Cell state-of-charge estimation for energy storage systems utilizing maintenance mode

A cell state-of-charge estimation method, comprising:

• measuring, by a measurement module comprising a voltage measurement device and a current measurement device, a cell voltage measurement of one or more cells of one or more stacks of an energy storage system, and a stack current measurement of one or more of the stacks;
• estimating, by a stack state-of-charge estimation module, a stack state-of-charge based on one or more cell voltage measurements and the stack current measurement;
• determining, by a static gradient generation module, a gradient of an open circuit voltage curve based on the one or more cell voltage measurements;
• determining, by a maintenance control module, an estimation signal based on the stack state-of-charge and the gradient for each of the one or more stacks;
• wherein the maintenance control module is configured to send instructions to a power conversion system to bring the one or more stacks to a specified state-of-charge based on the stack state-of-charge;
• and
• estimating, by a cell state-of-charge estimation module, a cell state-of-charge estimate based on the cell voltage measurements of one or more of the cells of the one or more stacks and in response to the estimation signal.

A state-of-charge estimation device comprising:

• an energy storage system comprising one or more stacks, wherein each of the one or more stacks contain one or more cells;
• a measurement module comprising a voltage measurement device and a current measurement device;
• wherein the voltage measurement device is configured to measure a cell voltage measurement of one or more of the cells of one or more of the stacks;
• wherein the current measurement device is configured to measure a stack current measurement of one or more of the stacks;
• a stack computing unit for each of the one or more stacks, the stack computing unit for receiving the cell voltage measurement and the stack current measurement and determining a stack state-of-charge;
• an energy management controller for determining a power request based on the stack state-of-charge;
• and
• a power conversion system for controlling the energy storage system based on the power request.