Frequency converter parallel operation control device and frequency converter parallel operation control system

Abstract

The application discloses a frequency converter parallel control device and a frequency converter parallel control system, and relates to the technical field of frequency converters, wherein the frequency converter parallel control device comprises an external power supply connecting end, a rectifier circuit, a total drive board, a plurality of sub-drive boards, a plurality of inverter circuits, a current operation circuit, an analog quantity sampling board and a control circuit; the total drive board generates multiple-phase different signals and synchronously drives a plurality of power half-bridges in each inverter circuit through the sub-drive boards, the output ends of each half-bridge are short-circuited to make the current superimposed, and single-bridge-arm high-power output is realized. The current operation circuit synthesizes total currents of each bridge arm and feeds back to the control circuit, the control circuit adjusts the driving signal according to the total currents, closed-loop control is formed, and the output currents of each phase are balanced. The technical scheme provided by the application can solve the problems of high cost, difficult development and poor current sharing of the prior art.

Description

Technical Field

[0001] This invention relates to the field of frequency converter technology, and in particular to a frequency converter parallel operation control device and a frequency converter parallel operation control system. Background Technology

[0002] A frequency converter (VDC) is a power control device that controls the speed of an AC motor by changing the frequency of the power supply. It is widely used in industrial automation, fans and pumps, elevators, and rail transportation. With the increasing size and power of industrial equipment, the market demand for ultra-high-power VDCs is growing. Currently, one common way to achieve high-power variable frequency output is to operate multiple VDCs in parallel. There are two main existing VDC parallel control schemes: the first is a master-slave synchronous parallel scheme, which sets up a master control unit and multiple slave control units. The master control unit synchronizes with each slave control unit through communication signals. Under the control of the synchronization signals, each control unit drives its corresponding inverter unit, and the outputs of multiple inverter units are connected in parallel to supply power to the load. The second is an FPGA-based parallel scheme, which includes a control unit, an input rectifier unit, a parallel board, multiple inverter units, and multiple interface boards. The parallel board has a built-in FPGA chip for expanding I / O ports, and control commands are simultaneously sent to each inverter unit via the parallel board to achieve parallel output current sharing.

[0003] However, the existing solutions mentioned above still have the following shortcomings: In the master-slave synchronization scheme, due to the differences in device parameters and line impedance of each inverter unit, it is difficult to guarantee the balance of output current even if carrier synchronization is achieved, and there are deviations in the closed-loop control response. In addition, a large number of copper busbars or cables need to be connected in parallel at the output of multiple inverter units, resulting in high material costs. In the FPGA-based scheme, the hardware cost is higher than that of the MCU plus dedicated driver chip scheme due to the mid-to-high-end FPGA chip and its supporting peripheral circuits. The development cycle is also longer, and there is also the problem of high material costs for output connection. Summary of the Invention

[0004] The main objective of this invention is to propose a frequency converter parallel operation control device and a frequency converter parallel operation control system, which aims to solve the problems of high cost, difficult development, and poor current sharing of existing solutions.

[0005] To achieve the above objectives, the inverter parallel operation control device proposed in this invention is applied to the inverter parallel operation control system. The inverter parallel operation control device includes: External power supply connection terminal, used to connect to an external power source; A rectifier circuit, wherein the input terminal of the rectifier circuit is connected to the external power supply connection terminal; The main driver board is used to generate multiple drive signals with different phases. Multiple sub-drive boards are electrically connected to the main drive board in a one-to-one correspondence. Each sub-drive board is used to receive one of the drive signals output by the main drive board. Multiple inverter circuits, the input terminals of which are respectively connected to the output terminal of the rectifier circuit; Each inverter circuit includes multiple power half-bridges, the output terminals of the multiple power half-bridges are shorted to form a single-phase bridge arm, and each inverter circuit is connected to a corresponding sub-drive board. The sub-drive board is used to simultaneously distribute one of the drive signals received from the main drive board to the multiple power half-bridges. A current calculation circuit, the input terminal of which is connected to the current detection terminals of the plurality of power half-bridges respectively, is used to add the branch currents of the plurality of power half-bridges to synthesize the total single-phase bridge arm current of the inverter circuit. An analog sampling board, the input terminals of which are respectively connected to the output terminals of each of the current calculation circuits, is used to collect the analog signal of the total current of a single-phase bridge arm synthesized by multiple inverter circuits; A control circuit, the input of which is connected to the output of the analog sampling board, and the output of which is connected to the main drive board, is used to adjust the multi-channel drive signals output by the main drive board according to the received analog signals of the total current of the multiple single-phase bridge arms.

