions to solve the above-mentioned technical problems:

[0006] A conversion control method for a power parallel conversion device, the power parallel conversion device including a set of execution switches respectively connected to two or more power supplies; the specific steps of the conversion control method are as follows: Step 1, confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and the voltage difference and frequency difference are within a preset range. If not, the conversion fails; if yes, proceed to step 2.

[0007] Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch.

[0008] Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails.

[0009] Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power supply, and after time t6, send a tripping command to the execution switch corresponding to the power supply to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state, and t5 is the tripping action time of the execution switch corresponding to the power supply to be converted.

[0010] Furthermore, the conversion control method of the power parallel conversion device further includes: real-time monitoring of the actual closing action time and actual driving voltage of each actuator switch for each closing operation, and recording the normal closing action data where both the actual closing action time and actual driving voltage are within a preset range. Then, based on the recorded normal closing action data, the closing action time-driving voltage correspondence data of each actuator switch is corrected according to the following method: starting from the number of recorded normal closing actions reaching a preset number J, after each normal closing, the closing action time corresponding to the actual driving voltage of this normal closing action is found from the current closing action time-driving voltage correspondence data, and updated using the average of the actual closing action times of the most recent M normal closing actions. <M≤J。

[0011] Preferably, the optimal power supply is selected from the two or more power supplies in real time based on the power supply voltage to power each actuator switch.

[0012] Based on the same inventive concept, the following technical solutions can also be obtained:

[0013] A power supply parallel conversion device includes a set of actuator switches respectively connected to two or more power supplies; the power supply parallel conversion device further includes a control unit for performing conversion control according to the following method:

[0014] Step 1: Confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and whether the voltage difference and frequency difference are within the preset range. If not, the conversion will fail; if yes, proceed to step 2.

[0015] Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch.

[0016] Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails.

[0017] Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power supply, and after time t6, send a tripping command to the execution switch corresponding to the power supply to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state, and t5 is the tripping action time of the execution switch corresponding to the power supply to be converted.

[0018] Furthermore, the control unit also includes a data correction module, used to monitor in real time the actual closing action time and actual driving voltage of each actuator switch for each closing operation, and to record normal closing action data where both the actual closing action time and actual driving voltage are within a preset range. Then, based on the recorded normal closing action data, the closing action time-driving voltage correspondence data of each actuator switch is corrected using the following method: starting from when the number of recorded normal closing actions reaches a preset number J, after each normal closing operation, the closing action time corresponding to the actual driving voltage of this normal closing action is found from the current closing action time-driving voltage correspondence data, and updated using the average of the actual closing action times of the most recent M normal closing actions. <M≤J。

[0019] Preferably, the power supply parallel conversion device further includes a power selection circuit, used to select the optimal power supply from the two or more power supplies in real time according to the power supply voltage to supply power to each execution switch.

[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects;

[0021] This invention monitors the actual driving voltage of the actuator switch and obtains a more accurate closing action time of the actuator switch based on the relationship data between the closing action time and the driving voltage, thereby avoiding large circulating currents when power supplies are connected in parallel. Furthermore, this invention further corrects the relationship data between the closing action time and the driving voltage in real time based on historical data of the actual driving voltage and the actual closing action time, thereby ensuring that the actuator switch can close at the expected closing phase angle within its electrical life, avoiding excessive circulating currents and ensuring the normal operation of the power supply system. Attached Figure Description

[0022] Figure 1 This is a structural block diagram of a specific embodiment of the power parallel conversion device of the present invention;

[0023] Figure 2 A schematic diagram illustrating the principle for determining the timing of the closing command. Detailed Implementation

[0024] To address the shortcomings of existing technologies, the present invention addresses this issue by considering the relationship between the closing action time of the actuator switch and the driving voltage during the parallel power supply conversion control process. By monitoring the actual driving voltage of the actuator switch and using the data on the relationship between the closing action time and the driving voltage, a more accurate closing action time of the actuator switch can be obtained, thereby avoiding large circulating currents during parallel power supply operation.

[0025] The specific technical solution proposed in this invention is as follows:

[0026] A conversion control method for a power parallel conversion device, the power parallel conversion device including a set of execution switches respectively connected to two or more power supplies; the specific steps of the conversion control method are as follows: Step 1, confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and the voltage difference and frequency difference are within a preset range. If not, the conversion fails; if yes, proceed to step 2.

[0027] Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch.

[0028] Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails.

