A three-stage control system and method for a wide-range bidirectional DCDC electronic load

Abstract

The present application relates to a kind of wide-range bidirectional DCDC electronic load three-level control system and method, for solving the technical problems that the method exists in the test cost of traditional power supply test, test precision is low and debugging is difficult using multiple power supply load combination.The system includes input stage circuit, intermediate stage circuit unit, output stage circuit, the first control system of control input stage circuit, the second control system of control intermediate stage circuit unit and the third control system of control output stage circuit;The output end of third control system is connected to first control system.The input stage circuit of the present application adopts voltage outer loop control, current inner loop control mode, intermediate stage circuit adopts open loop control mode of fixed frequency and fixed duty cycle, output stage circuit adopts any mode outer loop control of constant current, constant voltage, constant resistance and constant power, inductance current loop inner loop control mode;Input stage circuit and output stage circuit synchronous control, intermediate stage circuit energy automatic distribution, realize bidirectional control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power supply testing, in particular to a three-stage control system and method of a wide-range bidirectional DCDC electronic load. BACKGROUND

[0002] In some special industries, the input and output of the electronic load of the power supply testing need to adapt to the wide-range input requirements, and usually a plurality of power supply load modules are combined to achieve this requirement. Although these methods can meet the basic testing requirements, they have high cost, low testing accuracy and difficult debugging. SUMMARY

[0003] The present application aims to solve the technical problems of high testing cost, low testing accuracy and difficult debugging of the traditional power supply testing method using multiple power supply load combinations, and provides a three-stage control system and method of a wide-range bidirectional DCDC electronic load.

[0004] To solve the above technical problems, the technical solution provided by the present application is as follows:

[0005] A three-stage control system of a wide-range bidirectional DCDC electronic load, characterized in that it comprises an input stage circuit, an intermediate stage circuit unit and an output stage circuit connected in sequence, and a first control system connected with the input stage circuit, a second control system connected with the intermediate stage circuit unit and a third control system connected with the output stage circuit.

[0006] The feedback output end of the third control system is connected with the input end of the first control system, for current feedforward to improve the response speed of the control system.

[0007] The input stage circuit is a bidirectional buck-boost circuit; the first control system adopts a voltage outer loop and current inner loop control mode to control the input stage circuit, for keeping the input stage bus voltage Vdc1 stable and output.

[0008] The intermediate stage circuit unit is a bidirectional isolation resonant soft switching circuit, comprising at least one intermediate stage circuit; the second control system adopts a fixed frequency and fixed duty cycle control mode to control the intermediate stage circuit unit, for voltage isolation conversion of the input stage bus voltage Vdc1 and the output stage bus voltage Vdc2.

[0009] The output stage circuit is a bidirectional buck-boost circuit; the third control system adopts a constant current, constant voltage, constant resistance or constant power outer loop control, and an inductance current inner loop control mode to control the output stage circuit, for realizing constant voltage, constant current, constant power or constant resistance output functions.

[0010] Further, the input stage circuit comprises a third capacitor C3, a third inductor L3, a ninth switch tube VT9, a tenth switch tube VT10 and a fourth capacitor C4;

[0011] The third capacitor C3 is connected between the input high end and the input low end; one end of the third inductor L3 is connected with the input high end; the gate of the ninth switch tube VT9 is connected with the first control system, the drain thereof is connected with the input stage bus high end, and the source thereof is connected with the drain of the tenth switch tube VT10 and the other end of the third inductor L3; the gate of the tenth switch tube VT10 is connected with the first control system, and the source thereof is connected with the input low end; the fourth capacitor C4 is connected between the input stage bus high end and the input low end.

[0012] Further, the intermediate stage circuit comprises a first switch tube VT1, a second switch tube VT2, a third switch tube VT3, a fourth switch tube VT4, a first capacitor C1, a second capacitor C2, a first resonant inductor L1, a second resonant inductor L2, an isolation transformer T1, a fifth switch tube VT5, a sixth switch tube VT6, a seventh switch tube VT7 and an eighth switch tube VT8;

[0013] The gates of the first switch tube VT1, the second switch tube VT2, the third switch tube VT3, the fourth switch tube VT4, the fifth switch tube VT5, the sixth switch tube VT6, the seventh switch tube VT7 and the eighth switch tube VT8 are respectively connected with the fixed frequency and fixed duty cycle driving signals PWM1-PWM8 output by the second control system;

[0014] The drain of the first switch tube VT1 is connected with the input stage bus high end, and the source thereof is connected with the drain of the second switch tube VT2 and one end of the second capacitor C2; the source of the second switch tube VT2 is connected with the input low end; the drain of the third switch tube VT3 is connected with the input stage bus high end, and the source thereof is connected with the drain of the fourth switch tube VT4 and one end of the first capacitor C1; the source of the fourth switch tube VT4 is connected with the input low end; the other end of the first capacitor C1 is connected with one end of the first resonant inductor L1, the other end of the second capacitor C2 is connected with one end of the second resonant inductor L2, and the other end of the first resonant inductor L1 and the other end of the second resonant inductor L2 are respectively connected with two ends of the primary winding of the isolation transformer T1;

[0015] The drain of the fifth switch tube VT5 is connected with the output stage bus high end, and the source thereof is connected with the drain of the sixth switch tube VT6 and one end of the secondary winding of the isolation transformer T1; the source of the sixth switch tube VT6 is connected with the output low end; the drain of the seventh switch tube VT7 is connected with the output stage bus high end, and the source thereof is connected with the drain of the eighth switch tube VT8 and the other end of the secondary winding of the isolation transformer T1; the source of the eighth switch tube VT8 is connected with the output low end.