[0006] In one embodiment, the inverter parallel operation control device further includes a DC bus; The first end of the DC bus is connected to the output end of the rectifier circuit, and the second end of the DC bus is connected to the input ends of the plurality of inverter circuits.

[0007] In one embodiment, the inverter parallel control device includes at least one of the inverter circuits.

[0008] In one embodiment, at least one of the inverter circuits includes a first inverter circuit, a second inverter circuit, and a third inverter circuit; The input terminals of the first inverter circuit, the second inverter circuit, and the third inverter circuit are connected in parallel with the DC bus. The first inverter circuit is used to output U-phase current, the second inverter circuit is used to output V-phase current, and the third inverter circuit is used to output W-phase current.

[0009] In one embodiment, the input terminal of the analog sampling board is connected to the rectifier circuit to collect the input current of the rectifier circuit and transmit the collected signal to the control circuit.

[0010] In one embodiment, the current calculation circuit includes an adder circuit; The input terminal of the adder circuit is connected to the current detection terminal of the power half-bridge. The adder circuit is used to perform an addition operation on the analog current signal corresponding to the current detection terminal, and output the analog signal of the total current of the single-phase bridge arm to the analog quantity sampling board.

[0011] In one embodiment, the analog sampling board includes an analog-to-digital converter; The analog-to-digital converter is used to convert the analog signal of the total current of the single-phase bridge arm into a digital signal and transmit the digital signal to the control circuit.

[0012] In one embodiment, the control circuit employs a DSP chip, which adjusts the duty cycle of the PWM signal output to the main drive board based on the digital signal to control the inverter circuit.

[0013] In one embodiment, the main drive board and the plurality of sub-drive boards are connected by optical fibers; The sub-drive board is electrically connected to the corresponding inverter circuit and transmits drive signals.

[0014] The present invention also proposes a frequency converter parallel operation control system, including the frequency converter parallel operation control device as described in any of the above claims.

[0015] The technical solution of this invention includes an external power supply connection terminal, a rectifier circuit, a main driver board, multiple sub-driver boards, multiple inverter circuits, a current calculation circuit, an analog sampling board, and a control circuit. The external power supply connection terminal is used to connect to an external power source; the input terminal of the rectifier circuit is connected to the external power supply connection terminal; the main driver board is used to generate multiple drive signals with different phases; the multiple sub-driver boards are electrically connected to the main driver board in a one-to-one correspondence, and each sub-driver board is used to receive one of the drive signals output by the main driver board; the input terminals of the multiple inverter circuits are respectively connected to the output terminals of the rectifier circuits; each inverter circuit includes multiple power half-bridges, and the output terminals of the multiple power half-bridges are short-circuited to form a single-phase bridge arm, and each inverter circuit is connected to one sub-driver board. The system should be connected to a driver board, which simultaneously distributes one drive signal received from the main driver board to multiple power half-bridges; the input terminals of the current calculation circuits are connected to the current detection terminals of the multiple power half-bridges, and the current calculation circuits are used to sum the branch currents of the multiple power half-bridges to synthesize the total single-phase bridge arm current of the inverter circuit; the input terminals of the analog sampling board are connected to the output terminals of each current calculation circuit, and the analog signal of the total single-phase bridge arm current synthesized by the multiple inverter circuits is used to collect the analog signal; the input terminal of the control circuit is connected to the output terminal of the analog sampling board, and the output terminal of the control circuit is connected to the main driver board, and the control circuit is used to adjust the multi-channel drive signals output by the main driver board according to the received analog signals of the total single-phase bridge arm current.

