VEHICLE-GRID-HOME POWER INTERFACE

Abstract

A method of operating an electric vehicle charging apparatus for a vehicle to grid interface comprising a first full bridge converter configured to convert a grid supply to a DC link and a primary full bridge converter connected to the DC link and configured to provide an output alternating current for use in vehicle charging. The method includes detecting a charging power requirement for a vehicle; determining a required voltage for the DC link to enable the converter to supply power for satisfying the charging power requirement when operating at full duty cycle; operating the primary full bridge converter at full duty cycle; controlling the voltage of the DC link to the required voltage.

Claims

1. A method of operating an electric charging apparatus comprising a first full bridge converter configured to convert a grid supply to a DC link and a primary full bridge converter connected to the DC link and configured to provide an output alternating current for use in charging, the method comprising: detecting a charging power requirement for a battery to be charged by the apparatus; determining a required voltage for the DC link to enable the primary full bridge converter to supply power satisfying the charging power requirement when the primary full bridge converter is operating at full duty cycle; operating the primary full bridge converter at full duty cycle; and controlling the voltage of the DC link to the required voltage.

2. The method of claim 1 further comprising charging the battery wirelessly.

3. The method of claim 2 further comprising providing a bi-directional wireless coupling between the primary full bridge converter and the battery.

4. The method of claim 2 further comprising supplying the output of the primary full bridge converter to a coil for coupling to a further coil for inductive coupling to enable wireless power transfer.

5. The method of claim 1 further comprising: detecting a reactive power requirement of a load connected to the grid, and operating the first full bridge converter to compensate for the reactive power requirement.

6. The method of claim 1 further comprising: detecting a power requirement of the load or grid, and operating the first and primary full bridge converters to supply power from the battery to the load and/or the grid.

7. The method of claim 3 further comprising: controlling the primary full bridge converter and a secondary full bridge converter associated with the battery to control bi-directional wireless power transfer between the grid, load and battery.

8. The method of claim 7 further comprising operating the primary and secondary converters at a relative phase angle (θ) to direct power flow to or form the battery.

9. The method claim 1 further comprising operating the duty cycle (φp) of the primary converter at 180 degrees.

10. The method of claim 7 further comprising operating the duty cycle (φs) of the secondary converter to control power flow.

11. The method of claim 1 further comprising: calculating an instantaneous load power for a load connected to the grid, determining a reference current for supply by the first full bridge converter, and controlling switches of the first full bridge converter to provide compensation.

12. A method of operating an electric charging apparatus comprising a first full bridge converter connected to a utility grid and configured to convert a grid supply to a DC link and a second full bridge converter connected to the DC link and configured to provide an output alternating current for use in battery charging, the method comprising: detecting a reactive power requirement of a load connected to the grid; and operating the first full bridge converter to compensate for the reactive power requirement.

13. The method of claim 12 further comprising detecting a charging power requirement for a battery to be charged by the apparatus, and operating the second converter to charge the battery.

14. The method of claim 12 further comprising: detecting a power requirement of the load or grid, and operating the first and second full bridge converters to supply power from the battery to the load and/or the grid.

15. A method of operating an electric charging apparatus comprising a first full bridge converter connected to a utility grid and configured to convert a grid supply to a DC link and a second full bridge converter connected to the DC link and configured to provide an output alternating current for use in battery charging, the method comprising: detecting a power requirement of the load or grid and operating the first and second full bridge converters to supply power from the battery to the load and/or the grid.

16. A vehicle-grid-home interface comprising a controller configured or operable to perform the method according to claim 1, wherein the battery comprises an electric vehicle battery.

17. A power and quality control converter comprising: a full bridge converter; an input coupled to a utility power supply; an output coupled to a wireless power transfer system; and a controller configured to determine a required instantaneous DC voltage for the output, and adaptively control the full bridge converter at the determined required DC voltage.

18. The power and quality control converter of claim 17 configured to: detect a reactive power requirement of a load connected to the utility power supply, and operate the first full bridge converter to compensate for the reactive power requirement.

19. The power and quality control converter of claim 17 configured to detect a power requirement of the load or utility supply and operate the first and second full bridge converters to supply power from the battery to the load and/or the utility supply.

20. The power and quality control converter of claim 17 configured to calculate an instantaneous load power for a load connected to the utility supply, determine a reference current for supply by the first full bridge converter, and control switches of the first full bridge converter to provide compensation.

21. The power and quality control converter of claim 17 wherein the wireless power transfer system comprises a wireless battery charging system.

