CN201303290Y - Direct-current stabilized power supply for achieving low ripple with IGBT series-parallel mixture - Google Patents

Abstract

A DC steady-current power supply that uses IGBT series-parallel hybrid to realize low ripple, belongs to the field of automatic control technology and power electronics technology, and relates to a power conversion circuit based on a large-capacity IGBT device, including: incoming line filter circuit, phase shifting Circuit; input rectifier filter circuit; energy storage circuit; pre-stage step-down chopper circuit; front passive filter circuit; post-stage step-down chopper circuit; rear passive filter circuit; output passive filter circuit; voltage sensor circuit ; Current sensor circuit; A control circuit for controlling the operation of the overall circuit. The utility model can adopt water cooling or forced air cooling, and has the advantages of high long-term current stability, low voltage (current) ripple, fast response, high adjustment precision, small volume, high efficiency and low noise of the device.

Description

Using IGBT Series-Parallel Hybrid to Realize Low Ripple DC Steady Current Power Supply

technical field

The utility model belongs to the field of automatic control technology and power electronics technology, and relates to a power conversion circuit based on a large-capacity IGBT device. In occasions with high performance requirements, IGBT (Insalated-Gate Bipolar Transistor, Insulated Gate Bipolar Transistor) series-parallel hybrid is used to achieve a low-ripple DC steady-current power supply.

Background technique

In important fields such as basic scientific research, medical and health care, rail transit, and national defense industry, it is usually necessary to use a high-current steady-current power supply to supply excitation current to the magnet. These applications have strict requirements on the stability of the magnetic field. To ensure the long-term stability of the magnetic field, it is necessary to ensure that the output current of the constant current power supply has a high degree of stability and extremely low voltage (current) ripple. At present, the known power supply of this type generally adopts thyristor phase-controlled rectification power supply, which is composed of thyristor rectification, passive filtering, regulation control and other links. This conventional power supply has the advantages of large capacity, simple system structure, and low price of controllable components. And easy to realize the characteristics of magnetic field energy feedback. However, factors such as unbalanced AC grid voltage, inconsistent turn-on/turn-off characteristics of rectifier components, and unsatisfactory component characteristics will all generate non-characteristic sub-voltage (current) harmonics, which are directly manifested as large output voltage (current) ripples. . If a passive filter is used to eliminate voltage (current) characteristics and non-characteristic sub-harmonics, the size of the passive filter will increase, the cost of the power supply will be increased, and the dynamic performance of the system will be deteriorated.

In order to solve the problem of large output voltage (current) ripple of the thyristor phase-controlled rectification power supply, the existing power supply products mostly adopt the method of connecting linear adjustment transistors (high-power triodes) in series in the main circuit. Figure 1 shows the method of this method Circuit diagram. In Figure 1, the three-phase AC power supply U, V, W is connected to the three-phase thyristor rectifier unit A1 through the line reactor L1, and the rectified output is connected to the filter inductor L2 (common mode choke coil) and then connected to both ends of the capacitor C1. C2 and resistor R1 are connected in series and connected in parallel with C1. L2, C1, C2, and R1 form a passive filter to filter the characteristic harmonics of the three-phase rectification. The positive end of C1 is connected to the collector c of the linear adjustment tube V1, the wire of the emitter e of V1 passes through the current sensor U1 and is connected to the load, and the other end of the load is connected to the negative end of C1. The current feedback signal output by U1 is sent to the error amplifier A2 for comparison with the current given reference signal, and the output signal of A2 is connected to the base b of V1 to drive the linear adjustment tube to work. V1 works in the linear region, which is equivalent to a variable resistor. The output voltage ripple after the passive filter is absorbed by the voltage drop V _CE of the collector c-emitter e of the linear adjustment tube V1. When the DC output current increases due to the increase of the input voltage or the decrease of the load impedance, the base voltage of the linear adjustment tube V1 decreases, and the resistance value of its equivalent resistance increases, so that the output current decreases, so as to keep the current feedback signal equal to the current given base signal. This negative feedback control also works when the output current drops due to a drop in input voltage or an increase in load impedance. At this time, the output of the error amplifier will increase the base voltage of V1, reduce the collector-emitter resistance, and increase the DC output current, so that the current feedback signal is equal to the current given reference signal. Therefore, the advantages of this type of power supply are small ripple and high stability, and the disadvantages are large power consumption, low efficiency, large volume and poor reliability of the linear adjustment tube.

