Control method and system for starting of multi-level bidirectional DC-DC converter

Abstract

The invention discloses a control method and system for starting of a multi-level bidirectional DC-DC converter, belonging to the field of DC-DC conversion. The method comprises the steps that when a high-voltage side is started, switching tubes including S<N>, S<N+1>, S<3N> and S<3N+1> are disconnected, the other switching tubes are switched on, k is gradually reduced from N-1 to 1, and switching tubes connected with the high-voltage side are disconnected when the voltage of C<2k+1> or C<2k+2> reaches a corresponding set value; when a low-voltage side is started, S<N+1> and S<3N> are disconnected, the other switching tubes are switched on, k is gradually decreased from N-1, S<2N-k+1> and S<2N+k> are disconnected when the voltage of C<2k+1> or C<2k+2> reaches a corresponding set value, and until the voltage of C<2k+1> or C<2k+2> reaches 1 / 2 of the voltage of the low-voltage side, switching tubes from S<k+1> to SN, from S<N+1> to S<2N-k>, from S<2N+k+1> to S<3N> and from S<3N+1> to S<4N-k> are divided into four groups and subjected to PWM modulation; and then, k continues to be gradually decreased to 1, and when the voltage of C<2k+1> or C<2k+2> reaches the corresponding set value, the connected switching tubes are added to the four groups of switching tubes. When the multi-level bidirectional DC-DC converter is started, the voltage of a flying capacitor is controlled, the voltage stress balance of the switching tubes is kept, faults are avoided, and the converter can be safely started on both sides.

Description

technical field [0001] The invention belongs to the field of DC-DC conversion, and more specifically relates to a method and system for starting and controlling a multi-level bidirectional DC-DC converter. Background technique [0002] A bidirectional DC / DC converter is a circuit that converts a DC power supply, and its input and output voltages are both DC. Because of its many advantages, multilevel converters are gradually favored by people. Multilevel converters include diode-clamped multilevel converters, cell cascaded multilevel converters, and flying capacitor multilevel converters. Among them, the number of switching devices in the flying capacitor multilevel converter is small, and it is easy to expand to a higher level converter. However, in the application of the flying capacitor type multilevel converter, the voltage balance of the flying capacitor must be ensured, so that the voltage stress of each switching tube is uniform, and the damage of the switching tube...

AI Technical Summary

Problems solved by technology

However, the use of auxiliary DC power supply will reduce the utilization rate of equipment; in the RCD circuit, the additional loss generated by the snubber circuit will reduce the overall efficiency of the converter; the additional capacitor charging circuit increases the number of devices, reduces the utilization rate of devices, and has a negative impact on cost and power density. Negative Effects

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