Patent Publication Number: US-2023137678-A1

Title: Adaptive dc/dc pwm control

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 63/273,506, filed Oct. 29, 2021, entitled ADAPTIVE DC/DC PWM CONTROL, naming Livio Alessandro Tilotta and Stefano Pecorari as inventors, which is incorporated herein by reference in the entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to DC/DC converters and, more particularly, to adaptive PWM control of DC/DC converters 
     BACKGROUND 
     DC/DC converters are widely used to convert and/or regulate an input voltage of a direct current (DC) source to a desired output voltage. Various architectures are possible such as, but not limited to, a buck converter (e.g., a step-down converter) to reduce the input voltage to a lower output voltage, a boost converter (e.g., a step-up converter) to increase the input voltage to a higher output voltage, or a buck-boost converter to provide a regulated voltage in response to a range of input voltages. However, existing DC/DC converters fail to adequately provide both rapid responsivity and energy-efficient operation under diverse operating conditions such as, but not limited to, dynamic grid support (DGS) applications. There is therefore a need to develop systems and methods for advanced DC/DC conversion. 
     SUMMARY 
     An adaptive direct current (DC) conversion system is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the system includes a multi-mode DC converter circuit including two or more power switches, where the multi-mode DC converter circuit is operable in two or more pulse width modulation (PWM) modes based on two or more PWM signal sets provided to the two or more power switches. In another illustrative embodiment, the system includes a PWM controller, where the PWM controller controls which of the two or more PWM modes the multi-mode DC converter circuit operates in by providing the multi-mode DC converter circuit with the associated one of the two or more PWM signal sets. 
     An uninterruptible power supply (UPS) is disclosed in accordance with one or more illustrative embodiments of the present disclosure. In one illustrative embodiment, the UPS includes a rectifier to rectify input power from an electrical grid. In another illustrative embodiment, the UPS includes a battery. In another illustrative embodiment, the UPS includes a DC conversion system coupled to the battery. In another illustrative embodiment, the DC conversion system includes a multi-mode DC converter circuit including two or more power switches, where the multi-mode DC converter circuit is operable in two or more PWM modes based on two or more PWM signal sets provided to the two or more power switches. In another illustrative embodiment, the DC conversion system includes a PWM controller, where the PWM controller controls which of the two or more PWM modes the multi-mode DC converter circuit operates in by providing the multi-mode DC converter circuit with the associated one of the two or more PWM signal sets. In another illustrative embodiment, the UPS includes an inverter to generate an alternating current (AC) power output from at least one of the rectifier or the DC conversion system. 
     In some embodiments, the UPS with the adaptive DC conversion system is suitable for selective operation in either a standard UPS state or a dynamic grid support (DGS) state. For example, the UPS may utilize any of a number of complementary PWM signal sets to modulate at least one pair of power switches in the multi-mode DC converter circuit with a complementary pattern to provide high responsivity. In this way, any of a number of DGS functions may be implemented using complementary PWM signal sets. By way of another example, the UPS may utilize a single PWM signal set to modulate a single power switch in the multi-mode DC converter circuit to provide power-efficient operation in the standard UPS state. In this way, the UPS may provide highly responsive DGS operations when necessary and power efficient operation when DGS operations are not necessary. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not necessarily restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The numerous advantages of the disclosure may be better understood by those skilled in the art by reference to the accompanying figures. 
         FIG.  1 A  is a block-level diagram of an adaptive DC conversion system, in accordance with one or more embodiments of the present disclosure. 
         FIG.  1 B  is a conceptual schematic view of a multi-mode DC converter circuit, in accordance with one or more embodiments of the present disclosure. 
         FIG.  1 C  is a conceptual view of a PWM signal set for a pair of power switches providing complementary PWM mode operation, in accordance with one or more embodiments of the present disclosure. 
         FIG.  1 D  is a conceptual view of inductor current over time for different output current levels associated with complementary PWM mode operation, in accordance with one or more embodiments of the present disclosure. 
         FIG.  1 E  is a conceptual view of a PWM signal set providing modulation of a single power switch in a single PWM mode, in accordance with one or more embodiments of the present disclosure. 
         FIG.  1 F  is a conceptual view of inductor current over time for different output current levels associated with single PWM mode operation, in accordance with one or more embodiments of the present disclosure. 
         FIG.  2 A  illustrates a standard UPS operational mode, in accordance with one or more embodiments of the present disclosure. 