22. The method of claim 15 further comprising operating the apparatus in an islanding mode in which power is supplied from the battery to the load.

23. The method of claim 15 further comprising operating the apparatus to provide compensation for the load.

24. The method of claim 8 wherein θ is +90 degrees or −90 degrees.

25. The method of claim 1 wherein the battery comprises an electric vehicle battery.

Description

DRAWING DESCRIPTION

[0083] FIG. 1 is a vehicle-grid-home VGH unit-based system

[0084] FIG. 2 is a circuit topology for a VW-VGH-PI system

[0085] FIGS. 3A, 3B, 3C, 3D, and 3E show operating modes for the system of FIG. 1

[0086] FIG. 4 is a simplified circuit schematic for a BD-WPT system

[0087] FIG. 5 is a plot of power, input voltage and the primary converter control parameter

[0088] FIG. 6A shows a waveform for a conventional WPT control method with high DC voltage

[0089] FIG. 6B shows a waveform for the adaptive DC control method with low DC voltage disclosed herein

[0090] FIG. 7 is a plot of V.sub.DC(PQCC) in terms of P.sub.V and Q.sub.L

[0091] FIG. 8 is a diagram of a controller

[0092] FIG. 9A shows steady state waveforms of the proposed system from VG2H to islanding mode

[0093] FIG. 9B shows steady state waveforms of the proposed system from VG2H to G2HV

[0094] FIG. 9C shows steady state waveforms of the proposed system from V2HG to V2H

[0095] FIG. 10A shows dynamic waveforms of a proposed VW-VGH-PI system under G2VH mode, including dynamic waveforms of v.sub.G, i.sub.G, i.sub.L and i.sub.si

[0096] FIG. 10B shows dynamic waveforms of a proposed VW-VGH-PI system under G2VH mode, including dynamic waveforms of v.sub.si, i.sub.si, v.sub.pi and i.sub.pi

[0097] FIG. 10C shows steady-state waveforms of a proposed VW-VGH-PI system under G2VH mode, including steady-state waveforms for P.sub.V=200 W

[0098] FIG. 10D shows steady-state waveforms of a proposed VW-VGH-PI system under G2VH mode, including steady-state waveforms for P.sub.V=350 W

[0099] FIG. 11A shows dynamic waveforms of a proposed VW-VGH-PI system under VG2H mode, including dynamic waveforms of v.sub.G, i.sub.G, i.sub.L and i.sub.si

[0100] FIG. 11B shows dynamic waveforms of a proposed VW-VGH-PI system under VG2H mode, including dynamic waveforms of v.sub.si, i.sub.si, v.sub.pi and i.sub.pi

[0101] FIG. 11C shows steady-state waveforms of a proposed VW-VGH-PI system under VG2H mode, including steady-state waveforms for P.sub.V=−200 W

[0102] FIG. 11D shows steady-state waveforms of a proposed VW-VGH-PI system under VG2H mode, including steady-state waveforms for P.sub.V=−350 W

DETAILED DESCRIPTION

[0103] FIGS. 1 and 2 show a system topology, generally referenced 1, for a vehicle-home-grid system, which will be referred to generally herein as a Versatile Wireless Vehicle-Grid-Home Power Interface (VW-VGH-PI) system. The utility supply (or grid, or mains) 2 supplies power at a mains frequency (for example 50 or 60 Hz) at voltage v.sub.G and current i.sub.G. Loads 4, which in the example illustrated comprises home or household or local loads are electrically connected to the grid, drawings current i.sub.L at voltage v.sub.G. The loads 4 may be, and are typically, non-linear.

[0104] A first full bridge converter, referred to herein as a power & quality control converter (PQCC) has an input 5 coupled to the grid 1, and an output 6 coupled to a wireless power transfer system (BD-WPT). In this example the BD-WPT is a bi-directional wireless power transfer system. In some other examples it is possible that the WPT is uni-directional. It will be understood by those skilled in the art that the WPT system could be replaced by a wired charging system in which a full bridge converter supplies current to an isolating transformer, and another converter associated with the vehicle converts the alternating current to a direct current for charging (or supplying power back to the grid/load). Also, although a series tuned compensation network is shown in FIG. 2, other networks may be used, for example parallel tuned networks.

