Constant current load control circuit with controllable peak factor and control method

Abstract

This invention relates to the field of AC electronic loads, and discloses a constant current load control circuit and method with controllable peak factor. It employs a dual effective value loop for output current peak factor and output current, achieving dual controllability of both effective value and peak factor. The analog PID instantaneous value outer loop control significantly improves the system's control response speed, while the capacitor current inner loop control technology suppresses resonant spikes and increases bandwidth, thus contributing to system stability. The hybrid analog-digital control method fully utilizes the calculation of the digital control effective value loop and the response speed of the analog instantaneous value, improving the reliability of system control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of AC electronic load, in particular to a controllable crest factor constant current load control circuit and control method. BACKGROUND

[0002] The crest factor is an important indicator in AC power supply or equipment, which reflects the characteristics of different electrical equipment to some extent. The greater the crest factor, the greater the input energy impact of the equipment, and the greater the harm to the power grid or power supply. Conversely, the smaller the crest factor, the better the characteristics of the electrical equipment, and the smaller the harm to the power supply system. In order to meet the input energy impact of different electrical equipment, AC power supply equipment needs to have the ability to output higher current crest factor. Therefore, in order to test the crest factor characteristics of AC power supply, controllable crest factor AC load is particularly important, which simulates the input impact characteristics of different electrical equipment by changing the current crest factor. However, the crest factor of most AC electronic loads is , and the crest factor is uncontrollable. SUMMARY

[0003] The present application aims to provide a controllable crest factor constant current load control circuit and control method, which can solve the above problems and realize dual control of RMS value and crest factor.

[0004] To achieve the above purpose, the following technical solutions are adopted:

[0005] A controllable crest factor constant current load control method includes digital control and analog control.

[0006] The digital control includes the following steps:

[0007] Crest factor RMS value control, calculate the given crest factor and the peak factor error of the sampled current crest factor , adjust the peak factor of the output current, act on the current RMS value given , output the new current RMS value given ;

[0008] Current RMS value control, calculate the output current RMS value and the output current error of the new current RMS value given , the error signal is calculated and then converted to digital-analog, output analog control given , control the output current waveform;

[0009] The analog control includes the following steps:

[0010] Output current instantaneous outer loop control, calculate the current instantaneous value point of the output current and the given signal error signal is calculated and outputted as the outer loop output signal ;

[0011] output current instantaneous inner loop control, calculate the capacitor current sampling signal and the outer loop output signal error, adjust the actual output current according to the error.

[0012] Further, the peak factor error is calculated by an integral element, and then acts on the current effective value given ;

[0013] The output current error is calculated by a PI element, and then digital-to-analog conversion is performed.

[0014] Further, the output current instantaneous outer loop control adopts PID control, and the output current instantaneous inner loop control adopts proportional element control.

[0015] Further, the peak factor effective value control includes the steps of:

[0016] Calculate the output current effective value :

[0017]

[0018] Wherein, n represents the number of discrete points of the current participating in the calculation of the effective value, represents the square of the current value of the nth point;

[0019] Calculate the sampling current peak factor:

[0020]

[0021] Wherein, is the sampling current peak value, is the sampling current effective value;

[0022] Calculate the peak factor error :

[0023]

[0024] Calculate the peak factor integral:

[0025]

[0026] Wherein, is the peak factor integral coefficient, is the peak error calculated in each period, and t is time.

[0027] Further, the current effective value control includes the steps of:

[0028] Calculate the output current error :

[0029]

[0030] Perform a proportional-integral (PI) calculation on the output current error:

[0031]

[0032] in, This is the proportional gain for the PI stage. For the integral coefficient of the PI element, The output current error is calculated for each cycle, where t is time.

[0033] Furthermore, the RMS value of the sampled current from the analog output is converted into a discrete digital value using an AD converter, resulting in... and .

[0034] A constant current load control circuit with controllable peak factor includes a digital control circuit, an analog control circuit, and an AD / DA conversion circuit;

[0035] The digital control circuit is an RMS loop, including a peak factor RMS loop and a current RMS loop. The peak factor RMS loop includes a first subtractor and an integrator, with the output of the first subtractor connected to the input of the integrator. The current RMS loop includes a multiplier, a second subtractor, and a PI loop. The input of the multiplier is connected to the output of the integrator, the output of the multiplier is connected to the input of the second subtractor, the other input of the second subtractor is connected to the output current RMS value, and the output of the second subtractor is connected to the input of the PI loop.