         FIG.  2 B  illustrates a full discharge mode, in accordance with one or more embodiments of the present disclosure. 
         FIG.  2 C  illustrates a partial discharge mode, in accordance with one or more embodiments of the present disclosure. 
         FIG.  2 D  illustrates a recharge mode, in accordance with one or more embodiments of the present disclosure. 
         FIG.  3    is a flow diagram illustrating dynamic operation of a UPS with an adaptive DC conversion system in multiple operational modes, in accordance with one or more embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the subject matter disclosed, which is illustrated in the accompanying drawings. The present disclosure has been particularly shown and described with respect to certain embodiments and specific features thereof. The embodiments set forth herein are taken to be illustrative rather than limiting. It should be readily apparent to those of ordinary skill in the art that various changes and modifications in form and detail may be made without departing from the spirit and scope of the disclosure. 
     Embodiments of the present disclosure are directed to systems and methods for adaptive pulse width modulation (PWM) mode control of a switched-mode DC/DC converter, herein referred to simply as a direct current (DC) converter. 
     Switched-mode DC converters are a class of DC converters that utilize one or more power switching elements such as, but not limited to, transistors to selectively direct energy from an input source to energy storage components (e.g., inductors, capacitors, or the like) in order to provide a regulated output voltage. Switched-mode DC converters typically include a PWM controller to provide PWM signals that drive the power switching elements. In this way, various aspects of the PWM signals such as, but not limited to, the duty cycle may be used to control or tune the operation of the DC converter. 
     Switched-mode DC converters may be flexibly designed to provide varied functionality based on the configurations of the power switches and the energy storage components. For example, switched-mode DC converters may be implemented in a variety of voltage regulation functions such as buck converters, boost converters, or buck-boost converters. By way of another example, switched-mode DC converters may provide for both uni-directional and bi-directional power flow operations. 
     It is contemplated herein that different designs or operational modes of a DC converter may provide different performance tradeoffs. For example, the operation of the power switches may result in various power losses such as, but not limited to, switching losses, conduction losses, or inductor losses. As a result, increasing a number of operational power switches may increase the overall system losses. However, designs incorporating multiple switches may provide desirable benefits such as increased temporal responsivity for high-speed operation. It may thus be the case that different designs or operational modes may be suitable for different circumstances. 
     Embodiments of the present disclosure are directed to dynamic control of a DC converter for operation in two or more PWM modes (e.g., two or more configurations of power switches). In this way, the performance of the DC converter may be dynamically tailored for different operating conditions during run-time (e.g., on the fly). In some embodiments, an adaptive DC converter system includes a multi-mode DC converter circuit capable of operation in two or more PWM modes and an adaptive PWM controller to provide PWM signal sets to the power switches of the multi-mode DC converter circuit associated with the two or more PWM modes. For example, an adaptive DC converter system may operate using a single PWM mode in which a single power switch is operational. Such a single PWM mode may be suitable for, but is not limited to, operating inductors of the DC converter in a discontinuous conduction mode (DCM), which may provide relatively low power losses, particularly when the converted current is low. By way of another example, an adaptive DC converter system may operate using a complementary PWM mode in which one or more pairs of power switches are operated with complementary PWM signals. Such a complementary PWM mode may be suitable for, but is not limited to, operating inductors of the DC converter in a continuous conduction mode (CCM), which may provide relatively fast responsivity (e.g., fast dynamic responses) but have relatively higher losses than a single PWM mode when the converter current is low. In this way, an adaptive DC converter system may selectively operate in a complementary PWM mode when high responsivity is required and operate in a single PWM mode when high responsivity is not required and/or when power efficient operation is desired. 
     It is further contemplated herein that an adaptive DC converter system as disclosed herein may provide PWM modes associated with any voltage regulation scheme including, but not limited to, a buck converter, a boost converter, a buck-boost converter, or a dynamically-controllable combination thereof. 
     Some embodiments of the present disclosure are directed to an uninterruptible power supply (UPS) with dynamic grid support (DGS) that includes an adaptive DC converter system. It is contemplated herein that DGS features may place significant demands on a UPS such as, but not limited to, a requirement that the battery converter including charger and booster modes must track power level references that vary relatively quickly (e.g., on the order of 10-100 ms in some applications). A DC converter circuit may thus require a configuration with multiple power switches to provide the necessary high-speed current loop performance. For instance, high-speed current loop performance may be obtained using a complementary PWM mode configuration with one or more pairs of power switches that are driven by complementary PWM signals (e.g., PWM signals in a complementary pattern) to provide CCM operation. 
