Power Converter

Abstract

An embodiment of the present application provides a power converter, which includes at least two bridge arms, a first switch and a controller. The bridge arm includes an output end and a plurality of switch tubes, and the conduction and shutdown of the plurality of switch tubes are used to convert the direct current from the photovoltaic module or the energy storage battery into alternating current and output the alternating current through the output end. The first switch is connected in series between the output ends of any two bridge arms in at least two bridge arms. The controller is used to control the first switch to close, so as to realize the electrical connection of the switch tube that is partially turned on in the first bridge arm and the switch tube that is partially turned on in the second bridge arm in at least two bridge arms and form a current loop, and when the current value of the current loop is less than or equal to the set threshold value, the controller sends an alarm signal.

Description

Technical Field

[0001] The present application relates to the field of power electronics, and in particular to a power converter. Background Art

[0002] As the core component of the inverter, the power module directly determines the product quality of the inverter. However, most power modules are not tested in the factory. The mechanical stress of the module crimping, the parasitic parameters of the printed circuit board after installation, the tolerance of the drive resistor and other extreme working conditions are all causes of power module damage. Therefore, it is very important to screen out the faulty power module before the power module fails and avoid the sudden failure of the inverter during operation, which is very important for improving the reliability of the inverter. Summary of the invention

[0003] The present application provides a power converter, which can detect a faulty bridge arm in the power converter to avoid sudden failure of the power converter during operation.

[0004] In a first aspect, the present application provides a power converter, which includes at least two bridge arms, a first switch and a controller. The bridge arm includes an output end and a plurality of switch tubes, and the conduction and shutdown of the plurality of switch tubes are used to convert the direct current from the photovoltaic component or the energy storage battery into alternating current and output the alternating current through the output end. The first switch is connected in series between the output ends of any two bridge arms in at least two bridge arms. The controller is used to control the closing of the first switch to achieve electrical connection between the switch tubes partially conducting on the first bridge arm and the switch tubes partially conducting on the second bridge arm in at least two bridge arms and form a current loop, and when the current value of the current loop is less than or equal to the set threshold, the controller sends an alarm signal.

[0005] In this embodiment, the controller is used to control the first switch to close, so as to realize the electrical connection of the switch tube partially turned on in the first bridge arm and the switch tube partially turned on in the second bridge arm in at least two bridge arms and form a current loop. The above-mentioned control of the first switch to close can be to control one or more first switches to close. Specifically, the controller is used to control the first switch to close so that the output end of the first bridge arm is short-circuited with the output end of the second bridge arm, and to control the electrical connection of the switch tube partially turned on in the first bridge arm and the switch tube partially turned on in the second bridge arm in at least two bridge arms and form a current loop. Finally, if it is detected that the current value of the current loop rises and exceeds the set threshold, the above-mentioned current loop is valid, the devices on the current loop are normal, and some of the switch tubes on the first bridge arm and the second bridge arm can be turned on normally. If it is detected that the current value of the current loop is less than or equal to the set threshold, the device on the current loop fails, and the controller sends an alarm signal to prompt the power converter to have a bridge arm failure, so as to avoid sudden failure of the power converter during operation. Here, the controller controls the partially conductive switch tube on the first bridge arm and the partially conductive switch tube on the second bridge arm to be electrically connected and form a current loop, so that a double pulse test is performed based on the current loop to detect the faulty bridge arm, thereby improving the test efficiency of the power converter.

[0006] In a possible implementation, the power converter further includes a second switch, which is connected to the output end of at least two bridge arms and is used to connect to a power grid or a load. The controller is also used to control the second switch to be disconnected before controlling the formation of a current loop, and then control the first switch to be closed. Here, the controller controls the power converter to be off-grid or not connected to the load, that is, controls the second switches connected to each bridge arm to be turned off, thereby avoiding interference of the alternating current from the power grid on the fault detection bridge arm.

[0007] In a possible implementation, the power converter further includes an inductor, which is connected in series between the first switch and the output end of the bridge arm. After the power converter forms a current loop and the current value of the current loop is greater than the set threshold, the controller is also used to continue to control the first switch to close, so as to realize the electrical connection of the partially conductive switch tube in the first bridge arm and the partially conductive switch tube in the second bridge arm in at least two bridge arms and form a freewheeling loop of the inductor, and the freewheeling loop and the current loop include at least partially different switch tubes. If the freewheeling loop is not established, the controller sends an alarm signal. Here, after the current loop is formed, a freewheeling loop is formed in the power converter due to the discharge of the inductor, and other switch tubes outside the current loop are further detected through the freewheeling loop. If the freewheeling loop is not established, the switch tube and other devices on the freewheeling loop are faulty, and the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0008] In a possible implementation, the power converter further includes a bus capacitor, which is connected in series in the current loop to provide electrical energy for the current loop. After the power converter forms the current loop, the bus capacitor is discharged, and the controller detects whether a device in the current loop fails based on the current value of the current loop.

[0009] In a possible implementation, the bus capacitor includes a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus. At least two bridge arms are connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube connected in series in sequence, and the series connection point of the first switch tube and the second switch tube is connected to the series connection point of the third switch tube and the fourth switch tube through two series-connected diodes, and the series connection point of the two series-connected diodes is connected to the series connection point of the first capacitor and the second capacitor, and the series connection point of the second switch tube and the third switch tube in each bridge arm serves as the output end of each bridge arm.

[0010] In a possible implementation, the bus capacitor includes a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus. At least two bridge arms are connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series in sequence, and the series connection point of the first switch tube and the second switch tube is connected to the series connection point of the third switch tube and the fourth switch tube through the fifth switch tube and the sixth switch tube connected in series, and the series connection point of the fifth switch tube and the sixth switch tube connected in series is connected to the series connection point of the first capacitor and the second capacitor, and the series connection point of the second switch tube and the third switch tube in each bridge arm serves as the output end of each bridge arm.

[0011] In a possible implementation, the controller is also used to control the first switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the fourth switch tube in the second bridge arm to be turned on periodically, and to control the third switch tube in the second bridge arm and the second switch tube in the first bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor and the second capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0012] In a possible implementation, the controller is also used to control the second switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the third switch tube and the fourth switch tube in the second bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the second capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0013] In a possible implementation, the controller is also used to control the third switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the first switch tube and the second switch tube in the second bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0014] In a possible implementation, the controller is also used to control the fourth switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the first switch tube in the second bridge arm to be turned on periodically, and the second switch tube in the second bridge arm and the third switch tube in the first bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor and the second capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0015] In a possible implementation, the controller is also used to control the fifth switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the first switch tube and the second switch tube in the second bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0016] In a possible implementation, the controller is also used to control the sixth switch tube in the first bridge arm to be turned on periodically, and to control the third switch tube and the fourth switch tube in the second bridge arm to remain turned on, after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed. Here, if the switch tube and other devices in the current loop are normal, the inductor connected to the first bridge arm can draw power from the second capacitor, that is, it can be detected that the current value on the inductor connected to the first bridge arm increases. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices in the current loop are faulty.

[0017] In a possible implementation, the bus capacitor includes a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus. At least two bridge arms are connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, the first switch tube and the fourth switch tube are connected in series, and the series connection point of the first switch tube and the fourth switch tube is connected to the series connection point of the first capacitor and the second capacitor through the second switch tube and the third switch tube connected in reverse series, and the series connection point of the first switch tube and the fourth switch tube in each bridge arm serves as the output end of each bridge arm.

[0018] In a possible implementation, the controller is also used to control the first switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the fourth switch tube in the second bridge arm to be turned on periodically, and to control the third switch tube in the second bridge arm and the second switch tube in the first bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor and the second capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0019] In a possible implementation, the controller is also used to control the second switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the fourth switch tube in the second bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the second capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0020] In a possible implementation, the controller is also used to control the third switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the first switch tube in the second bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0021] In a possible implementation, the controller is also used to control the fourth switch tube in the first bridge arm to be turned on periodically after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to be closed, and to control the first switch tube in the second bridge arm to be turned on periodically, and the second switch tube in the second bridge arm and the third switch tube in the first bridge arm to remain turned on to form a current loop. Here, if the switch tube and other devices on the current loop are normal, the inductor connected to the first bridge arm can draw power from the first capacitor and the second capacitor, that is, the current value on the inductor connected to the first bridge arm can be detected to increase. Otherwise, if the current value on the inductor is detected to be less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty.

