CN118232718A - IGBT parallel current equalizing circuit, PWM rectifier and PWM inverter - Google Patents
IGBT parallel current equalizing circuit, PWM rectifier and PWM inverter Download PDFInfo
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- CN118232718A CN118232718A CN202410340997.9A CN202410340997A CN118232718A CN 118232718 A CN118232718 A CN 118232718A CN 202410340997 A CN202410340997 A CN 202410340997A CN 118232718 A CN118232718 A CN 118232718A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/02—Conversion of AC power input into DC power output without possibility of reversal
- H02M7/04—Conversion of AC power input into DC power output without possibility of reversal by static converters
- H02M7/12—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of AC power input into DC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of AC power input into DC power output; Conversion of DC power input into AC power output
- H02M7/42—Conversion of DC power input into AC power output without possibility of reversal
- H02M7/44—Conversion of DC power input into AC power output without possibility of reversal by static converters
- H02M7/48—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of DC power input into AC power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
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Abstract
The invention discloses an IGBT parallel current-sharing circuit, a PWM rectifier and a PWM inverter, which comprises N parallel branches, N full-coupling inductors and an LCL filter circuit, wherein the middle point of a bridge arm of each parallel branch is connected to the same name end of the primary side of the full-coupling inductor corresponding to the parallel branch, the non-same name ends of the primary sides of the N full-coupling inductors are commonly connected to be used as a converging end, the secondary sides of the N full-coupling inductors are divided into one or more groups, and each group is connected into a ring in an end-to-end mode; and after the leakage inductance of all the full-coupling inductors are connected in parallel, the leakage inductance of all the full-coupling inductors and the back LCL filter circuit are equivalent to form a new LCL filter circuit, so that the switching harmonic wave is suppressed, and the switching harmonic wave which is converged into a power grid or an alternating current load is reduced.
Description
Technical Field
The invention relates to the field of PWM rectifiers, in particular to an IGBT parallel current sharing circuit, a PWM rectifier and a PWM inverter.
Background
The PWM rectifier or PWM inverter comprises a plurality of IGBT parallel branches, the output ends of the branches are connected together, and when the parallel branches are connected in parallel, the amplitude or phase of the voltage of each parallel branch is inconsistent due to the performance difference of each parallel branch, the circuit parameter dispersion, the disturbance rejection capability and other factors, so that the problems of uneven flow and loop current exist among the parallel branches. The current equalizing method of the parallel branch of the IGBT mainly comprises the following steps:
1) Optimizing layout method: and the current sharing is realized through the symmetrical design of IGBT parallel branches. The symmetry of the parallel branches is maintained by optimizing the layout and routing of the IGBT parallel branches, the problem of uneven flow caused by inconsistent routing and layout can be reduced, but the IGBT is used as a non-ideal switching device, the current sharing characteristic of the IGBT is influenced by the opening threshold voltage, the saturation voltage drop of the device, the junction temperature of the device and the like, meanwhile, the magnetic fields among the parallel branches can influence each other, the influence of a plurality of related factors on the current sharing of the parallel branches of the IGBT is ensured, the debugging and optimizing process is complex, the time cost is high, and the consistency of the device is not completely ensured.
2) Series resistance method: and the resistances are connected in series in parallel branches of the IGBT to balance uneven current caused by the conduction voltage drop of the IGBT. The voltage drop of the parallel branch of the IGBT is regulated by a series resistor, the device is required to be subjected to saturation voltage drop test, the voltage drop difference of the parallel IGBT under the required current is calculated, then the resistance value is calculated reversely, the voltage drop difference of the parallel branch is compensated by regulating the size of the series resistor to realize static current sharing, however, the current sharing effect of the series resistor is poor in the dynamic process of the switching transient state of the IGBT, the series resistor is applied under high current, the resistance value of the series resistor generally needs to be customized, the resistance value of the matched series resistor also changes within a certain range when the IGBTs of different batches are connected in parallel, the batch consistency is not easy to control, and the scheme can bring additional loss and the rise of the system cost.
