CN108776244B - Electronic load - Google Patents

Abstract

An electronic load, comprising: the load unit is used as a load of the power supply equipment to be tested; the voltage sampling unit is used for collecting the output voltage of the power supply equipment to be tested as a sampling voltage; the current sampling unit is used for collecting the output current of the power supply equipment to be tested as a first sampling current and collecting the current on the energy storage element of the load unit as a second sampling current; the load adjusting unit is used for receiving the voltage reference value and the current reference value and generating a modulation signal according to the current reference value, the voltage reference value, the sampling voltage, the first sampling current and the second sampling current; the modulation signal is used for adjusting the load unit to realize the output control of the power supply equipment to be tested; and the control unit is used for receiving the mode switching instruction and adjusting the current reference value and the voltage reference value according to the mode switching instruction. The electronic load can automatically adjust to realize the output control of the power supply equipment to be tested, thereby meeting the test requirement of the power supply equipment to be tested and having better convenience.

Description

Electronic load

technical field

The invention relates to the technical field of testing, in particular to an electronic load.

Background technique

With the rapid popularization of electric vehicles, charging piles have become more and more popular. In order to ensure the normal functions of the charging pile, the charging pile needs to be strictly tested before leaving the factory, such as constant voltage and constant current tests. Traditional electronic loads are resistive loads, which require testers to continuously adjust the load to meet the test requirements of power supply equipment such as charging piles, which is very inconvenient for testing.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide an electronic load for the problem that the traditional electronic load requires testers to continuously adjust the load to meet the test requirements of the charging equipment, which is very inconvenient for testing.

An electronic load comprising:

a load unit, which is used for connecting with the power supply device to be tested as a load of the power supply device to be tested;

a voltage sampling unit for collecting the output voltage of the power supply device to be tested as a sampling voltage;

a current sampling unit, configured to collect the output current of the power supply device to be tested as the first sampling current, and collect the current on the energy storage element of the load unit as the second sampling current;

a load adjustment unit, connected to the load unit, the voltage sampling unit and the current sampling unit respectively, the load adjustment unit is used for receiving the voltage reference value and the current reference value, and according to the current reference value, the voltage reference value value, the sampled voltage, the first sampled current and the second sampled current to generate a modulation signal; the modulation signal is used to adjust the load unit to realize output control of the power supply device to be tested; as well as

The control unit is connected to the load adjustment unit; the control unit is configured to receive a mode switching instruction, and adjust the current reference value and the voltage reference value according to the mode switching instruction.

The above-mentioned electronic load can adjust the current reference value and the voltage reference value through the control unit according to the mode switching instruction, so that the load adjustment unit can adjust the current reference value, the voltage reference value after adjustment and the sampled voltage obtained by sampling, the first sample The current and the second sampling current are used to generate a modulation signal to adjust the load unit so as to realize the output control of the power supply device to be tested, so as to meet the test requirements of the power supply device to be tested, and has good convenience.

In one embodiment, the load unit includes a filter circuit, an analog load circuit, and an energy feedback circuit; the analog load circuit is connected to the power supply device to be tested through the filter circuit; the analog load circuit is also connected to the The energy feedback circuit is connected to the energy feedback circuit, and the energy feedback circuit is also used for connecting with the commercial power; the current sampling unit is used for collecting the current of the output end of the analog load circuit as the second sampling current.

In one of the embodiments, the load adjustment unit includes a current outer loop circuit, a voltage loop circuit, a selection circuit, a current inner loop circuit and a pulse width modulation circuit; the current outer loop circuit is used for according to the current reference value and The error signal between the first sampled currents generates a current control amount and outputs it to the selection circuit; the voltage loop circuit is configured to generate a voltage control amount according to the error signal between the voltage reference value and the sampled voltage and output it to the selection circuit circuit; the selection circuit is used to select the minimum control quantity among the control quantities in the input and use it as the current given value of the current inner loop circuit; the current inner loop circuit is used to according to the current given value and An error signal between the second sampling currents generates a control signal; the pulse width modulation circuit is configured to generate the modulation signal according to the control signal.

