Stepless adjustable constant power load

Abstract

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

Description

Technical Field

[0001] The patent of this invention relates to the performance parameter test of power supply equipment, generator equipment, or battery charge and discharge test, and is particularly suitable for variable load test with adjustable power, test with high precision requirements and controllable equipment noise environment. Background Art

[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 higher and higher, especially for equipment testing with constantly changing power. The power is required to be adjustable in real time on the basis of load, and to load with load parameters of a certain accuracy. In addition, the equipment is required to be highly operable and have a higher degree of automation. Summary of the invention

[0003] In order to solve the above problems, the present invention designs a load with multiple power levels that can be adjusted from zero power to maximum power steplessly, and a load device that can adjust the three-phase current balance. At the same time, automatic negative feedback real-time rapid adjustment is achieved, and the operation is simple and the reliability is strong.

[0004] Provided is a stepless adjustable constant power load, comprising a power resistor adjustment device, a heat dissipation system and a controller; the power resistor adjustment device comprises 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, each load module is connected in parallel, the input end of the primary circuit frequency converter is connected to a test power supply, each load module is connected in parallel to the 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 each load module according to the size of a target power, the loading combination is configured so that the combined power consumption is less than the target power and the difference between the two is minimized, and 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 is equal to the difference.

[0005] The heat dissipation system includes fans with a number corresponding to the fixed value resistors, and a fan inverter; each fixed value resistor is equipped with a fan for air cooling, and each fan is connected in parallel to the output end of the fan inverter.

[0006] This includes an auxiliary distribution power supply that is connected to the input end of the fan inverter to draw power.

[0007] The controller is electrically connected to the fan frequency converter, and controls the speed of the fan according to the overall heat generated by each load module after being connected in parallel.

[0008] Wherein, 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 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;

[0009] The control relationship between the cooling air flow rate and the heat generation is configured as follows:

[0010] L is the cooling air flow rate; Q is the total heat generated by the parallel resistor; ρ is the air density; C is the specific heat of air;

[0011] 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;

[0012] Q=I 2 Rt, I is the total current flowing through the parallel resistors, R is the overall resistance of the resistors after parallel connection, and t is the operating time.

[0013] Among them, the electrical interface of each load module uses unified standard parts.

[0014] Compared with the existing technology, it has the following advantages:

[0015] 1. Power is fast and infinitely adjustable: This load uses a frequency converter to change the voltage passing through the load, and can be adjusted continuously from 0kW to maximum power according to P=U^2 / R. Compared with the traditional gear power span, the contactor closes and opens to add and subtract loads, which improves the adjustable accuracy and response time.

[0016] 2. The device uses a variable frequency fan to dissipate heat from the power-consuming resistor. On the one hand, it can save fan power at medium and low loads, and on the other hand, it can reduce the speed at medium and low loads to reduce fan noise.

[0017] 3. The load adopts a single modular parallel connection design. Through the front-end switch, each circuit is connected in parallel to the primary load circuit by an independent load and heat dissipation unit, which is convenient for reallocation of substitute use and later maintenance when a local load fails. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 An overview of the system components is shown. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0020] See also Figure 1 The steplessly adjustable constant power load includes a power resistance adjustment device, a heat dissipation system and a controller.

[0021] The power resistor adjustment device includes at least three fixed resistors with different resistance values, and a primary circuit inverter. A single resistor tube is a single-tube resistor, and each fixed resistor R1, R2, R3...Rn is connected in series with a contactor KM1, KM2...KMn as a load module M1. The electrical interface of the load module uses unified standard parts to form a modular parallel design. The load modules M1 are connected in parallel with each other, and the input end of the primary circuit inverter is connected to the test power supply. After the load modules are connected in parallel, they are connected to the output end of the primary circuit inverter. The primary circuit inverter serves as an adjustable voltage power consumption unit. The controller selects a loading combination from each load module according to the size of the target power. The loading combination is configured so 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 inverter until the power consumption of the primary circuit inverter is equal to the difference.

[0022] This device mainly uses power-consuming resistors as the test load of the power supply. According to Ohm's law R=U / I and P=UI, the power gear circuits R1, R2, R3...Rn are designed after calculation. The controller sends commands to control the corresponding contactors KM1, KM2...KMn in the appropriate loading combination, and realizes multi-power adjustable loading in parallel. Then, the test load size is accurately adjusted through the frequency converter. According to the change of Ohm's law, P=U^2 / R is obtained. After the primary circuit frequency converter is connected to the loop, the voltage of the primary circuit frequency converter is adjusted to achieve rapid response adjustment of power.

[0023] The cooling system includes fans with the same number of fixed resistors and fan inverters; each fixed resistor is equipped with a fan for air cooling, and each fan F1, F2, F3...Fn is connected in parallel to the output end of the fan inverter, which is convenient for unified control and achieves cost savings. Furthermore, an auxiliary power distribution power supply is configured, and the input end of the fan inverter is connected to the power supply. The auxiliary power distribution power supply separates the power consumption of the fan inverter from the power-consuming resistor to avoid interference.

[0024] The cooling system uses a variable frequency fan, and the controller is electrically connected to the fan inverter to control the fan speed according to the overall heat generated by each load module in parallel. Specifically, 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 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.

[0025] The control relationship between the cooling air flow and the heat output is configured as follows:

[0026] L is the cooling air flow rate; Q is the total heat generated by the parallel resistor; ρ is the air density; C is the specific heat of air;

[0027] 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;

[0028] Q=I 2 Rt, I is the total current flowing through the parallel resistors, R is the overall resistance of the resistors after parallel connection, and t is the operating time.

[0029] The console detects the load and power parameters in real time. When the load is unstable, the controller can automatically adjust it to a constant state. When a gear failure or a channel heat dissipation failure is detected, the controller can turn off the KM of the circuit, attract other KMs and the cooling fan, and continue to run.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A stepless adjustable constant power load, characterized in that: It includes a power resistance adjustment device, a heat dissipation system and a controller; The power resistance 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, the input end of the primary circuit frequency converter is connected to a test power supply, and the load modules are connected in parallel to the 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 each load module according to the size of the target power, and the loading combination is configured so 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 inverter until the power consumption of the primary circuit inverter is equal to the difference.

2. The stepless adjustable constant power load according to claim 1, characterized in that: The cooling system includes fans with a number corresponding to the fixed value resistor, and a fan inverter; Each fixed value resistor is equipped with a fan for air cooling, and each fan is connected in parallel to the output end of the fan inverter.

3. The stepless adjustable constant power load according to claim 1, characterized in that: Including auxiliary distribution power supply for connecting to the input terminal of fan inverter.

4. The stepless adjustable constant power load according to claim 2, characterized in that: The controller is electrically connected to the fan frequency converter and controls the speed of the fan according to the overall heat generated by each load module after being connected in parallel.

5. The stepless 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 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 resistor; 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=I 2 Rt, I is the total current flowing through the parallel resistors, R is the overall resistance of the resistors after parallel connection, and t is the operating time.

6. The stepless adjustable constant power load according to claim 1, characterized in that: The electrical interfaces of each load module use unified standard parts.

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