A series resonant dual active bridge power converter with constant power load stabilization

Abstract

A series-resonant dual-active-bridge (SR-DAB) converter with an interleaved integrated-bidirectional-converter (IBC) and its associated control strategy is configured to improve transient response and stabilize a converter system in the presence of an input filter and cabling. The associated control strategy incorporates three parts. A main feedback control loop regulates the output voltage based on a reference signal by adjusting the frequency and phase shift of the SR-DAB converter. Virtual impedance control and active damping is provided by a feedforward controller configured to modify the reference signal. An IBC controller includes two loops, a slower outer voltage loop and a faster inner current loop, and is configured to improve transient response. In buck mode the IBC controller stores energy on an auxiliary capacitor when the output voltage is rising and in boost mode the stored energy is returned to the load when the output voltage is falling.

Description

[0001]A SERIES RESONANT DUAL ACTIVE BRIDGE POWER CONVERTER WITH CONSTANT POWER LOAD STABILIZATION TECHNICAL FIELD The aspects of the disclosed embodiments relate generally to power conversion apparatus and more particularly to stabilizedseries resonant dual active bridge DC-DC power converters.BACKGROUND Due to their ability to operate with soft-switching and low root-mean-square (rms) current, series-resonant dual-active-bridge(SR-DAB) DC-DC power converters are often used in power conversion applications where high efficiency is required. Usinga well-designed feedback control loop to regulate the output voltage of an SRDAB converter results in a converter that acts asa constant power load (CPL).A well-regulated DC-DC power converters should, when connected to an input filter / long cable be able to produce input andoutput voltages having no low frequency oscillations across the entire range of input voltage, output voltage, and load. TheDC-DC converter should also have low component count, fast transient response, and minimum component stress under inputand output voltage steps, while providing efficient and stable bidirectional power flow. Unfortunately, when an SR-DAB converter is connected to an input filter formed by the inductance of a long cable and an input capacitor or EMI filter, substantial oscillations may result in the input and output voltages due to interaction between the input filter and the SR-DAB converter.Thus, there is a need for improved SR-DAB isolated DC-DC converters capable of damping input and output oscillations andproducing fast transient response while maintaining low component count, and bi-directional power flow. Accordingly, itwould be desirable to provide apparatus that addresses at least some of the problems described above.SUMMARYThe aspects of the disclosed embodiments are directed to a series-resonant dual-active-bridge power converter apparatus withan interleaved integrated-bidirectional-converter (IBC) and an associated control method. The disclosed embodiments provide a stabilized converter system configured to provide active damping and improved transient response without requiring additional active components, resulting in reduced switching loss, improved efficiency, and lower cost.According to a first aspect, the above and further advantages are obtained by a power converter apparatus including atransformer comprising a primary winding magnetically coupled to a secondary winding, and a resonant circuit comprising an inductor, a capacitor, and the primary winding coupled in series across a primary AC voltage. A primary full bridge switchingcircuit configured to receive an input voltage and produce the primary AC voltage is coupled to an input filter configured toreceive a DC voltage and produce the input voltage, wherein the input filter comprises a resonance frequency. An integrated bi-directional converter is coupled to the secondary winding and configured to produce an output voltage. The power converterapparatus includes a controller configured to operate the converter. The integrated bi-directional converter includes: a firstupper switch and a first lower switch coupled in series across the output voltage and forming a first switched node; a second upper switch and a second lower switch coupled in series across the output voltage and forming a second switched node; and an auxiliary capacitor, wherein the first switched node is coupled to the auxiliary capacitor through a first auxiliary inductor and the second switched node is coupled to the auxiliary capacitor through a second auxiliary inductor. The controller is configured to produce a first duty cycle for the first upper switch, and a second duty cycle for the second upper switch, based on one or more of the output voltage, an auxiliary capacitor voltage, a first auxiliary inductor current, and a second auxiliary inductor current. The first duty cycle and the second duty cycle are configured to store energy onto the auxiliary capacitorwhen the output voltage is increasing and release energy from the auxiliary capacitor when the output voltage is decreasing.In a possible implementation form, the controller includes a main control loop and a feed forward path. The main control loopis configured to receive the output voltage and a reference signal and generate a plurality of switch control signals. The pluralityof switch control signals is configured to vary a frequency of the primary AC voltage and a phase shift between the primaryAC voltage and a secondary AC voltage. The feed forward path is configured