In one of the embodiments, the current outer loop circuit, the voltage loop circuit and the current inner loop circuit all have the same circuit structure; wherein the voltage loop circuit includes a subtractor and a proportional integral adjustment connected in sequence The subtractor is used to receive the voltage reference value and the sampled voltage and obtain the error signal of the two; the proportional-integral regulator is used to adjust the error signal generated by the subtractor to obtain the voltage control quantity .

In one embodiment, the mode switching instruction includes a constant current mode switching instruction and a constant voltage mode switching instruction; the control unit is configured to obtain the corresponding The target constant value of the target constant parameter, and after adjusting the reference value of the target constant parameter to the target constant value, adjust the reference values of other parameters to the rated value; the target constant parameter is voltage or current.

In one of the embodiments, a power sampling unit is further included for collecting the power of the load unit as sampling power; the load adjustment unit further includes a power loop circuit; the power loop circuit is respectively connected with the power sampling unit, the control unit and the selection circuit are connected; the power loop circuit is configured to receive the power reference value output by the control unit and generate a power control quantity output according to the error signal between the power reference value and the sampling power to the selection circuit.

In one of the embodiments, the mode switching instruction includes a constant current mode switching instruction, a constant voltage mode switching instruction, and a constant power mode switching instruction; the control unit is configured to switch according to the constant current mode switching instruction, the constant voltage The mode switching command or the constant power mode switching command obtains the target constant value of the corresponding target constant parameter, and adjusts the reference value of the target constant parameter to the target constant value after adjusting the reference value of other parameters to the rated value; The target constant parameter is voltage, current or power.

In one embodiment, the mode switching instruction further includes a burn-in test mode instruction; the control unit is further configured to change the current reference value, the voltage reference value and the power reference value according to the burn-in test mode instruction value is set to the rated value to control the electronic load to enter maximum power tracking mode; or

The control unit is further configured to monitor the sampled voltage and control the electronic load to enter a maximum power tracking mode when the instantaneous voltage drop of the sampled voltage is monitored to be greater than a preset value.

In one of the embodiments, the control unit is further configured to perform the following steps every preset period after the electronic load enters the maximum power tracking mode:

Obtain the sampling power at the current moment as the second power;

Obtain the sampling power of the previous cycle as the first power;

When the second power is greater than the first power and the current perturbation direction is positive, add the maximum power current setting value to the current perturbation step size and set the current perturbation direction to be positive;

When the second power is greater than the first power and the current disturbance direction is negative, subtracting the current disturbance step size from the maximum power current setting value and setting the current disturbance reverse to negative;

when the second power is less than or equal to the first power and the current perturbation direction is positive, subtracting the current perturbation step size from the maximum power current setting value and setting the current perturbation direction to be negative;

When the second power is less than or equal to the first power and the current perturbation direction is negative, add the maximum power current setting value to the current perturbation step size and set the current perturbation direction to positive ; The maximum power current setting value is used as the current reference value.

In one of the embodiments, the control unit adjusts the current reference value and the voltage reference value at a preset adjustment rate.

Description of drawings

1 is a schematic block diagram of an electronic load in an embodiment;

2 is a structural block diagram of a load unit in an embodiment;

3 is a circuit schematic diagram of an analog load circuit in an embodiment;

4 is a structural block diagram of a load adjustment unit in an embodiment;

FIG. 5 is a schematic circuit diagram of a load adjustment unit in an embodiment;

6 is a flowchart of a maximum power tracking method in an embodiment;

FIG. 7 is an external characteristic curve diagram of a charging pile in an embodiment.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

An embodiment of the present invention provides an electronic load for connecting with a power supply device to be tested as a load of the power supply device to be tested. The power supply equipment to be tested may include charging piles, switching power supplies, linear power supplies, UPS power supplies, batteries and chargers, etc. that require constant current function tests and constant voltage function tests. In this embodiment, a charging pile is used as an example for description.

FIG. 1 is a schematic block diagram of an electronic load in an embodiment. Referring to FIG. 1 , the electronic load includes a load unit 110 , a voltage sampling unit 120 , a current sampling unit 130 , a load adjustment unit 140 and a control unit 150 .

