Electric marine propulsion system and control method with voltage adaptation

Abstract

An electric marine propulsion system configured to propel a marine vessel includes at least one electric motor powered by a power storage system and configured to rotate a propulsor to propel the marine vessel and a control system. The control system is configured to determine a voltage change due to a change in demand level of the electric motor, determine a minimum voltage at a maximum rated demand level for the electric motor based on the voltage change, determine an adjusted command for the electric motor based on the minimum voltage and a current demand input, and control the electric motor based on the adjusted command.

We claim: 
     
         1 . An electric marine propulsion system configured to propel a marine vessel, the system comprising:
 at least one electric motor powered by a power storage system and configured to rotate a propulsor to propel the marine vessel;   a control system configured to:
 determine a voltage change due to a change in demand level of the electric motor; 
 determine a minimum voltage at a maximum rated demand level for the electric motor based on the voltage change; 
 determine an adjusted command for the electric motor based on the minimum voltage and a current demand input; and 
 control the electric motor based on the adjusted command. 
   
     
     
         2 . The system of  claim 1 , wherein the control system is further configured to determine an adapted system resistance based on the voltage change, and wherein the minimum voltage is determined based on the adapted system resistance. 
     
     
         3 . The system of  claim 2 , wherein the adapted system resistance includes an internal resistance of at least one battery in the power storage system and a resistance of connection elements connecting the electric motor to the at least one battery. 
     
     
         4 . The system of  claim 2 , wherein the control system is further configured to determine a filtered adapted system resistance based on the adapted system resistance over time, and wherein the minimum voltage is determined based on the filtered adapted system resistance. 
     
     
         5 . The system of  claim 2 , wherein the control system is further configured to:
 identify the change in demand level that is at least a threshold change;   identify the voltage change as a corresponding change in input voltage at the electric motor that corresponds with the threshold change in demand level; and   determine the adapted system resistance based on the change in demand level and the corresponding change in input voltage.   
     
     
         6 . The system of  claim 5 , wherein the change in demand level is one of a threshold change in motor current, a threshold change in motor torque, and a threshold change in helm command. 
     
     
         7 . The system of  claim 5 , wherein the control system is further configured to:
 identify a first steady state demand level and measure a first motor input voltage at the first steady state demand level;   identify a second steady state demand level and measure a second motor input voltage at the second steady state demand level;   wherein the change in demand level is a difference between the first steady state demand level and the second steady state demand level.   
     
     
         8 . The system of  claim 1 , wherein the maximum rated demand level is a maximum rated torque for the electric motor, wherein the current demand input is a current torque demand, and the adjusted command is a torque command to the electric motor. 
     
     
         9 . The system of  claim 1 , wherein the current demand input is based on a user demand input at a user input device. 
     
     
         10 . The system of  claim 9 , wherein the control system is further configured to rescale user demand input values from the user input device based on the minimum voltage. 
     
     
         11 . The system of  claim 9 , wherein the control system is further configured to limit user authority over output of the electric motor based on the minimum voltage. 
     
     
         12 . The system of  claim 1 , further comprising a command table stored in memory comprising adjusted command values based on minimum voltage values;
 wherein the control system is further configured to access the command table based on the minimum voltage and the current demand input to determine the adjusted command.   
     
     
         13 . A method of controlling an electric marine propulsion system comprising at least one electric motor powered by a power storage system and configured to rotate a propulsor to propel a marine vessel, the method comprising:
 determining a voltage change due to a change in demand level of the electric motor;   determining a minimum voltage at a maximum rated demand level for the electric motor based on the voltage change;   determining an adjusted command for the electric motor based on the minimum voltage and a current demand input; and   controlling the electric motor based on the adjusted command.   
     
     
         14 . The method of  claim 13 , further comprising determining an adapted system resistance based on the voltage change, wherein the minimum voltage is determined based on the adapted system resistance. 
     
     
         15 . The method of  claim 14 , wherein the adapted system resistance includes an internal resistance of at least one battery in the power storage system and a resistance of connection elements connecting the electric motor to the power storage system. 
     
     
         16 . The method of  claim 14 , further comprising determining a filtered adapted system resistance based on the adapted system resistance over time, wherein the minimum voltage is determined based on the filtered adapted system resistance. 
     
     
         17 . The method of  claim 14 , further comprising:
 identifying the change in demand level that is at least a threshold change;   identifying a corresponding change in input voltage at the motor that corresponds with the threshold change in demand level; and   determining the adapted system resistance based on the change in demand level and the corresponding change in input voltage.   
     
     
         18 . The method of  claim 17 , wherein the change in demand level is one of a threshold change in motor current, a threshold change in motor torque, and a threshold change in helm command. 
     
     
         19 . The method of  claim 17 , further comprising:
 identifying a first steady state demand level and measure a first motor input voltage at the first steady state demand level;   identifying a second steady state demand level and measure a second motor input voltage at the second steady state demand level;   wherein the change in demand level is a difference between the first steady state demand level and the second steady state demand level.   
     
     
         20 . The method of  claim 13 , wherein the maximum rated demand level is a maximum rated torque for the electric motor, wherein the current demand input is a current torque demand, and the adjusted command is a torque command to the electric motor. 
     
     
         21 . The method of  claim 20 , wherein the current torque demand is based on a user demand input at a user input device. 
     
     
         22 . The method of  claim 21 , further comprising rescaling user demand input values from the user input device based on the minimum voltage. 
     
     
         23 . The method of  claim 21 , further comprising limiting user authority over output of the electric motor based on the minimum voltage.