PATENT DOCUMENT

Publication Number: US-11539231-B1
Application Number: US-201916520036-A
Country: US
Kind Code: B1

Title: Method and system for single stage battery charging

Abstract:
Aspects of the present disclosure involve a system and method for providing a boosted voltage using a single stage dual active bridge converter. In one embodiment, the single stage dual active bridge converter is introduced for high voltage charging using phase shift and frequency control. Phase shift and frequency control can be implemented on duty cycled switches and pulse width modulated switches in order to achieve a desired output voltage. In another embodiment, the phase shift and frequency controlled single stage dual active bridge converter is replicated in modular form to provide a single-phase system that provides a voltage for charging a high voltage system. In yet another embodiment, the phase shift and frequency controlled single stage dual active bridge converter is replicated in modular form to provide a three-phase system that provides a voltage for charging a high voltage system.

Claims:
What is claimed is: 
     
       1. A method of charging a battery comprising:
 in a bridge converter charging a battery that transitions while charging from a first voltage zone associated with a first battery voltage to a second voltage zone associated with a second battery voltage that is higher than the first battery voltage, constant power charging while charging within both the first voltage zone and the second voltage zone; 
 controlling the bridge converter using phase shift control alone while charging the battery within the first voltage zone; and 
 when the battery transitions to the second zone, controlling the bridge converter using frequency shift control and phase shift control while charging the battery within the second voltage zone. 
 
     
     
       2. The method of charging a battery of  claim 1  further comprising:
 during charging of a battery that transitions while charging to a third voltage zone associated with a third battery voltage that is higher than the second battery voltage, 
 controlling the bridge converter using phase shift control and frequency control in the third voltage zone to decrease power as the third battery voltage increases during charging. 
 
     
     
       3. The method of  claim 1  wherein the bridge converter is a single stage dual active bridge converter. 
     
     
       4. The method of  claim 3  wherein an output power of the single-stage dual active bridge converter is directly proportional to phase shift and inversely proportional to switching frequency. 
     
     
       5. The method of  claim 3  wherein the single-stage dual active bridge converter comprises an H-bridge rectifier operably coupled with a H-bridge converter through a transformer. 
     
     
       6. The method of  claim 1  wherein the bridge converter is a dual active bridge converter, the method further comprising:
 controlling the dual active bridge converter using constant frequency control while charging within the first voltage zone. 
 
     
     
       7. The method of  claim 1  wherein the phase shift control and the frequency shift control are generated from:
 a frequency shift value and a phase shift value based on a voltage difference of a sensed instantaneous voltage at an input to a secondary side of the bride converter and a battery voltage, and whether the battery voltage is within the first voltage zone or the second voltage zone. 
 
     
     
       8. The method of  claim 1  wherein at least one of the phase shift control and the frequency shift control is further based on a grid voltage to provide power factor correction. 
     
     
       9. A battery charger comprising:
 a bridge converter including an H-bridge rectifier connectable to a source of AC power, an H-bridge converter connectable to a battery, and a transformer interconnecting the H-bridge rectifier and the H-bridge converter; 
 a controller in operably communication with the bridge converter, the controller including instructions to:
 control the bridge converter using phase shift control alone while charging within a first voltage zone of the battery; and 
 when the battery transitions to the second zone, control the bridge converter using frequency shift control and phase shift control while charging within a second voltage zone of the battery, the second voltage zone being associated with a battery voltage higher than a battery voltage of the first voltage zone. 
 
 
     
     
       10. The battery charger of  claim 9  wherein:
 the controller further includes instructions to control the bridge converter using constant power within both the first voltage zone and the second voltage zone. 
 
     
     
       11. The battery charger of  claim 9  wherein:
 the controller further includes instructions to control the bridge converter using frequency shift control and phase shift control while charging with a third voltage zone of the battery that is associated with a battery voltage that is higher than a battery voltage of the second voltage zone. 
 
     
     
       12. The battery charger of  claim 10  wherein:
 the controller further includes instructions to control the dual active bridge converter using constant power within both the first voltage zone and the second voltage zone; and 
 apply deceasing power within a third voltage zone as the battery voltage increases. 
 
     
     
       13. The battery charger of  claim 9  wherein the bridge converter is a single stage dual active bridge converter, and wherein the single-stage dual active bridge converter is one of a plurality of single-stage dual active bridge converters coupled in parallel between a source of AC power, and outputs of each of the plurality of single-stage dual active bridge converters being operatively intercoupled to provide a summed output charging voltage. 
     
     
       14. The battery charger of  claim 13  wherein the plurality of single-stage dual active bridge converters comprises a first single-stage dual active bridge converter, a second single-stage dual active bridge converter, and a third single-stage dual active bridge converter, and wherein the controller includes instructions to control the first single-stage dual active bridge converter shifted by 120 degrees relative to the second single-stage dual active bridge converter, and control the third single-stage dual active bridge converter shifted by 120 degrees relative to the second single-stage dual active bridge converter. 
     
     
       15. The battery charger of  claim 14  wherein the source of AC power comprises a first source of AC power for the first single-stage dual active bridge converter, a second source of AC power for the second single-stage dual active bridge converter and a third source of AC power for the third single-stage dual active bridge converter. 
     