Another feasible way is to use active filtering technology, which can effectively cancel the characteristic and non-characteristic sub-harmonics. Figure 2 shows a schematic circuit diagram of this method. In Figure 2, the three-phase AC power supply U, V, W is connected to the three-phase thyristor rectifier unit A3 through the line reactor L3, and the rectified output is connected to the filter inductor L4 (common mode choke coil) and then connected to both ends of the capacitor C3. C4 and resistor R2 are connected in series and connected in parallel with C3. L4, C3, C4, and R2 form a passive filter to filter the characteristic harmonics of the three-phase rectification. Both ends of C3 are also connected in parallel with the output of A4, which is composed of an IGBT single-phase full-bridge inverter circuit, and an external AC220V power supply is used to supply power to A4. The positive wire of C3 passes through the current sensor U2 and is connected to the load, and the other end of the load is connected to the negative terminal of C3. The current signal output by U2 is sent to the error amplifier A5 for comparison with the current given reference signal. The output signal of A5 is isolated and amplified and connected to the gate of the IGBT in A4 to drive the active filter to work. The working principle of this circuit is: use the current sensor U2 to collect the current on the DC output line, and then perform ripple separation processing on the obtained current signal to obtain a ripple reference signal, which is used as the PWM (Pulse Width Modulation, pulse width modulation) The modulation signal is compared with the triangular wave to obtain the switching signal, which is used to control the IGBT single-phase bridge. According to the principle of PWM technology, reverse the switching signals of the upper and lower bridge arms to obtain a ripple current that is equal in size and opposite to the ripple signal on the line, and offset the ripple current on the line. This is feedforward control part. If it is necessary to further improve the filtering effect, then feed back the ripple component of the line current after the active filter access point, and use it as the input of the regulator to adjust the error of the feedforward control. The active filter A4 and the passive filter are used together in the whole system, that is, the passive filter performs large-capacity filter compensation, and the active filter performs fine-tuning to further suppress the output voltage (current) ripple and achieve the best filtering the goal of. However, due to the complexity of the non-characteristic sub-harmonic spectrum of this scheme, it is difficult to design and calculate the frequency selection network of the control system, and the workload of on-site debugging is huge.

Utility model content

The purpose of the utility model is to eliminate the shortcomings and deficiencies of the above-mentioned scheme, and design a kind of IGBT series-parallel hybrid with high long-term current stability, low voltage (current) ripple, fast response, high adjustment precision, small volume and high efficiency. Low ripple DC power supply.

In order to solve the above-mentioned technical problems, the utility model adopts the following technical solutions:

A high-precision, low-ripple DC steady-current power supply using IGBT series-parallel hybrids, including:

Incoming line filter circuit to attenuate the noise interference between the power grid and the power supply;

A phase shifting circuit for generating a phase shift of 15° from the electrical signal processed by the incoming filter circuit;

An input rectifying and filtering circuit for rectifying and filtering the phase-shifted electrical signal;

An energy storage circuit for forming two voltage sources;

The pre-stage step-down chopper circuit powered by the energy storage circuit;

A front passive filter circuit used to suppress the output ripple of the previous step-down chopper circuit;

The rear step-down chopper circuit powered by the front passive filter circuit;

A post-passive filter circuit used to suppress the output ripple of the post-stage step-down chopper circuit;

A passive filter circuit at the output to suppress the total output ripple;

A voltage sensor circuit used to sample the output voltage of the previous-stage step-down chopper circuit and feed it back to the previous-stage step-down chopper circuit;

A current sensor circuit used to sample the output current of the subsequent step-down chopper circuit and feed it back to the subsequent step-down chopper circuit;

A current sensor circuit used to sample the total output current and feed it back to the subsequent step-down chopper circuit;

A control circuit used to control the operation of the overall circuit.

The incoming line filter circuit is composed of filters respectively connected to each grid line.

The rectifying and filtering circuit at the input end includes a three-phase rectifying bridge and a filtering inductor.

The three-phase rectifier bridge includes A1, A2, A3, and A4 rectifier bridges, wherein A1, A2 are connected in series, and A3, A4 are connected in series to form 12-pulse rectifiers respectively. The two 12-pulse rectifiers form 24 rectifiers when viewed from the grid side. Pulse rectification.

The pre-stage step-down chopper circuit adopts a step-down chopper circuit bridge structure, at least two step-down chopper circuits are connected in parallel, and the output end of each step-down chopper circuit is connected to the front passive filter circuit.