3) Active driving method: by detecting the current of the parallel IGBTs, the IGBTs are driven in a variable delay mode, the switching-on and switching-off processes of the IGBTs are regulated separately, and the IGBTs are forced to realize current sharing. According to the scheme, dynamic unevenness of the IGBT can be optimized, static current sharing is realized by means of screening consistency of device conduction voltage drop, but due to the fact that detection and control software is added, real-time requirements on a controller are very high, a separate driving circuit can realize variable-delay or multi-level driving, complexity of the driving circuit is increased, reliability is not guaranteed, and cost of a system is increased proportionally.
4) Serial differential mode coupling inductance method: the method is characterized in that differential mode coupling inductors are connected in series in a parallel path of the IGBTs, static current sharing and dynamic current sharing of the IGBT devices are carried out in a magnetic field coupling mode, and the defect that the inductance of the differential mode coupling inductors is superposed on stray inductances of the IGBT devices due to the fact that the differential mode coupling inductors are connected in series between a bus and the IGBT switching devices, so that the problem that the stress of the IGBT devices is too high easily occurs in the turn-off process is solved, leakage inductance introduced by the differential mode inductors is not too large in design, and otherwise the reliability of the devices is reduced.
Disclosure of Invention
The technical problem to be solved by the invention is to provide an IGBT parallel current sharing circuit, a PWM rectifier and a PWM inverter aiming at the defects in the prior art.
The technical scheme adopted for solving the technical problems is as follows: an IGBT parallel current sharing circuit is constructed for a PWM rectifier or PWM inverter, comprising:
N parallel branches, wherein each parallel branch is connected between a positive direct current bus and a negative direct current bus and is formed by connecting an IGBT upper bridge arm and an IGBT lower bridge arm in series, the connecting point of the IGBT upper bridge arm and the IGBT lower bridge arm in each parallel branch is a bridge arm midpoint, and N is a positive integer greater than 1;
The N full-coupling inductors are in one-to-one correspondence with the N parallel branches, the middle point of a bridge arm of each parallel branch is connected to the same-name end of the primary side of the full-coupling inductor corresponding to the parallel branch, the non-same-name ends of the primary sides of the N full-coupling inductors are commonly connected to be used as a converging end, the secondary sides of the N full-coupling inductors are divided into one or more groups, and each group is connected into a ring in an end-to-end mode;
and the LCL filter circuit is connected between the bus ends of the N full-coupling inductors and an alternating current object and is used for inhibiting switching harmonic waves entering the alternating current object, wherein the alternating current object is an alternating current source or an alternating current load.
Further, in the IGBT parallel current sharing circuit of the present invention, the LCL filter circuit includes a first filter inductor, a first filter capacitor, and a second filter inductor, where a first end of the first filter inductor is connected to a bus end of the N full-coupling inductors, a second end of the first filter inductor is grounded through the first filter capacitor, and a second end of the first filter inductor is also connected to an ac source or an ac load through the second filter inductor;
the windings of the full-coupling inductor are wound around the magnetic core in parallel and tightly, and the inductance of the full-coupling inductor is greater than or equal to N times of the inductance of the first filter inductor.
Further, in the IGBT parallel current sharing circuit, a driving loop is connected between the grid and the emitter of the IGBT of the parallel branch, a power loop is connected between the collector and the emitter of the IGBT, and a driving signal wire between the emitter of the IGBT connected with the driving loop and a power wire between the emitter of the IGBT connected with the power loop are separated;
The IGBT grid is connected into a driving loop through a grid driving resistor and the emitter of the IGBT is connected into the driving loop through an emitter matching resistor so as to inhibit circulation.
Furthermore, in the IGBT parallel current sharing circuit, magnetic beads are connected in series between the emitter of the IGBT and the emitter matching resistor so as to inhibit oscillation signals.
Further, in the IGBT parallel current sharing circuit, the width of the driving pulse of the IGBT of the parallel branch is larger than or equal to 1us.
