Patent Publication Number: US-9906119-B2

Title: Method of ripple-compensation control and electrical energy conversion device using the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is based on, and claims priority from, Taiwan Application Serial Number 104132375, filed 30 Sep. 2015, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The technical field relates to the method of ripple-compensation control and electrical energy conversion device using the same. 
     BACKGROUND 
     The converter circuit converts an AC power source to a DC power source, or a DC power source to an AC power source. The common application is to use a controller to control the DC side voltage of the converter, and normally reduce the gain of the controller when controlling the DC side voltage of the converter to approach a DC constant. 
     SUMMARY 
     An embodiment of a ripple-compensation control method is disclosed. The method is adopted by a converter controlled by a controller which controls a first voltage of a DC node of the converter according to a command value, comprising: obtaining a ripple-component voltage of the first voltage corresponding to an AC node of the converter; and generating the command value based on the ripple-component voltage and controlling the converter according to the command value. 
     An embodiment of an electrical energy conversion device applying ripple-compensation control is disclosed. The electrical energy conversion device comprises a converter configured to perform electrical energy conversion, a controller coupled to control terminals of the converter and controlling a first voltage of a DC node of the converter according to a command value, and a ripple-compensation unit configured to generate a ripple-component voltage of the first voltage and provide the command value generated based on the ripple-component voltage to the controller. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  shows a block diagram of an electrical energy conversion device according to an exemplary embodiment; 
         FIG. 2  shows an electrical energy conversion device according to an exemplary embodiment; 
         FIGS. 3A-3C  show examples of ripple detector according to some exemplary embodiments; 
         FIG. 4A  shows an electrical energy conversion device according to an exemplary embodiment; 
         FIG. 4B  shows a circuit which combines single phase AC/DC inverter and boost-type DC/DC converter according to an exemplary embodiment; 
         FIG. 5A  shows an electrical energy conversion device according to an exemplary embodiment; 
         FIG. 5B  shows a circuit which combines single phase AC/DC inverter and boost-type power decoupling unit according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
       FIG. 1  illustrates a block diagram of the electrical energy conversion device  100  according to an exemplary embodiment. The electrical energy conversion device  100  comprises the converter  101 , ripple-compensation unit  102  and controller  103 . The converter  101  is configured to perform the conversion as DC-to-AC or AC-to-DC, and the controller  103  controls the performance of the conversion. 
     According to one embodiment of the present disclosure, the ripple-compensation unit  102  combines a ripple-component power, which is generated at the AC side of the converter  101 , and a predetermined command value (e.g. a predetermined command voltage) to generate a command value (e.g. a command voltage), and then provides the command value to the controller  103 . The controller  103  controls the DC side voltage of the converter  101  according to the command value, and makes the DC side voltage of the converter  101  contain the voltage component corresponding to the ripple-component power in order to improve the power balance between the DC side and AC side of the converter  101 . 
       FIG. 2  illustrates the electrical energy conversion device  200  according to one embodiment of the present disclosure. The electrical energy conversion device  200  comprises the converter  201 , controller  202 , first filter  203  and ripple-compensation unit  208 . The ripple-compensation unit  208  comprises a first computation device  204  and a ripple detector  205 . In this embodiment, the converter  201  is a single phase AC/DC inverter. The controller  202  is coupled to the control terminal and DC node  209 , placed at the DC side, of the converter  201 , controlling the voltage (which is noted as the first voltage V d ) of the DC node  209  according to the command voltage V c , and the command voltage V c  is provided by the ripple-compensation unit  208 . The ripple-compensation unit  208  generates the ripple-component current I dr  corresponding to the ripple-component power of the power at the AC side of the converter  201  through the ripple detector  205 . The ripple-component current I dr  is transformed into ripple-component voltage V dr  by an integrator  206  of the first computation device  204 , and the ripple-component voltage V dr  is combined with the predetermined command voltage V cp  to generate the command voltage V c  through the adder  207  of the first computation device  204 . The controller  202  controls the first voltage V d  based on the command voltage V c  which relates to the ripple-component power. Based on the operation of the controller  202 , the first voltage V d  will approach the command voltage V c , and when the controller  202  provides higher gain performance, the first voltage V d  will approach the command voltage V c  more quickly. 
     Based on the embodiment described above, the first voltage V d  will reflect the change of the ripple-component power, and therefore the converter  201  can have balanced power between the DC side and AC side thereof. It will be seen from this that the described embodiment can make the converter  201  have balanced power between the DC side and the AC side without degrading the gain performance of the controller  202 . In other words, the described embodiment can maintain the proper gain performance of the controller  202  and reduce the current harmonic distortion at the AC side of the converter  201  at the same time. 
     In this embodiment, the first filter  203  is a low pass filter consisting of the inductor L f  and capacitor C f , but the present disclosure is not limited by this description. In this embodiment, the first computation device  204  consists of the integrator  206  and adder  207 , but the present disclosure is not limited by this description. In some embodiments, the converter  201  may be any type of electrical energy converter performing DC-to-AC or AC-to-DC conversion. In some embodiments, the ripple detector  205  may detect the ripple-component current I dr  through various methods, such as those that are depicted in  FIGS. 3A-3C , but the present disclosure is not limited by this description. In some embodiments, the AC current I o  will be sent to the controller  202 . 
       FIG. 3A  illustrates the ripple detector  3001  according to an exemplary embodiment. The ripple detector  3001  comprises a second filter  308  and a subtractor  309 . The ripple detector  3001  obtains the DC current I d  at the DC side of the converter  201  through a sampling circuit (which is not shown in  FIG. 3A ). The DC current I d  is converted to ripple-component current I dr  by the operation of the second filter  308  and the subtractor  309 . 
       FIG. 3B  illustrates the ripple detector  3002  according to another exemplary embodiment. Ripple detector  3002  comprises the second computation device  302 , second filter  308  and subtractor  309 . The second computation device  302  comprises the inverter  303 , differentiator  304 , adder  305 , multiplier  306 , and divider  307 . The ripple detector  3002  obtains the output current at the AC side of the converter  201  (AC current I ac ), the output voltage of the first filter  203  (AC voltage V o ) and the first voltage V d  through a first, second, and third sampling circuit (which are not shown in  FIG. 3B ), respectively. The second computation device  302  receives and computes the AC current I ac , AC voltage V o  and the first voltage V d  to generates the equivalent DC current I 3dd . The equation (1) that generates the equivalent DC current I 3dd  is expressed below. 
     