[0016] Further, the output stage circuit comprises a fifth capacitor C5, an eleventh switch tube VT11, a twelfth switch tube VT12, a fourth inductor L4 and a sixth capacitor C6;

[0017] The fifth capacitor C5 is connected between the output stage bus high end and the output low end; the gate of the eleventh switch tube VT11 is connected to the third control system, the drain thereof is connected to the output stage bus high end, and the source thereof is connected to the drain of the twelfth switch tube VT12 and one end of the fourth inductor L4; the gate of the twelfth switch tube VT12 is connected to the third control system, and the source thereof is connected to the output low end; the other end of the fourth inductor L4 is connected to the output high end; and the sixth capacitor C6 is connected between the output high end and the output low end.

[0018] Further, the first control system comprises a first current sampling filter module, a first voltage sampling filter module, a first voltage loop regulator, a bus current calculation module, a first current loop regulator and a first PWM wave generator;

[0019] The input end of the first voltage sampling filter module is connected to the input stage bus high end, and the input end of the first current sampling filter module is connected to the input stage bus current sampling signal; the output end of the first voltage sampling filter module is connected to the input end of the first voltage loop regulator after being subtracted by the first voltage given value Vset1, the output end of the first voltage loop regulator is connected to the input end of the first current loop regulator after being subtracted by the output end of the first current sampling filter module and added by the output end of the bus current calculation module, the output end of the first current loop regulator is connected to the input end of the first PWM wave generator, and the output of the first PWM wave generator is a driving signal PWM01 and PWM02 connected to the gates of the ninth switch tube VT and the tenth switch tube VT10 respectively;

[0020] The third control system comprises an inductor current sampling filter module, a second voltage sampling filter module, a second voltage loop regulator, a second current sampling filter module, a second current loop regulator, a power calculation module, a power loop regulator, a resistance calculation module, a resistance loop regulator, an inductor current loop regulator and a second PWM wave generator;

[0021] The input end of the inductance current sampling filter module is connected with an inductance current sampling signal; the input end of the second voltage sampling filter module is connected with an output high end, and the output end thereof is connected with a second voltage given value Vset2 after being subtracted, and then is connected with the input end of a second voltage loop regulator; the input end of the second current sampling filter module is connected with an output stage current sampling signal, and the output end thereof is connected with a current given value Iset after being subtracted, and then is connected with the input end of a second current loop regulator; the input ends of the power calculation module are respectively connected with the output high end and the output stage current sampling signal, and the output end thereof is connected with a power given value Pset after being subtracted, and then is connected with the input end of a power loop regulator; the input ends of the resistance calculation module are respectively connected with the output high end and the output stage current sampling signal, and the output end thereof is connected with a resistance given value Rset after being subtracted, and then is connected with the input end of a resistance loop regulator;

[0022] The output end of any one of the second voltage loop regulator, the second current loop regulator, the power loop regulator and the resistance loop regulator is connected with the input end of the inductance current loop regulator after being subtracted from the output end of the inductance current sampling filter module, and the output end of the inductance current loop regulator is connected with the input end of a second PWM wave generator, and the output driving signal PWM03 and PWM04 of the second PWM wave generator are respectively connected with the gate of the eleventh switch tube VT11 and the twelfth switch tube VT12; the output high end and the output stage current sampling signal are respectively connected with the input ends of a bus current calculation module.

[0023] Further, the intermediate stage circuit unit comprises a plurality of intermediate stage circuits which are connected in parallel or in series.

[0024] The application further provides a three-stage control method of a wide-range bidirectional DCDC electronic load, which is characterized in that the method comprises the following steps:

[0025] 1) The switching frequency of the input stage circuit and the output stage circuit is kept within a switching frequency for synchronous control, and the output stage power calculated by the third control system is transmitted to the first control system as a feedforward signal;

[0026] 2) The input stage circuit adopts a voltage outer loop control and current inner loop control mode

[0027] The first control system calculates the input stage bus current by the output stage power, and the input stage bus current is used as the current feedforward control of the input stage circuit and is subjected to difference calculation with the feedback input stage bus current; the difference between the first voltage given value Vset1 and the feedback input stage bus voltage Vdc1 is used to control the duty cycle of the switch tube of the input stage circuit, so that the input stage bus voltage Vdc1 is kept stable output;

[0028] 3) The intermediate stage circuit unit adopts an open loop control mode with fixed frequency and fixed duty cycle

[0029] The switch tubes of the intermediate stage circuit unit are set to the same frequency, and the duty cycles are set to 0.5-2Dt / T, so that the input stage bus voltage Vdc1 and the output stage bus voltage Vdc2 are transformed in voltage, wherein Dt is the dead time, and T is the switching period of the switch tube of the intermediate stage circuit unit.

[0030] 4) The output stage circuit adopts any mode of constant current, constant voltage, constant resistance and constant power outer loop control, and inductance current loop control mode

[0031] The output values of the constant current, constant voltage, constant resistance and constant power modes and the sampled inductance current signal control the duty cycles of the switch tubes of the output stage circuit, so that the control system has any function of constant voltage, constant current, constant power and constant resistance.