[0105] The PQCC comprises switches S.sub.11 S.sub.12 S.sub.13 and S.sub.14 arranged in a full bridge configuration. A coupling component or network such as inductor L.sub.c is connected (in this example in series) with the grid to reduce the current ripple. A parallel capacitor C.sub.c is used in this example to maintain the output voltage under islanding mode. A DC-link capacitor C.sub.DC is designed to maintain the DC voltage of the DC link at the output 6 at or under a satisfactory voltage ripple. Voltage v.sub.conv is the voltage across the input of the bridge of the PQCC. P.sub.L, Q.sub.L, and S.sub.Lh are load active, reactive and harmonic power, respectively, and Pv is the active power received from or supplied to the BD-WPT system. PQCC is controlled to produce current i.sub.c at V.sub.conv to supply required P.sub.V, Q.sub.L, and S.sub.Lh.

[0106] In the BD-WPT module, the primary side converter derives power from the grid through PQCC and is fed by the output DC voltage V.sub.DC while the secondary side converter is considered to be connected to a load such as a battery. This is represented in the FIG. 2 as an EV and represented by an individual DC source V.sub.out to either store or retrieve energy. The primary and secondary side coils, represented by self-inductances L.sub.pi and L.sub.si, are separated by an air-gap, but magnetically coupled through mutual inductance M. The primary and secondary side series connected capacitors C.sub.pi and C.sub.si are designed to minimize the reactive power requirement in the BD-WPT.

[0107] PQCC is used to support the reactive and harmonic power (Q.sub.L and S.sub.Lh) compensation of the nonlinear household loads while meeting the active power supply/demand in accordance with P.sub.G=(P.sub.V−P.sub.L). The BD-WPT module is used to transfer (preferably bi-directionally) the active power Pv under Islanding mode, V2H mode, G2VH mode, VG2H and V2HG and any other possible modes as required. These operation modes are illustrated in FIGS. 3A-3E. In all modes, both the reactive and harmonic power of the household loads are to be, or can be, supplied by the PQCC, subject to its capacity. The EV acts as an active load to absorb active power (P.sub.V>0) from the power gird in the G2VH mode. In contrast, the EV is represented as a DC supply to deliver power (P.sub.V<0) to household loads in the VG2H mode. Also, the EV power can flow into another EV through VW-VGH-PIs. Those skilled in the art will understand that the monitored or sampled parameters, such as those shown and described in this document, but in particular those identified in the control system shown in FIG. 8 below, may be used to determine an appropriate operating mode (as per FIGS. 3A-3E) for the system, and control the system to operate in that mode, as described further below.

[0108] As shown in FIG. 4, the BD-WPT module employs a full-bridge converter on the primary side to generate high-frequency current in the primary coil/track from the DC link voltage V.sub.DC. The full-bridge converter employed on the secondary side can be connected to active loads such as EVs, to enable supply or retrieval of energy.

[0109] Based on FIG. 4, the input and output currents can be expressed as:

[00001]$\begin{array}{cc}{I}_{pi}=\frac{V_{pi}-V_p}{j{\omega }_s{L}_{pi}-1/j{\omega }_s{C}_{pi}}=\frac{V_{pi}-j{\omega }_s{\mathrm{MI}}_{si}}{j{\omega }_s{L}_{pi}-1/j{\omega }_s{C}_{pi}}& \left(1\right)\end{array}$$\begin{array}{cc}{I}_{si}=\frac{V_{si}-V_s}{j{\omega }_s{L}_{si}-1/j{\omega }_s{C}_{si}}=\frac{V_{si}-j{\omega }_s{\mathrm{MI}}_{pi}}{j{\omega }_s{L}_{si}-1/j{\omega }_s{C}_{si}}& \left(2\right)\end{array}$

where V.sub.p and V.sub.s are voltages induced in the primary and secondary coils, respectively, and M is the mutual inductance. The voltages V.sub.pi and V.sub.si produced by the converters from V.sub.DC and V.sub.out, respectively, can be expressed as:

[00002]$\begin{array}{cc}{v}_{\mathrm{pi}}\left(t\right)=\frac{4}{\pi }{V}_{\mathrm{DC}}\underset{n=1,3,.Math.}{\overset{\infty }{.Math.}}\frac{1}{n}\cos \left(n{\omega }_{s}t\right)\sin \left(\frac{n{\phi }_p}{2}\right)& \left(3\right)\end{array}$$\begin{array}{cc}{v}_{\mathrm{si}}=\frac{4}{\pi }{V}_{out}\underset{n=1,3,.Math.}{\overset{\infty }{.Math.}}\frac{1}{n}\cos \left(n{\omega }_{s}t+n\theta \right)\sin \left(\frac{n{\phi }_s}{2}\right)& \left(4\right)\end{array}$

