Patent Publication Number: US-9843182-B2

Title: Systems and methods for use in identifying and responding to type of grid fault event

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of PCT Patent Application No. PCT/CN2011/081499 filed Oct. 28, 2011, which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates generally to systems and methods for use in controlling a converter coupled between a power generator and an electric grid. 
     Electric grids are known for distribution of electric power. A utility power generator is generally known to provide a substantial amount of power to the electric grid, while independent sources are connected to the electric grid to provide a local grid power and reduced dependence on the utility power generator. 
     Each of the independent sources is connected to the electric grid through a power conditioner and/or a converter to provide consistent and efficient coupling of the independent source to the electric grid. Under certain conditions, the electric grid may experience one or more grid fault events, such as low voltage, high voltage, zero voltage, phase jumping, etc. Often, electric grid operators require that independent sources connected to the electric grid be sufficiently robust to ride through grid fault events. Under such conditions, power conditioners and/or converters may be required to protect the power generator from one or more overvoltage conditions, while providing the ride through functionality. Several known power conditioners and/or converters, for example, include braking resistors to absorb excessive energy to reduce the potential for overvoltage conditions. Other known methods instantaneously turn OFF switching devices within power conditioners and/or converters during a grid fault event, intending to preempt one or more overvoltage conditions, often resulting in a shutdown and/or restart of the power generator. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, a power module for use in controlling a converter coupled between a power generator and an electric grid is provided. The power module includes a converter configured to supply an output from a power generator to an electric grid and a controller coupled to the converter, and configured to disable the converter in response to a grid fault event. The converter is also configured to identify the type of grid fault event after a first predetermined interval from disabling the converter, and to enable the converter when the type of the grid fault event is identified as a low voltage condition. 
     In another aspect, a power system is provided. The power system includes a power generator configured to generate a DC voltage and a power module coupled to the power generator and configured to convert the DC output to an AC output and provide the AC output to an electric grid. The power module includes a converter. The power module is configured to detect a grid fault event based on a parameter associated with the converter, disable the converter in response to the detected grid fault event, identify a type of the grid fault event after a first predetermined interval based on the parameter associated with the converter, and when the type of the grid fault event is identified as a phase jump condition, determine if a phase-lock-loop (PLL) module is locked onto the electric grid after a second predetermined interval. 
     In yet another aspect, a method for use by a power module in controlling a converter coupled between a power generator and an electric grid is provided. The power module includes a converter and a controller coupled to the converter. The method includes detecting a grid fault event as a function of a parameter associated with the electric grid, disabling the converter based on detection of the grid fault event, and identifying, at the controller, the type of the grid fault event after waiting a first predetermined interval. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary power system. 
         FIG. 2  is a circuit diagram of an exemplary power module that may be used with the power system of  FIG. 1 . 
         FIG. 3  is a flow diagram of an exemplary method for use in controlling a converter coupled between a power generator and an electric grid. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The embodiments described herein relate to power systems and methods for use in controlling a converter coupled between a power generator and an electric grid. More particularly, the embodiments described herein facilitate identifying a type of grid fault event and/or recovering a power module from the grid fault event. 
       FIG. 1  illustrates an exemplary power system  100 . In the exemplary embodiment, power system  100  includes an electric grid  102 , multiple power generators  104  coupled to electric grid  102 , and a major power generator  106  coupled to electric grid  102 . Major power generator  106  is configured to provide a relatively major portion of power to electric grid  102 , as compared to each individual power generator  104 . In various embodiments, each power generator  104  may include, without limitation, one or more photovoltaic (PV) arrays, wind turbines, hydroelectric generators, fuel generators, and/or other power generator devices, etc. Further, major power generator  106  may include, for example, a nuclear, coal, or natural gas power generator. It should be appreciated that power system  100  may include a different number and/or configuration of generators in other embodiments. 
     In the exemplary embodiment, power system  100  includes a power module  108  coupling each power generator  104  to electric grid  102 . 
