CN-122026739-A - Pulse control method and device for three-level converter

CN122026739ACN 122026739 ACN122026739 ACN 122026739ACN-122026739-A

Abstract

The invention provides a pulse control method and device of a three-level converter, wherein the method comprises the steps of obtaining a state signal and a power grid voltage polarity signal of an alternating current output relay after the three-level converter enters a standby working condition, selectively keeping at least one switching tube corresponding to the power grid voltage polarity in a bridge arm in a conducting state according to the power grid voltage polarity signal so as to limit a current switching path between P-O levels or between N-O levels, avoiding overvoltage of the switching tube, and blocking pulses of all the switching tubes in the bridge arm to finish shutdown when detecting that a feedback signal of the alternating current output relay is at a low level, wherein the standby working condition is a working condition that the alternating current output relay is closed and a pulse enabling signal is at a low level. The invention aims to limit the current-exchanging flow path between P-O or N-O through polarity association maintaining conduction, and realize overvoltage protection without increasing hardware cost by taking relay feedback as a blocking condition.

Inventors

SHANG JING
LIU FEI
XIE SHUNMENG
MEI WENQING
XIA JING
ZHANG HONGHAO
ZHU JIAZHI
Du Chengji
YU SHUKUN
SHEN SAIPU

Assignees

株洲中车时代电气股份有限公司

Dates

Publication Date: 20260512
Application Date: 20260409

Claims (10)

1. A pulse control method of a three-level converter, the three-level converter including at least one leg, each leg including a plurality of switching tubes, the method comprising: When the three-level converter enters a standby working condition, acquiring a state signal of an alternating current output relay and a power grid voltage polarity signal; Selectively maintaining at least one switching tube corresponding to the voltage polarity of the power grid in the bridge arm in a conducting state according to the voltage polarity signal of the power grid so as to limit the current commutation path to be limited Between levels or between levels Between the levels, the overvoltage of a switching tube is avoided; When detecting that the feedback signal of the alternating current output relay is at a low level, blocking the pulses of all switching tubes in the bridge arm to finish shutdown; The standby working condition is a working condition that the alternating current output relay is closed and the pulse enabling signal is of low level.
2. The pulse control method of the three-level converter according to claim 1, wherein the selectively maintaining at least one switching tube corresponding to the polarity of the grid voltage in the bridge arm in a conductive state according to the polarity signal of the grid voltage specifically comprises: when the voltage of the power grid is positive, keeping the sixth clamping tube in a conducting state; When the power grid voltage is negative, the fifth clamping tube is kept in a conducting state; when the voltage of the power grid is zero crossing, the fifth clamping tube and the sixth clamping tube are conducted simultaneously within a specified duration, and at least one clamping tube is in a conducting state at any moment.
3. The pulse control method of the three-level converter according to claim 1, wherein the selectively maintaining at least one switching tube corresponding to the polarity of the grid voltage in the bridge arm in a conductive state according to the polarity signal of the grid voltage specifically comprises: When the voltage of the power grid is positive, keeping the second inner pipe in a conducting state; when the power grid voltage is negative, keeping the third inner pipe in a conducting state; When the voltage of the power grid is zero-crossing, the second inner tube and the third inner tube are conducted simultaneously within a specified duration, and at least one inner tube is in a conducting state at any moment.
4. A pulse control method of a three-level converter according to claim 2 or 3, wherein the specified duration is 1 microsecond to 2 microseconds.
5. The method of claim 1, further comprising, in a standby mode, if the pulse enable signal is detected to be restored to a high level, exiting the standby mode at a normal timing of a corresponding modulation mode of the converter, and restoring pulse output.
6. The pulse control method of the three-level converter according to any one of claims 1 to 3, wherein the three-level converter is an active neutral point clamped three-level converter, and each bridge arm comprises a first outer pipe, a fourth outer pipe, a second inner pipe, a third inner pipe, a fifth clamping pipe and a sixth clamping pipe.
7. The pulse control method of a three-level converter according to claim 6, wherein the method is applicable to an inside-fast-outside-slow modulation mode and an inside-slow-outside-fast modulation mode of an active neutral point clamped three-level converter.
8. The pulse control method of the three-level converter according to any one of claims 1 to 3, wherein blocking pulses of all switching tubes in the bridge arm comprises blocking an outer tube first, and blocking an inner tube and a clamping tube second.
9. An inverter control device comprising a processor and a memory, wherein the memory is used for storing an inverter control program, and the processor is used for executing the inverter control program to execute the pulse control method of the three-level converter according to any one of claims 1-8.
10. A readable storage medium storing an inverter control program, wherein the inverter control program when executed implements the pulse control method of the three-level converter according to any one of claims 1 to 8.