[0110] where n is the harmonic number, φ.sub.p is the primary side phase shift modulation, φ.sub.s is the secondary side phase shift modulation and θ is the relative phase angle between the two voltages produced by converters, and ω.sub.s is the angular switching frequency of both the primary and secondary converters which is equal to the angular resonant frequency ω.sub.r, which can be expressed as:

[00003]$\begin{array}{cc}{\omega }_r={\omega }_s=\frac{1}{\sqrt{L_{\mathrm{pi}}.Math.C_{\mathrm{pi}}}}=\frac{1}{\sqrt{L_{\mathrm{si}}.Math.C_{\mathrm{si}}}}& \left(5\right)\end{array}$

[0111] The power flow on the EV side can be expressed by:

[00004]$\begin{array}{cc}{P}_V\left({\phi }_p,{\phi }_s,\theta \right)=P_{p_{-}1}\left({\phi }_p,{\phi }_s,\theta \right)=\frac{1}{2}\mathrm{Re}\left(V_{\mathrm{pi}\_1}{I}_{\mathrm{pi}\_1}^{*}\right)=-\frac{8}{{\pi }^2}\frac{1}{{\omega }_{s}M}{V}_{DC}{V}_{out}\sin \left(\frac{{\phi }_p}{2}\right)\sin \left(\frac{{\phi }_s}{2}\right)\sin \left(\theta \right)& \left(6\right)\end{array}$$\begin{array}{cc}{Q}_V\left({\phi }_p,{\phi }_s,\theta \right)=Q_{p_{-}1}\left({\phi }_p,{\phi }_s,\theta \right)=\frac{1}{2}\mathrm{Im}\left(V_{\mathrm{pi}\_1}{I}_{\mathrm{pi}\_1}^{*}\right)=\frac{8}{{\pi }^2}\frac{1}{{\omega }_{s}M}{V}_{DC}{V}_{out}\sin \left(\frac{{\phi }_p}{2}\right)\sin \left(\frac{{\phi }_s}{2}\right)\cos \left(\theta \right)& \left(7\right)\end{array}$

[0112] The purpose of the BD-WPT controller is to control Pv at its reference value, while minimizing its reactive power requirement. In (6) and (7), the reactive power components on both sides of the system can be minimized (Q.sub.V=0) by keeping the relative phase angle θ between the voltages of primary and the secondary-side converters to be either +90° or −90°. The direction of power flow can be controlled through the sign of the relative phase angle. Apart from θ, both φ.sub.p and φ.sub.s as well as ω.sub.s can be used to control the active power transfer. In this example, φ.sub.p is set as the first priority for active power control, while φ.sub.s is set to 180°. Based on (6), the relationship among the P.sub.V, V.sub.DC and φ.sub.p can be shown as in FIG. 5.

[0113] As evident from FIG. 5, P.sub.V can be regulated through controlling phase shift φ.sub.p or input voltage V.sub.DC. Conventionally, P.sub.V is regulated by controlling φ.sub.p while V.sub.DC is set to a fixed value. However, the proposed PQCC employs an adaptive DC-link voltage control method to regulate P.sub.V by varying V.sub.DC, as appropriate, and thereby lowers switching losses and harmonic distortion in PQCC as well as in the primary converter of the BD-WPT module. The comparison between a conventional control method using φ.sub.p and the proposed control method is made with reference to FIGS. 6A and 6B.

[0114] Conventionally, as in FIG. 6A, V.sub.DC is designed to be a fixed value V.sub.DC(WPT)_conv, and P.sub.V is regulated by indirectly controlling V.sub.DC(WPT)_conv through φ.sub.p (effectively the duty cycle) of the primary side converter of the WPT module.

[0115] In contrast, as shown in FIG. 6B, the proposed adaptive method regulates P.sub.V by directly controlling V.sub.DC=V.sub.DC(WPT)_adap through PQCC while keeping φ.sub.p of the primary side converter of the WPT module at 180°, which corresponds to maximum duty cycle of 100%. The V.sub.DC(WPT)_adap is designed for the condition that corresponds to either supply or absorption of maximum P.sub.V.