to add a feed forward signal to the referencesignal. The feed forward signal is generated by applying a band pass filter to the input voltage. The feed forward controllerprovides virtual impedance control and active damping by modifying the reference signal based on oscillations in the input voltage. In a possible implementation form, the band pass filter includes a pass band configured to pass the resonance frequency. The band pass filter essentially removes the feed forward path at steady state and provides active damping of resonance producedby the input filter during input and load variations.In a possible implementation form, the controller further includes an integrated bi-directional converter controller including an outer voltage loop configured to regulate a voltage of the auxiliary capacitor and an inner current loop configured to control current flowing through the first auxiliary inductor and the second auxiliary inductor. The dual loop IBC controller improves transient response by operating the IBC in both buck and boost mode. In a possible implementation form, a bandwidth of the outer voltage loop is lower than the resonance frequency. The slowerouter voltage loop is used to regulate the voltage of the auxiliary energy storage capacitor to half of the output voltage.In a possible implementation form, a bandwidth of the inner current loop is higher than the resonance frequency. The faster current loop improves transient response of the converter. In a possible implementation form, the inner current loop generates a current reference signal by applying a high pass filter tothe output voltage, where a passband of the high pass filter is configured to pass the resonance frequency. The band pass filteressentially removes the current control loop during steady state and engages the current loop to supress resonance inducedoscillations and improve transient response.In a possible implementation form, the input filter comprises one or more of an electromagnetic interference filter and a cablingimpedance. An important advantage of the power converter apparatus is its ability to stabilize a converter system in thepresence of inductance caused by application specific requirements such as long cabling used to supply input power.These and other aspects, implementation forms, and advantages of the exemplary embodiments will become apparent fromthe embodiments described herein considered in conjunction with the accompanying drawings. It is to be understood, however, that the description and drawings are designed solely for purposes of illustration and not as a definition of the limits of the disclosed invention, for which reference should be made to the appended claims. Additional aspects and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. Moreover, the aspects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGSIn the following detailed portion of the present disclosure, the invention will be explained in more detail with reference to theexample embodiments shown in the drawings, in which like references indicate like elements and:Figure 1 illustrates a schematic diagram of an exemplary power converter apparatus incorporating aspects of the disclosedembodiments.Figure 2 illustrated an exemplary active damping control strategy incorporating aspects of the disclosed embodiments. Figure 3 illustrates graphs of the primary operating waveforms of an exemplary power converter apparatus while operating in buck mode incorporating aspects of the disclosed embodiments. Figure 4 illustrates graphs of the primary operating waveforms of an exemplary power converter apparatus while operating in boost mode incorporating aspects of the disclosed embodiments. DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS Figure 1 illustrates a schematic diagram of an exemplary power converter apparatus 100 incorporating aspects of the disclosed embodiments. The aspects of the disclosed embodiments are directed to a series-resonant dual-active-bridge power converter apparatus with an interleaved integrated-bidirectional-converter (IBC) and an associated control method. The disclosed embodiments provide a stabilized converter system configured to provide active damping and improved transient response without requiring additional active components, resulting in reduced switching loss, improved efficiency, and lower cost.In one embodiment, as shown in Figure 1, the power converter apparatus 100 includes a transformer (T) with a primary winding110 magnetically coupled to a secondary winding 112. A resonant circuit (Z) with an inductor (Lr), a capacitor (Cr), and theprimary winding 110 is coupled in series across a primary AC voltage (vp). A primary full bridge switching circuit 108 isconfigured to receive an input voltage (Vin) and produce the primary AC voltage (vp). An input filter 106 is configured to receive a DC voltage (Vdc) and produce the input voltage (Vin). The input filter 106 has a resonance frequency (ωin).In one embodiment, an integrated bi-directional converter 104 is coupled to the secondary winding 112 and is configured toproduce an output voltage (Vo). The integrated bi-directional converter (104) includes a first upper switch (S5) and a firstlower switch (S6) coupled in series across the output voltage (Vo) and forming a first switched node 114. a second upper switch (S7) and a second lower switch (S8) coupled in series across the output voltage (Vo) and forming a second switched node 116.The first switched node 114 is coupled to an auxiliary capacitor (Cb) through a first auxiliary inductor (Lb1). The secondswitched node 116 is coupled to the auxiliary capacitor (Cb) through a second auxiliary inductor (Lb2).A controller 118 is configured to produce a first duty cycle (Ds5) for the first upper switch (S5), and a second duty cycle (Ds7)for the second upper switch (S7), based on one or more of the output voltage (Vo), an auxiliary capacitor voltage (VCb), a firstauxiliary inductor current (iLb1), and a second auxiliary inductor current (iLb2). The first duty cycle (Ds5) and the second duty cycle (Ds7) are configured to store energy onto the auxiliary capacitor (Cb) when the output voltage (Vo) is increasing and release energy from the auxiliary capacitor (Cb) when the output voltage (Vo) is decreasing.The exemplary power converter apparatus 100 includes a series-resonant dual-active-bridge (SR-DAB) isolated DC-DC powerconverter 102 configured to receive an input power through an input filter 106. When a well-regulated SR-DAB converter iscoupled to an input filter, such as when a converter is installed in an application requiring a long cable to connect input power,the combination can become unstable due to interaction between the output impedance of the filter and the input impedanceof the converter. To stabilize an SR-DAB converter 102 in the presence of an input filter 106 the exemplary converterapparatus 100 includes an integrated bidirectional converter 104 and a controller 118 configured to implement a corresponding control scheme. The exemplary converter and corresponding control scheme can effectively stabilize the whole system and achieve improved transient response without the use of extra active components. As will be discussed further below, theexemplary power converter apparatus 100 results in faster transient response, improved efficiency, and higher power densitywith reduced cost. In the schematic diagram illustrated in Figure 1, crossed circuit lines without a dot 128 are not electrically connected, whilelines forming a tee intersection or marked with a dot 130 are electrically connected.In the exemplary converter apparatus 100, the switching devices S1, S2, S3, S4, S5, S6, S7, S8, are illustrated as metal–oxide–semiconductor field-effect transistors (MOSFET). Alternatively, any suitable type of switching device capable of switchingthe desired power at the desired frequency may be advantageously employed as the switching devices S1, S3, S3, S4, S5, S6, S7, S8, in the exemplary power converter apparatus 100.As used herein, a switch, or switching device, is referred to as on or turned on when it is conducting current, and referred toas off or turned off when it is not conducting current. Operation in the linear region between the on sand off states should beminimized to reduce switching losses.In the exemplary SR-DAB converter 102, electrical isolation between the input voltage Vinand the output voltage Voisprovided by a transformer T where the primary winding 110 is electrically isolated from and magnetically coupled to thesecondary winding 112. A resonant circuit Z, also sometimes referred to as a resonant tank, is formed by coupling a resonant inductor Lr, resonant capacitor Cr, and the primary winding 110 in series across a primary AC voltage vp. Conversion of the DC input voltage Vininto the primary AC voltage vpis achieved with a primary full bridge switching circuit 108 formed with four switches S1, S2, S3, S4 connected in an H-bridge configuration. Alternately turning a first pair of switches S1, S4 and a second pair of switches S2, S3 on and off converts the DC input voltage Vininto the primary AC voltage vp. On the secondary side of the transformer T, an integrated bi-directional converter (IBC) 104 is coupled to the secondary winding 112 and configured to receive the secondary AC voltage vsand produce a DC output voltage Vo. When desired, an output capacitor Co may be coupled across the DC output voltage Vo to remove high frequency distortions and smooth theoutput DC voltage Vo.In certain embodiments cabling or other components may be introduced to connect the converter to a power source. Whenthis is done, the cabling or other added components become part of the power system and are modelled in the exemplaryapparatus 100 as part of the input filter 106. For example, in one embodiment the input capacitor Cin may be part of theconverter 102 and an input inductance Lin may be introduced by cabling used to connect the converter to a power source.Unfortunately, in certain applications, interaction between the input capacitor Cin and the input inductance Lin can create aresonance frequency ωin within the input filter 106 that can adversely affect stability of the converter system.The IBC 104 includes a secondary full bridge switching circuit 126 configured to convert the secondary AC voltage vsto theDC output voltage Vo, where the full bridge switching circuit 126 includes a first upper switch S5 and a first lower switch S6coupled in series across the output voltage Vo, and a second upper switch S7 and a second lower switch S8 coupled in seriesacross the output voltage Vo. A first switched node 114 is formed between the first upper switch S5 and the first lower switchS6, and a second switched node 116 is formed between the second upper switch S7 and the second lower switch S8. The firstswitched node 114 and the second switched node 116 are coupled to the secondary AC voltage vs produced by the secondarywinding 112.An IBC is incorporated into the secondary full bridge switching circuit 126 by coupling an auxiliary capacitor Cb to the firstswitched node 114 through a first auxiliary inductor Lb1, and coupling the auxiliary capacitor Cb to the second switched node116 through a second auxiliary inductor Lb2. As will