       FIG. 2  illustrates an exemplary power module  108  for use with power system  100 . In the exemplary embodiment, power module  108  includes a converter  110  and a controller  112  coupled to converter  110  to provide control signals to converter  110 . Converter  110  is a direct current (DC) to alternating current (AC) converter, having a number of switching devices. Control signals to one or more of the switching devices are toggled ON or OFF, to enable or disable converter  112 , respectively. In one example, the switching devices include multiple insulated gate bipolar junction transistors (IGBT) configured to provide single or multiple phase outputs from power generator  104  to electric grid  102 . Various other switching devices and/or configurations of switching devices may be used in other converter embodiments. It should be further appreciated that other converters may be used in other embodiments. For example, converter  110  may include a DC-DC converter, an AC-DC converter, and/or an AC-AC converter, etc. 
     As shown in  FIG. 2 , power module  108  further includes a DC-DC boost converter and an energy storage device  114  coupled between converter  110  and boost converter  118 . Specifically, energy storage device  114  is coupled in parallel with an input of converter  110 . While energy storage device  114  is illustrated as a single capacitor, it should be understood that a different number and/or type of energy storage device may be used in other embodiments. Additionally, or alternatively, boost converter  118  may include a buck converter, buck-boost converter or other type of converter in other power module embodiments, potentially depending on the power supplied by power generator  104  and/or the power standard of electric grid  102 . In at least one embodiment, boost converter  118  is omitted. 
     In the exemplary embodiment, during operation, DC power is generated by power generator  104 , which is transmitted through boost converter  118 . Boost converter  118  converts the generated DC voltage from power generator  104  to another DC voltage. The DC voltage from boost converter  118  is supplied to converter  110  and charges energy storage device  114 . Converter  110  converts the DC voltage from boost converter  118  to an AC voltage, which is subsequently filtered and provided to electric grid  102  through a transformer  119 . Further, power module  108  includes circuit breakers  120  and  121  coupled in series between power generator  104  and electric grid  102 . Circuit breaker  120  is configured to de-couple and/or disconnect power generator  104  from power module  108 , and circuit breaker  121  is configured to de-couple and/or disconnect electric grid  102  from power module  108 . 
     In the exemplary embodiment, controller  112  provides control signals to converter  110  to provide a desired output voltage to electric grid  102 , while reacting to and/or riding through one or more grid fault events of electric grid  102 . 
     In the exemplary embodiment, controller  112  includes an event control  122 . As shown in  FIG. 2 , event control  122  is coupled to a plurality of regulators, which control the switching of one or more switching devices included in converter  110 . It should be appreciated that the particular topology of the regulators is merely exemplary and that one or more different topologies may be employed in other power module embodiments. In the exemplary embodiment, controller  112  includes a phase-lock-loop (PLL) module  123 , a DC voltage regulator  124 , a Volt-VAR regulator  126 , current regulators  128  and  130 , and a number of other components. Further description of the functionality of such regulators is described below. 
     Furthermore, in the exemplary embodiment, controller  112  is implemented in software and/or firmware embedded in one or more processing devices. Such processing devices may include, without limitation, a microcontroller, a microprocessor, a programmable gate array, a reduced instruction set circuit (RISC), an application specific integrated circuit (ASIC), etc. Implementations and/or deployment of modules and methods described herein may be efficient and cost effective, and require little or no additional hardware. Further, controller  112  may be programmed for specific applications, such that instructions, predetermined intervals, thresholds, etc. may be programmed and/or stored for particular power generators  104  and/or electric grids  102 . While controller  112  is described herein as implemented in one or more processing devices, it should be appreciated that one or more aspects of controller  112  may be implemented by discrete components, external to one or more processing devices. 
     According to one or more embodiments, technical effects of the methods, systems, and modules described herein include at least one of: (a) detecting a grid fault event as a function of a voltage associated with a converter, (b) disabling the converter based on detection of a grid fault event, and (c) identifying, at a controller, the type of the grid fault event after a first predetermined interval. Furthermore, technical effects of the methods, systems, and modules described herein include at least one of: (a) detecting, by a controller, a grid fault event as a function of a voltage associated with a converter, (b) disabling the converter substantially during the grid fault event, while maintaining coupling between a power generator and an electric grid, and, (c) after the grid fault event, re-enabling the converter to provide an AC voltage to the electric grid. 