[0016] In this way, the main drive board generates multiple drive signals of different phases, and multiple sub-drive boards are electrically connected to the main drive board one-to-one. Each sub-drive board receives one of the drive signals and simultaneously distributes it to multiple power half-bridges within the corresponding inverter circuit, so that multiple power half-bridges within the same inverter circuit receive the same drive signal synchronously. The output terminals of multiple power half-bridges in each inverter circuit are short-circuited to form a single-phase bridge arm, so that the currents of multiple power half-bridges are superimposed. The current calculation circuit adds the branch currents of multiple power half-bridges within the same inverter circuit to synthesize the total single-phase bridge arm current of the inverter circuit. The analog sampling board collects the analog signal of the total single-phase bridge arm current synthesized by each inverter circuit and sends it to the control circuit. The control circuit adjusts the multiple drive signals output by the main drive board according to the received feedback signals of the total single-phase bridge arm current, thereby forming a closed-loop control that can adjust the output current of each inverter circuit and ensure the current sharing capability of the output current of multiple inverter circuits. Attached Figure Description

[0017] 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, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0018] Figure 1 A schematic diagram of an embodiment of the inverter parallel operation control device provided by the present invention; Figure 2 This is a schematic diagram of another embodiment of the inverter parallel control device provided by the present invention.

[0019] Explanation of icon numbers: 100. Variable frequency drive parallel operation control device; 10. External power supply connection terminal; 20. Rectifier circuit; 30. Main drive board; 40. Driver board; 50. Inverter circuit; 60. Current calculation circuit; 70. Analog sampling board; 80. Control circuit; 90. DC bus; 200. Variable frequency drive parallel control system.

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] A frequency converter (VDC) is a power control device that controls the speed of an AC motor by changing the frequency of the power supply. It is widely used in industrial automation, fans and pumps, elevators, and rail transportation. With the increasing size and power of industrial equipment, the market demand for ultra-high-power VDCs is growing. Currently, one common way to achieve high-power variable frequency output is to operate multiple VDCs in parallel. There are two main existing VDC parallel control schemes: the first is a master-slave synchronous parallel scheme, which sets up a master control unit and multiple slave control units. The master control unit synchronizes with each slave control unit through communication signals. Under the control of the synchronization signals, each control unit drives its corresponding inverter unit, and the outputs of multiple inverter units are connected in parallel to supply power to the load. The second is an FPGA-based parallel scheme, which includes a control unit, an input rectifier unit, a parallel board, multiple inverter units, and multiple interface boards. The parallel board has a built-in FPGA chip for expanding I / O ports, and control commands are simultaneously sent to each inverter unit via the parallel board to achieve parallel output current sharing.

[0023] However, the existing solutions mentioned above still have the following shortcomings: In the master-slave synchronization scheme, due to the differences in device parameters and line impedance of each inverter unit, it is difficult to guarantee the balance of output current even if carrier synchronization is achieved, and there are deviations in the closed-loop control response. In addition, a large number of copper busbars or cables need to be connected in parallel at the output of multiple inverter units, resulting in high material costs. In the FPGA-based scheme, the hardware cost is higher than that of the MCU plus dedicated driver chip scheme due to the mid-to-high-end FPGA chip and its supporting peripheral circuits. The development cycle is also longer, and there is also the problem of high material costs for output connection.

[0024] To address these issues, this invention proposes a frequency converter parallel operation control device, aiming to solve the problems of high cost, difficult development, and poor current sharing in existing solutions.

[0025] Please see Figure 1 In one embodiment of the present invention, the inverter parallel operation control device is applied to the inverter parallel operation control system, and the inverter parallel operation control device includes: External power supply connection terminal, used to connect to an external power source; The rectifier circuit has its input terminal connected to the external power supply terminal. The main driver board is used to generate multiple drive signals with different phases. Multiple sub-drive boards are electrically connected to the main drive board in a one-to-one correspondence. Each sub-drive board is used to receive one of the drive signals output by the main drive board. Multiple inverter circuits, with their input terminals connected to the output terminals of the rectifier circuit respectively; Each inverter circuit includes multiple power half-bridges. The output terminals of the multiple power half-bridges are shorted to form a single-phase bridge arm. Each inverter circuit is connected to a corresponding sub-drive board. The sub-drive board is used to simultaneously distribute one of the drive signals received from the main drive board to the multiple power half-bridges. The current calculation circuit has its input terminals connected to the current detection terminals of multiple power half-bridges. The current calculation circuit is used to add the branch currents of multiple power half-bridges to synthesize the total single-phase bridge arm current of the inverter circuit. The analog sampling board has its input terminals connected to the output terminals of each current calculation circuit to acquire the analog signal of the total current of a single-phase bridge arm synthesized by multiple inverter circuits. The control circuit has its input terminal connected to the output terminal of the analog sampling board and its output terminal connected to the main drive board. It is used to adjust the multi-channel drive signals output by the main drive board based on the received analog signals of the total current of multiple single-phase bridge arms.

