Three-level bridge arm circuit power device on-state voltage measuring circuit and method

Abstract

The invention provides a three-level bridge arm circuit power device on-state voltage measuring circuit and method. The circuit comprises a first on-state voltage measuring circuit and a second on-state voltage measuring circuit, wherein the first on-state voltage measuring circuit comprises a first input port, a second input port and a third input port; the second on-state voltage measuring circuit comprises a fourth input port, a fifth input port and a sixth input port; the first input port is electrically connected with the first end of the first power device, the second input port is electrically connected with the second end of the first power device and the first end of the second power device, and the third input port is electrically connected with the second end of the second power device; the fourth input port is electrically connected with the first end of the third power device, the fifth input port is electrically connected with the second end of the third power device and the first end of the fourth power device, and the sixth input port is electrically connected with the second end of the fourth power device; according to the invention, the on-state voltage of the power device of the three-level bridge arm circuit is detected in real time through a simple circuit structure, and the accuracy of on-state voltage measurement is improved.

Description

Technical Field

[0001] The present invention relates to the field of monitoring the health parameters of inverter-level power devices, and particularly to a conduction voltage measurement circuit and method for power devices in a three-level bridge arm circuit. Background Art

[0002] The development of power electronic devices and new energy technologies has promoted the wide application of multilevel circuit topologies in fields such as new energy technologies and motor drives, which benefits from their advantages such as high efficiency, low switching losses, and good power quality. The health status of power devices (such as IGBTs and MOSFETs) is crucial for the reliable operation of power electronic systems, and their health status and operational reliability have become the focus of research; among them, the junction temperature of power devices is a key parameter for evaluating their health status, and the on-state voltage drop of the device (such as V ce ) of IGBT) is the core basis for realizing junction temperature monitoring, life prediction, and loss calculation. With the development of power converters towards high frequency, high power, and high density, the monitoring of on-state voltage drop needs to meet requirements such as linearity, safety, and accuracy.

[0003] Currently, the existing methods for monitoring on-state voltage drop are mainly divided into two types: offline and online. Offline monitoring measures the change in the on-state voltage drop of the device when the converter is in a non-operating state; online monitoring needs to capture the change in its on-state voltage drop when the converter is operating normally; however, due to the need to equip each power device with an independent isolated power supply and a sampling opto-isolator or adopt a one-to-one measurement mode in the traditional on-state voltage measurement circuit, the complex circuit structure of the existing technology is limited to offline measurement and single power transistor measurement, resulting in a problem of poor accuracy in on-state voltage measurement. Summary of the Invention

[0004] In order to solve the above problems, the present invention proposes a conduction voltage measurement circuit and method for power devices in a three-level bridge arm circuit, which can realize real-time detection of the conduction voltage of power devices in a three-level bridge arm circuit with a simple circuit structure and improve the accuracy of on-state voltage measurement.

[0005] To achieve the above object, an embodiment of the present invention provides a conduction voltage measurement circuit for power devices in a three-level bridge arm circuit, which is applied to a three-level bridge arm circuit. The three-level bridge arm circuit includes: a first power device, a second power device, a third power device, and a fourth power device. The first power device, the second power device, the third power device, and the fourth power device are connected in series. The conduction voltage measurement circuit for power devices in the three-level bridge arm circuit includes: a first conduction voltage measurement circuit and a second conduction voltage measurement circuit; the first conduction voltage measurement circuit includes: a first input port, a second input port, a third input port, a first output port, a second output port, and a third output port; the second conduction voltage measurement circuit includes: a fourth input port, a fifth input port, a sixth input port, a fourth output port, a fifth output port, and a sixth output port; the first input port is electrically connected to the first end of the first power device, the second input port is electrically connected to the second end of the first power device, the second input port is also electrically connected to the first end of the second power device, and the third input port is electrically connected to the second end of the second power device; the fourth input port is electrically connected to the first end of the third power device, the fifth input port is electrically connected to the second end of the third power device, the fifth input port is also electrically connected to the first end of the fourth power device, and the sixth input port is electrically connected to the second end of the fourth power device; a first voltage value is output between the first output port and the third output port, a second voltage value is output between the second output port and the third output port, a third voltage value is output between the fourth output port and the fifth output port, and a fourth voltage value is output between the fourth output port and the sixth output port; both the first conduction voltage measurement circuit and the second conduction voltage measurement circuit are composed of several diodes.

[0006] An embodiment of the present invention proposes a conduction voltage measurement circuit for power devices in a three-level bridge arm circuit. By connecting each input port of the first conduction voltage measurement circuit and the second conduction voltage measurement circuit of the conduction voltage measurement circuit for power devices in the three-level bridge arm circuit to each power device in the three-level bridge arm circuit, the conduction relationship of each input port of the first conduction voltage measurement circuit and the second conduction voltage measurement circuit can be affected according to the conduction relationship of each power device in the three-level bridge arm circuit, thereby realizing the detection of the conduction voltage of each power device in the three-level bridge arm circuit, and outputting corresponding voltage values from each output port of the first conduction voltage measurement circuit and the second conduction voltage measurement circuit. According to the corresponding voltage values, the conduction voltage of each power device can be obtained, and both the first conduction voltage measurement circuit and the second conduction voltage measurement circuit are composed of several diodes. Thus, combined with the conduction relationship of each power device in the three-level bridge arm circuit, the conduction voltage of the power devices in the three-level bridge arm circuit can be detected in real time with a simple circuit structure, and the accuracy of conduction voltage measurement can be improved.

[0007] Further, the first on-state voltage measurement circuit includes: a first diode, a second diode, a third diode, a fourth diode, a first voltage stabilizing diode, a second voltage stabilizing diode, and a first isolated power supply; the negative electrode of the first diode is electrically connected to the first input port, the positive electrode of the first diode is electrically connected to the negative electrode of the second diode, and the positive electrode of the second diode is electrically connected to the positive electrode of the first isolated power supply; the negative electrode of the third diode is electrically connected to the second input port, the positive electrode of the third diode is electrically connected to the negative electrode of the fourth diode, and the positive electrode of the fourth diode is electrically connected to the positive electrode of the first isolated power supply; the positive electrode of the first voltage stabilizing diode is electrically connected to the third output port, the positive electrode of the first voltage stabilizing diode is electrically connected to the negative electrode of the first isolated power supply, the negative electrode of the first voltage stabilizing diode is electrically connected to the positive electrode of the first diode, and the negative electrode of the first voltage stabilizing diode is electrically connected to the negative electrode of the second diode; the positive electrode of the second voltage stabilizing diode is electrically connected to the third output port, the positive electrode of the second voltage stabilizing diode is electrically connected to the negative electrode of the first isolated power supply, the negative electrode of the second voltage stabilizing diode is electrically connected to the positive electrode of the third diode, and the negative electrode of the second voltage stabilizing diode is electrically connected to the negative electrode of the fourth diode.

[0008] In the above solution, the first diode and the third diode are respectively connected to the first input port and the second input port. Thus, the conduction relationship between the first diode and the third diode can be affected according to the conduction relationship between the first power device and the second power device, and the conduction relationship between the first diode and the third diode will form different on-state voltage detection circuits, thereby realizing the real-time detection of the on-state voltage of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the measurement accuracy of the on-state voltage.

[0009] Further, the first on-state voltage measurement circuit includes: a first operational amplifier and a second operational amplifier; the non-inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the first diode, the non-inverting input terminal of the first operational amplifier is electrically connected to the negative electrode of the second diode, the non-inverting input terminal of the first operational amplifier is electrically connected to the negative electrode of the first voltage stabilizing diode, the inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the second diode, the inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the fourth diode, the inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the first isolated power supply, and the output terminal of the first operational amplifier is electrically connected to the first output port; the negative electrode of the first isolated power supply is electrically connected to the third output port; the positive electrode of the first voltage stabilizing diode is electrically connected to the third output port; the non-inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the third diode, the non-inverting input terminal of the second operational amplifier is electrically connected to the negative electrode of the fourth diode, the non-inverting input terminal of the second operational amplifier is electrically connected to the negative electrode of the second voltage stabilizing diode, the inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the second diode, the inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the fourth diode, the inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the first isolated power supply, and the output terminal of the second operational amplifier is electrically connected to the second output port; the positive electrode of the second voltage stabilizing diode is electrically connected to the third output port.

[0010] In the above solution, the first operational amplifier and the second operational amplifier are arranged to be connected to each diode, and then the output terminals of the first operational amplifier and the second operational amplifier are connected to the first output port and the second output port. After different on-state voltage detection circuits are formed according to the conduction relationship between the first diode and the third diode, the corresponding first voltage value and second voltage value are output from the first output port, the second output port and the third output port. According to the corresponding first voltage value and second voltage value, the on-state voltages of the first power device and the second power device can be obtained, thereby realizing the real-time detection of the on-state voltages of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the measurement accuracy of the on-state voltage.