[0022] In a possible implementation, the power converter further includes a third switch, which is connected in series between the second switch and the inductor. When the output ends of two bridge arms in at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series point of the inductor connected to the output end of one bridge arm and the third switch, and the other end of the first switch is connected to the series point of the inductor connected to the output end of another bridge arm and the third switch. Here, the output ends of each bridge arm are connected to the first switch and the third switch connected in series, which can avoid the situation where the bridge arm cannot be disconnected from the power grid when any of the first switch and the third switch connected to each bridge arm fails.

[0023] In a possible implementation, the power converter further includes a third switch, which is connected in series between the second switch and the inductor. When the output ends of two bridge arms in at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series point of the inductor connected to the output end of one bridge arm and the third switch, and the other end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of another bridge arm. Here, the output ends of each bridge arm are connected to the first switch and the third switch connected in series, which can avoid the situation where the bridge arm cannot be disconnected from the power grid when any of the first switch and the third switch connected to each bridge arm fails.

[0024] In a possible implementation, the power converter further includes a third switch, which is connected in series between the second switch and the inductor. When the output ends of two bridge arms in at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series connection point of the second switch and the third switch connected to the output end of one bridge arm, and the other end of the first switch is connected to the series connection point of the second switch and the third switch connected to the output end of another bridge arm. Here, the output ends of each bridge arm are connected to the first switch and the third switch connected in series, which can avoid the situation where the bridge arm cannot be disconnected from the power grid when any of the first switch and the third switch connected to each bridge arm fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of an application scenario of the power supply system provided by this application;

[0026] Figure 2 is a schematic diagram of another application scenario of the power supply system provided by the present application;

[0027] Figure 3 is a structural schematic diagram of a power converter provided by the present application;

[0028] Figure 4 is another structural schematic diagram of the power converter provided by the present application;

[0029] Figure 5 is another structural schematic diagram of the power converter provided by the present application;

[0030] Figure 6 is another structural schematic diagram of the power converter provided by the present application;

[0031] Figure 7 is another structural schematic diagram of the power converter provided by the present application;

[0032] Figure 8 is another structural schematic diagram of the power converter provided by the present application;

[0033] Fig. 9 is another structural schematic diagram of the power converter provided by the present application;

[0034] Fig.10 is another structural schematic diagram of the power converter provided by the present application;

[0035] Fig.11 is another structural schematic diagram of the power converter provided by the present application;

[0036] Fig.12 is another structural schematic diagram of the power converter provided by the present application;

[0037] Fig.13 is another structural schematic diagram of the power converter provided by the present application;

[0038] Fig.14 is another structural schematic diagram of the power converter provided by the present application;

[0039] Fig.15 is another structural schematic diagram of the power converter provided by the present application;

[0040] Fig.16 is another structural schematic diagram of the power converter provided by the present application;

[0041] Fig.17 is another structural schematic diagram of the power converter provided by the present application;

[0042] Fig.18 is another structural schematic diagram of the power converter provided by the present application;

[0043] Fig.19 is another structural schematic diagram of the power converter provided by the present application;

[0044] Fig. 20 is another structural schematic diagram of the power converter provided by the present application;

[0045] Fig.21 It is another structural schematic diagram of the power converter provided by the present application. DETAILED DESCRIPTION

[0046] See also Figure 1 , Figure 1 : This is a schematic diagram of an application scenario of the power supply system provided by the present application. The power supply system provided by the present application may include a DC power supply and at least one power converter, wherein the DC power supply is a photovoltaic module. Taking the power supply system including multiple power converters as an example, the DC end of the power converter is used to connect the photovoltaic module, and the AC end of the power converter is connected in parallel to connect the power grid or load. The power converter can invert the DC power provided by the photovoltaic module, and output the AC power obtained after the inversion conversion to the power grid or load for power supply.

[0047] In some feasible implementations, the DC power source is a storage battery, and the DC end of each power converter can be used to connect to the storage battery. Figure 2 , Figure 2It is another application scenario schematic diagram of the power supply system provided by the present application. Among the multiple power converters of the power supply system, the DC end of some power converters is used to connect the energy storage battery, and the AC end of multiple power converters is connected in parallel to connect the power grid or load. Each power converter can invert the DC power provided by the photovoltaic module or the energy storage battery, and output the AC power obtained after the inversion conversion to the power grid or load for power supply. Here, the power converter connected to the photovoltaic module in the power supply system can be an inverter, and the power converter connected to the energy storage battery in the power supply system can be a converter.

[0048] exist Figure 1 or Figure 2 In the application scenario of the power supply system shown, the power converter in the power supply system includes a power module and a controller. The power module may include a bridge arm. The controller in the power converter controls the switch tube in the bridge arm so that the power converter performs an inversion conversion on the direct current provided by the photovoltaic module or the energy storage battery. During the operation of the power converter, the power module may fail, such as a switch tube failure in the bridge arm, which may cause the power converter to fail to work normally. In order to avoid sudden failure of the power converter during operation, it is necessary to screen out the faulty bridge arm. For example, periodic detection is performed on each power converter in the power supply system. When a bridge arm fault is detected in the power converter, the corresponding power converter is replaced or repaired, thereby reducing the failure rate of the power converter.

[0049] The power converter comprises a controller, a first switch and at least two bridge arms. Figure 3 , Figure 3 Schematic diagram of a power converter provided by the present application. Figure 3 As shown, the power converter may include a controller ( Figure 3Not shown) and n bridge arms, namely including bridge arm 1, bridge arm 2, ..., bridge arm n-1 and bridge arm n, n is an integer greater than 1. Wherein, the first switch is connected in series between the output ends of any two bridge arms in at least two bridge arms. Specifically, one or more first switches can be connected in series between the output ends of any two bridge arms in at least two bridge arms, for example, the output ends of bridge arm 1 and bridge arm 2 are connected through switch Ka1, the output ends of bridge arm 2 and bridge arm 3 are connected through switch Ka2, ..., the output ends of adjacent bridge arm n-1 and bridge arm n in the power converter are connected through switch Kan-1. Further, the output ends of bridge arm 1 and bridge arm 3 are connected through switch Ka1 and switch Ka2, the output ends of bridge arm 1 and bridge arm 4 are connected through switch Ka1, switch Ka2 and switch Ka3, and so on. The specific connection method between the output ends of any other two bridge arms is similar and will not be repeated here. When the power converter is subjected to a double pulse test to detect a faulty bridge arm, the power converter is controlled to be off-grid or not connected to a load. At this time, the controller controls at least one first switch to be turned on to short-circuit the output end of the first bridge arm and the output end of the second bridge arm in the above-mentioned bridge arm 1, bridge arm 2, ..., bridge arm n-1 and bridge arm n. For example, the controller can control switch Ka1 to be turned on so that the output ends of bridge arm 1 and bridge arm 2 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 2. Alternatively, the controller can control switch Ka1 and switch Ka2 to be turned on so that the output ends of bridge arm 1 and bridge arm 3 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 3.