[0032] Further, in step 2), the first control system subtracts the first voltage given value Vset1 from the input stage bus voltage Vdc1 filtered by the first voltage sampling and filtering module, and sends the difference value to the first voltage loop regulator; the output value of the first voltage loop regulator is given to the first current loop regulator, and the input stage bus current sampling signal filtered by the first current sampling and filtering module and the bus current feedforward signal calculated by the bus current calculation module are added and subtracted, and then sent to the first current loop regulator; the output value of the first current loop regulator is sent to the first PWM wave generator, and the first PWM wave generator generates driving signals PWM01 and PWM02 to drive the ninth switch tube VT9 and the tenth switch tube VT10 to act, respectively.

[0033] Further, in step 3), the intermediate stage circuit unit includes at least one intermediate stage circuit, and the intermediate stage circuit realizes bidirectional isolation through an isolation transformer T1; the frequencies of the first switch tube VT1, the fourth switch tube VT4, the fifth switch tube VT5 and the eighth switch tube VT8 are the same; the frequencies of the second switch tube VT2, the third switch tube VT3, the sixth switch tube VT6 and the seventh switch tube VT7 are the same; and the duty cycles are all 0.5-2Dt / T, wherein Dt is the dead time, and T is the switching period of the switch tube.

[0034] Further, in step 4), the third control system subtracts the second voltage given value Vset2 and the output stage voltage Vout filtered by the second voltage sampling filter module, and sends the difference into the second voltage loop regulator; subtracts the current given value Iset and the output stage current sampling signal filtered by the second current sampling filter module, and sends the difference into the second current loop regulator; sends the output stage current sampling signal and the second voltage sampling signal into the power calculation module, subtracts the power given value Pset and the output value of the power calculation module, and sends the difference into the power loop regulator; sends the output stage current sampling signal and the second voltage sampling signal into the resistance calculation module, subtracts the resistance given value Rset and the output value of the resistance calculation module, and sends the difference into the resistance loop regulator; and then, the output value of any control loop of the second voltage loop regulator, the second current loop regulator, the power loop regulator and the resistance loop regulator is taken as the given value of the inductance current loop regulator, and the difference between the given value and the inductance current sampling signal filtered by the inductance current sampling filter module is sent into the inductance current loop regulator; the output value of the inductance current loop regulator is sent into the second PWM wave generator, and the second PWM wave generator generates the driving signals PWM03 and PWM04 to drive the eleventh switch tube VT11 and the twelfth switch tube VT12 to act, respectively.

[0035] The beneficial effects of the present application compared with the prior art are:

[0036] 1. The three-stage control system of the wide-range bidirectional DCDC electronic load provided by the present application has the characteristics of high precision and high power density, and the input and output voltage ranges can be guaranteed to be within 20 times of the minimum value; and the circuit topology is simple, thereby reducing the test cost.

[0037] 2. The three-stage control system of the wide-range bidirectional DCDC electronic load provided by the present application is controlled in a decoupled manner among the three-stage circuits, and the control is simple; the intermediate-stage circuit unit and the output-stage circuit are independently controlled, and only the output power signal exists between the control of the input-stage circuit and the output stage, thereby improving the dynamic performance of the input-stage bidirectional energy switching and reducing the debugging difficulty.

[0038] 3. The three-stage control system of the wide-range bidirectional DCDC electronic load provided by the present application has the first capacitor C1 and the second capacitor C2, the first resonant inductor L1 and the second resonant inductor L2 of the isolation transformer T1 of the intermediate-stage circuit symmetrically arranged, thereby eliminating the common-mode voltage at both ends of the isolation transformer T1 and preventing the transformer from being broken down; the first switch tube VT1, the second switch tube VT2, the third switch tube VT3, the fourth switch tube VT4, the fifth switch tube VT5, the sixth switch tube VT6, the seventh switch tube VT7 and the eighth switch tube VT8 are symmetrically arranged, thereby realizing fast and automatic bidirectional energy flow.

[0039] 4. The three-stage control system of the wide-range bidirectional DCDC electronic load provided by the application, when the system power is not satisfied, the intermediate-stage circuit unit can be provided with multiple intermediate-stage circuits 2 in parallel for expanding the power, and when the system voltage is not satisfied, multiple intermediate-stage circuits 2 can be provided in series for raising the voltage, so that the system is suitable for a wide range and has great application prospects.

[0040] 5. The three-stage control method of the wide-range bidirectional DCDC electronic load provided by the application, the input-stage circuit adopts a voltage outer loop and current inner loop control mode to keep the input-stage bus voltage Vdc1 stable; the intermediate-stage circuit unit adopts a fixed-frequency and fixed-duty ratio control mode to realize automatic flow of bidirectional capability; the output-stage circuit adopts a constant current, constant voltage, constant resistance and constant power any mode outer loop control and inductance current loop inner loop control mode, so that the control system has the functions of constant voltage, constant current, constant power and constant resistance. At the same time, the switching frequency of the input-stage circuit and the output-stage circuit is kept within a switching frequency for synchronous control, the output-stage power calculated by the third control system is transmitted to the first control system as the input-stage feedforward signal, and the response speed of the control system is improved.

