Photovoltaic module

Abstract

A photovoltaic module can include a solar cell module including a plurality of solar cells; a converter configured to convert a level of DC power input from the solar cell module; a DC-terminal capacitor configured to store DC power output from the converter; an inverter including a plurality of switching elements and configured to convert DC power from the DC-terminal capacitor into AC power; and a controller configured to control the inverter, in which the converter controls some switching elements among of the plurality of switching elements included in the inverter to perform switching at a third switching frequency, and controls other switching elements among the plurality of switching elements included in the inverter to perform switching at a forth switching frequency higher than the third switching frequency.

What is claimed is: 
     
         1 . A photovoltaic module comprising:
 a solar cell module including a plurality of solar cells;   a converter configured to convert a level of direct current (DC) power input from the solar cell module;   a DC-terminal capacitor configured to store DC power output from the converter;   an inverter having a plurality of switching elements including first, second, third and fourth switching elements, the inverter being configured to convert DC power from the DC-terminal capacitor into alternating current (AC) power; and   a controller configured to perform asynchronous pulse width modulation (PWM) control on the inverter.   
     
     
         2 . The photovoltaic module according to  claim 1 , wherein the controller is further configured to:
 control the first and fourth switching elements to perform switching according to the PWM control while the second switching is turned on, and   control the fourth and first switching elements to perform switching according to the PWM control while the third switching element is turned on.   
     
     
         3 . The photovoltaic module according to  claim 1 , wherein the inverter further includes:
 a first leg including some switching elements among the plurality of switching elements in the inverter, and   a second leg including other switching elements among the plurality of switching elements in the inverter,   wherein a switching frequency of the first leg is different than a switching frequency of the second leg.   
     
     
         4 . The photovoltaic module according to  claim 3 , wherein the some switching elements in the first leg of the inverter and the other switching elements in the second leg of the inverter are of different types. 
     
     
         5 . The photovoltaic module according to  claim 3 , wherein the some switching elements in the first leg of the inverter include GaN transistors or SiC transistors, and the other switching elements in the second leg of the inverter include metal-oxide-semiconductor field-effect-transistors (MOSFETs). 
     
     
         6 . The photovoltaic module according to  claim 1 , further comprising:
 a filter configured to filter the AC power output from the inverter.   
     
     
         7 . The photovoltaic module according to  claim 6 , wherein the filter includes:
 an inductor connected to an output terminal of the inverter; and   a capacitor connected between the inductor and another output terminal of the inverter.   
     
     
         8 . The photovoltaic module according to  claim 1 , wherein the converter further includes:
 a transformer having an input side connected to an output terminal of the full-bridge switching part;   a synchronous rectification part connected to an output side of the transformer;   a resonant capacitor connected between the transformer and the synchronous rectification part; and   a resonant inductor connected between the transformer and the synchronous rectification part.   
     
     
         9 . The photovoltaic module according to  claim 8 , wherein the full-bridge switching part includes:
 fifth and sixth switching elements connected in parallel; and   seventh and eighth switching elements respectively connected in series to the fifth and sixth switching elements,   wherein the input side of the transformer is connected between a first node located between the first and second switching elements and a second node located between the seventh and eighth switching elements.   
     
     
         10 . The photovoltaic module according to  claim 9 , wherein the controller is further configured to:
 control the full-bridge switching part to enter a buck mode and operate at a third switching frequency when a voltage of the DC-terminal capacitor is greater than or equal to a target voltage, and   control the full-bridge switching part to enter a boost mode and operate at a fourth switching frequency lower than the third switching frequency when the voltage of the DC-terminal capacitor is lower than the target voltage.   
     
     
         11 . The photovoltaic module according to  claim 8 , wherein the controller is further configured to:
 increase a phase difference between switching elements in the full-bridge switching part as a difference between a voltage of the DC-terminal capacitor and the target voltage increases, when the voltage of the DC-terminal capacitor is greater than or equal to the target voltage.   
     
     
         12 . The photovoltaic module according to  claim 8 , wherein the controller is further configured to:
 increase a turn-on duty of switching elements in the synchronous rectification part as a difference between a voltage of the DC-terminal capacitor and the target voltage increases, when the voltage of the DC-terminal capacitor is lower than the target voltage.   
     
     
         13 . The photovoltaic module according to  claim 8 , wherein the synchronous rectification part includes:
 ninth and tenth switching elements connected in series; and   first and second capacitors connected in series,   wherein the output side of the transformer is connected between a third node located between the ninth and tenth switching elements and a fourth node located between the first and second capacitors.   
     
     
         14 . The photovoltaic module according to  claim 1 , wherein the inverter further includes:
 the first and forth switching elements connected in series; and   the second and third switching elements connected in series,   wherein the AC power is output through a node located between the first and forth switching elements and a node located between the second and third switching elements.   
     
     
         15 . The photovoltaic module according to  claim 14 , wherein the controller is further configured to:
 control the second and third switching elements to operate at a first switching frequency and control the first and forth switching elements to operate at a second switching frequency lower than the first switching frequency.   
     
     
         16 . The photovoltaic module according to  claim 14 , wherein the controller is further configured to:
 control the first and forth switching elements to perform switching according to PWM control while the second switching element is turned on, and   control the second and third switching elements to perform switching according to PWM control while the third switching element is turned on.   
     
     
         17 . The photovoltaic module according to  claim 1 , wherein the DC-terminal capacitor includes a film capacitor. 
     
     
         18 . A photovoltaic module comprising:
 a solar cell module including a plurality of solar cells;   a converter configured to convert a level of direct current (DC) power input from the solar cell module;   a DC-terminal capacitor configured to store DC power output from the converter;   an inverter including a plurality of switching elements and configured to convert DC power from the DC-terminal capacitor into alternating current (AC) power; and   a controller configured to control the inverter,   wherein the converter includes a full-bridge switching part configured to switch the DC power,   wherein the controller is further configured to:   control the full-bridge switching part to enter a buck mode and operate at a first switching frequency when a voltage of the DC-terminal capacitor is greater than or equal to a target voltage, and   control the full-bridge switching part to enter a boost mode and operate at a second switching frequency lower than the first switching frequency when the voltage of the DC-terminal capacitor is lower than the target voltage, and   wherein the converter is further configured to:   control some switching elements among the plurality of switching elements in the inverter to perform switching at a third switching frequency, and   control other switching elements among the plurality of switching elements in the inverter to perform switching at a forth switching frequency higher than the third switching frequency.   
     
     
         19 . The photovoltaic module according to  claim 18 , wherein the controller includes:
 a current controller configured to output a DC-terminal voltage command based on an output current flowing through the inverter;   a voltage command compensator configured to compensate for a voltage command based on the DC-terminal voltage command and a voltage across both terminals of the DC-terminal capacitor;   a low-speed switching driving signal generator configured to output a low-speed switching driving signal at the third switching frequency based on an output value from the voltage command compensator; and   a high-speed switching driving signal generator configured to output a high-speed switching driving signal at the forth switching frequency based on the output value from the voltage command compensator.   
     
     
         20 . The photovoltaic module according to  claim 18 , wherein the some switching elements in the converter and the other switching elements in the converter are of different types of transistors.