The front passive filter circuit is composed of a high-frequency inductor and a filter capacitor.

The step-down chopper circuit of the rear stage adopts a step-down chopper circuit bridge structure, at least two step-down chopper circuits are connected in parallel, and the output end of each step-down chopper circuit is connected to the rear passive filter circuit.

A current sensor is provided at the output end of the rear passive filter circuit.

The input end of the control circuit is connected with the output of the current sensor and the voltage sensor, and the output of the control circuit is respectively connected with the grids of the IGBTs in the previous step-down chopper circuit and the rear-stage step-down chopper circuit.

The control circuit includes a given current reference, a total current closed-loop regulator, a current-sharing closed-loop regulator, an oscillator, a frequency division-phase shifting circuit, a pulse forming circuit, a proportioner, a voltage closed-loop regulator, a triangular wave generating circuit, and a pulse forming circuit. circuit, subtractor.

The utility model can adopt water cooling or forced air cooling, and has the advantages of high long-term current stability, low voltage (current) ripple, fast response, high adjustment precision, small volume, high efficiency and low noise of the device.

Description of drawings

Fig. 1 is the circuit schematic diagram of the known high-power power supply that has adopted thyristor phase-controlled rectification plus series-connected linear adjustment tube;

Fig. 2 is the circuit diagram of the known high-power power supply that has adopted thyristor phase-controlled rectification and active filter;

Fig. 3 is a schematic circuit diagram of the utility model;

Fig. 4 is the control circuit block diagram of the utility model.

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described:

Use IGBT series-parallel hybrid to realize low ripple DC steady current power supply, including:

The incoming line filter circuit is used to attenuate the noise interference of the power grid and the power supply to each other, and the incoming line filter circuit is composed of incoming line filters U11~U14;

It is used to generate a phase-shifting circuit with a phase shift of 15° for the electrical signal processed by the incoming filter circuit; the secondary windings of the transformers T1~T4 are phase-shifted by 15°;

The input rectification and filter circuit for rectifying and filtering the phase-shifted electrical signal includes three-phase rectifiers A1 and A2 connected in series to form a 12-pulse rectifier, and A3 and A4 connected in series to form a 12-pulse rectifier. Observe these two rectifiers from the grid side 12-pulse rectification constitutes 24-pulse rectification;

The energy storage circuit used to form two voltage sources is composed of filter inductors L1, L2 and energy storage capacitors C11-C14;

The pre-stage step-down chopper circuit powered by the energy storage circuit, the pre-stage step-down chopper circuit adopts a step-down chopper circuit bridge structure, and at least two step-down chopper circuits are connected in parallel;

The front passive filter circuit is used to suppress the output ripple of the previous step-down chopper circuit. The front passive filter circuit is composed of a high frequency inductor and a filter capacitor.

The rear-stage step-down chopper circuit powered by the front passive filter circuit, the latter-stage step-down chopper circuit adopts a step-down chopper circuit bridge structure, and at least two step-down chopper circuits are connected in parallel;

The rear passive filter circuit is used to suppress the output ripple of the step-down chopper circuit of the rear stage. The rear passive filter circuit is composed of a high-frequency inductor and a filter capacitor, and the output end of the rear passive filter circuit is provided with a current sensor.

The passive filter circuit at the output end is used to suppress the total output ripple. The passive filter circuit at the output end is composed of filter inductors L11, L12, capacitors C9, C10, and resistor R1.

A voltage sensor circuit used to sample the output voltage of the previous-stage step-down chopper circuit and feed it back to the previous-stage step-down chopper circuit;

A current sensor circuit used to sample the output current of the subsequent step-down chopper circuit and feed it back to the subsequent step-down chopper circuit;

A current sensor circuit used to sample the total output current and feed it back to the subsequent step-down chopper circuit;

A control circuit used to control the operation of the overall circuit.