[0036] The AD / DA conversion circuit includes an AD conversion circuit and a DA conversion circuit. The input of the DA conversion circuit is connected to the output of the PI circuit, and the output of the DA conversion circuit is connected to the input of the analog control circuit. The AD converter converts the sampled analog output current into a discrete digital quantity, which is used to calculate the effective value of the sampled current. and sampling current peak factor ;

[0037] The analog control circuit includes a third subtractor, an instantaneous outer loop circuit, a fourth subtractor, and an instantaneous inner loop circuit. The instantaneous outer loop circuit includes a PID circuit, and the instantaneous inner loop circuit includes a proportional circuit. One input terminal of the third subtractor is connected to the output terminal of the DA conversion circuit, and the other input terminal of the third subtractor is connected to the current instantaneous value. The third subtractor's output is connected to the PID circuit's input; the PID circuit's output is connected to one input of the fourth subtractor; and the fourth subtractor's other input is connected to the capacitor current sampling signal. Connect the output of the fourth subtractor to the input of the proportional circuit.

[0038] Furthermore, the inputs to the first subtractor are the peak factor of the sampled current. Given peak factor The output is The two input terminals of the multiplier are the output terminal of the integrator and the current RMS value input terminal, respectively. .

[0039] Furthermore, the instantaneous outer loop circuit includes resistors R1, R2, and R3, capacitors C1, C2, C3, and C4, and operational amplifier OP1. The left end of resistor R1 is connected to the given input. Capacitor C1 and resistor R1 are connected in parallel. The left side of resistor R2 is connected to the current instantaneous value point. The capacitor C2 and resistor R2 are connected in parallel. The right sides of resistors R1, R2, C1, and C2 are all connected to the inverting input of operational amplifier OP1. One end of resistor R3 is connected to the non-inverting input of operational amplifier OP1, and the other end of resistor R3 is grounded. The left side of resistor R4 is connected to the inverting input of operational amplifier OP1, and the right end of resistor R4 is connected to the left side of capacitor C3. The right side of capacitor C3 is connected to the output of operational amplifier OP1. The series branch of resistor R4 and capacitor C3 is connected in parallel with capacitor C4.

[0040] The instantaneous inner loop circuit includes resistors R5, R6, R7, and R8, and operational amplifier OP2. The left side of resistor R6 is connected to the output terminal of operational amplifier OP1, and the right side of resistor R6 is connected to the inverting input terminal of operational amplifier OP2. The left side of resistor R5 is connected to the capacitor current sampling signal. Resistor R5 is connected to the inverting input of operational amplifier OP2 on the right side. One end of resistor R7 is connected to the non-inverting input of operational amplifier OP2, and the other end of resistor R7 is grounded. Resistor R8 is connected to the inverting input of operational amplifier OP2 on the left side, and the right end of resistor R8 is connected to the output of operational amplifier OP2 on the right side.

[0041] The advantages of this invention are:

[0042] This invention employs a dual effective value loop for output current peak factor and output current, achieving dual controllability of both effective value and peak factor. The simulated PID instantaneous value outer loop control greatly improves the system's control response speed, while the capacitor current inner loop control technology suppresses resonance spikes and improves bandwidth, which is beneficial to the system's stability.

[0043] The hybrid digital-analog control method makes full use of the calculation of the effective value loop of digital control and the response speed of the simulated instantaneous value, thereby improving the reliability of system control. Attached Figure Description

[0044] Figure 1 This is an overall block diagram of the constant current load control circuit with controllable peak factor according to Embodiment 1 of the present invention;

[0045] Figure 2 This is a simulation control circuit diagram for Embodiment 1 of the present invention. Detailed Implementation

[0046] 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.

[0047] Example 1

[0048] This embodiment discloses a constant current load control circuit with controllable peak factor, including a digital control circuit, an analog control circuit, and an AD / DA conversion circuit. Please refer to [reference needed]. Figure 1 .

[0049] The digital control circuit is an RMS loop, comprising a peak factor RMS loop and a current RMS loop. The peak factor RMS loop includes a first subtractor and an integrator. The inputs to the first subtractor are the sampled current peak factor. Given peak factor The output of the first subtractor is connected to the input of the integrator, and the output is... The current RMS loop includes a multiplier, a second subtractor, and a PI controller. One input of the multiplier is connected to the output of the integrator, and the other input is connected to the current RMS value setpoint. The output of the multiplier is connected to the input of the second subtractor, the other input of the second subtractor is connected to the effective value of the output current, and the output of the second subtractor is connected to the input of the PI circuit.

