CN105490313A - A shared electronic load for AC and DC - Google Patents

Abstract

The present invention relates to an AC/DC shared electronic load, the AC/DC shared electronic load includes an AC/DC power unit, a DC/DC power unit, a DC/AC power unit, an AC input terminal and a DC input terminal; wherein, the AC/DC power The input terminal of the unit is connected to the AC input terminal; the input terminal of the DC/DC power unit is connected to the DC input terminal; the output terminals of the AC/DC power unit and the DC/DC power unit are connected to the DC bus, and the DC bus is connected to the DC/ The AC power unit is used to connect to the power grid; switches are respectively connected between the AC/DC power unit and the AC input terminal, and between the DC/DC power unit and the DC input terminal. The AC-DC shared electronic load proposed by the present invention can change the transmission of electric energy in the AC-DC power supply according to requirements, so that the applicability of the load is more comprehensive and has strong applicability.

Description

A shared electronic load for AC and DC

technical field

The invention relates to an AC-DC shared electronic load, which is suitable for the technical field of load access to an AC power grid.

Background technique

The load is an important part of the power supply system, and it is an important index to measure the quality of the power supply. Especially in the R&D and test experiments of power supply equipment, it is often necessary to use the load to match the AC and DC power supply equipment, and connect it between the output of the AC and DC power supply and the power grid. The DC power supply is fed back to the grid to simulate the actual working environment load. Most of the traditional loads are pure resistive loads, which easily cause the output energy of the power supply to be converted into heat energy in vain, which increases the R&D and testing costs of power supply equipment; there is also a DC electronic load, but the DC electronic load has low efficiency, harmonic This will lead to unbalanced feedback to the power grid, which will easily cause pollution to the power grid. Therefore, in order to make up for such defects, AC and DC output methods are often used to convert three-phase balanced AC power to the grid in the test of load access to the grid. , and cannot achieve flexible control of alternating current and direct current, resulting in a single work mode that can be implemented by the load, which is not conducive to testing complex alternating current and direct current power supplies.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and propose an AC-DC shared electronic load, which solves the problem of poor applicability when the load feeds back electric energy from the AC-DC power supply to the power grid for testing.

The present invention is achieved by the following scheme:

An AC-DC shared electronic load is characterized in that the AC-DC shared electronic load includes an AC/DC power unit, a DC/DC power unit, a DC/AC power unit, an AC input terminal, and a DC input terminal; wherein, the AC The input terminal of the /DC power unit is connected to the AC input terminal; the input terminal of the DC/DC power unit is connected to the DC input terminal; the output terminals of the AC/DC power unit and the DC/DC power unit are connected to the DC bus, and the DC bus is connected through The DC/AC power unit is used to connect to the power grid; wherein, switches are respectively connected between the AC/DC power unit and the AC input terminal, and between the DC/DC power unit and the DC input terminal.

Further, the circuit structure in the AC/DC power unit is a three-level single-phase full-bridge circuit; the circuit structure in the DC/DC power unit is a Buck-Boost circuit; the AC/DC power The circuit structure in the unit is a three-level full-bridge inverter circuit.

Further, the AC/DC power unit and its AC input end are also connected with an AC fuse, an LCL filter circuit and a pre-charging branch connected in parallel at both ends of the switch; the DC/DC power unit and its DC input end are also connected with a DC A fuse and a pre-charge branch connected in parallel across the switch.

Further, an LCL filter circuit, a circuit breaker and a fuse are also connected between the output end of the DC/AC power unit and the grid.

