Energy storage system and control method thereof

Abstract

The invention provides an energy storage system which comprises a controller, a main circuit, a push-pull converter, a cycloconverter, a filter inductor and a sampling circuit. The controller is used for controlling the generation of an SVPWM (Space Vector Pulse Width Modulation) signal and a PWM (Pulse Width Modulation) signal to obtain a discrete SVPWM signal, the main circuit comprises an energy storage device for storing and releasing electric energy, the push-pull converter comprises a high-frequency transformer and is boosted by adopting the high-frequency transformer to electrically isolate the input from the output of the energy storage system, the cycloconverter is used for converting a high-frequency alternating voltage into a power frequency alternating voltage, the filter inductor is used for filtering a grid current, and the sampling circuit is used for acquiring a voltage and a current of an external circuit. The energy storage system can generate discrete pulse-type SVPWM and has the advantages of higher utilization rate of the bus voltage, low total harmonic content and wide scope of application. The invention also provides a control method of the energy storage system.

Description

technical field [0001] The present invention relates to an energy storage system and a control method, in particular to an energy storage system and a control method for peak-shaving and valley-filling of a power grid. Background technique [0002] With the development of power electronics technology, energy storage systems are used more and more widely, such as uninterruptible power supply (UPS), electric vehicles, and energy storage devices for power grid shaving and filling valleys. The energy storage device stores electric energy during low power consumption periods (charging), and releases electric energy to support the grid during peak power consumption periods (discharging). In order to achieve the effect of peak shaving and valley filling, the converter between the energy storage device and the grid must not only have two-way conversion capability, but also require a fast response to the conversion and a unit power factor of the system. [0003] The patent "energy s...

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Problems solved by technology

Power factor correction can be done, but the buck inverter requires the bus voltage to be higher than the AC output voltage, so this topology is not suitable for low-voltage energy storage devices, such as supercapacitors

And there is no electrical isolation between the grid and the energy storage device

IEEE Trans.on Power Electronics [Journal of Power Electronics] published the article "Three-Phase Boost-Type Grid-Connected Inverter" [Three-Phase Boost-Type Grid-Connected Inverter] in the fifth issue of 2008. A boost inverter is formed, and the single-cycle control strategy is adopted to reduce the DC side voltage to a certain extent. However, the boost converter has a limited boost capability, and it is still not suitable for ultra-low voltage energy storage devices such as supercapacitors. boost inverter, increasing the total harmonic content (THD) of the output current

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