A main circuit and control method of a high-voltage four-quadrant frequency conversion integrated machine capable of bypass

Abstract

The application provides a main loop and control method of a high-voltage four-quadrant frequency conversion integrated machine which can bypass, comprising: a high-voltage motor comprising 3xM same power units, an input reactor, an input circuit breaker, an input electrical contactor, a pre-charge resistor and 3xM independent coils; the power unit comprises a rectifier circuit, an inverter circuit, a DC filter module and a DC voltage detection module; wherein the rectifier circuit and the inverter circuit of the power unit have the same structure, and the inverter circuit output is connected to both ends of the winding coil of the motor; when the power unit fails, the controller controls the rectifier circuit and the open circuit inverter circuit to complete bypass of the current power unit. The application solves the problem of large grid side voltage and current harmonics caused by diode rectification which affects the work of other devices, and can work in the four-quadrant range; the fault part can be bypassed, and the reliability of the operation of the frequency conversion integrated machine is improved.

Description

Technical Field

[0001] This invention belongs to the field of frequency converter technology, specifically relating to the main circuit and control method of a bypassable high-voltage four-quadrant frequency converter. Background Technology

[0002] In recent years, with the continuous development and progress of my country's power industry, the application prospects of frequency converter technology in the domestic power system are very broad. Moreover, the space and efficiency advantages brought by frequency converters have led to their increasing market application. High-voltage frequency converters, especially those with voltage levels from 3.3kV to 10kV, eliminate the full-power phase-shifting transformer, which not only improves overall efficiency but also reduces the space occupied by the equipment. However, current high-voltage frequency converters generally use diode rectification, operating in two quadrants. This means the frequency converter can only drive the motor in either forward or reverse direction, making it unsuitable for motor-generated power. Furthermore, power unit redundancy significantly reduces power output, limiting its application. Additionally, the voltage and current harmonics generated by diode rectification exceed standard values, affecting other equipment in the power supply system and, in severe cases, even causing other equipment to malfunction. These problems are particularly prominent in applications with small grid capacity and a high proportion of power from diode rectifiers. Summary of the Invention

[0003] In view of the above-mentioned shortcomings of the prior art, the present invention provides a main circuit and control method for a bypassable high-voltage four-quadrant frequency converter to solve the above-mentioned technical problems.

[0004] In a first aspect, the present invention provides a main circuit of a bypassable high-voltage four-quadrant frequency converter, comprising: a high-voltage motor containing 3×M identical power units, an input reactor, an input circuit breaker, an input contactor, a pre-charge resistor, and 3×M independent coils;

[0005] The power grid input terminal is connected to three input circuit breakers, each phase's input circuit breaker is connected to an input contactor, and each phase's input contactor is connected in parallel with a pre-charging resistor; each phase's input contactor is connected to an input reactor; each phase's input reactor is connected to M power units connected in series, and the output of each power unit is connected to the corresponding independent coil of the motor.

[0006] The power unit includes a rectifier circuit, an inverter circuit, a DC filter module, and a DC voltage detection module. The rectifier circuit and inverter circuit of the power unit have the same structure, and the output of the inverter circuit is connected to both ends of the motor winding coil. When the power unit fails, the controller controls the rectifier circuit and the open-circuit inverter circuit to bypass the current power unit.

[0007] Furthermore, the controller includes a rectifier controller and an inverter controller. The rectifier controller controls the part of the frequency converter that connects to the power grid and the rectifier circuit of the power unit, and stabilizes the DC bus voltage of the power unit. The inverter controller is used to control the inverter circuit of the power unit and work with the load motor to achieve motor drive.

[0008] Furthermore, the rectifier controller and the rectifier circuit of the power unit are connected by optical fiber, and the inverter controller and the inverter circuit of the power unit are connected by optical fiber. The rectifier controller and the inverter controller achieve interlocking for start and stop through signal connection. Each power unit is equipped with a transmitting optical fiber and a receiving optical fiber. The transmitting optical fiber sends the drive pulse signal, power-on signal, reset signal and synchronization signal output by the rectifier controller or inverter controller to the power unit.

