Multi-machine parallel control system and method for direct-current power supply

Abstract

The invention discloses a multi-machine parallel control system and method for direct-current power supplies, the system comprises a plurality of direct-current sources, one direct-current source is set as a host, the other direct-current sources are set as slaves, each of the host and the slaves comprises two CAN communication ports and two pairs of LVDS communication ports, and the CAN communication ports of the host and the slaves are connected through a CAN communication bus; one pair of LVDS communication ports of the host and each slave are connected in series, and the other pair of LVDS communication ports of the host and each slave are also connected in series; the CAN communication port is used for transmitting common parameters in the system, one pair of LVDS communication ports is used for transmitting a reference value sent by a host to a slave, and the other pair of LVDS communication ports is used for the host to send a synchronizing signal to the slave; the invention has the advantages of high transmission rate and low design cost.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to a multi-machine parallel control system and method for a direct current power supply. Background Art

[0002] Currently, in areas requiring DC power supplies, distributed desktop DC power supplies with higher power density and smaller footprints are preferred. However, these DC power sources typically have low power output (<40 kW). Therefore, in high-power applications, multiple DC power sources must be connected in parallel to form a distributed power supply test system to output higher power and current. However, since the output impedance and output voltage of each DC power source in this parallel system cannot be completely consistent, direct parallel connection can result in unbalanced loads. Devices with significantly different external characteristics will carry more current, and even cause circulating current between devices, potentially affecting the protection of individual devices or even damaging them. Therefore, a multi-device parallel control method is needed to achieve coordinated operation and current sharing among the devices. The most commonly used method is a master-slave configuration, where one device is designated as the master and the others as slaves. The master sets the voltage setpoint for the entire distributed system, and the remaining slaves follow the master's instructions. Voltage and current setpoints, protection levels, setpoint thresholds, and other parameters must be communicated between the master and slaves, and current sharing measures are also required. There are generally two ways to perform current sharing control. One is to use hardware to connect the current sharing control signal and add a communication connection to perform multi-machine parallel control. For example, Chinese Patent Publication No. CN114024301A discloses a DC power supply parallel system and current sharing control method. The second is to use only a communication connection to perform multi-machine parallel control, that is, remove the current sharing control signal and only perform multi-machine parallel control.

[0003] Regarding the two parallel control methods mentioned above, the first, "hardware current sharing signal connection + communication connection," places high demands on the interference resistance of the current sharing control signal and the hardware current sharing sampling circuit. Improper handling can easily lead to suboptimal current sharing control. In DC power supply systems with bidirectional energy flow, this can easily cause circulating currents between machines, affecting the stability of the entire system. The second, "communication connection only," generally uses CAN communication, RS485 serial communication, or Gigabit Ethernet communication. The former two are characterized by simple and reliable design but low transmission rates. In high-power-density distributed power supplies, due to the high switching frequency, the former two communication rates are insufficient to transmit loop control parameters with strict time response requirements. While the latter communication method effectively solves the transmission rate issue, Gigabit Ethernet communication requires optoelectronic conversion circuits, which imposes high design costs and development cycles. Summary of the Invention

[0004] The technical problem to be solved by the present invention is how to solve the problems of low transmission rate and high design cost in the existing communication method for parallel control of multiple DC power supplies.

[0005] The present invention solves the above technical problems through the following technical means: a multi-machine parallel control system of a DC power supply, comprising multiple DC sources, one of which is set as a master, and the other DC sources are set as slaves, the master and the slave each comprising two CAN communication ports and two pairs of LVDS communication ports, the CAN communication ports of the master and each slave being connected via a CAN communication bus; one pair of LVDS communication ports of the master and each slave being connected in series, and the other pair of LVDS communication ports also being connected in series; the CAN communication port is used to transmit common parameters within the system, a pair of LVDS communication ports transmits reference values ​​sent by the master to the slave, and the other pair of LVDS communication ports is used for the master to send synchronization signals to the slave.