[0029] Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power supply, and after time t6, send a tripping command to the execution switch corresponding to the power supply to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state, and t5 is the tripping action time of the execution switch corresponding to the power supply to be converted.

[0030] A power supply parallel conversion device includes a set of actuator switches respectively connected to two or more power supplies; the power supply parallel conversion device further includes a control unit for performing conversion control according to the following method:

[0031] Step 1: Confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and whether the voltage difference and frequency difference are within the preset range. If not, the conversion will fail; if yes, proceed to step 2.

[0032] Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch.

[0033] Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails.

[0034] Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power supply, and after time t6, send a tripping command to the execution switch corresponding to the power supply to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state, and t5 is the tripping action time of the execution switch corresponding to the power supply to be converted.

[0035] To further improve the accuracy of the estimated closing time of the actuator switch, this invention further corrects the relationship between the closing time and the driving voltage in real time based on historical data of the actual driving voltage and the actual closing time. This ensures that the actuator switch can close at the expected closing phase angle throughout its electrical life, avoiding excessive circulating current. Specifically:

[0036] The control unit also includes a data correction module, used to monitor in real time the actual closing action time and actual driving voltage of each actuator switch for each closing operation, and record normal closing action data where both the actual closing action time and actual driving voltage are within a preset range. Then, based on the recorded normal closing action data, the closing action time-driving voltage correspondence data of each actuator switch is corrected using the following method: starting from when the number of recorded normal closing actions reaches a preset number J, after each normal closing operation, the closing action time corresponding to the actual driving voltage of this normal closing action is found from the current closing action time-driving voltage correspondence data, and updated using the average of the actual closing action times of the most recent M normal closing actions. <M≤J。

[0037] To ensure the stability of the drive voltage for the actuator switches as much as possible, the power supply parallel conversion device further includes a power selection circuit, which is used to select the optimal power supply from the two or more power supplies in real time based on the power supply voltage to supply power to each actuator switch.

[0038] To facilitate public understanding, the technical solution of the present invention will be described in detail below using the simplest dual-power switching system as an example, in conjunction with the accompanying drawings:

[0039] like Figure 1 As shown, the power conversion system of this embodiment includes a first power supply, a second power supply, and a parallel power conversion device. The parallel power conversion device includes: a first power input terminal and a second power input terminal connected to the first and second power supplies respectively; a first output terminal and a second output terminal connected to the load; a first execution switch; a second execution switch; and a control unit. The first execution switch is connected in series between the first power input terminal and the first output terminal, and the second execution switch is connected in series between the second power input terminal and the second output terminal. The first and second output terminals are connected together and then connected to the load. The control unit can control the first and second execution switches respectively. The control unit includes a microprocessor and power supply circuits, voltage detection circuits, frequency detection circuits, power selection circuits, switch state detection circuits, execution switch on / off control circuits, and phase detection circuits connected to the microprocessor respectively. The measurement circuits are used to detect the input voltage, input frequency, and input phase of the first and second power input terminals in real time. The switch state detection circuit is used to detect the switching states of the first and second execution switches in real time. The execution switch on / off control circuit is used to control the switching states of the first and second execution switches. When the control unit receives a parallel conversion command and the input phase sequence, input voltage difference, and input frequency difference between the first and second power input terminals all meet the preset parallel conversion conditions, it calculates the time when the parallel conversion closing command is issued, which ensures that the start time of the parallel state is at the same phase as the inputs of the first and second power input terminals. At the time the parallel conversion closing command is issued, it sends a parallel conversion closing command to the execution switch corresponding to the target power supply. In addition, the power supply circuit in this embodiment obtains electrical energy from the first and / or second power supply and converts it into a suitable voltage for the control unit. The power selection circuit in this embodiment is used to select the optimal power supply from the two power supplies in real time based on the power supply voltage to power each execution switch.

[0040] The voltage detection circuit, frequency detection circuit, switch state detection circuit, switch on / off control circuit, and phase detection circuit in the above-mentioned device are all mature technologies in the field. Those skilled in the art can select specific circuit structures according to actual conditions. In this embodiment, the frequency detection circuit converts the voltage signals of the first power supply and the second power supply into zero-crossing pulse signals and transmits them to the microprocessor. The microprocessor obtains the frequencies of the first power supply and the second power supply based on the zero-crossing pulse signal interval.

[0041] The control unit performs power parallel conversion control according to the following steps:

[0042] Step 1: Confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and whether the voltage difference and frequency difference are within the preset range. If not, the conversion will fail; if yes, proceed to step 2.

[0043] Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch.

[0044] Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails.

