CN114545123A

CN114545123A - Control method for improving dynamic performance of high-power direct-current electronic load

Info

Publication number: CN114545123A
Application number: CN202210170835.6A
Authority: CN
Inventors: 周玉柱
Original assignee: Hefei Kewei Power System Co ltd
Current assignee: Hefei Kewei Power System Co ltd
Priority date: 2022-02-23
Filing date: 2022-02-23
Publication date: 2022-05-27
Anticipated expiration: 2042-02-23
Also published as: CN114545123B

Abstract

The invention discloses a control method for improving the dynamic performance of a high-power direct-current electronic load, wherein the direct-current electronic load comprises a PWM (pulse-width modulation) rectifying circuit and a BUCK circuit, and the BUCK circuit is connected in parallel with the output end of the PWM rectifying circuit; respectively setting an interruption point A, C, E, G at adjacent peaks of the carriers, and respectively setting an update point B, D, F, H, J at an adjacent carrier bottom point starting from a first carrier bottom point after the interruption point A; before the moment of an interruption point A, the control mode is output current PI control, after the moment of the interruption point A, the control mode is switched into inductive current prediction control, the direct current electronic load regulates the load current from 0 ampere to the instruction current, and after the load current reaches the instruction current and is stabilized for a plurality of cycles, the control mode is switched back to the output current PI control by the inductive current prediction control; the invention has the advantages that: the method can obtain higher dynamic performance of the load current, thereby being beneficial to expanding the application field of the direct current electronic load.

Description

Control method for improving dynamic performance of high-power direct-current electronic load

Technical Field

The invention relates to the field of test equipment, in particular to a control method for improving dynamic performance of a high-power direct current electronic load.

Background

Compared with traditional energy-consuming loads such as resistors, the direct current electronic load can feed energy back to a power grid while having flexible application such as constant current, constant resistance and constant power, and is energy-saving and environment-friendly. The method has more and more important application requirements in occasions of battery pack charging and discharging equipment, semiconductor device testing systems, fuel cell characteristic load simulation, photovoltaic array simulation power supplies and the like.

The high dynamic performance and the high steady-state precision are core indexes of the direct current electronic load. The sampling resolution of hardware is improved, PI closed-loop control is carried out on load current, and the like, and high steady-state precision index of the direct-current electronic load can be achieved. However, high dynamic performance and high steady-state performance are often difficult to achieve simultaneously, the sampling rate of a high-precision sampling chip is slow, and the load current PI control takes a current error as an input quantity, and results such as slow current response are brought. Therefore, under the condition of not reducing the steady-state precision, the dynamic index of the load current is necessary to be improved, and the application field of the direct-current electronic load can be greatly expanded.

The prior art direct current electronic load has two realization modes of analog and digital: the dynamic indexes of the simulation mode can be guaranteed, but the general power is low and the price is high; the power device with high switching frequency is needed to meet the high dynamic index in a digital mode, and the fast devices of the MOSFET and the SIC have high switching frequency, but have small overcurrent capacity and high price. The IGBT has strong overcurrent capacity, but the switching frequency is low, and the conventional PI control is difficult to meet the index requirement. In addition, in order to meet the requirement of high-power testing, a parallel tube or parallel machine mode is needed to realize simulation, which brings complex control, low stability and high cost. Therefore, how to obtain higher dynamic performance of the load current is a new challenge faced by the dc electronic load.

Chinese patent publication No. CN 111327300 a discloses a high-power ac/dc integrated electronic load system and a control method thereof, including a plurality of PWM control bridges, a subtraction module, a modulation wave control module, a triangular carrier generation module and a comparison module, where each PWM control bridge is independent of the other, the subtraction module is in electrical signal connection with the modulation wave control module, the triangular carrier generation module and the modulation wave control module are both in electrical signal connection with the comparison module, and a phase-shift PWM waveform is generated by using a waveform generation method in the PWM control technology and a waveform iteration structure in the multiple superposition technology, so as to obtain a high equivalent switching frequency without increasing a single set of switching frequency and maintaining a main circuit topology structure, and reduce harmonic content in output waveforms of the system. The problems that when the load characteristic requirements of an electronic load realized by the power field effect transistor are variable and the power is high, self-oscillation is easily generated, operation is not facilitated, and high power current ripple and serious heating of the power transistor exist are well avoided. However, the patent application does not relate to the research on the load current dynamic performance of the direct current electronic load, and cannot obtain higher load current dynamic performance.

Disclosure of Invention

The technical problem to be solved by the invention is that the control method of the direct current electronic load in the prior art cannot obtain higher dynamic performance of load current, so that the application field of the direct current electronic load is difficult to expand.