[0006] The hardware circuit design of the present invention is simple. Compared with Gigabit Ethernet transmission, which requires an optical module, a photoelectric conversion circuit, and a high-speed transmission circuit within a single machine, it not only reduces hardware costs but also saves software development cycles. At the same time, to compensate for the problem of insufficient transmission rate, all signals that need to be transmitted are separated. Important loop control signals (reference values ​​and synchronization signals) are transmitted via LVDS, while other signals that do not require high-speed transmission (system common parameters) are transmitted via CAN or other low-speed communication ports, thereby achieving fast loop response and high transmission rate.

[0007] Furthermore, the CAN communication ports of the host and each slave are connected via a CAN communication bus, including:

[0008] A CAN communication port of the host is connected to a CAN communication port of a slave through a bus, and another CAN communication port of the slave is connected to a CAN communication port of the next slave through a bus, so that the host and each slave are connected in sequence through the CAN communication bus.

[0009] Furthermore, the common parameters in the system include set values ​​of voltage, current and power, thresholds, protection values, slopes and delay times sent by the host.

[0010] Furthermore, the process of transmitting the shared parameters in the system via the CAN communication port is as follows:

[0011] The host sets the set values ​​of voltage, current and power, thresholds, protection values, slopes and delay times, and reads the status signals and fault signals reported by each slave, and then broadcasts them to each slave.

[0012] Furthermore, the host and the slave both include an LVDS signal transceiver circuit, which includes a bidirectional differential transceiver, two single-pole double-throw switches, a logic level converter, three digital isolators and a DSP chip. The two pairs of LVDS communication ports are respectively connected to the two pairs of signal transceiver ports of the bidirectional differential transceiver, the two data transmission ports of the bidirectional differential transceiver are each connected to the common port of a single-pole double-throw switch, the enable port of the bidirectional differential transceiver is connected to the 1A port of the logic level converter and the Vout_a port of a digital isolator, the Vout_b port of the digital isolator is connected to the enable end of the DSP chip, the 1Y port of the logic level converter is connected to the enable ports of the two single-pole double-throw switches, the output end of one single-pole double-throw switch is connected to the signal transmission port of the DSP chip through another digital isolator, and the output end of another single-pole double-throw switch is connected to the synchronization signal port of the DSP chip through another digital isolator.

[0013] The present invention also provides a method for a multi-machine parallel control system of a DC power supply, wherein the host sends common parameters in the system to each slave through a CAN communication port, and the host sends a reference value and a synchronization signal to the first slave through an LVDS communication port. The first slave forwards the signal to the second slave, and the second slave forwards the signal to the third slave, and the LVDS signals sent by the host are transmitted serially in sequence.

[0014] Furthermore, the stand-alone working process of the host is:

[0015] The host obtains the voltage outer loop output value based on the output voltage command value and the output voltage feedback value. The voltage outer loop output value of the host is limited and then subtracted from the output current feedback value received by the host. The difference is input into the first PI regulator. The output result of the first PI regulator is subtracted from the input voltage feedback value of the host's converter to generate a first PWM wave. The first PWM wave controls the power switch of the host's converter.

[0016] Furthermore, the process of obtaining the voltage outer loop output value is as follows:

[0017] The output voltage command value of the host is subtracted from the output voltage feedback value received by the host, and the difference is input into the second PI regulator. The output result of the second PI regulator is limited and subtracted from the output current feedback value received by the host to obtain the voltage outer loop output value.

[0018] Furthermore, the standalone working process of the slave is as follows:

[0019] The difference between the current reference value of the slave and the current baseline value of the slave is limited and then the difference is input into the third PI regulator. The output result of the third PI regulator is subtracted from the input voltage feedback value of the converter of the slave to generate a second PWM wave. The second PWM wave controls the power switch of the converter of the slave.

[0020] Furthermore, the current reference value of the slave is obtained as follows:

[0021] The voltage outer loop output value of the master is compared with the calibration table value and the set threshold value, and the minimum value of the three is selected as the current reference value of the slave.

[0022] The advantages of the present invention are:

[0023] (1) The hardware circuit design of the present invention is simple. Compared with Gigabit Ethernet transmission, which requires optical modules, photoelectric conversion circuits, and high-speed transmission circuits within a single machine, it not only reduces hardware costs but also saves software development cycles. At the same time, in order to compensate for the problem of insufficient transmission rate, all signals that need to be transmitted are separated. Important loop control signals (reference values ​​and synchronization signals) are transmitted via LVDS, and the remaining signals that do not require high-speed transmission (system common parameters) are transmitted via CAN or other low-speed communication ports, thereby achieving fast loop response and high transmission rate.