[0011] Further, the second on-state voltage measurement circuit includes: a fifth diode, a sixth diode, a seventh diode, an eighth diode, a third voltage regulator diode, a fourth voltage regulator diode, and a second isolated power supply; the anode of the fifth diode is electrically connected to the sixth input port, the cathode of the fifth diode is electrically connected to the anode of the sixth diode, and the cathode of the sixth diode is electrically connected to the negative pole of the second isolated power supply; the anode of the seventh diode is electrically connected to the fifth input port, the cathode of the seventh diode is electrically connected to the anode of the eighth diode, and the cathode of the eighth diode is electrically connected to the negative pole of the second isolated power supply; the cathode of the third voltage regulator diode is electrically connected to the fourth input interface, the anode of the third voltage regulator diode is electrically connected to the cathode of the seventh diode, and the anode of the third voltage regulator diode is electrically connected to the anode of the eighth diode; the cathode of the fourth voltage regulator diode is electrically connected to the fourth input interface, the anode of the fourth voltage regulator diode is electrically connected to the cathode of the fifth diode, and the anode of the fourth voltage regulator diode is electrically connected to the anode of the sixth diode.

[0012] In the above solution, the fifth diode and the seventh diode are respectively connected to the sixth input port and the fifth input port. Thus, the on-state relationship of the fifth diode and the seventh diode can be affected according to the on-state relationship of the third power device and the fourth power device. The on-state relationship of the fifth diode and the seventh diode will form different on-state voltage detection circuits, thereby realizing the real-time detection of the on-state voltage of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the accuracy of on-state voltage measurement.

[0013] Further, the second on-state voltage measurement circuit includes: a third operational amplifier and a fourth operational amplifier; the non-inverting input terminal of the third operational amplifier is electrically connected to the cathode of the seventh diode, the non-inverting input terminal of the third operational amplifier is electrically connected to the anode of the eighth diode, the non-inverting input terminal of the third operational amplifier is electrically connected to the anode of the third voltage regulator diode, the inverting input terminal of the third operational amplifier is electrically connected to the cathode of the sixth diode, the inverting input terminal of the third operational amplifier is electrically connected to the cathode of the eighth diode, the inverting input terminal of the third operational amplifier is electrically connected to the negative pole of the second isolated power supply, and the output terminal of the third operational amplifier is electrically connected to the fifth output port; the positive pole of the second isolated power supply is electrically connected to the fourth output port; the cathode of the third voltage regulator diode is electrically connected to the fourth output port; the non-inverting input terminal of the fourth operational amplifier is electrically connected to the cathode of the fifth diode, the non-inverting input terminal of the fourth operational amplifier is electrically connected to the anode of the sixth diode, the non-inverting input terminal of the fourth operational amplifier is electrically connected to the anode of the fourth voltage regulator diode, the inverting input terminal of the fourth operational amplifier is electrically connected to the cathode of the sixth diode, the inverting input terminal of the fourth operational amplifier is electrically connected to the cathode of the eighth diode, the inverting input terminal of the fourth operational amplifier is electrically connected to the negative pole of the second isolated power supply, and the output terminal of the fourth operational amplifier is electrically connected to the sixth output port; the cathode of the fourth voltage regulator diode is electrically connected to the fourth output port.

[0014] In the above solution, a third operational amplifier and a fourth operational amplifier are connected to each diode, and then the output terminals of the third operational amplifier and the fourth operational amplifier are connected to a fifth output port and a sixth output port. After different on-state voltage detection circuits are formed according to the conduction relationship between the fifth diode and the seventh diode, corresponding third voltage values and fourth voltage values are output from the fourth output port, the fifth output port and the sixth output port. Based on the corresponding third voltage values and fourth voltage values, the on-state voltages of the third power device and the fourth power device can be obtained, thereby realizing the real-time detection of the on-state voltages of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the accuracy of on-state voltage measurement.

[0015] Furthermore, the first on-state voltage measurement circuit and the second on-state voltage measurement circuit are set as symmetrical circuits.

[0016] In the above solution, the first on-state voltage measurement circuit and the second on-state voltage measurement circuit are set as symmetrical circuits, so that the working principles of the first on-state voltage measurement circuit and the second on-state voltage measurement circuit are the same. Then, the on-state voltages of each power device can be detected by using the same two-device connection, and the circuit structure can be simplified to reduce the circuit cost. The on-state voltages of the power devices in the three-level bridge arm circuit can be detected in real time with a simple circuit structure, and the accuracy of on-state voltage measurement can be improved.

[0017] The embodiment of the present invention also provides a method for measuring the on-state voltage of a power device in a three-level bridge arm circuit, including: controlling the conduction and turn-off of each power device in the three-level bridge arm circuit based on a preset modulation strategy to obtain the conduction states of each power device in the three-level bridge arm circuit; controlling the conduction and turn-off of each input port of the on-state voltage measurement circuit of the power device in the three-level bridge arm circuit based on the conduction states of each power device in the three-level bridge arm circuit to obtain the corresponding voltage values output from each output port; and obtaining the measurement result of the on-state voltage of the power device in the three-level bridge arm circuit based on the corresponding voltage values output from each output port.

[0018] An embodiment of the present invention provides a method for measuring the on-state voltage of power devices in a three-level bridge arm circuit. By connecting each input port of the first on-state voltage measurement circuit and the second on-state voltage measurement circuit of the three-level bridge arm circuit power device on-state voltage measurement circuit to each power device in the three-level bridge arm circuit, the on-state relationship of each input port of the first on-state voltage measurement circuit and the second on-state voltage measurement circuit can be affected according to the conduction relationship of each power device in the three-level bridge arm circuit, thereby realizing the detection of the on-state voltage of each power device in the three-level bridge arm circuit, and outputting the corresponding voltage values from each output port of the first on-state voltage measurement circuit and the second on-state voltage measurement circuit. According to the corresponding voltage values, the on-state voltage of each power device can be obtained. Moreover, both the first on-state voltage measurement circuit and the second on-state voltage measurement circuit are composed of several diodes. Thus, in combination with the conduction relationship of each power device in the three-level bridge arm circuit, the on-state voltage of the power devices in the three-level bridge arm circuit can be detected in real time with a simple circuit structure, improving the accuracy of on-state voltage measurement.

[0019] Further, based on the conduction states of each power device in the three-level bridge arm circuit, controlling the conduction and cut-off of each input port of the three-level bridge arm circuit power device on-state voltage measurement circuit to obtain the corresponding voltage values output from each output port, including: if each power device in the three-level bridge arm circuit is in a positive voltage state, both the first power device and the second power device are conducting; if both the first power device and the second power device are conducting, the first input port, the second input port, and the third input port of the three-level bridge arm circuit power device on-state voltage measurement circuit are all conducting; if the first input port, the second input port, and the third input port of the three-level bridge arm circuit power device on-state voltage measurement circuit are all conducting, the difference between the first voltage value and the second voltage value is used as the on-state voltage of the first power device, and the second voltage value is used as the on-state voltage of the second power device.

[0020] In the above solution, when each power device in the three-level bridge arm circuit is in a positive voltage state, both the first power device and the second power device are conducting. At this time, the first input port, the second input port, and the third input port are conducting. Then, according to the connection relationship and conduction relationship of the first on-state voltage measurement circuit, the on-state voltages of the first power device and the second power device are detected, and the corresponding voltage values are output from the first output port, the second output port, and the third output port as the on-state voltages of the first power device and the second power device, realizing the real-time detection of the on-state voltage of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the accuracy of on-state voltage measurement.

[0021] Further, based on the conduction states of the power devices in the three-level bridge arm circuit, control the conduction and cutoff of each input port of the conduction state voltage measurement circuit of the power devices in the three-level bridge arm circuit to obtain the corresponding voltage values output from each output port, including: if the power devices in the three-level bridge arm circuit are in the negative voltage state, both the third power device and the fourth power device are conducting; if both the third power device and the fourth power device are conducting, the fourth input port, the fifth input port, and the sixth input port of the conduction state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all conducting; if the fourth input port, the fifth input port, and the sixth input port of the conduction state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all conducting, the difference between the third voltage value and the fourth voltage value is used as the conduction state voltage of the third power device, and the third voltage value is used as the conduction state voltage of the fourth power device.

[0022] In the above solution, when the power devices in the three-level bridge arm circuit are in the negative voltage state, both the third power device and the fourth power device are conducting. At this time, the fourth input port, the fifth input port, and the sixth input port are conducting. Then, based on the connection relationship and conduction relationship of the second conduction state voltage measurement circuit, the conduction state voltages of the third power device and the fourth power device are detected, and the corresponding voltage values output from the fourth output port, the fifth output port, and the sixth output port are used as the conduction state voltages of the third power device and the fourth power device, realizing real-time detection of the conduction state voltages of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the accuracy of conduction state voltage measurement.

[0023] Further, based on the conduction states of the power devices in the three-level bridge arm circuit, control the conduction and cutoff of each input port of the conduction state voltage measurement circuit of the power devices in the three-level bridge arm circuit to obtain the corresponding voltage values output from each output port, including: if the power devices in the three-level bridge arm circuit are in the 0 state, both the second power device and the third power device are conducting; if both the second power device and the third power device are conducting, the second input port, the third input port, the fourth input port, and the fifth input port of the conduction state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all conducting; if the second input port, the third input port, the fourth input port, and the fifth input port of the conduction state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all conducting, the second voltage value is used as the conduction state voltage of the second power device, and the third voltage value is used as the conduction state voltage of the fourth power device.