The load unit 110 is used for connecting with the power supply device 90 to be tested, and serves as a load of the power supply device 90 to be tested. The voltage sampling unit 120 is configured to collect the output voltage of the power supply device 90 to be tested as the sampling voltage Vs. The current sampling unit 130 is used to collect the output current flowing through the power supply device 90 under test as the first sampling current Is, and simultaneously collect the current on the energy storage element in the load unit 110 as the second sampling current I1. The load adjustment unit 140 is respectively connected with the load unit 110 , the voltage sampling unit 120 and the current sampling unit 130 . The load regulating unit 140 is also connected to the control unit 150 . The control unit 150 is configured to receive the mode switching instruction, adjust the current reference value Iset and the voltage reference value Vset according to the mode switching instruction, and output them to the load adjustment unit 140 . The load adjustment unit 140 receives the current reference value Iset, the first sampling current I1, the second sampling current Is, the voltage reference value Vset and the sampling voltage Vs, and generates a modulation signal according to them. The modulation signal is used to adjust the load unit 110 to realize the output control of the power supply device 90 under test. For example, under the constant current mode switching command, the modulation signal is used to control the current on the side of the load unit 110 to be constant, so as to achieve constant control of the output current of the power supply device 90 under test.

The above-mentioned electronic load can adjust the current reference value Iset and the voltage reference value Vset through the control unit 150 according to the mode switching instruction, so that the load adjustment unit 140 can adjust the current reference value Iset, the voltage reference value Vset and the sampled value according to the adjusted current reference value Iset. Sampling the voltage Vs, the first sampling current Is and the second sampling current I1 to generate a modulation signal to adjust the load unit 110 to realize the output control of the power supply device 90 to be tested, so as to meet the test requirements of the power supply device to be tested 90, and has a relatively high performance. Good convenience.

In an embodiment, a structural block diagram of the load unit 110 is shown in FIG. 2 . The load unit 110 includes a filter circuit 112 , an analog load circuit 114 and an energy feedback circuit 116 . Wherein, both ends of the analog load circuit 114 are connected to the power supply device 90 under test through the filter circuit 112 . The analog load circuit 114 is also connected to the energy feedback circuit 116 . The output end of the energy feedback circuit 116 is also connected to the commercial power. The energy feedback circuit 116 is used to convert the generated energy of the electronic load into electric energy and feed it back to the grid. Therefore, the electronic load in this embodiment can also be called a feedback electronic load. Compared with traditional resistive loads, the regenerative electronic load greatly saves energy and avoids the waste of energy by feeding back electric energy to the grid for reuse. At this time, the current sampling unit 130 collects the current on the energy storage element of the analog load circuit 114 as the second sampling current I1. In other embodiments, the filter circuit 112 and the analog load circuit 114 can also be used as a whole.

In a specific embodiment, the analog load circuit 114 adopts an inductive DC-DC boost circuit, and the filter circuit 112 adopts a filter capacitor C2, as shown in FIG. 3 . At this time, the energy storage element is the energy storage inductor L. The energy feedback circuit 116 adopts a DC-AC circuit. Therefore, the second sampling current is also the current I1 flowing through the inductor L. In one embodiment, both DC-DC and DC-AC are bidirectional, which can meet the testing requirements of the charging pile with a wide voltage range of 200V to 750V. After the pre-stage DC-DC circuit is started, the voltage output by the power supply device 90 to be tested will be raised as the input of DC-AC. DC-AC is used to connect to the grid and feed back energy to the grid to achieve the purpose of feeding back to the grid. The DC-DC circuit can dynamically adjust the output voltage of the DC-DC circuit according to the output of the charging pile, that is, the input voltage of the DC-AC. Specifically, the DC-DC circuit can adopt a linear adjustment method, and the lowest and highest voltage output by the charging pile corresponds to the voltage value that meets the DC-AC requirements. For example, the test voltage of the charging pile is 200V to 750V, and the output voltage of the corresponding DC-DC circuit is set to 550V to 800V, and the relationship of the voltage increase is set as follows:

Vout=0.4545Vc+459.

