Method and system for an ac battery

Abstract

A method and system for AC battery operation. In one embodiment, the method comprises determining, at a battery management unit (BMU) coupled to an AC battery comprising a power converter and a battery that is rechargeable, a bias control voltage that indicates a state of a charge process of the AC battery; and coupling, by a bias control module of the BMU, the bias control voltage to the power converting for communicating the state of the charge process to and from the BMU and the power converter.

1 . An AC battery system, comprising:
 a battery that is rechargeable;   a power converter coupled to the battery;   a battery management unit (BMU) coupled to the battery and the BMU; and   a first switch and a second switch connected between the battery and the power converter and coupled to the BMU for driving the first switch to control battery discharge and driving the second switch to control battery charge.   
     
     
         2 . The AC battery system of  claim 1 , wherein the first switch and the second switch are connected in series between a first terminal of the battery and a first terminal of the power converter. 
     
     
         3 . The AC battery system of  claim 1 , wherein a body diode cathode terminal of the first switch is coupled to a first terminal of the battery and a body diode cathode terminal of the second switch is coupled to a first terminal of the power converter. 
     
     
         4 . The AC battery system of  claim 1 , wherein respective gate terminals of the first switch and second switch are coupled to the BMU. 
     
     
         5 . The AC battery system of  claim 1 , wherein the first switch and the second switch each comprise a body diode. 
     
     
         6 . The AC battery system of  claim 5 , wherein a configuration of the body diode of the first switch and the body diode of the second switch allows current to be blocked in one direction but not the other direction depending on a state of each of the first switch and the second switch. 
     
     
         7 . The AC battery system of  claim 6 , wherein when the first switch is active while the second switch is inactive, battery discharge is enabled to allow current to flow from the battery to the power converter through the body diode of the second switch,
 wherein when the first switch is inactive while the second switch is active, battery charge is enabled to allow current flow from the power converter to the battery through the body diode of the first switch, and   wherein when the first switch and the second switch are both active, the AC battery system is in a normal mode where the battery can be charged or discharged.   
     
     
         8 . The AC battery system of  claim 1 , further comprising a current measurement device connected to the BMU for receiving information on a measured current, and receiving an input from the battery indicating a battery cell voltage and temperature. 
     
     
         9 . The AC battery system of  claim 8 , wherein the current measurement device is connected to a second terminal of the battery and a second terminal of the power converter. 
     
     
         10 . The AC battery system of  claim 1 , wherein the BMU is coupled across a first terminal of the power converter and a second terminal of the power converter for providing an inverter bias control voltage to the power converter. 
     
     
         11 . The AC battery system of  claim 1 , wherein the power converter is a bidirectional inverter. 
     
     
         12 . A method for AC battery operation, comprising:
 determining a state of charge (SOC) of a battery that is rechargeable;   when the battery is discharged to a first predetermined amount, deactivating a first switch to disable current flow from the battery to a power converter and activating a second switch to enable current flow from the power converter to the battery; and   when the battery is charged to a second predetermined amount, which is different from the first predetermined amount, activating the first switch to enable current flow from the battery to the power converter and deactivating the second switch to disable current flow from the power converter to the battery.   
     
     
         13 . The method of  claim 12 , wherein the first switch and the second switch are connected in series between a first terminal of the battery and a first terminal of the power converter. 
     
     
         14 . The method of  claim 12 , wherein a body diode cathode terminal of the first switch is coupled to a first terminal of the battery and a body diode cathode terminal of the second switch is coupled to a first terminal of the power converter. 
     
     
         15 . The method of  claim 12 , wherein respective gate terminals of the first switch and second switch are coupled to the BMU. 
     
     
         16 . The method of  claim 12 , wherein the first switch and the second switch each comprise a body diode. 
     
     
         17 . The method of  claim 16 , wherein a configuration of the body diode of the first switch and the body diode of the second switch allows current to be blocked in one direction but not the other direction depending on a state of each of the first switch and the second switch. 
     
     
         18 . The method of  claim 12 , further comprising receiving information on a measured current from a current measurement device and receiving an input from the battery indicating a battery cell voltage and temperature. 
     
     
         19 . The method of  claim 18 , wherein the current measurement device is connected to a second terminal of the battery and a second terminal of the power converter. 
     
     
         20 . The method of  claim 12 , wherein the power converter is a bidirectional inverter.