Cascade type high-pressure molten salt induction heater power supply and control system thereof

Abstract

The utility model relates to a cascaded high-voltage molten salt induction heater power supply and a control system thereof, and belongs to the field of power electronics. The power supply is used for providing sinusoidal voltage with selectable frequency, adjustable amplitude and higher than 98% of fundamental wave content for the high-voltage molten salt induction heater, and comprises a phase-shifting transformer and a plurality of power units, output positive and negative buses of each power unit are in cascade connection and then are connected with the high-voltage molten salt induction heater, and the high-voltage molten salt induction heater can be heated by changing the cascade number of the power units. And appropriate rated voltage can be provided for the high-voltage molten salt induction heater. The control system comprises a temperature detection device, a voltage and current detection device, a PECS controller, a PLC controller, a human-computer interface controller and a power unit control panel. The power unit is electrically connected with the power unit control board, and the control system controls the power unit through the power unit control board.

Description

Technical Field

[0001] The utility model belongs to the field of power electronics and relates to a cascade type high-voltage molten salt induction heater power supply and a control system thereof. Background Art

[0002] Molten salt heat storage technology is being widely used in solar thermal power stations, thermal power flexibility transformation, and industrial steam supply. Molten salt heating is an important part of the molten salt heat storage system. At present, the market mostly uses molten salt electric heating technology, and most of them are low-voltage equipment of 380 or 690V, and they are used in occasions with large power requirements. Low-voltage systems have problems of low efficiency and short system life. Therefore, high-voltage electromagnetic induction heaters are introduced on the market, which have the significant advantages of high efficiency and long life. In order to meet the controllable and adjustable temperature of the heated molten salt, the high-voltage molten salt induction heater needs to be equipped with a high-voltage power supply with adjustable output power and low harmonic content. The current power and voltage regulating power supply mostly adopts thyristor series topology. This topology has the disadvantages of large grid-side harmonics and low power factor, and usually cannot meet the grid quality requirements. Utility Model Content

[0003] In view of this, the purpose of the utility model is to provide a cascade high-voltage molten salt induction heater power supply and a control system thereof, so as to achieve the effect of input directly connected to the high-voltage power grid, harmonics and power factor meeting the quality requirements of the power grid, high output voltage level, infinitely adjustable power, and low current harmonics; and provide human-computer interaction with simple control and concise operation.

[0004] In order to achieve the above-mentioned purpose, the utility model proposes a cascaded high-voltage molten salt induction heater power supply on the one hand, which is used to provide a sinusoidal voltage with optional frequency, adjustable amplitude and fundamental content higher than 98% to the high-voltage molten salt induction heater, which includes a phase-shifting transformer and a plurality of power units. The input side of the phase-shifting transformer is connected to the power grid or generator, and the output side is connected to the three-phase input side of each power unit to supply power to the power unit; the output positive and negative busbars of each power unit are cascaded, and the three-phase output side of the power unit cascade is connected to the high-voltage molten salt induction heater, thereby providing a three-phase output voltage with a variable amplitude for the high-voltage molten salt induction heater. By changing the cascade number n of the power unit cascade, a suitable rated voltage can be provided for the high-voltage molten salt induction heater, and the number of power units is equal to three times the cascade number n, that is, N=3*n, where N represents the number of power units.

[0005] Optionally, the power unit includes an uncontrolled rectifier bridge, a DC-Link and an inverter bridge, wherein the uncontrolled rectifier bridge, the DC-Link and the inverter bridge are connected in sequence.

[0006] On the other hand, the utility model proposes a control system for a cascade high-voltage molten salt induction heater power supply, which includes a temperature detection device, a voltage and current detection device, a PECS controller, a PLC controller, a human-machine interface controller and a power unit control board.

[0007] The temperature detection device, the voltage and current detection device and the power unit control board are respectively connected to the PECS controller signal; the PECS controller, the PLC controller and the human-machine interface controller are respectively connected to the industrial switch signal; the power unit control board is also connected to the power unit.

[0008] Optionally, the power unit control board includes a power supply module, a signal detection module, a CPLD and a driver board. The power supply module is respectively connected to the signal detection module, the CPLD and the driver board; the signal detection module is connected to the power unit; the CPLD is respectively connected to the signal detection module, the PECS controller and the driver board; and the driver board is also connected to the power unit.

[0009] Optionally, the temperature detection device, the voltage and current detection device and the power unit control board are respectively connected to the PECS controller signal via optical fibers.

[0010] Optionally, the PECS controller, PLC controller and human-machine interface controller are respectively connected to the industrial switch signal via a network cable.

[0011] The beneficial effects of the utility model are as follows: the cascaded high-voltage molten salt induction heater power supply proposed in the utility model has the voltage level expansion capability, can achieve a rated output voltage of 6kV to 13.8kV, grid-side current harmonics <3%, power factor >0.97, and meet the grid-side power quality; at the same time, the utility model is easy to control and simple to operate, and realizes comfortable human-computer interaction through the visualization of equipment status and historical fault information.