Further, in the IGBT parallel current sharing circuit, each parallel branch comprises four IGBTs connected in series, the first IGBT and the second IGBT form an IGBT upper bridge arm, the third IGBT and the fourth IGBT form an IGBT lower bridge arm, the connection point of the connection node of the second IGBT and the third IGBT is a bridge arm midpoint, and the same-order IGBTs of all the parallel branches receive the same driving signal.
Further, in the parallel current equalizing circuit of the IGBT, the parallel current equalizing circuit further comprises a first bus capacitor and a second bus capacitor which are connected in series between the positive direct current bus and the negative direct current bus, wherein a connecting node of the first bus capacitor and the second bus capacitor is a bus midpoint, the whole body of the first bus capacitor and the second bus capacitor after being connected in series is connected with the parallel branch, the connecting node of the first IGBT and the second IGBT is an upper bridge arm midpoint, and the connecting node of the third IGBT and the fourth IGBT is a lower bridge arm midpoint;
each upper bridge arm midpoint and each lower bridge arm midpoint are connected with the bus midpoint through corresponding diodes: the middle point of each upper bridge arm is connected to the cathode of the corresponding diode and the middle point of the positive electrode connecting bus of the corresponding diode; each lower bridge arm midpoint is connected to the anode of the corresponding diode and the cathode of the corresponding diode is connected with the bus midpoint.
The IGBT parallel current sharing circuit, the PWM rectifier and the PWM inverter have the following beneficial effects: according to the invention, parallel current sharing of the IGBT is carried out through the full-coupling inductor, a branch with large current can form negative induced voltage in the branch, so that the current of the branch is regulated in a small direction, and electric energy is converted into magnetic energy; the branch circuit with small current can form forward induced voltage in the branch circuit, so that the current of the branch circuit is regulated in a large direction, and magnetic energy is converted into electric energy; the magneto-electric conversion process is synchronously carried out, so that the induced electromotive force always exists as long as the branch current is unbalanced, the branch current is forced to change towards the balanced direction, so that current sharing output is realized, after leakage inductance of all the fully-coupled inductors are connected in parallel, the leakage inductance of all the fully-coupled inductors and a rear LCL filter circuit are equivalent to form a new LCL filter circuit, switching harmonic waves are suppressed, switching harmonic waves which are converged into a power grid or an alternating current load are reduced, the design scheme, the manufacturing process and the circuit realization of the fully-coupled inductors are relatively simple, software logic participation is not needed, current sharing of parallel branches is automatically realized through magneto-electric conversion, and the circuit operation reliability is high and the cost is low;
Furthermore, the invention also considers that the actual coupling inductance is not an ideal device, the coupling coefficient is not 1, and meanwhile, the inductance unsaturation is guaranteed, so that the winding of the full coupling inductance is wound around the magnetic core in parallel and tightly, and the inductance of the full coupling inductance is larger than or equal to N times of the inductance of the first filtering inductance in the LCL filtering circuit; when the coupling inductance is considered to compensate the differential pressure of the branch circuit to realize current sharing control, the differential pressure belongs to a step excitation signal for a driving circuit of the IGBT, so that oscillation is generated by controlling a grid driving signal in the turn-on and turn-off processes of the IGBT, and grid overvoltage and direct-connection risks of an IGBT device are caused. In addition, the width of the driving pulse of the IGBT is larger than or equal to 1us, and the phenomenon that when the grid electrode of the parallel branch is driven by a narrow pulse signal, compensation differential pressure formed by coupling inductance due to the fact that the grid electrode is rapidly turned on and off and the device is turned on and off is inconsistent is avoided, the compensation differential pressure can be simultaneously loaded to the control grid electrode of the IGBT, the oscillation of grid electrode signals of the parallel branch of the IGBT can be aggravated by various rapid jump signals, and the grid electrode overvoltage and the device damage caused by misleading of the IGBT are extremely easy to occur.