     
       16. The battery charger of  claim 9  wherein the phase shift control and the frequency shift control are generated from a frequency shift value and a phase shift value based on a voltage difference of a sensed instantaneous voltage at an input of the H-bridge converter and a battery voltage during charging, and whether the battery voltage is within the first voltage zone or the second voltage zone.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/712,795, filed Sep. 22, 2017, titled “METHOD AND SYSTEM FOR SINGLE STAGE BATTERY CHARGING,” which is related to and claims priority under 35 U.S.C. § 119(e) from U.S. Patent Application Ser. No. 62/398,670, filed Sep. 23, 2016, titled “METHOD AND SYSTEM FOR SINGLE STAGE BATTERY CHARGING,” both of which are incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to a power correction factor system architecture used to supply an increased output voltage from a battery to a high load. 
     BACKGROUND 
     High powered systems generally utilize a high voltage battery charging system. Such high voltage battery charging systems often come in the form of a multi-stage system with an AC-to-DC power factor correction stage and a DC-to-DC stage. Multi-stage systems, however, are often voluminous, inefficient, or have low power densities. A single stage, high voltage battery charging system would therefore reduce many of the drawbacks to multi-stage high voltage battery charging systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which: 
         FIG.  1    is a diagram illustrating a single-stage, dual-active bridge converter. 
         FIG.  2    is a graph illustrating a control scheme for frequency and phase shift control for a single-stage, dual active bridge converter. 
         FIG.  3    is a diagram illustrating the frequency and phase shift control loops for a single-stage, dual active bridge converter. 
         FIG.  4    is a flowchart of a method for providing phase shift and frequency control to a single-stage, dual-active bridge converter. 
         FIG.  5    is a diagram illustrating a phase modular single-stage, dual-active bridge converter for single-phase operation. 
         FIG.  6    is a flowchart of a method for single-phase charging using a phase modular single-stage, dual-active bridge converter. 
         FIG.  7    is a diagram illustrating a phase modular single-stage, dual-active bridge converter for three-phase operation. 
         FIG.  8    is a flowchart of a method for three-phase charging using a phase modular single-stage, dual-active bridge converter. 
         FIG.  9    is a diagram illustrating an example of a computing system which may be used in implementing embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present disclosure involve systems, methods, devices, and the like for supplying power to a battery for charging. In one embodiment, a single stage charger is introduced for high voltage charging that utilizes phase shift and frequency control. In one particular embodiment, the single stage charger may include a dual active bridge (DAB) converter with a primary and secondary side designed to perform power factor correction (PFC), AC-to-DC conversion, and DC-to-DC conversion. The primary side and secondary side of the DAB converter can each include an H-bridge circuit with switches that can operate using distinct modulation schemes. In particular, phase and frequency control can be implemented through the operation of the switches of the single stage charger to provide a desired output voltage while maintaining efficiency and high power density during charging of the battery. Both phase and frequency modulation may be applied to control the single stage DAB circuit over the entire operating range of the battery. In one embodiment, a modulator selects either or both of the frequency control or phase shift control of the DAB circuit based upon a sensed output battery voltage. 
     In another embodiment, a phase modular single stage circuit provides high power to charge a battery that may be operational in a one-phase or three-phase topology. In one particular example, the phase modular circuit includes three independent single stage chargers that can be interconnected at the output, with each of the three single stage chargers independently controllable to provide a total summed high output power. In addition, each single stage charger may also be independently phase and/or frequency controlled to achieve a desired output to charge a battery. 
     Conventionally, providing a high voltage range for charging of a battery has been accomplished by using a multi-stage charger generally including two (or more) independent stages that are joined by a DC bulk storage capacitor for energy storage and harmonic cancellation. In the multi-stage charger configuration, a first stage generally performs the AC-to-DC power correction stage (with the DC bulk storage capacitor) with an isolated second stage for DC-to-DC conversion. However, such a two stage topology can be inefficient or have low power density, especially at high voltage ranges. 
     In contrast,  FIG.  1    illustrates an example embodiment of a single-stage, dual active bridge AC-DC converter  100  (hereinafter “DAB converter  100 ”) for supplying output DC power signal (e.g., output  104 ) relative to an input AC input (e.g., AC source at input  102 ) to charge a battery. More particularly,  FIG.  1    is a diagram illustrating a single-stage charger with a primary side “H-bridge” power factor correction (PFC) rectifier  106  and a secondary side H-bridge converter  108 . A transformer  110  couples the primary side  106  and the secondary side  108  with a 1: n winding ratio. In general, DAB converter  100  is a singular stage system where the secondary side  108  switches S 5 -S 8  operate as a function of the primary side  106  switches S 1 -S 4 . Thus, the S 5 -S 8  switches can be controlled at least based in part on the functionality of the S 1 -S 4  switches. For example, the S 1 -S 4  switches on the H-bridge of the primary side  106  can be designed to operate on a particular duty cycle while the S 5 -S 8  switches on the H-bridge of the secondary side  108  can be designed to depend on the voltage of the S 1 -S 4  switches. In one embodiment, the S 1 -S 4  switches operate on a 50% duty cycle and the S 5 -S 8  switches are voltage controlled using Pulse-Width Modulation (PWM), as described in more detail below. 
     As indicated above, in the primary side  106  of the DAB converter  100 , the switches S 1 -S 4  can operate at 50% duty cycle. In particular, switches S 1 , S 4  and switches S 2 , S 3  operate in complementary fashion at duty ratio of 50% of switching frequency during both cycles of AC voltage. For example, during a positive cycle of AC voltage (VAC&gt;0), switches S 1 , S 4  turn ON, hence transformer primary voltage V 1  equals VAC for Ts/2 time interval. Next switches S 2 , S 3  turn ON (with switches S 1 , S 4  turned OFF) and transformer primary voltage V 1  equals-VAC for the next Ts/2 time interval. Here Ts has a switching period (of say 10us). The transformer primary voltage V 1  is a bipolar AC quasi-square waveform with an envelope of 60 Hz grid voltage on top but is chopped at 50% duty ratio to generate high frequency voltages (at say 100 kHz). V 1  is then provided to the transformer  110  portion of the circuit  100 . The transformer, having 1:n winding, operates to either up-convert or down-convert the voltage V 1  provided at the input of the transformer  110  to higher voltage, namely nV 1 , depending on the battery operating voltage range requirement. Inductors L 1 , L 2  and capacitor C 1  of the transformer circuit  110  are magnetizing inductance of the transformer, leakage inductance of the transformer, and resonant capacitor to filter our switching noise, respectively, in the DAB converter  100  circuit. 