[0041] 6. The three-stage control method of the wide-range bidirectional DCDC electronic load provided by the application, which adopts input-stage circuit and output-stage circuit synchronous control and intermediate-stage circuit unit energy automatic distribution to realize bidirectional control and is suitable for a bidirectional DCDC electronic load with wide-range variable input and output. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The circuit topology of the three-stage control system of the wide-range bidirectional DCDC electronic load provided by the application;

[0043] Figure 2 The control block diagram of the input-stage circuit in the embodiment of the application;

[0044] Figure 3 The switching waveform diagram of the intermediate-stage circuit switch in the embodiment of the application;

[0045] Figure 4 The control block diagram of the output-stage circuit in the embodiment of the application.

[0046] Specific reference signs are as follows:

[0047] 1-input stage circuit; 2-intermediate stage circuit; 3-output stage circuit; 4-first control system; 5-second control system; 6-third control system; 7-first current sampling filter module; 8-first voltage sampling filter module; 9-first voltage loop regulator; 10-bus current calculation module; 11-first current loop regulator; 12-first PWM wave generator; 13-inductor current sampling filter module; 14-second voltage sampling filter module; 15-second current sampling filter module; 16-power calculation module; 17-resistance calculation module; 18-second voltage loop regulator; 19-second current loop regulator; 20-power loop regulator; 21-resistance loop regulator; 22-inductor current loop regulator; 23-second PWM wave generator. DETAILED DESCRIPTION

[0048] In order to make the advantages and characteristics of the present application more clear, the present application is further described in detail below in combination with the drawings and specific embodiments.

[0049] As shown in Figure 1 , a three-stage control system of a wide-range bidirectional DCDC electronic load includes an input stage circuit 1, an intermediate stage circuit unit, an output stage circuit 3 connected in sequence, and a first control system 4 connected with the input stage circuit 1, a second control system 5 connected with the intermediate stage circuit unit, and a third control system 6 connected with the output stage circuit 3. At the same time, the feedback output end of the third control system 6 is connected with the input end of the first control system 4, for current feedforward to improve the response speed of the control system.

[0050] The input stage circuit 1 is a bidirectional boost-buck circuit, including a third capacitor C3, a third inductor L3, a ninth switch tube VT9, a tenth switch tube VT10, and a fourth capacitor C4. The third capacitor C3 is connected between the input high end and the input low end; one end of the third inductor L3 is connected with the input high end; the gate of the ninth switch tube VT9 is connected with the first control system 4, the drain thereof is connected with the input stage bus high end, and the source thereof is connected with the drain of the tenth switch tube VT10 and the other end of the third inductor L3; the gate of the tenth switch tube VT10 is connected with the first control system 4, and the source thereof is connected with the input low end; the fourth capacitor C4 is connected between the input stage bus high end and the input low end.

[0051] As shown in Figure 2As shown, the first control system 4 adopts a voltage outer loop and current inner loop control mode to control the input stage circuit 1, for keeping the input stage bus voltage Vdcl stable. The first control system 4 comprises a first current sampling filter module 7, a first voltage sampling filter module 8, a first voltage loop regulator 9, a bus current calculation module 10, a first current loop regulator 11 and a first PWM wave generator 12. The input end of the first voltage sampling filter module 8 is connected to the high end of the input stage bus, and the input end of the first current sampling filter module 7 is connected to the input stage bus current sampling signal; the output end of the first voltage sampling filter module 8 is connected to the input end of the first voltage loop regulator 9 after being subtracted by the first voltage given value Vsetl, the output end of the first voltage loop regulator 9 is connected to the input end of the first current loop regulator 11 after being subtracted by the output end of the first current sampling filter module 7 and added by the output end of the bus current calculation module 10, the output end of the first current loop regulator 11 is connected to the input end of the first PWM wave generator 12, and the output of the first PWM wave generator 12 is a driving signal PWM01, PWM02, which is connected to the gate of the ninth switch tube VT9 and the tenth switch tube VT10, respectively.

[0052] The intermediate stage circuit unit is a bidirectional isolation resonant soft switching circuit, comprising at least one intermediate stage circuit 2. The intermediate stage circuit 2 comprises a first switch tube VT1, a second switch tube VT2, a third switch tube VT3, a fourth switch tube VT4, a first capacitor C1, a second capacitor C2, a first resonant inductor L1, a second resonant inductor L2, an isolation transformer T1, a fifth switch tube VT5, a sixth switch tube VT6, a seventh switch tube VT7, and an eighth switch tube VT8. The second control system 5 controls the intermediate stage circuit 2 in a constant frequency and constant duty ratio control mode, for voltage isolation conversion of the input stage bus voltage Vdc1 and the output stage bus voltage Vdc2. The gate of the first switch tube VT1 is connected to the first drive signal PWM1 of the second control system 5, the drain thereof is connected to the input stage bus high end, and the source thereof is connected to the drain of the second switch tube VT2 and one end of the second capacitor C2; the gate of the second switch tube VT2 is connected to the second drive signal PWM2 of the second control system 5, the source thereof is connected to the input low end; the gate of the third switch tube VT3 is connected to the third drive signal PWM3 of the second control system 5, the drain thereof is connected to the input stage bus high end, and the source thereof is connected to the drain of the fourth switch tube VT4 and one end of the first capacitor C1; the gate of the fourth switch tube VT4 is connected to the fourth drive signal PWM4 of the second control system 5, the source thereof is connected to the input low end; the other end of the first capacitor C1 is connected to one end of the first resonant inductor L1, the other end of the second capacitor C2 is connected to one end of the second resonant inductor L2, the other end of the first resonant inductor L1 and the other end of the second resonant inductor L2 are respectively connected to the two ends of the primary winding of the isolation transformer T1; the gate of the fifth switch tube VT5 is connected to the fifth drive signal PWM5 of the second control system 5, the drain thereof is connected to the output stage bus high end, and the source thereof is connected to the drain of the sixth switch tube VT6 and one end of the secondary winding of the isolation transformer T1; the gate of the sixth switch tube VT6 is connected to the sixth drive signal PWM6 of the second control system 5, the source thereof is connected to the output low end; the gate of the seventh switch tube VT7 is connected to the seventh drive signal PWM7 of the second control system 5, the drain thereof is connected to the output stage bus high end, and the source thereof is connected to the drain of the eighth switch tube VT8 and the other end of the secondary winding of the isolation transformer T1; the gate of the eighth switch tube VT8 is connected to the eighth drive signal PWM8 of the second control system 5, the source thereof is connected to the output low end. When the system power does not meet the requirements, multiple intermediate stage circuits 2 can be connected in parallel to expand the power, and when the system voltage does not meet the requirements, multiple intermediate stage circuits 2 can be connected in series to increase the voltage. In this embodiment, the intermediate stage circuit unit is provided as one intermediate stage circuit 2.