Drawings
For a clearer description of an embodiment of the invention or of a technical solution in the prior art, the drawings that are needed in the description of the embodiment or of the prior art will be briefly described, it being obvious that the drawings in the description below are only embodiments of the invention, and that other drawings can be obtained, without inventive effort, by a person skilled in the art from the drawings provided:
FIG. 1 is a schematic diagram of a parallel current sharing circuit of an IGBT;
fig. 2 is a schematic structural diagram of a first embodiment of an IGBT parallel current sharing circuit according to the present invention;
FIG. 3 is a schematic diagram of an equivalent LCL filter circuit;
Fig. 4 is a schematic diagram of a drive signal routing and power routing scheme for the parallel branch of IGBTs;
FIG. 5 is a waveform schematic diagram of parallel-arm current and its difference when co-located parallel devices use the same PWM drive signal;
FIG. 6 is a schematic waveform diagram of parallel arm current and its difference when a co-located parallel device uses a variable delay drive signal;
Fig. 7 is a schematic structural diagram of a second embodiment of the IGBT parallel current sharing circuit of the present invention;
Fig. 8 is a schematic structural diagram of a third embodiment of the IGBT parallel current sharing circuit of the present invention.
Detailed Description
In order that the application may be readily understood, a more complete description of the application will be rendered by reference to the appended drawings. Exemplary embodiments of the present application are illustrated in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical solutions of the present application, and not limited to the technical solutions of the present application, and the embodiments of the present application and the technical features in the embodiments may be combined with each other without conflict.
Referring to fig. 1, the general idea of the present invention is to construct an IGBT parallel current sharing circuit, which includes:
N parallel branches, each parallel branch is connected between a positive direct current bus and a negative direct current bus (DC+ represents the positive direct current bus and DC-represents the negative direct current bus in the figure) and is formed by connecting an IGBT upper bridge arm and an IGBT lower bridge arm in series, the connecting point of the IGBT upper bridge arm and the IGBT lower bridge arm in each parallel branch is a bridge arm midpoint, and N is a positive integer larger than 1; the IGBT upper bridge arm consists of at least one IGBT, and the IGBT lower bridge arm consists of at least one IGBT;
The N full-coupling inductors are in one-to-one correspondence with the N parallel branches, the middle point of a bridge arm of each parallel branch is connected to the same-name end of the primary side of the full-coupling inductor corresponding to the parallel branch, the non-same-name ends of the primary sides of the N full-coupling inductors are commonly connected to be used as a converging end, the secondary sides of the N full-coupling inductors are divided into one or more groups, and each group is connected into a ring in an end-to-end mode; in fig. 1, the secondary sides of the N fully-coupled inductors are shown to be divided into one group, and in practice, the secondary sides of each group may be further divided into more groups, and the number of the secondary sides of each group is not limited and may be equal or unequal.
The LCL filter circuit is connected between the bus ends of the N full-coupling inductors and an alternating current object, and is used for suppressing switching harmonics which enter the alternating current object, wherein the alternating current object is an alternating current source (such as a power grid) or an alternating current load.
Because the current is bi-directional, the circuit can be used in either a PWM rectifier or a PWM inverter, and if used in a PWM rectifier, the LCL filter circuit is connected between the bus and an ac source (such as a power grid), with the positive and negative dc buses connecting the dc loads. If the inverter is a PWM inverter, the positive and negative DC buses are connected with a DC source, and the LCL filter circuit is connected between the bus end and an AC load.