[0009] Furthermore, except for the R terminal of the first power unit which is connected to the input reactor, the R terminals of the remaining power units are all connected to the S terminal of the previous power unit, and the S terminals of the last three-phase power units are connected together to form a common point.

[0010] Secondly, the present invention provides a control method for a bypassable high-voltage four-quadrant frequency converter, comprising:

[0011] Power-on state: The rectifier controller receives the power-on command from the frequency converter, closes the input circuit breaker, charges the power unit through the pre-charging resistor, and after the voltage on the DC filter module capacitor of the power unit reaches the preset value, it closes the input contactor. At this time, the frequency converter is in the power-on state.

[0012] Ready state: The rectifier controller collects the input three-phase high-voltage system voltage and current, as well as the DC bus voltage of all power units, to drive the switches of the power unit rectifier circuits, controlling the switches to maintain operation. The power unit bus voltage is basically stable, and the DC bus voltage amplitude is consistent among the power units in each phase. At this time, the inverter is in a ready state, waiting for the inverter to start.

[0013] Operating status: After receiving the inverter's operating command, the inverter controller controls the inverter circuit of the power unit to start working; the inverter controller collects the DC bus voltage and output current of all power units, generates a three-phase modulation wave, and generates the drive signal of the power unit's inverter circuit after being compared and controlled by each power unit respectively.

[0014] Fault status: If a power unit of the inverter or a winding of the motor fails, the inverter controller blocks the inverter output of the faulty unit, opens the corresponding motor winding, and adjusts the voltage phase of the remaining windings so that the magnetic field of the motor remains a complete circular magnetic field. After the inverter is blocked, the input power of the power unit becomes zero, and the rectifier controller controls the input terminal of the rectifier circuit of the power unit to be short-circuited.

[0015] The beneficial effects of this invention are as follows: It provides a bypassable high-voltage four-quadrant frequency converter, which can solve the problem of large harmonics in the grid-side voltage and current caused by diode rectification affecting the operation of other equipment. Furthermore, when applied to potential energy type motor loads, it can operate within the four-quadrant range, sending the energy from the motor feedback system back to the grid. When a part of the frequency converter or motor fails, the faulty part can be bypassed, improving the reliability of the frequency converter. The power unit structure of this invention is simple and highly modular, making it easy to expand, replace, and maintain in practical applications. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a topology diagram of the main circuit of a bypassable high-voltage four-quadrant frequency converter provided in one embodiment of the present invention;

[0018] Figure 2 This is a diagram of the internal topology of a power unit provided in one embodiment of the present invention;

[0019] Figure 3 This is a schematic diagram of a power unit bypass control method provided in an embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0021] like Figure 1 As shown, an embodiment of the present invention provides a main circuit of a bypassable high-voltage four-quadrant frequency converter, including: a high-voltage motor comprising 3×M identical power units, an input reactor, an input circuit breaker, an input contactor, a pre-charge resistor, and 3×M independent coils;

[0022] The power grid input terminal is connected to three input circuit breakers, each phase's input circuit breaker is connected to an input contactor, and each phase's input contactor is connected in parallel with a pre-charging resistor; each phase's input contactor is connected to an input reactor; each phase's input reactor is connected to M power units connected in series, and the output of each power unit is connected to the corresponding independent coil of the motor.

[0023] The power unit includes a rectifier circuit, an inverter circuit, a DC filter module, and a DC voltage detection module. The rectifier circuit and inverter circuit of the power unit have the same structure, and the output of the inverter circuit is connected to both ends of the motor winding coil. When the power unit fails, the controller controls the rectifier circuit and the open-circuit inverter circuit to bypass the current power unit.