     The output of the transformer circuit  110  is provided as an input at the secondary side converter  108  of the DAB converter  100 . In general, the secondary side converter  108  provides a pulse-width modulated signal as an output for voltage regulation. Pulse-Width Modulation (PWM) is a control scheme that can be used to control the power supplied to a load at an output  104 . The output power provided from the secondary side converter  108  is generally controlled by utilizing switches S 5 -S 8  to switch between supplying power to the load and removing power to the load at a determined rate to achieve a desired voltage level. For example, if the output voltage is used to charge a battery at 240V, then the switches S 5 -S 8  can be controlled to turn off if the approximated voltage is greater than 240V and turn back on if the approximate voltage is less than 240V. In this manner, switches S 5 -S 8  are switched on and off at a particular rate such that the output power at output  104  approximates a desired power level. 
     The control of the switches S 1 -S 4  and S 5 -S 8  in the DAB converter  100  may be controlled unlike the switch control used in conventional single-stage dual active bridge converters which generally operate at 50% duty cycle and provide constant power charging. Rather, in one embodiment, the voltage control provided through the PWM aspect of the converter  108  enables the duty ratio of the S 5 -S 8  switches to be a function of the switching operation of the primary side  106  switches S 1 -S 4 . That is to say, the operation of the S 1 -S 4  switches (and in particular the output voltage from the S 1 -S 4  switches) controls the switching rate of the S 5 -S 8  switches on the secondary side  108  of the DAB converter  100  circuit. Thus, an optimized switching control scheme (e.g., phase shift and/or frequency control) can be formulated for operation of DAB converter  100  to meet battery charging requirements and attain higher efficiencies over conventional topologies. 
     Although DAB converter  100  architecture is shown in  FIG.  1    to include two conversion portions with switches, inductors, transformers, and capacitors, the circuit is not so limited. It should be appreciated that other system configurations may be possible as is the addition and/or reduction of other components. Further, the components including the inductors, capacitors, and switches may be replaced by other components with similar functionality. For example, switches S 1 -S 8  may be replaced by relays, MOSFETS, IGBTs, SMPS, transistors, and the like. 
     As indicated above, an optimized switching scheme can be formulated for use by the DAB converter  100  to meet load power (e.g., battery) requirements.  FIG.  2    is a graph illustrating a control scheme  200  that introduces frequency and phase shift controls for varying output voltage values of the battery that may be used in the operation of the single-stage dual active bridge converter  100  to charge the battery. As shown, the control scheme  200  may be divided into separate operational zones (e.g., Zone  1   202 , Zone  2   204 , and Zone  3   206 ). Zone  1   202  defines a control scheme applied to the charging of the battery when the output voltage from the battery is low. In this zone, a constant power level (illustrated in  FIG.  2    as line  212 ) is provided to charge the battery, as defined in more detail below. Zone  2   204  defines a control scheme applied to the charging of the battery when the output voltage from the battery is nominal, or within a normal operating voltage range for the battery. Similar to Zone  1   202 , a constant power level is provided to charge the battery during operation within Zone  2   204 . Zone  3   206  defines a control scheme applied to the charging of the battery when the output voltage from the battery is high. The control scheme for Zone  3   206  provides a decreasing charging power to the battery through manipulation of a phase shift control and a frequency control of the DAB converter  100 . The phase and frequency control scheme  200  illustrated in  FIG.  2    allows for operation of the DAB converter  100  to recharge a battery over a large range of battery output voltage values, which may otherwise not be efficiently provided. In this manner, the phase shift and frequency control scheme  200  provides control of the DAB converter  100  to achieve improved performance over a large voltage range of battery operation. 
     In control scheme  200 , each zone  202 - 206  is divided into output voltage ranges or specifically into load/battery operating ranges. For example, Zone  1   202  may be the voltage range that accounts for low operating voltages (output voltages) In this zone, the battery is charged with a constant power, as shown in control scheme  200 . The DAB converter  100  operating in this zone provides the constant power charging signal to the battery through a constant frequency control  208  and adjusting the phase shift control  210  on the switches S 1 -S 8 . In general, phase shift control  210  is a control scheme of the DAB circuit  100  that controls the on time of one or more of the switches. Specifically, it provides the time delay that the switches S 1 -S 8  encounter before turning on or activating relative to the corresponding switches on the other side of the circuit. In addition, frequency control is a control scheme that controls the width or period of the pulsating wave that is applied to the switches. For example, frequency control may provide the amount of time the secondary side switches S 5 -S 8  of the DAB converter  100  remain on. In Zone  1   202  of  FIG.  2   , phase shift control  210  is applied while frequency control  208  is held constant. As such, in Zone  1   202  the switches S 5 -S 8  can be turned on as indicated by the phase shift control, while the width (e.g., period) of the pulse provided to the switches S 5 -S 8  is held constant at a minimum operating frequency. Further details, including a control circuit regarding the phase shift control and frequency control are described below and in conjunction with  FIG.  3   . 
     Turning back to  FIG.  2   , Zone  2   204  is defined for nominal battery output voltage values. To operate the DAB converter  100  within Zone  2   204 , both frequency and phase shift control are used in order to provide the constant charging power  212  that may be needed at the battery. In particular, at nominal battery voltages, frequency control  208  and phase shift control  210  is introduced to leverage the additional power needed by the battery. As visible in graph  200 , Zone  2   204  includes an area of DAB converter  100  operation where both frequency control  208  and phase shift control  210  are used. In general, output power of a DAB converter  100  can defined as:
 