[0050] In some feasible implementations, the power converter may further include a second switch, which is connected to the output ends of at least two bridge arms and is used to connect to a power grid or a load. Figure 4 , Figure 4 is another schematic diagram of the structure of the power converter provided by the present application. Figure 4 As shown, the output ends of bridge arm 1, bridge arm 2, ..., bridge arm n-1 and bridge arm n are connected to an AC end of the power converter through switches Kb1, switch Kb2, ..., switch Kbn-1 and switch Kbn respectively. Figure 4As shown, when the power converter is connected to the grid or connected to the load, that is, when the bridge arm 1, bridge arm 2, ..., bridge arm n-1 and the second switch connected to the bridge arm n are all turned on, the controller controls the switch tubes in the bridge arm 1, bridge arm 2, ..., bridge arm n-1 and bridge arm n to act, so that each bridge arm converts the direct current from the photovoltaic module or the energy storage battery into alternating current and outputs it to the grid or load. Further, when the power converter is subjected to a double pulse test to detect the faulty bridge arm, the power converter is controlled to be off the grid or not connected to the load, that is, the second switches connected to the bridge arm 1, bridge arm 2, ..., bridge arm n-1 and bridge arm n are all turned off, so as to avoid the interference of the alternating current from the grid on the detection of the faulty bridge arm. Then the controller controls at least one first switch to be turned on to short-circuit the output end of the first bridge arm in the above-mentioned bridge arm 1, bridge arm 2, ..., bridge arm n-1 and bridge arm n with the output end of the second bridge arm. For example, when switches Kb1, Kb2, ..., Kbn are turned off, the controller can control switch Ka1 to be turned on, so that the output ends of bridge arm 1 and bridge arm 2 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 2.

[0051] Optionally, the power converter may include two bridge arms, see Figure 5 , Figure 5 is another schematic diagram of the structure of the power converter provided by the present application. Figure 5 As shown, the power converter may include two bridge arms, namely, bridge arm 1 and bridge arm 2. The output ends of bridge arm 1 and bridge arm 2 are connected via switch Ka1, and the output ends of bridge arm 1 and bridge arm 2 are connected to an AC end of the power converter via switches Kb1 and Kb2, respectively. One end of the switch Ka1 is connected to the series point between the output end of bridge arm 1 and switch Kb1, and the other end of the switch Ka1 is connected to the series point between the output end of bridge arm 2 and switch Kb2.

[0052] Optionally, the power converter may include three bridge arms, see Figure 6 , Figure 6 is another schematic diagram of the structure of the power converter provided by the present application. Figure 6 As shown, the power converter may include three bridge arms, and the three bridge arms may be ABC three-phase bridge arms (for convenience of description, they may be respectively represented as bridge arm 1, bridge arm 2 and bridge arm 3), the output ends of bridge arm 1 and bridge arm 2 are connected through switch Ka1, and the output ends of bridge arm 2 and bridge arm 3 are connected through switch Ka2. The output ends of bridge arm 1, bridge arm 2 and bridge arm 3 are respectively connected to an AC end of the power converter through switch Kb1, switch Kb2 and switch Kb3, one end of the switch Ka1 is connected to the series point of the output end of bridge arm 1 and switch Kb1, and the other end of switch Ka1 is connected to the series point of the output end of bridge arm 2 and switch Kb2, and the connection method of switch Ka2 is similar to that of the switch Ka1.

[0053] In some feasible implementations, the power converter further includes an inductor, which is connected in series between the first switch and the output end of the bridge arm. Figure 6 , the output ends of bridge arm 1, bridge arm 2 and bridge arm 3 are connected to inductor L1, inductor L2 and inductor L3 respectively, wherein inductor L1 is connected in series between switch Ka1 connected to bridge arm 1 and the output end of bridge arm 1, inductor L2 is connected in series between switch Ka1 and switch Ka2 connected to bridge arm 2 and the output end of bridge arm 2, and inductor L3 is connected in series between switch Ka3 connected to bridge arm 3 and the output end of bridge arm 3. In other words, the output ends of bridge arm 1, bridge arm 2 and bridge arm 3 are connected to one end of inductor L1, inductor L2 and inductor L3 respectively, and the other ends of inductor L1, inductor L2 and inductor L3 are connected to an AC end of the power converter through switch Kb1, switch Kb2 and switch Kb3 respectively.

[0054] Optionally, the power converter may further include a capacitor, see again Figure 6 , Figure 6 In the power converter shown, the other end of any bridge arm (or, may be referred to as the output end) is connected to one end of an inductor, and the other end of the inductor is connected to the series point of capacitor C1 and capacitor C2 through a capacitor. For example, the output ends of bridge arm 1, bridge arm 2, and bridge arm 3 are respectively connected to one end of inductor L1, inductor L2, and inductor L3, and the other ends of inductor L1, inductor L2, and inductor L3 are respectively connected to the series point of capacitor C1 and capacitor C2 through capacitor C10, capacitor C20, and capacitor C30.

[0055] Above Figure 6In the power converter shown, the controller is used to control the first switch to close, so as to realize the electrical connection between the switch tube partially turned on in the first bridge arm and the switch tube partially turned on in the second bridge arm in at least two bridge arms and form a current loop. The above-mentioned control of the first switch to close can be to control one or more first switches to close. Specifically, the controller is used to control the first switch to close so that the output end of the first bridge arm is short-circuited with the output end of the second bridge arm, and to control the electrical connection between the switch tube partially turned on in the first bridge arm and the switch tube partially turned on in the second bridge arm in at least two bridge arms and form a current loop. Specifically, the controller controls some of the switch tubes in the first bridge arm to turn on periodically, and controls some of the switch tubes in the second bridge arm to turn on, or controls some of the switch tubes in the first bridge arm to turn on periodically, and controls some of the switch tubes in the first bridge arm and the second bridge arm to turn on, so that the switch tube partially turned on in the first bridge arm and the switch tube partially turned on in the second bridge arm are electrically connected and form a current loop. For example, the controller can send a pulse drive waveform to some of the switch tubes in the first bridge arm, so that some of the switch tubes are briefly turned on in each switching cycle. Finally, if the current value of the current loop is detected to rise, the above current loop is valid, the devices on the current loop are normal, and some of the switch tubes on the first bridge arm and the second bridge arm can be turned on normally. If the current value of the current loop is detected to be less than or equal to the set threshold, or the current on the inductor connected to the first bridge arm is less than or equal to the set threshold, the device on the current loop fails, and the controller sends an alarm signal to prompt the power converter to have a bridge arm failure, so as to avoid the sudden failure of the power converter during operation. Here, the controller controls at least one first switch to be turned on, so that the output end of the first bridge arm in the power converter is short-circuited with the output end of the second bridge arm, and at the same time controls the switch tube on the first bridge arm to be partially turned on and the switch tube on the second bridge arm to be electrically connected and form a current loop, so as to perform a double pulse test based on the current loop to detect the faulty bridge arm, thereby improving the test efficiency of the power converter. In addition, when the power converter is connected to the power grid in parallel with other power converters, during the double pulse test, only the part of the power converter that needs to be detected needs to be disconnected from the grid, and other power converters in the power supply system remain in normal operation, so as to avoid excessive power generation loss in the power supply system.

[0056] In some feasible implementations, the power converter may further include a third switch connected in series between the second switch and the inductor. When the output ends of two bridge arms in at least two bridge arms are connected via a first switch, one end of the first switch is connected to a series point of the inductor connected to the output end of one bridge arm and the third switch, and the other end of the first switch is connected to a series point of the inductor connected to the output end of another bridge arm and the third switch.

[0057] With the above Figure 6 Take the power converter shown in the figure as an example, see Figure 7 , Figure 7is another schematic diagram of the structure of the power converter provided by the present application. Figure 7 As shown, the output ends of bridge arm 1, bridge arm 2 and bridge arm 3 in the power converter are respectively connected to one end of inductor L1, inductor L2 and inductor L3, the other end of inductor L1 is connected to an AC end of the power converter through switches Kb1 and Kc1 connected in series, the other end of inductor L2 is connected to an AC end of the power converter through switches Kb2 and Kc2 connected in series, and the other end of inductor L3 is connected to an AC end of the power converter through switches Kb3 and Kc3 connected in series. The output end of each bridge arm is connected to the second switch and the third switch connected in series, which can avoid the situation that the power grid cannot be disconnected when any switch of the second switch and the third switch connected to each bridge arm fails. When the output ends of two bridge arms in at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series connection point of the inductor connected to the output end of one bridge arm and the third switch, and the other end of the first switch is connected to the series connection point of the inductor connected to the output end of another bridge arm and the third switch. For example, the output ends of bridge arm 1 and bridge arm 2 are connected through switch Ka1, the inductor L1 connected to bridge arm 1 at one end of switch Ka1 is connected to the series point of switch Kc1, and the inductor L2 connected to bridge arm 2 at the other end of switch Ka1 is connected to the series point of switch Kc2. When the power converter is subjected to a double pulse test to detect a faulty bridge arm, the controller can first control switches Kb1, Kb2, Kb3, Kc1, Kc2, and Kc3 to be turned off, and then control switch Ka1 to be turned on, so that the output ends of bridge arm 1 and bridge arm 2 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 2. It can be understood that when the output ends of the other two bridge arms are connected through a first switch, the connection mode of the first switch can be the same as the connection mode of the first switch between the above-mentioned bridge arm 1 and bridge arm 2, or it can be different, and there is no limitation here.

