Stepless adjustable constant power load

Abstract

A stepless adjustable constant power load, comprising a power resistance adjustment device, a heat dissipation system, and a controller. The power resistance adjustment device comprises at least three fixed-value resistors having different resistance values, and a primary-circuit frequency converter; each fixed-value resistor is connected in series with a contactor to serve as a load module, and load modules are connected in parallel; an input end of the primary-circuit frequency converter is connected to a test power supply, the load modules are connected in parallel and then connected to an output end of the primary-circuit frequency converter, and the primary-circuit frequency converter serves as an adjustable-voltage power consumption unit. The controller selects a loading combination from the load modules on the basis of the magnitude of a target power, the loading combination is configured to enable combined power consumption to be less than the target power and a difference between the combined power consumption and the target power to be the minimum, and the controller outputs a PWM signal to adjust an output voltage of the primary-circuit frequency converter until power consumption of the primary-circuit frequency converter is equal to the difference.

Description

A stepless adjustable constant power load Technical Field

[0001] This invention patent relates to the testing of performance parameters of power supply equipment and generator equipment, or the charging and discharging testing of batteries, and is particularly suitable for testing of variable loads with adjustable power, testing with high accuracy requirements, and testing with controllable equipment noise environment. Background Technology

[0002] With the gradual development of new energy and various power generation equipment manufacturing and development, test loads are being used more and more widely, and the requirements for loads are becoming increasingly higher. Technical issues

[0003] Testing equipment with constantly changing power requires real-time adjustable power based on the load, and the load parameters must be applied with a certain accuracy. Furthermore, the equipment must be highly operable and have a higher degree of automation. Solution

[0004] To address the aforementioned issues, this invention presents a multi-power level load with stepless adjustment from zero power to maximum power, capable of balancing three-phase current. It also achieves automated negative feedback for real-time, rapid adjustment, offering simple operation and high reliability.

[0005] A steplessly adjustable constant power load is provided, comprising a power resistor adjustment device, a heat dissipation system, and a controller. The power resistor adjustment device includes at least three fixed resistors with different resistance values ​​and a primary circuit frequency converter. Each fixed resistor is connected in series with a contactor as a load module, and the load modules are connected in parallel. The input terminal of the primary circuit frequency converter is connected to a test power supply, and the parallel connection of the load modules is connected to the output terminal of the primary circuit frequency converter. The primary circuit frequency converter serves as an adjustable voltage power consumption unit. The controller selects a loading combination from the load modules according to the target power. The loading combination is configured such that the power consumption of the combined load is less than the target power and the difference between the two is minimized. The controller outputs a PWM signal to adjust the output voltage of the primary circuit frequency converter until the power consumption of the primary circuit frequency converter equals the difference.

[0006] The heat dissipation system includes fans of a number corresponding to the number of fixed resistors, and fan frequency converters; each fixed resistor is equipped with a fan for air cooling, and all fans are connected in parallel to the output terminal of the fan frequency converter.

[0007] This includes the auxiliary power supply that draws power from the input terminal of the fan inverter.

[0008] The controller is electrically connected to the fan frequency converter and controls the fan speed based on the overall heat generation of each load module after parallel connection.

[0009] It includes a first temperature sensor and a second temperature sensor. The first temperature sensor is used to detect the inlet temperature of the cooling air blown out by the fan before it flows through the resistor, and the second temperature sensor is used to detect the outlet temperature of the cooling air after it flows through the resistor.

[0010] The control relationship between the cooling air flow rate and the heat generation is configured as follows:

[0011] L is the cooling air flow rate; Q is the total heat generated by the parallel resistors; ρ is the air density; C is the specific heat of air;

[0012] t0 is the outlet temperature of the cooling air after it flows through the resistor; t1 is the inlet temperature of the cooling air before it flows through the resistor.

[0013] Q = I²Rt, where I is the total current flowing through the parallel resistors, R is the overall resistance after the resistors are connected in parallel, and t is the running time.

[0014] The electrical interfaces of each load module use standardized components. Beneficial effects

[0015] Compared with existing technologies, it has the following advantages:

[0016] Rapidly and steplessly adjustable power: This load uses a frequency converter to change the voltage passing through the load, and can be continuously and subtly adjusted from 0kW to the maximum power according to P=U^2 / R. Compared with traditional contactors with large power ranges for adding and removing loads, this improves the adjustability accuracy and response time.

[0017] The device uses a variable frequency fan to dissipate heat from the power-consuming resistor. On the one hand, it can save the fan's power consumption under medium and low load conditions, and on the other hand, it can reduce the fan speed under medium and low load conditions, thereby reducing fan noise.

[0018] The load adopts a single modular parallel design. Each circuit is connected to a load circuit in parallel by an independent load and heat dissipation unit through a front-end switch. This facilitates the reallocation and replacement of the load in case of partial load failure, as well as subsequent maintenance. Attached Figure Description

[0019] Figure 1 shows an overview of the system components. The best embodiment of the present invention

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0021] Referring to Figure 1, the stepless adjustable constant power load includes a power resistor adjustment device, a heat dissipation system, and a controller.