[0045] Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power supply, and after time t6, send a opening command to the execution switch corresponding to the power supply to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state, and t5 is the opening action time of the execution switch corresponding to the power supply to be converted.

[0046] like Figure 2 As shown, taking phase B as an example, when the phase difference between the first power supply and the second power supply detected by the control unit in real time is Φ1, the time until the first power supply and the second power supply are in phase is t3. (Δf>0); The closing action time t2 of the actuator switch is obtained from the corresponding data of the closing action time and driving voltage of the actuator switch based on the current actual driving voltage value. The parallel connection time t1 can be preset by the control unit. The control unit can start timing from the zero-crossing point of the second power supply (i.e., time A), when the phase difference Φ0 is calculated. When the timing reaches t3-t2 (i.e., time B), to ensure a small parallel loop current, the control unit compares the real-time detected phase difference Φ1 with the set phase difference threshold Φs. Only when Φ1 < Φs does the control unit issue a parallel closing command for the actuator switch. The parallel connection is achieved at time C. At time C, the first and second power supplies have the same phase at time B, and the loop current is 0. The parallel connection ends at time D. During the parallel connection process, the command to disconnect the actuator switch is issued starting from time B, after t1+t2-t5. To further reduce the closing current value, the parallel time t1 can be reduced. However, t1 must be greater than the time for the switch to open. The smaller the parallel time t1, the smaller the phase difference when the first power supply and the second power supply are disconnected, and the smaller the closing current value.

[0047] Step 5: Correct the corresponding data of closing action time and driving voltage for each actuator based on the recorded normal closing action data:

[0048] The control unit monitors the actual closing action time and actual drive voltage of each actuator switch in real time for each closing operation and records the normal closing action data when both the actual closing action time and actual drive voltage are within the preset range. Then, based on the recorded normal closing action data, the closing action time-drive voltage correspondence data for each actuator switch is corrected using the following method: Starting from when the number of recorded normal closing actions reaches a preset number J, after each normal closing operation, the closing action time corresponding to the actual drive voltage of this normal closing action is found from the current closing action time-drive voltage correspondence data, and updated using the average of the actual closing action times of the most recent M normal closing actions. <M≤J。

[0049] The relationship between the closing action time and driving voltage of the actuator switch can be presented in the form of an array or a curve. The following example, using the simplest array format, will further illustrate the specific correction method:

[0050] (1) The microprocessor contains an array t(i) showing the relationship between the driving voltage and the closing action time of the actuator switch, where i = 0 to n, and the array elements are the closing action times of the actuator switch under different driving voltages. u z1 As the upper limit of the driving voltage, u z2The driving voltage is the lower limit, and Δu is the voltage interval. The relationship between the driving voltage and the closing action time t(i) of the switch is as follows: the driving voltage in the range of Uz1+(m-1)ΔU~Uz1+mΔU corresponds to the closing action time t(m) of the switch, where m∈[0,n].

[0051] (2) The control unit monitors the closing action time t of the actuator switch. The following steps are not performed; when t∈(ttz1,ttz2), step (3) is executed, where ttz1 is the lower limit of the time for executing the switch closing action, and ttz2 is the upper limit of the time for executing the switch closing action;

[0052] (3) When the number of closing actions of the actuator switch driving voltage within each range of Uz1+(m-1)△U~Uz1+m△U is ≤J, the actuator switch closing action time array t(i) remains unchanged (t(i) has a default value); (4) When the number of closing actions of the actuator switch driving voltage within a certain range of Uz1+(m-1)△U~Uz1+m△U is >J, the controller records the driving voltage at the closing time of the actuator switch M times and stores it in the voltage array U(M), and records the closing action time t(M) of the actuator switch at this time. Then, it calculates the average closing action time of the actuator switch and updates the corresponding actuator switch closing action time array element under the driving voltage.

[0053] If the driving voltage U(M) for M times is within the range of Uz1+(m-1)△U~Uz1+m△U, then calculate the average value of the switching closing action time. And use the average value t of the switch closing action time. m Update the array t(m) which shows the relationship between the driving voltage and the time of the switch closing action;

[0054] (5) As the number of times the switch closing action is increased, repeat step (3) to obtain the driving voltage at the time of the new M times the switch closing action is executed and store it in the voltage array U(M), and record the time t(M) of the switch closing action at this time. Then calculate the average value of the switch closing action time and update the corresponding switch closing action time array element under the driving voltage. Repeat this process to continuously update the switch closing action time array t(i).