[0050] The AD / DA conversion circuit includes an AD conversion circuit and a DA conversion circuit. The input of the DA conversion circuit is connected to the output of the PI stage, and the output of the DA conversion circuit is connected to the input of the analog control circuit. The AD converter converts the sampled analog output current into a discrete digital quantity, which is used to calculate the effective value of the sampled current. and sampling current peak factor ;

[0051] The analog control circuit includes a third subtractor, an instantaneous outer loop circuit, a fourth subtractor, and an instantaneous inner loop circuit. The instantaneous outer loop circuit includes a proportional-integral-derivative (PID) circuit, and the instantaneous inner loop circuit includes a proportional (P) circuit. One input terminal of the third subtractor is connected to the output terminal of the DA converter circuit, and the other input terminal of the third subtractor is connected to the current instantaneous value. The third subtractor's output is connected to the PID circuit's input; the PID circuit's output is connected to one input of the fourth subtractor; and the fourth subtractor's other input is connected to the capacitor current sampling signal. Connect the output of the fourth subtractor to the input of the proportional circuit.

[0052] Please refer to Figure 2 The instantaneous outer loop circuit includes resistors R1, R2, and R3, capacitors C1, C2, C3, and C4, and operational amplifier OP1. The left end of resistor R1 is connected to the given input. Capacitor C1 and resistor R1 are connected in parallel. The left side of resistor R2 is connected to the current instantaneous value point. The following circuits are connected: capacitor C2 and resistor R2 are connected in parallel; the right sides of resistors R1, R2, capacitors C1 and C2 are all connected to the inverting input of operational amplifier OP1; one end of resistor R3 is connected to the non-inverting input of operational amplifier OP1, and the other end of resistor R3 is grounded; the left side of resistor R4 is connected to the inverting input of operational amplifier OP1, and the right side of resistor R4 is connected to the left side of capacitor C3; the right side of capacitor C3 is connected to the output of operational amplifier OP1; the series branch of resistor R4 and capacitor C3 is connected in parallel with capacitor C4; the output of operational amplifier OP1 is the outer loop output. , used as a given inner loop

[0053] The instantaneous inner loop circuit includes resistors R5, R6, R7, and R8, and operational amplifier OP2. The left side of resistor R6 is connected to the output terminal of operational amplifier OP1, and the right side of resistor R6 is connected to the inverting input terminal of operational amplifier OP2. The left side of resistor R5 is connected to the capacitor current sampling signal. Resistor R5 is connected to the inverting input of operational amplifier OP2 on its right side. One end of resistor R7 is connected to the non-inverting input of operational amplifier OP2, and the other end of resistor R7 is grounded. The left end of resistor R8 is connected to the inverting input of operational amplifier OP2, and the right end of resistor R8 is connected to the output of operational amplifier OP2. The output signal of operational amplifier OP2 is... It is used to control the output waveform.

[0054] Example 2

[0055] This embodiment discloses a specific control method for constant current load control with controllable peak factor. Please refer to the control block diagram. Figure 1 It includes a digital control section, an analog control section, and an AD / DA conversion section. The digital control section is an RMS loop, consisting of two parts: a current RMS loop and a peak factor RMS loop, which control the current accuracy and peak factor accuracy, respectively.

[0056] Peak factor effective value control, calculating a given peak factor With sampling current peak factor The peak factor error is accumulated through an integral element and applied to the given effective current value. The output current RMS value is given. It is used to adjust the peak factor of the output current.

[0057] Peak factor effective value control includes the following steps:

[0058] Calculate the effective value of the output current :

[0059]

[0060] Where n represents the number of current discrete points involved in calculating the effective value. This represents the square of the current value at the nth point;

[0061] Calculate the peak factor of the sampled current:

[0062]

[0063] in, The peak value of the sampled current. This is the effective value of the sampled current;

[0064] Calculate peak factor error :

[0065]

[0066] Calculate the peak factor integral:

[0067]

[0068] in, The peak factor integral coefficient, The peak error is calculated for each period, where t is time.

[0069] The peak factor control principle is that when the peak factor of the output current is less than the given peak factor, the given peak factor... and peak factor feedback The difference is positive, the integration stage accumulates the error positively, and the integral output is positive. Increase, used to increase the output peak factor; when the current peak factor is greater than the given peak factor, the given peak factor... and peak factor feedback The difference is negative, the integration stage accumulates the error negatively, and the integral output is... Decrease, used to reduce the output peak factor.