[0024] In the above solution, when all the power devices in the three-level bridge arm circuit are in the 0 state, only the second and third power devices are conducting. At this time, the first input port and the sixth input port are turned off. According to the connection relationship and conduction relationship of the first on-state voltage measurement circuit and the second on-state voltage measurement circuit, the on-state voltages of the second and third power devices are detected, and the corresponding voltage values are output from the second output port, the third output port, the fourth output port, and the fifth output port as the on-state voltages of the second and third power devices. Thus, the on-state voltages of the power devices in the three-level bridge arm circuit can be detected in real time with a simple circuit structure, improving the measurement accuracy of the on-state voltage. Description of the Drawings

[0025] Figure 1 Structural schematic diagram of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention Figure 1 ;

[0026] Figure 2 Structural schematic diagram of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention Figure 2 ;

[0027] Figure 3 Structural schematic diagram of the P state of the three-level bridge arm circuit of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0028] Figure 4 Structural schematic diagram of the N state of the three-level bridge arm circuit of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0029] Figure 5 Structural schematic diagram of the 0 state of the three-level bridge arm circuit of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0030] Figure 6 Schematic diagram of the SPWM carrier overlapping modulation waveform of the three-level bridge arm circuit of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0031] Figure 7 Schematic diagram of the logic for generating the driving signal of the switch tube of phase A of the three-level bridge arm circuit of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0032] Figure 8 Structural schematic diagram of the three-level three-phase main circuit of a circuit for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0033] Figure 9 Schematic diagram of the step flow of a method for measuring the on-state voltage of a power device in a three-level bridge arm circuit provided by an embodiment of the present invention;

[0034] Reference numerals: 1, first power device; 2, second power device; 3, third power device; 4, fourth power device; 5, first on-state voltage measurement circuit; 6, second on-state voltage measurement circuit; 51, first input port; 52, second input port; 53, third input port; 54, first output port; 55, second output port; 56, third output port; 61, fourth input port; 62, fifth input port; 63, sixth input port; 64, fourth output port; 65, fifth output port; 66, sixth output port; D1, first diode; D2, second diode; D3, third diode; D31, third diode of phase A; D32, third diode of phase B; D33, third diode of phase C; D4, fourth diode;

[0035] Z1, first zener diode; Z2, second zener diode; V P1 , first isolated power supply; OA1, first operational amplifier; OA2, second operational amplifier; D5, fifth diode; D6, sixth diode; D7, seventh diode; D71, seventh diode of phase A; D72, seventh diode of phase B; D73, seventh diode of phase C; D8, eighth diode; Z3, third zener diode; Z4, fourth zener diode; V P2 , second isolated power supply; OA3, third operational amplifier; OA4, fourth operational amplifier; U dc , DC power supply; C1, first capacitor; C2, second capacitor; D a1 , first protection diode; D a2 , second protection diode; D a3 , third protection diode; D a4 , fourth protection diode; D a5 , fifth protection diode of phase A; D a6 , sixth protection diode of phase A; S a1 , first IGBT device of phase A; S a2 , second IGBT device of phase A; S a3 , third IGBT device of phase A; S a4 , fourth IGBT device of phase A; D a51 , fifth protection diode of phase B; D a61 , sixth protection diode of phase B; S b1 , first IGBT device of phase B; S b2 , second IGBT device of phase B; S b3 , third IGBT device of phase B; S b4, the fourth IGBT device of phase B; D a52 , the fifth protection diode of phase C; D a62 , the sixth protection diode of phase C; S c1 , the first IGBT device of phase C; S c2 , the second IGBT device of phase C; S c3 , the third IGBT device of phase C; S c4 , the fourth IGBT device of phase C; R1, the first resistor; R2, the second resistor; R3, the third resistor; R4, the fourth resistor; R5, the fifth resistor; R6, the sixth resistor; R7, the seventh resistor; R8, the eighth resistor; R9, the ninth resistor; R10, the tenth resistor. Detailed implementation mode

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0037] Embodiment

[0038] See Figure 1 , Figure 1 , which is a schematic structure diagram of a conduction voltage measurement circuit for power devices of a three-level bridge arm circuit provided by an embodiment of the present invention Figure 1 ; As Figure 1As shown in the figure, an embodiment of the present invention provides a conduction voltage measurement circuit for power devices in a three-level bridge arm circuit, which is applied to a three-level bridge arm circuit. The three-level bridge arm circuit includes: a first power device 1, a second power device 2, a third power device 3, and a fourth power device 4. The first power device 1, the second power device 2, the third power device 3, and the fourth power device 4 are connected in series. The conduction voltage measurement circuit for power devices in the three-level bridge arm circuit includes: a first conduction voltage measurement circuit 5 and a second conduction voltage measurement circuit 6. The first conduction voltage measurement circuit 5 includes: a first input port 51, a second input port 52, a third input port 53, a first output port 54, a second output port 55, and a third output port 56. The second conduction voltage measurement circuit 6 includes: a fourth input port 61, a fifth input port 62, a sixth input port 63, a fourth output port 64, a fifth output port 65, and a sixth output port 66. The first input port 51 is electrically connected to the first end of the first power device 1. The second input port 52 is electrically connected to the second end of the first power device 1, and the second input port 52 is also electrically connected to the first end of the second power device 2. The third input port 53 is electrically connected to the second end of the second power device 2. The fourth input port 61 is electrically connected to the first end of the third power device 3. The fifth input port 62 is electrically connected to the second end of the third power device 3, and the fifth input port 62 is also electrically connected to the first end of the fourth power device 4. The sixth input port 63 is electrically connected to the second end of the fourth power device 4. A first voltage value Vm1 is output between the first output port 54 and the third output port 56. A second voltage value Vm2 is output between the second output port 55 and the third output port 56. A third voltage value Vm3 is output between the fourth output port 64 and the fifth output port 65. A fourth voltage value Vm4 is output between the fourth output port 64 and the sixth output port 66. Both the first conduction voltage measurement circuit 5 and the second conduction voltage measurement circuit 6 are composed of several diodes.

[0039] A preferred implementable manner, see Figure 2 , Figure 2 is a schematic structure of a conduction voltage measurement circuit for power devices in a three-level bridge arm circuit provided by an embodiment of the present invention Figure 2 , as Figure 2 shown, a conduction voltage measurement circuit for power devices in a three-level bridge arm circuit proposed by an embodiment of the present invention is applied to measure a three-level bridge arm circuit. The three-level bridge arm circuit includes: a first power device 1, a second power device 2, a third power device 3, a fourth power device 4, a DC power supply U dc , a first capacitor C1, a second capacitor C2, a fifth protection diode D a5 and a sixth protection diode D a6 ; in this embodiment, the DC power supply U dc, the first power device 1, the second power device 2, the third power device 3 and the fourth power device 4 are connected in series. The first end of the first capacitor C1 is electrically connected to the first end of the first power device 1, and the second end of the first capacitor C1 is electrically connected to the positive electrode of the fifth protection diode D a5 . The negative electrode of the fifth protection diode D a5 is electrically connected to the second end of the first power device 1. The first end of the second capacitor C2 is electrically connected to the second end of the fourth power device 4, and the second end of the second capacitor C2 is electrically connected to the negative electrode of the sixth protection diode D a6 . The positive electrode of the sixth protection diode D a6 is electrically connected to the first end of the fourth power device 4. Among them, the first power device 1 includes: the first protection diode D a1 and the first IGBT device S a1 of phase A. The second power device 2 includes: the second protection diode D a2 and the second IGBT device S a2 of phase A. The third power device 3 includes: the third protection diode D a3 and the third IGBT device S a3 of phase A. The fourth power device 4 includes: the fourth protection diode D a4 and the fourth IGBT device S a4 ;

[0040] For an implementable manner of a preferred solution, refer to Figure 2 . Figure 2 is a schematic structure diagram of a conduction voltage measurement circuit for power devices in a three-level bridge arm circuit provided by an embodiment of the present invention. Figure 2 As shown in Figure 2 , the first conduction voltage measurement circuit 5 includes: the first diode D1, the second diode D2, the third diode D3, the fourth diode D4, the first voltage stabilizing diode Z1, the second voltage stabilizing diode Z2, the first isolated power supply V P1 , the first operational amplifier OA1 and the second operational amplifier OA2. The negative electrode of the first diode D1 is electrically connected to the first input port 51, the positive electrode of the first diode D1 is electrically connected to the negative electrode of the second diode D2, and the positive electrode of the second diode D2 is electrically connected to the positive electrode of the first isolated power supply V P1 ; The negative electrode of the third diode D3 is electrically connected to the second input port 52, the positive electrode of the third diode D3 is electrically connected to the negative electrode of the fourth diode D4, and the positive electrode of the fourth diode D4 is electrically connected to the positive electrode of the first isolated power supply V P1 ; The positive electrode of the first voltage stabilizing diode Z1 is electrically connected to the third output port 56, and the positive electrode of the first voltage stabilizing diode Z1 is electrically connected to the first isolated power supply V P1is electrically connected to the negative electrode. The negative electrode of the first voltage stabilizing diode Z1 is electrically connected to the positive electrode of the first diode D1, and the negative electrode of the first voltage stabilizing diode Z1 is electrically connected to the negative electrode of the second diode D2; the positive electrode of the second voltage stabilizing diode Z2 is electrically connected to the third output port 56, and the positive electrode of the second voltage stabilizing diode Z2 is electrically connected to the negative electrode of the first isolated power supply V P1 is electrically connected to the negative electrode. The negative electrode of the second voltage stabilizing diode Z2 is electrically connected to the positive electrode of the third diode D3, and the negative electrode of the second voltage stabilizing diode Z2 is electrically connected to the negative electrode of the fourth diode D4. The non-inverting input terminal of the first operational amplifier OA1 is electrically connected to the positive electrode of the first diode D1, the non-inverting input terminal of the first operational amplifier OA1 is electrically connected to the negative electrode of the second diode D2, the non-inverting input terminal of the first operational amplifier OA1 is electrically connected to the negative electrode of the first voltage stabilizing diode Z1, the inverting input terminal of the first operational amplifier OA1 is electrically connected to the positive electrode of the second diode D2, the inverting input terminal of the first operational amplifier OA1 is electrically connected to the positive electrode of the fourth diode D4, and the inverting input terminal of the first operational amplifier OA1 is electrically connected to the positive electrode of the first isolated power supply V P1 is electrically connected. The output terminal of the first operational amplifier OA1 is electrically connected to the first output port 54; the negative electrode of the first isolated power supply V P1 is electrically connected to the third output port 56; the positive electrode of the first voltage stabilizing diode Z1 is electrically connected to the third output port 56; the non-inverting input terminal of the second operational amplifier OA2 is electrically connected to the positive electrode of the third diode D3, the non-inverting input terminal of the second operational amplifier OA2 is electrically connected to the negative electrode of the fourth diode D4, the non-inverting input terminal of the second operational amplifier OA2 is electrically connected to the negative electrode of the second voltage stabilizing diode Z2, the inverting input terminal of the second operational amplifier OA2 is electrically connected to the positive electrode of the second diode D2, the inverting input terminal of the second operational amplifier OA2 is electrically connected to the positive electrode of the fourth diode D4, and the inverting input terminal of the second operational amplifier OA2 is electrically connected to the positive electrode of the first isolated power supply V P1 is electrically connected. The output terminal of the second operational amplifier OA2 is electrically connected to the second output port 55; the positive electrode of the second voltage stabilizing diode Z2 is electrically connected to the third output port 56. In addition, the first on-state voltage measurement circuit 5 is also provided with a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5, which can be used to protect the circuit.