In fig. 1, a branch with a large current will form a negative induced voltage in the branch, so as to promote the current of the branch to be adjusted towards a small direction, and the electric energy is converted into magnetic energy; the branch circuit with small current can form forward induced voltage in the branch circuit, so that the current of the branch circuit is regulated in a large direction, and magnetic energy is converted into electric energy; the magneto-electric conversion process is synchronous, so that the induced electromotive force always exists as long as the branch current is unbalanced, the branch current is forced to change towards the balanced direction, so that current sharing output is realized, after leakage inductance of all the fully-coupled inductors are connected in parallel, the leakage inductance of all the fully-coupled inductors and a rear LCL filter circuit are equivalent to form a new LCL filter circuit, switching harmonic waves are suppressed, switching harmonic waves which are converged into a power grid or an alternating current load are reduced, the design scheme, the manufacturing process and the circuit realization of the fully-coupled inductors are relatively simple, software logic participation is not needed, current sharing of parallel branches is automatically realized through magneto-electric conversion, and the circuit operation reliability is high and the cost is low.
Several specific embodiments are described below.
Example 1
Referring to fig. 1, the present embodiment is for a PMW rectifier. The embodiment comprises 3 parallel branches, 3 full-coupling inductors, an LCL filter circuit, a first bus capacitor C1 and a second bus capacitor C2 which are connected in series between a positive direct current bus and a negative direct current bus.
The connecting node of the first bus capacitor C1 and the second bus capacitor C2 is a bus midpoint, and the whole of the first bus capacitor C1 and the second bus capacitor C2 which are connected in series is connected with 3 parallel branches in parallel. Each parallel branch includes four IGBTs connected in series. The first IGBT and the second IGBT form an IGBT upper bridge arm, and the third IGBT and the fourth IGBT form an IGBT lower bridge arm. The connection point of the connection node of the second IGBT and the third IGBT is the bridge arm midpoint. The connection node of the first IGBT and the second IGBT is the middle point of the upper bridge arm. The connection node of the third IGBT and the fourth IGBT is the midpoint of the lower bridge arm.
In the 3 parallel branches, the middle point of each upper bridge arm and the middle point of each lower bridge arm are connected with the middle point of a bus through corresponding diodes, for example, in fig. 1, the middle points of the upper bridge arms of the 3 parallel branches are respectively connected with the middle points of the buses through diodes D1, D2 and D3, and the middle points of the lower bridge arms of the 3 parallel branches are respectively connected with the middle points of the buses through diodes D4, D5 and D6. More specifically, the middle point of each upper bridge arm is connected to the middle point of a positive connecting bus of the corresponding diode D1/D2/D3 and the corresponding diode D1/D2/D3; each lower bridge arm midpoint is connected to the anode of the corresponding diode D4/D5/D6 and the cathode of the corresponding diode D4/D5/D6.
The middle point of the bridge arm of each parallel branch is connected to the primary side homonymous end of the full-coupling inductor T1/T2/T3 corresponding to the parallel branch, and the primary side non homonymous ends of the 3 full-coupling inductors T1, T2 and T3 are commonly connected to be used as a converging end. The LCL filter circuit comprises a first filter inductor L1, a first filter capacitor C3 and a second filter inductor L2, wherein a first end of the first filter inductor (L1) is connected with a bus end of N full-coupling inductors, a second end of the first filter inductor L1 is grounded through the first filter capacitor C3, and a second end of the first filter inductor L1 is also connected with a power grid through the second filter inductor L2.
In this embodiment, the same-order IGBTs of all parallel branches receive the same driving signal. In fig. 1, IGBT2, IGBT3 are controlled by using driving signals PWM1, IGBT4, IGBT5, IGBT6 are controlled by using PWM2, IGBT7, IGBT8, IGBT9 are controlled by using PWM3, IGBT10, IGBT11, IGBT12 are controlled by using PWM4, the output voltages at the middle points of the bridge arms of the three parallel branches are V1, V2, V3, which are respectively input from the primary homonymous ends of the full-coupled inductors T1, T2, T3, va output is obtained by converging from the primary non-homonymous ends of the full-coupled inductors, the secondary sides of T1, T2, T3 are connected in an end-to-end connection manner, and the secondary sides of T1, T2, T3 are connected in series and are equivalent to the case of secondary side short circuit, so that the three coupled inductors can be equivalent to the three leakage inductances lk_t1, lk_t2, lk_t3 are connected in parallel and then in series with L1 in the whole power loop, are equivalent to the circuit of fig. 3, the leakage inductances lk_t1, lk_t2, lk_t3 are connected in parallel and then in parallel with L2 are connected in parallel, and the new harmonic current is suppressed in the power grid, and the harmonic filter circuit is formed.