In the utility model, the incoming line filters U11-U14 are used to attenuate the noise interference between the grid and the power supply. The secondary windings of transformers T1~T4 are phase-shifted by 15°. Three-phase rectifiers A1 and A2 are connected in series to form 12-pulse rectification. A 24-pulse rectifier is formed, which will greatly reduce the harmonics of the AC input current on the grid side and improve the power factor, thereby reducing the interference of the rectifier circuit to the power grid. Three-phase rectifiers A1-A4, filter inductors L1, L2, and energy storage capacitors C11-C14 together form two-way voltage sources, which supply power to the pre-stage step-down chopper circuits A5-A8. The pre-stage step-down chopper circuit adopts a Buck Chopper bridge structure, and 4 Buck Choppers are connected in parallel. The output of each Buck Chopper is connected with a passive filter composed of a high-frequency inductor and a filter capacitor to filter out the step-down chopper. output ripple of the circuit. As shown in Figure 4, its output voltage is measured by sensors U7 and U8, and fed back to the voltage closed-loop regulator respectively, thereby suppressing the voltage fluctuation of the power grid and the low-order harmonics generated by the three-phase rectifier on the output voltage of the previous step-down chopper circuit The influence of this ensures that the voltage source supplied to the subsequent step-down chopper circuit is highly stable.

The post-stage step-down chopper circuits A9~A12 also adopt the Buck Chopper bridge structure, 4 Buck Choppers are connected in parallel, and the output end of each Buck Chopper is connected with a passive filter composed of a high-frequency inductor and a filter capacitor to filter out the step-down voltage chopper circuit output ripple. As shown in Figure 4, its output current is measured by sensors U3, U4, U5, and U6, which are respectively fed back to the current-sharing closed-loop regulator. Because the given values of the 4 current-sharing closed-loop regulators all come from the output of the total current closed-loop regulator, the 4 Buck Choppers all output the same magnitude of current, which has good current-sharing characteristics and avoids the natural current-sharing of power devices. The waste of capacity, at the same time, its response is fast and the adjustment accuracy is high. The 4 Buck Choppers in the latter stage use the phase-shift frequency multiplication control technology, and the output frequency is 4 times the operating frequency of the IGBT. This can reduce the output voltage (current) ripple, reduce the burden of passive filtering, and improve the dynamic response performance of power regulation. The total current closed-loop regulation is completed by a current negative feedback closed-loop controller with stable performance, low temperature drift and high precision specially designed for the characteristics of this type of power supply, so that the output current of the power supply has a high degree of stability.

This two-stage Buck Chopper is connected in series and multiple Buck Choppers are connected in parallel. The front stage adopts PID (Proportional-Integral-Differential, proportional-integral-differential operation) closed-loop voltage control, and the latter stage adopts two currents of total current and current sharing. Closed-loop control, multiplier PWM phase-shift control. The function of the front-stage Buck Chopper is to suppress the influence of the power grid voltage fluctuation and the low-order harmonics generated by the three-phase rectifier on the subsequent stage circuit, so as to ensure that the voltage source supplied to the subsequent step-down chopper circuit is highly stable, which is beneficial to reduce output voltage (current) ripple. The duty cycle of the post-stage Buck Chopper is controlled at more than 85% in the whole process, and the synthesized output frequency reaches tens of kilohertz. The long-term stability of the output current of the utility model is ≤±1×10 ^-4 /8 hours, and the output voltage ripple is ≤±1×10 ^-3 .

Fig. 3 shows the schematic circuit diagram of the utility model. It includes incoming line circuit breaker Q, incoming line filters U11, U12, U13, U14, phase-shifting transformers T1, T2, T3, T4, three-phase rectifier bridges A1, A2, A3, A4, filter inductors L1, L2, storage Energy capacitors C11, C12, C13, C14, pre-stage step-down chopper circuits (BuckChopper) A5, A6, A7, A8 (composed of IGBTs and diodes), pre-stage high-frequency inductors L3, L4, L5, L6, pre-stage Filter capacitors C1, C2, C3, C4, voltage sensors U7, U8, post-stage step-down chopper circuits (BuckChopper) A9, A10, A11, A12 (composed of IGBTs and diodes), post-stage high-frequency inductors L7, L8, L9, L10, post-stage filter capacitors C5, C6, C7, C8, current sensors U3, U4, U5, U6, output filter inductors L11, L12, output passive filters C9, C10, R1, current sensor U1 and load Load, control circuit 1.

The connection relationship between them is: the three-phase power supply U, V, W is connected to the line filter U11~U14 through the three-phase circuit breaker Q, and then connected to the primary side of the phase-shifting transformer T1~T4 respectively, and the phase-shifting transformer The secondary sides (with a phase shift of 15° from each other) are respectively connected to the three-phase rectifier bridges A1-A4.