     However, it is further contemplated herein that it may not be desirable for a UPS to operate in a complementary PWM mode at all times. For example, when the battery is near full charge, the load on the DC converter may be relatively low such that the current and the regulated power levels are also low. Under these conditions, a complementary PWM mode inducing CCM operation may result in unnecessary power losses (e.g., switching losses, conduction losses, inductor losses, or the like). 
     In some embodiments, a UPS with an adaptive DC converter system may selectively operate in either a complementary PWM mode providing high-speed current loop performance (e.g., for DGS operation) or a single PWM mode when such high-speed current loop performance is not required and/or at low load levels. In this way, the operational mode of the UPS and the associated performance tradeoffs may be dynamically adjusted based on the operating conditions. In particular, it is contemplated herein that a significant fraction of the total operating time of a UPS may correspond to low load conditions and/or times when high responsivity for DGS operation is not required. As a result, dynamically switching to a single PWM mode may provide substantial power savings while retaining the ability to provide dynamic DGS functionality when needed. 
     However, it is to be understood that an adaptive DC converter system is not limited to UPS applications and that descriptions of specific embodiments of a UPS with an adaptive DC converter system are merely illustrative and should not be interpreted as limiting. 
     Referring now to  FIGS.  1 A- 3   , systems and methods for adaptive DC conversion are described in greater detail in accordance with one or more embodiments of the present disclosure. 
       FIG.  1 A  is a block-level diagram of an adaptive DC conversion system  100 , in accordance with one or more embodiments of the present disclosure. In some embodiments, the adaptive DC conversion system  100  includes a multi-mode DC converter circuit  102  capable of operating in two or more PWM modes and an adaptive PWM controller  104  to provide PWM signal sets  106  to the multi-mode DC converter circuit  102  associated with the two or more PWM modes. 
     The multi-mode DC converter circuit  102  may include any type of switch-mode DC converter known in the art with two or more power switches  108  that accepts PWM signal sets  106  and may be configurable to operate in different modes based at least in part on the received PWM signal sets  106 . In some embodiments, the multi-mode DC converter circuit  102  is a non-isolating switch-mode DC converter. For example, the multi-mode DC converter circuit  102  may include a buck converter, a boost converter, a buck-boost converter, or a combination thereof that is configurable based on the PWM signal sets  106 . Further, the multi-mode DC converter circuit  102  may operate in a uni-directional power flow mode or a bi-directional power flow mode. The multi-mode DC converter circuit  102  may further include various additional energy storage and/or regulation components such as, but not limited to, inductors  110  and capacitors  112 . 
       FIG.  1 B  is a conceptual schematic view of a multi-mode DC converter circuit  102  in accordance with one or more embodiments of the present disclosure. In particular,  FIG.  1 B  illustrates a buck-booster DC converter circuit including two power switches  108  along with an inductor  110  and a capacitor  112  for energy storage and power regulation.  FIG.  1 B  further illustrates a battery  114  connected to the multi-mode DC converter circuit  102 , which may be suitable for, but is not limited to, UPS applications. The performance and operation of the multi-mode DC converter circuit  102  may be tailored based on PWM signal sets  106  applied to the power switches  108 . 
     Referring now to  FIGS.  1 C- 1 F , various PWM modes of the multi-mode DC converter circuit  102  are described in greater detail, in accordance with one or more embodiments of the present disclosure. 
       FIG.  1 C  is a conceptual view of a PWM signal set  106  for a pair of power switches  108  (e.g., PWM A and PWM B) providing complementary PWM mode operation, in accordance with one or more embodiments of the present disclosure. In particular,  FIG.  1 C  illustrates a configuration in which the complementary PWM A and PWM B signals are generated according to a control signal  116 , where the duty cycles are further controlled by a modulation index level  118  (e.g., a mod index level  118 ) applied to the control signal  116 . Further, a complementary PWM signal set  106  need not be strictly complementary. Rather, as illustrated in  FIG.  1 C , dead time  120  or other delays may be introduced between the switching times of the individual PWM signals. 