[0026] Optionally, the control circuit can be implemented using a main controller, such as an MCU (Micro Controller Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), or SOC (System-on-Chip). In one example, the DSP chip compares the received actual digital values ​​of the output current of each phase with the target current values ​​stored internally or set externally to calculate the current deviation. Based on the deviation, the DSP chip uses a PID algorithm or other closed-loop control algorithm to calculate the correction value of the PWM signal duty cycle that needs to be adjusted, and then updates the duty cycle register of the PWM modulation module, thereby adjusting the duty cycle of the PWM signal output to the main driver board.

[0027] In this embodiment, the inverter parallel control device includes an external power supply connection terminal, a rectifier circuit, a main drive board, multiple sub-drive boards, multiple inverter circuits, a current calculation circuit, an analog sampling board, and a control circuit. An external AC power source, such as 380V / 50Hz AC from an industrial power grid, is connected through the external power supply connection terminal. The AC power is converted into stable DC power by the rectifier circuit and delivered to the input terminals of each inverter circuit. Simultaneously, the control circuit generates corresponding control commands based on the target output voltage and frequency and sends these commands to the main drive board. The main drive board generates multiple drive signals with different phases according to the control commands, where the number of drive signals corresponds to the final required number of AC phases for output. Each drive signal is transmitted to a corresponding sub-drive board. Each sub-drive board is connected to its corresponding inverter circuit. Each inverter circuit contains multiple power half-bridges, and the output terminals of these power half-bridges are short-circuited to each other via copper busbars or wires, thereby merging to form a single-phase bridge arm. After receiving one of the drive signals from the main drive board, the sub-drive board simultaneously distributes that drive signal to multiple power half-bridges within its inverter circuit, causing these power half-bridges to turn on or off synchronously. Since the outputs of the multiple power half-bridges are short-circuited together, the currents output by each power half-bridge automatically superimpose at the short-circuit point, forming the total output current of a single-phase bridge arm of the inverter circuit. Multiple inverter circuits output their respective single-phase bridge arm currents, which together constitute the multi-phase AC output of the inverter parallel control device. To achieve closed-loop control, each power half-bridge is equipped with a current detection terminal to detect the branch current of the power half-bridge. A current calculation circuit is also installed next to each inverter circuit, with its input terminals connected to the current detection terminals of the multiple power half-bridges within the inverter circuit. The current calculation circuit performs analog addition on the branch currents of each power half-bridge to synthesize an analog signal of the total single-phase bridge arm current of the inverter circuit. Each inverter circuit's current calculation circuit then outputs its synthesized analog signal of the total single-phase bridge arm current to the analog sampling board. The analog sampling board acquires analog signals of the total current of multiple single-phase bridge arms, performs necessary filtering or scaling, and then transmits these signals to the control circuit. The control circuit compares the received total current signals of each single-phase bridge arm with a preset target current value to calculate the current deviation. Based on this deviation, the control circuit generates an adjustment command using a PID or other closed-loop control algorithm and outputs the adjustment command to the main drive board. The main drive board adjusts the pulse width or phase of its multi-channel drive signals accordingly, thereby changing the actual output current of each inverter circuit, making the output current of each phase approach the target value, and achieving output current sharing and stable control.

[0028] Optionally, the output of the rectifier circuit is not directly connected to the inputs of each inverter circuit, but rather connected to a common DC bus. The first end of this DC bus is electrically connected to the output of the rectifier circuit to receive the stable DC power output. The second end of the DC bus is simultaneously electrically connected to the inputs of multiple inverter circuits, thereby distributing DC power in parallel to each inverter circuit.