[0058] In some feasible implementations, when the output ends of two bridge arms of at least two bridge arms are connected via a first switch, one end of the first switch is connected to a series connection point of an inductor connected to the output end of one bridge arm and a third switch, and the other end of the first switch is connected to a series connection point of a second switch connected to the output end of another bridge arm and a third switch. Figure 6 Take the power converter shown in the figure as an example, see Figure 8 , Figure 8 is another schematic diagram of the structure of the power converter provided by the present application. Figure 8As shown, the output ends of the bridge arm 1, bridge arm 2 and bridge arm 3 in the power converter are respectively connected to one end of the inductor L1, inductor L2 and inductor L3, the other end of the inductor L1 is connected to an AC end of the power converter through the series switches Kb1 and Kc1, the other end of the inductor L2 is connected to an AC end of the power converter through the series switches Kb2 and Kc2, and the other end of the inductor L3 is connected to an AC end of the power converter through the series switches Kb3 and Kc3. When the output ends of two bridge arms in at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series point of the inductor connected to the output end of one bridge arm and the second switch, and the other end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of another bridge arm. For example, the output ends of the bridge arm 1 and the bridge arm 2 are connected through the switch Ka1, one end of the switch Ka1 is connected to the series point of the inductor L1 connected to the bridge arm 1 and the switch Kc1, and the other end of the switch Ka1 is connected to the series point of the switch Kb2 connected to the bridge arm 2 and the switch Kc2. When a double pulse test is performed on the power converter to detect a faulty bridge arm, the controller can first control switches Kb1, Kb2, Kb3, Kc1, Kc2 and Kc3 to be turned off, and then control switches Ka1 and Kc2 to be turned on, so that the output ends of bridge arm 1 and bridge arm 2 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 2.

[0059] Alternatively, see Fig. 9 , Fig. 9 is another schematic diagram of the structure of the power converter provided by the present application. Fig. 9 As shown, the output ends of bridge arm 1 and bridge arm 2 are connected through switch Ka1, switch Kb1 connected to bridge arm 1 at one end of switch Ka1 is connected to the series point of switch Kc1, and the inductor L2 connected to bridge arm 2 at the other end of switch Ka1 is connected to the series point of switch Kc2. When the power converter is subjected to a double pulse test to detect a faulty bridge arm, the controller can first control switches Kb1, Kb2, Kb3, Kc1, Kc2, and Kc3 to be turned off, and then control switches Ka1 and Kc1 to be turned on, so that the output ends of bridge arm 1 and bridge arm 2 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 2. It can be understood that when the output ends of the other two bridge arms are connected through a first switch, the connection mode of the first switch can be the same as the connection mode of the first switch between the above-mentioned bridge arm 1 and bridge arm 2, or it can be different, and there is no limitation here.

[0060] In some feasible embodiments, when the output ends of two bridge arms of at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of one bridge arm, and the other end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of another bridge arm.

[0061] With the above Figure 6 Take the power converter shown in the figure as an example, see Fig.10 , Fig.10 is another schematic diagram of the structure of the power converter provided by the present application. Fig.10 As shown, the output ends of the bridge arm 1, bridge arm 2 and bridge arm 3 in the power converter are respectively connected to one end of the inductor L1, inductor L2 and inductor L3, the other end of the inductor L1 is connected to an AC end of the power converter through the series switches Kb1 and Kc1, the other end of the inductor L2 is connected to an AC end of the power converter through the series switches Kb2 and Kc2, and the other end of the inductor L3 is connected to an AC end of the power converter through the series switches Kb3 and Kc3. When the output ends of two bridge arms in at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of one bridge arm, and the other end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of another bridge arm. For example, the output ends of the bridge arm 1 and the bridge arm 2 are connected through the switch Ka1, one end of the switch Ka1 is connected to the series point of the switch Kb1 connected to the bridge arm 1 and the switch Kc1, and the other end of the switch Ka1 is connected to the series point of the switch Kb2 connected to the bridge arm 2 and the switch Kc2. When a double pulse test is performed on the power converter to detect a faulty bridge arm, the controller may first control switches Kb1, Kb2, Kb3, Kc1, Kc2 and Kc3 to be turned off, and then control switches Ka1, Kc1 and Kc2 to be turned on, so that the output ends of bridge arm 1 and bridge arm 2 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 2. It is understandable that when the output ends of the other two bridge arms are connected through a first switch, the connection mode of the first switch may be the same as the connection mode of the first switch between the above-mentioned bridge arm 1 and bridge arm 2, or may be different, and is not limited here.

[0062] In some feasible embodiments, the power converter further includes a bus capacitor, which is connected in series in the current loop to provide electrical energy for the current loop. Specifically, the bus capacitor includes a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus. In the above power converter, at least two bridge arms are connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series in sequence, and the series connection point of the first switch tube and the second switch tube is connected to the series connection point of the third switch tube and the fourth switch tube through two diodes connected in series, and the series connection point of the two diodes connected in series is connected to the series connection point of the first capacitor and the second capacitor, and the series connection point of the second switch tube and the third switch tube in each bridge arm serves as the output end of each bridge arm.

[0063] Take the power converter including three bridge arms as an example, see Fig.11 , Fig.11 is another schematic diagram of the structure of the power converter provided by the present application. Fig.11 As shown, Fig.11 The power converter in the embodiment may include a capacitor C1 and a capacitor C2 connected in series, and three bridge arms (bridge arm 1, bridge arm 2 and bridge arm 3), wherein bridge arm 1, bridge arm 2 and bridge arm 3 are three-phase bridge arms ABC respectively, and the above-mentioned bridge arm 1, bridge arm 2 and bridge arm 3 lead out three corresponding ports ABC respectively. Bridge arm 1 may include a switch tube Q11, a switch tube Q12, a switch tube Q13 and a switch tube Q14 connected in series in sequence and connected in parallel at both ends of capacitor C1 and capacitor C2, the series connection point of switch tube Q11 and switch tube Q12 is connected to the series connection point of switch tube Q13 and switch tube Q14 through two series connection diodes D11 and diode D12, the series connection point of the two series connection diodes is connected to the series connection point of capacitor C1 and capacitor C2, and the series connection point of switch tube Q12 and switch tube Q13 can be used as the output end of bridge arm 1 to lead out the A phase port. The bridge arm 2 may include a switch tube Q21, a switch tube Q22, a switch tube Q23, a switch tube Q24, a diode D21 and a diode D22, and the bridge arm 3 may include a switch tube Q31, a switch tube Q32, a switch tube Q33, a switch tube Q34, a diode D31 and a diode D32. It can be understood that Fig. 9 In the power converter shown, the circuit structure of bridge arm 2 and bridge arm 3 is the same as that of bridge arm 1, which will not be described here. Each switch tube in the power converter can be a metal oxide semiconductor field effect transistor (MOSFET), referred to as MOS tube, or an insulated gate bipolar transistor (IGBT), etc., which is not limited here. Fig.11 In the power converter shown, the output ends of the two bridge arms are connected via a first switch, and the output end of each bridge arm is connected to an AC end of the power converter via an inductor, a third switch, and a second switch connected in series in sequence. Here, the connection method of the first switch can be as described above. Figures 7 to 10 The connection mode of the first switch in any power converter shown in Fig.10Taking the connection mode of switch Ka1 in the power converter as an example, one end of switch Ka1 is connected to the series point of switch Kc1 and switch Kb1 connected to bridge arm 1, and the other end of switch Ka1 is connected to the series point of switch Kc2 and switch Kb2 connected to bridge arm 2. Similarly, one end of switch Ka2 is connected to the series point of switch Kc2 and switch Kb2 connected to bridge arm 2, and the other end of switch Ka2 is connected to the series point of switch Kc3 and switch Kb3 connected to bridge arm 3. It can be understood that each first switch in the power converter is not limited to Fig.11 For details on the connection method, please refer to the above Figures 7 to 10 The description of the medium power converter will not be repeated here.