[0024] like Figure 1 The high-voltage bypassable four-quadrant frequency converter topology includes: an input circuit breaker QF1, three-phase pre-charge resistors R1, R2, and R3, an input contactor KM1, a three-phase input reactor L1, 3×M power units, and a motor with 3×M windings. The power units are arranged sequentially, and the connection between the power unit outputs and the motor coils is polarized, requiring a one-to-one correspondence to ensure the integrity of the motor's internal magnetic field. The rectifier circuit of the power unit is identical to the inverter circuit. The output terminals U and V of the inverter circuit are connected to the two ends of the motor winding coils, providing the required AC voltage to the motor according to control requirements. The rectifier circuit is responsible for stabilizing the DC bus voltage of the unit, filtering high-frequency voltage fluctuations caused by the switching of the self-healing thin-film capacitors, and storing the reactive power of the motor windings.

[0025] like Figure 2 As shown, the power unit provided in this embodiment of the invention operates in a four-quadrant mode, including a rectifier circuit, a DC filter circuit, a DC voltage detection circuit, and an inverter circuit.

[0026] It should be noted that the number of power units M in the inverter integrated machine topology provided by the present invention is determined according to the grid voltage level and the selected switching device voltage level.

[0027] Optionally, as an embodiment of the present invention, the controller includes a rectifier controller and an inverter controller, wherein the rectifier circuit of the inverter unit and the power unit are controlled to stabilize the DC bus voltage of the power unit and provide a stable and balanced voltage for the inverter, and the inverter controller is used to control the inverter circuit of the power unit to drive the motor in conjunction with the load motor.

[0028] Specifically, the rectifier controller collects the DC bus voltage value, the amplitude and phase of the high-voltage input voltage, and the three-phase current of all power units, and provides drive signals for the power units. The rectifier controller provided by this invention is used to stabilize the DC bus voltage of the power units and ensure that the bus voltages of each power unit are basically consistent. The inverter controller is used to control the H-bridge inverter section of the power unit, outputting the desired voltage value to the individual coil windings of the motor, forming a rotating magnetic field within the motor to make the motor rotate.

[0029] Optionally, as an embodiment of the present invention, the rectifier controller and the rectifier circuit of the power unit are connected by optical fiber, and the inverter controller and the inverter circuit of the power unit are connected by optical fiber. The rectifier controller and the inverter controller achieve interlocking for start and stop through signal connection; each power unit is provided with a transmitting optical fiber and a receiving optical fiber, wherein the transmitting optical fiber sends the drive pulse signal, power-on signal, reset signal and synchronization signal output by the rectifier controller or the inverter controller to the power unit.

[0030] Specifically, the power unit is equipped with two optical fibers: one for receiving and the other for transmitting. The rectifier controller or inverter controller controls the power unit through this optical fiber. For example, the transmitting optical fiber sends the H-bridge drive pulse signal, power-on signal, reset signal, and synchronization signal output by the rectifier controller to the rectifier H-bridge section of the power unit to stabilize the DC bus voltage of the power unit and ensure that the bus voltages of each power unit are basically consistent.

[0031] Optionally, as an embodiment of the present invention, except that the R terminal of the first power unit is connected to the input reactor, the R terminals of the remaining power units are all connected to the S terminal of the previous power unit, and the S terminals of the last three-phase power units are connected together to form a common point.

[0032] Specifically, for example Figure 1 Each phase has M power units connected in series. The R terminal of unit A1 is connected to the input reactor terminal, the S terminal of unit A1 is connected to the R terminal of unit A2, the S terminal of unit A2 is connected to the R terminal of unit A3, and so on. M-1 S-terminal and unit A M The R terminal is connected. The structure and connection method of the three-phase power units A, B, and C are the same. Each phase unit A M B M C M The S-ends are connected together to form the common point of the phase unit.

[0033] In addition to the frequency converter integrated machine provided in the above embodiments, this invention also provides a control method for the above frequency converter integrated machine, specifically including the following steps:

[0034] Power-on state: The rectifier controller receives the power-on command from the frequency converter, closes the input circuit breaker, and charges the power unit through the pre-charging resistor. After the voltage on the DC filter module capacitor of the power unit reaches the preset value, the input contactor is closed, and the frequency converter is in the power-on state.