[0041] In the above solution, the first operational amplifier OA1 and the second operational amplifier OA2 are connected to each diode, and then the output terminals of the first operational amplifier OA1 and the second operational amplifier OA2 are connected to the first output port 54 and the second output port 55. After different on-state voltage detection circuits are formed according to the conduction relationship of the first diode D1 and the third diode D3, the corresponding first voltage value Vm1 and second voltage value Vm2 are output from the first output port 54, the second output port 55, and the third output port 56. According to the corresponding first voltage value Vm1 and second voltage value Vm2, the on-state voltages of the first power device 1 and the second power device 2 can be obtained, and thus the on-state voltages of the power devices in the three-level bridge arm circuit can be detected in real time with a simple circuit structure, improving the measurement accuracy of the on-state voltage.

[0042] An implementable manner of a preferred solution is shown in Figure 2 , Figure 2 a structural schematic diagram of a circuit for measuring the on-state voltage of a power device in a three-level bridge arm circuit provided by an embodiment of the present invention Figure 2 , as Figure 2 shown, the second on-state voltage measurement circuit 6 includes: a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, a third voltage regulator diode Z3, a fourth voltage regulator diode Z4, a second isolated power supply V P2 , the positive electrode of the fifth diode D5 is electrically connected to the sixth input port 63, the negative electrode of the fifth diode D5 is electrically connected to the positive electrode of the sixth diode D6, and the negative electrode of the sixth diode D6 is electrically connected to the negative electrode of the second isolated power supply V P2 ; the positive electrode of the seventh diode D7 is electrically connected to the fifth input port 62, the negative electrode of the seventh diode D7 is electrically connected to the positive electrode of the eighth diode D8, and the negative electrode of the eighth diode D8 is electrically connected to the second isolated power supply V P2The negative electrode of [component] is electrically connected; the negative electrode of the third voltage stabilizing diode Z3 is electrically connected to the fourth input interface, the positive electrode of the third voltage stabilizing diode Z3 is electrically connected to the negative electrode of the seventh diode D7, and the positive electrode of the third voltage stabilizing diode Z3 is electrically connected to the positive electrode of the eighth diode D8; the negative electrode of the fourth voltage stabilizing diode Z4 is electrically connected to the fourth input interface, the positive electrode of the fourth voltage stabilizing diode Z4 is electrically connected to the negative electrode of the fifth diode D5, and the positive electrode of the fourth voltage stabilizing diode Z4 is electrically connected to the positive electrode of the sixth diode D6. The non-inverting input terminal of the third operational amplifier OA3 is electrically connected to the negative electrode of the seventh diode D7, the non-inverting input terminal of the third operational amplifier OA3 is electrically connected to the positive electrode of the eighth diode D8, the non-inverting input terminal of the third operational amplifier OA3 is electrically connected to the positive electrode of the third voltage stabilizing diode Z3, the inverting input terminal of the third operational amplifier OA3 is electrically connected to the negative electrode of the sixth diode D6, the inverting input terminal of the third operational amplifier OA3 is electrically connected to the negative electrode of the eighth diode D8, and the inverting input terminal of the third operational amplifier OA3 is electrically connected to the negative electrode of the second isolated power supply V P2 is electrically connected, and the output terminal of the third operational amplifier OA3 is electrically connected to the fifth output port 65; the positive electrode of the second isolated power supply V P2 is electrically connected to the fourth output port 64; the negative electrode of the third voltage stabilizing diode Z3 is electrically connected to the fourth output port 64; the non-inverting input terminal of the fourth operational amplifier OA4 is electrically connected to the negative electrode of the fifth diode D5, the non-inverting input terminal of the fourth operational amplifier OA4 is electrically connected to the positive electrode of the sixth diode D6, the non-inverting input terminal of the fourth operational amplifier OA4 is electrically connected to the positive electrode of the fourth voltage stabilizing diode Z4, the inverting input terminal of the fourth operational amplifier OA4 is electrically connected to the negative electrode of the sixth diode D6, the inverting input terminal of the fourth operational amplifier OA4 is electrically connected to the negative electrode of the eighth diode D8, and the inverting input terminal of the fourth operational amplifier OA4 is electrically connected to the negative electrode of the second isolated power supply V P2 is electrically connected, and the output terminal of the fourth operational amplifier OA4 is electrically connected to the sixth output port 66; the negative electrode of the fourth voltage stabilizing diode Z4 is electrically connected to the fourth output port 64. In addition, the second on-state voltage measurement circuit 6 is also provided with a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a tenth resistor R10, which can be used to protect the circuit.

[0043] In the above solution, the fifth diode D5 and the seventh diode D7 are respectively connected to the sixth input port 63 and the fifth input port 62. Thus, the conduction relationship of the fifth diode D5 and the seventh diode D7 can be affected according to the conduction relationship of the third power device 3 and the fourth power device 4. The conduction relationship of the fifth diode D5 and the seventh diode D7 will form different on-state voltage detection circuits. The third operational amplifier OA3 and the fourth operational amplifier OA4 are connected to each diode, and then the output terminals of the third operational amplifier OA3 and the fourth operational amplifier OA4 are connected to the fifth output port 65 and the sixth output port 66. After different on-state voltage detection circuits are formed according to the conduction relationship of the fifth diode D5 and the seventh diode D7, the corresponding third voltage value Vm3 and fourth voltage value Vm4 are output from the fourth output port 64, the fifth output port 65 and the sixth output port 66. According to the corresponding third voltage value Vm3 and fourth voltage value Vm4, the on-state voltages of the third power device 3 and the fourth power device 4 can be obtained, thereby realizing the real-time detection of the on-state voltages of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the accuracy of on-state voltage measurement.

[0044] An embodiment of the present invention provides a circuit for measuring the on-state voltage of a power device in a three-level bridge arm circuit. The input ports of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 for designing the circuit for measuring the on-state voltage of the power device in the three-level bridge arm circuit are connected to each power device in the three-level bridge arm circuit. The conduction relationship of the input ports of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 can be affected according to the conduction relationship of each power device in the three-level bridge arm circuit, thereby realizing the detection of the on-state voltages of each power device in the three-level bridge arm circuit, and the corresponding voltage values are output from the output ports of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6. According to the corresponding voltage values, the on-state voltages of each power device can be obtained. Moreover, both the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 are composed of several diodes. Thus, in combination with the conduction relationship of each power device in the three-level bridge arm circuit, the on-state voltages of the power devices in the three-level bridge arm circuit are detected in real time with a simple circuit structure, and the accuracy of on-state voltage measurement is improved.

[0045] As an example of an embodiment of the present invention, the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 are set as symmetric circuits.

[0046] In the above solution, the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 are set as symmetric circuits, so that the working principles of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 are the same. Furthermore, by using the same two-device connection, the on-state voltage detection of each power device can be achieved, and the circuit structure can be simplified, thereby reducing the circuit cost. The on-state voltage of the power devices in the three-level bridge arm circuit can be detected in real time with a simple circuit structure, improving the accuracy of on-state voltage measurement.

