High-power bidirectional double-path direct current input automatic switching control method and device

Abstract

The invention discloses a high-power bidirectional double-path direct current input automatic switching control method and device, and relates to the technical field of power supply control, and the device is internally provided with a controller, an inverter circuit, a voltage sampling assembly, a driving circuit and two paths of direct current input branches with the same structure, the two direct-current input branches are arranged between the direct-current input end and the inverter circuit in parallel, each direct-current input branch comprises a slow start assembly, a forward conduction assembly and a reverse conduction assembly, and forward conduction and reverse conduction of the branches can be achieved; according to the technical scheme, when one of the preceding-stage double-path direct-current power supply branches breaks down in use, the other power supply branch can be rapidly switched, continuous work of the high-power power conversion device is guaranteed, the device achieves the slow-start power-on function through the slow-start assembly, and the power supply efficiency is improved. The reverse conduction assembly and the direct current connection assembly between the power supplies are used for achieving the function of restraining the voltage rise of the direct current bus. The device and the control method can effectively improve the working reliability of the direct current input high-power power conversion device.

Description

Technical Field

[0001] The present application relates to the technical field of power supply control, and in particular to a high-power bidirectional dual-path direct current input automatic switching control method and device. Background Art

[0002] In the field of power control technology, inverter power equipment is usually used to convert input DC power into AC power to meet the power demand of AC load. In this process, dual-channel DC input is generally used to improve the power supply reliability of the inverter power supply, that is, when one input currently in use fails, it can be switched to another input without interruption, which can ensure the DC input supply of the inverter power supply and continue to maintain continuous output power supply. At the same time, the use of dual-channel DC input can also realize energy dispatching of different DC sources, and a branch can be purposefully selected as the main power supply branch according to the energy dispatching needs of the power grid system.

[0003] The existing technology or products rely on uncontrolled devices such as diodes to achieve DC input switching of inverter power supplies, which has the following shortcomings: (1) The switching judgment condition is single, and only the input branch with a high voltage value can be selected. When the voltage of the main branch is slightly lower but still within the normal voltage range, it is impossible to give priority to the main branch; (2) There is no voltage difference protection judgment during switching. When there is a large difference between the voltage of the branch to be switched in and the DC bus capacitor inside the power supply, direct switching will cause a large instantaneous current to charge the bus capacitor, which may cause the input voltage and output voltage of the inverter power supply to fluctuate, and even cause the voltage front-stage DC input side protection switch to operate; (3) There is no reverse channel during switching. Due to multiple machines in parallel, grid-connected operation, motor pumping, etc., the inverter power supply may have reverse input power on the AC side, causing DC bus overvoltage. If there are no energy consumption or discharge measures, it may cause DC overvoltage protection shutdown. Summary of the invention

[0004] The purpose of the present application is to provide an automatic switching control method and device which adopts a dual-path input structure and can realize bidirectional power flow in each path and uninterrupted switching of dual-path DC input in order to solve the problems in the prior art of single switching judgment condition, no voltage difference protection in switching and no discharge measures in the process of power conversion of dual-path DC input inverter power supply.

[0005] The technical solution of the present application is to provide a high-power bidirectional dual-channel DC input automatic switching control method, which is used for multiple inverter power supplies arranged in parallel, adjacent inverter power supplies are connected by a DC bus switch, a single inverter power supply is internally provided with a controller, an inverter circuit, a voltage sampling component, a drive circuit and two DC input branches with the same structure, the two DC input branches are arranged in parallel and the output ends of the two DC input branches are respectively connected to the inverter circuit through a DC bus, characterized in that the method comprises: step 1, using the two DC input branches as the main branch and the standby branch respectively, closing the DC switch between the DC power supply and the inverter power input end; step 2, using the slow-start components in the two DC input branches to limit the DC input current to a preset safety value, and after the voltage of the DC bus reaches a predetermined range, controlling the fast forward conduction positive component and the fast forward conduction negative component in the main branch to conduct through the controller, so that the main branch is forward-conducted, so that the DC power supply supplies power to the inverter circuit through the main branch; step 3, using the controller to monitor the voltage of the main branch input end, the bus voltage, the DC ... The voltage and the state of the DC switch, when the monitoring result meets the preset conditions, the DC input branch is switched, and when the monitoring result does not meet the preset conditions, the main branch continues to be used for power supply, wherein the preset conditions are: the bus voltage is lower than the first threshold value or the DC input voltage is lower than the second threshold value or the DC switch is opened; step 4, judging whether to reverse conduct the DC input branch according to the bus voltage, when the bus voltage does not exceed the preset overvoltage limit, continue to forward conduct the current DC input branch, when the bus voltage exceeds the overvoltage limit, control the fast reverse conduction positive component and the fast reverse conduction negative component in the current DC input branch to conduct through the controller, so that the current DC input branch is reversely conducted, and the active current is fed back to the DC input terminal of the current inverter power supply, and step 4 is executed; step 5, continue to monitor the bus voltage, when the bus voltage is less than the predetermined voltage threshold in the reverse conduction state, forward conduct the current DC input branch again, when the bus voltage is still greater than or equal to the predetermined voltage threshold in the reverse conduction state, turn on the DC bus tie switch, and feed the active current back to the DC input terminals of all parallel inverter power supplies.

[0006] Furthermore, step 2 specifically includes: after the DC switch is turned on, the DC input current reaches the DC bus through the slow-start components in the two DC input branches, the voltage of the DC bus gradually increases, and the slow-start components limit the DC input current to a preset safety value through internal resistance. The controller monitors the voltage of the DC bus in real time through the voltage sampling component. After the voltage of the DC bus reaches a predetermined range, the controller controls the fast forward conducting positive component and the fast forward conducting negative component in the main branch to conduct through the drive circuit. The DC power supply supplies power to the inverter circuit through the main branch, and the inverter circuit converts the DC input current into AC current and outputs the AC current.

[0007] Furthermore, step 3 specifically includes: setting voltage sampling components between the positive and negative poles of the DC input branch input terminal and between the positive and negative poles of the DC bus, respectively, the controller monitors the main branch input terminal voltage and the bus DC line voltage in real time through the voltage sampling component, the controller is connected to the DC switch, and the controller monitors the state of the DC switch in real time. When at least one of the bus voltage is lower than the first threshold, the DC input voltage is lower than the second threshold, or the DC switch is opened, it is determined that the DC input of the current inverter power supply is in an abnormal state. The controller quickly turns on the fast forward conducting positive electrode component and the fast forward conducting negative electrode component in the spare branch through the driving circuit, and uses the spare branch to power the inverter circuit. When all conditions are not met, it is determined that the DC input of the current inverter power supply is in a normal working state, and the main branch continues to be used to power the inverter circuit.