Among them, Vout is the output voltage of the DC-DC circuit, and Vc is the output voltage of the charging pile (that is, the sampling voltage). In this case, when the output voltage of the charging pile is 200V, the output voltage of the DC-DC circuit is 550V; When the output voltage of the DC-DC circuit is 750V, the output voltage of the DC-DC circuit is 800V.

In one embodiment, the load adjustment unit 140 includes a voltage loop circuit 210 , a current outer loop circuit 220 , a selection circuit 230 , a current inner loop circuit 240 and a pulse width modulation circuit (PWM modulation circuit) 250 , as shown in FIG. 4 . The voltage loop circuit 210 is configured to generate a voltage control quantity for the selection circuit 230 according to the error signal between the voltage reference value Vset and the sampling voltage Vs. The current outer loop circuit 220 is configured to generate a current control quantity and output it to the selection circuit 230 according to the error signal between the current reference value Iset and the first sampling current Is. The selection circuit 230 is used to select the minimum control quantity among the control quantities output by the voltage loop circuit 210 and the current outer loop circuit 220 as the current given value Ilref of the current inner loop circuit 240 . The current inner loop circuit 240 is used to generate a control signal according to the error signal between the current given value Ilref and the second sampling current Il. The PWM modulation circuit 250 is used to generate a modulation signal according to the control signal to control the power tube in the DC-DC circuit, realize the control of the current and voltage in the DC-DC circuit, and finally realize the constant voltage of the power supply device 90 to be tested. voltage or constant current control.

In this embodiment, the voltage loop circuit 210 , the current outer loop circuit 220 and the current inner loop circuit 240 all have the same circuit structure, as shown in FIG. 5 . The following description takes the voltage outer loop circuit 210 as an example. The voltage outer loop circuit 210 includes a subtractor 212 and a proportional integral regulator (PI regulator) 214 connected in sequence. One input end of the subtractor 212 is connected to the voltage sampling unit 120 , and the other input end is connected to the control unit 150 . The subtractor 212 receives the sampling voltage Vs output by the voltage sampling unit 120 and the voltage reference value Vset output by the control unit 150 . The subtractor 212 is used for subtracting the sampling voltage Vs from the voltage reference value Vset to obtain an error signal therebetween, and then inputting the error signal to the PI regulator 214 . The PI regulator 214 is used for linearly adjusting the error signal generated by the subtractor 212 to obtain the voltage control quantity. The current outer loop circuit 220 also forms a current control amount according to the current reference value Iset and the first sampling current Is.

In this embodiment, the mode switching command includes a constant current mode switching command and a constant voltage mode switching command. The mode switching instruction can be input by the user through a mouse, a keyboard, a touch keyboard, voice recognition and other devices. The constant current mode switching instruction refers to controlling the power supply device 90 under test to be in the constant current mode, so the target constant parameter is current. The constant voltage mode switching command refers to controlling the power supply device 90 to be tested to be in the constant voltage mode, so the target constant parameter is voltage. After receiving the constant current mode switching instruction, the control unit 150 adjusts the target constant parameter, that is, the current, to the target constant value, and then adjusts other parameters (voltage at this time) to the maximum rated value. Therefore, after the voltage is adjusted to the rated value, the voltage loop circuit 210 will gradually become saturated, and only the current outer loop circuit 220 will work at this time, thereby achieving the purpose of constant output current of the power supply device 90 under test. After receiving the constant voltage mode switching instruction, the control unit 150 adjusts the target constant parameter, that is, the voltage, to the target constant value, and then adjusts other parameters (current at this time) to the rated value. Therefore, after the current is adjusted to the rated value, the current outer loop circuit 220 will gradually become saturated, and only the voltage loop circuit 210 will work at this time, thereby achieving the purpose of constant the output voltage of the power supply device 90 under test.