[0029] In one example, a three-phase frequency converter with an output power of 45kW needs to be built. An external power supply is connected to a three-phase 380V AC power source via an external power supply connection terminal. The AC power is converted into stable DC power, for example, approximately 540VDC, by a rectifier circuit. The converted DC power is delivered to the DC bus, which serves as a common DC power transmission channel. The positive and negative terminals of the DC bus are connected to the DC input terminals of each inverter circuit, thus distributing the DC power in parallel to the three subsequent inverter circuits. Under the control of the control circuit, the main drive board generates three drive signals with a phase difference of 120 degrees, corresponding to the final output U-phase, V-phase, and W-phase, respectively. These three drive signals are transmitted to three sub-drive boards, each connected to one inverter circuit. Each inverter circuit contains three power half-bridges, whose output terminals are directly shorted together via copper busbars, forming a single-phase bridge arm. The driver board simultaneously distributes the received drive signals to the three power half-bridges within the inverter circuit, causing them to turn on or off synchronously. The currents automatically superimpose at the short-circuit points, resulting in a combined output of the corresponding phase current. Specifically, the three inverter circuits correspond to the U-phase, V-phase, and W-phase outputs, respectively, independently inverting the DC power from the DC bus into AC power of the required frequency and amplitude. Each inverter circuit is connected to a corresponding current calculation circuit located outside the inverter circuit. Each power half-bridge has a current detection terminal, and the input terminal of the current calculation circuit is connected to the current detection terminals of multiple power half-bridges within the same inverter circuit. The current calculation circuit performs analog addition on the three branch currents to synthesize the total current of a single-phase bridge arm of the inverter circuit. The three current calculation circuits output the total current signals of the U-phase, V-phase, and W-phase to the analog sampling board, which converts these signals through analog-to-digital conversion and transmits the digital signals to the control circuit. The control circuit compares the received actual three-phase current values ​​with the preset target values, and generates adjustment commands through a closed-loop control algorithm, such as the PID algorithm, and outputs them to the main drive board. The main drive board then adjusts the pulse width or phase of each drive signal accordingly, thereby achieving output current sharing and stable control.

[0030] The aforementioned DC bus structure simplifies and standardizes the power connection between the rectifier and inverter circuits, while facilitating the expansion of more inverter circuits without requiring modifications to the wiring from the rectifier circuit to each inverter unit. Furthermore, the DC bus can be connected in parallel to a braking unit or energy storage unit, providing braking or energy feedback functionality to the system. Throughout the process, there is no need to use FPGA or CPLD chips to expand I / O ports; the drive signals are uniformly issued by the main driver board, ensuring synchronized signal transmission. The short-circuited power half-bridge structure and current synthesis feedback mechanism effectively guarantee the current sharing capability of each bridge arm.

[0031] Optionally, each drive signal output terminal of the main drive board is electrically connected to a corresponding input terminal of a sub-drive board. Taking a three-phase frequency converter as an example, specifically, the U-phase drive signal output terminal of the main drive board is connected to the input terminal of the first sub-drive board, the V-phase drive signal output terminal of the main drive board is connected to the input terminal of the second sub-drive board, and the W-phase drive signal output terminal of the main drive board is connected to the input terminal of the third sub-drive board. Each sub-drive board is connected to an inverter circuit. After receiving the drive signal sent by the main drive board, the sub-drive board simultaneously distributes the drive signal to multiple power half-bridges within the corresponding inverter circuit. Since the output terminals of multiple power half-bridges within the same inverter circuit are short-circuited to form a single-phase bridge arm, and multiple power half-bridges receive the same drive signal, each power half-bridge is synchronously turned on or off, and their output currents are automatically superimposed at the short-circuit point to jointly form the output current of the corresponding phase. Taking a 45kW three-phase frequency converter as an example, the main drive board generates three drive signals, U, V, and W, with a phase difference of 120°. The U-phase drive signal is transmitted to the first sub-drive board, which simultaneously distributes the U-phase drive signal to the three power half-bridges inside the first inverter circuit. The output currents of the three power half-bridges are superimposed to form the total U-phase current output. Similarly, the V-phase and W-phase drive signals are transmitted through the second and third sub-drive boards, respectively, to drive the corresponding inverter circuits to output the total V-phase and W-phase currents.

[0032] It is worth noting that a one-to-one connection between the main driver board and the sub-driver boards is adopted. The drive signals are sent uniformly by the main driver board, ensuring the phase relationship and synchronization of each drive signal. The sub-driver boards are responsible for signal distribution, eliminating the need for complex signal processing, thereby simplifying circuit design and reducing hardware costs.

[0033] Optionally, each inverter circuit contains multiple power half-bridges, each equipped with a current detection terminal for detecting the branch current output by the power half-bridge. Each inverter circuit also has a corresponding current calculation circuit, whose input terminals are electrically connected to the current detection terminals of the multiple power half-bridges within the inverter circuit. After receiving multiple branch current signals, the current calculation circuit performs analog addition on these signals to synthesize the total single-phase bridge arm current of the inverter circuit.

