Active electronic emulation of a passive circuit component

Abstract

An electronic emulation component for actively emulating a passive electronic component such as a capacitor or inductor having a desired value, comprises a pair of terminals for connection to an external circuit and across which the desired value is to appear, a power convertor, and a passive electronic component of the type to be emulated but having a value different from the value to be emulated and isolated from the pair of terminals by the convertor.

Claims

1. An electronic emulation component for actively emulating a passive component having capacitance or inductance of a value desired to be emulated, the emulation component comprising: a pair of terminals for connection to an external circuit and across which said desired value to be emulated appears, thereby to provide said value to be emulated to said external circuit; a power convertor comprising a control unit and an emulator, the emulator for emulating said capacitance or said inductance; a controller connected to said power converter, said controller configured to provide a control signal to said power converter which control signal is a DC reference signal having a value equal to said value desired to be emulated; and a passive component having a value of capacitance or inductance smaller than said value desired to be emulated, the passive component isolated from said pair of terminals by said convertor, wherein said emulator is configured to provide an emulation of a capacitance C.sub.B at said pair of terminals by providing a DC reference voltage (v.sub.DC*) to said power convertor at a control current i.sub.C, wherein said reference voltage is given by: $v_{\mathrm{DC}}^{*}=\frac{1}{C_B}\int i_C\left(t\right)\mathrm{dt}.$

2. The electronic emulation component of claim 1, wherein said emulator is configured to provide said control signal to said power converter.

3. The electronic emulation component of claim 2, wherein said control signal is changeable, thereby to allow said electronic component to vary the value of the component being emulated.

4. The electronic emulation component of claim 1, wherein said component being emulated is one member of the group consisting of a capacitor and an inductor.

5. The electronic emulation component of claim 1 wherein said passive component isolated from said pair of terminals by said convertor has a value of capacitance or inductance which is independent of said desired value.

6. An electronic emulation component for actively emulating a passive component having capacitance or inductance of a value desired to be emulated, the emulation component comprising: a pair of terminals for connection to an external circuit and across which said desired value to be emulated appears, thereby to provide said value to be emulated to said external circuit; a power convertor comprising a control unit and an emulator, the emulator for emulating said capacitance or said inductance; a controller connected to said power converter, said controller configured to provide a control signal to said power converter which control signal is a DC reference signal having a value equal to said value desired to be emulated; and a passive component having a value of capacitance or inductance smaller than said value desired to be emulated, the passive component isolated from said pair of terminals by said convertor, wherein said emulator is configured to provide an emulation of an inductance L.sub.B at said pair of terminals by providing a DC reference current (i.sub.DC*) to said power convertor at a control current v.sub.C, wherein said reference current is given by: $i_{\mathrm{DC}}^{*}=\frac{1}{L_B}\int v_C\left(t\right)\mathrm{dt}.$

7. The electronic emulation component of claim 1, wherein said control current is calculated based on internal losses of said capacitance being emulated.

8. The electronic emulation component of claim 6, wherein said control voltage is calculated based on internal losses of said inductance being emulated.

9. The electronic emulation component of claim 1, further comprising a regulator for regulating current from the emulator to provide a control signal.

10. The electronic emulation component of claim 1, further comprising a regulator for regulating voltage from the emulator to provide a control signal.

11. The electronic emulation component of claim 9, further comprising a modulator for modulating said control signal from the regulator to provide a switching sequence for said power convertor.

12. The electronic emulation component of claim 1 connected into a power circuit.

13. The electronic emulation component of claim 12, connected across said power supply circuit to smooth ripples.

14. A method for actively emulating a first capacitance or inductance such that a value of said first capacitance or inductance appears across a pair of terminals to an external circuit, comprising: providing a pair of terminals; providing a capacitance or inductance having a second capacitance different from and smaller than said first capacitance or inductance; placing a decoupler between said pair of terminals and said capacitor; controlling said decoupler using a control signal and further controlling said decoupler using a DC reference signal having a value equal to said value of said first capacitance or inductance to appear across said pair of terminals, and wherein said control signal comprises a capacitance emulation component or an induction emulation component, wherein said capacitance or inductance emulation component is configured to provide an emulation of a capacitance or inductance C.sub.B or L.sub.B at said pair of terminals by providing a DC reference voltage or current to said decoupler at a control current or voltage i.sub.C or v.sub.C, wherein said reference voltage is given by: $v_{\mathrm{DC}}^{*}=\frac{1}{C_B}\int i_C\left(t\right)\mathrm{dt}\text{ or }{i}_{\mathrm{DC}}^{*}=\frac{1}{L_B}\int v_C\left(t\right)\mathrm{dt}.$

15. The method of claim 14, further comprising using a control signal to control said decoupler.

16. The method of claim 15, wherein said control signal comprises a capacitance or inductance emulation component.

17. The method of claim 14, wherein said capacitance or inductance emulation component comprises a value of all or part of said control signal which is based at least in part on a value of said desired capacitance or inductance.