   P =a*f ( n,Vi ,Vbat)*δ/( L*fs )
 
with
 
 {circumflex over (d)}=x+y*n*Vi /Vbat
 
where, f(n,Vi,Vbat) is some function of n, Vi, and Vbat and x and y are some constants. Thus, output power  P  is directly proportional to phase shift (δ) and inversely proportional to switching frequency. The purpose of the duty cycle control on secondary converter being a function of the grid voltage Vi is to shape the grid currents for power factor correction. Therefore, as illustrated in Zone  2   204 , a change in frequency will inherently also provide some phase shift control  210 .
 
     At the highest voltage region, Zone  3   206 , frequency control  208  is held constant and again phase shift control  210  is used. In some instances, a voltage limit may be set to establish a corresponding cut off frequency that is too high to use. Therefore, at Zone  3   206 , a sharp decrease in power  212  is observed as frequency control  208  again is held constant and phase shift control  210  is used to deliver the required power to charge the battery. 
     Note that the control scheme  200  also includes boundaries separating each zone, which define the boundaries of operation  214 ,  216 . That is to say, boundaries  214 ,  216  indicate the location where different control schemes for phase shift control  210  and/or frequency control  208  are used. Additionally, boundary  216  can indicate the threshold voltage which corresponds to a frequency value that cannot be exceeded (e.g., maximum operating frequency). Similarly, boundary  214  can identify the threshold voltage that defines the transition from low voltages into nominal voltages for the use of frequency control  208 . It should be appreciated that the values assigned or associated with the boundaries  214 ,  216  may be any battery output voltage. For example, the particular voltage values that define a “low” value, a “nominal” value, or a “high” value may be any value and may, in some instances, be set as a particular percentage of the total output voltage capability of the battery being charged. 
       FIG.  3    is a diagram illustrating a control block  300  used to control the phase shift and frequency of the DAB converter circuit  100 . Specifically,  FIG.  3    illustrates one embodiment of phase shift and frequency control loops  302 ,  304  for a single-stage dual active bridge converter  100 . As indicated, phase shift and frequency control may vary based on the battery voltage range of operation. As such, the phase shift loop  302  and/or the frequency loop  304  are activated based on the voltage range of operation as illustrated in the control scheme  200  of  FIG.  2   . In some instances, phase shift control may be applied, while the frequency control is held constant. In other instances, frequency control may be applied such that phase shift control also inherently applied. Examples of the phase shift and frequency control of the DAB circuit  100  through control of the phase shift loop  302  and/or the frequency loop  304  are shown in the control scheme  200  of  FIG.  2   . 
     The main inputs to the control loops are the output power reference of the DAB converter  100  (Ibatt) and the battery current reference (Ibatt_ref). These values can be determined or read by a processor or other module such that once determined, the zone  202 - 206  of operation and thus the control scheme for the control loops  302 ,  304  to use are defined. For example, if the battery has a low output voltage such that a constant power charge signal is provided, then operation of the DAB converter  100  is in Zone  1   202 . As indicated in  FIG.  2   , Zone  1   202  utilizes a constant frequency control  208  and a varying phase shift control  210 . In one instance, the phase shift control loop  302  and frequency control loop  304  are controlled based on the battery current reference Ibatt_ref In other instances, the control loops may have a voltage mode control or power mode control. 
     As indicated, in current mode control, the use of phase shift and/or frequency control loops is based on the desired output voltage of operation Vbatt_ref and the zone the output voltage Vbatt_ref falls in, as defined by the zone boundaries  214 ,  216  of the control scheme  200 . In instances where phase shift control is used, battery current reference Ibatt_ref is input into the phase shift control loop  302 . Alternatively, in instances where frequency control is used, the battery current reference Ibatt_ref is input into the frequency control loop  304 . In either instance, the phase shift loop  302  and/or frequency loop  304  control the charging power provided to the battery by the DAB converter  100  circuit to recharge the battery during operation. In general, the frequency and phase-shift controllers  302 ,  304  can act either independently or together to generate the references for the modulator block  306 . In some instances, the modulator block  306  also gets an input for duty ratio (d) reference based on the sensed input and output voltages and generates the switching signals for the two H-bridges of the DAB converter  100 . 
     In general, the modulator  306  is a module that can communicate with the output pins in each of the switches. Therefore, the modulator  306  may control each switch individually and can thus use the delta identified to control the bridges on both sides of the transformer in the DAB controller  100 . As shown in the graph  200  of  FIG.  2   , constant power is provided to the battery through control of the frequency loop  304  and the phase shift loop  302 . In particular during Zone  1   202  operation, switching frequency is held constant at or near the minimum operating frequency while phase shift control is solely utilized to control the power transfer to the battery. 
     Similarly, when the output battery voltage falls within Zone  2   204  of  FIG.  2    (or within a nominal output voltage), frequency control is applied to the DAB controller  100  through the frequency loop  304  in order to provide the desired recharge power to the battery. In particular, frequency control is applied based on a frequency offset identified by the frequency control loop  304 . The frequency control loop works much like the phase shift control loop  302 . In one particular embodiment, the frequency control loop  302  determines a reference current (Ibatt_ref) and compares it to the sensed current (Ibatt_sense) at the battery. The comparison provides an offset or voltage error frequency (Ve_freq) that is fed into the phase shift controller (PI-freq) to reduce the error and obtain the voltage offset (Vc_f) that needs to be compensated. The phase shift controller may be followed, in some instances, by a saturation loop which can include an anti-windup gain AWg for correcting the voltage offset (Vc_f) if it exceeds the modulation bounds. Once the offset has been corrected, the delta voltage (Vc_freq) is converted to a frequency value with the use of a carrier generator such as a voltage controlled oscillator (VCO). A VCO is an oscillator whose oscillating frequency is controlled by its input voltage. In other words, the instantaneous oscillating frequency (e.g., delta frequency value) is determined by an applied input voltage (e.g., delta voltage). The delta frequency value is then processed by modulator  306  which can control each of the switches in the DAB controller  100 . A frequency delta represents a change in the period of the PWM signal between the primary and secondary sides  106 ,  108 . 
     Through this, both the switching frequency and phase shift control are utilized to deliver the constant power to the battery. In particular, phase shift between the primary and secondary bridges increases inversely with increase in the output battery voltage. Further, frequency control increases proportionally to the increase in operating battery output voltage. 