       
         
           
             
               
                 
                   
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     The equation (1) transforms the AC current I ac  into an output power at the AC side of the converter  201  after the operation of the multiplier  306  in  FIG. 3B , and divides the output power by the first voltage V d  to generate the equivalent DC current I 3dd . The equivalent DC current I 3dd  is converted to ripple-component current I dr  through the operation of the second filter  308  and subtractor  309 . In this embodiment, the second filter  308  may be a low pass filter or a moving average filter, but the present disclosure is not limited by this description. 
       FIG. 3C  illustrates the ripple detector  3003  according to an alternative embodiment. The ripple detector  3003  comprises the second computation device  310 , second filter  308 , and subtractor  309 . The second computation device  310  comprises the inverter  303 , differentiator  304 , differentiator  312 , adder  305 , adder  311 , multiplier  306 , and divider  307 . The ripple detector  3003  obtains the output current of the first filter  203  (AC current I o ), the output voltage of the first filter  203  (AC voltage V o ) and the first voltage V d  through a fourth, fifth, and sixth sampling circuit (which are not shown in  FIG. 3C ) respectively. The second computation device  310  receives and computes the AC current I o , AC voltage V o  and the first voltage V d  to generates an equivalent DC current I 3dd . The equation (2) that generates the equivalent DC current I 3dd  is expressed below. 
     