       FIG.  1 D  is a conceptual view of inductor  110  current over time for different output current levels associated with complementary PWM mode operation, in accordance with one or more embodiments of the present disclosure. In particular,  FIG.  1 D  illustrates CCM operation both at high and low output current levels. For example, a high current level may be a current sufficiently high that the current in the inductor  110  does not change sign during a PWM period, whereas a low current level may be a current sufficiently low that the current in the inductor  110  does change sign during a PWM period. As a result, various power losses associated with CCM such as, but not limited to, switching losses, conduction losses, and inductor  110  losses may be present regardless of the output current levels. 
       FIG.  1 E  is a conceptual view of a PWM signal set  106  providing modulation of a single power switch  108  in a single PWM mode, in accordance with one or more embodiments of the present disclosure. Similar to the complementary PWM signal mode illustrated in  FIG.  1 C , the single modulated PWM signal is similarly controlled by a control signal  116  and the duty cycle depends on the modulation index level  118 . 
       FIG.  1 F  is a conceptual view of inductor  110  current over time for different output current levels associated with single PWM mode operation, in accordance with one or more embodiments of the present disclosure. In particular,  FIG.  1 F  illustrates CCM operation at high output current levels and DCM operation at low output current levels. For example, a high current level may be a current sufficiently high that the current in the inductor  110  does not change sign during a PWM period, whereas a low current level may be a current sufficiently low that the current in the inductor  110  reaches and stays at zero for a portion of a PWM period. As a result, various power losses associated with CCM such as, but not limited to, switching losses, conduction losses, and inductor  110  losses may be mitigated by operation in the single PWM operation when the output current is low such as, but not limited to, when the battery  114  is near full charge. 
     It is to be understood that  FIGS.  1 B- 1 F  and the associated descriptions are provided solely for illustrative purposes and should not be interpreted as limiting. For example, the multi-mode DC converter circuit  102  may have any suitable design or number of the power switches  108  and energy storage elements (e.g., inductors  110 , capacitors  112 , or the like). In this way, the design of the multi-mode DC converter circuit  102  is not limited by the depiction in  FIG.  1 B . As another example, the multi-mode DC converter circuit  102  may be operational in any number of PWM modes based on different PWM signal sets  106  applied to the power switches  108 . In this way, the multi-mode DC converter circuit  102  is not limited to operation in the PWM modes and associated PWM signal sets  106  depicted in  FIGS.  1 C- 1 F . 
     Referring again to  FIG.  1 A , the adaptive PWM controller  104  is described in greater detail in accordance with one or more embodiments of the present disclosure. The adaptive PWM controller  104  may include any type of PWM controller known in the art suitable for providing PWM signal sets  106  associated with two or more PWM modes of the multi-mode DC converter circuit  102 . 
     In some embodiments, the adaptive PWM controller  104  includes one or more processors  122  configured to execute program instructions maintained on memory  124  (e.g., a memory medium). In this regard, the one or more processors  122  may execute any of the various process steps described throughout the present disclosure. The one or more processors  122  of the adaptive PWM controller  104  may include any processor or processing element known in the art. For the purposes of the present disclosure, the term “processor” or “processing element” may be broadly defined to encompass any device having one or more processing or logic elements such as, but not limited to, one or more digital signal processors (DSPs), one or more field-programmable gate arrays (FPGAs), one or more application specific integrated circuit (ASIC) devices, or one or more micro-processor devices. In this sense, the one or more processors  122  may include any device configured to execute algorithms and/or instructions. 
     The memory  124  may include any storage medium known in the art suitable for storing program instructions executable by the associated one or more processors  122 . 
     For example, the memory  124  may include a non-transitory memory medium. By way of another example, the memory  124  may include, but is not limited to, a read-only memory (ROM), a random-access memory (RAM), a magnetic or optical memory device (e.g., disk), a magnetic tape, a solid-state drive, or the like. It is further noted that the memory  124  may be, but is not required to be, housed in a common controller housing with the one or more processors  122 . In some embodiments, the memory  124  may be located remotely with respect to the physical location of the one or more processors  122 , additional portions of the adaptive PWM controller  104 , and/or components of the adaptive DC conversion system  100 . For instance, the one or more processors  122  of the adaptive PWM controller  104  may access a remote memory  124  (e.g., a server), accessible through a network (e.g., internet, intranet, or the like). Moreover, the steps described throughout the present disclosure may be carried out by a single adaptive PWM controller  104  or, alternatively, multiple adaptive PWM controllers  104 . In this way, references to specific hardware configurations herein are solely provided for illustrative purposes and should not be interpreted as limiting. 