[0064] In some feasible implementations, the above Fig.11 In the power converter shown, when a double pulse test is performed on the power converter to detect a faulty bridge arm, taking the above-mentioned bridge arm 1 as the first bridge arm and bridge arm 3 as the second bridge arm as an example, the controller can first control switches Kb1, Kb2, Kb3, Kc1, Kc2 and Kc3 to be turned off, and then control switches Ka1, Kc1 and Kc2 to be turned on, so that the output ends of bridge arm 1 and bridge arm 3 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 3.

[0065] Further, the controller controls the electrical connection between the partially turned-on switch tubes in the first bridge arm and the partially turned-on switch tubes in the second bridge arm of at least two bridge arms to form a current loop. Specifically, when the output end of the first bridge arm is short-circuited with the output end of the second bridge arm, the controller controls some of the switch tubes in the first bridge arm to be turned on periodically, and controls some of the switch tubes in the second bridge arm to be turned on, or controls some of the switch tubes in the first bridge arm to be turned on periodically, and controls some of the switch tubes in the first bridge arm and the second bridge arm to be turned on, so that the partially turned-on switch tubes in the first bridge arm and the partially turned-on switch tubes in the second bridge arm are electrically connected and form a current loop. For example, the controller controls the first switch tube in the first bridge arm to be turned on periodically, and controls the fourth switch tube in the second bridge arm to be turned on periodically, and the third switch tube in the second bridge arm and the second switch tube in the first bridge arm remain turned on. See again Fig.11After the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q11 in bridge arm 1 to be turned on periodically, and controls the switch tube Q34 in bridge arm 3 to be turned on periodically, and controls the switch tube Q12 in bridge arm 1 and the switch tube Q33 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q11, the switch tube Q12 and the inductor L1 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally passes through the inductor L3, the switch tube Q33, and the switch tube Q34 in sequence to the negative DC bus BUS-. Here, if the switch tubes and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 and the inductor L3 connected to the bridge arm 3 can draw power from the capacitor C1 and the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 remains unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 fails, then the controller sends an alarm signal to prompt the power converter that a bridge arm failure has occurred, so as to avoid sudden failure of the power converter during operation.

[0066] Optionally, when the current on the inductor connected to the first bridge arm is greater than a set threshold, the controller can continue to control the first switch to close and control some of the switch tubes in the first bridge arm to turn off, so as to achieve electrical connection between the partially conductive switch tubes in the first bridge arm and the partially conductive switch tubes in the second bridge arm of at least two bridge arms and form a freewheeling loop of the inductor, and the freewheeling loop includes at least some different switch tubes from the above current loop, so as to detect other switch tubes outside the current loop. If the above freewheeling loop is not established, the controller sends an alarm signal. For example, refer again to Fig.11 After the current loop is formed in the power converter, the controller controls the switch tube Q11 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the turned-on switches Kb1 and Kb2, and then flows back to the inductor L1 through the inductor L3, the switch tube Q33, the diode D32, the diode D11 and the switch tube Q12 in sequence. Here, if the switch tube, diode and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 gradually decreases, that is, the freewheeling loop is established normally. Otherwise, if after controlling the above-mentioned switch tube Q11 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, that is, the freewheeling loop is not established, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, and the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0067] In some feasible implementations, the above Fig.11In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the second switch tube in the first bridge arm to be periodically turned on, and control the third switch tube and the fourth switch tube in the second bridge arm to remain turned on. Fig.12 , Fig.12 is another schematic diagram of the structure of the power converter provided by the present application. Fig.12 As shown, after the output ends of the bridge arm 1 and the bridge arm 3 are short-circuited, the controller controls the switch tube Q12 in the bridge arm 1 to be turned on periodically, and controls the switch tubes Q33 and Q34 in the bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the series connection point of the capacitor C1 and the capacitor C2 (or, it can be called the busbar midpoint), passes through the diode D11 and the switch tube Q12 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally flows back to the capacitor C2 through the inductor L3, the switch tube Q33 and the switch tube Q34 in sequence. Here, if the switch tube and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 can draw power from the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0068] Optional, see again Fig.12 After the current loop is formed in the power converter, the controller controls the switch tube Q12 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the turned-on switches Kb1 and Kb2, and then flows back to the inductor L1 through the inductor L3, the switch tube Q33, the switch tube Q34, the switch tube Q14 and the switch tube Q13 in sequence. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q12 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0069] In some feasible implementations, the above Fig.11 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the third switch tube in the first bridge arm to be turned on periodically, and control the first switch tube and the second switch tube in the second bridge arm to remain turned on. Fig.13 , Fig.13 is another schematic diagram of the structure of the power converter provided by the present application. Fig.13 As shown, after the output ends of the bridge arm 1 and the bridge arm 3 are short-circuited, the controller controls the switch tube Q13 in the bridge arm 1 to be turned on periodically, and controls the switch tubes Q31 and Q32 in the bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q31, the switch tube Q32, and the inductor L3 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally flows back to the inductor L1, the switch tube Q13 and the diode D12 in sequence to flow back to the series connection point of the capacitor C1 and the capacitor C2 (or, it can be called the bus midpoint). Here, if the switch tube and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 can draw power from the capacitor C1, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0070] Optional, see again Fig.13 After the current loop is formed in the power converter, the controller controls the switch tube Q13 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the switch tube Q12, the switch tube Q11, the switch tube Q31, the switch tube Q32, the inductor L3 in turn, and finally flows back to the inductor L1 through the turned-on switches Kb1 and Kb2. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q13 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0071] In some feasible implementations, the above Fig.11 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the fourth switch tube in the first bridge arm to be turned on periodically, and control the first switch tube in the second bridge arm to be turned on periodically, and the second switch tube in the second bridge arm and the third switch tube in the first bridge arm to remain turned on. Please also refer to Fig.14 , Fig.14 is another schematic diagram of the structure of the power converter provided by the present application. Fig.14As shown, after the output ends of the bridge arm 1 and the bridge arm 3 are short-circuited, the controller controls the switch tube Q14 in the bridge arm 1 to be turned on periodically, and controls the switch tube Q31 in the bridge arm 3 to be turned on periodically, and controls the switch tube Q13 in the bridge arm 1 and the switch tube Q32 in the bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q31, the switch tube Q32 and the inductor L3 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally passes through the inductor L1, the switch tube Q13, and the switch tube Q14 in sequence to flow to the negative DC bus BUS-. Here, if the switch tubes and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 and the inductor L3 connected to the bridge arm 3 can draw power from the capacitor C1 and the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0072] Optional, see again Fig.14 After the current loop is formed in the power converter, the controller controls the switch tube Q14 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the switch tube Q13, the diode D12, the diode D31, the switch tube Q32 and the inductor L3 in sequence, and finally flows back to the inductor L1 through the turned-on switches Kb1 and Kb2. Here, if the switch tube, diode and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q11 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0073] In some feasible implementations, in the above power converter, each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series in sequence, and the series connection point of the first switch tube and the second switch tube is connected to the series connection point of the third switch tube and the fourth switch tube through the fifth switch tube and the sixth switch tube connected in series, the series connection point of the fifth switch tube and the sixth switch tube connected in series is connected to the series connection point of the first capacitor and the second capacitor, and the series connection point of the second switch tube and the third switch tube in each bridge arm serves as the output end of each bridge arm. Taking the power converter including three bridge arms as an example, see Fig.15 , Fig.15is another schematic diagram of the structure of the power converter provided by the present application. Fig.15 As shown, Fig.15 The power converter may include capacitors C1 and C2 connected in series, and three bridge arms (bridge arm 1, bridge arm 2 and bridge arm 3), wherein bridge arm 1, bridge arm 2 and bridge arm 3 are ABC three-phase bridge arms respectively, and the above-mentioned bridge arm 1, bridge arm 2 and bridge arm 3 lead out three corresponding ports ABC respectively. The bridge arm 1 may include a series-connected switch tube Q11, a switch tube Q12, a switch tube Q13 and a switch tube Q14, which are connected in series in sequence and in parallel at both ends of the capacitor C1 and the capacitor C2. The series point of the switch tube Q11 and the switch tube Q12 is connected to the series point of the switch tube Q13 and the switch tube Q14 through two series-connected switch tubes (switch tube Q15 and switch tube Q16), the series point of the series switch tube Q15 and the switch tube Q16 is connected to the series point of the capacitor C1 and the capacitor C2, and the series point of the switch tube Q12 and the switch tube Q13 can be used as the output end of the bridge arm 1 to lead out the A-phase port. The bridge arm 2 may include switch tubes Q21, Q22, Q23, Q24, Q25, and Q26, and the bridge arm 3 may include switch tubes Q31, Q32, Q33, Q34, Q35, and Q36. It can be understood that Fig.15 In the power converter shown, the circuit structures of the bridge arm 2 and the bridge arm 3 are the same as that of the bridge arm 1 described above, and will not be described in detail here.