In one embodiment, a power sampling unit is also included. The power sampling unit is used to collect the output power of the power supply device 90 to be tested. In one embodiment, the power sampling unit is connected to the current sampling unit 130 and the voltage sampling unit 120 respectively, so that the first sampling current Is collected by the current sampling unit 130 and the sampling voltage Vs collected by the voltage sampling unit 120 are directly used to calculate and obtain Sampling power Ps. At this time, the load adjustment unit 140 further includes a power loop circuit 260, as shown in FIG. 4 . The power loop circuit 260 is respectively connected with the power sampling unit, the control unit 150 and the selection circuit 230 . The power loop circuit 260 is configured to receive the error signal between the power reference value Pset outputted by the control unit 150 and the sampling power Ps, generate a power control amount, and output it to the selection circuit 230 for selection. The power loop circuit 260 has the same circuit structure as the voltage loop circuit 210 and the current outer loop circuit 220 , as shown in FIG. 5 , and details are not described here.

In this embodiment, the mode switching instruction further includes a constant power mode switching instruction. The constant power mode switching command is used to control the output power of the power supply device to be tested to be constant. When the control unit 150 receives the constant power mode switching instruction, it controls the power reference value to the target constant value and then adjusts other parameters (including current and voltage at this time) to the rated value. Therefore, both the voltage loop circuit 210 and the current outer loop circuit 220 will gradually become saturated, and only the power loop circuit 260 will work at this time, thereby achieving the purpose of maintaining the output power of the power supply device 90 under test. When receiving the constant current or constant voltage mode switching instruction, the control unit 150 adjusts the current reference value or the voltage reference value to the target value, and then adjusts other parameters to the rated value. By first adjusting the target constant parameter to the target value, and then adjusting other parameters to the rated value, the situation that the load power exceeds the maximum power of the power supply device 90 to be tested can be avoided during the parameter adjustment process.

In one embodiment, the mode switch instruction further includes a burn-in test mode instruction. The burn-in test mode command means that the power supply device to be tested is in the burn-in test mode, that is, the electronic load is used as the load during the burn-in test process of the power supply device to be tested. After receiving the burn-in test mode instruction, the control unit 150 may set the current reference value Iset, the voltage reference value Vset and the power reference value Pset as rated values to control the electronic load to enter the maximum power tracking mode. Or the control unit 150 can control the electronic load to enter the maximum power tracking mode when the instantaneous voltage drop Vdroop of the monitored sampled voltage is greater than the preset value, so as to track the maximum power point to seek the maximum power value, thereby ensuring that the power supply device 90 to be tested is in the maximum power tracking mode. The maximum power point is aging. Specifically, when the power supply device to be tested is a charging pile, its external characteristic curve is shown in Figure 7. In Figure 7, a charging pile mode with a rated voltage of 750V, a rated current of 20A, and a rated power of 15KW is taken as an example, and the maximum current is 22A. When turned on, the charging pile can maintain the voltage at 750V, and as the load increases, the output current and power increase. When the load power exceeds the power of the charging pile, two situations will occur. One is to pull down the output voltage of the charging pile and maintain it at another lower voltage point, and the power will drop. Then, the output of the charging pile is directly pulled across, and the alarm is turned off. Therefore, according to the output characteristics, it is a constant voltage process in the low power stage. If the voltage suddenly drops by a certain value Vdroop, it is considered that the load power is too large and exceeds the maximum power of the charging pile. At this time, the maximum power is entered. in the tracking mode, and form the power tracking mode flag. In this embodiment, the preset value Vdroop is set as Vdroop=(12+Vdc×0.025)V, Vdc is the rated voltage of the charging pile, when Vdroop drops, the power tracking mode is forcibly entered.

In one embodiment, the current perturbation method is used for maximum power point tracking. The control unit 150 executes the steps shown in FIG. 6 every preset period after the electronic load enters the maximum power tracking mode. In this embodiment, the preset period is 20 ms, and in other embodiments, the preset period can also be set as required. Figure 6 includes the following steps:

Step S310, acquiring the sampling power at the current moment as the second power.

The second power P1 can be obtained by a power sampling unit. The electronic load may also be provided with a storage device to store the sampling power collected each time.

Step S320, acquiring the sampling power of the previous cycle as the first power.

The sampled power of the previous cycle can be read directly from the storage device. When the sampling power of the previous cycle cannot be read, the first power is set to 0, that is, the default value of the first power P0 is 0.