     In one embodiment, DAB converter  100 , is a converter with a primary side  106  and a secondary side  108 . The primary side  106  may include bi-directional switches S 1 -S 4 , operating at a 50% duty cycle. The secondary side  108  may include switches S 5 -S 8 , that are pulse width modulated. The pulse width modulation of switches S 5 -S 8 , may be controlled by control block  300 , where phase and/or frequency control is added to place the power provided to the battery at a desired level. The phase and/or frequency control is determined based on the operation zone (e.g., Zone  1   202 -Zone  3   206 ) the desired output voltage falls in. Further, modulation of switches S 5 -S 8  can occur via frequency, pulse width, and/or phase shift modulation of the switches. Thus, switches S 5 -S 8  can be controlled by an ON/OFF signal and time synchronization. Therefore, a phase shift provides a delay, relative to the primary side  106  switches S 1 -S 4 , before providing the ON signal to the secondary side switches S 5 -S 8 , while the frequency delta provides the period of the signal or the amount of time the secondary side switches S 5 -S 8  are ON. 
     As an example, the DAB converter  100  can operate with a 50% duty cycle on the primary side  106  and PWM of the secondary side  108  and have an input alternating current voltage with a 10 μs period. Thus, the signal can have a 5 μs positive cycle and a 5 μs negative cycle. If it is determined that a 2 μs phase shift is needed for powering the load to the desired output power, then the switches on the secondary side  108  turn ON 2 μs later with respect to the start time of the switches on the primary side  106 . The phase shift provided accounts for the voltage required to maintain the constant power to the load at the desired output voltage level. 
     Note that in control block  300 , control of the DAB converter  100  may occur at a processor. Thus, detection of the voltage at the battery, the desired voltage of operation, and the AC side voltage, may be determined by a processor (not shown). The parameter generation block may receive the values and provide them to the control loops  320 ,  304  and modulator  306 . Modulator  306  may use the parameters in conjunction with the phase shift delay and/or frequency delay to control the switches. Additionally, modulator  306  can perform time synchronization as may be necessary by the system (e.g., frequency modulation). 
     In operating in Zone  3   206  (or high operating battery voltage), the power provided to the battery is reduced proportionally to an increase in the operating voltage of the battery, dropping to zero charging power. In this zone, switching frequency is held constant and only phase shift control is utilized to deliver the required power in a similar manner as described above. 
       FIG.  4    is a flowchart of a method for single-phase charging using phase shift and frequency control. As illustrated in  FIG.  3   , a control block  300  is introduced for use in phase shift and frequency control for the charging of a battery utilizing the single-stage dual active bridge converter  100 .  FIG.  4    corresponds to the flowchart used for providing the desired output power at the battery using the phase shift and frequency control of control block  300 . 
     In this process, method  400  begins with operation  402  where a processor or other module obtains the operating voltage at the load, such as a battery. The voltage can be a predetermined value known by the processor or can be read by the processor or other module from the load. The output voltage can then be used to determine the corresponding control zone  202 - 206  in order to identify the corresponding control mechanism (e.g., frequency control and phase shift control) to use. 
     After the output voltage is known, method  400  continues to operation  404  where the instantaneous voltage at the input of the secondary side (e.g., the input of the H-bridge on the secondary side) is sensed. Sensing of the instantaneous voltage can occur by a processor or other module as well. The instantaneous voltage is read in order to determine the delta or difference between the desired output voltage at the load/battery and the voltage arriving at the switches S 5 -S 8 . Note that in some instances, the instantaneous voltage at the input of the secondary side H-bridge and output voltage can be determined simultaneously. 
     In operation  406 , the voltage difference between the output voltage and instantaneous voltage is computed. The difference is used to determine the corresponding frequency delta and/or phase shift that provides the desired output voltage. Determining the voltage difference between the output voltage and the instantaneous voltage can occur at both or one of the control loops  302 ,  304  in  FIG.  3   . 
     Operation  408  includes determining the frequency delta and phase shift corresponding to the calculated voltage difference determined in operation  406 . A phase shift controller may be used to determine the frequency delta and phase shift. A phase shift controller is generally a feedback regulator that helps eliminate the error between a baseline voltage (e.g., output voltage) and the current voltage in the system (instantaneous voltage). In some instances, a saturation loop and/or an anti-wind up gain may be used if the frequency delta and/or phase shift determined exceed the modulation bounds of the system. Additionally, a voltage-controlled oscillator (VCO) can be used in the frequency control loop  304  to enable the conversion from a delta voltage to a frequency voltage. 
     In operation  410 , control of the switches on the secondary H bride in the single stage dual active bridge converter  100  occurs. As indicated above, the modulator has a direct connection to the switches on the bridges, thus is able to control the switching in order to achieve the desired output voltage. 
     Some advantages may be achieved through the use of the DAB converter  100 . For example, the single-stage converter  100  may operate in a soft-switching state, such as zero-voltage switching (ZVS) zero-current switching (ZCS), etc. Unlike multi-stage converters in which only the DC-DC stage is soft-switched, the PFC stage of the disclosed DAB converter  100  may be hard-switched, meaning that it has significant switching losses. The single-stage converter control described above ensures that the circuit maintains either ZVS or ZCS so that the switching losses are near-zero, resulting in a high efficiency for the circuit operation. Also having zero or near zero switching losses gives it the flexibility to be pushed higher in switching frequencies to bring down the size of the magnetics, thereby increasing the net power density of the charger. 
     In addition, the circuit topology described herein provides bi-directional functionality, enabling power flow in both forward and reverse directions. In a grid to vehicle direction of operation, power is drawn from the grid to charge the electric vehicle. In a vehicle to grid direction of operation, power may be fed to the grid from the vehicle battery. In this scenario, the vehicle is treated as a storehouse of energy and feeds excess energy back to the grid. The bi-directional power flow is enabled by the use of switches in both primary and secondary H bridges which allow current conduction in both directions. In the scenario of reverse power flow, the converter essentially serves as an inverter, converting DC voltage from the battery to AC voltage synchronized at the grid line frequency. Phase shift and delta is the control variable used to transfer power from the source to the load in the forward power flow condition. By adjusting the phase shift from positive to negative, reverse power flow can be achieved. Also, similar to grid inverter control strategies, a phase lock loop can be used to synchronize the fundamental frequency of the converter to the grid frequency. 