       
         
           
             
               
                 
                   
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     The equation (2) transforms the AC current I o  and AC voltage V o  into the AC current I ac  after the operation of the adder  311  in  FIG. 3C , and then performs the computation as equation (1) to generate the ripple-component current I dr . In this embodiment, the second filter  308  may be a low pass filter or a moving average filter, but the present disclosure is not limited by this description. 
       FIG. 4A  illustrates the electrical energy conversion device  400  according to an exemplary embodiment. The electrical energy conversion device  400  comprises the converter  4001 , controller  202 , first filter  203  and ripple-compensation unit  208 . The converter  4001  comprises the first conversion circuit  401 , second conversion circuit  402  and capacitors C d  and C dc . 
     In this embodiment, the first conversion circuit  401  is a single phase AC/DC inverter. The DC node  403  at the DC side of the first conversion circuit  401  is coupled to the second conversion circuit  402  and controller  202 , and the second conversion circuit  402  is a DC/DC converter. The controller  202  controls the voltage of the DC node  403  (which is noted as the first voltage V 4d ) according to the command voltage V 4c , and the command voltage V 4c  is provided by the ripple-compensation unit  208 . The ripple-compensation unit  208  generates a ripple-component current I 4dr  corresponding to the ripple-component power of the power at the AC side of the first conversion circuit  401 . The ripple-component current I 4dr  is transformed into a ripple-component voltage V 4dr  by the integrator  206  of the first computation device  204 , and the adder  207  of the first computation device  204  combines the ripple-component voltage V 4dr  and a predetermined command voltage V 4cp  to generate the command voltage V 4c . The controller  202  controls the first voltage V 4d  according to the command voltage V 4c  which relates to the ripple-component power, generates a pulse width modulation (PWM) signal, and sends the PWM signal to the control terminal of the second conversion circuit  402  in order to control the output thereof. Based on the operation of the controller  202 , the first voltage V 4d  will approach the command voltage V 4c , and when the controller  202  provides higher gain performance, the first voltage V 4d  will approach the command voltage V 4c  more quickly. 
     Based on the embodiment described above, the first voltage V 4d  contains the components related to the ripple-component power, and therefore the first conversion circuit  401  can have balanced power between the DC side and AC side thereof to make the electrical energy conversion device  400  achieve a power balance. It will be seen from this that the controller  202  of the electrical energy conversion device  400  can maintain proper gain performance, and because the DC side of the first conversion circuit  401  also contains the components related to the ripple-component power, the AC side of the first conversion circuit  401  can maintain the original AC waveform, and therefore the distortion status of the AC current at the AC side of the first conversion circuit  401  can be reduced. Additionally, based on the DC side and AC side of the first conversion circuit  401  being able to achieve a power balance, the amount of ripple current caused by the ripple-component power will flow to a capacitor C d  after the first voltage V 4d  containing the components related to the ripple-component power, so the amount of ripple components, which are caused by the ripple-component power, of the DC current I dc  can also be reduced. Meanwhile, the capacitor C d  does not need to be enlarged to make the first voltage V 4d  approach a DC constant. 
     In some embodiments, the first conversion circuit  401  may be any type of electrical energy converter performing DC-to-AC or AC-to-DC conversion, and the second conversion circuit  402  may be any type of DC/DC converter comprising boost type, buck type, or resonant circuits. In some embodiments, the DC current I dc  will be sent to the controller  202 . As  FIG. 4B  shows, the first conversion circuit  401  may be a single phase AC/DC inverter consisting of power switch components Q i1˜i4  and diodes D 11˜14 , and the power switch components Q i1˜i4  are coupled to a driving control circuit (which is not shown in  FIG. 4A ), such as a PWM driving control circuit. On the other hand, the second conversion circuit  402  may be a boost type DC/DC converter consisting of power switch components Q d1˜d2  and diodes D 1˜2 , and the power switch components Q d1˜d2  are coupled to the controller  202  and receive PWM signals therefrom. 