[0074] Above Fig.15 In the power converter shown, the output ends of the two bridge arms are connected via a first switch, and the output end of each bridge arm is connected to an AC end of the power converter via an inductor, a third switch, and a second switch connected in series in sequence. Here, the connection method of the first switch can be as described above. Figures 7 to 10 The connection mode of the first switch in any power converter shown in Fig.10 Taking the connection mode of switch Ka1 in the power converter as an example, one end of switch Ka1 is connected to the series point of switch Kc1 and switch Kb1 connected to bridge arm 1, and the other end of switch Ka1 is connected to the series point of switch Kc2 and switch Kb2 connected to bridge arm 2. Similarly, one end of switch Ka2 is connected to the series point of switch Kc2 and switch Kb2 connected to bridge arm 2, and the other end of switch Ka2 is connected to the series point of switch Kc3 and switch Kb3 connected to bridge arm 3. It can be understood that each first switch in the power converter is not limited to Fig.11 For details on the connection method, please refer to the above Figures 7 to 10 The description of the medium power converter will not be repeated here.

[0075] In some feasible implementations, the above Fig.15In the power converter shown, when a double pulse test is performed on the power converter to detect a faulty bridge arm, taking the above-mentioned bridge arm 1 as the first bridge arm and bridge arm 3 as the second bridge arm as an example, the controller can first control switches Kb1, Kb2, Kb3, Kc1, Kc2 and Kc3 to be turned off, and then control switches Ka1, Kc1 and Kc2 to be turned on, so that the output ends of bridge arm 1 and bridge arm 3 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 3.

[0076] Further, the controller controls the electrical connection between the partially turned-on switch tubes in the first bridge arm and the partially turned-on switch tubes in the second bridge arm in at least two bridge arms to form a current loop. For example, the controller controls the first switch tube in the first bridge arm to be turned on periodically, and controls the fourth switch tube in the second bridge arm to be turned on periodically, and the third switch tube in the second bridge arm and the second switch tube in the first bridge arm to remain turned on. See again Fig.15 After the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q11 in bridge arm 1 to be turned on periodically, and controls the switch tube Q34 in bridge arm 3 to be turned on periodically, and controls the switch tube Q12 in bridge arm 1 and the switch tube Q33 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q11, the switch tube Q12 and the inductor L1 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally passes through the inductor L3, the switch tube Q33, and the switch tube Q34 in sequence to the negative DC bus BUS-. Here, if the switch tubes and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 and the inductor L3 connected to the bridge arm 3 can draw power from the capacitor C1 and the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0077] Optional, see again Fig.15After the current loop is formed in the power converter, the controller controls the switch tube Q11 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the turned-on switches Kb1 and Kb2, and then flows back to the inductor L1 through the inductor L3, the switch tube Q33, the switch tube Q36, the switch tube Q15 and the switch tube Q12 in sequence. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q11 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0078] In some feasible implementations, the above Fig.15 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the second switch tube in the first bridge arm to be turned on periodically, and control the third switch tube and the fourth switch tube in the second bridge arm to remain turned on. After the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q12 in bridge arm 1 to be turned on periodically, and controls the switch tubes Q33 and Q34 in bridge arm 3 to remain turned on. Here, the current loop formed in the power converter can refer to the above Fig.12 The current loop in will not be described in detail here.

[0079] Optionally, when the current on the inductor connected to the first bridge arm reaches a set threshold, the controller can also control some of the switches in the first bridge arm to turn off. If after controlling some of the switches in the first bridge arm to turn off, it is detected that the current on the inductor connected to the first bridge arm is simultaneously reduced to zero, an alarm signal is issued. After a current loop is formed in the power converter, the controller controls the switch tube Q12 to turn off and stop sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. The freewheeling loop formed in the power converter can be specifically referred to the above Fig.12 The freewheeling circuit in will not be described in detail here.

[0080] In some feasible implementations, the above Fig.15In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the third switch tube in the first bridge arm to be turned on periodically, and control the first switch tube and the second switch tube in the second bridge arm to remain turned on. After the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q13 in bridge arm 1 to be turned on periodically, and controls the switch tubes Q31 and Q32 in bridge arm 3 to remain turned on. Here, the current loop formed in the power converter can refer to the above Fig.13 The current loop in will not be described in detail here.

[0081] Optionally, when the current on the inductor connected to the first bridge arm reaches a set threshold, the controller can also control some of the switches in the first bridge arm to turn off. If after controlling some of the switches in the first bridge arm to turn off, it is detected that the current on the inductor connected to the first bridge arm is simultaneously reduced to zero, an alarm signal is issued. After a current loop is formed in the power converter, the controller controls the switch tube Q13 to turn off and stop sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. The freewheeling loop formed in the power converter can be specifically referred to the above Fig.13 The freewheeling circuit in will not be described in detail here.

[0082] In some feasible implementations, the above Fig.15 In the power converter shown, after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the fourth switch tube in the first bridge arm to be turned on periodically, and control the first switch tube in the second bridge arm to be turned on periodically, and control the second switch tube in the second bridge arm and the third switch tube in the first bridge arm to remain turned on. After the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q14 in bridge arm 1 to be turned on periodically, and controls the switch tube Q31 in bridge arm 3 to be turned on periodically, and controls the switch tube Q13 in bridge arm 1 and the switch tube Q32 in bridge arm 3 to remain turned on. Here, the current loop formed in the power converter can refer to the above Fig.14 The current loop in will not be described in detail here.

[0083] Optionally, when the current on the inductor connected to the first bridge arm reaches a set threshold, the controller can also control some of the switches in the first bridge arm to turn off. If after controlling some of the switches in the first bridge arm to turn off, it is detected that the current on the inductor connected to the first bridge arm is simultaneously reduced to zero, an alarm signal is issued. After a current loop is formed in the power converter, the controller controls the switch Q14 to turn off and stop sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. The freewheeling loop formed in the power converter can be specifically referred to the above Fig.14 The freewheeling circuit in will not be described in detail here.