[0008] Furthermore, step 4 specifically includes: presetting an overvoltage limit so that the overvoltage limit is less than the maximum operating voltage of all devices inside the inverter power supply, the controller monitors the bus DC line voltage in real time through a voltage sampling component, and when the bus voltage does not exceed the preset overvoltage limit, it is determined that the bus voltage does not have an abnormal increase, and the current DC input branch continues to be forward-conducted; when the bus voltage exceeds the overvoltage limit, it is determined that the bus voltage has an abnormal increase, and the controller turns on the fast reverse conducting positive component and the fast reverse conducting negative component in the current DC input branch through a drive circuit, and at the same time turns off the fast forward conducting positive component and the fast forward conducting negative component, and feeds back the active current at the DC bus to the DC input terminal of the current inverter power supply, so that the DC bus voltage drops to a range less than or equal to the overvoltage limit.

[0009] Furthermore, step 5 specifically includes: the controller continues to monitor the bus DC line voltage in real time through the sampling component. When the bus voltage in the reverse conduction state is less than a predetermined voltage threshold, the controller turns on the fast forward conduction positive component and the fast forward conduction negative component in the current DC input branch through the driving circuit, and at the same time turns off the fast reverse conduction positive component and the fast reverse conduction negative component. When the bus voltage in the reverse conduction state is still greater than or equal to the predetermined voltage threshold, the controller turns on the DC bus tie switch to feed back the active current to the DC input terminals of all parallel inverter power supplies, so that the DC bus voltage drops to a range not exceeding the overvoltage limit.

[0010] The technical solution of the present application also provides a high-power bidirectional dual-channel DC input automatic switching device, which includes: an inverter circuit and two DC input branches with the same structure; the input ends of the two DC input branches are respectively connected to the DC power supply through DC switches, the output ends of the two DC input branches are respectively connected to the inverter circuit through DC buses, and the DC power supply supplies power to the inverter circuit through any one of the DC input branches; the DC input branch includes a slow-start component, a fast forward conducting positive electrode component, a fast reverse conducting positive electrode component, a fast forward conducting negative electrode component and a fast reverse conducting negative electrode component, wherein the slow-start component, the fast forward conducting positive electrode component and the fast reverse conducting positive electrode component are arranged in parallel between the positive electrode of the input end of the DC input branch and the positive electrode of the DC bus, The fast forward conducting negative electrode component and the fast reverse conducting negative electrode component are arranged in parallel between the negative electrode of the input end of the DC input branch and the negative electrode of the DC bus; the slow-start component is used to limit the DC input current to a safe value when the main power is first turned on until the DC bus voltage reaches a preset DC input voltage; the fast forward conducting positive electrode component and the fast forward conducting negative electrode component are used to forward conduct the DC input branch under the triggering of the drive circuit, so that the DC power supply supplies power to the inverter circuit; the fast reverse conducting positive electrode component and the fast reverse conducting negative electrode component are used to reverse conduct the DC input branch under the triggering of the drive circuit, so that the inverter circuit feeds back the active current to the input end of the DC input branch; the inverter circuit is used to convert the input DC power into AC power for output.

[0011] Furthermore, the input end of the slow-start component is connected to the positive input end of the DC input branch, and the output end of the slow-start component is connected to the positive DC bus; the slow-start component is composed of a diode and a resistor in series, wherein the resistor is used to slow down the rate of current rise, and the diode is used to limit the current to forward conduction.

[0012] Furthermore, the input end of the fast forward conduction positive electrode component is connected to the positive electrode of the input end of the DC input branch, and the output end of the fast forward conduction positive electrode component is connected to the positive electrode of the DC bus; the fast forward conduction positive electrode component is composed of a thyristor rectifier, a capacitor, a resistor and a diode, the resistor and the diode are connected in parallel and the whole formed in parallel is connected in series with the capacitor, the whole formed by the capacitor, the resistor and the diode is connected in parallel with the thyristor rectifier, the thyristor rectifier is used to control the on and off of the fast forward conduction positive electrode component according to the trigger signal sent by the drive circuit, the capacitor is used to smooth the voltage change of the fast forward conduction positive electrode component through the charging and discharging process, and the resistor is used to prevent Excessive current may cause damage to components, and the diode is used to prevent current from flowing in the reverse direction in the fast forward conducting positive electrode component, wherein the direction of the anode of the thyristor rectifier is the input end of the fast forward conducting positive electrode component, and the direction of the cathode of the thyristor rectifier is the output end of the fast forward conducting positive electrode component; the input end of the fast reverse conducting positive electrode component is connected to the positive pole of the DC bus, and the output end of the fast reverse conducting positive electrode component is connected to the positive pole of the input end of the DC input branch; the composition structure of the fast reverse conducting positive electrode component is the same as that of the fast forward conducting positive electrode component, and the conduction direction of the fast reverse conducting positive electrode component is opposite to that of the fast forward conducting positive electrode component.

[0013] Furthermore, the input end of the fast forward conducting negative electrode assembly is connected to the negative electrode of the input end of the DC input branch, the output end of the fast forward conducting negative electrode assembly is connected to the negative electrode of the DC bus, the composition structure of the fast forward conducting negative electrode assembly is the same as that of the fast forward conducting positive electrode assembly, and the conduction direction of the fast forward conducting negative electrode assembly is the same as that of the fast forward conducting positive electrode assembly; the input end of the fast reverse conducting negative electrode assembly is connected to the positive electrode of the DC bus, the output end of the fast reverse conducting negative electrode assembly is connected to the positive electrode of the input end of the DC input branch, the composition structure of the fast reverse conducting negative electrode assembly is the same as that of the fast forward conducting positive electrode assembly, and the fast reverse conducting negative electrode assembly is opposite to the fast forward conducting positive electrode assembly.

[0014] Furthermore, the automatic switching device also includes: a voltage sampling component, a drive circuit and a controller; the voltage sampling component measures the voltage at the input end of the DC input branch and the DC bus; the drive circuit is used to control the on and off of the fast forward conducting positive component, the fast reverse conducting positive component, the fast forward conducting negative component and the fast reverse conducting negative component through a trigger signal; the controller is used to control the drive circuit to send a trigger signal to each component according to the voltage value of the DC input branch input end and the DC bus.

[0015] The beneficial effects of this application are:

[0016] First, the technical solution in the present application sets two DC input branches with the same structural composition in the inverter power supply, and uses controllable electronic switching devices to build a fast forward conduction component in the DC input branch. The forward conduction component can realize controllable fast switching of the two DC input branches, and can ensure that the input branch is reasonably selected according to the needs of energy scheduling, priority of specific branches, etc. during the power supply process; the technical solution in the present application can detect the abnormality of the DC input according to multiple conditions such as the DC input voltage, the DC bus voltage and the state of the DC input switch, and quickly switch the branch to reduce the DC bus voltage drop and increase the stability of the power supply. Compared with the mode of switching according to a single condition of voltage size in the prior art, the technical solution in the present application will switch to the backup branch only when an abnormal problem of DC input occurs in the main branch, avoiding the frequent switching problem caused by the imbalance of voltage size of each branch in the circuit, and improving the stability of the inverter power supply.

