Four-quadrant energy feedback load test system

Abstract

The utility model belongs to the technical field of frequency converter energy feedback, and specifically relates to a four-quadrant energy feedback load test system comprising a power supply unit which comprises a plurality of paths of power supply branches with selectable power; the load unit comprises a plurality of paths of load branches with selectable power; an energy feedback control unit, wherein the energy feedback control unit comprises an AFE four-quadrant controller; and a test connection mechanism. Wherein the input end of the AFE four-quadrant controller is connected with the power supply unit through a filter circuit, and the output end of the AFE four-quadrant controller is connected with the load unit through a direct current bus; and the test connection mechanism is used for mechanically connecting the frequency converter to be tested with a load motor in the load unit. According to loads with different large power, under the condition that full-load testing is achieved, energy generated in the testing process can be fed back to a power grid at the same time to achieve bidirectional flow of the energy, and therefore the purpose of full-load testing of the large-power frequency converter is achieved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of frequency converter energy feedback, specifically relates to a four quadrant energy feedback load test system. BACKGROUND

[0002] Frequency converter plays an important role in industrial applications, and the reliability of its factory test directly affects the actual application effect. In the prior art, the factory test of the frequency converter manufacturer in the production of high-power (55kw and above) frequency converter mainly has the following technical problems:

[0003] Limitation of test method: the traditional test adopts the excitation motor simulation load mode, needs to be equipped with large capacity transformer, leads to large infrastructure investment; due to high test cost, many manufacturers choose not to carry out full load test or reduced load test, which affects product quality guarantee.

[0004] Low energy utilization efficiency: the existing two quadrant frequency converter adopts diode rectifier bridge structure, can only realize unidirectional flow of electric energy; in the application scene such as elevator, hoist, centrifuge system, oil pumping machine, which needs energy feedback, only can consume feedback energy through increasing resistance braking unit, causes energy waste.

[0005] Grid influence: the harmonic pollution generated by diode rectifier bridge influences the quality of power grid; low power factor is not conducive to the stable operation of power grid.

[0006] High test cost: need to increase transformer capacity, improve infrastructure investment; large energy consumption in test process, high operating cost.

[0007] Control scheme defects: lack of control scheme that can realize bidirectional flow of energy; lack of software and hardware integrated solution for feeding back energy to power grid. SUMMARY

[0008] The utility model aims at the deficiencies of the prior art, provides a four quadrant energy feedback load test system, for different high-power loads, can realize full load test, and can feed back the energy generated in the test process to the power grid to realize bidirectional flow of energy, so as to achieve the purpose of full load test of high-power frequency converter.

[0009] Technical scheme: the four quadrant energy feedback load test system, including:

[0010] The power supply unit includes a plurality of power supply branches with selectable power;

[0011] The load unit includes a plurality of load branches with selectable power;

[0012] An energy feedback control unit, the energy feedback control unit comprising an AFE four-quadrant controller; and

[0013] A test connection mechanism;

[0014] The input end of the AFE four-quadrant controller is connected with the power supply unit through a filter circuit, and the output end is connected with a load unit through a DC bus; the test connection mechanism is used for mechanically connecting a load motor in the load unit with a to-be-tested frequency converter.

[0015] Further to the above technical solution, the power supply unit comprises:

[0016] A first power supply branch with a rated power of 45 kW;

[0017] A second power supply branch with a rated power of 110 kW; and

[0018] Two third power supply branches each with a rated power of 250 kW;

[0019] The power supply branches are selectively connected with the system through corresponding contactors.

[0020] Further, the load unit comprises:

[0021] A first load branch with a rated power of 45 kW;

[0022] A second load branch with a rated power of 110 kW;

[0023] A third load branch with a rated power of 160 kW;

[0024] A fourth load branch with a rated power of 200 kW; and

[0025] A fifth load branch with a rated power of 515 kW;

[0026] The load branches are selectively connected with the system through corresponding contactors.