[0012] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and will be apparent to those skilled in the art based on the following examination and research, or can be taught from the practice of the present invention to some extent. The objectives and other advantages of the present invention can be achieved and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be described in detail below in conjunction with the accompanying drawings, in which:

[0014] Figure 1 It is a schematic diagram of the structure of a cascade high-voltage molten salt induction heating power supply;

[0015] Figure 2is a schematic diagram of the power unit structure;

[0016] Figure 3 It is a structural block diagram of the control system of the cascade high-voltage molten salt induction heating power supply;

[0017] Figure 4 It is a schematic diagram of the structure of the temperature, voltage and current detection device.

[0018] Figure numerals: 1-power unit; 2-temperature detection device; 3-voltage and current detection device; 4-PECS controller; 5-PLC controller; 6-industrial switch; 7-human-machine interface controller; 8-optical fiber; 9-network cable; 10-power unit control board. DETAILED DESCRIPTION

[0019] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. The following embodiments and the features in the embodiments can be combined with each other without conflict.

[0020] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present utility model. In order to better illustrate the embodiments of the present utility model, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0021] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0022] The utility model proposes a cascade type high voltage molten salt induction heater power supply and control system thereof, and its power supply structure is as follows Figure 1The power supply mainly includes a phase-shifting transformer and N power units, wherein the input side of the phase-shifting transformer is connected to the power grid, and the output side is connected to the three-phase input side of the N power units, and the output positive and negative busbars of the power units are cascaded to each other, and the three-phase output side of the cascaded power unit is connected to the molten salt induction heating power supply.

[0023] Among them, the power unit structure is as follows Figure 2 As shown, it includes an uncontrolled rectifier bridge, a DC-Link and an inverter bridge. One end of the uncontrolled rectifier bridge is connected to the input side of the power unit, and the other end is connected to the DC-Link. The other end of the DC-Link is connected to the inverter bridge, and the other end of the inverter bridge serves as the output side of the power unit.

[0024] In the utility model, the control system for the cascade molten salt induction heater power supply is as follows Figure 3 As shown, it mainly includes a temperature detection device 2, a voltage and current detection device 3, a PECS controller 4, a PLC controller 5, a switch 6, a human-machine interface controller 7 and a power unit control board 10, and also includes an optical fiber 8 and a network cable 9 for realizing information transmission.

[0025] Among them, the power unit 1 is connected to the power unit control board 10; the temperature detection device 2, the voltage and current detection device 3 and the power unit control board 10 are respectively connected to the PECS controller 4 signal through the optical fiber 8; the PECS controller 4, the PLC controller 5 and the human-machine interface controller 7 are respectively connected to the industrial switch 6 signal through the network cable 9.

[0026] The temperature detection device 2 and the voltage and current detection device 3 are used to detect the temperature and voltage and current information of the power unit respectively. Figure 4 As shown, the temperature detection device 2 and the voltage and current detection device 3 first amplify the received analog signal through the amplifier circuit, and then convert the analog voltage and current signal into a pulse signal of corresponding frequency through the voltage-frequency conversion chip, and transmit it to the PECS controller 4 through the optical fiber 8. The function of the optical fiber 8 is to achieve safe isolation between the high-voltage system and the low-voltage control system.

[0027] The PECS controller 4 is based on FPGA+DSP, has optional communication ports, supports various common industrial communication protocols, and has 24 pairs of programmable optical fiber I / O interfaces. The optional FPGA model is Cyclone V-5CEBA4F23C8, and the optional DSP model is TMS320C28346. The controller includes functions such as signal processing, target voltage calculation, and drive signal generation.

[0028] The signal processing function of the PECS controller 4 refers to processing the optical fiber signals from the temperature detection device 2, the voltage and current detection device 3 and the power unit control board 10 respectively, wherein the optical fiber signal of the temperature detection device 2 is processed to obtain the temperature information of the three-phase pipeline of the molten salt heater, the optical fiber signal of the voltage and current detection device 3 is processed to obtain the corresponding actual voltage and current, and the optical fiber signal of the power unit control board 10 is processed to obtain the corresponding unit bus voltage, the actual operating temperature of the unit and the unit fault status information.

[0029] The target voltage calculation function of the PECS controller 4 refers to selecting the feedback signal according to the target mode set by the human-machine interface controller 7. Specifically, in the constant temperature mode, the feedback signal takes three-way temperature; in the constant current mode, the feedback signal takes three-phase current; in the constant power mode, the feedback signal takes three-phase power. The difference between the control target received by the human-machine interface and the average value of the three-phase feedback signal is input to the PI regulator, and the PI regulator outputs the reference value of the target voltage; the difference between the control target and the feedback signal of each phase is input to the PI regulator, and the PI regulator outputs the adjustment value of the target voltage of each phase.