[0017] Second, the technical solution in the present application introduces a voltage difference protection judgment in the process of switching branches. The controller monitors the DC input voltage, DC bus voltage and the status of the DC input switch in real time. According to the changes in these data, the timing of switching branches can be selected quickly and reasonably, which can effectively reduce the instantaneous charging current caused by switching when the voltage difference is large, and ensure the smooth operation of the inverter power supply switching process.

[0018] Third, the technical solution in the present application also uses controllable electronic switching devices to build a fast reverse discharge component in the DC input branch. The reverse discharge component can perform energy feedback when reverse power occurs on the AC side of the inverter, effectively suppressing the DC bus voltage overvoltage and ensuring the stable operation of the inverter under reverse power conditions. The fast reverse discharge component can solve the problem of abnormal increase in DC bus voltage when the inverter is connected in parallel with multiple machines, directly in parallel with the shore power grid, or with back-electromotive force loads. Compared with the switching mode without reverse channel in the prior art, the discharge measures of the technical solution in the present application can avoid the protection shutdown problem caused by DC overvoltage.

[0019] Fourthly, the technical solution in the present application further provides a DC bus tie switch on the input DC bus of multiple inverter power supplies, which can effectively suppress overvoltage of the DC bus voltage by feeding back active current to the DC input terminals of all parallel inverter power supplies. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The advantages of the above and / or additional aspects of the present application will become apparent and easily understood in the description of the embodiments in conjunction with the following drawings, in which:

[0021] Figure 1 is a functional schematic diagram of a high-power bidirectional dual-path DC input automatic switching device according to an embodiment of the present application;

[0022] Figure 2 It is a circuit diagram of an embodiment of a high-power bidirectional dual-path DC input automatic switching device according to an embodiment of the present application. DETAILED DESCRIPTION

[0023] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0024] In the following description, many specific details are elaborated to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited to the specific embodiments disclosed below.

[0025] like Figure 1 to Figure 2 As shown, this embodiment provides a high-power bidirectional dual-channel DC input automatic switching device, which is an inverter power supply with power-on slow start, voltage difference protection, and reverse current conduction functions. The device includes: a first DC input branch, a second DC input branch, a voltage sampling component, a drive circuit, a controller and an inverter circuit.

[0026] In this embodiment, the first DC input branch and the second DC input branch are two DC input branches with the same structure. The DC input branch includes a slow-start component, a fast forward conducting positive electrode component, a fast reverse conducting positive electrode component, a fast forward conducting negative electrode component and a fast reverse conducting negative electrode component. The first DC input branch and the second DC input branch are respectively introduced in detail below.

[0027] The input end of the first DC input branch is connected to the external DC power supply through a DC switch, and the output end is connected to the inverter circuit through a DC bus; specifically, a first DC input positive pole V1P and a first DC input negative pole V1N are set on the side of the first DC input branch connected to the DC power supply, the first DC input positive pole V1P is used to connect to the positive pole of the external DC power supply through the DC switch, and the first DC input negative pole V1N is used to connect to the negative pole of the external DC power supply through the DC switch, the positive and negative poles of the side of the first DC input branch connected to the inverter circuit are respectively connected to the DC bus positive pole VbusP and the DC bus negative pole VbusN, and the DC bus positive pole VbusP and the DC bus negative pole VbusN are respectively connected to the inverter circuit.

[0028] The first DC input branch includes a first slow-start component P10, a first fast forward conducting positive component P11, a first fast reverse conducting positive component P12, a first fast forward conducting negative component N11 and a first fast reverse conducting negative component N12; wherein, the first slow-start component P10, the first fast forward conducting positive component P11 and the first fast reverse conducting positive component P12 are arranged in parallel between the first DC input positive pole V1P and the DC bus positive pole VbusP, and the first fast forward conducting negative component N11 and the first fast reverse conducting negative component N12 are arranged in parallel between the first DC input negative pole V1N and the DC bus negative pole VbusN.

[0029] The first slow-start component P10 is used to limit the DC input current to a safe value when the main power is first turned on until the DC bus voltage reaches the preset DC input voltage. The input end of the first slow-start component P10 is connected to the first DC input positive electrode V1P, and the output end is connected to the DC bus positive electrode VbusP; the first slow-start component P10 is composed of a diode D10 and a resistor R10 connected in series, the resistor R10 is used to slow down the rate of current rise, and D10 is used to limit the current to conduct forward.

[0030] Specifically, Figure 2 As shown, when the DC input voltage is applied to the first slow-start component P10, the resistor R10 limits the increase of instantaneous current to prevent excessive current from impacting the circuit. After the resistor limits the current, the voltage of the DC bus will gradually rise and gradually approach the preset DC input voltage. This process effectively realizes the slow-start and avoids the instantaneous large current caused by directly applying high voltage. D10 ensures that the current is only conducted in the forward direction to prevent the influence of reverse current and further protect the circuit.

[0031] In this embodiment, a slow-start component is used to control the rising speed of the voltage and current in the DC bus to avoid current surges or voltage mutations in the circuit at the moment of power-on, achieve smooth startup of the power input, and avoid damage to sensitive components in the circuit.

[0032] The first fast forward conduction positive electrode component P11 is used to conduct forward conduction (forward conduction refers to the conduction state when the DC power supply supplies power to the inverter circuit) under the triggering of the driving circuit, so that the DC power supply supplies power to the inverter circuit. The input end of the first fast forward conduction positive electrode component P11 is connected to the first DC input positive electrode V1P, and the output end is connected to the DC bus positive electrode VbusP; the first fast forward conduction positive electrode component P11 consists of a silicon controlled rectifier SCR11 (Silicon ControlledRectifier, a semiconductor device with three terminals, which needs a trigger signal to be applied to the control electrode G for conduction), a capacitor C11, a resistor R11 and a diode D11, the resistor R11 and the diode D11 are connected in parallel and the whole composed of the resistor R11 and the diode D11 is connected in series with the capacitor C11, the whole composed of the capacitor C11, the resistor R11 and the diode D11 is connected in parallel with the thyristor rectifier SCR11, the thyristor rectifier SCR11 is used to control the on and off of the first fast forward conducting positive electrode component P11 according to the trigger signal sent by the drive circuit, the capacitor C11 is used to smooth the voltage change of the first fast forward conducting positive electrode component P11 through the charging and discharging process to prevent instantaneous current impact, the resistor R11 is used to limit the size of the passing current to prevent excessive current from causing damage to other components, and the diode D11 is used to prevent the current from flowing in the first fast forward conducting positive electrode component P11 in reverse. The direction of the anode of the silicon controlled rectifier SCR11 is the input end of the first fast forward conducting positive electrode component P11, and the direction of the cathode of the silicon controlled rectifier SCR11 is the output end of the first fast forward conducting positive electrode component P11. The conduction direction of the silicon controlled rectifier SCR11 is from the positive electrode of the DC input branch to the positive electrode of the DC bus, and its control electrode G is connected to the drive circuit, and the conduction direction of the diode D11 is from the positive electrode of the DC input branch to the positive electrode of the DC bus.