The invention solves the technical problems through the following technical means: a control method for improving dynamic performance of a high-power direct-current electronic load comprises a PWM (pulse-width modulation) rectification circuit and a BUCK circuit, wherein the BUCK circuit comprises a switch tube S1 and a switch tube S2 which are connected in series, and the BUCK circuit is connected in parallel with the output end of the PWM rectification circuit; the PWM carrier wave is configured to increase or decrease the count, the top of the PWM interruption mode configuration bit is interrupted, the bottom of the PWM wave updating mode configuration bit is updated, the switching tubes S1 and S2 of the BUCK circuit are configured in a duty ratio complementary mode, the PWM is configured to symmetrically emit waves, interruption points A, C, E, G are respectively arranged at adjacent vertexes of the carrier wave, and updating points B, D, F, H, J are respectively arranged at adjacent bottom points of the carrier wave starting from a first bottom point of the carrier wave after the interruption point A; before the moment of an interruption point A, the inductive current average value of the BUCK circuit is 0 ampere, the control mode is output current PI control, after the moment of the interruption point A, the BUCK circuit receives instruction current, the control mode is switched into inductive current prediction control, the direct current electronic load regulates load current from 0 ampere to the instruction current, and after the load current reaches the instruction current and stabilizes for a plurality of cycles, the control mode is switched back to the output current PI control by the inductive current prediction control; the flow sensing prediction control includes four cases: calculating the duty ratio of the BD in the lower period at the moment of the PWM interruption point A; calculating the duty ratio of a lower period DF at the moment of an interruption point C; calculating the duty ratio of a lower period FH at the moment of an interruption point E; predicting the duty ratio of a lower period HJ at the moment of an interruption point G, and controlling the conduction time of the switching tubes S1 and S2 according to the duty ratio; the command current is negative, indicating that the current is directed from the outside to the inside.

According to the invention, through the inductive current prediction control, the load current of the direct current electronic load is quickly adjusted from 0 ampere to the instruction current, so that the quick response of the load current is realized, the inductive current prediction method corresponding to each situation is provided, the dynamic and steady-state indexes of the load current are respectively met by combining the inductive current prediction control and the load current PI control, and the high dynamic performance of the load current can be obtained, so that the application field of the direct current electronic load can be further expanded.

Further, the BUCK circuit comprises a switching tube S1, a switching tube S2, a capacitor C1, an inductor L and a capacitor C, wherein the capacitor C1 is connected in parallel to the output end of the PWM rectifier circuit, the switching tube S1 and the switching tube S2 are connected in series and then connected in parallel to two ends of the capacitor C1, one end of the inductor L and one end of the capacitor C are respectively connected to the collector and the emitter of the switching tube S2, and the other end of the inductor L is connected to the other end of the capacitor C.

Further, the switching tube S1 and the switching tube S2 are both IGBT tubes.

Furthermore, when the switch tube S1 is turned on, that is, the switch tube S2 is turned off, the inductive current IL rises, and when the switch tube S1 is turned off, that is, the switch tube S2 is turned on, the inductive current IL falls, and the inductive current IL is an average value of inductive currents sampled by the DSP at each interruption point.

Furthermore, the on-time of the switching tube S1 in the current period is Ton, the off-time of the switching tube S1 in the current time is Toff, and the switching period is Ts, which is Ton + Toff.

Furthermore, the rising inductance current variation when the switching tube S1 is turned on is Δ IL2, the falling inductance current variation when the switching tube S1 is turned off is Δ IL1, and Δ IL1 ═ Δ IL2, Δ IL1 ═ UoToff/L, Δ IL2 ═ Ton/L (Ud-Uo) during one switching period when inductance current is balanced, where Uo is the external voltage, L is the filter inductance current, and Ud is the BUCK circuit bus voltage.

Further, the calculating the duty ratio of the following period BD at the PWM break point a includes:

if the influenza at the moment of the break point A is predicted to be Ib, the Ib is IL +0.5 delta IL2-0.5 delta IL 1;

assuming that the switching tube S1 is fully disconnected in the next period BD, and the inductance current corresponding to the moment D is Id after the moment A is predicted to be 1.5 periods, the Id is Ib-UOTs/L;

if Ib > Iref, where Iref is the command current, that is, Ib does not reach the command current amplitude, the on-time Ton' of the switch S1 in the next cycle is 0, that is, the switch S2 is fully turned on.

