Safety Switch for Photovoltaic Systems

Abstract

Various implementations described herein are directed to a methods and apparatuses for disconnecting, by a device, elements at certain parts of an electrical system. The method may include measuring operational parameters at certain locations within the system and/or receiving messages from control devices indicating a potentially unsafe condition, disconnecting and/or short-circuiting system elements in response, and reconnection the system elements when it is safe to do so. Certain embodiments relate to methods and apparatuses for providing operational power to safety switches during different modes of system operation.

1 - 25 . (canceled) 
     
     
         26 . A safety switch comprising:
 a first connector comprising a first conductor;   a second connector comprising a second conductor;   a switch circuit connected between the first conductor and the second conductor, wherein the switch circuit is configurable into: an ON state that provides a direct-current serial path between the first conductor and the second conductor, and an OFF state that disconnects the direct-current serial path; and   circuitry connected between the first conductor and the second conductor and configured to:
 receive power across the first and the second conductors; 
 control, utilizing the power, the switch circuit from the OFF state into the ON state; and 
 control, in response to a loss of the power, the switch circuit from the ON state into the OFF state. 
   
     
     
         27 . The safety switch of  claim 26 , wherein the circuitry is configured to receive the power at a first voltage between the first conductor and the second conductor when the switch circuit is in the ON state, and receive the power at a second voltage between the first conductor and the second conductor when the switch circuit is in the OFF state. 
     
     
         28 . The safety switch of  claim 27 , wherein the circuitry is configured to maintain, while receiving the power, the switch circuit in the ON state. 
     
     
         29 . The safety switch of  claim 27 , wherein the first voltage is between 15-200 millivolts when the switch circuit is in the ON state, and the second voltage is greater than 25V when the switch circuit is in the OFF state. 
     
     
         30 . The safety switch of  claim 26 , wherein:
 the circuitry is configured to receive one or more power line communication signals transmitted to the safety switch via the first conductor or the second conductor; and   the control of the switch circuit into the ON state is based on the circuitry receiving the one or more power line communication signals.   
     
     
         31 . The safety switch of  claim 30 , wherein the one or more power line communication signals comprises an alternating-current signal over the first conductor or the second conductor. 
     
     
         32 . The safety switch of  claim 26 , wherein, when in the ON state, the switch circuit has a current-voltage relationship that causes a voltage across the first and the second conductors to be between 15-200 millivolts when 10 amperes passes through the direct-current serial path. 
     
     
         33 . The safety switch of  claim 26 , wherein the switch circuit has an on-resistance that causes a second voltage across the first and the second conductors to be generated in response to a serial current from the first conductor to the second conductor through the direct-current serial path. 
     
     
         34 . The safety switch of  claim 26 , further comprising a diode having a cathode connected to the first conductor and an anode connected to the second conductor. 
     
     
         35 . The safety switch of  claim 26 , wherein:
 the circuitry is configured to receive the power at a first voltage between 15-200 millivolts when the switch circuit is in the ON state;   the switch circuit comprises a transistor connected, via a source or emitter terminal and a drain or collector terminal, between the first and the second conductors; and   the circuitry is configured to generate a control voltage between a gate or base terminal of the transistor and the source or emitter terminal sufficient to maintain the switch circuit in the ON state.   
     
     
         36 . The safety switch of  claim 35 , wherein:
 the circuitry comprises a power circuit configured to generate the control voltage from the first voltage,   the control voltage is greater than the first voltage, and   the power circuit is configured to cease generating the control voltage based on:
 a serial current flowing between the first and the second conductors through the direct-current serial path falling below a threshold level, or 
 receipt of a power line communication signal comprising a shutdown command. 
   
     
     
         37 . The safety switch of  claim 26 , wherein the circuitry comprises an auxiliary power circuit configured to:
 receive the power from an auxiliary current flowing from the first conductor to the second conductor through the auxiliary power circuit.   
     
     
         38 . The safety switch of  claim 26 , wherein the circuitry is configured to:
 receive a keep alive signal via the first conductor or the second conductor;   maintain the switch circuit in the ON state based on receiving the keep alive signal; and   control the switch circuit into the OFF state based on an absence of the keep alive signal.   
     