[0027] Further, the filter circuit comprises:

[0028] A filter capacitor for storing energy and smoothing pulsation in DC power;

[0029] A filter inductor for current filtering;

[0030] A PFC inductor for power factor correction; and

[0031] A buffer circuit comprising a buffer contactor and a buffer resistor connected in series.

[0032] Further, the AFE four-quadrant controller comprises:

[0033] a rectification control unit for generating a PWM pulse control signal;

[0034] an IGBT module comprising six IGBT tubes for realizing AC / DC bidirectional conversion; and

[0035] a DC bus for connecting the IGBT module and the load unit.

[0036] Further, a control system is further included, and the control system comprises:

[0037] a PLC controller;

[0038] industrial control software; and

[0039] a multi-path contactor control circuit;

[0040] The PLC controller controls the on-off state of the corresponding contactor through the industrial control software according to the power of the to-be-tested frequency converter, so as to realize the selective access of the power branch and the load branch.

[0041] Further, the load motor in the load unit adopts a torque control mode, and the motor controlled by the to-be-tested frequency converter adopts a speed control mode.

[0042] Further, the AFE four-quadrant controller has two working modes of motoring state and generating state:

[0043] In the motoring state, energy flows from the power grid to the motor via the rectification loop and the inverter loop;

[0044] In the generating state, energy is fed back from the motor to the power grid via the inverter loop and the rectification loop.

[0045] Further, in the generating state,

[0046] When the DC bus voltage exceeds a preset threshold value, the rectification control unit starts energy feedback control;

[0047] By controlling the phase and amplitude of the inverter voltage, the electric energy generated by the motor is fed back to the power grid.

[0048] Benefits: Compared with the prior art, the utility model has the advantages that: through AFE four-quadrant controller, bidirectional flow of electric energy is realized, the electric energy generated in the test process can be fed back to the power grid, high efficient recycling of energy is realized, compared with the traditional scheme, energy utilization efficiency is improved by more than 50%, through the combination design of multiple power supplies and loads, a set of system can test frequency converters of multiple power specifications, improves equipment utilization, does not need to configure large capacity transformer, reduces infrastructure investment by about 40%, reduces test cost, realizes real full load test of high power frequency converter, through the accurate control of PLC and industrial control software, test data is more reliable, improves product quality guarantee capability, adopts IGBT module to replace diode rectifier bridge, significantly reduces harmonic pollution, through PFC inductance, power factor correction is carried out, improves power factor to more than 0.95, improves power grid quality, provides complete system solution, the design of filter circuit guarantees electric energy quality, buffer circuit provides overvoltage protection, improves system reliability, energy recovery efficiency reaches more than 85%, compared with the traditional scheme, carbon emission is reduced by about 60%, energy saving and environmental protection effect is remarkable, according to test demand, automatically selects optimal power supply and load combination, operation convenience is improved, supports the test of frequency converter of different power levels of 45kW to 515kW, can flexibly expand system capacity according to actual demand, system adaptability is strong. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is the circuit schematic diagram of total input power supply of the utility model;

[0050] Figure 2 It is the circuit schematic diagram of input power supply of the utility model test frequency converter;

[0051] Figure 3 It is the circuit connection schematic diagram of 5-way load;

[0052] Figure 4 It is the circuit schematic diagram of the core control unit of four-quadrant energy feedback load test system;

[0053] Figure 5 It is the necessary connection loop of four-quadrant AFE. DETAILED DESCRIPTION

[0054] The technical scheme of the utility model will be described in detail below with the drawings, but the protection scope of the utility model is not limited to the described embodiments.

[0055] Embodiment 1: Figure 1 It is 690V 110KW power supply cabinet.

[0056] As Figure 245kw, 110kw and 2 route 250kw power supply is mainly responsible for providing input power for the test frequency converter, according to the power of the test frequency converter, the corresponding KM1 / KM2 / KM3 / KM4 on-off can be selected.

[0057] As shown in Figure 3 5 route load power is set respectively, 45Kw, 110kw, 160kw, 200kw and 515kw, through the on-off between KM5-KM12, different load power can be selected.