     In some instances, it may be difficult to achieve the high voltage charging required by some high voltage devices operational at 800V and/or 1200 V using a single-stage dual active bridge converter system like DAB converter  100 . Therefore, modular system  500  in  FIG.  5    is introduced where DAB converter  100  of  FIG.  1    is duplicated to form a modular phase topology that enables conversion to higher power by providing higher currents. By having three modules in a phase modular approach, the circuit  500  of  FIG.  5    enables higher power levels by summing up the individual output currents from each module. Specifically,  FIG.  5    is a diagram illustrating a phase modular single-stage dual-active bridge converter  500  for single-phase operation. 
     In the single-phase topology of modular system  500 , three modular converters  502 - 506  (e.g., DAB converter  100 ) are duplicated and interconnected in parallel to provide a total high voltage desirable for high voltage charging of a load (e.g., battery V 7  in a high voltage device) and may be stored in capacitor C 2 . In modular system  500 , the interconnection between the three modular converters  502 - 506  for single-phase operation includes combining these modular converters  502 - 506 . In general, the modular converters  202 - 206  are connected in parallel and operate 120° out of phase between the three modules. Therefore, a single input voltage Vac can be used to supply all three of the modular converters  502 - 506  via voltage lines Ln 1 -Ln 3  and neutrals N 1 -N 3 , respectively. Each of the modular converters  502 - 506  can be provided to operate phase shifted by 0°, 120°, and 240°. In other words, pulses of the second module are phase-shifted by 120 degrees compared to the first module. This injects an instantaneous input current which has its switched currents 120 degrees phase-shifted to each other and hence they cancel out effectively. 
     Each modular converter  502 - 506  will operate independently as indicated in  FIG.  1    with 50% duty ratios on the primary side H-bridges and controlled PWM switching on the secondary side H-bridges. Therefore, each modular converter  502 - 506  can independently determine an instantaneous voltage V 1 -V 3  and desired output voltage V 4 -V 6  respectively, to obtain the respective phase shift and frequency controls needed to achieve the desired output voltage V 4 -V 6  for a total summed voltage V 7 . 
     In addition, since the modular converters  502 - 506  are operating with a 120° phase shift through the control pulses of the three modules, the ripple current introduced and present through the modular system  500  is cancelled out. Therefore, a reduced filter size is used and an improved efficiency is achieved. 
       FIG.  6    is a flowchart of a method for single-phase charging using a phase modular single-stage dual-active bridge converter. As illustrated in  FIG.  5   , a modular system  500  is introduced for providing a high voltage to a load using a single phase operation.  FIG.  6    corresponds to the flowchart used for providing the voltage using the architecture of  FIG.  5    above. Method  600  can apply to any high voltage battery system that can benefit from battery charging. In addition, although a single-stage dual active bridge converter system is used herein for charging, a multi-stage, boost, buck, buck-boost, or other converter may be used. 
     In this process, method  600  begins with operation  602  where an alternating current voltage supplies a voltage to the input of the modular system  500  for conversion. The modular system  500  can be a single stage system with modular converters  502 - 506  replicated to provide a total summed high voltage for charging. 
     After the voltage is supplied to the input of the modular system  500 , method  600  continues to operation  604 , where the single voltage supplied by the Vac source is provided to each of the modular converters  502 - 506  phase shifted by 120°. Each of the modular converters  502 - 506  processes the alternating current voltage supplied through the primary side of H-bridge. In the H-bridge, the voltage supplied is rectified and converted to a pulsating DC voltage providing AC-to-DC conversion and inherent PFC. In one embodiment, the switches S 1 -S 4  on each of the converters on the primary side can operate on a 50% duty cycle. 
     Once the voltage has been converted to a pulsating DC voltage (e.g., in quasi-square wave form), method  600  continues to operation  608  where the voltage is transformed and boosted at each of the modular converters  502 - 506 . Operation  608  occurs at the secondary side of each of the modular converters  502 - 506 . First, the pulsating DC voltage arrives at the transformer that is designed with a 1:n turns ratio and takes the DC voltage (e.g., V 1 ) from the primary side and transforms it into to an increased DC voltage (e.g., nV 1 ). Then, the increased voltage pulse continues to the H-bridge switches S 5 -S 8  which controlled to operate based on a desired voltage using pulse width modulation. As an instantaneous voltage on the secondary side  108  is determined and compared to a desired voltage, the switches S 5 -S 8  are turn on and off accordingly to achieve the desired voltage level. As indicated above, control scheme  200  and block diagram  300  in conjunction with  FIGS.  2 - 3    can be used to determine the appropriate phase shift and frequency to apply to the switches S 5 -S 8  to achieve the desired voltage level. In modular system  500 , since converter modules  502 - 506  run in parallel, the voltage and/or current control is applied at each of the secondary sides  108  so as to achieve a maximum total voltage desired for charging battery V 7  (or any high powered system). 
     Once the voltage has been controlled to the desired level at each of the converter modules  502 - 506 , method  600  proceeds to operation  610  where the voltages V 4 -V 6  at the output of each modular converter  502 - 506  are summed to provide a total voltage that may be used for charging battery V 7  and/or alternatively stored in capacitor C 2 . 
     In some instances, three phase operation is needed for charging the high voltage system. In these instances, it is advantageous to have a single system that may be interchangeably used for either one phase or three phase operation.  FIG.  7    introduces three phase modular system  700  (previously, modular system  500 ) which was used for one phase operation now interconnected for three phase operation. Specifically,  FIG.  7    is a diagram illustrating a phase modular single-stage dual-active bridge converter for three-phase operation. 
     As illustrated in  FIG.  7   , the three phase modular system  700  continues the use of modular converter  100  which has been replicated three times (e.g., converters  702 - 706 ) and interconnected to provide a total summed voltage V 17  that may be stored in capacitor C 4  and used for a charging battery. Each converter  702 - 706  comprises a primary side  106  50% duty cycled PFC rectifying H-bridge and secondary side  108  pulse width modulated H-bridge. 