Further, said calculating, at the break point C, a lower period DF duty cycle comprises:

predicting that the induced flow at the D moment is Id at the C moment, and then the Id is IL-0.5 UoTs/L;

assuming that a switching tube S1 is fully disconnected in the lower period DF, and If the inductance current corresponding to the F time is If after the C time predicts 1.5 periods, the If is Id-UoTs/L;

if > Iref, i.e. If has not yet reached the command current amplitude, the on-time Ton' of the switch tube S1 in the next cycle is 0, i.e. the switch tube S2 is fully on.

Further, said calculating, at the break point E, the duty cycle of the following period FH, includes:

predicting the inductive flow at the moment F to be If at the moment E, and then setting the If to be IL-0.5 UoTs/L;

assuming that a switching tube S1 is fully disconnected in a lower period FH, and an inductive current corresponding to a time H is Ih after a 1.5 period is predicted by a time E, then Ih is If-UOTs/L;

if Ih ≦ Iref, i.e. if Ih reaches and exceeds the commanded current magnitude, the duty cycle of the switching transistor S1 in the next period FH is not 0, and the S1 on-time Ton' is UoTs/Ud.

Still further, predicting the next cycle HJ duty cycle at the break point G includes:

predicting the influenza at the time H as Ih at the time G, and then determining that the Ih is IL +0.5 delta IL2-0.5 delta IL 1;

assuming that a switching tube S1 is fully disconnected in an HJ period, and the inductance current corresponding to the moment J is Ij after 1.5 periods are predicted at the moment G, and the Ij is Ih-UOTs/L;

if Ij is less than or equal to Iref, the current over-command value at the moment J is expected, the periodic duty ratio of HJ is not 0, the inductive current corresponding to the moment I is set as Ii, and the condition that Ii is equal to Iref is met;

if the predicted on-time of the switching tube S1 in the HJ period is Ton ' and the predicted off-time is Toff ', Δ IL1 '/L and Δ IL2 ' (Ud-Uo) Ton '/L are set, then the predicted current Ii ═ Ih-0.5 Δ IL1 ' +0.5 Δ IL2 ' corresponding to time I;

ton' ═ 2((Iref-Ih) L + Uo)/Ud was calculated from the above two steps.

The invention has the advantages that:

(1) according to the invention, through the inductive current prediction control, the load current of the direct current electronic load is quickly adjusted from 0 ampere to the instruction current, so that the quick response of the load current is realized, the inductive current prediction method corresponding to each situation is provided, the dynamic and steady-state indexes of the load current are respectively met by combining the inductive current prediction control and the load current PI control, and the high dynamic performance of the load current can be obtained, so that the application field of the direct current electronic load can be further expanded.

(2) The invention adopts the IGBT with large current bearing capacity as the switching device, improves the single machine capacity of the direct current electronic load, improves the steady state performance of the system, reduces the test cost, and realizes the high-power load current simulation by using the IGBT with low switching frequency as the power device.

(3) The hardware circuit of the invention has simple and reliable topology.

Drawings

Fig. 1 is a schematic diagram of an application of a dc electronic load in a control method for improving dynamic performance of a high-power dc electronic load according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a topology structure of a dc electronic load circuit in a control method for improving dynamic performance of a high-power dc electronic load according to an embodiment of the present invention;

fig. 3 is a timing chart illustrating PWM modulation and current sensing prediction in a control method for improving dynamic performance of a high-power dc electronic load according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1 to fig. 2, a control method for improving dynamic performance of a high-power dc electronic load, where the dc electronic load includes a PWM rectifier circuit and a BUCK circuit, the BUCK circuit includes a switching tube S1, a switching tube S2, a capacitor C1, an inductor L, and a capacitor C, the capacitor C1 is connected in parallel to an output end of the PWM rectifier circuit, the switching tube S1 and the switching tube S2 are connected in series and then connected in parallel to two ends of the capacitor C1, one end of the inductor L and one end of the capacitor C are respectively connected to a collector and an emitter of the switching tube S2, and the other end of the inductor L is connected to the other end of the capacitor C. The switch tube S1 and the switch tube S2 are IGBT tubes. The direct current electronic load application is schematically shown in fig. 1, and the direct current electronic load circuit topology based on the BUCK circuit is shown in fig. 2. In fig. 2, Ud is a bus voltage of the BUCK circuit, Uo is an external voltage, L is a filter inductance current, C is a filter capacitance value, Io is a load current, and IL is an inductance current average value sampled by each interrupt point DSP.

The dc electronic load comprises the following characteristics:

1) the direct current electronic load needs to realize accurate and rapid control on the load current Io;

2) the load current Io is realized by controlling the inductive current IL;

3) the output load current Io can be quickly controlled by quickly controlling the inductor current IL.