[0058] As shown in Figure 4 the core control unit, the front end AFE is a four quadrant control unit, that is, the rear end can provide power and the rear end can provide power feedback to the grid. The frequency converter connected with AFE through DC bus (+, -) corresponds to four load motors. The load motor and the test motor are connected in the same way as the motor shaft. At the same time, the load motor adopts torque control mode, and the test motor adopts speed control mode. When loading is needed, only the load motor controlled by the frequency converter needs to increase torque to realize loading. At this time, the load motor will enter the power generation mode, and the generated power will be sent to the grid through the DC bus, realizing energy saving. When the load motor is not loaded, it is in the mode of electric drive. AFE provides power for the load motor through the DC bus, and consumes power.

[0059] As shown in Figure 5The necessary connection circuit of the four-quadrant AFE is shown. The three-phase power supply L1 / L2 / L3 is connected to the UVW end of the frequency converter through the total switch, and is connected with the filter capacitor, filter inductor, PFC inductor, buffer contactor and buffer resistor. At the same time, the phase sequence of the three-phase input power supply is sampled between the switch and the filter inductor and connected to the main control board. The main function of the filter capacitor in the four-quadrant frequency converter is energy storage and filtering. During the rectification process, alternating current is converted into direct current, but at this time the direct current may contain a certain pulsating component. The filter capacitor can smooth these pulsations and make the direct current more stable. In addition, the filter capacitor can also provide necessary energy buffer during the operation of the frequency converter to ensure the smoothness of the motor operation. The main function of the filter inductor in the four-quadrant frequency converter is current filtering. It is usually used together with the filter capacitor to further smooth the pulsating component in the direct current. When the current passes through the filter inductor, the inductor will generate a self-induced electromotive force, which will hinder the change of the current, so as to make the current waveform smoother. In addition, the filter inductor can also filter out the high-frequency component of the current waveform in the feedback state, protecting the frequency converter and the power grid from harmonic pollution. The PFC inductor mainly participates in the power factor correction (PFC) circuit in the four-quadrant frequency converter. Power factor correction is a technology that adjusts the circuit structure to improve the power factor and reduce the reactive power. The PFC inductor cooperates with other elements to reduce the phase difference between the fundamental current and voltage of the alternating current input, thereby improving the power factor. This not only reduces the reactive power consumption in the inductor capacitor device, but also reduces the harmonic pollution to the power grid and improves the energy efficiency of the entire system. The buffer contactor and the buffer resistor constitute the input buffer circuit. The bus capacitor inside the frequency converter is not a complete capacitor, and it may contain energy accumulated in the capacitor plate. If this part of energy is not consumed through the buffer circuit, it may cause damage to the frequency converter. The function of the buffer contactor is to consume this part of energy to ensure that the bus voltage is not too high, thereby protecting the frequency converter from damage.

[0060] In addition, a part of the software control part needs to be added, and PLC+industrial control software is adopted to select different contactor on-off states through different test powers.

[0061] It should be noted that the load motor mainly works in two different working states, as follows:

[0062] Motor state: when the motor works in the motor state, the main function of the four-quadrant frequency converter is to convert the alternating current of the power grid into direct current suitable for the operation of the motor, and further convert it into adjustable voltage and frequency alternating current to drive the motor.

[0063] Rectification process: The DSP (Digital Signal Processor) of the rectification control unit generates 6 high-frequency PWM (Pulse Width Modulation) pulses, which control the turn-on and turn-off of the 6 IGBTs (Insulated Gate Bipolar Transistors) on the rectification side. The turn-on and turn-off of the IGBTs, together with the input reactor, produce a sinusoidal current waveform consistent with the phase of the input voltage, thereby eliminating the harmonic pollution that a diode bridge might produce.

[0064] Inversion process: The DC power after rectification is sent to the inversion unit, which converts it into AC power with adjustable voltage and frequency through the inversion action of IGBTs, driving the motor to operate.

[0065] Energy flow: In motoring state, energy flows from the power grid to the motor through the rectification and inversion circuits. At this time, the four-quadrant inverter works in the first and third quadrants.