[0116] The switching loss of any semiconductor device in PQCC can be approximated as:

[00005]$\begin{array}{cc}{P}_{sw}\left(V_{DC}\right)=V_{DC}{I}_c{f}_{sw}\left[\frac{1}{8}{t}_{rN}\frac{I_c}{I_{CN}}+t_{\mathrm{fN}}\left(\frac{1}{3\pi }+\frac{1}{24}\frac{I_c}{I_{CN}}\right)\right]& \left(8\right)\end{array}$

[0117] where V.sub.DC, I.sub.C, I.sub.CN, t.sub.rN, t.sub.fN, and f.sub.sw are the DC-link voltage, PQCC output current, rated current, rated rise time, rated fall time, and switching frequency, respectively. As evident from (8), V.sub.DC is proportional to the switching loss, for any given I.sub.C which is injected in to the grid based on active, reactive and harmonic power requirements. Thus by lowering V.sub.DC as appropriate using the adaptive control concept, the switching loss of PQCC can be reduced.

[0118] Under the conditions specified for PQCC in (8), the same power P.sub.V(V.sub.DC, φ.sub.p) in (6) must be transferred through the primary side converter of the BD-WPT module. Then considering the same power transfer through both the conventional constant DC link voltage method and the new adaptive DC-link control, the following expression can be obtained:

[00006]$\begin{array}{cc}{P}_V\left(V_{DC}=V_{\mathrm{DC}\left(\mathrm{WPT}\right)\_\mathrm{conv}},{\phi }_p\right)=P_V\left(V_{\mathrm{DC}\left(\mathrm{WPT}\right)\_\mathrm{adap}},{\phi }_p={180}^o\right)& \left(9\right)\end{array}$$\begin{array}{cc}{V}_{\mathrm{DC}\left(\mathrm{WPT}\right)\_\mathrm{conv}}\sin \left(\frac{{\phi }_p}{2}\right)=V_{\mathrm{DC}\left(\mathrm{WPT}\right)\_\mathrm{adap}}& \left(10\right)\end{array}$

[0119] Accordingly, based on (6) and (8), the switching loss ratio between the conventional method and proposed method of the primary side BD-WPT converter can be given as (11).

[00007]$\begin{array}{cc}\frac{P_{\mathrm{sw}\_\mathrm{conv}}}{P_{sw}}=\frac{1}{\sin \left(\frac{{\phi }_p}{2}\right)}& \left(11\right)\end{array}$

[0120] A smaller φ.sub.p in (11) indicates that the conventional method uses high DC link voltage to transfer low P.sub.V, incurring high switching losses but with adaptive control the switching loss would be only a fraction of the conventional switching loss. Moreover, the primary side BD-WPT converter is always operated with full duty cycle and enables operation with approximate soft-switching. Consequently the switching losses are further reduced and in addition to lowering the harmonic distortion.

[0121] According to (6) and under the conditions of φ.sub.p=φ.sub.s=180° and θ=+90° or −90°, the maximum DC-link voltage that is required for the BD-WPT module is calculated as:

[00008]$\begin{array}{cc}{V}_{\mathrm{DC}\left(\mathrm{WPT}\right)\_\mathrm{adap}}=.Math.\frac{{\pi }^2{\omega }_s{\mathrm{MP}}_V}{8V_{out}}.Math.& \left(12\right)\end{array}$

[0122] The the DC-link voltage given in (12) is adaptively controlled by PQCC in accordance with the reference P.sub.V. However in addition to the maximum V.sub.DC voltage specified in (12) that satisfies the BD-WPT module requirement, there is also a minimum V.sub.DC voltage, represented by V.sub.DC(PQCC), at which PQCC is always guaranteed to supply the AC grid with the required P.sub.V, Q.sub.L and S.sub.Lh. Based on FIG. 2, the fundamental component of the voltage produced by PQCC can be expressed as:

[00009]$\begin{array}{cc}{\stackrel{.fwdarw.}{V}}_{\mathrm{convf}}={\stackrel{.fwdarw.}{V}}_G+X_{Lc}.Math.{\stackrel{.fwdarw.}{I}}_{\mathrm{cf}}=V_G+j\omega L_c.Math.\left(\frac{P_V-j{Q}_L}{V_G}\right)=j\frac{\omega L_c{P}_V}{V_G}+\left(V_G+\frac{\omega L_c{Q}_L}{V_G}\right)& \left(13\right)\end{array}$

[0123] From (13), the minimum required fundamental DC-link voltage can be obtained as:

[00010]$\begin{array}{cc}{V}_{\mathrm{DCf}\left(\mathrm{PQCC}\right)}=\sqrt{2}{V}_{conv}=\sqrt{2}\sqrt{{\left(\frac{\omega L_c{P}_V}{V_G}\right)}^2+{\left(V_L+\frac{\omega L_c{Q}_L}{V_G}\right)}^2}& \left(14\right)\end{array}$

[0124] From (14) and parameters in Table I, the requirement of V.sub.DC(PQCC) can be determined, and as evident from FIG. 7, the minimum fundamental DC-link voltage V.sub.DC(PQCC) depends on the active and reactive power supplied by the PQCC.