[0033] Specifically, Figure 2 As shown, when the driving circuit does not send a trigger signal, SCR11 is in the off state, and no current flows through the branch where it is located. Capacitor C11 enters the charging state to limit the current passing through capacitor C11. R11 prevents the capacitor from charging too quickly or too much current from flowing when SCR11 is not turned on. After the driving circuit sends a trigger signal to the control electrode G of SCR11, SCR11 is turned on, and current flows through the branch where it is located. Capacitor C11 discharges quickly when SCR11 is triggered and provides instantaneous energy to SCR11, helping the circuit to quickly establish current at the moment of turn-on. After the capacitor C11 is discharged, it enters the charging state again. During the whole process, D11 blocks the reverse current to ensure that the current flows in the expected direction when SCR11 is triggered.

[0034] The first fast reverse conducting positive electrode component P12 is used to reverse conduct when triggered by the drive circuit (reverse conduction refers to the conduction state in which the inverter circuit feeds back the active current to the DC input terminal of the current inverter power supply), so that the inverter circuit feeds back the active current to the input terminal of the DC input branch. The input end of the first fast reverse conducting positive electrode component P12 is connected to the DC bus positive electrode VbusP, and the output end is connected to the first DC input positive electrode V1P; the first fast reverse conducting positive electrode component P12 is composed of a thyristor rectifier SCR12, a capacitor C12, a resistor R12 and a diode D12. The structure and working principle of the first fast reverse conducting positive electrode component P12 are the same as those of the first fast forward conducting positive electrode component P11. The conduction direction of the first fast reverse conducting positive electrode component P12 is opposite to that of the first fast forward conducting positive electrode component P11. The conduction direction of the thyristor rectifier SCR12 is from the DC bus positive electrode to the DC input branch positive electrode, and its control electrode G is connected to the drive circuit. The conduction direction of the diode D12 is from the DC bus positive electrode to the DC input branch positive electrode, which will not be repeated here.

[0035] The first fast forward conducting negative electrode component N11 is used to conduct forward conduction under the triggering of the driving circuit, so that the DC power supply supplies power to the inverter circuit. The input end of the first fast forward conducting negative electrode component N11 is connected to the first DC input negative electrode V1N, and the output end is connected to the DC bus negative electrode VbusN; the first fast forward conducting negative electrode component N11 is composed of a thyristor rectifier SCR13, a capacitor C13, a resistor R13 and a diode D13, the resistor R13 and the diode D13 are connected in parallel, and the whole composed of the resistor R13 and the diode D13 is connected in series with the capacitor C13, and the whole composed of the capacitor C13, the resistor R13 and the diode D13 is connected to the thyristor. The rectifier SCR13 is connected in parallel, and the thyristor rectifier SCR13 is used to control the on and off of the first fast forward conducting negative electrode component N11 according to the trigger signal sent by the drive circuit. The capacitor C13 is used to smooth the voltage change of the first fast forward conducting negative electrode component N11 through the charging and discharging process to prevent the instantaneous impact of the current. The resistor R13 is used to limit the magnitude of the passing current to prevent excessive current from passing through and causing damage to other components. The diode D13 is used to prevent the current from flowing in the first fast forward conducting positive electrode component P11 in reverse. The structure and working principle of the first fast forward conducting negative electrode component N11 are the same as those of the first fast forward conducting positive electrode component P11, wherein the conduction direction of the thyristor rectifier SCR13 is from the negative electrode of the DC input branch to the negative electrode of the DC bus, and its control electrode G is connected to the drive circuit. The conduction direction of the diode D13 is from the negative electrode of the DC input branch to the negative electrode of the DC bus, which will not be repeated here.

[0036] The first fast reverse conducting negative electrode component N12 is used to reverse conduct under the triggering of the driving circuit, so that the inverter circuit feeds back the active current to the input end of the DC input branch. The input end of the first fast reverse conducting negative electrode component N12 is connected to the negative electrode VbusN of the DC bus, and the output end is connected to the first DC input negative electrode V1N; the first fast reverse conducting negative electrode component N12 is composed of a thyristor rectifier SCR14, a capacitor C14, a resistor R14 and a diode D14. The structure and working principle of the first fast reverse conducting negative electrode component N12 are the same as those of the first fast forward conducting negative electrode component N11. The conduction direction of the first fast reverse conducting negative electrode component N12 is opposite to that of the first fast forward conducting negative electrode component N11, wherein the conduction direction of the thyristor rectifier SCR14 is from the negative electrode of the DC bus to the negative electrode of the DC input branch, and its control electrode G is connected to the driving circuit, and the conduction direction of the diode D14 is from the negative electrode of the DC bus to the negative electrode of the DC input branch, which will not be repeated here.

[0037] One side of the second DC input branch is connected to the external DC power supply through a DC switch, and the other side is connected to the inverter circuit through a DC bus; specifically, a second DC input positive pole V2P and a second DC input negative pole V2N are set on the side of the second DC input branch connected to the DC power supply, the second DC input positive pole V2P is used to connect to the positive pole of the external DC power supply through the DC switch, and the second DC input negative pole V2N is used to connect to the negative pole of the external DC power supply through the DC switch, the positive and negative poles of the second DC input branch on the side connected to the inverter circuit are respectively connected to the DC bus positive pole VbusP and the DC bus negative pole VbusN, and the DC bus positive pole VbusP and the DC bus negative pole VbusN are respectively connected to the inverter circuit.

[0038] The first DC input branch and the second DC input branch are arranged in parallel in the inverter power supply. When in use, one of them is selected to be turned on for power transmission. When one of the branches fails, it can be instantly switched to the other branch. For example, when the first DC input branch is turned on, the first DC input positive electrode V1P and the first DC input negative electrode V1N are connected to the DC power supply through the DC switch, and the current of the DC power supply is used to supply the inverter current through the first DC input branch.

[0039] The second DC input branch includes a second slow-start component P20, a second fast forward conducting positive component P21, a second fast reverse conducting positive component P22, a second fast forward conducting negative component N21 and a second fast reverse conducting negative component N22; wherein, the second slow-start component P20, the second fast forward conducting positive component P21 and the second fast reverse conducting positive component P22 are arranged in parallel between the second DC input positive pole V2P and the DC bus positive pole VbusP, and the second fast forward conducting negative component N21 and the second fast reverse conducting negative component N22 are arranged in parallel between the second DC input negative pole V2N and the DC bus negative pole VbusN.