The positive output terminal of A1 is connected to the filter inductor L1, the negative output terminal is connected to the positive output terminal of A2, the negative output terminal of A2 is connected to the negative terminals of energy storage capacitors C11 and C12, the positive terminals of C11 and C12 are connected to the other terminal of the filter inductor L1 connected at one end. Connected in parallel behind the energy storage capacitors C11 and C12 are pre-stage step-down chopper circuits A5 and A6 (composed of IGBTs and diodes). The positive terminal of the output of A5 is connected to the high-frequency inductor L3, the negative terminal of the output is connected to the negative terminal of the filter capacitor C1, and the positive terminal of C1 is connected to the other end of the high-frequency inductor L3. The positive terminal of the output of A6 is connected to the high-frequency inductor L4, the negative terminal of the output is connected to the negative terminal of the filter capacitor C2, and the positive terminal of C2 is connected to the other end of the high-frequency inductor L4. C1 and C2 are connected in parallel, and their two ends are connected with voltage sensor U7, and then connected with subsequent step-down chopper circuits A9 and A10 (composed of IGBT and diode). The positive terminal of the output of A9 is connected to the high-frequency inductor L7, the negative terminal of the output is connected to the negative terminal of the filter capacitor C5, the positive terminal of C5 is connected to the other end of the high-frequency inductor L7, and then the lead-out wire passes through the current sensor U3 to connect to the output filter inductor L11. The positive terminal of the output of A10 is connected to the high-frequency inductor L8, the negative terminal of the output is connected to the negative terminal of the filter capacitor C6, the positive terminal of C6 is connected to the other end of the high-frequency inductor L8, and then the lead wire is passed through the current sensor U4 to connect to the output filter inductor L11.

The same structure as the above circuit, the output positive terminal of A3 is connected to the filter inductor L2, the output negative terminal is connected to the output positive terminal of A4, the output negative terminal of A4 is connected to the negative terminals of energy storage capacitors C13 and C14, and the positive terminals of C13 and C14 The end is connected to the other end of the filter inductor L2. Connected in parallel behind the energy storage capacitors C13 and C14 are pre-stage step-down chopper circuits A7 and A8 (composed of IGBTs and diodes). The positive terminal of the output of A7 is connected to the high-frequency inductor L5, the negative terminal of the output is connected to the negative terminal of the filter capacitor C3, and the positive terminal of C3 is connected to the other end of the high-frequency inductor L5. The positive terminal of the output of A8 is connected to the high-frequency inductor L6, the negative terminal of the output is connected to the negative terminal of the filter capacitor C4, and the positive terminal of C4 is connected to the other end of the high-frequency inductor L6. C3 and C4 are connected in parallel, and their two ends are connected with voltage sensor U8, and then connected with subsequent step-down chopper circuits A11 and A12 (composed of IGBT and diode). The positive terminal of the output of A11 is connected to the high-frequency inductor L9, the negative terminal of the output is connected to the negative terminal of the filter capacitor C7, the positive terminal of C7 is connected to the other end of the high-frequency inductor L9, and then the lead wire is passed through the current sensor U5 to connect to the output filter inductor L12. The positive terminal of the output of A12 is connected to the high-frequency inductor L10, the negative terminal of the output is connected to the negative terminal of the filter capacitor C8, the positive terminal of C8 is connected to the other end of the high-frequency inductor L10, and then the lead wire is passed through the current sensor U6 to connect to the output filter inductor L12.

The outputs of L11 and L12 are connected in parallel to the positive end of capacitor C9, and the negative ends of C5, C6, C7, and C8 are connected in parallel to the negative end of capacitor C9. Capacitor C10 and resistor R1 are connected in series and connected in parallel with C9 to form a passive filter. The positive wire of C9 passes through the current sensor U1 and is connected to the load, and the other end of the load is connected to the negative terminal of C9. The outputs of current sensors U1, U3, U4, U5, U6 and voltage sensors U7, U8 are all connected to control circuit 1, and the output of control circuit 1 is respectively connected to the previous step-down chopper circuit A5, A6, A7, A8 and the subsequent stage The gates of the IGBTs in the step-down chopper circuits A9, A10, A11, A12.

Referring to Fig. 4, the control circuit 1 includes a given current reference 32, a total current closed-loop regulator 2, a current sharing closed-loop regulator 3, 4, 5, 6, an oscillator 7, a frequency division-phase shifting circuit 8, and a pulse forming circuit 9 , 10, 11, 12, proportional device 17, voltage closed-loop regulator 18, 19, triangular wave generating circuit 20, pulse forming circuit 21, 22, subtractor 25, 26, 27, 28, 29, 30, 31.