     The adaptive PWM controller  104  may select and provide PWM signal sets  106  to the multi-mode DC converter circuit  102  for operation of the multi-mode DC converter circuit  102  in any of various PWM modes using any of a variety of techniques. In some embodiments, the adaptive PWM controller  104  receives a mode selection request that indicates a desired PWM mode. This mode selection request may include commands, triggers, or any other suitable control signals from an external source. The adaptive PWM controller  104  may then provide associated PWM signal sets  106  to the multi-mode DC converter circuit  102  circuit for operation in the desired mode. For example, the external source providing control signals relevant to the PWM mode may include a user input source. As another example, the external source providing control signals relevant to the PWM mode may include an external controller such as, but not limited to, a plant or grid controller. In some embodiments, the desired PWM mode is determined by monitoring circuitry  126 , which may dynamically select the desired PWM mode based on present, expected, or projected operating conditions. The monitoring circuitry  126  may include any type or combination of components suitable for monitoring at least one of currents and/or voltages in the multi-mode DC converter circuit  102  and/or external components (e.g., one or more current monitors, one or more voltage monitors, one or more power monitors, or the like). For example, in the context of a UPS, the monitoring circuitry  126  may monitor aspects of a battery, grid input power, one or more loads connected to the UPS, or the like. 
     As an illustration in the context of a UPS with an adaptive PWM controller  104 , the monitoring circuitry  126  may dynamically select the desired PWM mode for any given time based on grid needs and/or an analysis of grid parameters. Further, the monitoring circuitry  126  may be provided as a component of the adaptive DC conversion system  100  (e.g., as illustrated in  FIG.  1   ), as a component of the adaptive PWM controller  104 , or as a component external to the adaptive DC conversion system  100 . 
     Referring now to  FIGS.  2 A- 2 D , a UPS  202  providing DGS features that includes an adaptive DC conversion system  100  is described in accordance with one or more embodiments of the present disclosure. It is to be understood, however, that an adaptive DC conversion system  100  as disclosed herein is not limited to UPS systems, but may rather be implemented within any application or system utilizing a switched-mode DC converter. In this way, the descriptions of the adaptive DC conversion system  100  within the context of the UPS  202  are illustrative rather than limiting. 
     It is contemplated herein that a UPS  202  providing DGS features may operate with a primary mission of protecting critical loads and a secondary mission of providing grid services. For example, the primary mission of protecting critical loads may include, but is not limited to, providing high-quality, mission-critical power to loads on an output side of the UPS. By way of another example, the secondary mission of providing grid services may include providing various support to the grid such as, but not limited to, frequency regulation, voltage regulation, grid capacity, power plant operations, or energy storage. 
     As an illustration,  FIGS.  2 A- 2 D  illustrate various non-limiting UPS operational modes that may be implemented by a UPS  202  with DGS features, in accordance with one or more embodiments of the present disclosure. In the non-limiting illustrations shown in  FIGS.  2 A- 2 D , the UPS  202  includes a connection to AC grid input power  204  (e.g., from a main utility grid) and a battery  206  connected to a buck-booster DC converter  208  (e.g., the adaptive DC conversion system  100 ) to provide DC power. The UPS  202  further includes a rectifier  210  to convert the AC grid input power  204  to DC power and an inverter  212  to generate AC output power  214  from either the rectified grid input power  204  or from the battery  206 . This AC output power  214  may be used for any purpose including, but not limited to, powering one or more loads connected to the UPS  202  (not shown). The UPS  202  may also include, but is not required to include, a bypass  216  to bypass the rectifier  210  and the inverter  212  to directly provide AC output power  214  from the AC grid input power  204 . 
     It is contemplated herein that each of the UPS operational modes depicted in  FIGS.  2 A- 2 D  may be implemented by operating the multi-mode DC converter circuit  102  of the adaptive DC conversion system  100  (represented simply as the buck-booster DC converter  208 ) in either a single PWM mode or a complementary PWM mode. However, operation of the multi-mode DC converter circuit  102  in a complementary PWM mode may facilitate rapid switching between any of the UPS operational modes. In this way, the UPS may enable DGS operation by supporting rapid changes in the UPS operational modes based on changing conditions of the grid and/or the load, based on control signals and/or commands from an external control, or the like. 