be discussed further below, the integrated bidirectional converterimproves transient response by alternately storing and releasing energy from the auxiliary capacitor Cb to / from a load through the auxiliary inductors to stabilize the output voltage. The exemplary converter apparatus 100 includes a controller 118 configured to produce control signals 120, 122 adapted tooperate the primary full bridge switching circuit 108 and the secondary full bridge switching circuit 126, respectively. Thecontroller 118 is configured to produce a first duty cycle Ds5for the first upper switch S5, and a second duty cycle Ds7for the second upper switch S7, based on one or more of the output voltage Vo, an auxiliary capacitor voltage VC, a first auxiliaryinductor current iLb1, and a second auxiliary inductor current iLb2. The controller 118 operates the IBC 104 in buck mode whenthe output voltage Vo is increasing, and in boost mode when the output voltage Vo is decreasing. In buck mode the controller118 configures the first duty cycle Ds5 and the second duty cycle Ds7 to store energy from the load onto the auxiliary capacitorCb, and when operating in boost mode the controller 118 configures the first duty cycle Ds5 and the second duty cycle Ds7 to release energy from the auxiliary capacitor Cb to the load.To improve transient response of the exemplary SR-DAB converter 102 in the presence of an input filter 106, an IBC 104 isincorporated into the secondary full bridge switching circuit 126 and a controller 118 is configured to implement acorresponding control strategy. During steady state the converter operates as a conventional SR-DAB converter with the primary full bridge switching circuit 108 and secondary full bridge switching circuit 126 operated with a fifty percent (50%)duty cycle, while power transfer from the source to the load is controlled by a phase-shift Ɵ between the primary full bridgeswitching circuit 108 and the secondary full bridge switching circuit 126.An active damping control strategy that employs feedforward of the input voltage is introduced in the exemplary powerconversion apparatus 100 provide active damping of oscillations created by the resonance ωin and to stabilize the exemplarypower converter 100 in the presence of the input filter 106. Transient response is improved by operating the secondary full bridge switching circuit 126 as an IBC 104 where control is achieved by varying a duty cycle of the secondary full bridge switching circuit 126. When the output voltage Vo is increasing, energy is absorbed by the IBC 104 and stored on the auxiliary capacitor Cb by operating the IBC 104 in buck mode, and when the output voltage Vo is decreasing, energy is returned back to the load from the auxiliary capacitor Cb by operating the IBC 104 in boost mode. Figure 2 illustrated an exemplary active damping control strategy 200 incorporating aspects of the disclosed embodiments. The exemplary active damping control strategy 200 is appropriate for use in the controller 118 to operate the exemplary power conversion apparatus 100 described above and with respect to Figure 1. As an aid to understanding, operation of the exemplaryactive damping control strategy 200 will be described with reference to the exemplary power conversion apparatus 100described above, however it should be understood that elements of the exemplary active damping control strategy may be advantageously employed with other SR-DAB converters. The controller includes a PWM generator 208 configured to receive inputs 218, 220, 222 from other parts of the controller204, 206 and generate a plurality of switch control signals 210 configured to operate the switching devices S1, S3, S3, S4, S5,S6, S7, S8, in the primary full bridge switching circuit 108 and the secondary full bridge switching circuit 126. The plurality of switch control signals 210 are configured to regulate the output voltage Vo based on the control inputs 218, 220, 222. Forexample, during steady state operation, the plurality of switch control signals 210 operate the primary full bridge switchingcircuit 108 and the secondary full bridge switching circuit 126 to create a fifty percent (50%) duty cycle in each of the primary AC voltage vp and the secondary AC voltage vs. Power transfer between the source and load is controlled by varying the phase shift ^ between the primary and secondary switching circuits 108, 126.An example of the key operating waveforms of the SR-DAB converter 102 during steady state operation are shown in Figure3 and Figure 4, where Figure 3 provides an example of buck mode (M ≤ 1) operation where the converter gain M is less thanor equal to one, and Figure 4 provides an example of boost mode (M > 1) operation where the converter gain M is greater thanone.Figure 3 illustrates graphs 300 of the primary operating waveforms of an exemplary power converter apparatus operating inbuck mode incorporating aspects of the disclosed embodiments. In the graphs 300, time is depicted along a horizontal axis 302 increasing to the right and signal magnitude is depicted along a vertical axis 304 increasing upwards. Magnitude of the primary AC voltage vp and secondary AC voltage vs is depicted in volts and primary current ip is depicted in amps along the vertical axis 304. Switching states 306 for various time intervals are shown along the time axis 302. In each time interval, switching devices in the on state are listed and switching devices not included in the list are off. The phase shift between theprimary AC voltage vp and secondary AC voltage vs is labelled on the graphs 300 as ^.Figure 4 illustrates graphs 400 of the primary operating