The current sharing of the IGBT parallel branch circuit is realized by the circuit according to the embodiment, wherein the current sharing of the IGBT parallel branch circuit is based on the mutual conversion principle of an electric field and a magnetic field of a magnetic device, and a branch circuit with large current can form negative induced voltage in the branch circuit so as to promote the current of the branch circuit to be adjusted towards a small direction, and electric energy is converted into magnetic energy; the branch circuit with small current can form forward induced voltage in the branch circuit, so that the current of the branch circuit is regulated in a large direction, and magnetic energy is converted into electric energy; the magneto-electric conversion process is synchronously carried out, so that the induced electromotive force exists all the time only when the current of the branch is unbalanced, and the current of the branch is forced to change towards the balanced direction, thereby realizing current sharing output.
However, the actual coupling inductance is not an ideal device, the coupling coefficient cannot be 1, meanwhile, the unsaturation of the inductance is guaranteed, the actual coupling inductance is an inductance capable of bearing a certain direct current bias, the inductance is correspondingly attenuated when the current flowing through the inductance increases in a nonlinear manner, and the following requirements are met for the design of the full coupling inductance: on one hand, the windings of the fully-coupled inductor are wound around the magnetic core in parallel and tightly; on the other hand, the inductance of the full-coupling inductor is greater than or equal to N times the inductance of the first filter inductor L1, N being the number of parallel branches.
The drive loop is connected between the grid and the emitter of the IGBT, the power loop is connected between the collector and the emitter of the IGBT, the coupling inductance is used for realizing current sharing control by compensating the differential pressure of the branches, the differential pressure belongs to a step excitation signal for the drive circuit for providing the drive signal for the IGBT, the grid drive signal can be caused to oscillate in the turn-on and turn-off processes of the IGBT, and the grid overvoltage and the through risk of the IGBT device are caused, so that in the invention, the grid of the IGBT is connected into the drive loop through the grid drive resistor and the emitter of the IGBT through the emitter matching resistor to inhibit circulation, that is, the emitter of the IGBT is connected to one output end of the drive circuit through the emitter matching resistor, the grid of the IGBT is connected to the other output end of the drive circuit through the grid drive resistor, and the drive signal wiring between the emitter of the IGBT and the power wiring between the emitter connection drive loops of the IGBT are separated, as shown in fig. 4, the thin solid lines represent the signal wiring, the thick solid lines represent the power wiring, only the first IGBT of 3 branches are shown in fig. 4, and R1, R2 and R3 are the grid drive resistors of the IGBT1, IGBT2 and IGBT3 are the grid drive resistors of the IGBT. Further, magnetic beads are further connected in series between the emitter of the IGBT and the emitter matching resistor to suppress oscillation signals, for example, FB1, FB2, FB3 are magnetic beads connected to the emitters of IGBT1, IGBT2, IGBT3 in the figure, and more specifically, the magnetic beads are located between the emitter matching resistor and the emitter of the IGBT, that is, the magnetic beads are closer to the emitter than the emitter matching resistor.
Further, the width of the driving pulse of the IGBT is larger than or equal to 1us, and the phenomenon that when the grid electrode of the parallel branch is driven by a narrow pulse signal, compensation differential pressure formed by coupling inductance due to the fact that the grid electrode is rapidly turned on and off and the device is turned on and off is inconsistent is avoided, the control grid electrode of the IGBT can be loaded at the same time, the oscillation of grid electrode signals of the parallel branch of the IGBT can be aggravated by various rapid jump signals, and the damage to the device caused by grid electrode overvoltage and misleading of the IGBT is extremely easy to occur.