The connection relationship between them is: the output end of the current reference 32 is respectively connected to the input end of the proportional device 17 and the positive input end of the subtractor 25, the output end of the current sensor U1 is connected to the negative input end of the subtractor 25, The output terminal of the subtractor 25 is connected to the input terminal of the total current closed-loop regulator 2, and the output terminals of the total current closed-loop regulator 2 are respectively connected to the positive input terminals of the subtractors 26, 27, 28, 29, and the current sensors U3, U4, U5 , the output terminals of U6 are respectively connected to the negative input terminals of the subtractors 26, 27, 28 and 29 in turn, and the output terminals of the subtractors 26, 27, 28 and 29 are respectively connected to the current equalizing closed-loop regulators 3, 4, 5, The input end of 6 and the output ends of the current-sharing closed-loop regulators 3, 4, 5, and 6 are respectively connected to one input end of the pulse forming circuits 9, 10, 11, and 12 in turn. The output terminal of the oscillator 7 is connected to the input terminal of the frequency division-phase shifting circuit 8, and the four output terminals of the frequency division-phase shifting circuit 8 are respectively connected to the other input terminals of the pulse forming circuits 9, 10, 11, 12 in turn . The output ends of the pulse forming circuits 9 , 10 , 11 , 12 are respectively connected to the gates of the IGBTs in the step-down chopper circuits A9 , A10 , A11 , A12 of the subsequent stages in turn.

The output terminals of the proportional device 17 are respectively connected to the positive input terminals of the subtractors 30 and 31, the output terminals of the voltage sensors U7 and U8 are respectively connected to the negative input terminals of the subtractors 30 and 31 successively, and the output terminals of the subtractors 30 and 31 are successively They are respectively connected to the input terminals of the voltage closed-loop regulators 18 and 19, and the output terminals of the voltage closed-loop regulators 18 and 19 are respectively connected to one input terminal of the pulse forming circuits 21 and 22 respectively. The output end of the triangular wave generating circuit 20 is respectively connected to the other input end of the pulse forming circuits 21, 22, and the output ends of the pulse forming circuits 21, 22 are respectively connected to the front-stage step-down chopper circuits A5, A6, A7, A8 in turn. The gate of the IGBT.

The working principle of the utility model is: the incoming line filters U11-U14 are used to attenuate the noise interference of the grid and the power supply to each other. The secondary windings of transformers T1~T4 are phase-shifted by 15°. Three-phase rectifiers A1 and A2 are connected in series to form 12-pulse rectification. A 24-pulse rectifier is formed, which will greatly reduce the harmonics of the AC input current on the grid side and improve the power factor, thereby reducing the interference of the rectifier circuit to the power grid. Three-phase rectifiers A1-A4, filter inductors L1, L2, and energy storage capacitors C11-C14 together form two-way voltage sources, which supply power to the pre-stage step-down chopper circuits A5-A8.

The pre-stage step-down chopper circuit adopts a Buck Chopper bridge structure, four Buck Choppers are connected in parallel, and the output of each Buck Chopper is connected with a passive filter composed of a high-frequency inductor and a filter capacitor to filter out the step-down chopper output ripple of the circuit. As shown in Figure 4, its output voltage is controlled by voltage closed-loop regulators 18 and 19. It is through this voltage negative feedback PID closed-loop control that the power grid voltage fluctuation and the low-order harmonics generated by the three-phase rectifier are suppressed. The impact of the voltage chopper circuit ensures that the voltage source supplied to the subsequent step-down chopper circuit is highly stable.

For the subsequent step-down chopper circuit, use the high-precision current sensor U1 to collect the current on the DC output line, send the obtained signal to the total current closed-loop PID regulator, and compare it with the given current reference signal. The output of the total current closed-loop PID regulator is used as the reference signal of the current-sharing closed-loop PI (Proportional-Integral, proportional-integral operation) regulator, and the current signals output by the current sensors U3, U4, U5, and U6 are respectively used as the current-sharing closed-loop PI regulator The feedback signal is compared with the reference signal. The output of the current-sharing closed-loop PI regulator is connected to the pulse forming circuit, which is used as a modulation signal of pulse width modulation, and compared with four triangular waves whose phase shifts are 1/4 period, thereby obtaining four PWM signals, using this four-way PWM The signal is used to control the IGBT in the step-down chopper circuit of the subsequent stage to perform chopping. The duty cycle of the four PWM signals is controlled above 85% in the whole process, and the synthesized output frequency reaches tens of kilohertz.