[0053] The output stage circuit 3 is a bidirectional buck-boost circuit, comprising a fifth capacitor C5, an eleventh switch tube VT11, a twelfth switch tube VT12, a fourth inductor L4 and a sixth capacitor C6. The fifth capacitor C5 is connected between the output stage bus high end and the output low end; the gate of the eleventh switch tube VT11 is connected to the third control system 6, the drain thereof is connected to the output stage bus high end, and the source thereof is connected to the drain of the twelfth switch tube VT12 and one end of the fourth inductor L4; the gate of the twelfth switch tube VT12 is connected to the third control system 6, and the source thereof is connected to the output low end; the other end of the fourth inductor L4 is connected to the output high end; and the sixth capacitor C6 is connected between the output high end and the output low end.

[0054] As shown in Figure 4 The third control system 6 adopts a constant current, constant voltage, constant resistance or constant power outer loop control, and an inductor current inner loop control mode to control the output stage circuit 3, so as to realize the constant voltage, constant current, constant power or constant resistance output function. The third control system 6 comprises an inductor current sampling filter module 13, a second voltage sampling filter module 14, a second voltage loop regulator 18, a second current sampling filter module 15, a second current loop regulator 19, a power calculation module 16, a power loop regulator 20, a resistance calculation module 17, a resistance loop regulator 21, an inductor current loop regulator 22 and a second PWM wave generator 23. The input end of the inductor current sampling filter module 13 is connected to an inductor current sampling signal; the input end of the second voltage sampling filter module 14 is connected to the output high end, and the output thereof is connected to the input end of the second voltage loop regulator 18 after being subtracted by a second voltage given value Vset2; the input end of the second current sampling filter module 15 is connected to an output stage current sampling signal, and the output thereof is connected to the input end of the second current loop regulator 19 after being subtracted by a current given value Iset; the input ends of the power calculation module 16 are respectively connected to the output high end and the output stage current sampling signal, and the output thereof is connected to the input end of the power loop regulator 20 after being subtracted by a power given value Pset; the input ends of the resistance calculation module 17 are respectively connected to the output high end and the output stage current sampling signal, and the output thereof is connected to the resistance loop regulator 21 after being subtracted by a resistance given value Rset; the output ends of the second voltage loop regulator 18, the second current loop regulator 19, the power loop regulator 20 and the resistance loop regulator 21 are subtracted by the output end of the inductor current sampling filter module 13 to connect the input end of the inductor current loop regulator 22, and the output end of the inductor current loop regulator 22 is connected to the input end of the second PWM wave generator 23, and the output of the second PWM wave generator 23 drives signals PWM03 and PWM04 to be connected to the gates of the eleventh switch tube VT11 and the twelfth switch tube VT12 respectively. The output high end and the output stage current sampling signal are connected to the input ends of the bus current calculation module 10 respectively.

[0055] The input stage circuit 1, the intermediate stage circuit 2 and the output stage circuit 3 of the application can flow energy in both directions, and the circuit topology is simple, and has the characteristics of high precision and high power density, and the input and output voltage ranges can be guaranteed to be within 20 times of the minimum value.

[0056] The three-stage control method of the wide-range bidirectional DC / DC electronic load comprises the following steps:

[0057] 1) The switching frequency of the input stage circuit 1 and the output stage circuit 3 is kept within a switching frequency for synchronous control, and the output stage power calculated by the third control system 6 is transmitted to the first control system 4 as a feedforward signal.

[0058] 2) The input stage circuit 1 adopts a voltage outer loop control and current inner loop control mode

[0059] The first control system 4 obtains a bus current feedforward signal by processing the output stage power feedforward signal through the bus current calculation module 10; the first control system 4 sends the difference between the first voltage given value Vset1 and the input stage bus voltage Vdc1 filtered through the first voltage sampling filter module 8 into the first voltage loop regulator 9; the output value of the first voltage loop regulator 9 is used as the given value of the first current loop regulator 11, and the first current loop regulator 11 adds and subtracts the input stage bus current sampling signal filtered through the first current sampling filter module 7 and the bus current feedforward signal calculated through the bus current calculation module 10, and sends the result into the first current loop regulator 11; the output value of the first current loop regulator 11 is sent into the first PWM wave generator 12, and the first PWM wave generator 12 generates driving signals PWM01 and PWM02 to drive the ninth switch tube VT9 and the tenth switch tube VT10 to act, so that the input stage bus voltage Vdc1 is kept stable.