Referring to fig. 5, waveforms of parallel branch current and its difference when the same PWM driving signal is used by the same parallel devices are shown. Simulation conditions: the difference of IGBT saturation voltage drops of the branch 1 and the branch 2 is 0.15V, and the difference of IGBT saturation voltage drops of the branch 1 and the branch 3 is 0.3V; the same PWM drive signal is used by the same co-located parallel devices. I1, I2 and I3 respectively represent the currents of three branches, and I1-I2, I1-I3 and I2-I3 represent the current difference value between any two branches. The graph shows that the larger the IGBT saturation voltage drop difference is, the larger the current difference value of the branch is, the maximum value of the current difference value is 5A, the maximum value of the branch current is 120A, the current sharing error percentage is less than or equal to 5%, and the requirement of parallel connection reliability is met.
Referring to fig. 6, waveforms of parallel branch current and its difference when the same parallel device uses a variable delay driving signal are shown. Simulation conditions: the difference of IGBT saturation voltage drops of the branch 1 and the branch 2 is 0.15V, and the difference of IGBT saturation voltage drops of the branch 1 and the branch 3 is 0.3V; the parallel devices at the same position use driving signals with variable delay, and IGBTs of three parallel branches are respectively delayed by 0s, 200ns and 100ns. The graph shows that the larger the IGBT saturation voltage drop difference is, the larger the current difference value of the branch is, the maximum value of the current difference value is 6A, the maximum value of the branch current is 120A, the current sharing error percentage is less than or equal to 5%, and the requirement of parallel connection reliability is met.
It can be understood that the number of parallel branches is not limited to the three-parallel circuit of the embodiment, and more parallel branches can be reasonably divided into groups according to the circuit topology of fig. 2, so as to achieve the purpose of parallel current sharing.
Therefore, the parallel current sharing of the IGBT is carried out through the full-coupling inductor, the design scheme, the manufacturing process and the circuit implementation of the full-coupling inductor are simpler, software logic participation is not needed, and the current sharing of the parallel branch circuit is automatically realized through magneto-electric conversion, so that the cost is low and the reliability is high.
Example two
Referring to fig. 7, in this embodiment, the number of parallel branches is two, and correspondingly, the number of full-coupling inductors is two, V1 and V2 are output voltages at the midpoints of bridge arms of the two parallel branches, and Va represents an output voltage at the bus terminal.
Example III
Referring to fig. 8, in this embodiment, the number of parallel branches is 4, and correspondingly, the number of full-coupling inductors is also 4, and V1, V2, V3, and V4 are output voltages at midpoints of bridge arms of the 4 parallel branches, where Va represents an output voltage at a bus terminal. In addition, in this embodiment, the secondary sides of the 4 full-coupling inductors are in a group, and the combination is connected end to end, and of course, the secondary sides of the 4 full-coupling inductors may be all divided into a group to end.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The terms including ordinal numbers such as "first", "second", and the like used in the present specification may be used to describe various constituent elements, but these constituent elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a first component may be termed a second component, and, similarly, a second component may be termed a first component, without departing from the scope of the present invention. The term "coupled" or "connected" includes not only the direct connection of two entities but also the indirect connection through other entities having beneficial improvements.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.
Claims (9)
1. An IGBT parallel current sharing circuit for a PWM rectifier or PWM inverter, comprising:
N parallel branches, wherein each parallel branch is connected between a positive direct current bus and a negative direct current bus and is formed by connecting an IGBT upper bridge arm and an IGBT lower bridge arm in series, the connecting point of the IGBT upper bridge arm and the IGBT lower bridge arm in each parallel branch is a bridge arm midpoint, and N is a positive integer greater than 1;
The N full-coupling inductors are in one-to-one correspondence with the N parallel branches, the middle point of a bridge arm of each parallel branch is connected to the same-name end of the primary side of the full-coupling inductor corresponding to the parallel branch, the non-same-name ends of the primary sides of the N full-coupling inductors are commonly connected to be used as a converging end, the secondary sides of the N full-coupling inductors are divided into one or more groups, and each group is connected into a ring in an end-to-end mode;
and the LCL filter circuit is connected between the bus ends of the N full-coupling inductors and an alternating current object and is used for inhibiting switching harmonic waves entering the alternating current object, wherein the alternating current object is an alternating current source or an alternating current load.