[0047] To further explain the working principle of a three-level bridge arm circuit power device on-state voltage measurement circuit proposed in an embodiment of the present invention, in this embodiment, a separate three-level A-phase bridge arm circuit is taken as an example for explanation. Taking the current flowing into the AC side as positive and flowing out as negative, the working principles of various states of the three-level bridge arm circuit are explained. For details, see Figure 3 , Figure 3 FIG. is a schematic diagram of the P state structure of a three-level bridge arm circuit of a three-level bridge arm circuit power device on-state voltage measurement circuit provided in an embodiment of the present invention; as Figure 3 shown, when the three-level A-phase bridge arm circuit is in the P state (positive voltage state), the current flow direction in the circuit is shown in the Figure 3 dashed line part. At this time, the first IGBT device S a1 of phase A and the second IGBT device S a2 of phase A are turned on, and the third IGBT device S a3 of phase A and the fourth IGBT device S a4 of phase A are turned off. When the current direction is the positive direction, the first capacitor C1 discharges, and the current flows through the first IGBT device S a1 of phase A and the second IGBT device S a2 of phase A and flows into the AC side. When the current direction is the negative direction, the first capacitor C1 is charged, and the current passes through the first protection diode D a1 and the second protection diode D a2 and reaches the positive pole of the DC power supply U dc . In this stage, the potentials of point A and point P are always the same, that is, the voltage relative to point O is +U dc / 2. Therefore, when the first IGBT device S a1 of phase A and the second IGBT device S a2 of phase A are turned on, and the third IGBT device S a3 of phase A and the fourth IGBT device S a4 of phase A are turned off, U AO is equal to +U dc / 2;

[0048] See Figure 4 , Figure 4Schematic diagram of the N - state structure of a three - level bridge - arm circuit power device conduction voltage measurement circuit provided for a certain embodiment of the present invention; as Figure 4 shown, when the three - level A - phase bridge - arm circuit is in the N state (negative - voltage state), at this time, the third IGBT device S of the A - phase a3 and the fourth IGBT device S of the A - phase a4 conduct, and the first IGBT device S of the A - phase a1 and the second IGBT device S of the A - phase a2 turn off. The current direction is shown in the Figure 4 dashed - line part. When the current direction is the positive direction, the second capacitor C2 is charged, and the power is supplied to the load through the fourth protection diode D a4 and the third protection diode D a3 . When the current direction is the negative direction, the current passes through the third IGBT device S of the A - phase a3 and the fourth IGBT device S of the A - phase a4 to discharge the second capacitor C2. In this stage, the potentials of point A and point N are always the same. Therefore, when the third IGBT device S of the A - phase a3 and the fourth IGBT device S of the A - phase a4 conduct, and the first IGBT device S of the A - phase a1 and the second IGBT device S of the A - phase a2 turn off, U AO is equal to - U dc / 2;

[0049] See Figure 5 , Figure 5 Schematic diagram of the 0 - state structure of a three - level bridge - arm circuit power device conduction voltage measurement circuit provided for a certain embodiment of the present invention; as Figure 5 shown, when the three - level A - phase bridge - arm circuit is in the 0 state, at this time, the second IGBT device S of the A - phase a2 and the third IGBT device S of the A - phase a3 conduct, and the first IGBT device S of the A - phase a1 and the fourth IGBT device S of the A - phase a4 turn off. The current direction is shown in the Figure 5 dashed - line part. When the current direction is the positive direction, the DC power supply U dc charges the first capacitor C1 and discharges the second capacitor C2. The current passes through the fifth protection diode D a5 and the second IGBT device S of the A - phase a2 to supply power to the load. When the current direction is the negative direction, the current passes through the third IGBT device S of the A - phase a3 and the sixth protection diode D a6Charge the second capacitor C2 and discharge the first capacitor C1. During this stage, the potential at point A is clamped to the same as the midpoint O. Therefore, when the second IGBT device S of phase A a2 and the third IGBT device S of phase A a3 are turned on, and the first IGBT device S of phase A a1 and the fourth IGBT device S of phase A a4 are turned off, U AO equals 0;

[0050] Summarize the relationship between the circuit switch state and the output state into Table 1 as follows:

[0051] Table 1 Relationship Table between Circuit Switch State and Output State

[0052]

[0053] From the operating principles of various states of the above three-level bridge arm circuit and Table 1, it can be seen that the first on-state voltage measurement circuit 5 only exists when the first IGBT device S of phase A a1 and the second IGBT device S of phase A a2 are turned on simultaneously and when the second IGBT device S of phase A a2 is turned on alone. The second on-state voltage measurement circuit 6 only exists when the third IGBT device S of phase A a3 and the fourth IGBT device S of phase A a4 are turned on simultaneously and when the third IGBT device S of phase A a3 is turned on alone.

[0054] It is worth mentioning that in this embodiment, the turning on and off of the devices are controlled by control signals, and the control signals depend on different modulation strategies. The three-level bridge arm circuit can adopt the SPWM modulation method. For details, refer to Figure 6 , Figure 6 which is the SPWM carrier overlap modulation waveform schematic diagram of the three-level bridge arm circuit of a three-level bridge arm circuit power device on-state voltage measurement circuit provided by an embodiment of the present invention; as Figure 6 shown, its modulation mainly generates control signals by comparing the sine modulation wave with the triangular carrier wave. More specifically, the three-level bridge arm circuit often adopts the method of carrier overlap to achieve the purpose of controlling four switching tubes. The generation principle of the control signal is as follows: Refer to Figure 7 , Figure 7 which is the schematic diagram of the driving signal generation logic of the switching tubes of phase A of the three-level bridge arm circuit of a three-level bridge arm circuit power device on-state voltage measurement circuit provided by an embodiment of the present invention; as Figure 7 shown, taking the single-phase bridge arm circuit as an example, the second IGBT device S of phase A a2 and the third IGBT device S of phase A a3The drive signals are complementary. The first IGBT device S in phase A a1 and the fourth IGBT device S in phase A a4 are complementary. When the sinusoidal modulation wave is greater than 0, that is, in the positive half - cycle, keep the second IGBT device S in phase A a2 conducting. At this time, keep the third IGBT device S in phase A a3 and the fourth IGBT device S in phase A a4 turned off. Under this condition, when the amplitude of the sinusoidal modulation wave is greater than the triangular carrier wave (equivalent to carrier 1), such as Figure 6 in the t1 time period in, then control the first IGBT device S in phase A a1 to conduct. On the contrary, when the amplitude of the sinusoidal modulation wave is less than the triangular carrier wave (equivalent to carrier 2), such as Figure 6 in the t2 time period in, control the first IGBT device S in phase A a1 to turn off; when the sinusoidal modulation wave is less than 0, that is, in the negative half - cycle, keep the third IGBT device S in phase A a3 conducting. At this time, the first IGBT device S in phase A a1 , the second IGBT device S in phase A a2 are all kept turned off. Under this condition, when the amplitude of the sinusoidal modulation wave is less than the triangular carrier wave (equivalent to carrier 2), such as Figure 6 in the t3 time period in, then control the fourth IGBT device S in phase A a4 to conduct. On the contrary, when the amplitude of the sinusoidal modulation wave is greater than the triangular carrier wave (equivalent to carrier 1), such as Figure 6 in the t4 time period in, control the fourth IGBT device S in phase A a4 to turn off, thus realizing the conduction and turn - off of the four switching tubes (i.e., IGBT devices);

[0055] In addition, referring to Figure 8 , Figure 8 is a schematic diagram of the three - level three - phase main circuit structure of a three - level bridge - arm circuit power device on - state voltage measurement circuit provided by an embodiment of the present invention; as Figure 8 shown, in addition to measuring the on - state voltage of the power device of the single - phase three - level bridge - arm circuit, it can also measure the three - level poly - phase circuit. Taking the three - level three - phase main circuit as an example, on the basis of the three - level A - phase bridge - arm circuit, add a three - level B - phase bridge - arm circuit and a three - level C - phase bridge - arm circuit. The three - level B - phase bridge - arm circuit includes: the fifth protection diode D in phase B a51 , the sixth protection diode D in phase B a61 , the first IGBT device S in phase B b1 , the second IGBT device S in phase B b2 , the third IGBT device S in phase B b3 and the fourth IGBT device S in phase B b4; The three-level C-phase bridge arm circuit includes: the fifth protection diode D of the C-phase a52 , the sixth protection diode D of the C-phase a62 , the first IGBT device S of the C-phase c1 , the second IGBT device S of the C-phase c2 , the third IGBT device S of the C-phase c3 and the fourth IGBT device S of the C-phase c4 ; The working principles of the three-level bridge arm circuits of each phase are the same. Only the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 need to be improved. For the first on-state voltage measurement circuit 5, the third diode D3 is improved to three identical diodes respectively connected to the three-level bridge arm circuits of each phase, such as Figure 8 shown, the third diode D31 of the A-phase, the third diode D32 of the B-phase and the third diode D33 of the C-phase; For the second on-state voltage measurement circuit 6, the seventh diode D7 is improved to three identical diodes respectively connected to the three-level bridge arm circuits of each phase as Figure 8 shown, the seventh diode D71 of the A-phase, the seventh diode D72 of the B-phase and the seventh diode D73 of the C-phase; Only by increasing the number of diodes can the on-state voltage detection of the multi-phase power devices be completed, which simplifies the circuit structure, facilitates operation and reduces the circuit cost at the same time.

[0056] See Figure 9 , Figure 9 is the step flow schematic diagram of a method for measuring the on-state voltage of power devices in a three-level bridge arm circuit provided by an embodiment of the present invention. As Figure 9 shown, the embodiment of the present invention proposes a method for measuring the on-state voltage of power devices in a three-level bridge arm circuit, including steps 101 to 103, and the specific steps are as follows:

[0057] Step 101, based on a preset modulation strategy, control the conduction and turn-off of each power device in the three-level bridge arm circuit to obtain the conduction states of each power device in the three-level bridge arm circuit;

[0058] Step 102, based on the conduction states of each power device in the three-level bridge arm circuit, control the conduction and turn-off of each input port of the on-state voltage measurement circuit of the power device in the three-level bridge arm circuit to obtain the corresponding voltage values output by each output port;

[0059] Step 103, based on the corresponding voltage values output by each output port, obtain the on-state voltage measurement result of the power device in the three-level bridge arm circuit.