[0125] To satisfy harmonic power requirement S.sub.Lh, the harmonic component of DC link voltage should be:

[00011]$\begin{array}{cc}{V}_{\mathrm{DCh}\left(\mathrm{PQCC}\right)}=\sqrt{2}{V}_{convh}\approx \sqrt{2}\sqrt{\underset{n=1}{\overset{n=N}{.Math.}}{\left(n\omega L_c.Math.I_{Ln}\right)}^2}& \left(15\right)\end{array}$

[0126] where n is the harmonic order, N is the maximum harmonic selected depending on the application, nωL.sub.c is the harmonic impedance, I.sub.Ln is the harmonic load current. Hence, the total required DC link voltage of PQCC can be expressed as:

V.sub.DC(PQCC)=√{square root over (V.sub.DCf(PQCC).sup.2+V.sub.DCh(PQCC).sup.2)}  (16)

[0127] The final DC-link voltage can be determined by selecting the maximum of the two values of V.sub.DC(WPT)_adap and V.sub.DC(PQCC).

[0128] The system shown in FIG. 1 is controlled using a controller or control module 10 configured as shown in FIG. 8. The controller can be provided in two parts, a first part 52 which is a controller for the PQCC, and a second part 54 which is a controller for the WPT module. In an embodiment the PQCC may be provided as a separate unit with a controller 11 to enable it to be connected to an existing WPT module which may have a separate controller or controllers 12 and 13. It will also be seen that the PQCC may be provided in combination with WPT apparatus i.e. the WPT apparatus may include the PQCC. The controller may be provided as one or more processors programmed to perform the control functions shown in FIG. 8 and as disclosed herein. Communication is provided if necessary between the control modules 10, 11, 12, 13. Also, communication means 14 can be provided to allow the system 1 to communicate with a grid or similar controller which may be operated by a utility supply entity. Thus, if demand on the grid needs to be reduced, this may be communicated to the controller 10, so that vehicle charging for example, can be reduced, or additional compensation may be provided.

[0129] A control strategy and system for the adaptive DC-link voltage control will now be provided, and disclosed with reference to the controller of FIG. 8.

[0130] In FIG. 8, the change of P.sub.V* is mainly used to automatically determine the transitions between modes. The P.sub.V* is from the gird controller or EV users.

[0131] In one example the single phase PQ method is used to implement the controller. This involves implementing an instantaneous active and reactive current P-Q controller for the regulation of current i.sub.C. Specifically to track the reference value i.sub.C*, the PQCC controller generates the current i.sub.C by using pulse width modulation control, such as current hysteresis pulse width modulation (PWM) control. In this example the hysteresis PWM is selected due to its simplicity of implementation, fast dynamic response, and good current limiting capability. The reference i.sub.C* can thus be calculated as:

[00012]$\begin{array}{cc}{i}_c^{*}=\frac{1}{v_G^2+{\left(v_G^D\right)}^2}\left[-v_G.Math.\left({\tilde{p}}_L+P_V^{*}+p_{DC}\right)+v_G^D.Math.q_L\right]& \left(17\right)\end{array}$

[0132] where v.sub.G and v.sub.G.sup.D are the grid voltage and instantaneous π/2 lag of load voltage; P.sub.V* is the reference active power from the BD-WPT module; p.sub.DC is the DC controlled required active power; p.sub.L and q.sub.L are the load instantaneous active and reactive current, which contain both DC components and AC components. The AC component {tilde over (p)}.sub.L is obtained by passing p.sub.L through a low pass filter (LPF) and subsequent subtraction. In (17), p.sub.L, q.sub.L and p.sub.DC can be expressed as:

[00013]$\begin{array}{cc}\left[\begin{array}{c}{p}_L\\ q_L\end{array}\right]=\{\begin{array}{cc}{v}_G& v_G^D\\ -v_G^D& v_G\end{array}].Math.\left[\begin{array}{c}{i}_L\\ i_L^D\end{array}\right]& \left(18\right)\end{array}$$\begin{array}{cc}{p}_{DC}=k_p.Math.\left(V_{DC}-V_{DC}^{*}\right)& \left(19\right)\end{array}$