[0034] Specifically, taking a single inverter circuit as an example, the inverter circuit contains three power half-bridges, which output the first branch current, the second branch current, and the third branch current, respectively. The current calculation circuit adds these three branch currents together, i.e., I0. total = I1 + I2 + I3, synthesized to obtain the total single-phase bridge arm current of the inverter circuit. The output terminal of the current calculation circuit is electrically connected to the input terminal of the analog sampling board, sending the synthesized single-phase bridge arm total current signal to the analog sampling board. For a three-phase output system, there are three inverter circuits, corresponding to the U-phase, V-phase, and W-phase outputs respectively. Each inverter circuit is equipped with a current calculation circuit: the first current calculation circuit synthesizes the U-phase total current, the second current calculation circuit synthesizes the V-phase total current, and the third current calculation circuit synthesizes the W-phase total current. The three current calculation circuits send the total current signals of the U-phase, V-phase, and W-phase to the analog sampling board respectively. The analog sampling board filters, scales, and conditions these signals before sending them to the control circuit. The control circuit compares the received three-phase actual current values ​​with the target values ​​and generates adjustment commands through a closed-loop control algorithm, thereby realizing feedback control. By using the current calculation circuit, the actual output current of each phase can be obtained without using FPGA or CPLD chips to expand I / O ports, ensuring both synchronous transmission of drive signals and closed-loop current sharing control after multiple frequency converters are paralleled.

[0035] In this way, the main drive board generates multiple drive signals of different phases, and multiple sub-drive boards are electrically connected to the main drive board one-to-one. Each sub-drive board receives one of the drive signals and simultaneously distributes it to multiple power half-bridges within the corresponding inverter circuit, so that multiple power half-bridges within the same inverter circuit receive the same drive signal synchronously. The output terminals of multiple power half-bridges in each inverter circuit are short-circuited to form a single-phase bridge arm, so that the currents of multiple power half-bridges are superimposed. The current calculation circuit adds the branch currents of multiple power half-bridges within the same inverter circuit to synthesize the total single-phase bridge arm current of the inverter circuit. The analog sampling board collects the analog signal of the total single-phase bridge arm current synthesized by each inverter circuit and sends it to the control circuit. The control circuit adjusts the multiple drive signals output by the main drive board according to the received feedback signals of the total single-phase bridge arm current, thereby forming a closed-loop control that can adjust the output current of each inverter circuit and ensure the current sharing capability of the output current of multiple inverter circuits.

[0036] like Figure 2 As shown, in one embodiment, the inverter parallel control device includes at least one inverter circuit.

[0037] Optionally, the second terminal of the DC bus is connected in parallel to the input terminals of the first, second, and third inverter circuits, respectively. This can be understood as the positive and negative terminals of the DC bus being simultaneously connected to the DC input terminals of the three inverter circuits, allowing the three inverter circuits to draw power from the DC bus independently and without interference. Specifically, the first inverter circuit outputs U-phase current, the second inverter circuit outputs V-phase current, and the third inverter circuit outputs W-phase current. Together, these three inverter circuits form a complete three-phase AC output system. Taking a 45kW inverter parallel control system as an example, the first inverter circuit inverts the DC power supplied by the DC bus into U-phase AC power output, the second inverter circuit inverts it into V-phase AC power output, and the third inverter circuit inverts it into W-phase AC power output. The phases of the three output currents differ by 120 degrees, and after being combined, they drive a three-phase load, such as a high-power fan or water pump.

[0038] It should be noted that the above explanation uses three-phase output as an example, but the present invention is not limited to three-phase output. The number of inverter circuits can be increased or decreased according to the needs of the actual application scenario. For example, when driving a single-phase load, only one inverter circuit can be set up, with multiple power half-bridges inside the inverter circuit short-circuited to form a single-phase bridge arm, outputting single-phase AC power. When driving a two-phase load, two inverter circuits can be set up, each outputting two-phase current. When driving a load with more phases, such as a six-phase motor, six inverter circuits can be set up, each outputting six-phase current, with the phase difference between each phase current evenly distributed according to the actual number of phases. Therefore, the number of inverter circuits matches the actual number of AC phases required for output, and can be flexibly configured according to power expansion needs and load type, exhibiting good scalability.