[0060] As a preferred solution, taking the three-level A-phase bridge arm circuit as an example, according to the preset SPWM modulation strategy, control the conduction or turn-off of the four power devices, and judge the state of the current three-level A-phase bridge arm circuit according to the conduction and turn-off conditions of the four power devices. When the first IGBT device S of the A-phasea1 and the second IGBT device S of phase A a2 When they are conducting simultaneously, the three-level phase A bridge arm circuit is in a positive voltage state. When the second IGBT device S of phase A a2 and the third IGBT device S of phase A a3 are conducting simultaneously, the three-level phase A bridge arm circuit is in the 0 state. When the third IGBT device S of phase A a3 and the fourth IGBT device S of phase A a4 are conducting simultaneously, the three-level phase A bridge arm circuit is in a negative voltage state. Finally, according to the state of the current three-level phase A bridge arm circuit, the conduction and cutoff conditions of each input port of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 are controlled. Since the conduction and cutoff of each input port will affect the circuit conduction loop in the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6, and then different input ports output voltage values, so as to obtain the on-state voltage measurement result of the power device of the three-level bridge arm circuit.

[0061] An embodiment of the present invention proposes a method for measuring the on-state voltage of a power device of a three-level bridge arm circuit. The first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 of the on-state voltage measurement circuit of the power device of the three-level bridge arm circuit are designed to be connected to each power device of the three-level bridge arm circuit. The conduction relationship of each power device of the three-level bridge arm circuit can affect the conduction relationship of each input port of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6, so as to realize the detection of the on-state voltage of each power device of the three-level bridge arm circuit, and the corresponding voltage values are output from each output port of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6. According to the corresponding voltage values, the on-state voltage of each power device can be obtained. And the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6 are both composed of several diodes. Thus, combined with the conduction relationship of each power device of the three-level bridge arm circuit, the on-state voltage of the power device of the three-level bridge arm circuit can be detected in real time with a simple circuit structure, and the measurement accuracy of the on-state voltage is improved.

[0062] A preferred solution is to control the conduction and cutoff of each input port of the on-state voltage measurement circuit of the power devices in the three-level bridge arm circuit based on the conduction states of the power devices in the three-level bridge arm circuit, so as to obtain the corresponding voltage values output from each output port, including: if each power device in the three-level bridge arm circuit is in a positive voltage state, both the first power device 1 and the second power device 2 are conducting; if both the first power device 1 and the second power device 2 are conducting, the first input port 51, the second input port 52, and the third input port 53 of the on-state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all conducting; if the first input port 51, the second input port 52, and the third input port 53 of the on-state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all conducting, the difference between the first voltage value Vm1 and the second voltage value Vm2 is used as the on-state voltage of the first power device 1, and the second voltage value Vm2 is used as the on-state voltage of the second power device 2.

[0063] An implementable mode of a preferred solution is that when the first IGBT device S of phase A a1 and the second IGBT device S of phase A a2 are conducting simultaneously, the sum of Vce1 and Vce2 is less than the voltage of the first isolated power supply V P1 , so the current passes through the second diode D2 and the first diode D1 and then returns to the negative pole of the first isolated power supply V a1 after passing through the first IGBT device S of phase A a2 ; similarly for the other branch, the current passes through the fourth diode D4 and the third diode D3 and then returns to the negative pole of the first isolated power supply V P1 after passing through the second IGBT device S of phase A a2 ; at the same time, the first zener diode Z1 and the second zener diode Z2 will also be broken down by the first isolated power supply V P1 so that the voltage across their two ends is maintained at their zener voltage values, and the potentials of v1 and v2 are respectively the zener voltage values of the first zener diode Z1 and the second zener diode Z2. Taking the first operational amplifier OA1 as an example, according to the properties of the operational amplifier, assuming that the third resistor R3 = the fifth resistor R5 and the fourth resistor R4 = the second resistor R2, the following formula can be obtained: P1 According to the properties of the operational amplifier, it can be obtained that:

[0064]

[0065] According to the properties of the operational amplifier, it is obtained that:

[0066] (v1 - ) = v1 +;

[0067] So it is obtained that:

[0068] Vm1 = (2·(v1 +)) - v3 = (v1 +) - (v3 - (v1 +)) = (v1 +) - V D2 ;

[0069] Assume V D1 = V D2 ;

[0070] Then we get:

[0071] Vm1 = (v1+) - V D1 = Vce1 + Vce2;

[0072] Thus, it can be obtained that the output first voltage value Vm1 is equal to the sum of the conduction voltages of the first IGBT device S in phase A a1 and the second IGBT device S in phase A a2 . Similarly, for the second operational amplifier OA2:

[0073]

[0074] According to the properties of the operational amplifier, we get:

[0075] (v2 -) = v2+;

[0076] So we get:

[0077] Vm2 = (2·(v2+)) - v3 = (v2+) - (v3 - (v2+)) = (v2+) - V D4 ;

[0078] If V D3 = V D4 ;

[0079] Then we get:

[0080] Vm2 = (v2+) - V D3 = Vce2;

[0081] Therefore, the output second voltage value Vm2 is equivalent to the on - state voltage of the second IGBT device S in phase A a2 . Then, by subtracting the output results of the two operational amplifiers, the on - state voltage of the first IGBT device S in phase A can be obtained, that is, the on - state voltage of the first IGBT device S in phase A a1 is Vm1 - Vm2. a1 The on - state voltage of the first IGBT device S in phase A is Vm1 - Vm2.

[0082] In the above solution, when each power device of the three-level bridge arm circuit is in a positive voltage state, the first power device 1 and the second power device 2 are both turned on. At this time, the first input port 51, the second input port 52, and the third input port 53 are turned on. Then, according to the connection relationship and conduction relationship of the first on-state voltage measurement circuit 5, the on-state voltages of the first power device 1 and the second power device 2 are detected, and the corresponding voltage values are output from the first output port 54, the second output port 55, and the third output port 56 as the on-state voltages of the first power device 1 and the second power device 2, realizing real-time detection of the on-state voltages of the power devices in the three-level bridge arm circuit with a simple circuit structure and improving the measurement accuracy of the on-state voltage.

[0083] A preferred solution is to control the conduction and turn-off of each input port of the on-state voltage measurement circuit of the power devices in the three-level bridge arm circuit based on the conduction states of the power devices in the three-level bridge arm circuit, and obtain the corresponding voltage values output from each output port, including: if each power device in the three-level bridge arm circuit is in a negative voltage state, the third power device 3 and the fourth power device 4 are both turned on; if the third power device 3 and the fourth power device 4 are both turned on, the fourth input port 61, the fifth input port 62, and the sixth input port 63 of the on-state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all turned on; if the fourth input port 61, the fifth input port 62, and the sixth input port 63 of the on-state voltage measurement circuit of the power devices in the three-level bridge arm circuit are all turned on, the difference between the third voltage value Vm3 and the fourth voltage value Vm4 is used as the on-state voltage of the third power device 3, and the third voltage value Vm3 is used as the on-state voltage of the fourth power device 4.

[0084] An implementable manner of a preferred solution is that when the third IGBT device S of phase A a3 and the fourth IGBT device S of phase A a4 are both turned on, the sum of Vce3 and Vce4 is less than the voltage of the second isolated power supply V P2 , so the current passes through the third IGBT device S of phase A a3 and the fourth IGBT device S of phase A a4 , and returns to the negative pole of the second isolated power supply V P2 after passing through the fifth diode D5 and the sixth diode D6; similarly for the other branch, the current passes through the third IGBT device S of phase A a3 , the seventh diode D7, and the eighth diode D8 and then returns to the negative pole of the second isolated power supply V P2 , and at the same time, the third zener diode Z3 and the fourth zener diode Z4 will also be connected to the second isolated power supply V P2Breakdown keeps the voltage across its two ends at its regulated voltage value, that is, the potentials of V4 and V5 are respectively the regulated voltage values of the third zener diode Z3 and the fourth zener diode Z4. Taking the fourth operational amplifier OA4 as an example, according to the properties of the operational amplifier, assuming that the seventh resistor R7 = the eighth resistor R8 and the ninth resistor R9 = the tenth resistor R10, the following formula can be obtained:

[0085]

[0086] Where:

[0087] (v4 - ) = v4+;

[0088] So, it can be obtained that:

[0089] Vm4 = (2·(v4+)) - v6 = v5 + v5 - v6 = v5 + V D6 ;

[0090] Assume V D5 = V D6 ;

[0091] Then, it can be obtained that:

[0092] Vm4 = v5 + V D5 = Vce3 + Vce4;

[0093] From this, it can be seen that its output fourth voltage value Vm4 is equal to the sum of the conduction voltages of the third IGBT device S in phase A a3 and the fourth IGBT device S in phase A a4 . Similarly, for the third operational amplifier OA3:

[0094]

[0095] According to the properties of the operational amplifier, it can be obtained that:

[0096] (v3 - ) = v3+ = v4;

[0097] Then, it can be obtained that:

[0098] Vm3 = (2·(v3+)) - v6 = v4 + v4 - v6 = v5 + V D8 ;

[0099] Assume V D7 = V D8 ;

[0100] Then, it can be obtained that:

[0101] Vm3 = v4 + V D7 = Vce3;

[0102] Therefore, its output third voltage value Vm3 is equivalent to the third IGBT device S in phase Aa3 The on-state voltage, and then subtracting the output results of the two operational amplifiers can obtain the on-state voltage of the fourth IGBT device S in phase A a4 The on-state voltage, that is, the on-state voltage of the fourth IGBT device S in phase A a4 The on-state voltage is Vm4 - Vm3.