[0060] 3) The intermediate stage circuit 2 adopts a fixed-frequency and fixed-duty-cycle open-loop control mode

[0061] As shown in Figure 3 , the intermediate stage circuit 2 realizes bidirectional isolation through the isolation transformer T1, so that the input stage bus voltage Vdc1 and the output stage bus voltage Vdc2 realize voltage conversion; the transformation ratio of the isolation transformer T1 is 1:n, so Vdc2=n*Vdc1, and since the value of the input stage bus voltage Vdc1 is stable, the value of Vdc2 is also a constant value. The frequencies of the first switch tube VT1, the second switch tube VT2, the third switch tube VT3, the fourth switch tube VT4, the fifth switch tube VT5, the sixth switch tube VT6, the seventh switch tube VT7 and the eighth switch tube VT8 in the intermediate stage circuit 2 are set to the same frequency, and the duty cycles are all set to 0.5-2Dt / T, where Dt is the dead time and T is the switching period of the intermediate stage switch tube.

[0062] 4) output stage circuit 3 adopts constant current, constant voltage, constant resistance and constant power any mode outer ring control, inductance current loop inner ring control mode

[0063] Third control system 6 difference value of second voltage given value Vset2 and output stage voltage Vout filtered through second voltage sampling filter module 14, sent to second voltage loop regulator 18; difference value of current given value Iset and output stage current sampling signal filtered through second current sampling filter module 15, sent to second current loop regulator 19; output stage current sampling signal and second voltage sampling signal are sent to power calculation module 16, difference value of power given value Pset and output value of power calculation module 16, sent to power loop regulator 20; output stage current sampling signal and second voltage sampling signal are sent to resistance calculation module 17, difference value of resistance given value Rset and output value of resistance calculation module 17, sent to resistance loop regulator 21; again, the output value of any control loop of second voltage loop regulator 18, second current loop regulator 19, power loop regulator 20 and resistance loop regulator 21 is given as the inductance current loop regulator 22, and the difference value of the inductance current sampling signal filtered through the inductance current sampling filter module 13 is sent to the inductance current loop regulator 22; the output value of the inductance current loop regulator 22 is sent to the second PWM wave generator 23, and the second PWM wave generator 23 generates driving signals PWM03 and PWM04, respectively driving the eleventh switch tube VT11 and the twelfth switch tube VT12 to act, so that the control system has any function of constant voltage, constant current, constant power and constant resistance.

[0064] In the application, the input stage circuit 1 and the output stage circuit 3 can adopt bidirectional BUCK / BOOST or four-tube BUCK / BOOST circuit topology.

[0065] The above description is only used to illustrate the technical solutions of the present application, and is not limited thereto. For ordinary skilled persons in the art, the specific technical solutions described in the above embodiments can be modified, or some technical features can be replaced by equivalent ones, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions protected by the present application.

Claims

1. A three-stage control system for a wide-range bidirectional DC-DC electronic load, characterized by: The input stage circuit (1), the intermediate stage circuit unit, the output stage circuit (3) are sequentially connected, and the first control system (4) is connected with the input stage circuit (1), the second control system (5) is connected with the intermediate stage circuit unit, and the third control system (6) is connected with the output stage circuit (3); The feedback output end of the third control system (6) is connected with the input end of the first control system (4), and is used for current feedforward to improve the response speed of the control system; The input stage circuit (1) is a bidirectional boost-buck circuit, the first control system (4) is used for keeping the input stage bus voltage Vdc1 stable by adopting voltage outer loop and current inner loop control mode to control the input stage circuit (1), and the second control system (5) is used for voltage isolation conversion of the input stage bus voltage Vdc1 and the output stage bus voltage Vdc2 by adopting constant frequency and constant duty ratio control mode to control the intermediate stage circuit unit; The output stage circuit (3) is a bidirectional boost-buck circuit, the third control system (6) is used for realizing constant voltage, constant current, constant power or constant resistance output function by adopting constant current, constant voltage, constant resistance or constant power outer loop control and inductance current inner loop control mode to control the output stage circuit (3); The first control system (4) comprises a first current sampling filter module (7), a first voltage sampling filter module (8), a first voltage loop regulator (9), a bus current calculation module (10), a first current loop regulator (11) and a first PWM wave generator (12); The input end of the first voltage sampling filter module (8) is connected with the high end of the input stage bus, and the input end of the first current sampling filter module (7) is connected with the input stage bus current sampling signal; the output end of the first voltage sampling filter module (8) is connected with the first voltage loop regulator (9) input end after being subtracted by the first voltage given value Vset1, the output end of the first voltage loop regulator (9) is subtracted by the output end of the first current sampling filter module (7) and then added by the output end of the bus current calculation module (10), and the output end of the first current loop regulator (11) is connected with the input end of the first PWM wave generator (12), and the output driving signal PWM01, PWM02 of the first PWM wave generator (12) is connected with the input stage circuit (1); The third control system (6) comprises an inductance current sampling filter module (13), a second voltage sampling filter module (14), a second voltage loop regulator (18), a second current sampling filter module (15), a second current loop regulator (19), a power calculation module (16), a power loop regulator (20), a resistance calculation module (17), a resistance loop regulator (21), an inductance current loop regulator (22) and a second PWM wave generator (23); ​ The input end of the inductance current sampling filter module (13) is connected with the output stage inductance current sampling signal; the input end of the second voltage sampling filter module (14) is connected with the output high end, and the output end is connected with the second voltage ring regulator (18) input end after being subtracted by the second voltage given value Vset2; the input end of the second current sampling filter module (15) is connected with the output stage current sampling signal, and the output end is connected with the second current ring regulator (19) input end after being subtracted by the current given value Iset; the input end of the power calculation module (16) is connected with the output high end and the output stage current sampling signal respectively, and the output end is connected with the power ring regulator (20) input end after being subtracted by the power given value Pset; the input end of the resistance calculation module (17) is connected with the output high end and the output stage current sampling signal respectively, and the output end is connected with the resistance ring regulator (21) after being subtracted by the resistance given value Rset; The output end of the inductance current sampling filter module (13) is connected with the output end of any one of the second voltage ring regulator (18), the second current ring regulator (19), the power ring regulator (20) and the resistance ring regulator (21) after being subtracted, and the input end of the inductance current ring regulator (22) is connected with the input end of the second PWM wave generator (23), and the output end of the inductance current ring regulator (22) is connected with the input end of the second PWM wave generator (23), and the output driving signal PWM03, PWM04 of the second PWM wave generator (23) is connected with the output stage circuit (3); the output high end and the output stage current sampling signal are connected with the input end of the bus current calculation module (10) respectively.