[0039] In one embodiment, the current calculation circuit includes an adder circuit; The input terminal of the adder circuit is connected to the current detection terminal of the power half-bridge; The adder circuit is used to perform addition operations on the analog current signals corresponding to the current detection terminals and output the analog signal of the total current of the single-phase bridge arm to the analog sampling board.

[0040] Optionally, the input terminals of the adder circuit are electrically connected to the current sensing terminals of multiple power half-bridges within the same inverter circuit. Each power half-bridge's current sensing terminal outputs a current analog signal proportional to the branch current of the power half-bridge, such as a 0-5V voltage signal or a 4-20mA current signal. After receiving these current analog signals, the adder circuit performs an analog addition operation, meaning the output signal equals the sum of the input signals. The output terminal of the adder circuit is electrically connected to the input terminal of an analog sampling board, outputting the analog signal of the total single-phase bridge arm current obtained after the addition operation to the analog sampling board. In one example, a single inverter circuit contains three power half-bridges, and the current sensing terminals of the three power half-bridges respectively output analog signals of the first, second, and third branch currents to the three input terminals of the adder circuit. The adder circuit performs an addition operation on these three signals, i.e., V... out = V1+ V2+ V3 or I out = I1 + I2 + I3, the output result is the analog signal corresponding to the total current of a single-phase bridge arm of the inverter circuit. The analog signal is sent to the analog sampling board, processed by the analog sampling board, and then transmitted to the control circuit for closed-loop feedback control.

[0041] In one embodiment, the analog sampling board includes an analog-to-digital converter; An analog-to-digital converter is used to convert the analog signal of the total current of a single-phase bridge arm into a digital signal and transmit the digital signal to the control circuit.

[0042] Optionally, the analog sampling board includes an internal analog-to-digital converter (ADC). The input of the ADC is electrically connected to the output of the current calculation circuit to receive the analog signal of the total current of a single-phase bridge arm. The ADC converts the analog signal into a corresponding digital signal, and its output is electrically connected to the control circuit to transmit the converted digital signal to the control circuit.

[0043] In a single inverter circuit example, the current calculation circuit sums the branch currents of the three power half-bridges and outputs a 0-5V analog voltage signal, the voltage value being proportional to the total current of a single-phase bridge arm of the inverter circuit. This analog voltage signal is fed into an analog sampling board, where an analog-to-digital converter (ADC), such as a 12-bit successive approximation ADC, converts it into a digital value between 0 and 4095, where 0 corresponds to 0A and 4095 corresponds to the full-scale current value. The digital value is then transmitted to the control circuit via a parallel bus or a serial interface, such as SPI.

[0044] like Figure 2 As shown, in one embodiment, the main drive board and multiple sub-drive boards are connected by optical fibers; The driver board is electrically connected to the corresponding inverter circuit and transmits drive signals.

[0045] Optionally, the main driver board converts the PWM drive signal generated by the control circuit into an optical signal, which is then transmitted to each of the sub-driver boards via optical fiber. Each sub-driver board has an internal optical receiving circuit for receiving the optical signal from the optical fiber and converting it back into an electrical signal. The sub-driver board is electrically connected to the corresponding inverter circuit, transmitting the converted drive signal to multiple power half-bridges within the inverter circuit.

[0046] In a three-phase output system example, the main drive board generates three PWM drive signals: U-phase, V-phase, and W-phase. The main drive board internally incorporates electro-optical conversion circuits, such as laser diodes or LEDs, to convert the three electrical signals into three optical signals, which are then transmitted via three optical fibers to three sub-drive boards. The first sub-drive board receives the U-phase drive optical signal via optical fiber. Its internal optical receiving circuit, such as a photodiode or phototransistor, converts the optical signal back into a U-phase PWM electrical signal, which is then transmitted to the corresponding inverter circuit via electrical connections, driving multiple power half-bridges within that inverter circuit to output U-phase current. Similarly, the second sub-drive board receives and converts the V-phase drive signal, and the third sub-drive board receives and converts the W-phase drive signal. The advantage of using optical fiber connections is that it achieves electrical isolation between the main drive board and the sub-drive boards. In inverter systems, the inverter circuit operates under high voltage and high current conditions, and the operation of the power half-bridge switches generates strong electromagnetic interference. Optical fiber transmits optical signals rather than electrical signals, thus avoiding electromagnetic interference and ensuring the integrity and accuracy of the drive signals. Meanwhile, optical fiber enables high-voltage electrical isolation between the main drive board side (low-voltage control circuit) and the sub-drive board side (high-voltage power circuit), improving the safety and reliability of the system and eliminating the need for additional optocouplers or isolation transformers.