18. The method of claim 14, wherein said control current is calculated based on internal losses of said capacitance or inductance being emulated.

19. The method of any one of claim 15, further comprising regulating current or voltage of the capacitance or inductance emulation to provide said control signal.

20. The method of claim 19, further comprising modulating said control signal to provide a switching sequence for said decoupler.

21. The method of claim 20, comprising operating said decoupler as a power converter.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

(2) In the drawings:

(3) FIG. 1 is a diagram of a prior art power using a conventional capacitor/inductor;

(4) FIG. 2 is a simplified diagram showing an electronic capacitor/inductor attached to a power supply according to the present embodiments;

(5) FIG. 3 is a simplified schematic circuit diagram of the electronic capacitor component of the present embodiments;

(6) FIG. 4A is a power-level equivalent diagram of the circuit of FIG. 3 when emulating a capacitor;

(7) FIG. 4B is a power-level equivalent diagram of the circuit of FIG. 3 when emulating an inductor;

(8) FIG. 5 is a simplified diagram of a control circuit in the electronic capacitor/inductor of FIGS. 2 and 3;

(9) FIG. 6 is a simplified flow chart illustrating a method of emulating a capacitance/inductance according to embodiments of the present invention; and

(10) FIGS. 7A and 7B are a comparative example of power regulation using a large capacitor and using emulation according to the present embodiments.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

(11) The present invention, in some embodiments thereof, relates to electronic emulation of a passive circuit component, thus an electronic capacitor or an electronic inductor, and, more particularly, but not exclusively, to a power supply provided with such an electronically emulated component.

(12) The present embodiments may replace large passive components by an electronic system, consisting of a much smaller passive component and a power electronic converter. In case of capacitors, embodiments may achieve significant reduction in the capacitance value, allowing in some cases to employ a single ceramic/film capacitor in place of a bank of electrolytic capacitors, thus leading to much higher reliability, MTBF and lifetime. In case of inductors, inductor-like operation may be achieved utilizing capacitors and electronics switches only.

(13) In the case of a capacitor/inductor, the present embodiments may provide a two-terminal device consisting of capacitor C.sub.P, power converter and control system, capable of emulating terminal behavior of any finite capacitance C.sub.B (higher or lower than C.sub.P) or finite inductance L.sub.B. Moreover, emulated capacitance/inductance value C.sub.B/L.sub.B may be instantaneously varied according to an external control signal. On the other hand, energy storage capabilities of the proposed device equal these of the capacitor C.sub.P, i.e. the value of emulated capacitance/inductance is decoupled from the device energy storage capabilities, by contrast with a regular capacitor/inductor where the two are coupled.

(14) The device of the present embodiments may replace existing capacitors/inductors, operating as short-time energy storage in a plug-and-play fashion, utilizing relatively lower capacitance thus increasing reliability and lifetime while in many cases decreasing weight and volume.

(15) The present embodiments may thus enable the weight and volume of power conversion systems to be decreased, while increasing reliability, MTBF and lifetime.

(16) For purposes of better understanding some embodiments of the present invention, as illustrated in FIGS. 2-7B of the drawings, reference is first made to the construction and operation of a power supply with a conventional capacitor/inductor as illustrated in FIG. 1.

(17) FIG. 1 illustrates the conventional situation in which a capacitor/inductor C.sub.B/L.sub.B 10 is placed across the terminals of a power convertor 12 via a DC link 14. The task of the power converter 12 is to obtain power from a source Tl, 16, and supply the power under different conditions to output terminals Tk 18 and 20.

(18) Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

(19) Reference is now made to FIG. 2, which is a simplified diagram illustrating an electronic capacitor/inductor (ECI) 30 according to a first embodiment of the present invention. The ECI 30 may be an electronic capacitance/inductance component for emulating a desired capacitance/inductance. As shown in FIG. 2 the capacitance/inductance to be emulated is that needed by power converter 32 to deal with the power source across terminals 33. The component 30 comprises a pair of terminals 34 for connection to the external circuit 32 and across which the desired capacitance/inductance appears. Capacitor Cp 36 is isolated from the pair of terminals 36 by a decoupler 38, which may itself be a power supply, as shown a DC-DC power supply and isolator.

(20) FIG. 3 shows in greater detail the component 30. Terminals 34 are connected across decoupler 38, and capacitor C.sub.P 36 is connected on the other side of the decoupler so as to be decoupled from the terminals 34. As before, decoupler 38 is shown as a DC-DC power supply. Additional capacitor C.sub.R 40 is connected across the terminals to deal with switching ripple, and capacitance/inductance to be emulated C.sub.B/L.sub.B appears across the terminals to be seen by the external circuit.