Further, the main control board adopted by the AC-DC shared electronic load is composed of a digital signal processor DSP complex programmable logic element CPLD and 2 digital signal processors DSP; wherein, the 2 digital signal processors DSP are respectively: logic The digital signal processing element LOGICDSP and the control signal processing CONTROLDSP are respectively connected to the corresponding ports of the complex programmable logic element CPLD; the AC/DC power unit, DC/DC power unit and DC/AC power unit are also connected with the complex programmable logic element CPLD Corresponding port connection

The beneficial effect of the present invention compared with prior art is:

The present invention proposes an electronic load shared by AC and DC, in which a DC/DC power unit, an AC/DC power unit and a DC/AC power unit are arranged respectively; The AC input terminal of the /DC power unit is connected to the AC power supply, and the obtained AC is rectified into DC; the DC input terminal of the DC/DC power unit is connected to the DC power supply, and the output terminals of the AC/DC power unit and the DC/DC power unit are connected On the busbar, the busbar is connected to the power grid through the DC/AC power unit, and the AC source and DC source output are converted into three-phase balanced electric energy and sent to the grid. The AC input terminal is connected to the AC/DC power unit and the DC input terminal is connected to the DC There are switches connected between the /DC power units, which can realize multiple application modes, that is, single-phase DC output, single-phase AC output and AC-DC output. The AC-DC shared electronic load proposed by the present invention can change the transmission of electric energy in the AC-DC power supply according to requirements, so that the applicability of the load is more comprehensive and has strong applicability.

Compared with the traditional load, the AC-DC shared load proposed by the present invention converts electric energy into thermal energy consumption and replaces the single-phase AC-DC power supply with single-phase unbalanced electric energy for transmission to the power grid, which has high transmission efficiency, low harmonic content, and reduced energy consumption. Etc.

Description of drawings

FIG. 1 is a schematic diagram of a shared AC/DC electronic load according to an embodiment of the present invention;

FIG. 2 is a circuit topology diagram of an AC/DC power unit according to an embodiment of the present invention;

3 is a circuit topology diagram of a DC/DC power unit according to an embodiment of the present invention;

4 is a circuit topology diagram of a DC/AC power unit according to an embodiment of the present invention;

5 is a general circuit topology diagram of a shared AC and DC electronic load according to an embodiment of the present invention;

6 is a control block diagram of an AC/DC power unit according to an embodiment of the present invention;

Fig. 7 is a control block diagram of a DC/DC power unit according to an embodiment of the present invention;

Fig. 8 is a control block diagram of a DC/AC power unit according to an embodiment of the present invention;

Fig. 9 is the control block diagram of the main control panel of the embodiment of the present invention;

Fig. 10 is the coordinated control and protection of AC/DC, DC/DC, and DC/AC power units according to the embodiment of the present invention.

Protection and communication block diagram.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

(1) An AC-DC shared electronic load

An AC-DC shared electronic load according to the present invention, as shown in Figure 1, the electronic load mainly includes: AC/DC power unit, DC/DC power unit, DC/AC power unit, AC input terminal and DC input terminal . Among them, the input end of the AC/DC power unit is connected to the AC input end; the input end of the DC/DC power unit is connected to the DC input end; the output end of the AC/DC power unit and the DC/DC power unit are connected to the DC bus , the DC bus is used to connect to the grid by connecting to the DC/AC power unit, so as to feed back the electric energy of the AC and DC power supply to the grid. Wherein, switches are respectively connected between the AC/DC power unit and the AC input terminal, and between the DC/DC power unit and the DC input terminal. The specific structure of each module is described in detail below:

1) AC/DC power unit: As shown in Figure 2, the circuit topology in the AC/DC power unit mainly adopts a three-level single-phase full-bridge circuit, and the AC input terminals L and N of the AC/DC power unit are respectively connected to Into the DC power supply, using three-level high-frequency PWM technology to rectify the single-phase AC to DC; at the AC input end of the AC/DC power unit, a fuse, a switch, and a pre-charging branch connected in parallel with the switch are connected, LCL filter circuit,

2) DC/DC power unit: As shown in Figure 3, the circuit topology in the DC/DC power unit adopts a Buck-Boost circuit structure. The Buck-Boost circuit structure in this embodiment mainly includes two IGBT elements and one The inductance element is: one end of the two IGBT elements is connected in series in sequence, and the other end is respectively connected to the positive end and the negative end of the DC bus, and the inductance element is connected to the connection point of the two IGBT elements; the DC input terminals DC+ and DC- are respectively connected to the DC power supply, and the output current of the DC power supply can be raised to the bus voltage through the Buck-Boost circuit in the DC/DC power unit. The input port of the DC/DC power unit is also connected with a DC fuse, a switch and a pre-charging branch connected in parallel with the switch.