[0030] The driving signal generation function of the PECS controller 4 refers to calculating the PWM pulse according to the SPWM pulse width modulation algorithm based on the calculated target voltage, encoding the PWM pulse and sending it to the optical fiber port of the PECS controller 4 connected to the power unit control board 10, and transmitting it to the power unit control board 10.

[0031] The PECS controller 4, PLC controller 5 and human-machine interface controller 7 exchange information via the Modbus TCP protocol. The human-machine interface controller 7 is used to input parameters and control commands, as well as display power status, unit fault status and operation results. The PLC controller 5 is used to realize the communication connection between the human-machine interface controller 7 and the PECS controller 4. In addition, the PLC controller 5 is also used for start-stop, fault control, and external communication expansion.

[0032] The PECS controller 4 completes control, protection and other functions according to the input information of the PLC controller 5 and the human-machine interface controller 7, and outputs information such as power, voltage, current, and equipment status to the PLC controller 5 and the human-machine interface controller 7.

[0033] The power unit control board 10 includes a power supply module, a signal detection module, a programmable logic device (CPLD) and a driver board; wherein the signal detection module collects the DC voltage, power device temperature, and fault information of the power unit (such as unit board power failure, optical fiber communication failure, IGBT failure, power unit DC bus overvoltage and undervoltage failure, IGBT overtemperature failure, etc.); the CPLD is used to process the detection signal and encode it and send it to the optical fiber port of the power unit control board 10. The CPLD is also used to decode the optical fiber signal sent by the PECS controller 4 and generate an electrical signal for the driver board, wherein the CPLD can use MAXII EPM570; the driver board sends the generated electrical signal to the power switch element of the power unit to control the opening and closing of the power switch, wherein the driver board can be driven by FAST PM120.

[0034] The PLC controller 5 adopts Siemens smart200 controller, and can use ModbusTCP protocol to connect with multiple PECS controllers through network switches and network cables for collaborative control; it can also use network cables to achieve remote connection with industrial field control systems through network ports, or use twisted pair cables or shielded cables to achieve remote connection with industrial field control systems through 485 interfaces for remote control and status display.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the utility model.

Claims

1. A cascade high-voltage molten salt induction heater power supply, Features: It comprises a phase-shifting transformer and a plurality of power units (1); the input side of the phase-shifting transformer is connected to a power grid or a generator, and the output side thereof is connected to the three-phase input side of each of the power units (1); the output positive and negative busbars of the power units (1) are connected in cascade, and the three-phase output side of the cascaded power units (1) is connected to a high-voltage molten salt induction heater, thereby providing the high-voltage molten salt induction heater with a three-phase output voltage of varying amplitude.

2. The cascade high-voltage molten salt induction heater power supply according to claim 1, Features: The power unit (1) comprises an uncontrolled rectifier bridge, a DC-LINK and an inverter bridge which are connected in sequence, wherein the uncontrolled rectifier bridge serves as the input side of the power unit (1) and the inverter bridge serves as the output side of the power unit (1).

3. The cascade type high voltage molten salt induction heater power supply according to claim 1, Features: By changing the cascade number n of the power units (1), a suitable rated voltage is provided for the high-voltage molten salt induction heater.

4. The cascade high-voltage molten salt induction heater power supply according to claim 3, Features: The number of the power units (1) is equal to three times the cascade number n, that is, N=3*n, where N represents the number of the power units (1).

5. A control system for a cascade type high voltage molten salt induction heater power supply as claimed in any one of claims 1 to 4, Features: The control system comprises a temperature detection device (2), a voltage and current detection device (3), a PECS controller (4), a PLC controller (5), a human-machine interface controller (7) and a power unit control board (10); The temperature detection device (2), the voltage and current detection device (3) and the power unit control board (10) are respectively connected to the PECS controller (4) by signal; the PECS controller (4), the PLC controller (5) and the human-machine interface controller (7) are respectively connected to the industrial switch (6) by signal; the power unit control board (10) is also connected to the power unit (1); The power unit control board (10) comprises a power supply module, a signal detection module, a CPLD and a drive board; the power supply module is connected to the signal detection module, the CPLD and the drive board respectively; the signal detection module is connected to the power unit (1); the CPLD is connected to the signal detection module, the PECS controller (4) and the drive board respectively; the drive board is also connected to the power unit (1).

6. The control system according to claim 5, Features: The temperature detection device (2), the voltage and current detection device (3) and the power unit control board (10) are respectively connected to the PECS controller (4) by signals via optical fibers (8).

7. The control system according to claim 5, Features: The PECS controller (4), the PLC controller (5) and the human-machine interface controller (7) are respectively connected to the industrial switch (6) by signals via a network cable (9).

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