[0103] In the above solution, each power device of the three-level bridge arm circuit is in a negative voltage state, then the third power device 3 and the fourth power device 4 are both turned on. At this time, the fourth input port 61, the fifth input port 62, and the sixth input port 63 are turned on. Furthermore, according to the connection relationship and conduction relationship of the second on-state voltage measurement circuit 6, the on-state voltages of the third power device 3 and the fourth power device 4 are detected, and the corresponding voltage values are output from the fourth output port 64, the fifth output port 65, and the sixth output port 66 as the on-state voltages of the third power device 3 and the fourth power device 4, realizing real-time detection of the on-state voltages of the power devices of the three-level bridge arm circuit with a simple circuit structure and improving the measurement accuracy of the on-state voltage.

[0104] A preferred solution is to control the conduction and turn-off of each input port of the on-state voltage measurement circuit of the power devices of the three-level bridge arm circuit based on the conduction states of the power devices of the three-level bridge arm circuit, and obtain the corresponding voltage values output from each output port, including: if each power device of the three-level bridge arm circuit is in the 0 state, then the second power device 2 and the third power device 3 are both turned on; if the second power device 2 and the third power device 3 are both turned on, then the second input port 52, the third input port 53, the fourth input port 61, and the fifth input port 62 of the on-state voltage measurement circuit of the power devices of the three-level bridge arm circuit are all turned on; if the second input port 52, the third input port 53, the fourth input port 61, and the fifth input port 62 of the on-state voltage measurement circuit of the power devices of the three-level bridge arm circuit are all turned on, then the second voltage value Vm2 is used as the on-state voltage of the second power device 2, and the third voltage value Vm3 is used as the on-state voltage of the fourth power device 4.

[0105] As an implementable manner of a preferred solution, when only the second IGBT device S in phase A a2 and the third IGBT device S in phase A a3 are turned on, for the second IGBT device S in phase A a2 being turned on, the first diode D1 is turned off due to the high voltage on the first IGBT device S in phase A a1 . At this time, the output of the first operational amplifier OA1 is clamped to a fixed value. Then, according to the formula in the above implementable manner, the specific clamped value is v1 - v D2 , which prevents the influence on the first on-state voltage measurement circuit 5 when the switching tube is turned off, and the conducting second IGBT device S in phase A a2, the measurement principle of its on-state voltage is the same as that in the positive voltage state above. The third diode D3 and the fourth diode D4 are conducting. The second operational amplifier OA2 outputs the second voltage value Vm2 as its on-state voltage through the second output port 55 and the third output port 56. The specific calculation formula is as follows:

[0106]

[0107] According to the properties of the operational amplifier:

[0108] (v2-) = v2+;

[0109] So we get:

[0110] Vm2 = (2·(v2+)) - v3 = (v2+) - (v3 - (v2+)) = (v2+) - V D4 ;

[0111] If V D3 = V D4 ;

[0112] Then we get:

[0113] Vm2 = (v2+) - V D3 = Vce2;

[0114] When the first IGBT device S of phase A a1 and the second IGBT device S of phase A a2 are all turned off, the first operational amplifier OA1 and the second operational amplifier OA2 output the clamping voltage through the first output port 54, the second output port 55 and the third output port 56, which are v1 - V D2 and v2 - V D4 .

[0115] For the third IGBT device S of phase A a3 conducting, the fifth diode D5 is turned off due to the high voltage on the fourth IGBT device S of phase A a4 . At this time, the output of the fourth operational amplifier OA4 is clamped to a fixed value. Then, according to the formula in the above feasible embodiment, the specific clamped value is v5 + V D6 , which prevents the influence on the second on-state voltage measurement circuit 6 when the switching tube is turned off. And for the conducting third IGBT device S of phase A a3 , the measurement principle of its on-state voltage is the same as that in the negative voltage state above. The seventh diode D7 and the eighth diode D8 are conducting. The third operational amplifier OA3 outputs the third voltage value Vm3 as its on-state voltage through the fourth output port 64 and the fifth output port 65. When the third IGBT device S of phase A a3 and the fourth IGBT device S of phase A a4When all are turned off, the third operational amplifier OA3 and the fourth operational amplifier OA4 output a clamping voltage through the fourth output port 64, the fifth output port 65, and the sixth output port 66, which are v5 + V D6 and v4 + V D8 .

[0116] In the above solution, when each power device of the three-level bridge arm circuit is in the 0 state, only the second power device 2 and the third power device 3 are conducting. At this time, the first input port 51 and the sixth input port 63 are turned off. According to the connection relationship and conduction relationship of the first on-state voltage measurement circuit 5 and the second on-state voltage measurement circuit 6, the on-state voltages of the second power device 2 and the third power device 3 are detected, and the corresponding voltage values are output from the second output port 55, the third output port 56, the fourth output port 64, and the fifth output port 65 as the on-state voltages of the second power device 2 and the third power device 3, thereby realizing the real-time detection of the on-state voltages of the power devices of the three-level bridge arm circuit with a simple circuit structure and improving the measurement accuracy of the on-state voltage.

[0117] As another example of the embodiment of the present invention, taking Figure 8 the first on-state voltage detection circuit in a three-level three-phase main circuit shown as an example, the principle of the on-state voltage measurement circuit of the power devices of the three-level bridge arm circuit in the three-level multi-phase main circuit is explained. When only the three-level A-phase bridge arm circuit is in the P state, at this time, the A-phase first IGBT device S a1 and the A-phase second IGBT device S a2 are conducting. The first isolated power supply V P1 forms a current loop through the first diode D1, the second diode D2, the A-phase first IGBT device S a1 and the A-phase second IGBT device S a2 . At the same time, a current loop is composed of the fourth diode D4, the A-phase third diode D31, and the A-phase second IGBT device S a2 . Based on the measurement principle introduced above, at this time, the first voltage value Vm1 is the sum of the on-state voltages of the A-phase first IGBT device S a1 and the A-phase second IGBT device S a2 , and the second voltage value Vm2 is the on-state voltage of the A-phase second IGBT device S a2 . The B-phase third diode D32 and the C-phase third diode D33 are blocked due to the high voltage borne by the switching tubes. At this time, the B-phase and the C-phase are in a negative voltage state or a 0-level state. Then, the second on-state voltage detection circuit measures the on-state voltages of the A-phase third IGBT device S a3 and the A-phase fourth IGBT device S a4 ; similarly, when only the B-phase is in the P state, the first voltage value Vm1 measures the on-state voltage of the B-phase first IGBT device S b1and the second IGBT device S of phase B b2 The sum of the on-state voltages of, and the second voltage value Vm2 is the on-state voltage of the second IGBT device S of phase B b2 The same applies to phase C. In this embodiment, another situation also needs to be considered. As Figure 8 shown, assuming that the second IGBT device S of phase A a2 , the second IGBT device S of phase B b2 and the second IGBT device S of phase C c2 conduct simultaneously, due to the unidirectional conductivity of the diode, the current can only flow unidirectionally through the switching tube. At this time, the first voltage value Vm1 can be expressed as the on-state voltages of the three switching tubes. Of course, in actual experiments, the measurement results when a certain phase conducts alone are still taken;

[0118] It is worth mentioning that since the second on-state voltage detection circuit and the first on-state voltage detection circuit are symmetric circuits, their principles are the same as those of the first on-state voltage detection circuit, and will not be elaborated here.

[0119] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principles of the present invention, several improvements and deformations can still be made, and these improvements and deformations should also be regarded as the protection scope of the present invention.

[0120] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0121] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" can explicitly or implicitly include at least one of the features. In the description of the present application, "a plurality" means two or more, unless specifically defined otherwise.

Claims

1. A conduction voltage measurement circuit for power devices in a three-level bridge arm circuit, which is applied to a three-level bridge arm circuit. The three-level bridge arm circuit includes: A first power device, a second power device, a third power device, and a fourth power device, where the first power device, the second power device, the third power device, and the fourth power device are connected in series. It is characterized in that the three-level bridge arm circuit power device on-state voltage measurement circuit includes: A first on-state voltage measurement circuit and a second on-state voltage measurement circuit; The first on-state voltage measurement circuit includes: a first input port, a second input port, a third input port, a first output port, a second output port, and a third output port; The second on-state voltage measurement circuit includes: a fourth input port, a fifth input port, a sixth input port, a fourth output port, a fifth output port, and a sixth output port; The first input port is electrically connected to the first end of the first power device, the second input port is electrically connected to the second end of the first power device, the second input port is also electrically connected to the first end of the second power device, and the third input port is electrically connected to the second end of the second power device; The fourth input port is electrically connected to the first end of the third power device, the fifth input port is electrically connected to the second end of the third power device, the fifth input port is also electrically connected to the first end of the fourth power device, and the sixth input port is electrically connected to the second end of the fourth power device; A first voltage value is output between the first output port and the third output port, a second voltage value is output between the second output port and the third output port, a third voltage value is output between the fourth output port and the fifth output port, and a fourth voltage value is output between the fourth output port and the sixth output port; Both the first on-state voltage measurement circuit and the second on-state voltage measurement circuit are composed of several diodes.