The phase shift of the four PWM signals generated by the above method is 1/4 cycle. If the frequency of each PWM signal is 10kHz, the switching frequency obtained by superimposing the positive terminal of C9 in Figure 3 is 40kHz. This method is called Phase-shift frequency multiplication control technology. Because the phase shift of the four PWM signals is 1/4 cycle, and the frequency is quadrupled at the superposition point, this increases the number of output voltage pulses, reduces the output voltage (current) ripple, and speeds up the regulation of the power supply. responding speed. Because of the application of frequency doubling technology, the operating frequency of the passive filter has been greatly increased (for example, from 10kHz per channel to 40kHz at the output). According to the knowledge of electromagnetism, this not only reduces the capacity of the passive filter, but also reduces its volume.

Simultaneously, the utility model measures the output currents of the four post-stage step-down chopper circuits by the sensors U3, U4, U5, and U6, and feeds them back to the current-sharing closed-loop regulators respectively. Because the given values of the four current-sharing closed-loop regulators all come from the output of the total current closed-loop regulator, the four Buck Choppers all output the same magnitude of current and have good current-sharing characteristics, which is conducive to giving full play to each Buck The output capability of the Chopper bridge avoids the waste of power device capacity during natural current sharing, reduces procurement costs, and at the same time has fast response and high adjustment accuracy. For power supply devices with high power, the switching on and off of the IGBT will generate strong radiation interference and conduction interference, which puts forward strict requirements for the electromagnetic compatibility design of the system. In the structural design of the device, the utility model makes the energy storage capacitors and IGBTs of the main power circuit all crimped under the laminated copper busbar, and the incoming and outgoing busbars are also laminated, thereby effectively reducing the line complexity. The scattered inductance weakens the skin effect and proximity effect of high-frequency current, and reduces the conduction interference and radiation interference.

The working principle of the control circuit is:

At first, the signal of current given reference 32 is sent into proportional device 17, and the output signal of proportional device 17 is sent into subtractor 30,31 respectively, compares with the signal of voltage sensor U7, U8 output, obtains an error signal, the The error signal is amplified by the voltage closed-loop regulators 18 and 19, and then sent to the pulse forming circuits 21 and 22 for comparison with the output signal of the triangular wave generating circuit 20 to form a PWM signal, which is connected to the previous step-down chopper circuit A5 , A6, A7, and the gates of the IGBTs in A8 drive the front-stage step-down chopper circuit to work.

Oscillator 7 generates a high-frequency clock signal, which is processed by frequency division-phase shift circuit 8 into four triangular waves with phase shifts of 1/4 cycle. The signal of the current given reference 32 is sent to the subtractor 25, and compared with the signal output by the current sensor U1 to obtain an error signal, the error signal is amplified by the total current closed-loop regulator 2, and then sent to the subtractor 26, 27 respectively , 28, 29, compared with the signals output by the current sensors U3, U4, U5, and U6, four error signals are obtained, and the four error signals are respectively amplified by current-sharing closed-loop regulators 3, 4, 5, and 6, and then respectively into the pulse forming circuit 9, 10, 11, 12,. Compared with the aforementioned four triangular waves whose phase shifts are 1/4 period each other, a PWM signal is formed, and the PWM signal is connected to the gates of the IGBTs in the step-down chopper circuits A9, A10, A11, and A12 of the subsequent stage to drive the previous stage Buck chopper circuit works.

When the DC output current increases due to an increase in input voltage or a decrease in load impedance, the output of the total current closed-loop regulator decreases, and the output of the current-sharing closed-loop regulator also decreases, and the pulse width of the PWM signal decreases to make the output voltage Decrease, the output current decreases, so as to keep the current feedback signal equal to the current given reference signal. This negative feedback control also works when the output current drops due to a drop in input voltage or an increase in load impedance. At this time, the output of the total current closed-loop regulator increases, and the output of the current-sharing closed-loop regulator also increases. The increase of the pulse width of the PWM signal increases the output voltage and the output current, thereby keeping the current feedback signal equal to the current given reference Signal. The total current closed-loop regulation is completed by a current negative feedback closed-loop controller with stable performance, low temperature drift and high precision specially designed for the characteristics of this type of power supply, so that the output current of the power supply has a high degree of stability.