3) DC/AC power unit: As shown in Figure 4, the circuit topology diagram in the DC/AC power unit mainly adopts the three-level neutral point clamp (NPC) circuit topology, and the input terminals DC+ and DC of the DC/AC power unit The - terminals are respectively connected to the positive and negative terminals of the busbar, and the output terminal of the DC/AC power unit is connected to the power grid through the LCL filter circuit, circuit breaker and fuse; the DC power supply and the AC power supply are respectively passed through the AC/DC power unit and DC/DC The power unit transmits the current to the DC/AC power unit through the bus bar, and the DC/AC power unit is converted into three-phase balanced AC through the "1" type three-level full bridge and fed back to the grid.

The DC/AC power unit in this embodiment adopts active power factor correction technology and active filtering technology, the power factor of the grid side can reach more than 0.999, and the current harmonic distortion rate is less than 3%, which will not cause harmonic pollution to the grid .

The specific working mode of the AC electronic shared load is as follows: the current is transmitted to the AC/DC power unit through the AC input terminal, and the AC is rectified into DC by the AC/DC power unit and transmitted to the bus; then the current is transmitted to the DC through the DC input terminal. /DC power unit, through the DC/DC power unit, the voltage is raised to the bus voltage and transmitted to the bus. The busbar converts the currents obtained from the AC input terminal and the DC input terminal respectively through the DC/AC power unit to the “1” type three-level full-bridge inverter into three-phase balanced AC power and feeds it back to the grid.

The present invention realizes three different application modes of the DC/AC load device by controlling the switch between the AC input end and AC/DC and the switch between the DC input end and DC/DC: 1) Single-phase AC output: turn on the AC/DC Switch at the DC power unit, turn off the switch at the DC/DC power unit; 2) Single-phase DC output: turn off the switch at the AC/DC power unit, turn on the switch at the DC/DC power unit; 3) AC and DC output: Turn on all the switches at the AC/DC power unit and the switches at the DC/DC power unit.

In this embodiment, the main control board of the AC-DC shared electronic load mainly includes a complex programmable logic element CPLD and two digital signal processing elements DSP. Among them, the CPLD is the logic execution unit of the DSP, and the two digital signal processing components are respectively the logic digital signal processing component LOGICDSP and the control signal processing component CONTROLDSP, and the two digital signal processing components are respectively connected to the corresponding port of the CPLD, and the AC The /DC power unit, DC/DC power unit and DC/AC power unit are also connected to the corresponding ports of the CPLD. The main control board of the load realizes the driving control of the current transmission. The specific working principles of LOGICDSP and CONTROLDSP are as follows:

LOGICDSP mainly implements logic timing functions, communication data exchange (RS485, CAN communication) and protection logic, which are as follows:

1) Communication process: the Txd signal sent by LOGICDSP in the communication data exchange process is sent to the CPLDI/O receiving port, and the CPLD is sent to the CAN receiving module through the I/O output port; the CAN module sends the received Rxd signal to the receiving terminal I of the CPLD /O port, CPLD sends to LOGICDSP through the I/O output port to complete a communication process.

2) Protection process: During the protection process, the CPLD inputs the fault signal I_OVER_CPLD AC hardware fault signal through the I/O terminal, BUS_OV_CPLD DC hardware overvoltage fault signal, POWER_FAULT_CPLD auxiliary power fault signal, FAN_FAULT_CPLD cooling fan fault signal, FUSE_FAULT_CPLD power module OC The fault signal, SINF_FAULT_CPLD radiator overheating fault signal, is sent to LOGICDSP through I/O ports LogicGpio7, LogicGpio16, LogicGpio17, LogicGpio18, LogicGpio26, LogicGpio27, and LOGICDSP receives the fault status signal uploaded by CPLD to analyze and process the device to alarm or shut down, so as to realize the equipment protection.