       FIG. 3  illustrates an exemplary method for use in controlling converter  110  during one or more grid fault events. Grid fault events include, without limitation, a low voltage condition, a high voltage condition, a phase jump condition, etc. The term “low voltage condition” refers to an event in which the voltage of at least one phase of the electric grid is lower than a nominal voltage of the electric grid (e.g., about 70-85% or nominal, or lower). As such, the term “low voltage condition” is applicable to zero voltage in at least one phase of the electric grid. The term “phase jump condition” refers to an event in which the phase angle of at least one phase of the electric grid diverges, for example, by about 30° or more from a nominal phase angle of the one or more phases of the electric grid. The term “high voltage condition” refers to an event in which the voltage of at least one phase of the electric grid is substantially exceeds than a nominal voltage of the electric grid. Such conditions may occur during a startup of the converter, during a shutdown of the converter, and/or during any other suitable event. The events may result from, for example, significant switching activity on electric grid  102 , closing of one or more capacitive banks, etc. Grid fault events may cause energy storage device  114  to experience an overvoltage condition, potentially causing damage to energy storage device  114  and/or associated components of power module  108 . 
     In response to one or more grid fault events, controller  112  may trip, causing power module  108  and/or power generator  104  to be shutdown. As used herein, the term “trip” refers to one or more conditions in which power generator  104  is disconnected and/or decoupled from electric grid  102  when the voltage at the energy storage device  114  exceeds a predetermined threshold. Trips may include hard trips or soft trips. More specifically, power module  108  invokes a hard trip when the voltage at the energy storage device  114  exceeds, for example, about 1050 to about 1100 VDC, and invokes a soft trip when the voltage exceeds, for example, about 950 VDC. When controller  112  trips, controller  112  disables converter  110  and boost converter  118 , and then disconnects and/or decouples power generator  104  from electric grid  102  (e.g., opening circuit breakers  120  and  121 , etc.). Subsequently, controller  112  discharges energy storage device  114  to below a threshold level, such as, for example, about 50 VDC. Discharging of energy storage device  114  often occurs over a duration of about 3 minutes to about 25 minutes or more, depending on the voltage across energy storage device  114  and/or the manner in which energy storage device  114  is discharged. During a trip, power generator  104  is unable provide power to electric grid  102 . 
     When the trip is a hard trip, power module  108  remains shutdown until service is provided based on the assumption that the excessive voltage caused component damage. Conversely, when the trip is a soft trip, controller  112  initiates restart of power modules  108  after a wait interval, such as, for example, about 2.0 to about 8.0 minutes, about 3.0 minutes to about 4.0 minutes, or another suitable interval, etc. During restart, controller  112  couples and/or connects power module  108  to electric grid  102  (e.g., via circuit breaker  121 ), and enables the operation of the regulators and PLL module  123  included therein. Subsequently, power generator  104  is connected and/or coupled to power modules  108  (e.g., via circuit breaker  120 ), and boost converter  118  is initialized. Boost converter  118  is stepped upward a nominal operating voltage, with converter  110  reacting to each of the steps from initialization until the nominal operating voltage. The restart permits power generator  104  to eventually provide power to electric grid  102 , but only after a significant trip/restart interval, often in excess of about 30-40 minutes. In response to grid fault events, conventional power conditioners are known to trip in some instance and maintain operation in other instances. When conventional power conditioners maintain operation, a converter included therein remains enabled which may permit over voltage conditions at a DC bus and/or reverse current into the power conditioners. Such condition stress and/or damage associated components, thereby diminishing the lifetime of the components. 
     Systems and methods described herein provide one or more processes for avoiding a trip and/or restart of power module  108 , while inhibiting overvoltage conditions at and/or reverse power flow to energy storage device  114 . More specifically, in one exemplary embodiment, controller  112  quickly detects a grid fault event, identifies a type of grid fault event, and responds accordingly. In doing so, controller  112  inhibits substantial reverse current flow from electric grid  102  to energy storages device  114  and/or overvoltage conditions at energy storage device  114 , while avoiding shutdown and/or restart. 
     In the exemplary embodiment, controller  112  monitors a voltage associated with converter  110  to detect  202  grid fault events. As shown in  FIG. 2 , event control  122  measures the voltage associated with electric grid  102  directly at an output of converter  110 , as compared to monitoring the voltage at PLL module  123 . In this manner, event control  122  is able to substantially instantaneously detect one or more grid fault events, by comparing the measured voltage to one or more previously measured voltages. In contrast, known converters employ PLL feedback loops to detect grid fault events. The PLL feedback loops, however, are too slow to accurately track phase angle when electric grid  102  is attempting to clear the grid fault event. Inability to accurately track phase angles often results in reverse current conditions. By measuring the voltage associated with electric grid  102  directly, controller  112  is able to respond to grid fault events more rapidly to disable converter  110 , thereby reducing the potential for reverse current conditions and/or stress on energy storage device  114 . It should be appreciated that a voltage associated with electric grid  102  may be measured at one or more other locations within power module  108  and/or at electric grid  102  in other embodiments. 