[0047] The present invention also proposes a frequency converter parallel operation control system, which includes a frequency converter parallel operation control device. The specific structure of the frequency converter parallel operation control device is as described in the above embodiments. Since the frequency converter parallel operation control system adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0048] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A frequency converter parallel operation control device applied to a frequency converter parallel operation control system, characterized by, include: External power supply connection terminal, used to connect to an external power source; A rectifier circuit, wherein the input terminal of the rectifier circuit is connected to the external power supply connection terminal; The main driver board is used to generate multiple drive signals with different phases. Multiple sub-drive boards are electrically connected to the main drive board in a one-to-one correspondence. Each sub-drive board is used to receive one of the drive signals output by the main drive board. Multiple inverter circuits, the input terminals of which are respectively connected to the output terminal of the rectifier circuit; Each inverter circuit includes multiple power half-bridges, the output terminals of the multiple power half-bridges are shorted to form a single-phase bridge arm, and each inverter circuit is connected to a corresponding sub-drive board. The sub-drive board is used to simultaneously distribute one of the drive signals received from the main drive board to the multiple power half-bridges. A current calculation circuit, the input terminal of which is connected to the current detection terminals of the plurality of power half-bridges respectively, is used to add the branch currents of the plurality of power half-bridges to synthesize the total single-phase bridge arm current of the inverter circuit. An analog sampling board, the input terminals of which are respectively connected to the output terminals of each of the current calculation circuits, is used to collect the analog signal of the total current of a single-phase bridge arm synthesized by multiple inverter circuits; A control circuit, the input of which is connected to the output of the analog sampling board, and the output of which is connected to the main drive board, is used to adjust the multi-channel drive signals output by the main drive board according to the received analog signals of the total current of the multiple single-phase bridge arms.

2. The parallel operation control device for a frequency changer as claimed in claim 1, wherein The inverter parallel operation control device also includes a DC bus; The first end of the DC bus is connected to the output end of the rectifier circuit, and the second end of the DC bus is connected to the input ends of the plurality of inverter circuits.

3. The inverter parallel operation control device as described in claim 2, characterized in that, The inverter parallel control device includes at least one of the inverter circuits.

4. The inverter parallel operation control device as described in claim 3, characterized in that, At least one of the inverter circuits includes a first inverter circuit, a second inverter circuit, and a third inverter circuit; The input terminals of the first inverter circuit, the second inverter circuit, and the third inverter circuit are connected in parallel with the DC bus. The first inverter circuit is used to output U-phase current, the second inverter circuit is used to output V-phase current, and the third inverter circuit is used to output W-phase current.

5. The inverter parallel operation control device as described in claim 1, characterized in that, The input terminal of the analog sampling board is connected to the rectifier circuit to collect the input current of the rectifier circuit and transmit the collected signal to the control circuit.

6. The inverter parallel operation control device as described in claim 1, characterized in that, The current calculation circuit includes an adder circuit; The input terminal of the adder circuit is connected to the current detection terminal of the power half-bridge. The adder circuit is used to perform an addition operation on the analog current signal corresponding to the current detection terminal, and output the analog signal of the total current of the single-phase bridge arm to the analog quantity sampling board.

7. The inverter parallel operation control device as described in claim 6, characterized in that, The analog sampling board includes an analog-to-digital converter; The analog-to-digital converter is used to convert the analog signal of the total current of the single-phase bridge arm into a digital signal and transmit the digital signal to the control circuit.

8. The inverter parallel operation control device as described in claim 7, characterized in that, The control circuit uses a DSP chip, which adjusts the duty cycle of the PWM signal output to the main drive board based on the digital signal to control the inverter circuit.

9. The inverter parallel operation control device as described in claim 1, characterized in that, The main drive board and the multiple sub-drive boards are connected by optical fibers; The sub-drive board is electrically connected to the corresponding inverter circuit and transmits drive signals.

10. A frequency converter parallel operation control system, characterized in that, Includes the inverter parallel operation control device as described in any one of claims 1 to 9.

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