[0070] Current RMS control first outputs the peak factor RMS value loop. and the given effective value of the current The multiplier outputs the product. As a new given value for the output current RMS value loop, calculate the output current RMS value. and the given effective value of the new current The output current error is calculated using a PI converter and then converted from digital to analog to output the analog control setpoint. It is used for the control of the instantaneous value loop.

[0071] Calculate the output current error :

[0072]

[0073] Perform a proportional-integral (PI) calculation on the output current error:

[0074]

[0075] in, This is the proportional gain for the PI stage. For the integral coefficient of the PI element, The output current error is calculated for each cycle, where t is time.

[0076] The principle of RMS output current control is as follows: when the output current is less than the given RMS value... When a given valid value is given and the effective value of output current feedback The difference is positive, and the proportional-integral stage accumulates the error positively, with its effective value loop outputting the result. Increase, and thus increase the output current; when the output current exceeds the given effective value When a given valid value is given and the effective value of output current feedback The difference is negative, and the proportional-integral stage accumulates the error negatively, with its effective value loop outputting the result. This reduces the current, thereby controlling the output current to decrease.

[0077] The AD / DA conversion section is for converting between analog control and digital control. The AD converter converts the analog output current sample into a discrete digital quantity for calculating the current RMS value and peak factor. The DA converter converts the digital RMS output into an analog quantity and uses it as the reference for the instantaneous value loop to control the output current waveform.

[0078] The analog control section is an instantaneous value loop, including an outer loop control and an inner loop control for the output current. The outer loop uses proportional-integral-derivative (PID) control, which improves response speed and output accuracy, and enhances the steady-state and dynamic control of the output waveform. The inner loop uses capacitor current, which has high damping suppression, effectively suppressing resonance spikes in the controlled object, providing a wider bandwidth for the outer loop, which is beneficial for loop control and improves the loop's anti-interference capability.

[0079] The working principle of the instantaneous outer loop control of the output current is as follows: calculate the current instantaneous value of the output current. With a given signal The error signal is calculated by PID control and then output as the outer loop output signal. When the current instantaneous value of the output current is... Greater than the given signal At this time, the error signal is negative, and the PID controller adjusts the error signal to make its instantaneous value the outer loop. Reduce, decrease the actual output current; when the current instantaneous value of the output current is... Less than the given signal At this time, the error signal is positive, and the PID controller adjusts the error signal to make its instantaneous value the outer loop. Increase the current, thereby increasing the actual output current.

[0080] The working principle of the instantaneous inner loop control of the output current is as follows: calculate the capacitor current sampling signal. With outer loop output signal The error is used to adjust the actual output current, and the current instantaneous value of the capacitor current is adjusted accordingly. Greater than the outer loop output signal At this time, the error signal is negative, and the proportional element (P) of the inner loop adjusts the error signal to make its inner loop output... Reduce, lower the actual output current; when the current instantaneous value of the capacitor current is... Less than the outer loop output signal At this time, the error signal is positive, and the proportional element (P) adjusts the error signal to make its inner loop output... Increase the current, thereby increasing the actual output current.

[0081] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A constant current load control method with controllable peak factor, characterized in that, Including digital control and analog control; The digital control includes the following steps: Peak factor effective value control, calculating a given peak factor With sampling current peak factor The peak factor error is calculated using an integral element to obtain a new current peak factor. Then through the new current peak factor and the given effective value of current Multiply to output the new effective value of the current. ; Current RMS control, calculate the RMS value of the output current. and the given effective value of the new current The output current error is calculated, and the error signal is converted from digital to analog to output the analog control setpoint. Control the output current waveform; The simulation control includes the following steps: Output current instantaneous outer loop control, calculate the current instantaneous value of the output current. With a given signal The error signal is calculated and then output as the outer loop output signal. ; Instantaneous inner loop control of output current, calculating capacitor current sampling signal With outer loop output signal The error is adjusted by modifying the actual output current accordingly.

2. The constant current load control method with controllable peak factor according to claim 1, characterized in that, The output current error is calculated using a PI converter, and then digital-to-analog conversion is performed.

3. The constant current load control method with controllable peak factor according to claim 1, characterized in that, The instantaneous outer loop control of the output current adopts PID control, and the instantaneous inner loop control of the output current adopts proportional control.