     Detection of one or more grid fault events may be further based on different thresholds related to the voltage associated with electric grid  102 . In the embodiment illustrated in  FIG. 2 , controller  112  detects a grid fault event when the magnitude of the voltage is about 30-50% below a nominal value and/or when the phase of the voltage diverges by about 20-30° from a nominal value. It should be understood that one or more different thresholds for detecting grid fault events may be employed in other embodiments. 
     When controller  112  detects the occurrence of a grid fault event, controller  112  disables  204  converter  110 . Specifically, in the exemplary embodiment, controller  112  disables each regulator of controller  112 , thereby holding switching devices of converter  110  open (i.e., gating OFF converter  110 ). When converter  110  is disabled, no output is provided from power generator  104  to electric grid  102 . Power generator  104  and electric grid  102 , however, remain coupled to one another through power module  108 , thereby avoiding a trip. After disabling converter  110 , controller  112  waits  206  for an initial predetermined interval. In the exemplary embodiment, the initial predetermined interval is between about 2.0 milliseconds to about 20.0 milliseconds, and/or about 3.0 milliseconds to about 5.0 milliseconds. In other embodiments, the initial predetermined intervals may be of different durations, including, for example, about 1.0 millisecond to about 30.0 milliseconds, or more. During the initial predetermined interval, converter  110  remains disabled. It should be appreciated that while method  200  includes waiting steps, controller  112  may conduct one or more other processes, related or unrelated to control of converter  110 , while performing a waiting step. More generally, waiting during an interval used herein should not be understood to limit controller  112  to an idle state. 
     After the initial predetermined interval, controller  112  identifies  208  the type of grid fault event based on, for example, the voltage associated with electric grid  102 . In the exemplary embodiment, because converter  110  is disabled during the initial predetermined interval, the voltage measured at the output of converter  110 , for example, is substantially dependent on voltage from electric grid  102 , rather than converter  110 . As such, controller  112  is permitted to more accurately and/or efficiently perceive the grid fault event originating from electric grid  102 , due to the reduced effect of converter  110  on the measured voltage. 
     In the exemplary embodiment, controller  112  determines, based on the magnitude and/or phase of the voltage, whether the grid fault event is the result of a low voltage condition or a phase jump condition, as described above. Generally, to identify  208  the grid fault event, controller  112  evaluates the magnitude of the voltage to determine if the voltage is still low after the initial predetermined interval, or if the voltage has increased since detection of the grid fault event at  202 . If the voltage remains below the nominal value, controller  112  determines the type of grid fault event is a low voltage condition. Conversely, if the voltage is greater than the previously detected voltage, but the phase is different, controller  112  determines the type of grid fault event as a phase jump condition. One or more other conditions may be indicated by the magnitude and/or phase of the voltage associated with electric grid  102 , such as a high voltage condition in other embodiments. In at least one embodiment, once identified, the types of the grid fault events are stored in controller  112  for one or more diagnostic purposes. 
     Further, by identifying the type of grid fault event, controller  112  is able to control converter  110  based on the particular type of grid fault event. In various embodiments, rapid identification of the type of grid fault event permits power modules  108  to respond more quickly, potentially intervening prior to reverse current conditions and/or overvoltage conditions at energy storage device  114 . In the example of  FIG. 3 , after the initial predetermined interval (e.g., about 4.0 milliseconds), the type of grid fault event is identified, and controller  112  is able to respond to the grid fault event within about 5.0 milliseconds to about 30 milliseconds, or about 10.0 to about 20.0 milliseconds, of the occurrence of the grid fault event. 
     By responding in this manner, controller  112  intervenes before recoverable grid fault events cause a reverse current and/or overvoltage condition, leading to a trip of power module  108 . Accordingly, power modules  108  described herein are configured to trip to protect power module  108 , but ride through an increased number of grid fault events, as compared to known power converters which often rely on slower PLL feedback loops. By reducing the number of trip conditions, controller  112  minimizes shutdown and/or restart of power system  100  and extends the lifetime of components therein, such as energy storage device  114 . 