[0133] where i.sub.L and i.sub.L.sup.D are the load current and instantaneous π/2 lag of load current, V.sub.DC and V.sub.DC* are the DC-link voltage and its reference value, k.sub.p is the proportional gain control. The reference V.sub.DC* is obtained by selecting maximum value of V.sub.DC(PQCC)* and V.sub.DC(BD-WPT)* by using (16) and (12) with P.sub.V=P.sub.V*, respectively. The instantaneous expressions of V.sub.DC(PQCC)* and V.sub.DC(WPT)* are obtained by substituting P.sub.V=P.sub.V* based on (14) and (12) and given as:

[00014]$\begin{array}{cc}{V}_{{\mathrm{DC}\left(\mathrm{PQCC}\right)}^{=}}^{*}\sqrt{2}\text{⁠}\sqrt{{\left(\frac{\sqrt{2}\omega L_c{P}_V^{*}}{\sqrt{v_G^2+{\left(v_G^D\right)}^2}}\right)}^2+{\left(\frac{\sqrt{v_G^2+{\left(v_G^D\right)}^2}}{\sqrt{2}}+\frac{\sqrt{2}{L}_c.Math.{\overline{q}}_L}{2\sqrt{v_G^2+{\left(v_G^D\right)}^2}}\right)}^2+\underset{n=1}{\overset{n=N}{.Math.}}{\left(n\omega L_c.Math.I_{Ln}\right)}^2}& \left(20\right)\end{array}$$\begin{array}{cc}{V}_{\mathrm{DC}\left(\mathrm{WPT}\right)\_\mathrm{adap}}^{*}=.Math.\frac{{\pi }^2{\omega }_s{\mathrm{MP}}_V^{\star }}{8V_{out}}.Math.& \left(21\right)\end{array}$

[0134] Finally, V.sub.DC* is obtained by selecting the maximum value of V.sub.DC(PQCC)* in (18) and V.sub.DC* in (19) as:

V*.sub.DC=Max(V*.sub.DC(PQCC),V*.sub.DC(WPT)_adap)  (22)

[0135] According to FIG. 8, the reference DC-link voltages (V.sub.DC(PQCC)* and V.sub.DC(WPT)_adap*) are instantaneously calculated using (20) and (21) for PQCC and the BD-WPT module, respectively. Then the maximum of these two voltages is taken as the final value of V.sub.DC* as per (22). This is followed by the use of (19) to calculate the required active power p.sub.DC for DC-link voltage control, and the use of (18) to calculate the load reactive power q.sub.L and active power p.sub.L. The LPF and (17) are used to transform the load reactive power, harmonic power, reference active power and p.sub.DC to i.sub.c*. To generate i.sub.c, the switching signals of the full-bridge converter of PQCC are derived using PWM control and comparing i.sub.c with i.sub.c*.

[0136] For the control of BD-WPT module, the active power P.sub.V is controlled through φ.sub.p and φ.sub.s and θ is used to control the direction of the active power flow. Phase shifts φ.sub.p and φ.sub.s can be generated using PI or PID controllers; PID.sub.1 and PID.sub.2. If V.sub.DC(WPT)_adap*>V.sub.DC(PQCC)*, the BD-WPT module is operated at full duty cycle with φ.sub.p=φ.sub.s=180°. In contrast, if V.sub.DC(WPT)_adap*≤V.sub.DC(PQCC)*, then active power P.sub.V is regulated at its reference P.sub.V* by controlling φ.sub.p and φ.sub.s to be within ≤180°.

[0137] Simulations have been performed to validate the proposed concept, and Table 1 shows the parameters used for the validation.

TABLE-US-00001 TABLE 1 System Parameter Value AC gird V.sub.G , f.sub.sys 65 V, 50 Hz PQCC L.sub.c,, C.sub.c 10 mH, 10 μF f.sub.sw 10 kHz C.sub.DC 660 μF V.sub.DC Adaptively controlled BD-WPT module L.sub.pi, (or L.sub.si) 193 μH C.sub.pi, (or C.sub.si) 0.195 μF V.sub.out 130 V M, k 59.5 × 10 μH, 0.31 f.sub.s 85 kHz

[0138] FIGS. 9A-9C show the dynamic performance of the proposed VW-VGH-PI system under different modes.