     The modular converter  100 , having the same topology as the single phase modular system  500  of  FIG.  5   , also includes converters  702 - 706  that have corresponding voltage lines Ln 1 -Ln 3  and neutral lines N 1 -N 3  as inputs. Like the modular system  500  in single phase operation, three phase modular system  700  will also operate by use a single neutral line that is share by all three converters  7020706  via neutral line inputs N 1 -N 3 . However, specific to the three phase operation is the use of three independent voltage sources V 1 -V 3  arriving at each of the converters  703 - 706  respectively. Therefore, unlike the single phase system  500  where a single voltage source is used for all three converters, in the three phase modular system  700 , three voltage sources V 8 -V 10  are used. Thus, each of the converters  702 - 706  will have voltage line Ln 1 -Ln 3  that feeds the corresponding converter. Because three independent voltage sources are used in the three phase modular system  700  topology, each of the voltage source V 8 -V 10  can provide a distinct alternating current voltage. However, generally in a three phase system equivalent alternating current voltages are provided that are phase shifted by 120° degrees. Therefore, in the three phase module system  700 , voltage sources V 8 -V 10  each provide an alternating current voltage, where the alternating current voltage at each voltage source V 8 -V 10  has an equivalent amplitude with a 120° offset. Since three independent sources V 8 -V 10  are used in the three phase modular system  700 , interleaving of the converters  702 - 706  is not necessary. 
     Also, as three independent voltage sources V 8 -V 10  are providing voltage to each of the converters  702 - 706 , the converters  702 - 706  can function independently. That is to say, the PFC rectification and conversion that occurs on the primary side and secondary side of each converter  702 - 706  can operate without interdependence on the other converters. For example, converter  702 , can obtain an alternating current voltage from source V 8 . The alternating current voltage can then be rectified to a pulsating DC independent of the rectification occurring in converter  704  which is using the alternating current voltage from source V 9 . Similarly, the frequency and phase shift control may be applied to converter  702  independent of the phase shift and frequency control of converter  704 . Therefore, each of the modular converters  702 - 706  can independently determine an instantaneous voltage V 11 -V 13  and desired output voltage V 14 -V 16  respectively, to obtain the respective phase shift and frequency controls needed to achieve the desired output voltage V 14 -V 16  for a total summed voltage V 17 . Therefore, the converters  702 - 704  can work independently of each other to achieve a total summed voltage V 17 . 
       FIG.  8    is a flowchart of a method for three-phase charging using a phase modular single-stage dual-active bridge converter. As illustrated in  FIG.  7   , a three phase modular system  400  was introduced for providing a high voltage to a load using a three phase operation.  FIG.  8    corresponds to the flowchart used for providing the voltage using the architecture of  FIG.  7    above. Method  800  can apply to any high voltage battery system that can benefit from battery charging. In addition, although a single-stage dual active bridge converter system is used herein for charging, a multi-stage, boost, buck, buck-boost, or other converter may be used. 
     In this process, method  800  begins with operation  802  where three distinct alternating current voltage supplies, supply a voltage to the input of the three-phase modular system  700  for conversion. The three phase modular system  700  can be a single stage system with three modular converters  702 - 706 , each receiving an alternating current voltage one of the three alternating voltage supplies V 8 -V 10 . In one embodiment, the AC voltage received at each converter is equivalent with a phase shift of 120° degrees. 
     In operation  804 , the voltage supplied at each of the converter is processed through the primary side  106  of H-bridge where the alternating current voltage V 8  is rectified and converted to a pulsating DC voltage providing AC-to-DC conversion and inherent PFC. In one embodiment, the switches S 1 -S 4  on each of the converters  702 - 706  on the primary side can operate on a 50% duty cycle. 
     In operation  806 , the pulsing AC voltage is processed through the secondary side  108  where the voltage gets transformed and boosted at each of the converters  702 - 706 . First, the pulsating AC voltage arrives at the transformer that is designed with a 1:n turns ratio and takes the AC voltage (e.g., V 8 ) from the primary side  106  and transforms it into to an increased AC voltage (e.g., nV 8 ). Then, the boosted voltage pulse continues to the H-bridge switches S 5 -S 8  which are voltage controlled using pulse width modulation. Therefore, the instantaneous voltage on the secondary side  108  relative to a desired voltage determines the switching of switches S 5 -S 8  to achieve the desired voltage level. Phase shift and frequency control can be used to determine the appropriate phase shift and frequency to apply to the switches S 5 -S 8  to achieve the desired voltage level. In three phase modular system  700 , since converter modules  702 - 706  run in parallel, the phase shift and/or frequency control is applied at each of the secondary sides  108  so as to achieve a maximum total voltage desired for charging battery V 17  (or any high powered system). 
     Once the voltage has been controlled to achieve the desired level at each of the converter modules  702 - 706 , operation  808  proceeds to provide a combined boosted voltage by summing the voltages V 14 -V 16  at the output of each converter  702 - 706 . 
     Note that the various recovery modes presented are for illustration purposes and can occur in any order. Additionally, the voltage and current ranges are also used as an illustration and can vary in range width and values. Further, the voltage flows and charge current flows in the timing diagram may also vary as the operations transition between modes. 
     Referring now to  FIG.  9   , a detailed description of an example computing system  900  having one or more computing units that may implement various systems and methods discussed herein is provided, such as the modulator  306  of the circuit  300  of  FIG.  3   . It will be appreciated that specific implementations of these devices may be of differing possible specific computing architectures not all of which are specifically discussed herein but will be understood by those of ordinary skill in the art. 
     The computer system  900  may be a computing system is capable of executing a computer program product to execute a computer process. Data and program files may be input to the computer system  900 , which reads the files and executes the programs therein. Some of the elements of the computer system  900  are shown in  FIG.  9   , including one or more hardware processors  902 , one or more data storage devices  904 , one or more memory devices  906 , and/or one or more ports  908 - 912 . Additionally, other elements that will be recognized by those skilled in the art may be included in the computing system  900  but are not explicitly depicted in  FIG.  9    or discussed further herein. Various elements of the computer system  900  may communicate with one another by way of one or more communication buses, point-to-point communication paths, or other communication means not explicitly depicted in  FIG.  9   . 
     The processor  902  may include, for example, a central processing unit (CPU), a microprocessor, a microcontroller, a digital signal processor (DSP), and/or one or more internal levels of cache. There may be one or more processors  902 , such that the processor  902  comprises a single central-processing unit, or a plurality of processing units capable of executing instructions and performing operations in parallel with each other, commonly referred to as a parallel processing environment. 
     The computer system  900  may be a conventional computer, a distributed computer, or any other type of computer, such as one or more external computers made available via a cloud computing architecture. The presently described technology is optionally implemented in software stored on the data stored device(s)  904 , stored on the memory device(s)  906 , and/or communicated via one or more of the ports  908 - 912 , thereby transforming the computer system  900  in  FIG.  9    to a special purpose machine for implementing the operations described herein. Examples of the computer system  900  include personal computers, terminals, workstations, mobile phones, tablets, laptops, personal computers, multimedia consoles, gaming consoles, set top boxes, and the like. 