[0024] (2) When a single machine is working, the reference of the current inner loop of the present invention comes from the voltage outer loop of the single machine. When multiple machines are working in parallel, the reference value of the current inner loop of the slave machine adopts the reference value sent by the host machine through the LVDS signal, and another pair of LVDS signals sends a synchronization signal to the slave machine, thereby ensuring that the current of each machine is balanced and the changes are synchronized during startup, shutdown, steady state, and dynamic state. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic structural diagram of a multi-machine parallel control system for a DC power supply disclosed in an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a single-machine working mode in a multi-machine parallel control system of a DC power supply disclosed in an embodiment of the present invention, wherein: Figure 2 (a) is a schematic diagram of the host's stand-alone working mode system structure. Figure 2 (b) is a schematic diagram of the system structure of the slave in standalone working mode. Figure 2 (c) Schematic diagram of a master and slave sharing a system and switching through a 2-to-1 selector;

[0027] Figure 3 A schematic diagram of an LVDS signal transceiver circuit in a multi-machine parallel control system of a DC power supply disclosed in an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the LVDS signal working timing of the master and each slave in a multi-machine parallel control system of a DC power supply disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a multi-machine parallel control system of a DC power supply, including multiple DC sources, one of which is set as a master, and the other DC sources are set as slaves. The master and the slave each include two CAN communication ports and two pairs of LVDS communication ports. One CAN communication port of the master is connected to one CAN communication port of a slave through a bus, and another CAN communication port of the slave is connected to one CAN communication port of the next slave through a bus, so that the master and each slave are connected in sequence through the CAN communication bus; one pair of LVDS communication ports of the master and each slave are connected in series, and the other pair of LVDS communication ports are also connected in series.

[0031] This embodiment divides parallel multi-machine control into two parts. One part uses CAN communication to transmit shared parameters within the system. For example, the master sends voltage, current, and power setpoints, thresholds, protection values, slopes, delay times, and so on. It also reads various status signals and fault signals reported by the slaves. The master then comprehensively processes and broadcasts these signals to each slave. In this embodiment, CAN communication is used to handle this part.

[0032] The other part of the multi-machine parallel control is used to transmit the key control parameters of the current sharing control. In this embodiment, LVDS high-speed signals are used to replace the ordinary CAN, RS485, and Gigabit Ethernet signals. Here, for example, the control loop uses PI control, the operating frequency is 70kHz, and the multi-machine parallel operation is in constant voltage source mode. The LVDS signal takes 10Mbps. Figure 2 As shown, when a single machine is working, the reference of the current inner loop comes from the voltage outer loop of the single machine, while when multiple machines are working in parallel, the reference of the current inner loop of the slave machine is switched to the reference value sent by the host through the LVDS signal ( Figure 2MUX2 is a 2-to-1 function), and another pair of LVDS signals sends synchronization signals to the slave devices, thereby ensuring current balance and synchronization of each device during startup, shutdown, steady state, and dynamic conditions.

[0033] The above two communication methods are combined to realize signal transmission and reception between the host and the slave. The host sends the common parameters in the system to each slave through the CAN communication port. The host sends the reference value and synchronization signal to the first slave through the LVDS communication port. The first slave forwards it to the second slave, and the second slave forwards it to the third slave, and the LVDS signals sent by the host are transmitted serially in sequence.

[0034] Continue reading Figure 2 The control systems of the host and the slave can use the same system, which is switched through the 2-to-1 selector MUX2. When the upper path is selected, it is the stand-alone working process of the host, and when the lower path is selected, it is the stand-alone working process of the slave. Figure 2 (a) is a schematic diagram of the host's stand-alone working mode system structure. Figure 2 (b) is a schematic diagram of the system structure of the slave in standalone working mode. Figure 2 (c) is a diagram showing a master and slave sharing a system and switching between them via a 2-to-1 selector. The following describes the standalone operation modes of the master and slave.