[0035] Ready state: The rectifier controller collects the input three-phase high-voltage system voltage and current, as well as the DC bus voltage of all power units, to drive the switches of the power unit rectifier circuits, controlling the switches to maintain operation. The power unit bus voltage is basically stable, and the DC bus voltage amplitude is consistent among the power units in each phase. At this time, the inverter is in a ready state, waiting for the inverter to start.

[0036] Operating status: After receiving the inverter's operating command, the inverter controller controls the inverter circuit of the power unit to start working; the inverter controller collects the DC bus voltage and output current of all power units, generates a three-phase modulation wave, and generates the drive signal of the power unit's inverter circuit after being compared and controlled by each power unit respectively.

[0037] Specifically, with Figure 1 For example, during operation, circuit breaker QF1 is first closed, and the DC filter modules of the 3×M power units are charged through the three-phase pre-charge resistors R1, R2, R3, and the three-phase input reactor L1. After the DC bus voltage of the power unit exceeds the designed value, the input contactor KM1 is closed, putting the frequency converter into a ready state. After power-on, the voltage equalization circuit inside the power unit is put into use. When the power loss in each power unit is different, the loss of the voltage equalization resistor is greater than the loss of the unit itself, achieving the purpose of static balancing of the DC bus voltage among the power units.

[0038] Fault status: such as Figure 3 As shown, if a power unit of the inverter or a winding of the motor fails, the inverter controller blocks the inverter output of the faulty unit, opens the corresponding motor winding, and adjusts the voltage phase of the remaining windings so that the magnetic field of the motor remains a complete circular magnetic field. After the inverter is blocked, the input power of the power unit becomes zero, and the rectifier controller controls the input terminal of the rectifier circuit of the power unit to be short-circuited.

[0039] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the invention by those skilled in the art without departing from the spirit and essence of the invention. Such modifications or substitutions should all fall within the scope of the invention, or any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the invention should be covered within the protection scope of the invention. Therefore, the protection scope of the invention should be determined by the scope of the claims.

Claims

1. A main circuit of a high-voltage four-quadrant variable frequency integrated machine that can be bypassed, characterized in that, The application relates to a high-voltage motor comprising 3xM same power units, input reactors, input circuit breakers, input contactors, pre-charging resistors and 3xM independent coils. The input ends of the power grid are connected with three input circuit breakers respectively, the input circuit breaker of each phase is connected with an input contactor respectively, one pre-charging resistor is connected in parallel with the input contactor of each phase, the input contactor of each phase is connected with an input reactor, and M power units connected in series are connected with the input reactor of each phase, and the output of each power unit is connected to the corresponding independent coil of the motor. The power units are arranged in sequence, the R end of the first power unit is connected with the input reactor, the R end of the remaining power units is connected with the S end of the previous power unit, and the S ends of the last power units of the three phases are connected together to form a common point; the connection between the power unit output and the motor coil is polarized, and the connection needs to be one-to-one corresponding, so as to ensure the integrity of the magnetic field in the motor; The power unit comprises a rectification circuit, an inverter circuit, a direct-current filtering module and a direct-current voltage detection module; the rectification circuit and the inverter circuit of the power unit are the same in structure, the output of the inverter circuit is connected to the winding coil of the motor; when the power unit fails, the input end of the rectification circuit is short-circuited and the inverter circuit is opened to complete the bypass of the current power unit through the controller; The controller comprises a rectification controller and an inverter controller; the rectification controller is used for controlling the part connected with the power grid of the frequency conversion all-in-one machine and the rectification circuit of the power unit, and stabilizing the direct-current bus voltage of the power unit; the inverter controller is used for controlling the inverter circuit of the power unit, and realizing motor driving in cooperation with the load motor; if a power unit of the frequency converter or a winding of the motor fails, the inverter controller blocks the inverter output of the fault unit to make the corresponding motor winding open, and adjusts the voltage phase of the remaining winding to make the magnetic field of the motor still be a complete circular magnetic field; the input power of the power unit after inverter blocking becomes zero, and the rectification controller controls the input end of the rectification circuit of the power unit to be short-circuited. The rectification controller and the rectification circuit of the power unit adopt optical fiber connection, the inverter controller and the inverter circuit of the power unit adopt optical fiber connection, the rectification controller and the inverter controller are interlocked through signal connection to realize starting and stopping, one sending optical fiber and one receiving optical fiber are arranged in each power unit, the sending optical fiber sends the driving pulse signal, the starting signal, the reset signal and the synchronization signal output by the rectification controller or the inverter controller to the power unit.