[0066] Generating state: When the motor operates in generating state, such as during the descent of some potential loads (e.g., cranes, locomotive traction, etc.), the motor generates electricity due to gravity, and the generated power needs to be effectively recovered and processed.

[0067] Energy feedback: The power generated by the motor is fed back to the DC bus through the diodes on the inversion side. When the DC bus voltage exceeds a certain threshold, the energy feedback control part on the rectification side starts to invert the DC power into AC power.

[0068] Feedback control: By controlling the phase and amplitude of the inversion voltage, the power generated by the motor is fed back to the power grid, achieving energy recovery and reuse. This process not only improves energy utilization efficiency, but also reduces energy consumption on the braking resistor.

[0069] Energy flow: In generating state, energy flows from the motor to the power grid through the inversion and rectification sides. At this time, the four-quadrant inverter works in the second and fourth quadrants.

[0070] As mentioned above, although the present application has been shown and described with reference to specific preferred embodiments, it should not be construed as a limitation on the present application itself. Various changes can be made in form and details without departing from the spirit and scope of the present application as defined in the appended claims.

Claims

1. A four-quadrant energy feedback load test system, characterized by, The application relates to a variable frequency motor test system. The system comprises: a power supply unit comprising multiple power supply branches of alternative power; a load unit comprising multiple load branches of alternative power; an energy feedback control unit comprising an AFE four-quadrant controller; a test connection mechanism; wherein the input end of the AFE four-quadrant controller is connected with the power supply unit through a filter circuit, and the output end is connected with the load unit through a DC bus; and the test connection mechanism is used for mechanically connecting a variable frequency motor to be tested with a load motor in the load unit.

2. The four-quadrant energy regenerative load test system of claim 1, wherein, The power supply unit comprises: a first power supply branch with a rated power of 45kW; a second power supply branch with a rated power of 110kW; and two third power supply branches each with a rated power of 250kW; the power supply branches are selectively connected with the system through corresponding contactors.

3. The four-quadrant energy regenerative load test system of claim 1, wherein, The load unit comprises: a first load branch with a rated power of 45kW; a second load branch with a rated power of 110kW; a third load branch with a rated power of 160kW; a fourth load branch with a rated power of 200kW; and a fifth load branch with a rated power of 515kW; the load branches are selectively connected with the system through corresponding contactors.

4. The four-quadrant energy regenerative load test system of claim 1, wherein, The filter circuit comprises: a filter capacitor for storing energy and smoothing the pulsation in the DC current; a filter inductor for current filtering; a PFC inductor for power factor correction; and a buffer circuit comprising a buffer contactor and a buffer resistor connected in series.

5. The four-quadrant energy regenerative load test system of claim 1, wherein, The AFE four-quadrant controller comprises: a rectification control unit for generating a PWM pulse control signal; an IGBT module comprising six IGBT tubes for realizing AC / DC bidirectional conversion; and a DC bus for connecting the IGBT module with the load unit.

6. The four-quadrant energy regenerative load test system of claim 1, wherein, The system further comprises a control system comprising: a PLC controller; industrial control software; and a multiple contactor control circuit; wherein the PLC controller controls the on-off state of the corresponding contactor through the industrial control software according to the power of the variable frequency motor to be tested, so as to realize the selective connection of the power supply branches and the load branches.

7. The four-quadrant energy regenerative load test system of claim 1, wherein, The load motor in the load unit adopts a torque control mode, and the motor controlled by the variable frequency motor to be tested adopts a speed control mode.

8. The four-quadrant energy regenerative load test system of claim 1, wherein, The AFE four-quadrant controller has two working modes of an electric mode and a power generation mode: in the electric mode, energy flows from the power grid to the motor through a rectification circuit and an inverter circuit; in the power generation mode, energy flows from the motor to the power grid through the inverter circuit and the rectification circuit.

9. The four-quadrant energy regenerative load test system of claim 8, wherein, In the power generation mode, when the DC bus voltage exceeds a preset threshold, the rectification control unit starts the energy feedback control; by controlling the phase and amplitude of the inverter voltage, the electric energy generated by the motor is fed back to the power grid.

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