       FIG.  2 A  illustrates a full grid connection UPS operational mode, in accordance with one or more embodiments of the present disclosure. In this first operational mode, 100% of the output power  214  is provided by the grid input power  204 . Accordingly, the UPS  202  may operate as a standard double-conversion UPS. For example,  FIG.  2 A  illustrates 800 kW of output power  214  provided fully from the grid input power  204 . Further, in this first operational mode, the battery  206  may be at or near capacity such that the power flow is near zero. The PWM signals to the multi-mode DC converter circuit  102  may thus be selected to neither charge nor discharge the battery  206  and/or maintain the battery  206  in a floating charge state by providing a low current. It is contemplated herein that operating the multi-mode DC converter circuit  102  of the adaptive DC conversion system  100  in a single PWM mode providing DCM operation may be suitable for this UPS operational mode to provide power-efficient operation in a standard UPS state where DGS operation is not necessary, not requested by the monitoring circuitry  126 , and/or not requested by an external source. Alternatively, operating the multi-mode DC converter circuit  102  of the adaptive DC conversion system  100  in a complementary PWM mode providing CCM operation may be suitable for DGS operation in cases where the battery  206  is at or near capacity. 
       FIG.  2 B  illustrates a full discharge UPS operational mode, in accordance with one or more embodiments of the present disclosure. In this mode, 100% of the output power  214  is provided by the battery  206  and the output power  214  is fully disconnected from the grid. For example,  FIG.  2 B  illustrates 800 kW of output power  214  provided fully from the battery  206 , which is represented as −800 kW at the battery  206  to highlight power drain from the battery  206 . In this operational mode, the UPS  202  may fulfill the primary mission of protecting the load by running the battery  206 . The PWM signals to the multi-mode DC converter circuit  102  in this UPS operational mode may be selected to provide boost operation to discharge the battery  206  to provide the AC output power  214 . 
       FIG.  2 C  illustrates a partial discharge UPS operational mode, in accordance with one or more embodiments of the present disclosure. This DGS mode may implement regulated power exchange with the grid in which the grid input power  204  is reduced and supplemented with power from the battery  206 . For example,  FIG.  2 C  illustrates the combination of 600 kW of grid input power  204  with 200 kW of power from the battery  206  to provide 800 kW of output power  214 . In general, however, the output power  214  may be provided by any ratio of power from the grid or the battery  206 . The PWM signals to the multi-mode DC converter circuit  102  in this UPS operational mode may be selected to provide boost operation to discharge the battery  206  to provide the desired ratio of the AC output power  214 . Operating the multi-mode DC converter circuit  102  in a complementary PWM mode may be suitable for, but is not limited to, cases where the DGS operation is desired and the grid input power  204  is temporarily reduced. 
       FIG.  2 D  illustrates a recharge UPS operational mode, in accordance with one or more embodiments of the present disclosure. This DGS mode may implement regulated power exchange with the grid in which the grid input power  204  is increased to provide the desired output power  214  and also charge the battery  206 . For example,  FIG.  2 D  illustrates 1000 kW of grid input power  204  split to provide 800 kW of output power  214  and 200 kW to charge the battery  206 , which is represented as 200 kW at the battery  206  to highlight charging of the battery  206 . In general, however, the grid input power  204  may be divided between the battery  206  and the output power  214  in any ratio. In some embodiments, the maximum power that may be directed to the battery  206  may be limited (e.g., 20% of the available grid input power  204 , 25% of the available grid input power  204 , or any suitable number). In some cases, this maximum power that may be directed to the battery  206  is limited by the battery  206  such as, but not limited to, the battery recharge capacity, the maximum input current, or the like. The PWM signals to the multi-mode DC converter circuit  102  in this UPS operational mode may be selected to provide buck operation to charge the battery  206  with any desired portion of the input power  204 . Operating the multi-mode DC converter circuit  102  in a single PWM mode may be suitable for, but is not limited to, cases where the battery  206  is below capacity, but DGS operation is not necessary. Operating the multi-mode DC converter circuit  102  in a complementary PWM mode may be suitable for, but is not limited to, cases where the battery  206  is below capacity, but DGS operation is desired. For instance, changing load and/or grid conditions may necessitate switching to a different UPS operational mode (e.g., any of the UPS operational modes depicted in  FIGS.  2 A- 2 D ) and may further impact whether or not DGS operation is appropriate. 
     It is to be understood that the particular design of the UPS  202  and the DGS modes illustrated in  FIGS.  2 A- 2 D  are provided solely for illustrative purposes and should not be interpreted as limiting. 