     The one or more data storage devices  904  may include any non-volatile data storage device capable of storing data generated or employed within the computing system  900 , such as computer executable instructions for performing a computer process, which may include instructions of both application programs and an operating system (OS) that manages the various components of the computing system  900 . The data storage devices  904  may include, without limitation, magnetic disk drives, optical disk drives, solid state drives (SSDs), flash drives, and the like. The data storage devices  904  may include removable data storage media, non-removable data storage media, and/or external storage devices made available via a wired or wireless network architecture with such computer program products, including one or more database management products, web server products, application server products, and/or other additional software components. Examples of removable data storage media include Compact Disc Read-Only Memory (CD-ROM), Digital Versatile Disc Read-Only Memory (DVD-ROM), magneto-optical disks, flash drives, and the like. Examples of non-removable data storage media include internal magnetic hard disks, SSDs, and the like. The one or more memory devices  906  may include volatile memory (e.g., dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and/or non-volatile memory (e.g., read-only memory (ROM), flash memory, etc.). 
     Computer program products containing mechanisms to effectuate the systems and methods in accordance with the presently described technology may reside in the data storage devices  904  and/or the memory devices  906 , which may be referred to as machine-readable media. It will be appreciated that machine-readable media may include any tangible non-transitory medium that is capable of storing or encoding instructions to perform any one or more of the operations of the present disclosure for execution by a machine or that is capable of storing or encoding data structures and/or modules utilized by or associated with such instructions. Machine-readable media may include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more executable instructions or data structures. 
     In some implementations, the computer system  900  includes one or more ports, such as an input/output (I/O) port  908 , a communication port  910 , and a sub-systems port  912 , for communicating with other computing, network, or vehicle devices. It will be appreciated that the ports  908 - 912  may be combined or separate and that more or fewer ports may be included in the computer system  900 . 
     The I/O port  908  may be connected to an I/O device, or other device, by which information is input to or output from the computing system  900 . Such I/O devices may include, without limitation, one or more input devices, output devices, and/or environment transducer devices. 
     In one implementation, a communication port  910  is connected to a network by way of which the computer system  900  may receive network data useful in executing the methods and systems set out herein as well as transmitting information and network configuration changes determined thereby. Stated differently, the communication port  910  connects the computer system  900  to one or more communication interface devices configured to transmit and/or receive information between the computing system  900  and other devices by way of one or more wired or wireless communication networks or connections. Examples of such networks or connections include, without limitation, Universal Serial Bus (USB), Ethernet, Wi-Fi, Bluetooth®, Near Field Communication (NFC), Long-Term Evolution (LTE), and so on. One or more such communication interface devices may be utilized via the communication port  910  to communicate one or more other machines, either directly over a point-to-point communication path, over a wide area network (WAN) (e.g., the Internet), over a local area network (LAN), over a cellular (e.g., third generation (3G) or fourth generation (4G)) network, or over another communication means. Further, the communication port  910  may communicate with an antenna for electromagnetic signal transmission and/or reception. In some examples, an antenna may be employed to receive Global Positioning System (GPS) data to facilitate determination of a location of a machine, vehicle, or another device. 
     The computer system  900  may include a sub-systems port  912  for communicating with one or more systems related to a vehicle to control an operation of the vehicle and/or exchange information between the computer system  900  and one or more sub-systems of the vehicle. Examples of such sub-systems of a vehicle, include, without limitation, motor controllers and systems, battery control, fuel cell or other energy storage systems or controls in the case of such vehicles with hybrid or electric motor systems, autonomous or semi-autonomous processors and controllers, steering systems, brake systems, light systems, navigation systems, environment controls, entertainment systems, and the like. 
     Note that the embodiments of the present disclosure include various operations or steps. The steps may be performed using information from hardware components, and may be embodied in hardware components or may be embodied in machine-executable instructions, which may be used to cause a general-purpose or special-purpose processor (e.g., a processing unit of the mobile device) executing the instructions to perform the steps. Alternatively, the steps may be performed by a combination of hardware, software and/or firmware. 
     While the present disclosure has been described with reference to various implementations, it will be understood that these implementations are illustrative and that the scope of the disclosure is not limited to them. Many variations, modifications, additions, and improvements are possible. More generally, implementations in accordance with the present disclosure have been described in the context of particular implementations. Functionality may be separated or combined in blocks differently in various embodiments of the disclosure or described with different terminology. These and other variations, modifications, additions, and improvements may fall within the scope of the disclosure as defined in the claims that follow.

Metadata:
Filing Date: 20190723
Publication Date: 20221227
Grant Date: 20221227
Priority Date: 20160923
Inventors: Sahoo, Ashish K.
MAZUMDAR, POORNIMA
Sun, Nancy Y.
Zahid, Zaka Ullah
LEE, DONG YOUNG
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J3/381", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/007184", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J3/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J3/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2300/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02M7/793", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2300/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J3/381", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J3/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/00716", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J3/32", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02M7/219", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/02", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2207/20", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/045", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/00716", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 67620687