[0084] In some feasible implementations, the above Fig.15 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the fifth switch tube in the first bridge arm to be turned on periodically, and control the first switch tube and the second switch tube in the second bridge arm to remain turned on. Fig.16 , Fig.16 is another schematic diagram of the structure of the power converter provided by the present application. Fig.16 As shown, after the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q15 in bridge arm 1 to be turned on periodically, and controls the switch tubes Q31 and Q32 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q31, the switch tube Q32, and the inductor L3 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally flows back to the bus midpoint through the inductor L1, the switch tube Q12, and the switch tube Q15. Here, if the switch tube and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 can draw power from the capacitor C1, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0085] Optional, see again Fig.16 After the current loop is formed in the power converter, the controller controls the switch tube Q15 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the switch tube Q12, the switch tube Q11, the switch tube Q31, the switch tube Q32, the inductor L3 in turn, and finally flows back to the inductor L1 through the turned-on switches Kb1 and Kb2. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q15 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0086] In some feasible implementations, the above Fig.15In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the sixth switch tube in the first bridge arm to be turned on periodically, and control the third switch tube and the fourth switch tube in the second bridge arm to remain turned on. Fig.17 , Fig.17 is another schematic diagram of the structure of the power converter provided by the present application. Fig.17 As shown, after the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q16 in bridge arm 1 to be turned on periodically, and controls the switch tubes Q33 and Q34 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the series connection point of capacitor C1 and capacitor C2 (or, it can be called the busbar midpoint), passes through the switch tube Q16, the switch tube Q13, and the inductor L1 in sequence, then passes through the turned-on switch Kb1 and switch Kb2, and finally flows back to the capacitor C2 through the inductor L3, the switch tube Q33, and the switch tube Q34 in sequence. Here, if the switch tube and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 can draw power from the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0087] Optional, see again Fig.17 After the current loop is formed in the power converter, the controller controls the switch tube Q16 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the turned-on switches Kb1 and Kb2, and then flows back to the inductor L1 through the inductor L3, the switch tube Q33, the switch tube Q34, the switch tube Q14 and the switch tube Q13 in sequence. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q16 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0088] In some feasible embodiments, in the above-mentioned power converter, each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, the first switch tube and the fourth switch tube are connected in series, and the series point of the first switch tube and the fourth switch tube is connected to the series point of the first capacitor and the second capacitor through the second switch tube and the third switch tube connected in reverse series, and the series point of the first switch tube and the fourth switch tube in each bridge arm serves as the output end of each bridge arm.

[0089] Take the power converter including three bridge arms as an example, see Fig.18 , Fig.18 is another schematic diagram of the structure of the power converter provided by the present application. Fig.18 As shown, Fig.18 The power converter in the embodiment may include a capacitor C1 and a capacitor C2 connected in series, and three bridge arms (bridge arm 1, bridge arm 2 and bridge arm 3), wherein bridge arm 1, bridge arm 2 and bridge arm 3 are three-phase bridge arms ABC respectively, and the above-mentioned bridge arm 1, bridge arm 2 and bridge arm 3 lead out three corresponding ports ABC respectively. Bridge arm 1 may include two first bridge arm switch tubes and second bridge arm switch tubes connected in series (for convenience of description, they may be represented as switch tubes Q11 and switch tubes Q12), switch tubes Q11 and switch tubes Q12 may be connected in parallel to both ends of the capacitor C1 and capacitor C2 connected in series in the power converter, the series connection point of switch tubes Q11 and switch tubes Q12 may lead out the A phase port, and the series connection point of switch tubes Q11 and switch tubes Q12 may be connected to the series connection point of capacitor C1 and capacitor C2 through the third bridge arm switch tube and the fourth bridge arm switch tube connected in reverse series (for convenience of description, they may be represented as switch tubes Q13 and switch tubes Q14). The bridge arm 2 may include a switch tube Q21, a switch tube Q22, a switch tube Q23 and a switch tube Q24, and the bridge arm 3 may include a switch tube Q31, a switch tube Q32, a switch tube Q33 and a switch tube Q34. It can be understood that Fig.18 In the power converter shown, the circuit structures of the bridge arm 2 and the bridge arm 3 are the same as that of the bridge arm 1 described above, and will not be described in detail here.

[0090] Above Fig.18 In the power converter shown, the output ends of the two bridge arms are connected via a first switch, and the output end of each bridge arm is connected to an AC end of the power converter via an inductor, a third switch, and a second switch connected in series in sequence. Here, the connection method of the first switch can be as described above. Figures 7 to 10 The connection mode of the first switch in any power converter shown in Fig.10Taking the connection mode of switch Ka1 in the power converter as an example, one end of switch Ka1 is connected to the series point of switch Kc1 and switch Kb1 connected to bridge arm 1, and the other end of switch Ka1 is connected to the series point of switch Kc2 and switch Kb2 connected to bridge arm 2. Similarly, one end of switch Ka2 is connected to the series point of switch Kc2 and switch Kb2 connected to bridge arm 2, and the other end of switch Ka2 is connected to the series point of switch Kc3 and switch Kb3 connected to bridge arm 3. It can be understood that each first switch in the power converter is not limited to Fig.11 For details on the connection method, please refer to the above Figures 7 to 10 The description of the medium power converter will not be repeated here.

[0091] In some feasible implementations, the above Fig.18 In the power converter shown, when a double pulse test is performed on the power converter to detect a faulty bridge arm, taking the above-mentioned bridge arm 1 as the first bridge arm and bridge arm 3 as the second bridge arm as an example, the controller can first control switches Kb1, Kb2, Kb3, Kc1, Kc2 and Kc3 to be turned off, and then control switches Ka1, Kc1 and Kc2 to be turned on, so that the output ends of bridge arm 1 and bridge arm 3 are short-circuited, and current can be conducted between bridge arm 1 and bridge arm 3.

[0092] Further, the controller controls the electrical connection between the partially turned-on switch tubes in the first bridge arm and the partially turned-on switch tubes in the second bridge arm in at least two bridge arms to form a current loop. For example, the controller controls the first switch tube in the first bridge arm to be turned on periodically, and controls the fourth switch tube in the second bridge arm to be turned on periodically, and the third switch tube in the second bridge arm and the second switch tube in the first bridge arm to remain turned on. See again Fig.18 After the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q11 in bridge arm 1 to be turned on periodically, and controls the switch tube Q34 in bridge arm 3 to be turned on periodically, and controls the switch tube Q12 in bridge arm 1 and the switch tube Q33 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q11 and the inductor L1 in sequence, then passes through the turned-on switch Kb1 and switch Kb2, and finally passes through the inductor L3 and the switch tube Q34 in sequence to the negative DC bus BUS-. Here, if the switch tubes and other devices on the current loop are normal, the inductor L1 connected to bridge arm 1 and the inductor L3 connected to bridge arm 3 can draw power from the capacitor C1 and the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0093] Optional, see again Fig.18 After the current loop is formed in the power converter, the controller controls the switch tube Q11 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the turned-on switches Kb1 and Kb2, and then flows back to the inductor L1 through the inductor L3, the switch tube Q32, the switch tube Q33, the switch tube Q13 and the switch tube Q12 in sequence. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q11 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0094] In some feasible implementations, the above Fig.18 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the second switch tube in the first bridge arm to be periodically turned on, and control the fourth switch tube in the second bridge arm to remain turned on. Fig.19 , Fig.19 is another schematic diagram of the structure of the power converter provided by the present application. Fig.19 As shown, after the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q12 in bridge arm 1 to be turned on periodically, and controls the switch tube Q34 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the series connection point of capacitor C1 and capacitor C2 (or, it can be called the busbar midpoint), passes through the switch tube Q13, the switch tube Q12, and the inductor L1 in sequence, and then passes through the turned-on switch Kb1 and switch Kb2, and finally flows back to the capacitor C2 through the inductor L3 and the switch tube Q34 in sequence. Here, if the switch tube and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 can draw power from the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0095] Optional, see again Fig.19After the current loop is formed in the power converter, the controller controls the switch tube Q12 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the turned-on switches Kb1 and Kb2, and then flows back to the inductor L1 through the inductor L3, the switch tube Q34 and the switch tube Q14 in sequence. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q12 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0096] In some feasible implementations, the above Fig.18 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the third switch tube in the first bridge arm to be periodically turned on, and control the first switch tube in the second bridge arm to remain turned on. Fig. 20 , Fig. 20 is another schematic diagram of the structure of the power converter provided by the present application. Fig. 20 As shown, after the output ends of bridge arm 1 and bridge arm 3 are short-circuited, the controller controls the switch tube Q13 in bridge arm 1 to be turned on periodically, and controls the switch tube Q31 in bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q11, the switch tube Q31, the inductor L3 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally flows back to the bus midpoint through the inductor L1, the switch tube Q12 and the switch tube Q13. Here, if the switch tube and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 can draw power from the capacitor C1, and the current value on the inductor L1 can be detected to increase. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, the switch tube and other devices on the current loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault occurs.