[0040] The input end of the second slow-start component P20 is connected to the second DC input positive electrode V2P, and the output end is connected to the DC bus positive electrode VbusP; the second slow-start component P20 is composed of a diode D20 and a resistor R20 connected in series.

[0041] The input end of the second fast forward conducting positive electrode component P21 is connected to the second DC input positive electrode V2P, and the output end is connected to the DC bus positive electrode VbusP; the second fast forward conducting positive electrode component P21 is composed of a thyristor rectifier SCR21, a capacitor C21, a resistor R21 and a diode D21, and the connection method of the various components inside the second fast forward conducting positive electrode component P21 is the same as the connection method of the various components inside the first fast forward conducting positive electrode component P11.

[0042] The input end of the second fast reverse conducting positive electrode component P22 is connected to the DC bus positive electrode VbusP, and the output end is connected to the second DC input positive electrode V2P; the second fast reverse conducting positive electrode component P22 is composed of a thyristor rectifier SCR22, a capacitor C22, a resistor R22 and a diode D22, and the connection mode of each component inside the second fast reverse conducting positive electrode component P22 is the same as the connection mode of each component inside the first fast reverse conducting positive electrode component P12. Among them, the conduction direction of the second fast forward conducting positive electrode component P21 is opposite to that of the second fast reverse conducting positive electrode component P22.

[0043] The input end of the second fast forward conducting negative electrode component N21 is connected to the second DC input negative electrode V2N, and the output end is connected to the DC bus negative electrode VbusN; the second fast forward conducting negative electrode component N21 is composed of a thyristor rectifier SCR23, a capacitor C23, a resistor R23 and a diode D23, and the connection method of the various components inside the second fast forward conducting negative electrode component N21 is the same as the connection method of the various components inside the first fast forward conducting negative electrode component N11.

[0044] The input end of the second fast reverse conducting negative electrode component N22 is connected to the negative electrode VbusN of the DC bus, and the output end is connected to the second DC input negative electrode V2N; the second fast reverse conducting negative electrode component N22 is composed of a thyristor rectifier SCR24, a capacitor C24, a resistor R24 ​​and a diode D24, and the connection mode of each component inside the second fast reverse conducting negative electrode component N22 is the same as the connection mode of each component inside the first fast reverse conducting negative electrode component N12. Among them, the conduction direction of the second fast forward conducting negative electrode component N21 is opposite to that of the second fast reverse conducting negative electrode component N22.

[0045] The connection mode and working principle of each component structure in the second DC input branch are the same as those of the first DC input branch, and will not be described in detail here.

[0046] The voltage sampling component is used to measure the voltage in the branch, including a first voltage sampling V1, a second voltage sampling V2 and a bus voltage sampling V3. The first voltage sampling V1 is arranged between the first DC input positive pole V1P and the first DC input negative pole V1N, the second voltage sampling V2 is arranged between the second DC input positive pole V2P and the second DC input negative pole V2N, and the bus voltage sampling V3 is arranged between the DC bus positive pole VbusP and the DC bus negative pole VbusN.

[0047] The driving circuit is respectively connected to the terminals for receiving trigger signals of the first fast forward conducting positive electrode component P11, the first fast reverse conducting positive electrode component P12, the first fast forward conducting negative electrode component N11, the first fast reverse conducting negative electrode component N12, the second fast forward conducting positive electrode component P21, the second fast reverse conducting positive electrode component P22, the second fast forward conducting negative electrode component N21, and the second fast reverse conducting negative electrode component N22, and is used to control the on and off of each component by sending a trigger signal. Specifically, the driving circuit is connected to the control electrode G of the thyristor rectifier (that is, the terminal for receiving the trigger signal).

[0048] The controller is respectively connected to the first voltage sampling V1, the second voltage sampling V2, the bus voltage sampling V3 and the driving circuit, and is used to obtain the voltage value of each sampling position, and control the driving circuit to send a trigger signal to each component according to the voltage value of each sampling position.

[0049] The inverter circuit is arranged inside the inverter power supply and is used to convert the input direct current into alternating current for output.

[0050] The high-power bidirectional dual-channel DC input automatic switching device also includes a bus tie switch SD0, which is arranged between two adjacent power supplies and is used to connect different DC power supplies to achieve load distribution between different power supplies and improve the reliability and flexibility of the power supply system.

[0051] Specifically, the positive and negative electrodes of adjacent DC power supplies are connected via bus tie switches SD0; Figure 1 As shown, the inverter power supply A and the inverter power supply B are connected in parallel, the DC power supply VDC1 supplies power to the inverter power supply A, and the DC power supply VDC2 supplies power to the inverter power supply B. A bus tie switch SD0 is set between the DC power supply VDC1 and the DC power supply VDC2, and the positive electrode of the DC power supply VDC1 is connected to the positive electrode of the DC power supply VDC2 through the bus tie switch SD0, and the negative electrode of the DC power supply VDC1 is connected to the negative electrode of the DC power supply VDC2 through the bus tie switch SD0.

[0052] The present embodiment provides a high-power bidirectional dual-channel DC input automatic switching control method, which is used for multiple inverter power supplies arranged in parallel, where adjacent inverter power supplies are connected via a DC bus tie switch SD0, and a single inverter power supply is internally provided with two DC input branches with the same structure, as well as a voltage sampling component, a drive circuit, a controller, and an inverter circuit, the two DC input branches are arranged in parallel, and the output ends of the two DC input branches are respectively connected to the inverter circuit via a DC bus, and the control method comprises the following steps:

[0053] Step 1: Use the two DC input branches in the inverter power supply as the main branch and the standby branch respectively, close the DC switch SD1 between the external DC power supply VDC1 and the inverter power supply input terminal, and the DC power supply VDC1 starts to supply power to the inverter power supply.

[0054] Select any DC input branch in the current inverter power supply as the main branch, close the DC switch SD1 between the DC power supply VDC1 and the DC of the main branch, connect the positive and negative poles of the main branch input end to the positive and negative poles of the DC power supply respectively, so that the DC power supply VDC1 supplies power to the main branch; specifically, Figure 1 As shown, the inverter power supply includes a first DC input branch and a second DC input branch. When the first DC input branch serves as the main branch, the first DC input positive pole V1P and the first DC input negative pole V1N are connected to the positive pole and the negative pole of the DC power supply VDC1 respectively. When the second DC input branch serves as the main branch, the second DC input positive pole V2P and the second DC input negative pole V2N are connected to the positive pole and the negative pole of the DC power supply VDC1 respectively.

[0055] In this embodiment, before the DC power supply is connected, one of the two DC input branches with the same structure can be selected as the main branch, and the other can be used as a backup branch to be switched. When a problem occurs in the main branch, the controller can instantly switch to the backup branch to continue to supply power to the inverter circuit in the inverter power supply.