Step S330, determining whether the second power is greater than the first power.

When the second power P1 is greater than the first power P0, it means that the power increases with time, and step S340 is performed, otherwise, step S370 is performed.

In step S340, it is determined whether the current disturbance direction is positive.

In one embodiment, the value of the current disturbance direction Idir is 0 or 1. When the current perturbation direction is positive, Idir is 0, and when the current perturbation direction is negative, Idir is 1. Judging whether the current disturbance direction is positive or negative is actually a process of judging whether Idir is equal to 0. When Idir is equal to 0, it means that the current disturbance direction is positive, then step S350 is performed, otherwise, step S360 is performed.

In step S350, the maximum power current setting value is increased by the current disturbance step size, and the current disturbance direction is set to be positive.

Since the second power P1 is greater than the first power P0 and the current disturbance direction is positive, the maximum power current setting value Imppset continues to be increased at this time to determine the maximum power point, and the current disturbance direction is set to be positive. The maximum power current setting value Imppset is used as the current reference value Iset in the burn-in test mode.

Step S360, subtract the current disturbance step size from the maximum power current setting value, and set the current disturbance direction to be negative.

Step S370, determine whether the current disturbance direction is positive.

When Idir is equal to 0, it means that the current disturbance direction is positive, then step S380 is performed, otherwise, step S390 is performed.

In step S380, the current disturbance step size is subtracted from the maximum power current setting value, and the current disturbance direction is set to be negative.

In step S390, the maximum power current setting value is increased by the current disturbance step size, and the current disturbance direction is set to be positive.

Through the above method, the electronic load will record the power value corresponding to the current current after entering the maximum power tracking mode, and record the power value after the disturbance through the disturbance current (in this case, the forward disturbance). When the power increases, the current will continue to increase, and when the power decreases, the current will be decreased, and the maximum power value will be continuously adjusted by the current. When the disturbance current is a negative disturbance, the opposite processing is required, that is, the current is reduced to find the maximum power value, so that the power output of the power supply device to be tested is maximized and the optimal aging condition is achieved. During this adjustment process, neither the current nor the voltage will limit it to a nominal or target constant value.

In one embodiment, the control unit does not suddenly increase or decrease a certain parameter during the process of adjusting the reference value of each parameter, but adjusts at a certain adjustment rate. The adjustment rate of the parameters can be set as required. For example, the voltage update rate can be set to 100V/s, that is, every 0.1V/ms, so every 1ms, the voltage set value Vset changes by 0.1V. The current reference and power reference can be set in the same way. The adjustment rate can be set manually by the user or by default by the system.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present invention, and the descriptions thereof are more specific and detailed, but should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can also be made, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the appended claims.

Claims (10)