Description

Pulse control method and device for three-level converter Technical Field The invention relates to the technical field of power electronics, in particular to a pulse control method and device of a three-level converter. Background The three-level Active Neutral Point Clamped (ANPC) converter has the advantages of high output waveform quality, low switching loss, small voltage stress and the like, and is widely applied to the fields of new energy power generation, energy storage systems, industrial driving and the like. A typical ANPC three-level topological structure is shown in FIG. 1, each bridge arm comprises four switching tubes (T1-T4) and two clamping tubes (T5, T6) which are connected in series, wherein T1 and T4 are outer tubes, T2 and T3 are inner tubes, and T5 and T6 are clamping tubes for realizing a neutral point clamping function. In practical engineering application, the voltage balance problem of the switching tube needs to be considered in the normal operation and shutdown processes of the converter. In the prior art, various control strategies have been used to improve the voltage stress of an ANPC converter during switching. For example, chinese patent application CN101588124a discloses a method for controlling the wave-by-wave current limiting of a diode neutral point clamped multilevel converter, which includes closing the outer tube first and then closing the inner tube when protecting, and conducting the two inner tubes at the same time when recovering pulse, so as to avoid the inner tube overvoltage during the pulse blocking and recovering process. The Chinese patent application with publication number of CN119813111A proposes a protection method of an ANPC type three-level inverter, which aims at the current limiting protection of the high-frequency modulation of the inner tube and the shutdown process, and avoids the inner tube overvoltage in the shutdown process by firstly switching on the inner tube and then switching off the clamping tube. For another example, chinese patent application CN102868291a discloses a current limiting control method of a diode neutral point clamped three-level inverter and a related circuit, and the method avoids overvoltage of the outer tube by opening two inner tubes in sequence when pulse recovery occurs. As described above, the prior art mainly solves the problem of unbalanced voltage of the converter at the moment of blocking or recovering the pulse by adjusting the turn-off and recovery time sequence of the pulse. However, the voltage stress problem under the standby working condition is not considered in the prior art. The standby mode refers to a state in which the ac output relay remains closed but the converter is not pulsed. As shown in fig. 1, when the inverter is in standby mode, the output level can only be switched between P and N due to all pulses being blocked. When the current is back-flushed or the network voltage suddenly fluctuates after the current is zeroed, the current flows along a path shown in the figure to form a P-N straight-through loop. The current-exchanging path causes two corresponding series diodes of the inner tube and the outer tube to simultaneously recover reversely and bear the full bus voltage. Because of the difference of the chips or peripheral circuits used by the inner tube and the outer tube, the partial pressure capacity is inconsistent, so that the partial pressure of the inner tube and the outer tube is uneven, and the single tube overvoltage fault is caused. Therefore, how to effectively avoid the problem of single-tube overvoltage caused by current natural commutation or network voltage fluctuation under the standby working condition becomes a technical problem to be solved in the field. Disclosure of Invention The invention aims to solve the technical problems in the prior art, and provides a pulse control method and a pulse control device for a three-level converter, which aim to selectively keep the conduction of an inner tube or a clamping tube according to the polarity of network voltage under a standby working condition and control pulse blocking time by combining a relay feedback, so that a P-N straight-through path caused by natural current conversion or network voltage fluctuation is avoided, and single-tube overvoltage faults caused by uneven voltage division of the inner tube and the outer tube are fundamentally prevented. In order to solve the technical problems, the technical scheme provided by the invention is as follows: A pulse control method of a three-level converter, the three-level converter including at least one leg, each leg including a plurality of switching tubes, the method comprising: When the three-level converter enters a standby working condition, acquiring a state signal of an alternating current output relay and a power grid voltage polarity signal; Selectively maintaining at least one switching tube corresponding to the voltage polarity of the power grid in the bridge ar