     In the exemplary embodiment, when controller  112  detects low voltage conditions, controller  112  re-enables  210  converter  110 . More specifically, control signals are provided to converter  110  to output  212  reactive current from power generator  104  to electric grid  102 . The reactive current is delivered from power generator  104  during the grid fault event. In this manner, power module  108  is configured to remain coupled and/or connected to electric grid  102 , while riding through one or more low voltage conditions. Such ride through may be required by the operator of electric grid  102 . From outputting  212  reactive current, controller  112  monitors the voltage associated with converter  110  to determine  214  when the grid fault event is ended. After the grid fault event is ended, method  200  includes disabling  216  converter  110  prior to recovering power module  108 . 
     Conversely, if the type of grid fault event is identified as a phase jump condition, method  200  including waiting  218  for an additional predetermined interval. In the exemplary embodiment, the additional predetermined interval is between about 5 milliseconds and about 120 milliseconds (or less than approximately 10 cycles, etc.), and more specifically, between about 10 milliseconds and about 20 milliseconds. In other embodiments, one or more different durations of the additional predetermined interval may be used. After the additional predetermined interval, controller  112  proceeds to recover power module  108 . 
     Subsequently, in the exemplary embodiment, controller  112  re-enables converter  110  to recover power module  108  to normal operation. Controller  112  avoids one or more overvoltage conditions at energy storage device  114 , which permits controller  112  to maintain coupling between power generator  104  and electric grid  102 . The maintained coupling permits power modules  108  to recover, rather than restart as described above. In this manner, controller  112  is able to re-enable converter  110  and provide an output from power generator  104  to electric grid  102  more rapidly than if a shutdown and/or a restart was required. 
     In the exemplary embodiment, controller  112  employs PLL module  123  to lock onto the voltage associated with electric grid  102 . Specifically, in the exemplary embodiment, method  200  includes determining  220  whether PLL module  123  is locked onto the voltage associated with electric grid  102 . When locked, PLL module  123  provides a PLL locked indication to event control  122 . Without such an indication, method  200  includes waiting  222  for a short predetermined interval before controller  112  determines  220  again whether PLL module  123  is locked onto the voltage associated with electric grid  102 . In one example, the short predetermined interval includes about 5 milliseconds to about 20 milliseconds, or about 8 milliseconds to about 15, or about 10 milliseconds, but may be different in other controller embodiments. Further, in the exemplary embodiment, method  200  alternatively proceeds between determining  220  whether PLL module is locked and waiting  222  for a PLL locked indication, or a timeout interval expires (not shown). The timeout interval is in the range between about 100 milliseconds and about 1.0 second, or about 50 milliseconds and about 2.0 seconds, and may be longer or shorter in still other controller embodiments. When the timeout interval expires, power module  108  and/or converter  110  trip, as described above. 
     In the exemplary embodiment, when PLL module  123  locks on after a grid fault event, at least one parameter associated with one or more regulators of controller  112  is adjusted to permit converter  110  to recover to normal operation. More generally, after a grid fault event, in which converter  110  is disabled, the voltage at energy storage device  114  may diverge substantially from a nominal value during the grid fault event. Because the voltage across energy storage device  114  controls voltage regulator  124 , when converter  110  is enabled, the voltage may immediately demand a substantial power output from power generator  104 . Such a demand may cause known power conditioners and/or converters to detect a false grid fault event. Detection of the subsequent false grid fault event may occur repeatedly, effectively preventing known power conditioners and/or converters from recovering from the initial grid fault event. In contrast, after the grid fault event has ended, controller  112  adjusts the parameter associated with the regulator to prevent one or more initial demands from causing detection of a false grid fault event. 
     In the exemplary embodiment, method  200  proceeds to adjusting  223  at least one parameter associated with at least one of the regulators of controller  112 . Specifically, in the exemplary embodiment, method  200  proceeds to adjust  224  a correction defined by at least one of a Vdc reference and a Vdc feedback associated with regulator  124 . In this particular exemplary embodiment, the Vdc reference is adjusted to be substantially equal to the Vdc feedback (VdcFbk) from energy storage device  114 . In this manner, the correction defined by Vdc reference and Vdc feedback (e.g., a difference between Vdc reference and Vdc feedback), to which voltage regulator  124  responds, is substantially equal to zero. Accordingly, a demand provided from voltage regulator  124  may be insubstantial, as compared to a demand without such an adjustment. In another example, an adjustment may include reducing the correction by summing the Vdc reference, the Vdc feedback and another signal (substantially equal to and opposite of the sum of the Vdc reference and the Vdc feedback) to reduce the total of the three to substantially equal to zero. It should be appreciated that various other adjustments to corrections and/or parameters associated with voltage regulator  124  and/or other regulators of controller  112  may be employed to provide a recovery to converter  110 . 