     Referring now generally to  FIGS.  1 A- 3   , a UPS  202  including an adaptive DC conversion system  100  for selective DGS operation is described in greater detail, in accordance with one or more embodiments of the present disclosure. 
     In some embodiments, a UPS  202  includes an adaptive DC conversion system  100  with a multi-mode DC converter circuit  102  capable of selectively operating in a dynamic PWM mode and a power-saving PWM mode based on PWM signal sets  106  generated by an adaptive PWM controller  104 . In this way, the adaptive DC conversion system  100  may provide DGS features (e.g., any of the DGS operational modes illustrated in  FIGS.  2 A- 2 D ) in at least the dynamic PWM mode and energy-efficient operation in the PWM mode when DGS features are not required. 
     It is contemplated herein that providing dynamic grid support may require a DC converter with a high responsivity (e.g., high-speed current loop performance) to respond to changing grid conditions. As an illustration, responsivities in the range of 10-100 ms may be required for certain applications. 
     DC converters may be configured in various ways to provide the requisite high responsivity, though such designs are typically not power efficient at low loads. In some embodiments, the multi-mode DC converter circuit  102  may operate in a complementary PWM mode (e.g., a dynamic mode) in which one or more pairs of power switches  108  are driven by complementary PWM signal sets  106  to maintain inductors  110  within the multi-mode DC converter circuit  102  in a continuous-conduction mode. In such a complementary PWM mode, the continuous-conduction operation of the inductors  110  may facilitate high power-tracking speed required for DGS operation (e.g., operation in a DGS state). In this way, a complementary PWM mode may facilitate rapid switching between various operational modes (e.g., any of the modes illustrated in  FIGS.  2 A- 2 D ) based on grid conditions. 
     However, it is contemplated herein that DGS operation (e.g., operation in a DGS state) may not be needed continuously, but rather during limited timeframes. Further, in some applications, timeframes during which DGS operation may be needed may be known in advance, received from an external source (e.g., an external controller, or the like), and/or determinable via monitoring (e.g., with monitoring circuitry  126 ). Accordingly, in some embodiments, the multi-mode DC converter circuit  102  is further capable of operation in a single PWM mode (e.g., a standard UPS mode) in which the inductors  110  are kept in a discontinuous-conduction mode. For example, in standard UPS operation with buck/booster multi-mode DC converter circuit  102  configured in single PWM mode when the battery  206  is recharging and/or near a full charge and DGS operation is not required, the charging current may be decreased (or decrease naturally) to low values and the voltage (e.g., a charger voltage) may be kept constant or nearly constant (e.g., with a proper modulation of a power switch  108 ). As a result, the power dissipation in such a single PWM mode may be substantially smaller than in a complementary PWM mode during standard UPS battery charging operations since power losses on power switches  108  and inductors  110  will be lower. Further, in cases where there are relatively long periods of time between DGS operation, an adaptive DC conversion system  100  as disclosed herein may provide substantial improvement in power consumption and associated cost relative to alternative UPS systems without adaptive PWM mode switching. 
       FIG.  3    is a flow diagram illustrating dynamic operation of a UPS  202  with an adaptive DC conversion system  100  in multiple operational modes, in accordance with one or more embodiments of the present disclosure. For example, the UPS  202  may have the components illustrated in  FIGS.  2 A- 2 D  including the rectifier  210  to receive AC grid input power  204 , a buck-booster multi-mode DC converter circuit  102  coupled to a battery  206 , and an inverter  212  to provide AC output power  214  from any combination of the grid input power  204  or the battery  206 . 
     In particular,  FIG.  3    illustrates the operation of the buck-booster multi-mode DC converter circuit  102  in either a single PWM mode (block  302 ) providing power-efficient operation or a complementary PWM mode (block  304 ) providing high-speed responsivity. Further, these different PWM modes may be leveraged in multiple circumstances when necessary. For example,  FIG.  3    illustrates a standard UPS state  306  in which the UPS  202  operates as a typical UPS (e.g., as illustrated in  FIG.  2 A ) and a DGS state  308  (e.g., a DGS operational mode) providing high-speed operation suitable for any number of operational modes (e.g., any of the operational modes illustrated in  FIGS.  2 A- 2 D ), where each of the states or operational modes may utilize any number of PWM modes as necessary. 