CONTROLDSP mainly executes and completes the control algorithm function and exchanges information. The CONTROLDSP control signal passes through the CPLDI/O port ControllerGpio7, ControllerGpio16, ControllerGpio17, ControllerGpio18, ControllerGpio20, ControllerGpio21, ControllerGpio22, ControllerGpio23 to control the CLOCK_CPLD hardware reset of the underlying device, MAIN_CONTROL_CPLD AC main contactor, CPFT_CONTROL_ AC pre-charge control, IO_O1_CPLD mainstream main contactor, Contactor_CPLD DC pre-charge, FAN_CONTROL_CPLD cooling fan, I_A_CPLD synchronization signal output, I_C_CPLD switch signal output control and AD sampling data discretization, control algorithm and PWM pulse width modulation wave generation, etc. .

The following is a specific description of how each power module performs power transmission under the drive of the control board:

As shown in Figure 6, in the current loop control loop based on the PI control strategy for the AC/DC, the current value obtained from the AC input terminal is compared with the current value of the error signal, and the obtained deviation value is passed through the PI regulator After converting to a voltage reference signal and superimposing the DC bus voltage, the output signal value is processed according to the loaded pulse signal to obtain the output switch signal value. As shown in Figure 7, the DC input DC/DC control mode is the same as the AC/DC control mode. As shown in Figure 8, in the DC/AC control mode, according to the above-mentioned AC/DC control and DC/DC control methods, the voltage outer loop current inner loop control strategy based on PI control is adopted, and the bus voltage loop and bus current After the ring output signal is superimposed with the DC bus voltage, the root-loaded pulse signal is processed, and finally the required switching signal value is obtained.

Under the idea given by the present invention, the technical means in the above-mentioned embodiments are transformed, replaced, and modified in ways that are easy for those skilled in the art, and the functions played are basically the same as those of the corresponding technical means in the present invention. 1. The purpose of the invention realized is also basically the same, and the technical solution formed in this way is formed by fine-tuning the above-mentioned embodiments, and this technical solution still falls within the protection scope of the present invention.

Claims (5)

1. An AC-DC shared electronic load, characterized in that, the AC-DC shared electronic load includes an AC/DC power unit, a DC/DC power unit, a DC/AC power unit, an AC input terminal and a DC input terminal; wherein , the input end of the AC/DC power unit is connected to the AC input end; the input end of the DC/DC power unit is connected to the DC input end; the output end of the AC/DC power unit and the DC/DC power unit are connected to the DC bus, and the DC bus The DC/AC power unit is connected to the power grid; wherein, switches are respectively connected between the AC/DC power unit and the AC input terminal, and between the DC/DC power unit and the DC input terminal. 2. A kind of AC-DC shared electronic load according to claim 1, characterized in that, the circuit structure in the described AC/DC power unit is a three-level single-phase full-bridge circuit; the described DC/DC power The circuit structure in the unit is a Buck-Boost circuit; the circuit structure in the AC/DC power unit is a three-level full-bridge inverter circuit. 3. An AC-DC shared electronic load according to claim 1, characterized in that the AC/DC power unit and its AC input end are also connected with an AC fuse, an LCL filter circuit and a pre-charger connected in parallel at both ends of the switch. branch circuit; the DC/DC power unit and its DC input terminal are also connected with a DC fuse and a pre-charging branch circuit connected in parallel at both ends of the switch. 4. An AC-DC shared electronic load according to claim 1, characterized in that an LCL filter circuit, a circuit breaker and a fuse are also connected between the output end of the DC/AC power unit and the power grid. 5. A kind of AC-DC shared electronic load according to claim 1, characterized in that, the main control board adopted by the AC-DC shared electronic load is composed of digital signal processor DSP complex programmable logic element CPLD and 2 pieces of digital Signal processor DSP; among them, 2 pieces of digital signal processor DSP are: logic digital signal processing element LOGICDSP and control signal processing CONTROLDSP, and respectively connected to the corresponding ports of complex programmable logic element CPLD; AC/DC power unit, DC The /DC power unit and the DC/AC power unit are also connected to corresponding ports of the complex programmable logic element CPLD.