     
         39 . The safety switch of  claim 38 , wherein the keep alive signal provides the power. 
     
     
         40 . The safety switch of  claim 26 ,
 wherein the switch circuit comprises a transistor; and   wherein the circuitry comprises:
 a communication circuit configured to receive power line communication signals on the first conductor or the second conductor; 
 an auxiliary power circuit configured to convert the power to converted power; and 
 a controller circuit configured to:
 generate, from the converted power, a control voltage on a gate or base terminal of the transistor, and 
 based on the power line communication signals, vary the control voltage to control the transistor into the ON state and into the OFF state. 
 
   
     
     
         41 . The safety switch of  claim 40 , wherein the controller circuit is configured to, in response to the power line communication signals, toggle the control voltage between a first value of less than 1 volt and a second value of greater than 5 volts. 
     
     
         42 . The safety switch of  claim 26 ,
 wherein the safety switch comprises a transistor connected between the first conductor and the second conductor; and   the circuitry comprises an auxiliary power circuit configured to convert a drain-to-source or collector-to-emitter voltage across the transistor to a gate-to-source or base-to-emitter voltage applied to a gate or base terminal of the transistor, wherein the gate-to-source or base-to-emitter voltage is greater than the drain-to-source or collector-to-emitter voltage.   
     
     
         43 . The safety switch of  claim 26 , further comprising a resistor connected between the first conductor and the second conductor and in parallel with the switch circuit. 
     
     
         44 . The safety switch of  claim 26 , wherein the first conductor is configured to be connected to a photovoltaic panel connected to a power device, wherein the power device is configured to, based on a change in current flowing through the safety switch, cease drawing power from the photovoltaic panel to turn the safety switch to the OFF state. 
     
     
         45 . The safety switch of  claim 26 , wherein the switching circuit comprises a transistor that provides the direct-current serial path, and wherein the circuitry is connected in across the transistor. 
     
     
         46 . A system comprising:
 a photovoltaic string comprising a pair of photovoltaic panels coupled in series through a safety switch;   wherein the safety switch is connected inline between the pair of photovoltaic panels;   wherein the safety switch has an ON state that provides a direct-current serial path between the pair of photovoltaic panels, and an OFF state that disconnects the direct-current serial path; and   wherein the safety switch comprises circuitry configured to:
 receive auxiliary power through the photovoltaic string,
 utilize the auxiliary power to control the safety switch from the OFF state to the ON state, and
 in response to a loss of the auxiliary power, control the safety switch from the ON state to the OFF state; and 
 
 
   a power device comprising:
 a power converter having inputs connected across the photovoltaic string, and 
 a control circuit configured to control photovoltaic power generated by the pair of photovoltaic panels. 
   
     
     
         47 . A method comprising:
 receiving, between first and second conductors of a safety switch, power;   controlling, utilizing the power, the safety switch to an ON state that provides a direct-current serial path between the first and the second conductors; and   controlling, in response to a loss of the power, the safety switch into the OFF state that disconnects the direct-current serial path.   
     
     
         48 . A method comprising:
 receiving, at an output of a power converter, a first power line communication signal indicating for the power converter to shut down;   controlling, based on receiving the first power line communication signal, the power converter from a first mode of operation that extracts photovoltaic power from a photovoltaic string according to a maximum power point tracking (MPPT) algorithm, to a second mode of operation that ceases to draw the photovoltaic power resulting in loss of photovoltaic current in the photovoltaic string,
 wherein the photovoltaic string comprises a plurality of photovoltaic panels coupled in series through one or more safety switches, and 
 wherein each safety switch of the one or more safety switches is connected inline between a respective adjacent pair of the plurality of photovoltaic panels; and 
   controlling, in response to the loss of photovoltaic current, the one or more safety switches from an ON state to an OFF state, wherein each safety switch of the one or more safety switches in the ON state provides a direct-current serial path between the respective adjacent pair of the plurality of photovoltaic panels to which the safety switch is connected, and in the OFF state disconnects the direct-current serial path.