[0022] The power resistor adjustment device includes at least three fixed resistors with different resistance values ​​and a primary circuit frequency converter. Each fixed resistor R1, R2, R3…Rn is connected in series with a contactor KM1, KM2…KMn as a load module M1. The electrical interfaces of the load modules use standardized components, forming a modular parallel design. All load modules M1 are connected in parallel. The input terminal of the primary circuit frequency converter is connected to a test power supply, and the parallel connection of all load modules is connected to the output terminal of the primary circuit frequency converter. The primary circuit frequency converter serves as an adjustable voltage power consumption unit. The controller selects a loading combination from the load modules based on the target power. The loading combination is configured such that the combined power consumption is less than the target power and the difference between the two is minimized. The controller outputs a PWM signal to adjust the output voltage of the primary circuit frequency converter until the power consumption of the primary circuit frequency converter equals the difference.

[0023] This device primarily uses a power-consuming resistor as the test load. Based on Ohm's law R=U / I and P=UI, a series of power level circuits R1, R2, R3…Rn are designed. The controller sends commands to control the corresponding contactors KM1, KM2…KMn in the appropriate load combination, achieving multi-power adjustable loading through parallel connection. Then, the test load size is precisely adjusted through a frequency converter. According to Ohm's law, P=U^2 / R. After the primary circuit frequency converter is connected to the circuit, the power response adjustment is achieved by adjusting the voltage of the primary circuit frequency converter.

[0024] The cooling system includes fans corresponding to the number of fixed resistors, and fan inverters. Each fixed resistor is equipped with a fan for air cooling. The fans F1, F2, F3…Fn are connected in parallel to the output of the fan inverters for convenient unified control and cost savings. Furthermore, an auxiliary power supply is configured, connected to the input of the fan inverters. This auxiliary power supply separates the power consumption of the fan inverters from that of the power-consuming resistors to avoid interference.

[0025] The cooling system uses a variable frequency fan, and the controller is electrically connected to the fan's frequency converter. The fan speed is controlled based on the overall heat generated by the parallel connection of all load modules. Specifically, it includes a first temperature sensor and a second temperature sensor. The first temperature sensor detects the inlet temperature of the cooling air blown out by the fan before it flows through the resistor, and the second temperature sensor detects the outlet temperature of the cooling air after it flows through the resistor.

[0026] The control relationship between cooling air flow rate and heat generation is configured as follows:

[0027] L is the cooling air flow rate; Q is the total heat generated by the parallel resistors; ρ is the air density; C is the specific heat of air;

[0028] t0 is the outlet temperature of the cooling air after it flows through the resistor; t1 is the inlet temperature of the cooling air before it flows through the resistor.

[0029] Q = I²Rt, where I is the total current flowing through the parallel resistors, R is the overall resistance after the resistors are connected in parallel, and t is the running time.

[0030] The control console monitors the load and power parameters in real time. When the load is unstable, the controller can automatically adjust it to a constant value. When a fault is detected in a certain gear or a channel heat dissipation fault, the controller can shut down the circuit KM and activate other KMs and cooling fans to continue operation.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A steplessly adjustable constant power load, characterized in that: Includes power resistor adjustment device, heat dissipation system and controller; The power resistor adjustment device includes at least three fixed resistors with different resistance values ​​and a primary circuit frequency converter. Each fixed resistor is connected in series with a contactor as a load module. The load modules are connected in parallel with each other. The input terminal of the primary circuit frequency converter is connected to the test power supply. The load modules are connected in parallel and then connected to the output terminal of the primary circuit frequency converter. The primary circuit frequency converter serves as an adjustable voltage power consumption unit. The controller selects a loading combination from each load module according to the target power. The loading combination is configured such that the power consumption of the combined module is less than the target power and the difference between the two is minimized. The controller outputs a PWM signal to adjust the output voltage of the primary circuit inverter until the power consumption of the primary circuit inverter is equal to the difference.

2. The steplessly adjustable constant power load according to claim 1, characterized in that: The heat dissipation system includes fans of a number corresponding to the fixed resistors, and fan frequency converters; Each fixed resistor is equipped with a fan for air cooling, and all fans are connected in parallel to the output terminal of the fan frequency converter.

3. The steplessly adjustable constant power load according to claim 1, characterized in that: This includes the auxiliary power supply that draws power from the input terminal of the fan frequency converter.

4. The steplessly adjustable constant power load according to claim 2, characterized in that: The controller is electrically connected to the fan frequency converter and controls the fan speed based on the overall heat generation of each load module after parallel connection.

5. The steplessly adjustable constant power load according to claim 4, characterized in that: It includes a first temperature sensor and a second temperature sensor. The first temperature sensor is used to detect the inlet temperature of the cooling air blown out by the fan before it flows through the resistor, and the second temperature sensor is used to detect the outlet temperature of the cooling air after it flows through the resistor. The control relationship between the cooling air flow rate and the heat generation is configured as follows: L is the cooling air flow rate; Q is the total heat generated by the parallel resistors; ρ is the air density; C is the specific heat of air; t0 is the outlet temperature of the cooling air after it flows through the resistor; t1 is the inlet temperature of the cooling air before it flows through the resistor. Q = I²Rt, where I is the total current flowing through the parallel resistors, R is the overall resistance after the resistors are connected in parallel, and t is the running time.

6. The steplessly adjustable constant power load according to claim 1, characterized in that: The electrical interfaces of each load module use standardized components.

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