[0097] Optional, see again Fig. 20After the current loop is formed in the power converter, the controller controls the switch tube Q13 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the switch tube Q11, the switch tube Q31, the inductor L3 in turn, and finally flows back to the inductor L1 through the turned-on switches Kb1 and Kb2. Here, if the switch tube and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q13 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

[0098] In some feasible implementations, the above Fig.18 In the power converter shown in FIG. 1 , after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, the controller can also control the fourth switch tube in the first bridge arm to be turned on periodically, and control the first switch tube in the second bridge arm to be turned on periodically, and the second switch tube in the second bridge arm and the third switch tube in the first bridge arm to remain turned on. Please also refer to Fig.21 , Fig.21 is another schematic diagram of the structure of the power converter provided by the present application. Fig.21 As shown, after the output ends of the bridge arm 1 and the bridge arm 3 are short-circuited, the controller controls the switch tube Q14 in the bridge arm 1 to be turned on periodically, and controls the switch tube Q31 in the bridge arm 3 to be turned on periodically, and controls the switch tube Q13 in the bridge arm 1 and the switch tube Q32 in the bridge arm 3 to remain turned on. At this time, a current loop is formed in the power converter. Specifically, the current loop path flows out from the positive DC bus BUS+, passes through the switch tube Q31 and the inductor L3 in sequence, then passes through the turned-on switch Kb1 and the switch Kb2, and finally passes through the inductor L1 and the switch tube Q14 in sequence to the negative DC bus BUS-. Here, if the switch tubes and other devices on the current loop are normal, the inductor L1 connected to the bridge arm 1 and the inductor L3 connected to the bridge arm 3 can draw power from the capacitor C1 and the capacitor C2, and the current value on the inductor L1 can be detected to be increased. Otherwise, if it is detected that the current value on the inductor L1 is unchanged, or the current value on the inductor L1 is less than or equal to the set threshold, there is a fault in the switching tube and other devices in the current loop, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt the power converter that a bridge arm fault has occurred.

[0099] Optional, see again Fig.21After the current loop is formed in the power converter, the controller controls the switch tube Q14 to turn off and then stops sending the pulse drive waveform. At this time, a freewheeling loop is formed in the power converter due to the discharge of the inductor L1. Specifically, the freewheeling loop flows out from the inductor L1, passes through the switch tube Q12, the switch tube Q13, the switch tube Q33, the switch tube Q32 and the inductor L3 in sequence, and finally flows back to the inductor L1 through the turned-on switches Kb1 and Kb2. Here, if the switch tube, diode and other devices on the freewheeling loop are normal, the inductor L1 connected to the bridge arm 1 is slowly discharged through the freewheeling loop, and it can be detected that the current value on the inductor L1 is gradually reduced. Otherwise, if after controlling the above-mentioned switch tube Q11 to turn off, it is detected that the current value on the inductor L1 is reduced to zero at the same time, then the switch tube and other devices on the freewheeling loop are faulty, and the above-mentioned bridge arm 1 or bridge arm 3 is faulty, then the controller sends an alarm signal to prompt that the power converter has a bridge arm fault.

Claims

1. A power converter, characterized in that: The power converter comprises at least two bridge arms, a first switch and a controller; The bridge arm includes an output end and a plurality of switch tubes, and the turning on and off of the plurality of switch tubes is used to convert direct current from a photovoltaic module or an energy storage battery into alternating current and output the alternating current through the output end; The first switch is connected in series between output ends of any two bridge arms of the at least two bridge arms; The controller is used to control the closing of the first switch to achieve electrical connection between the partially conductive switch tube on the first bridge arm and the partially conductive switch tube on the second bridge arm of the at least two bridge arms and form a current loop. When the current value of the current loop is less than or equal to a set threshold, the controller sends an alarm signal.

2. The power converter according to claim 1, characterized in that: The power converter further comprises a second switch, which is connected to the output ends of the at least two bridge arms and is used to connect to a power grid or a load; The controller is further configured to, before controlling the formation of the current loop, first control the second switch to be opened, and then control the first switch to be closed.

3. The power converter according to claim 1 or 2, characterized in that: The power converter further includes an inductor, which is connected in series between the first switch and the output end of the bridge arm; After the power converter forms a current loop and the current value of the current loop is greater than the set threshold, the controller is also used to continue to control the first switch to close, so as to achieve electrical connection between the partially conductive switch tube in the first bridge arm and the partially conductive switch tube in the second bridge arm of the at least two bridge arms and form a freewheeling loop of the inductor, wherein the freewheeling loop and the current loop include at least partially different switch tubes, and if the freewheeling loop is not established, the controller sends an alarm signal.

4. The power converter according to any one of claims 1 to 3, characterized in that: The power converter further comprises a bus capacitor which is connected in series in the current loop and is used to provide electrical energy for the current loop.

5. The power converter according to claim 4, characterized in that: The bus capacitor includes a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus; The at least two bridge arms are connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and each of the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series in sequence, and the series point of the first switch tube and the second switch tube is connected to the series point of the third switch tube and the fourth switch tube through two diodes connected in series, and the series point of the two diodes in series is connected to the series point of the first capacitor and the second capacitor, and the series point of the second switch tube and the third switch tube in each bridge arm serves as the output end of each bridge arm.

6. The power converter according to claim 4, characterized in that: The bus capacitor includes a first capacitor and a second capacitor connected in series, the first capacitor is connected to the positive DC bus, and the second capacitor is connected to the negative DC bus; The at least two bridge arms are connected in parallel at both ends of the first capacitor and the second capacitor connected in series, and each bridge arm in the at least two bridge arms includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube connected in series in sequence, and the series point of the first switch tube and the second switch tube is connected to the series point of the third switch tube and the fourth switch tube through the fifth switch tube and the sixth switch tube connected in series, the series point of the fifth switch tube and the sixth switch tube in series is connected to the series point of the first capacitor and the second capacitor, and the series point of the second switch tube and the third switch tube in each bridge arm serves as the output end of each bridge arm.

7. The power converter according to claim 5 or 6, characterized in that: The controller is also used to, after controlling the first switch between the output end of the first bridge arm and the output end of the second bridge arm to close, control the first switch tube in the first bridge arm to be periodically turned on, and control the fourth switch tube in the second bridge arm to be periodically turned on, and control the third switch tube in the second bridge arm and the second switch tube in the first bridge arm to remain turned on to form the current loop.

8. The power converter according to any one of claims 3 to 7, characterized in that: The power converter further includes a third switch, wherein the third switch is connected in series between the second switch and the inductor; When the output ends of two bridge arms of the at least two bridge arms are connected through the first switch, one end of the first switch is connected to the series point of the inductor connected to the output end of one bridge arm and the third switch, and the other end of the first switch is connected to the series point of the inductor connected to the output end of the other bridge arm and the third switch.

9. The power converter according to any one of claims 3 to 7, characterized in that: The power converter further includes a third switch, wherein the third switch is connected in series between the second switch and the inductor; When the output ends of two bridge arms of the at least two bridge arms are connected through the first switch, one end of the first switch is connected to the series point of the inductor connected to the output end of one bridge arm and the third switch, and the other end of the first switch is connected to the series point of the second switch connected to the output end of the other bridge arm and the third switch.

10. The power converter according to any one of claims 3 to 7, characterized in that: The power converter further includes a third switch, wherein the third switch is connected in series between the second switch and the inductor; When the output ends of two bridge arms of the at least two bridge arms are connected through a first switch, one end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of one bridge arm, and the other end of the first switch is connected to the series point of the second switch and the third switch connected to the output end of another bridge arm.

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