2. The main circuit according to claim 1, characterized in that The application relates to a high-voltage motor comprising 3xM same power units, input reactors, input circuit breakers, input contactors, pre-charging resistors and 3xM independent coils.

3. A control method for the primary circuit according to claim 2, characterized in that, The input ends of the power grid are connected with three input circuit breakers respectively, the input circuit breaker of each phase is connected with an input contactor respectively, one pre-charging resistor is connected in parallel with the input contactor of each phase, the input contactor of each phase is connected with an input reactor, and M power units connected in series are connected with the input reactor of each phase, and the output of each power unit is connected to the corresponding independent coil of the motor. The power units are arranged in sequence, the R end of the first power unit is connected with the input reactor, the R end of the remaining power units is connected with the S end of the previous power unit, and the S ends of the last power units of the three phases are connected together to form a common point; the connection between the power unit output and the motor coil is polarized, and the connection needs to be one-to-one corresponding, so as to ensure the integrity of the magnetic field in the motor; The power unit comprises a rectification circuit, an inverter circuit, a direct-current filtering module and a direct-current voltage detection module; the rectification circuit and the inverter circuit of the power unit are the same in structure, the output of the inverter circuit is connected to the winding coil of the motor; when the power unit fails, the input end of the rectification circuit is short-circuited and the inverter circuit is opened to complete the bypass of the current power unit through the controller; The controller comprises a rectification controller and an inverter controller; the rectification controller is used for controlling the part connected with the power grid of the frequency conversion all-in-one machine and the rectification circuit of the power unit, and stabilizing the direct-current bus voltage of the power unit; the inverter controller is used for controlling the inverter circuit of the power unit, and realizing motor driving in cooperation with the load motor; if a power unit of the frequency converter or a winding of the motor fails, the inverter controller blocks the inverter output of the fault unit to make the corresponding motor winding open, and adjusts the voltage phase of the remaining winding to make the magnetic field of the motor still be a complete circular magnetic field; the input power of the power unit after inverter blocking becomes zero, and the rectification controller controls the input end of the rectification circuit of the power unit to be short-circuited. The rectification controller and the rectification circuit of the power unit adopt optical fiber connection, the inverter controller and the inverter circuit of the power unit adopt optical fiber connection, the rectification controller and the inverter controller are interlocked through signal connection to realize starting and stopping, one sending optical fiber and one receiving optical fiber are arranged in each power unit, the sending optical fiber sends the driving pulse signal, the starting signal, the reset signal and the synchronization signal output by the rectification controller or the inverter controller to the power unit. Ready state: the rectifier controller collects input three-phase high-voltage system voltage, current and all power unit DC bus voltage to generate power unit rectifier loop switch drive, control switch to act to maintain, power unit bus voltage is basically stable, and the DC bus voltage amplitude between each power unit in each phase is consistent, at this time the frequency conversion all-in-one machine is in ready state waiting for inverter work command; Working state: after receiving the inverter work command, the inverter controller controls the power unit inverter circuit to start working; the inverter controller collects all power unit DC bus voltage and output current, generates three-phase modulation wave, and then generates power unit inverter circuit drive signal after comparison control of each power unit; Fault state: if a power unit of the frequency converter or a winding of the motor fails, the inverter controller blocks the inverter output of the fault unit to open the corresponding motor winding, and adjusts the voltage phase of the remaining winding to make the magnetic field of the motor still a complete circular magnetic field; the input power of the inverter blocked power unit becomes zero, and the rectifier controller controls the power unit rectifier circuit input end to be short-circuited.

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