The utility model can adopt water cooling or forced air cooling. Its notable advantages are: high long-term stability of output current, low voltage (current) ripple, fast response, and high adjustment accuracy. The device has small volume, high efficiency and low noise.

Claims (10)

1, a kind of direct current steady current power supply that realizes high precision, low ripple with IGBT series-parallel hybrid, it is characterized in that, described power supply comprises: Incoming line filter circuit to attenuate the noise interference between the power grid and the power supply; A phase shifting circuit for generating a phase shift of 15° from the electrical signal processed by the incoming filter circuit; An input rectifying and filtering circuit for rectifying and filtering the phase-shifted electrical signal; An energy storage circuit for forming two voltage sources; The pre-stage step-down chopper circuit powered by the energy storage circuit; A front passive filter circuit used to suppress the output ripple of the previous step-down chopper circuit; The rear step-down chopper circuit powered by the front passive filter circuit; A post-passive filter circuit used to suppress the output ripple of the post-stage step-down chopper circuit; A passive filter circuit at the output to suppress the total output ripple; A voltage sensor circuit used to sample the output voltage of the previous-stage step-down chopper circuit and feed it back to the previous-stage step-down chopper circuit; A current sensor circuit used to sample the output current of the subsequent step-down chopper circuit and feed it back to the subsequent step-down chopper circuit; A current sensor circuit used to sample the total output current and feed it back to the subsequent step-down chopper circuit; A control circuit used to control the operation of the overall circuit. 2. According to claim 1, using IGBT series-parallel hybrid to realize high-precision, low-ripple DC steady-current power supply, it is characterized in that the incoming line filter circuit is composed of filters connected to each grid line respectively composition. 3. The high-precision, low-ripple DC steady-current power supply realized by IGBT series-parallel hybrid according to claim 1, characterized in that, the rectification and filtering circuit at the input end includes a three-phase rectification bridge and a filter inductor. 4. According to claim 3, the high-precision, low-ripple DC steady-current power supply is realized by IGBT series-parallel hybrid, wherein the three-phase rectifier bridge includes A1, A2, A3, and A4 rectifier bridges, wherein A1 and A2 are connected in series, and A3 and A4 are connected in series to form a 12-pulse rectifier respectively. From the grid side, these two 12-pulse rectifiers form a 24-pulse rectifier. 5. According to claim 1, the high-precision, low-ripple DC steady-current power supply is realized by using IGBT series-parallel hybrid, characterized in that, the step-down chopper circuit of the front stage adopts a step-down chopper circuit bridge structure , at least two step-down chopper circuits are connected in parallel, and the output end of each step-down chopper circuit is connected to the front passive filter circuit. 6. The high-precision, low-ripple DC steady-current power supply realized by IGBT series-parallel mixing according to claim 1, characterized in that the front passive filter circuit is composed of a high-frequency inductor and a filter capacitor. 7. According to claim 1, the high-precision, low-ripple DC steady-current power supply is realized by using IGBT series-parallel hybrid, characterized in that, the step-down chopper circuit of the rear stage adopts a step-down chopper circuit bridge structure , at least two step-down chopper circuits are connected in parallel, and the output end of each step-down chopper circuit is connected to the rear passive filter circuit. 8. The high-precision, low-ripple DC steady-current power supply realized by IGBT series-parallel hybrid according to claim 1, characterized in that a current sensor is provided at the output end of the rear passive filter circuit. 9. The high-precision, low-ripple DC steady-current power supply realized by IGBT series-parallel hybrid according to claim 1, characterized in that the input end of the control circuit is connected with the output of the current sensor and the voltage sensor, and the control The output of the circuit is respectively connected to the gates of the IGBT in the previous step-down chopper circuit and the rear-stage step-down chopper circuit. 10. According to claim 1 or 9, the high-precision, low-ripple direct current steady-current power supply is realized by IGBT series-parallel hybrid, characterized in that the control circuit includes a current given reference (32), and the total current closed-loop Regulator (2), current sharing closed-loop regulator (3), (4), (5), (6), oscillator (7), frequency division-phase shifting circuit (8), pulse forming circuit (9), (10), (11), (12), proportional device (17), voltage closed-loop regulator (18), (19), triangular wave generating circuit (20), pulse forming circuit (21), (22), subtractor (25), (26), (27), (28), (29), (30), (31).

Images