2. The IGBT parallel current sharing circuit according to claim 1, wherein the LCL filter circuit includes a first filter inductor, a first filter capacitor, a second filter inductor, a first end of the first filter inductor is connected to a bus end of the N full-coupling inductors, a second end of the first filter inductor is grounded via the first filter capacitor, and a second end of the first filter inductor is also connected to an ac source or an ac load via the second filter inductor;
The windings of the full-coupling inductor are wound around the magnetic core in parallel and tightly, and the inductance of the full-coupling inductor is greater than or equal to N times of the inductance of the first filter inductor (L1).
3. The IGBT parallel current sharing circuit according to claim 1, wherein a drive loop is connected between the gate and the emitter of the IGBT of the parallel branch, a power loop is connected between the collector and the emitter of the IGBT, and a drive signal trace between the emitter-connected drive loop of the IGBT and a power trace between the emitter-connected power loop of the IGBT are separated;
The IGBT grid is connected into a driving loop through a grid driving resistor and the emitter of the IGBT is connected into the driving loop through an emitter matching resistor so as to inhibit circulation.
4. The IGBT parallel current sharing circuit according to claim 3, wherein a magnetic bead is further connected in series between the emitter of the IGBT and the emitter matching resistor to suppress the oscillation signal.
5. The IGBT parallel current sharing circuit of claim 1 wherein the width of the drive pulse of the parallel-branched IGBTs is greater than or equal to 1us.
6. The IGBT parallel current sharing circuit according to claim 1, wherein each parallel branch includes four IGBTs connected in series, the first IGBT and the second IGBT constitute an IGBT upper arm, the third IGBT and the fourth IGBT constitute an IGBT lower arm, a connection point of a connection node of the second IGBT and the third IGBT is a bridge arm midpoint, and the same-order IGBTs of all parallel branches receive the same driving signal.
7. The IGBT parallel current sharing circuit according to claim 6, further comprising a first bus capacitor and a second bus capacitor connected in series between the positive and negative dc buses, a connection node of the first bus capacitor and the second bus capacitor being a bus midpoint, the entirety of the first bus capacitor and the second bus capacitor connected in series being connected in parallel with the parallel branch, a connection node of the first IGBT and the second IGBT being an upper bridge arm midpoint, a connection node of the third IGBT and the fourth IGBT being a lower bridge arm midpoint;
each upper bridge arm midpoint and each lower bridge arm midpoint are connected with the bus midpoint through corresponding diodes: the middle point of each upper bridge arm is connected to the cathode of the corresponding diode and the middle point of the positive electrode connecting bus of the corresponding diode; each lower bridge arm midpoint is connected to the anode of the corresponding diode and the cathode of the corresponding diode is connected with the bus midpoint.
8. A PWM rectifier comprising a parallel current sharing circuit as claimed in any one of claims 1 to 7.
9. A PWM inverter comprising a parallel current sharing circuit as claimed in any one of claims 1 to 7.
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| CN202410340997.9A CN118232718A (en) | 2024-03-25 | 2024-03-25 | IGBT parallel current equalizing circuit, PWM rectifier and PWM inverter |
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| CN202410340997.9A CN118232718A (en) | 2024-03-25 | 2024-03-25 | IGBT parallel current equalizing circuit, PWM rectifier and PWM inverter |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118589895A (en) * | 2024-08-06 | 2024-09-03 | 西安奇点能源股份有限公司 | Connecting circuit for enhancing topological symmetry of I-type NPC IGBT parallel connection |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118589895A (en) * | 2024-08-06 | 2024-09-03 | 西安奇点能源股份有限公司 | Connecting circuit for enhancing topological symmetry of I-type NPC IGBT parallel connection |
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