1. an electronic load, is characterized in that, comprises: a load unit, which is used for connecting with the power supply device to be tested as a load of the power supply device to be tested; a voltage sampling unit for collecting the output voltage of the power supply device to be tested as a sampling voltage; a current sampling unit, configured to collect the output current of the power supply device to be tested as the first sampling current, and collect the current on the energy storage element of the load unit as the second sampling current; a power sampling unit for collecting the power of the load unit as the sampling power; a load adjustment unit, connected to the load unit, the voltage sampling unit and the current sampling unit respectively, the load adjustment unit is used for receiving the voltage reference value and the current reference value, and according to the current reference value, the voltage reference value value, the sampled voltage, the first sampled current and the second sampled current to generate a modulation signal; the modulation signal is used to adjust the load unit to realize output control of the power supply device to be tested; as well as a control unit, connected with the load adjustment unit; the control unit is configured to receive a mode switching instruction, and adjust the current reference value and the voltage reference value according to the mode switching instruction; the control unit also uses After the electronic load enters the maximum power tracking mode, the following steps are performed every preset period: Obtain the sampling power at the current moment as the second power; Obtain the sampling power of the previous cycle as the first power; When the second power is greater than the first power and the current perturbation direction is positive, add the maximum power current setting value to the current perturbation step size and set the current perturbation direction to be positive; When the second power is greater than the first power and the current disturbance direction is negative, subtracting the current disturbance step size from the maximum power current setting value and setting the current disturbance reverse to negative; when the second power is less than or equal to the first power and the current perturbation direction is positive, subtracting the current perturbation step size from the maximum power current setting value and setting the current perturbation direction to be negative; When the second power is less than or equal to the first power and the current perturbation direction is negative, add the maximum power current setting value to the current perturbation step size and set the current perturbation direction to positive ; The maximum power current setting value is used as the current reference value. 2. The electronic load according to claim 1, wherein the load unit comprises a filter circuit, an analog load circuit and an energy feedback circuit; the analog load circuit is connected to the power supply device to be tested through the filter circuit The analog load circuit is also connected with the energy feedback circuit, and the energy feedback circuit is also used for connecting with the commercial power supply; the current sampling unit is used for collecting the current of the output end of the analog load circuit as the second sampling current . 3. The electronic load according to claim 2, wherein the load adjustment unit comprises a current outer loop circuit, a voltage loop circuit, a selection circuit, a current inner loop circuit and a pulse width modulation circuit; the current outer loop circuit is used for generating a current control quantity and outputting it to the selection circuit according to the error signal between the current reference value and the first sampled current; the voltage loop circuit is used for generating a current control quantity according to the difference between the voltage reference value and the sampled voltage The error signal generates a voltage control quantity and outputs it to the selection circuit; the selection circuit is used to select the minimum control quantity among the various control quantities in the input and use it as the current given value of the current inner loop circuit; the current inner loop circuit uses generating a control signal according to the error signal between the given current value and the second sampling current; the pulse width modulation circuit is used for generating the modulation signal according to the control signal. 4 . The electronic load according to claim 3 , wherein the current outer loop circuit, the voltage loop circuit and the current inner loop circuit all have the same circuit structure; wherein the voltage loop circuit comprises: 5 . A subtractor and a proportional-integral regulator are connected in sequence; the subtractor is used for receiving the voltage reference value and the sampled voltage and obtaining the error signal of the two; the proportional-integral regulator is used for the error generated by the subtractor The signal is adjusted to obtain the voltage control amount. 5. The electronic load according to claim 3 or 4, wherein the mode switching command comprises a constant current mode switching command and a constant voltage mode switching command; the control unit is configured to switch the command according to the constant current mode Or the constant voltage mode switching instruction obtains the target constant value of the corresponding target constant parameter, and adjusts the reference value of the target constant parameter to the target constant value and then adjusts the reference values of other parameters to the rated value; the target constant value The parameter is voltage or current. 6. The electronic load according to claim 3 or 4, wherein the load adjustment unit further comprises a power loop circuit; the power loop circuit is respectively connected with the power sampling unit, the control unit and the selection unit. The circuit is connected; the power loop circuit is configured to receive the power reference value output by the control unit, and generate a power control quantity according to the error signal between the power reference value and the sampling power and output it to the selection circuit. 7. The electronic load according to claim 6, wherein the mode switching instruction comprises a constant current mode switching instruction, a constant voltage mode switching instruction and a constant power mode switching instruction; The flow mode switching command, the constant voltage mode switching command or the constant power mode switching command obtains the target constant value of the corresponding target constant parameter, and adjusts the reference value of the target constant parameter to the target constant value and then adjusts other parameters to the target constant value. The reference value of is adjusted to the rated value; the target constant parameter is voltage, current or power. 8 . The electronic load according to claim 7 , wherein the mode switching instruction further comprises a burn-in test mode instruction; the control unit is further configured to change the current reference value, the all The voltage reference value and the power reference value are set as rated values to control the electronic load to enter the maximum power tracking mode. 9 . The electronic load according to claim 7 , wherein the mode switching instruction further comprises a burn-in test mode instruction; the control unit is further configured to monitor the sampling voltage and monitor the sampling voltage when the sampling voltage is detected. 10 . When the instantaneous voltage drop is greater than a preset value, the electronic load is controlled to enter the maximum power tracking mode. 10 . The electronic load according to claim 1 , wherein the control unit adjusts the current reference value and the voltage reference value at a preset adjustment rate. 11 .

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