2. The three-stage control system of the wide-range bidirectional DCDC electronic load according to claim 1, characterized in that: The input stage circuit (1) comprises a third capacitor C3, a third inductor L3, a ninth switch tube VT9, a tenth switch tube VT10 and a fourth capacitor C4; The third capacitor C3 is connected between the input high end and the input low end; one end of the third inductor L3 is connected with the input high end; the gate of the ninth switch tube VT9 is connected with the first control system (4), the drain thereof is connected with the input stage bus high end, and the source thereof is connected with the drain of the tenth switch tube VT10 and the other end of the third inductor L3; the gate of the tenth switch tube VT10 is connected with the first control system (4), and the source thereof is connected with the input low end; the fourth capacitor C4 is connected between the input stage bus high end and the input low end.

3. The three-stage control system of the wide-range bidirectional DCDC electronic load according to claim 2, characterized in that: The intermediate stage circuit (2) comprises a first switch tube VT1, a second switch tube VT2, a third switch tube VT3, a fourth switch tube VT4, a first capacitor C1, a second capacitor C2, a first resonant inductor L1, a second resonant inductor L2, an isolation transformer T1, a fifth switch tube VT5, a sixth switch tube VT6, a seventh switch tube VT7 and an eighth switch tube VT8; The gates of the first switch tube VT1, the second switch tube VT2, the third switch tube VT3, the fourth switch tube VT4, the fifth switch tube VT5, the sixth switch tube VT6, the seventh switch tube VT7 and the eighth switch tube VT8 are respectively connected with the fixed frequency and fixed duty cycle driving signals PWM1-PWM8 output by the second control system (5); The drain of the first switch tube VT1 is connected with the input stage bus high end, and the source thereof is connected with the drain of the second switch tube VT2 and one end of the second capacitor C2; the source of the second switch tube VT2 is connected with the input low end; the drain of the third switch tube VT3 is connected with the input stage bus high end, and the source thereof is connected with the drain of the fourth switch tube VT4 and one end of the first capacitor C1; the source of the fourth switch tube VT4 is connected with the input low end; the other end of the first capacitor C1 is connected with one end of the first resonant inductor L1, the other end of the second capacitor C2 is connected with one end of the second resonant inductor L2, and the other ends of the first resonant inductor L1 and the second resonant inductor L2 are respectively connected with the two ends of the primary winding of the isolation transformer T1; The drain of the fifth switch tube VT5 is connected with the output stage bus high end, and the source thereof is connected with the drain of the sixth switch tube VT6 and one end of the secondary winding of the isolation transformer T1; the source of the sixth switch tube VT6 is connected with the output low end; the drain of the seventh switch tube VT7 is connected with the output stage bus high end, and the source thereof is connected with the drain of the eighth switch tube VT8 and the other end of the secondary winding of the isolation transformer T1; the source of the eighth switch tube VT8 is connected with the output low end.

4. The three-stage control system of the wide-range bidirectional DC-DC electronic load according to claim 3, characterized in that: The output stage circuit (3) comprises a fifth capacitor C5, an eleventh switch tube VT11, a twelfth switch tube VT12, a fourth inductor L4 and a sixth capacitor C6; The fifth capacitor C5 is connected between the output stage bus high end and the output low end; the gate of the eleventh switch tube VT11 is connected with the third control system (6), the drain thereof is connected with the output stage bus high end, and the source thereof is connected with the drain of the twelfth switch tube VT12 and one end of the fourth inductor L4; the gate of the twelfth switch tube VT12 is connected with the third control system (6), and the source thereof is connected with the output low end; the other end of the fourth inductor L4 is connected with the output high end; and the sixth capacitor C6 is connected between the output high end and the output low end.

