Hitachi Energy Ltd

Hongyang Zhang

Theodore Soong

Rasool Heydari

Pinaki Mitra

Filiph Appelgren

Mikael Tenerz

There is disclosed herein a method to operate a system comprising an energy storage system (ESS) and a converter. The ESS being connected to the converter such that a DC-side of the converter forms DC terminals between which at least one string of modules of the ESS is connected. The method comprises receiving a bypass request to bypass at least one module in the ESS, based on a total number of modules to be bypassed exceeding a number of redundant modules, controlling the converter to reduce the terminal voltage of the ESS; and after reducing the terminal voltage of the ESS, bypassing the module. There is further disclosed herein a system comprising a central controller performing said method.

Method to operate a system comprising an energy storage system in response to a bypass request based on a total number of modules to be bypassed

The present disclosure provides a method and a control unit for controlling a power unit connected at a connection point to a power grid. The method comprises obtaining a power oscillation damping (POD) signal from a POD controller, based on a power oscillation in the power grid. A gain value may be determined based on a difference between a first voltage measurement at the connection point and a first voltage reference, or an estimated short circuit ratio of the power grid. The POD signal may be added to an input signal of a power unit regulator to obtain an intermediate reference signal. A combined reference signal may be determined based on adding the POD signal, multiplied by the gain value, to the intermediate reference signal. The power unit may be operated using the determined combined reference signal to damp the oscillation in the grid.

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Stockholm, Sweden

Hongyang Zhang