[0056] Step 2, use the slow-start components in the two DC input branches to limit the DC input current to a preset safety value. After the voltage of the DC bus reaches a predetermined range, the controller controls the fast forward conducting positive component and the fast forward conducting negative component in the main branch to conduct, so that the positive main branch is conducted, and the DC power supply VDC1 supplies power to the inverter circuit through the main branch.

[0057] After turning on the DC switch SD1 between the DC power supply and the inverter power input terminal, the DC current output by the DC power supply VDC1 is passed into the inverter power supply, and the DC input current reaches the DC bus through the slow-start components in the two DC input branches. The voltage of the DC bus gradually increases under the action of the DC input current. In this process, the slow-start component limits the DC input current to a preset safety value through an internally set resistor. The controller monitors the voltage between the positive and negative poles of the DC bus in real time through the voltage sampling component. After the voltage of the DC bus reaches a predetermined range, the controller controls the drive circuit to send a trigger signal to the fast forward conduction positive component and the fast forward conduction negative component in the conduction main branch, so that the fast forward conduction positive component and the fast forward conduction negative component in the main branch are turned on, so that the entire main branch is forward-conducted, and the DC power supply VDC1 supplies power to the inverter circuit through the main branch. The inverter circuit converts the DC input current into AC current and outputs the AC current.

[0058] Specifically, Figure 1 As shown, after the DC switch is turned on, the first slow-start component P10 and the second slow-start component P20 are used to perform DC slow-start. When the first DC input branch serves as the main branch, after slow-start, the controller controls the first fast forward conducting positive component P11 and the first fast forward conducting negative component N11 to be turned on through the driving circuit, and the DC power supply VDC1 supplies power to the inverter circuit through the first DC input branch.

[0059] In this embodiment, before the inverter power supply is ready to start, the internal DC bus voltage is close to 0. After the inverter power supply is ready to start, the voltage of the DC bus will start to rise from zero. Instantaneous fluctuations will occur in the process, and the fluctuations may cause instantaneous large currents. The DC input current can be limited to a safe range through the slow-start component, and will not cause damage to the entire circuit. After the voltage of the DC bus reaches a predetermined range (that is, it remains near the steady-state value), the inverter circuit is powered again. When the voltage of the DC bus does not rise to the predetermined DC input voltage, the fast forward conducting positive component, the fast reverse conducting positive component, the fast forward conducting negative component and the fast reverse conducting negative component in the two DC input branches are all in the off state.

[0060] Step 3, using the controller to monitor the main branch input terminal voltage, bus voltage and the status of the DC switch SD1 in real time. When the monitoring result meets the preset conditions, switch the DC input branch. When the monitoring result does not meet the preset conditions, continue to use the main branch for power supply, where the preset conditions are: the bus voltage is lower than the first threshold or the DC input voltage (i.e., the voltage value at the input terminal of the DC input branch) is lower than the second threshold or the DC switch is open.

[0061] Voltage sampling components are arranged between the positive and negative poles of the DC input branch input terminal and between the positive and negative poles of the DC bus. The controller monitors the main branch input terminal voltage and the bus DC line voltage in real time through the voltage sampling component. At the same time, the controller is also connected to the DC switch SD1 and can monitor the state of the DC switch SD1 in real time. When at least one of the following conditions is met: the bus voltage is lower than a preset first threshold, the DC input voltage is lower than a preset second threshold, or the DC switch is opened, it is determined that the DC input of the current inverter power supply is in an abnormal state and it is necessary to switch the DC input branch. Specifically, the controller quickly turns on the fast forward conducting positive electrode component and the fast forward conducting negative electrode component in another DC input branch through a driving circuit, and uses another DC input branch to power the inverter circuit. The switching process can ensure that the AC voltage output by the inverter power supply remains unchanged. When all the conditions are not met: the bus voltage is lower than the preset first threshold, the DC input voltage is lower than the preset second threshold, or the DC switch is opened, it is determined that the DC input of the current inverter power supply is in a normal working state, it is not necessary to switch the DC input branch, and the main branch continues to be used to power the inverter circuit.

[0062] In this embodiment, during the normal operation of the inverter power supply, its internal controller will quickly determine whether the DC input is abnormal in combination with multiple conditions. If any of the following conditions is true, the DC input is determined to be abnormal: 1) the DC bus voltage is lower than the first threshold (the first threshold is the preset normal bus voltage value); 2) the DC input voltage is lower than the first threshold (the first threshold is the preset normal voltage value of the DC input branch input end); 3) the DC input switch SD1 is abnormally opened (i.e., the power supply is cut off). In this embodiment, the use of the above multiple conditions can speed up the detection speed, reduce the judgment and branch switching time, and perform branch switching before the DC bus voltage drops, thereby avoiding the problem of unstable power supply caused by the bus voltage drop, thereby reducing the DC current caused by the voltage difference during the switching process (the DC current caused by the voltage difference will cause current fluctuations in the inverter power supply circuit, affecting the normal operation of the components in the circuit, and will also increase the power loss, affecting the working stability of the inverter power supply), and increase the power supply stability of the inverter power supply.

[0063] Step 4, judging whether to conduct the DC input branch in reverse according to the magnitude of the bus voltage, when the bus voltage does not exceed the preset overvoltage limit, continuing to conduct the current DC input branch in forward direction, when the bus voltage exceeds the overvoltage limit, controlling the fast reverse conduction positive electrode component and the fast reverse conduction negative electrode component in the current DC input branch to conduct through the controller, so that the current DC input branch is reversely conducted, and the active current is fed back to the DC input terminal of the current inverter power supply, and executing step 4;

[0064] An overvoltage limit is preset so that the overvoltage limit is less than the maximum operating voltage of all devices inside the inverter power supply. The controller monitors the bus DC line voltage in real time through a voltage sampling component. When the bus voltage does not exceed the preset overvoltage limit, it is determined that the bus voltage does not increase abnormally, and the current DC input branch continues to be forward-conducted, that is, the fast forward-conducting positive electrode component and the fast forward-conducting negative electrode component in the current DC input branch are kept in a conducting state. When it is monitored that the bus voltage exceeds the overvoltage limit, it is determined that the bus voltage increases abnormally, and the controller turns on the fast reverse-conducting positive electrode component and the fast reverse-conducting negative electrode component in the current DC input branch through a drive circuit, and at the same time turns off the fast forward-conducting positive electrode component and the fast forward-conducting negative electrode component. Since the bus voltage is relatively high, the active current at the DC bus can be fed back to the DC input terminal of the current inverter power supply, so that the DC bus voltage drops to a range that does not exceed the overvoltage limit (that is, the DC bus voltage returns to normal).