     Further, before, after or simultaneously with adjusting Vdc reference, a parameter associated with current regulators  128  and  130  may be adjusted. In the exemplary embodiment, method  200  proceeds to reset  226  at least one of current regulators  128  and  130  to make such an adjustment. More specifically, one or more current demands utilized by current regulators  128  and  130  are reset, i.e., zeroed out, prior to enabling converter  110 . In one example, current regulators  128  and  130  include integrators (not shown), which determine an integration of current demand over time. Accordingly, the integrators rely on one or more prior current demands. In the exemplary embodiment, controller  112  sets references of current regulators  128  and  130  substantially equal to the prior current demands (stored during operation of current regulators  128  and  130  prior to the grid fault event). As a result, the prior current demands are cancelled out by the new reference, thereby inhibiting current regulators  128  and  130  from acting on current demands from prior to the grid fault event and overshooting a suitable output from current regulators  128  and  130 . In several embodiments, one or more parameters associated with current regulators  128  and  130  may be adjusted, after one or more grid fault events, while parameters associated with other regulators within controller  112  remain unadjusted. Further, it should be appreciated that in various other embodiments, one or more parameters associated with one or more different regulators may be adjusted consistent to the description herein. 
     Moreover, in the exemplary embodiment, method  200  proceeds to eliminate  228  the adjustment over a recovery interval and re-enable  230  converter  110  prior to or after expiration of the recovery interval. The recovery interval provides an interval for returning the adjusted parameter to a value indicated by normal operation of converter  110  and/or the voltage associated with electric grid  102  and/or converter  110 . Specifically, in the example above, the adjusted Vdc reference value is permitted to return to a nominal value, over a recovery interval, such as, for example, about 20 milliseconds, about 100 milliseconds, etc. As such, in the exemplary embodiment, controller  112  provides a recovery of converter  110  over time, thereby inhibiting substantial demands after a grid fault event and/or detection of false grid fault events. The recovery interval may be included, without limitation, in the range between about 10 milliseconds and about 1.0 seconds or more, potentially based on topology of controller  112  and/or the bandwidth of one or more regulators included therein. 
     By responding according to exemplary method  200 , in at least one exemplary embodiment, power module  108  is capable of recovering from a grid fault event within about 2.0 seconds, about 5.0 seconds, about 10.0 seconds, or other minor interval, as compared to intervals, often in excess of about 30 to about 40 minutes, involved in restarting power module  108  from a trip condition. In this manner, power module  108  is permitted to deliver more power to electric grid  102 , while providing reduced down time and/or stress on one or more components included therein (e.g., energy storage device  114 , etc.). 
     While the systems and methods herein are described with reference to power generators and electric grids, it should be appreciated that such systems and methods may be employed in other applications, such as, for example, motor drive systems, various other PWM converter applications, other power applications, etc. 
     One more aspects of methods and/or systems described herein may be employed in various combinations. In one or more example systems, the power module is further configured to enable switching of the converter, when the type of grid fault is identified as a low voltage condition, to supply reactive current to the electric grid. Another example system includes a power module including a DC-DC converter coupled between the power generator and the converter. In such an example, the DC-DC converter is configured to boost the DC voltage supplied from the power generator. 
     In various example methods, the parameter associated with the electric grid includes a voltage associated with the converter. In some example methods, identifying the type of grid fault event includes measuring a magnitude of the voltage associated with the converter. One or more example methods may further include enabling the converter, when the identified type of the grid fault event is a low voltage condition, to supply reactive power to the electric grid. Additionally, or alternately, example methods may include determining if a PLL module of the power module is locked on the voltage associated with the converter after a second predetermined interval, when the identified type of grid fault event is a phase jump condition. Yet another example method may include tripping the power module when the PLL module does not locked onto the voltage associated with the converter after at least about 1.0 second from identifying the type of the grid fault event. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 
     