     In some embodiments, the UPS  202  initially enters a standard UPS state  306  after power up (block  310 ) and initialization (block  312 ) and then switches between the states based on requests. Such requests may include a selection of an operational mode generated using any suitable technique. For example, the selection of an operational state (e.g., the standard UPS state  306  or the DGS state  308 ) may be performed by a user, by an internal monitor (e.g., monitoring circuitry  126 ), or by any external source. 
     In some embodiments, the standard UPS state  306  includes configuring the adaptive PWM controller  104  to provide a single PWM mode (block  302 ) that places the buck-booster multi-mode DC converter circuit  102  in charge mode (e.g., a buck mode) (block  314 ) to charge the battery  206  with at least a portion of the grid input power  204  if necessary (see e.g.,  FIG.  2 D ). 
     For example, the adaptive PWM controller  104  may generate PWM signal sets  106  that drive only a single power switch  108  in a way that operates the buck-booster multi-mode DC converter circuit  102  in a charge mode. In this way, the PWM signal sets  106  may provide proper modulation of the power switch  108  to keep the charging current at a relatively low value and provide a constant charger voltage to the battery  206 . As a result, the power dissipation in such a single PWM mode may be lower than using a complementary PWM mode under these conditions. 
     In some embodiments, the UPS  202  enters a DGS state  308  upon a request (block  316 ). In the DGS state  308 , the adaptive PWM controller  104  is configured to operate in a complementary PWM mode (block  304 ) to provide high responsivity suitable for DGS operations. For example, each of the operational modes illustrated in  FIGS.  2 A- 2 D  may be implemented using different complementary PWM signal sets  106 . Accordingly, DGS operation (block  318 ) may include operation in any operational mode and/or rapid switching between various operational modes based on the needs of the grid. The UPS  202  may then remain in the DGS state  308  until a request for the standard UPS state  306  is received (block  320 ). 
     It is contemplated herein that the use of different PWM modes to selectively provide dynamic operation of a multi-mode DC converter circuit  102  may be advantageous for many applications or situations. In this way, the use of different PWM modes is not limited to selectively providing DGS functionality or traditional UPS functionality. As an illustration,  FIG.  3    illustrates the use of a complementary PWM mode (e.g., block  304 ) for system monitoring in either the standard UPS state  306  or the DGS state  308 . 
     In some embodiments, the UPS  202  may temporarily utilize a complementary PWM mode (block  304 ) if necessary to provide high-performance operation when needed. For example,  FIG.  3    illustrates monitoring a rectifier input voltage (block  322 ) (e.g., the input voltage of the rectifier  210  illustrated in  FIGS.  2 A- 2 D ). If the rectifier input voltage is not acceptable, the adaptive PWM controller  104  is configured to provide a complementary PWM mode (block  304 ) that places the buck-booster multi-mode DC converter circuit  102  in booster mode (block  324 ). In this way, the multi-mode DC converter circuit  102  can have a fast response required to feed the inverter  212  and the load without interruption in order to satisfy the primary UPS mission of protecting the load. Once the rectifier input voltage is acceptable, the UPS  202  may return to normal operation in either the standard UPS state  306  or the DGS state  308 . 
     Referring again generally to  FIGS.  2 A- 3   , it is to be understood that  FIGS.  2 A- 3    are provided solely for illustrative purposes and should not be interpreted as limiting. Rather, an adaptive DC conversion system  100  may generally provide different PWM modes for operation as any type of switched-mode DC converter. In this way, the illustrations and examples referring to operation in the context of a UPS are merely illustrations. Further, the illustrations and examples referring to the particular PWM modes (e.g., the single PWM mode or the complementary PWM mode) are also merely illustrations. It is contemplated herein that an adaptive DC conversion system  100  as disclosed herein may operate in any number or type of PWM modes based on selective use of associated PWM signals to various power switches. 
     The herein described subject matter sometimes illustrates different components contained within, or connected with, other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures can be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermedial components. Likewise, any two components so associated can also be viewed as being “connected” or “coupled” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “couplable” to each other to achieve the desired functionality. Specific examples of couplable include but are not limited to physically interactable and/or physically interacting components and/or wirelessly interactable and/or wirelessly interacting components and/or logically interactable and/or logically interacting components. 
     It is believed that the present disclosure and many of its attendant advantages will be understood by the foregoing description, and it will be apparent that various changes may be made in the form, construction, and arrangement of the components without departing from the disclosed subject matter or without sacrificing all of its material advantages. The form described is merely explanatory, and it is the intention of the following claims to encompass and include such changes. Furthermore, it is to be understood that the invention is defined by the appended claims.