[0065] Step 5, continue to monitor the bus voltage, when the bus voltage is less than the predetermined voltage threshold in the reverse conduction state, forward conduct the current DC input branch again, when the bus voltage is still greater than or equal to the predetermined voltage threshold in the reverse conduction state, turn on the DC bus tie switch SD0, and feed back the active current to the DC input terminals of all the inverter power supplies arranged in parallel;

[0066] After the current DC input branch is reversed, the controller continues to monitor the bus DC line voltage in real time through the sampling component. When the bus voltage is less than the predetermined voltage threshold in the reverse conduction state, the controller turns on the fast forward conduction positive component and the fast forward conduction negative component in the current DC input branch through the driving circuit, and at the same time turns off the fast reverse conduction positive component and the fast reverse conduction negative component, so that the current DC input branch is forward-conducted, and the DC power supply continues to supply power to the inverter circuit. When the bus voltage is still greater than or equal to the predetermined voltage threshold in the reverse conduction state, the controller turns on the DC bus tie switch SD0, and feeds back the active current to the DC input terminals of all parallel inverter power supplies, so that the DC bus voltage drops to a range not exceeding the overvoltage limit.

[0067] In this embodiment, when there are three situations in the entire power supply process, namely, multiple inverters are connected in parallel, the inverter is directly connected to the shore power grid in parallel, or the inverter output end carries a back electromotive force load, the DC bus in the inverter is prone to abnormal voltage increase. The abnormal increase in the DC bus voltage will cause the DC overvoltage protection to shut down, which is not conducive to the operation of the inverter. By real-time monitoring the bus DC line voltage in the above steps 4 to 5, and when the bus voltage abnormally rises and exceeds the preset overvoltage limit, the active current at the DC bus is fed back to the DC input end in time by reverse conducting the branch and closing the DC bus switch, the DC bus voltage can be restored to normal, avoiding protection shutdown caused by DC overvoltage, so that the inverter can work stably without interruption due to DC overvoltage.

[0068] The control method of the present invention introduces a voltage difference protection judgment, sets the voltage thresholds of the DC input terminal and the DC bus, and when it is monitored that the DC input voltage and the DC bus voltage are lower than the corresponding thresholds, or the DC input switch is opened, the DC input is switched to the DC in time, avoiding the impact caused by the bus voltage drop, and also effectively reducing the instantaneous charging current caused by the switching when the voltage difference is large, ensuring the smooth operation of the inverter switching process. Compared with the control method in the prior art that switches according to the single condition of voltage size, the control method of the present invention detects abnormalities and the entire process of switching occurs before the branch voltage drops significantly, which can effectively reduce the impact of the voltage difference, and the use time is within 10ms. The switching time in the prior art is between tens to hundreds of milliseconds. Compared with the prior art, the control method of the present invention is faster and safer, and improves the reliability of the operation of the DC input high-power power conversion device.

[0069] The steps in this application can be adjusted in order, combined, and deleted according to actual needs.

[0070] The units in the device of the present application can be combined, divided and deleted according to actual needs.

[0071] Although the present application is disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and are not intended to limit the application of the present application. The scope of protection of the present application is defined by the appended claims and may include various modifications, alterations and equivalents made to the invention without departing from the scope and spirit of the present application.

Claims

1. A high-power bidirectional dual-channel DC input automatic switching control method, the method is used for multiple inverter power supplies arranged in parallel, adjacent inverter power supplies are connected through a DC bus switch, a single inverter power supply is internally provided with a controller, an inverter circuit, a voltage sampling component, a drive circuit and two DC input branches with the same structure, the two DC input branches are arranged in parallel and the output ends of the two DC input branches are respectively connected to the inverter circuit through a DC bus, characterized in that: The method includes: Step 1: Use the two DC input branches as the main branch and the standby branch respectively, and close the DC switch between the DC power supply and the inverter power supply input terminal; Step 2, using the slow-start components in the two DC input branches to limit the DC input current to a preset safety value, and after the voltage of the DC bus reaches a predetermined range, controlling the fast forward conduction positive component and the fast forward conduction negative component in the main branch to conduct through the controller, so that the main branch is forward-conducted, so that the DC power supply supplies power to the inverter circuit through the main branch; Step 3, using the controller to monitor the input voltage of the main branch, the bus voltage and the state of the DC switch in real time, when the monitoring result meets the preset conditions, switch the DC input branch, when the monitoring result does not meet the preset conditions, continue to use the main branch for power supply, wherein the preset conditions are: the bus voltage is lower than the first threshold or the DC input voltage is lower than the second threshold or the DC switch is open; Step 4, judging whether to conduct the DC input branch in reverse according to the bus voltage, when the bus voltage does not exceed the preset overvoltage limit, continue to conduct the current DC input branch in forward direction, when the bus voltage exceeds the overvoltage limit, control the fast reverse conduction positive electrode component and the fast reverse conduction negative electrode component in the current DC input branch to conduct through the controller, so that the current DC input branch is reversely conducted, and the active current is fed back to the DC input terminal of the current inverter power supply, and step 4 is executed; Step 5, continue to monitor the bus voltage. When the bus voltage is less than the predetermined voltage threshold in the reverse conduction state, forward conduct the current DC input branch again. When the bus voltage is still greater than or equal to the predetermined voltage threshold in the reverse conduction state, turn on the DC bus tie switch to feed back the active current to the DC input terminals of all parallel-connected inverter power supplies.

2. The high-power bidirectional dual-path DC input automatic switching control method according to claim 1, characterized in that: The step 2 specifically includes: After the DC switch is turned on, the DC input current reaches the DC bus through the slow-start components in the two DC input branches, and the voltage of the DC bus gradually increases. The slow-start component limits the DC input current to a preset safety value through an internal resistor, and the controller monitors the voltage of the DC bus in real time through a voltage sampling component. After the voltage of the DC bus reaches a predetermined range, the controller controls the fast forward conducting positive component and the fast forward conducting negative component in the main branch to be turned on through a drive circuit, and the DC power supply supplies power to the inverter circuit through the main branch. The inverter circuit converts the DC input current into an AC current and outputs the AC current.

3. The high-power bidirectional dual-path DC input automatic switching control method according to claim 2, characterized in that: The step 3 specifically includes: Voltage sampling components are respectively arranged between the positive and negative poles of the DC input branch input terminal and between the positive and negative poles of the DC bus. The controller monitors the main branch input terminal voltage and the bus DC line voltage in real time through the voltage sampling components. The controller is connected to the DC switch. The controller monitors the state of the DC switch in real time. When at least one of the following conditions is met: the bus voltage is lower than a first threshold, the DC input voltage is lower than a second threshold, or the DC switch is opened, it is determined that the DC input of the current inverter power supply is in an abnormal state. The controller quickly turns on the fast forward conducting positive electrode component and the fast forward conducting negative electrode component in the spare branch through the driving circuit, and uses the spare branch to power the inverter circuit. When all conditions are not met, it is determined that the DC input of the current inverter power supply is in a normal working state, and the main branch continues to be used to power the inverter circuit.