As shown in fig. 3, it is a timing diagram of PWM modulation mode and current sensing prediction, where PWM carriers are configured to increase or decrease counts, PWM interruption mode configuration bits are interrupted at the top, PWM wave updating mode configuration bits are updated at the bottom, BUCK circuit switching tubes S1, S2 are configured in duty ratio complementary mode, PWM is configured in symmetric wave generation, interrupt points A, C, E, G are respectively set at adjacent vertexes of carriers, and update points B, D, F, H, J are respectively set at adjacent bottom points of carriers starting with the first bottom point of the carrier after interrupt point a; generating interruption at the carrier peak A, calculating a new duty ratio D1, and updating the duty ratio D1 after the carrier bottom point B; and in the next period, interruption is generated at the top point C of the carrier, a new duty ratio D2 is calculated, the duty ratio D2 is updated after the bottom point D of the carrier, and the cycle is repeated.

When the switching tube S1 is switched on, that is, the switching tube S2 is switched off, the inductive current IL rises, when the switching tube S1 is switched off, that is, the switching tube S2 is switched on, the inductive current IL falls, and the inductive current IL is an inductive current average value sampled by the DSP at each interruption point.

The on-time of the current period of the switching tube S1 is Ton, the off-time of the current period of the switching tube S1 is Toff, and the switching period is Ts, which is Ton + Toff.

When the switching tube S1 is turned on, the rising inductance current variation is Δ IL2, when the switching tube S1 is turned off, the falling inductance current variation is Δ IL1, when the inductance current is balanced, Δ IL1 ═ Δ IL2, Δ IL1 ═ UoToff/L, Δ IL2 ═ Ud-Uo) Ton/L in one switching period, where Uo is the external voltage, L is the filter inductance current, and Ud is the BUCK circuit bus voltage.

Continuing to refer to fig. 3, before the moment of the interruption point a, the BUCK circuit operates at 0 ampere, the average value of the inductive current is 0 ampere, the control mode is output current PI control, and the output current PI control is the conventional control mode, which is not described herein again. After the moment of the interruption point A, the BUCK circuit receives a command current of 100A, the direct current electronic load hopes to regulate the load current from 0A to-100A (as a load, the current is a negative value, namely the current points to the inside from the outside) at the fastest speed, the control mode is switched into the inductive current prediction control, the direct current electronic load regulates the load current from 0A to the command current, and after the load current reaches the command current and is stabilized for a plurality of cycles, the control mode is switched back to the output current PI control by the inductive current prediction control; the flow sensing prediction control includes four cases: calculating the duty ratio of the BD in the lower period at the moment of the PWM interruption point A; calculating the duty ratio of a lower period DF at the moment of an interruption point C; calculating the duty ratio of a lower period FH at the moment of an interruption point E; predicting the duty ratio of a lower period HJ at the moment of an interruption point G, and controlling the conduction time of the switching tubes S1 and S2 according to the duty ratio; the command current is negative, indicating that the current is directed from the outside to the inside. The following description focuses on the current sensing prediction control method.

[ prediction case 1: calculating non-0 to 0 Duty cycle

At the moment of the PWM break point a, the duty ratio of the next period BD is calculated, which includes:

[ prediction case 2: calculate 0 Duty cycle to 0 Duty cycle ]

At the moment of the break point C, calculating the duty cycle of the lower period DF, including:

[ prediction case 3: calculating duty cycle 0 to non-0 ]

At the break point E, the next period FH duty cycle is calculated, including:

[ prediction case 4: calculating non-0 to non-0 Duty cycle

Predicting a lower cycle HJ duty cycle at the break point G, comprising:

ton' ═ 2((Iref-Ih) L + Uo)/Ud was calculated from the above two steps.

In summary, under the condition that the external voltages Uo and Ud are constant and the filter inductance current L is constant, the average value of the inductance current can reach the instruction current at the fastest speed through the software algorithm according to the method. All situations of the inductive flow change are not more than the 4 situations, and the invention provides a duty ratio prediction method corresponding to each situation. When the inductive current reaches the instruction value and stabilizes for a plurality of cycles, the control mode is switched into the output current PI control by inductive current prediction control, so as to improve the control precision of the load current.

