The present invention comprises a method and system for improving the energy efficiency of a vanadium flow battery, VFB. This is achieved by simultaneously reconditioning the VFB through in-situ activation of the electrodes.

A state detection device for fuel cell includes a supposed high-frequency impedance value setting unit configured to set a supposed high-frequency impedance value on the basis of an impedance measurement value belonging to an arc region of an impedance curve of the fuel cell, an actually measured high-frequency impedance value calculation unit configured to obtain an actually measured high-frequency impedance value on the basis of an impedance measurement value belonging to a non-arc region of the impedance curve of the fuel cell, and an ionomer resistance estimation unit configured to estimate a value obtained by subtracting the actually measured high-frequency impedance value from the supposed high-frequency impedance value as an ionomer resistance value. The supposed high-frequency impedance value setting unit sets a value of an intersection of an equivalent circuit impedance curve set on the basis of the impedance measurement value belonging to the arc region and a real ads as the supposed high-frequency impedance value.

A state detection device for fuel cell includes a supposed high-frequency impedance value setting unit configured to set a supposed high-frequency impedance value on the basis of an impedance measurement value belonging to an arc region of an impedance curve of the fuel cell, an actually measured high-frequency impedance value calculation unit configured to obtain an actually measured high-frequency impedance value on the basis of an impedance measurement value belonging to a non-arc region of the impedance curve of the fuel cell, and an ionomer resistance estimation unit configured to estimate a value obtained by subtracting the actually measured high-frequency impedance value from the supposed high-frequency impedance value as an ionomer resistance value. The supposed high-frequency impedance value setting unit sets a value of an intersection of an equivalent circuit impedance curve set on the basis of the impedance measurement value belonging to the arc region and a real ads as the supposed high-frequency impedance value.

A fuel cell internal state detection system includes estimation object state quantity setting unit for setting a suitable estimation object state quantity as an index of an internal state, an impedance value acquisition unit configured to obtain an impedance value of a fuel cell, an impedance usability judging unit configured to judge whether or not the obtained impedance value is usable for the calculation of the estimation object state quantity, estimation object state quantity calculation unit for calculating the estimation object state quantity set by the estimation object state quantity setting unit on the basis of the obtained impedance value when the impedance value is judged to be usable for the calculation of the estimation object state quantity by the impedance usability judging unit, and an unusable-scene process execution unit configured to perform an unusable-scene process when the impedance value is judged not to be usable for the calculation of the estimation object state quantity by the impedance usability judging unit.

A redox flow battery system includes a plurality of branch circuits electrically connecting a plurality of battery cell parts in parallel; a switching unit configured to switch conduction states of a closed loop in which the branch circuits are connected together; a circulation mechanism including a tank configured to store an electrolyte, and a pump configured to circulate the electrolyte from the tank to the battery cell parts; a detection unit configured to detect physical quantities correlating with open circuit voltages of the battery cell parts; a determination unit configured to determine, on a basis of the physical quantities detected by the detection unit, as to whether or not a voltage difference between the open circuit voltages of the battery cell parts is more than a predetermined value; and a control unit configured to control a switching operation of the switching unit such that, when the determination unit determines the voltage difference to be more than the predetermined value, the closed loop is brought into a non-conducting state and, when the determination unit determines the voltage difference to be equal to or less than the predetermined value, the closed loop is brought into a conducting state.

An embodiment of the present disclosure provides a hydrogen purge system and a method for controlling the same, which are capable of maintaining the hydrogen purge amount constant based on differential pressure between an anode and a cathode, regardless of the size of a hydrogen purge flow path of a purge valve, by allowing the opening degree of the purge valve to the hydrogen purge flow path to be adjusted by a current control or PWM control according to a mapping of the differential pressure between the anode and the cathode of a fuel cell stack.

The present invention provides a method for operating a redox-flow battery system comprising at least two battery modules, wherein the redox-flow battery system comprises a measuring device for providing a measured variable representing a measure of the state of charge of each battery module, and wherein the method comprises the following steps: cyclic operation of the redox flow battery system; detecting measured values by use of the measuring device; carrying out at least two balancing interventions on a battery module during a half cycle; and wherein the last balancing intervention carried out in the half-cycle is of the overcompensating type, and an SoC.sub.2 value used for this balancing intervention is predicted with the aid of pre-trained AI.