4. The high-power bidirectional dual-path DC input automatic switching control method according to claim 3, characterized in that: The step 4 specifically includes: The overvoltage limit is preset so that the overvoltage limit is less than the maximum operating voltage of all devices inside the inverter power supply. The controller monitors the bus DC line voltage in real time through the voltage sampling component. When the bus voltage does not exceed the preset overvoltage limit, it is determined that the bus voltage does not increase abnormally and the current DC input branch continues to be forward-conducted. When the bus voltage exceeds the overvoltage limit, it is determined that the bus voltage increases abnormally. The controller turns on the fast reverse-conducting positive component and the fast reverse-conducting negative component in the current DC input branch through the drive circuit, and turns off the fast forward-conducting positive component and the fast forward-conducting negative component at the same time, and feeds back the active current at the DC bus to the DC input terminal of the current inverter power supply, so that the DC bus voltage drops to a range less than or equal to the overvoltage limit.

5. The high-power bidirectional dual-path DC input automatic switching control method according to claim 4, characterized in that: The step 5 specifically includes: The controller continues to monitor the bus DC line voltage in real time through the sampling component. When the bus voltage is less than the preset voltage threshold in the reverse conduction state, the controller turns on the fast forward conduction positive component and the fast forward conduction negative component in the current DC input branch through the driving circuit, and turns off the fast reverse conduction positive component and the fast reverse conduction negative component at the same time. When the bus voltage is still greater than or equal to the preset voltage threshold in the reverse conduction state, the controller turns on the DC bus tie switch to feed back the active current to the DC input terminals of all parallel inverter power supplies, so that the DC bus voltage drops to a range not exceeding the overvoltage limit.

6. A device for executing the high-power bidirectional dual-path DC input automatic switching control method according to any one of claims 1 to 5, characterized in that: The device comprises: an inverter circuit and two DC input branches with the same structure; The input ends of the two DC input branches are connected to the DC power supply through the DC switch respectively, the output ends of the two DC input branches are connected to the inverter circuit through the DC bus respectively, and the DC power supply supplies power to the inverter circuit through any one of the DC input branches; The DC input branch comprises a slow-start component, a fast forward conducting positive electrode component, a fast reverse conducting positive electrode component, a fast forward conducting negative electrode component and a fast reverse conducting negative electrode component, wherein the slow-start component, the fast forward conducting positive electrode component and the fast reverse conducting positive electrode component are arranged in parallel between the positive electrode of the input end of the DC input branch and the positive electrode of the DC bus, and the fast forward conducting negative electrode component and the fast reverse conducting negative electrode component are arranged in parallel between the negative electrode of the input end of the DC input branch and the negative electrode of the DC bus; The slow-start component is used to limit the DC input current to a safe value when the main power is first turned on until the DC bus voltage reaches a preset DC input voltage; The fast forward conducting positive electrode component and the fast forward conducting negative electrode component are used to forward conduct the DC input branch under the triggering of the driving circuit, so that the DC power supply supplies power to the inverter circuit; The fast reverse conducting positive electrode component and the fast reverse conducting negative electrode component are used to reverse conduct the DC input branch under the triggering of the driving circuit, so that the inverter circuit feeds back the active current to the input end of the DC input branch; The inverter circuit is used to convert input direct current into alternating current for output.

7. The high-power bidirectional dual-path DC input automatic switching device according to claim 6, characterized in that: The input end of the slow-start component is connected to the positive input end of the DC input branch, and the output end of the slow-start component is connected to the positive DC bus; The slow-start component is composed of a diode and a resistor connected in series, wherein the resistor is used to slow down the rate of current rise, and the diode is used to limit the current to conduct forward.

8. The high-power bidirectional dual-path DC input automatic switching device according to claim 6, characterized in that: The input end of the fast forward conducting positive electrode assembly is connected to the positive electrode of the input end of the DC input branch, and the output end of the fast forward conducting positive electrode assembly is connected to the positive electrode of the DC bus; The fast forward conducting positive electrode component is composed of a thyristor rectifier, a capacitor, a resistor and a diode. The resistor and the diode are connected in parallel and the whole formed in parallel is connected in series with the capacitor. The whole formed by the capacitor, the resistor and the diode is connected in parallel with the thyristor rectifier. The thyristor rectifier is used to control the on and off of the fast forward conducting positive electrode component according to the trigger signal sent by the drive circuit. The capacitor is used to smooth the voltage change of the fast forward conducting positive electrode component through the charging and discharging process. The resistor is used to prevent the component from being damaged by excessive current. The diode is used to prevent the current from flowing in the reverse direction in the fast forward conducting positive electrode component, wherein the direction of the anode of the thyristor rectifier is the input end of the fast forward conducting positive electrode component, and the direction of the cathode of the thyristor rectifier is the output end of the fast forward conducting positive electrode component; The input end of the fast reverse conducting positive electrode assembly is connected to the positive electrode of the DC bus, and the output end of the fast reverse conducting positive electrode assembly is connected to the positive electrode of the input end of the DC input branch; The composition structure of the fast reverse conducting positive electrode assembly is the same as that of the fast forward conducting positive electrode assembly, and the conducting direction of the fast reverse conducting positive electrode assembly is opposite to that of the fast forward conducting positive electrode assembly.

9. The high-power bidirectional dual-path DC input automatic switching device according to claim 4, characterized in that: The input end of the fast forward conducting negative electrode assembly is connected to the negative electrode of the input end of the DC input branch, the output end of the fast forward conducting negative electrode assembly is connected to the negative electrode of the DC bus, the composition structure of the fast forward conducting negative electrode assembly is the same as that of the fast forward conducting positive electrode assembly, and the conduction direction of the fast forward conducting negative electrode assembly is the same as that of the fast forward conducting positive electrode assembly; The input end of the fast reverse conducting negative electrode component is connected to the positive pole of the DC bus, the output end of the fast reverse conducting negative electrode component is connected to the positive pole of the input end of the DC input branch, the composition structure of the fast reverse conducting negative electrode component is the same as that of the fast forward conducting positive electrode component, and the fast reverse conducting negative electrode component is opposite to the fast forward conducting positive electrode component.

10. The high-power bidirectional dual-path DC input automatic switching device according to claim 6, characterized in that: The automatic switching device also includes: a voltage sampling component, a drive circuit and a controller; The voltage sampling component measures the voltage at the DC input branch input terminal and the DC bus; The driving circuit is used to control the on and off of the fast forward conducting positive electrode component, the fast reverse conducting positive electrode component, the fast forward conducting negative electrode component and the fast reverse conducting negative electrode component through a trigger signal; The controller is used to control the drive circuit to send a trigger signal to each component according to the voltage value of the DC input branch input terminal and the DC bus.

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