[0055] When the parallel conversion device is a two-input-one-bus-coupled conversion device, a three-input-one-output conversion device, a three-input-two-bus-coupled conversion device, or a two-input-one-bus-coupled-two-generator conversion device, the parallel conversion principle is the same. The only difference is the number of input power supply paths, the number of voltage detection circuits, the number of closing / opening control circuits, and the number of closing / opening status detection circuits. These will not be elaborated further here.

Claims

1. A conversion control method for a power supply parallel conversion device, wherein the power supply parallel conversion device comprises a set of actuator switches respectively connected to two or more power supplies; characterized in that, The specific steps of the conversion control method are as follows: Step 1: Confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and whether the voltage difference and frequency difference are within the preset range. If not, the conversion will fail; if yes, proceed to step 2. Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch. Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails. Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power source, and after time t6, send a opening command to the execution switch corresponding to the power source to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state and t5 is the opening action time of the switch corresponding to the power supply to be converted.

2. The conversion control method for the power supply parallel conversion device as described in claim 1, characterized in that, Also includes: The actual closing action time and actual driving voltage of each actuator switch are monitored in real time, and normal closing action data where both the actual closing action time and actual driving voltage are within a preset range are recorded. Then, based on the recorded normal closing action data, the closing action time-driving voltage correspondence data of each actuator switch is corrected according to the following method: starting from the number of recorded normal closing actions reaching a preset number J, after each normal closing, the closing action time corresponding to the actual driving voltage of this normal closing action is found from the current closing action time-driving voltage correspondence data, and updated with the average of the actual closing action times of the most recent M normal closing actions. <M≤J。 3. The conversion control method for the power supply parallel conversion device as described in claim 1 or 2, characterized in that, The optimal power supply is selected from the two or more power supplies in real time based on the power supply voltage to power each actuator switch.

4. A power supply parallel conversion device, comprising a set of actuator switches respectively connected to two or more power supplies; characterized in that, The power supply parallel conversion device also includes a control unit for controlling the conversion in the following manner: Step 1: Confirm whether the phase sequence of the power supply to be converted and the target power supply are the same and whether the voltage difference and frequency difference are within the preset range. If not, the conversion will fail; if yes, proceed to step 2. Step 2: Taking the zero-crossing point of the voltage of one of the two power supplies as the starting time of this round of timing, calculate the duration t4 from the starting time of this round of timing to the time when the parallel switching closing command is issued, based on the phase difference ΔΦ between the two power supplies at the starting time of this round of timing. The calculation formula is: t4 = t3 - t2, where t3 is the duration from the starting time of this round of timing to the most recent time when the two power supplies are in phase. Δf is the frequency difference between the two power supplies, and t2 is the closing action time required for the execution switch to complete the closing action from receiving the closing command, obtained from the current driving voltage of the execution switch corresponding to the target power supply and the corresponding data of the closing action time and driving voltage of the execution switch. Step 3: Determine whether the calculated duration t4 is less than the voltage cycle of the two power supplies. If not, proceed to Step 2 after the voltages of the two power supplies cross zero synchronously and start a new round of calculation. If yes, then determine whether the phase difference ΔΦ is less than the preset phase difference threshold. If it is less, proceed to Step 4. Otherwise, the parallel conversion fails. Step 4: At time t4 after the start of this round of timing, send a closing command to the execution switch corresponding to the target power source, and after time t6, send a opening command to the execution switch corresponding to the power source to be converted, thus ending the parallel conversion; t6 = t1 + t2 - t5, where t1 is the preset duration of the parallel state and t5 is the opening action time of the switch corresponding to the power supply to be converted.

5. The power parallel conversion device as described in claim 4, characterized in that, The control unit also includes a data correction module, used to monitor in real time the actual closing action time and actual driving voltage of each actuator switch for each closing operation, and record normal closing action data where both the actual closing action time and actual driving voltage are within a preset range. Then, based on the recorded normal closing action data, the closing action time-driving voltage correspondence data of each actuator switch is corrected using the following method: starting from when the number of recorded normal closing actions reaches a preset number J, after each normal closing operation, the closing action time corresponding to the actual driving voltage of this normal closing action is found from the current closing action time-driving voltage correspondence data, and updated using the average of the actual closing action times of the most recent M normal closing actions. <M≤J。 6. The power supply parallel conversion device as described in claim 4 or 5, characterized in that, It also includes a power selection circuit, which is used to select the optimal power supply from the two or more power supplies in real time based on the power supply voltage to power each actuator switch.

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