       
         
           
               
             
               
                   
               
               
                 PARTS LIST 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 100 
                 Power system 
               
               
                 102 
                 Electric grid 
               
               
                 104 
                 Power generator 
               
               
                 106 
                 Major power generator 
               
               
                 108 
                 Power module 
               
               
                 110 
                 Converter 
               
               
                 112 
                 Controller 
               
               
                 114 
                 Energy storage device 
               
               
                 118 
                 Boost converter 
               
               
                 119 
                 Transformer 
               
               
                 120 
                 Circuit breaker 
               
               
                 121 
                 Circuit breaker 
               
               
                 122 
                 Event control 
               
               
                 123 
                 Phase-lock-loop (PLL) module 
               
               
                 124 
                 Voltage regulator 
               
               
                 126 
                 Volt-VAR regulator 
               
               
                 128 
                 Current regulator 
               
               
                 130 
                 Current regulator 
               
               
                 200 
                 Method 
               
               
                 202 
                 Detecting 
               
               
                 204 
                 Disabling 
               
               
                 206 
                 Waiting 
               
               
                 208 
                 Grid Fault Type 
               
               
                 210 
                 Re-enabling 
               
               
                 212 
                 Outputting 
               
               
                 214 
                 Grid Fault Ends 
               
               
                 216 
                 Disabling 
               
               
                 218 
                 Waiting 
               
               
                 220 
                 PLL Module Locked 
               
               
                 222 
                 Waiting 
               
               
                 223 
                 Adjusting 
               
               
                 224 
                 Adjusting 
               
               
                 226 
                 Resetting 
               
               
                 228 
                 Eliminating 
               
               
                 230 
                 Re-enabling