4. The constant current load control method with controllable peak factor according to claim 2, characterized in that, The peak factor effective value control includes the following steps: Calculate the effective value of the output current : Where n represents the number of current discrete points involved in calculating the effective value. This represents the square of the current value at the nth point; Calculate the peak factor of the sampled current: in, The peak value of the sampled current. This is the effective value of the sampled current; Calculate peak factor error : Calculate the peak factor integral: in, The peak factor integral coefficient, The peak error is calculated for each period, where t is time.

5. The constant current load control method with controllable peak factor according to claim 2, characterized in that, The effective value control of the current includes the following steps: Calculate the output current error : Perform a proportional-integral (PI) calculation on the output current error: in, This is the proportional gain for the PI stage. For the integral coefficient of the PI element, The output current error is calculated for each cycle, where t is time.

6. The constant current load control method with controllable peak factor according to claim 1, characterized in that, The RMS value of the sampled current output from the analog circuit is converted into a discrete digital value through an analog-to-digital converter (AD converter). and .

7. A constant current load control circuit with controllable peak factor, characterized in that, Includes digital control circuits, analog control circuits, and AD / DA conversion circuits; The digital control circuit is an RMS loop, including a peak factor RMS loop and a current RMS loop. The peak factor RMS loop includes a first subtractor and an integrator, with the output of the first subtractor connected to the input of the integrator. The current RMS loop includes a multiplier, a second subtractor, and a PI loop. The input of the multiplier is connected to the output of the integrator, the output of the multiplier is connected to the input of the second subtractor, the other input of the second subtractor is connected to the output current RMS value, and the output of the second subtractor is connected to the input of the PI loop. The AD / DA conversion circuit includes an AD conversion circuit and a DA conversion circuit. The input terminal of the DA conversion circuit is connected to the output terminal of the PI circuit, and the output terminal of the DA conversion circuit is connected to the input terminal of the analog control circuit. The AD converter converts the sampled analog output current into a discrete digital quantity, which is used to calculate the effective value of the sampled current. and sampling current peak factor ; The analog control circuit includes a third subtractor, an instantaneous outer loop circuit, a fourth subtractor, and an instantaneous inner loop circuit. The instantaneous outer loop circuit includes a PID circuit, and the instantaneous inner loop circuit includes a proportional circuit. One input terminal of the third subtractor is connected to the output terminal of the DA conversion circuit, and the other input terminal of the third subtractor is connected to the current instantaneous value. The third subtractor's output is connected to the PID circuit's input; the PID circuit's output is connected to one input of the fourth subtractor; and the fourth subtractor's other input is connected to the capacitor current sampling signal. Connect the output of the fourth subtractor to the input of the proportional circuit.

8. The constant current load control circuit with controllable peak factor according to claim 7, characterized in that, The inputs to the first subtractor are the peak factor of the sampling current. Given peak factor The output is The two input terminals of the multiplier are the output terminal of the integrator and the current RMS value input terminal, respectively. .

9. The constant current load control circuit with controllable peak factor according to claim 7, characterized in that, The instantaneous outer loop circuit includes resistors R1, R2, and R3, capacitors C1, C2, C3, and C4, and operational amplifier OP1. The left end of resistor R1 is connected to the given input. Capacitor C1 and resistor R1 are connected in parallel. The left side of resistor R2 is connected to the current instantaneous value point. The capacitor C2 and resistor R2 are connected in parallel. The right sides of resistors R1, R2, C1, and C2 are all connected to the inverting input of operational amplifier OP1. One end of resistor R3 is connected to the non-inverting input of operational amplifier OP1, and the other end of resistor R3 is grounded. The left side of resistor R4 is connected to the inverting input of operational amplifier OP1, and the right end of resistor R4 is connected to the left side of capacitor C3. The right side of capacitor C3 is connected to the output of operational amplifier OP1. The series branch of resistor R4 and capacitor C3 is connected in parallel with capacitor C4. The instantaneous inner loop circuit includes resistors R5, R6, R7, and R8, and operational amplifier OP2. The left side of resistor R6 is connected to the output terminal of operational amplifier OP1, and the right side of resistor R6 is connected to the inverting input terminal of operational amplifier OP2. The left side of resistor R5 is connected to the capacitor current sampling signal. Resistor R5 is connected to the inverting input of operational amplifier OP2 on the right side. One end of resistor R7 is connected to the non-inverting input of operational amplifier OP2, and the other end of resistor R7 is grounded. Resistor R8 is connected to the inverting input of operational amplifier OP2 on the left side, and the right end of resistor R8 is connected to the output of operational amplifier OP2 on the right side.

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