[0035] See Figure 2 (a) The single-machine working process of the host is:

[0036] The host's output voltage command value, Uoc, is subtracted from the host's received output voltage feedback value, UO_fb. This difference is fed into a PI regulator. The PI regulator's output is clipped and subtracted from the host's received output current feedback value, IO_fb, to produce the voltage outer loop output value. The host's voltage outer loop output is clipped and subtracted from the host's received output current feedback value, IO_fb. This difference is fed into another PI regulator. The PI regulator's output is subtracted from the host's converter's input voltage feedback value, Uin, to generate a PWM wave that controls the host converter's power switches.

[0037] See Figure 2 (b) The single-machine working process of the slave is:

[0038] The master's voltage outer loop output is compared with the calibration table value and the set threshold value, and the minimum of the three is selected as the slave's current reference value. The slave's current reference value is subtracted from the slave's current reference value IO_ref, which is then clipped and then subtracted from the slave's output current feedback value. This difference is input into a PI regulator. The PI regulator's output is subtracted from the input voltage feedback value of the slave's converter to generate a PWM wave, which controls the slave's converter's power switch.

[0039] like Figure 3 As shown, the host and the slave both include an LVDS signal transceiver circuit, which includes a bidirectional differential transceiver (Bi-Dir Differential Transceiver), two single-pole double-throw switches (SPDT Switch), a logic level converter (Signal Transceiver), three digital isolators (Digital Isolators) and a DSP chip. The two pairs of LVDS communication ports are respectively connected to the two pairs of signal transceiver ports of the bidirectional differential transceiver, the two data transmission ports of the bidirectional differential transceiver are each connected to the common port of a single-pole double-throw switch, the enable port of the bidirectional differential transceiver is connected to the 1A port of the logic level converter and the Vout_a port of a digital isolator, the Vout_b port of the digital isolator is connected to the enable end of the DSP chip, the 1Y port of the logic level converter is connected to the enable ports of the two single-pole double-throw switches, the output end of one single-pole double-throw switch is connected to the signal transmission port of the DSP chip through another digital isolator, and the output end of another single-pole double-throw switch is connected to the synchronization signal port of the DSP chip through another digital isolator. Figure 3 A single-pole double-throw switch is used via a logic level converter to connect either the RF_a port or the RF_b port, switching between signal reception and transmission. For example, when RF_a is connected, both LVDS communication ports of the current machine receive external signals, namely, reference values ​​and synchronization signals. When RF_b is connected, the current machine transmits external signals, namely, reference values ​​and synchronization signals. The above circuit implements a transceiver circuit for LVDS control parameter transmission after master and slave device configuration. Compared to the optical modules, optoelectronic conversion circuits, and high-speed transmission circuits required for Gigabit Ethernet transmission, this reduces both hardware costs and software development cycles. Furthermore, to compensate for the slower LVDS transmission speed compared to Gigabit Ethernet, all signals requiring transmission are separated. Important loop control signals are transmitted via LVDS, while other signals that do not require high-speed transmission are transmitted via CAN or other low-speed communication ports.

[0040] like Figure 4 As shown, the present invention was tested in a system operating at 70kHz using a 10Mbps LVDS signal with four parallel devices. The LVDS transmission line from the master to the last slave device was over 4 meters (AWG 22 wire). The actual LVDS signal transmission delay between each device was only 30ns, and the LVDS differential signal conversion delay within each device was 30ns. This corresponds to an operating frequency of several hundred kHz and a loop response bandwidth of 1k-10kHz. This has no impact on power supplies controlled by LVDS transmission control parameters within 100-200 bits, and the overall anti-interference capability is also excellent.

[0041] Through the above technical solution, the present invention has a simpler hardware circuit design, lower cost, and shorter software and hardware development cycle than Gigabit Ethernet design. The transmission speed is faster than CAN communication and RS485 communication, and the anti-interference ability is stronger than analog signal transmission. It is suitable for applications with high operating frequency, fast loop response, and a large number of parallel machines.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A multi-machine parallel control system for a DC power supply, characterized in that: The system includes multiple DC sources, one of which is set as a host and the other DC sources are set as slaves. The host and the slave each include two CAN communication ports and two pairs of LVDS communication ports. The CAN communication ports of the host and each slave are connected through a CAN communication bus; one pair of LVDS communication ports of the host and each slave are connected in series, and the other pair of LVDS communication ports are also connected in series; the CAN communication port is used to transmit common parameters within the system, one pair of LVDS communication ports transmits reference values ​​sent by the host to the slave, and the other pair of LVDS communication ports is used for the host to send synchronization signals to the slave.