waveforms of an exemplary power converter apparatus operating in boost mode incorporating aspects of the disclosed embodiments. Similar to the Graphs 300, time is depicted in the Graphs 400 along a horizontal axis 402 increasing to the right and signal magnitude is depicted along a vertical axis 404 increasing upwards. Magnitude of the primary AC voltage vp and secondary AC voltage vs is depicted in volts and primary current ip is depicted in amps along the vertical axis 404. Switching states 406 for various time intervals are shown along the time axis402. In each time interval, switching devices in the on state are listed and switching devices not included in the list are off.The phase shift between the primary AC voltage vp and secondary AC voltage vs is labelled on the graphs 400 as ^. Referring once again to the exemplary active damping control strategy 200 illustrated in Figure 2, the active damping control strategy 200 includes three parts. A main SR-DAB control loop 204 is used to regulate the output voltage Vo, a feed forward path 202 configured to actively damp the system, and an IBC controller 206 configured to improve transient response. The main control loop 204 is used to regulate the output voltage Vo of the SR-DAB converter 102 by comparing the output voltageVo with a reference signal Voref to create an error signal 224, and applying a control algorithm PI to create a main control signal218 used to drive the PWM converter 208. Any appropriate control algorithm capable of providing a suitably stable outputvoltage may be advantageously employed as the control algorithm PI such as a proportional plus integral algorithm (PI), aproportional plus integral plus derivative algorithm (PID), or other well-designed control algorithm. As will be discussedfurther below, the main control loop 204 is dominate during steady state operation of the converter.The optimal phase shift ^ for an SR-DAB converter to achieve soft-switching operation and minimum rms current is providedby equation 1: ^= cos^^ ^ , ^ ≤ 1^^ = cos^^^, (1)^, ^ > 1where ^is the optimal phase shift, and M is the converter gain. The PWM Generator 208 configures the plurality of switchcontrol signals 210 to achieve the phase shift ^ as shown in Equation 1.Based on the voltage error signal 224 the main controller PI adapts the main control signal 218 to vary the frequency andphase shift ^ of the primary and secondary switching circuits 108, 126 in a closed loop fashion to regulate the output voltageVo. In the embodiment illustrated in Figure 1 a proportional plus integral control algorithm is employed in the main controllerPI. Optionally, any appropriate control algorithm, such as a proportional plus integral plus derivative (PID) algorithm or otherappropriately designed control algorithm, configured to provide the desired stead state response and stability characteristics may be advantageously employed as the main controller PI. During steady state operation, output of the bandpass filter is zero, or nearly zero, leaving the output voltage Vo to be regulatedbased primarily on the reference signal Voref. During transients, resonance frequency ωin oscillations in the input voltage Vinare extracted by the bandpass filter Gff and the resulting feed forward signal Vff is added to the reference signal Voref so theoutput voltage Vofollows a time varying reference signal (Voref + Vff). By modifying the reference signal in this fashion, thenegative resistance characteristics of the constant power load are changed thereby damping the oscillations and stabilizing the entire power system.Transient behavior is enhanced by the IBC controller 206 which is configured to vary the duty cycle Ds5, Ds7 of the upperswitches S5, S7 in the secondary full bridge switching circuit 126 to appropriately control the IBC 104. In buck mode ofoperation, the IBC controller 206 stores energy in the auxiliary capacitor Cb, while in boost mode of operation the storedenergy is returned back to the load by the IBC controller 206.An overall block diagram 206 of the control scheme for the IBC 104 is illustrated in Figure 2. The IBC controller 206 includes a slower outer voltage loop 212 and a faster inner current loop 214. The current loop 214 is configured to control an auxiliarycurrent iLb by controlling its two component auxiliary currents iLb1, iLb2 flowing through each of the first auxiliary inductor Lb1and the second auxiliary inductor Lb2, respectively, while the slower voltage loop 212 is configured to regulate the voltage ofthe auxiliary energy storage capacitor Cb. The slower outer voltage loop 212 is used to regulate the voltage of the auxiliary energy storage capacitor Cb to half of theoutput voltage ^^. A bandwidth of the outer voltage loop 212 is selected to be lower than the resonance frequency ωin.Thus, while there have been shown, described, and pointed out, fundamental novel features of the invention as applied to theexemplary embodiments thereof, it will be understood that various omissions, substitutions and changes in the form and details of devices and methods illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit and scope of the presently disclosed invention. Further, it is expressly intended that all combinations of those elements, which perform substantially the same function in substantially the same way to achieve the same results, are within the scope of the invention. Moreover, it should be recognized that structures and / or elements shown and / or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested formor embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scopeof the claims appended hereto.