2. The on-state voltage measurement circuit of the power device of a three-level bridge arm circuit according to claim 1, wherein The first on-state voltage measurement circuit includes: a first diode, a second diode, a third diode, a fourth diode, a first zener diode, a second zener diode, and a first isolated power supply; The negative electrode of the first diode is electrically connected to the first input port, the positive electrode of the first diode is electrically connected to the negative electrode of the second diode, and the positive electrode of the second diode is electrically connected to the positive electrode of the first isolated power supply; The negative electrode of the third diode is electrically connected to the second input port, the positive electrode of the third diode is electrically connected to the negative electrode of the fourth diode, and the positive electrode of the fourth diode is electrically connected to the positive electrode of the first isolated power supply; The positive electrode of the first zener diode is electrically connected to the third output port, the positive electrode of the first zener diode is electrically connected to the negative electrode of the first isolated power supply, the negative electrode of the first zener diode is electrically connected to the positive electrode of the first diode, and the negative electrode of the first zener diode is electrically connected to the negative electrode of the second diode; The positive electrode of the second zener diode is electrically connected to the third output port, the positive electrode of the second zener diode is electrically connected to the negative electrode of the first isolated power supply, the negative electrode of the second zener diode is electrically connected to the positive electrode of the third diode, and the negative electrode of the second zener diode is electrically connected to the negative electrode of the fourth diode.

3. The on-state voltage measurement circuit of a three-level bridge arm circuit power device according to claim 2, wherein, The first on-state voltage measurement circuit includes: a first operational amplifier and a second operational amplifier; The non-inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the first diode, the non-inverting input terminal of the first operational amplifier is electrically connected to the negative electrode of the second diode, the non-inverting input terminal of the first operational amplifier is electrically connected to the negative electrode of the first zener diode, the inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the second diode, the inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the fourth diode, the inverting input terminal of the first operational amplifier is electrically connected to the positive electrode of the first isolated power supply, and the output terminal of the first operational amplifier is electrically connected to the first output port; the negative electrode of the first isolated power supply is electrically connected to the third output port; the positive electrode of the first zener diode is electrically connected to the third output port; The non-inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the third diode, the non-inverting input terminal of the second operational amplifier is electrically connected to the negative electrode of the fourth diode, the non-inverting input terminal of the second operational amplifier is electrically connected to the negative electrode of the second zener diode, the inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the second diode, the inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the fourth diode, the inverting input terminal of the second operational amplifier is electrically connected to the positive electrode of the first isolated power supply, and the output terminal of the second operational amplifier is electrically connected to the second output port; the positive electrode of the second zener diode is electrically connected to the third output port.

4. The on-state voltage measurement circuit of a three-level bridge arm circuit power device according to claim 1, characterized in that The second on-state voltage measurement circuit includes: a fifth diode, a sixth diode, a seventh diode, an eighth diode, a third zener diode, a fourth zener diode, and a second isolated power supply; The positive electrode of the fifth diode is electrically connected to the sixth input port, the negative electrode of the fifth diode is electrically connected to the positive electrode of the sixth diode, and the negative electrode of the sixth diode is electrically connected to the negative electrode of the second isolated power supply; The positive electrode of the seventh diode is electrically connected to the fifth input port, the negative electrode of the seventh diode is electrically connected to the positive electrode of the eighth diode, and the negative electrode of the eighth diode is electrically connected to the negative electrode of the second isolated power supply; The negative electrode of the third zener diode is electrically connected to the fourth input interface, the positive electrode of the third zener diode is electrically connected to the negative electrode of the seventh diode, and the positive electrode of the third zener diode is electrically connected to the positive electrode of the eighth diode; The negative electrode of the fourth zener diode is electrically connected to the fourth input interface, the positive electrode of the fourth zener diode is electrically connected to the negative electrode of the fifth diode, and the positive electrode of the fourth zener diode is electrically connected to the positive electrode of the sixth diode.

5. The on-state voltage measurement circuit for the power device of a three-level bridge arm circuit according to claim 4, wherein The second on-state voltage measurement circuit includes: a third operational amplifier and a fourth operational amplifier; The non-inverting input terminal of the third operational amplifier is electrically connected to the negative electrode of the seventh diode, the non-inverting input terminal of the third operational amplifier is electrically connected to the positive electrode of the eighth diode, the non-inverting input terminal of the third operational amplifier is electrically connected to the positive electrode of the third voltage stabilizing diode, the inverting input terminal of the third operational amplifier is electrically connected to the negative electrode of the sixth diode, the inverting input terminal of the third operational amplifier is electrically connected to the negative electrode of the eighth diode, the inverting input terminal of the third operational amplifier is electrically connected to the negative electrode of the second isolated power supply, and the output terminal of the third operational amplifier is electrically connected to the fifth output port; the positive electrode of the second isolated power supply is electrically connected to the fourth output port; the negative electrode of the third voltage stabilizing diode is electrically connected to the fourth output port; The non-inverting input terminal of the fourth operational amplifier is electrically connected to the negative electrode of the fifth diode, the non-inverting input terminal of the fourth operational amplifier is electrically connected to the positive electrode of the sixth diode, the non-inverting input terminal of the fourth operational amplifier is electrically connected to the positive electrode of the fourth voltage stabilizing diode, the inverting input terminal of the fourth operational amplifier is electrically connected to the negative electrode of the sixth diode, the inverting input terminal of the fourth operational amplifier is electrically connected to the negative electrode of the eighth diode, the inverting input terminal of the fourth operational amplifier is electrically connected to the negative electrode of the second isolated power supply, and the output terminal of the fourth operational amplifier is electrically connected to the sixth output port; the negative electrode of the fourth voltage stabilizing diode is electrically connected to the fourth output port.

6. A conduction voltage measurement circuit for a three-level bridge arm circuit power device according to any one of claims 1 to 5, characterized in that, Including: The first on-state voltage measurement circuit and the second on-state voltage measurement circuit are set as symmetrical circuits.

7. A method for measuring the on-state voltage of a power device in a three-level bridge arm circuit, characterized in that, Applied to a three-level bridge arm circuit power device on-state voltage measurement circuit according to any one of claims 1 to 6, the three-level bridge arm circuit power device on-state voltage measurement method includes: Based on a preset modulation strategy, controlling the conduction and cutoff of each power device in the three-level bridge arm circuit to obtain the conduction states of each power device in the three-level bridge arm circuit; Based on the conduction states of each power device in the three-level bridge arm circuit, controlling the conduction and cutoff of each input port of the three-level bridge arm circuit power device on-state voltage measurement circuit to obtain the corresponding voltage values output by each output port; Based on the corresponding voltage values output by each output port, obtaining the on-state voltage measurement result of the three-level bridge arm circuit power device.

8. The method for measuring the on-state voltage of a power device in a three-level bridge arm circuit according to claim 7, wherein Based on the conduction states of each power device in the three-level bridge arm circuit, controlling the conduction and cutoff of each input port of the three-level bridge arm circuit power device on-state voltage measurement circuit to obtain the corresponding voltage values output by each output port, including: If each power device in the three-level bridge arm circuit is in a positive voltage state, both the first power device and the second power device are conducting; If both the first power device and the second power device are conducting, the first input port, the second input port, and the third input port of the three-level bridge arm circuit power device on-state voltage measurement circuit are all conducting; If the first input port, the second input port, and the third input port of the three-level leg circuit power device on-state voltage measurement circuit are all conducting, then the difference between the first voltage value and the second voltage value is used as the on-state voltage of the first power device, and the second voltage value is used as the on-state voltage of the second power device.

9. The method for measuring the on-state voltage of a power device in a three-level bridge arm circuit according to claim 7, characterized in that, Based on the conduction states of the power devices in the three-level leg circuit, control the conduction and cutoff of the input ports of the three-level leg circuit power device on-state voltage measurement circuit to obtain the corresponding voltage values output by each output port, including: If the power devices in the three-level leg circuit are in the negative voltage state, then both the third power device and the fourth power device are conducting; If both the third power device and the fourth power device are conducting, then the fourth input port, the fifth input port, and the sixth input port of the three-level leg circuit power device on-state voltage measurement circuit are all conducting; If the fourth input port, the fifth input port, and the sixth input port of the three-level leg circuit power device on-state voltage measurement circuit are all conducting, then the difference between the third voltage value and the fourth voltage value is used as the on-state voltage of the third power device, and the third voltage value is used as the on-state voltage of the fourth power device.

10. A method for measuring the on-state voltage of a power device in a three-level bridge arm circuit according to claim 7, characterized in that, Based on the conduction states of the power devices in the three-level leg circuit, control the conduction and cutoff of the input ports of the three-level leg circuit power device on-state voltage measurement circuit to obtain the corresponding voltage values output by each output port, including: If the power devices in the three-level leg circuit are in the 0 state, then both the second power device and the third power device are conducting; If both the second power device and the third power device are conducting, then the second input port, the third input port, the fourth input port, and the fifth input port of the three-level leg circuit power device on-state voltage measurement circuit are all conducting; If the second input port, the third input port, the fourth input port, and the fifth input port of the three-level leg circuit power device on-state voltage measurement circuit are all conducting, then the second voltage value is used as the on-state voltage of the second power device, and the third voltage value is used as the on-state voltage of the fourth power device.

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