2. A multi-machine parallel control system for a DC power supply according to claim 1, characterized in that: The CAN communication ports of the host and each slave are connected via a CAN communication bus, including: A CAN communication port of the host is connected to a CAN communication port of a slave through a bus, and another CAN communication port of the slave is connected to a CAN communication port of the next slave through a bus, so that the host and each slave are connected in sequence through the CAN communication bus.

3. The multi-machine parallel control system of a DC power supply according to claim 1, characterized in that: The common parameters in the system include the set values ​​of voltage, current and power, thresholds, protection values, slopes and delay times issued by the host.

4. A multi-machine parallel control system for a DC power supply according to claim 3, characterized in that: The process of transmitting shared parameters in the CAN communication port is as follows: The host sets the set values ​​of voltage, current and power, thresholds, protection values, slopes and delay times, and reads the status signals and fault signals reported by each slave, and then broadcasts them to each slave.

5. The multi-machine parallel control system of a DC power supply according to claim 1, characterized in that: The host and the slave both include an LVDS signal transceiver circuit, which includes a bidirectional differential transceiver, two single-pole double-throw switches, a logic level converter, three digital isolators, and a DSP chip. The two pairs of LVDS communication ports are respectively connected to the two pairs of signal transceiver ports of the bidirectional differential transceiver, the two data transmission ports of the bidirectional differential transceiver are each connected to the common port of a single-pole double-throw switch, the enable port of the bidirectional differential transceiver is connected to the 1A port of the logic level converter and the Vout_a port of a digital isolator, the Vout_b port of the digital isolator is connected to the enable end of the DSP chip, the 1Y port of the logic level converter is connected to the enable ports of the two single-pole double-throw switches, the output end of one single-pole double-throw switch is connected to the signal transmission port of the DSP chip through another digital isolator, and the output end of another single-pole double-throw switch is connected to the synchronization signal port of the DSP chip through another digital isolator.

6. The method for controlling a multi-machine parallel control system of a DC power supply according to any one of claims 1 to 5, characterized in that: The host sends the common parameters in the system to each slave through the CAN communication port. The host sends the reference value and synchronization signal to the first slave through the LVDS communication port. The first slave forwards it to the second slave, and the second slave forwards it to the third slave, and the LVDS signals sent by the host are transmitted serially in sequence.

7. The method for controlling a multi-machine parallel control system of a DC power supply according to claim 6, characterized in that: The stand-alone working process of the host is: The host obtains the voltage outer loop output value based on the output voltage command value and the output voltage feedback value. The voltage outer loop output value of the host is limited and then subtracted from the output current feedback value received by the host. The difference is input into the first PI regulator. The output result of the first PI regulator is subtracted from the input voltage feedback value of the host's converter to generate a first PWM wave. The first PWM wave controls the power switch of the host's converter.

8. The method for controlling a multi-machine parallel control system of a DC power supply according to claim 7, characterized in that: The process of obtaining the voltage outer loop output value is as follows: The output voltage command value of the host is subtracted from the output voltage feedback value received by the host, and the difference is input into the second PI regulator. The output result of the second PI regulator is limited and subtracted from the output current feedback value received by the host to obtain the voltage outer loop output value.

9. The method for controlling a multi-machine parallel control system of a DC power supply according to claim 8, characterized in that: The standalone working process of the slave is as follows: The difference between the current reference value of the slave and the current baseline value of the slave is limited and then the difference is input into the third PI regulator. The output result of the third PI regulator is subtracted from the input voltage feedback value of the converter of the slave to generate a second PWM wave. The second PWM wave controls the power switch of the converter of the slave.

10. The method for controlling a multi-machine parallel control system of a DC power supply according to claim 9, characterized in that: The current reference value of the slave is obtained as follows: The voltage outer loop output value of the master is compared with the calibration table value and the set threshold value, and the minimum value of the three is selected as the current reference value of the slave.

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