Claims

CLAIMS 1. A power converter apparatus (100) comprising:a transformer (T) comprising a primary winding (110) magnetically coupled to a secondary winding (112); aresonant circuit (Z) comprising an inductor (Lr), a capacitor (Cr), and the primary winding (110) coupled inseries across a primary AC voltage (vp);a primary full bridge switching circuit (108) configured to receive an input voltage (Vin) and produce the primary AC voltage (vp); an input filter (106) configured to receive a DC voltage (Vdc) and produce the input voltage (Vin), wherein the input filter (106) comprises a resonance frequency (ωin); an integrated bi-directional converter (104) coupled to the secondary winding (112) and configured to produce an output voltage (Vo); wherein the integrated bi-directional converter (104) comprises: a first upper switch (S5) and a first lower switch (S6) coupled in series across the output voltage (Vo) and forming a first switched node (114); a second upper switch (S7) and a second lower switch (S8) coupled in series across the output voltage (Vo) and forming a second switched node (116); an auxiliary capacitor (Cb), wherein the first switched node (114) is coupled to the auxiliary capacitor (Cb) through a first auxiliary inductor (Lb1) and the second switched node (116) is coupled to the auxiliary capacitor (Cb) through a second auxiliary inductor (Lb2), and acontroller (118), wherein the controller (118) is configured to produce a first duty cycle (Ds5) for the firstupper switch (S5), and a second duty cycle (Ds7) for the second upper switch (S7), based on one or more of the output voltage (Vo), an auxiliary capacitor voltage (VCb), a first auxiliary inductor current (iLb1), and a second auxiliary inductor current (iLb2), and wherein the first duty cycle (Ds5) and the second duty cycle (Ds7) are configured to store energy onto theauxiliary capacitor (Cb) when the output voltage (Vo) is increasing and release energy from the auxiliary capacitor (Cb) when the output voltage (Vo) is decreasing.

2. The power converter apparatus (100) according to claims 1 or 2 wherein the controller comprises: a main control loop (204); and a feed forward path (202), and wherein the main control loop (204) is configured to receive the output voltage (Vo) and a reference signal (Voref) and generate a plurality of switch control signals (210) configured to vary a frequency of the primary AC voltage(vp) and a phase shift between the primary AC voltage (vp) and a secondary AC voltage (vs); and, the feed forward path (202) is configured to add a feed forward signal (Vff) to the reference signal (Voref), wherein the feed forward signal (Vff) is generated by applying a band pass filter (Gff) to the input voltage (Vin).

3. The power converter apparatus (100) according to any one of the preceding claims wherein the band pass filter (Gff) comprises a pass band configured to pass the resonance frequency (ωin).

4. The power converter apparatus (100) according to any one of the preceding claims wherein the controller 200 furthercomprises an integrated bi-directional converter controller (206) comprising an outer voltage loop (212) configured to regulate a voltage (VCb) of the auxiliary capacitor (Cb) and an inner current loop (214) configured to control current (ilb1, ilb2) flowing through the first auxiliary inductor (Lb1) and the second auxiliary inductor (Lb2).

5. The power converter apparatus (100) according to any one of the preceding claims wherein a bandwidth of the outer voltage loop (212) is lower than the resonance frequency (ωin).

6. The power converter apparatus (100) according to any one of the preceding claims wherein a bandwidth of the inner current loop (214) is higher than the resonance frequency (ωin).

7. The power converter apparatus (100) according to any one of the preceding claims wherein the inner current loop (214)generates a current reference signal (216) by applying a high pass filter (HPF) to the output voltage (Vo), wherein a passband of the high pass filter (HPF) is configured to pass the resonance frequency (ωin).

8. The power converter apparatus (100) according to any one of the preceding claims wherein the input filter (106) comprises one or more of an electromagnetic interference filter, and a cabling impedance.

Images