5. The three-stage control system of the wide-range bidirectional DC-DC electronic load according to claim 4, characterized in that: The first PWM wave generator (12) outputs driving signals PWM01 and PWM02, which are respectively connected with the gates of the ninth switch tube VT9 and the tenth switch tube VT10; The second PWM wave generator (23) outputs driving signals PWM03 and PWM04, which are respectively connected with the gates of the eleventh switch tube VT11 and the twelfth switch tube VT12.

6. The three-stage control system of the wide-range bidirectional DC-DC electronic load according to claim 5, characterized in that: The intermediate stage circuit unit comprises a plurality of intermediate stage circuits (2) connected in parallel or in series.

7. A control method of a three-stage control system of a wide-range bidirectional DC-DC electronic load according to any one of claims 3 to 6, characterized in that, It comprises the following steps: 1) The input stage circuit (1) and the output stage circuit (3) are synchronously controlled at a switching frequency within a switching frequency range, and the output stage power calculated by the third control system (6) is transmitted to the first control system (4) as a feedforward signal; 2) The input stage circuit (1) adopts a voltage outer loop control and current inner loop control mode: The input stage bus current is calculated by the first control system (4) based on the output stage power, and is used as a current feedforward control of the input stage circuit (1) and a difference calculation of the feedback input stage bus current; the difference between the first voltage set value Vset1 and the feedback input stage bus voltage Vdc1 is used to control the duty cycle of the switching tube of the input stage circuit (1), so that the input stage bus voltage Vdc1 is kept stable and output; 3) The intermediate stage circuit unit adopts a fixed frequency and fixed duty cycle open loop control mode: The switching tube frequency of the intermediate stage circuit unit is set to the same frequency, and the duty cycle is set to 0.5-2Dt / T, so that the input stage bus voltage Vdc1 and the output stage bus voltage Vdc2 are converted, where Dt is the dead time and T is the switching period of the switching tube of the intermediate stage circuit unit; 4) The output stage circuit (3) adopts a constant current, constant voltage, constant resistance and constant power any mode outer loop control and inductance current inner loop control mode: The output value of the constant current, constant voltage, constant resistance and constant power any mode and the sampled inductance current signal are used to control the duty cycle of the switching tube of the output stage circuit (3), so that the control system has the functions of constant voltage, constant current, constant power and constant resistance.

8. The control method of the three-stage control system of the wide-range bidirectional DCDC electronic load according to claim 7, characterized in that: In step 2), the first control system (4) performs a difference calculation on the first voltage set value Vset1 and the input stage bus voltage Vdc1 filtered by the first voltage sampling filter module (8), and sends the difference to the first voltage loop regulator (9); the output value of the first voltage loop regulator (9) is used as a given value of the first current loop regulator (11), and the input stage bus current sampling signal filtered by the first current sampling filter module (7) and the bus current feedforward signal calculated by the bus current calculation module (10) are added and subtracted, and then sent to the first current loop regulator (11); the output value of the first current loop regulator (11) is sent to the first PWM wave generator (12), and the first PWM wave generator (12) generates driving signals PWM01 and PWM02 to drive the ninth switching tube VT9 and the tenth switching tube VT10 to act, respectively.

9. The control method of the three-stage control system of the wide-range bidirectional DCDC electronic load according to claim 8, characterized in that: In step 3), the intermediate stage circuit unit comprises at least one intermediate stage circuit (2) which is bidirectionally isolated by an isolation transformer T1; the first switch tube VT1, the fourth switch tube VT4, the fifth switch tube VT5 and the eighth switch tube VT8 have the same frequency; the second switch tube VT2, the third switch tube VT3, the sixth switch tube VT6 and the seventh switch tube VT7 have the same frequency; and the duty cycles are all 0.5-2Dt / T, wherein Dt is the dead time and T is the switching period of the switch tube.

10. The control method of the three-stage control system of the wide-range bidirectional DC-DC electronic load according to claim 9, characterized in that: In step 4), the third control system (6) subtracts the second voltage given value Vset2 from the output stage voltage Vout filtered by the second voltage sampling and filtering module (14) and sends the difference value to the second voltage loop regulator (18); subtracts the current given value Iset from the output stage current sampling signal filtered by the second current sampling and filtering module (15) and sends the difference value to the second current loop regulator (19); sends the output stage current sampling signal and the output stage voltage sampling signal to the power calculation module (16), subtracts the power given value Pset from the output value of the power calculation module (16) and sends the difference value to the power loop regulator (20); sends the output stage current sampling signal and the output stage voltage sampling signal to the resistance calculation module (17), subtracts the resistance given value Rset from the output value of the resistance calculation module (17) and sends the difference value to the resistance loop regulator (21); and then sends the output value of any one of the second voltage loop regulator (18), the second current loop regulator (19), the power loop regulator (20) and the resistance loop regulator (21) to the inductance current loop regulator (22) as a given value, subtracts the inductance current sampling signal filtered by the inductance current sampling and filtering module (13) from the inductance current loop regulator (22) and sends the difference value to the inductance current loop regulator (22); and the output value of the inductance current loop regulator (22) is sent to the second PWM wave generator (23) to generate the driving signals PWM03 and PWM04 to drive the eleventh switch tube VT11 and the twelfth switch tube VT12 to act, respectively.

Images