[0139] FIG. 9A shows the proposed VW-VGH-PI system is transferring from VG2H mode to the islanding mode at t=80 ms. Initially the system operates in the VG2H mode, and the grid side power factor and total harmonic distortion, given as PF.sub.G and THD.sub.iG, are controlled to be unity and <5% while transferring active power P.sub.V of 250 W from the EV to the grid through PQCC to meet the load demand of i.sub.L=7.5 A with a reduced grid current of 3.3 A. In the islanding mode (without the grid supply) v.sub.G is generated by the proposed system through the proposed voltage controller. As the AC grid side does not supply any power, the PQCC current i.sub.c is equal to i.sub.L, and the load demand is met by the EV through PQCC.

[0140] FIG. 9B shows the transition of the proposed VW-VGH-PI system from the APF mode to the G2VH mode at t=80 ms. As expected, PF.sub.G and THD.sub.iG are maintained at unity and <5% by PQCC. In APF mode, since the reactive and harmonic powers of the load are compensated, the grid current i.sub.G is 4.2 A and is smaller than the required 6.9 A load current i.sub.L. In contrast, in G2VH mode, EV demand is met by the grid, transferring active power P.sub.V of 250 W to the EV side. Hence the grid current is increased to i.sub.G=9.2 A.

[0141] FIG. 9C shows the transition of the proposed VW-VGH-PI system from the V2HG mode to the V2H mode at t=80 ms. As expected, PQCC maintains PF.sub.G and THD.sub.iG at unity and <5%. Initially in the V2HG mode, PQCC transfers active power P.sub.V of 440 W from the EV to fully support the home load P.sub.L=210 W, while injecting surplus active power to the grid. Then in the V2H mode with the absence of the grid power, PQCC uses the EV to fully support the load power requirement.

[0142] FIGS. 10A-10D and FIGS. 11A-11D show the dynamic waveforms of the proposed VW-VGH-PI system with adaptive DC-link voltage-control under G2VH and VG2H modes, respectively. In FIG. 10A, the reference P.sub.V* is changed from 200 W to 350 W at t=0.2 s. Despite the change, PQCC maintains PF.sub.G and THD.sub.iG at unity and lower than 3%. To meet the increased in EV active power demand, the grid current is increased from i.sub.G=10.1 A to 12.2 A while meeting the active and reactive power demand of the load. FIG. 10B shows the increased voltage and current in the BD-WPT module that corresponds to the power increase. FIGS. 10C and 10D illustrate how the soft-switching operation is achieved with the proposed adaptive DC-link voltage control.

[0143] FIG. 11A shows the waveforms during the active power P.sub.V injection to grid from the EV is changed from 200 W to 350 W. Throughout the operation, PQCC maintains THD.sub.iG and PF.sub.G at unity and <4.6% with a load power factor PF.sub.L=0.780. With the injection of 350 W P.sub.v, the grid current i.sub.G reduces to 2.7 A from 4.6 A. FIGS. 11C and 11D show how the dc link voltage is changed from 150 V to 220 V by the adaptive controller of PQCC in accordance with the increased power flow, while facilitating near soft-switch operation.

[0144] As shown in FIGS. 11A-11D, the input and output voltage and current waveforms in BD-WPT module can be controlled by proposed control method.

[0145] Although embodiments of the invention have been described with particular application to electric vehicles, those skilled in the art will appreciate that alternative fields of application comprise, for example, portable electronic devices such as cell phones, watches, tooth brushes, and the like.

[0146] Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of “including, but not limited to”.

[0147] Where in the foregoing description, reference has been made to specific components or integers of the invention having known equivalents, then such equivalents are herein incorporated as if individually set forth.

[0148] Note that the functional blocks, features, methods, devices, and systems described in the present disclosure may be integrated or divided into different combinations of systems, devices, and functional blocks as would be known to those skilled in the art. Any suitable programming language and programming techniques may be used to implement the routines of particular implementations. Different programming techniques may be employed such as procedural or object-oriented. The routines may execute on a single processing device or multiple processors. Although the steps, operations, or computations may be presented in a specific order, the order may be changed in different particular implementations. In some implementations, multiple steps or blocks shown as sequential in this specification may be performed at the same time. Having thus described a few particular embodiments of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements as are made obvious by this disclosure are intended to be part of this description though not expressly stated herein, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only, and not limiting. The invention is limited only as defined in the following claims and equivalents thereto.