       FIG. 5A  illustrates the electrical energy conversion device  500  according to an exemplary embodiment. The electrical energy conversion device  500  comprises the converter  5001 , controller  202 , first filter  203 , and ripple-compensation unit  508 . The converter  5001  comprises the first conversion circuit  501 , decoupling circuit  502 , and capacitors C d  and C de . 
     In this embodiment, the first conversion circuit  501  is a single phase AC/DC inverter. The DC side of the first conversion circuit  501  is coupled to the second terminal of the decoupling circuit  502 , and the first terminal (DC node  503 ) of the decoupling circuit  502  is coupled to the controller  202 . The controller  202  controls the voltage of the DC node  503  (which is noted as the first voltage V de ) according to the command voltage V 5c , and the command voltage V 5c  is provided by the ripple-compensation unit  508 . The ripple-compensation unit  508  generates a ripple-component current I 5dr  corresponding to the ripple-component power of the power at the AC side of the first conversion circuit  501 , and obtains the first voltage V de  and DC voltage V 5d  through a seventh and eighth sampling circuit (which are not shown in  FIG. 5A ), respectively. The ripple-component current I 5dr  is multiplied by the DC voltage V 5d  through the multiplier  509  to generate the ripple-component power of the power at the DC side of the first conversion circuit  501 , and then the ripple-component power is divided by the first voltage V de  through the divider  510 ; the resulting outcome is sent to the integrator  506  of the first computation device  504  to generate the ripple-component voltage V 5der , and the ripple-component voltage V 5der  is combined with the predetermined command voltage V 5cp  by the adder  507  of the first computation device  504  to generate the command voltage V 5c . The controller  202  controls the first voltage V de  according to the command voltage V 5c  which relates to the ripple-component power, generates a PWM signal, and sends the PWM signal to the control terminal of the decoupling circuit  502  in order to control the output thereof. Based on the operation of the controller  202 , the first voltage V de  will approach the command voltage V 5c , and when the controller  202  provides higher gain performance, the first voltage V de  will approach the command voltage V 5c  more quickly. Based on the embodiment described above, the first voltage V de  contains the components related to the ripple-component power, and therefore makes the electrical energy conversion device  500  have balanced power between the DC side and AC side thereof. In that case, the ripple-component power will be transferred to the side including V de  of the decoupling circuit  502 , and the voltage and current at the DC side of the first conversion circuit  501  will contain a small amount of ripple voltage and current, respectively. Meanwhile, the size of the capacitor C de  of the decoupling circuit  502  can be reduced. 
     In some embodiments, the first conversion circuit  501  may be any type of electrical energy converter performing DC-to-AC or AC-to-DC conversion, and the decoupling circuit  502  may be any type of bidirectional DC/DC converter comprising the boost type, buck type, or isolated type. In some embodiments, the DC current I de  will be sent to the controller  202 . As  FIG. 5B  shows, the first conversion circuit  501  may be a single phase AC/DC inverter consisting of power switch components Q i1˜i4  and diodes D 11˜14 , and the power switch components Q i1˜i4  are coupled to a driving control circuit (which is not shown in  FIG. 5A ), such as a PWM driving control circuit. On the other hand, the decoupling circuit  502  may be a boost type power decoupling circuit consisting of power switch components Q d1˜d2  and diodes D 1˜2 , and the power switch components Q d1˜d2  are coupled to the controller  202  and receive PWM signals therefrom. 
     The ripple-compensation control method provided by the various described embodiments can be applied to a power factor corrector (PFC), an AC/DC unidirectional power inverter, or a combination of a DC/AC unidirectional power inverter, bidirectional AC/DC inverter, and DC/DC power converter, and also can be adopted to a grid-connected type or stand-alone type system. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with the true scope of the disclosure being indicated by the following claims and their equivalents.