Through the technical scheme, the load current of the direct current electronic load is quickly adjusted from 0 ampere to the instruction current through the inductive current prediction control, the quick response of the load current is realized, the inductive current prediction method corresponding to each situation is provided, the dynamic and steady indexes of the load current are respectively met by combining the inductive current prediction control and the load current PI control, the high dynamic performance of the load current can be obtained, and the application field of the direct current electronic load can be further expanded.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A control method for improving dynamic performance of a high-power direct-current electronic load is characterized in that the direct-current electronic load comprises a PWM (pulse-width modulation) rectifying circuit and a BUCK circuit, the BUCK circuit comprises a switching tube S1 and a switching tube S2 which are connected in series, and the BUCK circuit is connected in parallel with the output end of the PWM rectifying circuit; the method comprises the following steps that PWM carriers are configured to increase and decrease counts, the top of a PWM interruption mode configuration bit is interrupted, the bottom of a PWM wave updating mode configuration bit is updated, switching tubes S1 and S2 of a BUCK circuit are configured to be in a duty ratio complementary mode, PWM is configured to be symmetrical to emit waves, interruption points A, C, E, G are respectively arranged at adjacent vertexes of the carriers, and updating points B, D, F, H, J are respectively arranged at adjacent carrier bottom points starting from a first carrier bottom point behind an interruption point A; before the moment of an interruption point A, the inductive current average value of the BUCK circuit is 0 ampere, the control mode is output current PI control, after the moment of the interruption point A, the BUCK circuit receives instruction current, the control mode is switched into inductive current prediction control, the direct current electronic load regulates load current from 0 ampere to the instruction current, and after the load current reaches the instruction current and stabilizes for a plurality of cycles, the control mode is switched back to the output current PI control by the inductive current prediction control; the flow sensing prediction control comprises four situations: at the moment of a PWM break point A, calculating the duty ratio of a next period BD; calculating the duty ratio of a lower period DF at the moment of an interruption point C; calculating the duty ratio of a lower period FH at the moment of an interruption point E; predicting the duty ratio of a lower period HJ at the moment of an interruption point G, and controlling the conduction time of the switching tubes S1 and S2 according to the duty ratio; the command current is negative, indicating that the current is directed from the outside to the inside.

2. The control method for improving the dynamic performance of the high-power direct-current electronic load according to claim 1, wherein the BUCK circuit comprises a switching tube S1, a switching tube S2, a capacitor C1, an inductor L and a capacitor C, the capacitor C1 is connected in parallel to the output end of the PWM rectification circuit, the switching tube S1 and the switching tube S2 are connected in series and then connected in parallel to two ends of the capacitor C1, one end of the inductor L and one end of the capacitor C are respectively connected to the collector and the emitter of the switching tube S2, and the other end of the inductor L is connected to the other end of the capacitor C.

3. The control method for improving the dynamic performance of the high-power direct-current electronic load according to claim 1, wherein the switching tube S1 and the switching tube S2 are both IGBT tubes.

4. The method as claimed in claim 2, wherein when the switching transistor S1 is turned on, that is, when the switching transistor S2 is turned off, the inductive current IL rises, and when the switching transistor S1 is turned off, that is, when the switching transistor S2 is turned on, the inductive current IL falls, and the inductive current IL is an average inductive current value sampled by the DSP at each interrupt point.

5. The control method according to claim 4, wherein the on-time of the switching transistor S1 in the current period is Ton, the off-time of the switching transistor S1 in the current time is Toff, and the switching period is Ts, then Ts is Ton + Toff.

6. The control method for improving dynamic performance of a high power dc electronic load according to claim 5, wherein the rising inductance current variation when the switching tube S1 is turned on is Δ IL2, the falling inductance current variation when the switching tube S1 is turned off is Δ IL1, and Δ IL1 ═ Δ IL2, Δ IL1 ═ UoToff/L, Δ IL2 ═ Ud-Uo) Ton/L in a switching period during inductance balance, where Uo is an external voltage, L is a filter inductance current, and Ud is a BUCK circuit bus voltage.

7. The control method according to claim 6, wherein said calculating the duty cycle of the following period BD at the moment of the PWM break point A comprises:

if Ib > Iref, where Iref is the command current, i.e. Ib does not reach the command current amplitude, the on-time Ton' of the switch tube S1 in the next cycle is 0, i.e. the switch tube S2 is fully turned on.

8. The control method for improving the dynamic performance of the high-power dc electronic load according to claim 6, wherein the calculating the duty ratio of the lower period DF at the moment of the break point C comprises:

9. The control method according to claim 6, wherein said calculating the next FH duty cycle at the break point E comprises:

10. The control method for improving dynamic performance of a high power dc electronic load according to claim 6, wherein said predicting the lower period HJ duty cycle at the break point G comprises:

ton' ═ 2((Iref-Ih) L + Uo)/Ud was calculated from the above two steps.