A control method for a modular multilevel converter with energy storage function

Abstract

The invention discloses a method for controlling a modular multilevel converter with an energy storage function, wherein the converter comprises three phase units, each phase unit comprises an upper bridge arm, a lower bridge arm, an upper bridge arm inductor and a lower bridge arm inductor, and each one of the upper bridge arm and the lower bridge arm is composed of a half-bridge sub-module and a quasi full-bridge energy storage sub-module, which are connected in series in a hybrid manner. The method comprises the following steps: determining modulating waves of each sub-module in the bridge arm of each phase according to a to-be-output instruction voltage waveform of each phase, wherein the modulating waves of the sub-module comprises half-bridge sub-module modulating waves and quasi full-bridge energy storage sub-module modulating waves; and performing comparison according to carriers of each sub-module in the bridge arm of each phase and the modulating waves of the sub-module to generate a control signal, and separately controlling the turn-on or turn-off of the sub-modules in the bridge arm of each phase. The modular multilevel converter with the energy storage function can increase the inertia of a new energy system, the charging and discharging current of a battery used for energy storage is smooth, and the voltage level is relatively low, therefore the efficient operation and the safety of the battery are guaranteed.

Description

technical field [0001] The invention belongs to the technical field of electrical automation equipment, and in particular relates to a control method of a modular multilevel converter with an energy storage function. Background technique [0002] In the existing technology, the sub-module with energy storage function directly connects the battery next to the capacitor of the sub-module, so that the battery can withstand the pulsating current of one or two times the power frequency, which has great impact on the efficient operation of the battery and the cost of the whole life cycle. Unfavorable; at the same time, the sub-module capacitor voltage in actual working conditions is generally greater than 1500V voltage level. For high-rate batteries represented by lithium-ion batteries, based on the balance of battery state of charge and fault protection, it is difficult to achieve in terms of cost and safety. Such a high series voltage. [0003] After retrieval, the Chinese pate...

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Problems solved by technology

[0005] The above-mentioned patents cannot solve the problem of battery voltage levels, because many sub-modules are used and cannot realize energy storage, and the battery voltage is low; secondly, the sub-module structures proposed in the above-mentioned patents all adopt the scheme that the battery is connected in parallel next to the DC capacitor, and the battery will inevitably Withstand the pulsating current of double power frequency and double power frequency, which is not good for the efficient operation of the battery and the cost of the whole life cycle

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