(21) FIGS. 4A and 4B are power-level equivalent circuits of FIG. 3 and will be discussed herein below.

(22) Reference is now made to FIG. 5, which is a simplified diagram illustrating control unit 60 for controlling the decoupler 38. Decoupler 38 is provided with a driving signal, and the driving signal is provided by the control unit 60. The control unit 60 comprises capacitance/inductance emulator 62, which provides a control signal for the decoupler 38 which control signal has a value based at least in part on a value of the desired capacitance/inductance C.sub.B/L.sub.B.

(23) The emulator may enable the emulation of the capacitance C.sub.B at the pair of terminals 34 by providing a DC reference voltage (v.sub.DC*) to the decoupler 38 at a control current i.sub.C, wherein the reference voltage is given by:

(24) 0$v_{\mathrm{DC}}^{*}=\frac{1}{C_B}\int i_C\left(t\right)\mathrm{dt}$

(25) or,

(26) the emulator may enable the emulation of the inductance L.sub.B at the pair of terminals 34 by providing a DC reference current (i.sub.DC*) to the decoupler 38 at a control voltage v.sub.C, wherein the reference voltage is given by:

(27) $i_{\mathrm{DC}}^{*}=\frac{1}{L_B}\int v_C\left(t\right)\mathrm{dt}$

(28) The integration may be carried out by integrator 63.

(29) The control unit may further include a loss compensation unit 64, which generates an initial control current/voltage which is calculated based on internal losses of the capacitance/inductance C.sub.B/L.sub.B being emulated.

(30) The control unit may further include a regulator 66, which regulates the current/voltage from the capacitance/inductance emulator to provide a regulated control signal.

(31) The control unit 60 may further include a modulator 68, which modulates the regulated control signal from the regulator to provide a switching sequence for the decoupler, which may be a power convertor.

(32) The electronic capacitance/inductance component may usefully be connected across a power supply circuit to smooth ripples. For power supply circuits with a relatively high rating, the decoupling between the capacitor and the terminals effectively allows a relatively small capacitor to emulate the much larger capacitor/inductor that the power supply needs.

(33) Reference is now made to FIG. 6, which is a flow chart that illustrates a method of providing an emulated capacitance/inductance value using a different capacitance value according to embodiments of the present invention.

(34) A pair of terminals 70 provide an external connection to the device. A capacitor having a second capacitance not being the capacitance/inductance to be emulated is then provided 72 and connected 74 to the terminals via a decoupler such as a DC-DC power supply.

(35) The decoupler is then controlled as a power supply using a reference signal having a value selected at least in part based on a value of the capacitance/inductance to be emulated.

(36) The device according to the present embodiments thus provides what appears to be the capacitance/inductance being emulated, across its output terminals and since the effect appears across the terminals, the terminals can simply be attached across an existing power supply. The device in fact provides the emulation electronically with the help of an internal decoupled capacitance C.sub.P which in many cases can be much smaller than the capacitance/inductance being emulated. If the device is used with mains voltage equipment such as power supplies, then the capacitor used need not be electrolytic and can be much smaller, and cheaper than those used in the prior art and thus have a longer expected lifetime.

(37) In greater detail, a smaller capacitance may be sufficient, as we note that according to above equation (7), bulk capacitance stores a maximal energy of:
E.sub.B.sup.MAX=½C.sub.B(v.sub.DC.sup.MAX).sup.2,  (11)

(38) out of which only a small fraction given by:
E.sub.B.sup.USED=½C.sub.B((v.sub.DC.sup.MAX).sup.2−(v.sub.DC.sup.MIN).sup.2)  (12)

(39) is actually used. For a typical case of 390V<v.sub.DC.sup.ss(t)<410V, less than 10% of stored energy is utilized. Therefore, a much smaller capacitor would be sufficient to supply the energy requirement than that required if the DC link ripple constraint did not exist. The electronic capacitor of the present embodiments, see FIGS. 2-6, allows physical decoupling of the power matching capacitor from the DC link, thus releasing its voltage from the ripple constraints given by (7). The decoupling leads to significant reduction of the power matching capacitance, i.e. C.sub.P<<C.sub.B in FIG. 2. It is further shown that any finite C.sub.B may be emulated by the electronic capacitor device of the present embodiments, using the circuit shown in FIG. 3.

(40) In FIG. 3, C.sub.R 40 is a small ceramic capacitor which may be present at the DC link side terminals 34 of the electronic capacitor to absorb switching ripple. Note that even though capacitor C.sub.P operates as a power matching element, its voltage ripple restrictions are much more relaxed than in equation (7) above.

(41) Neglecting the energy stored in C.sub.R, C.sub.P absorbs the pulsating power component, as shown in FIGS. 4A and 4B, i.e. its steady-state voltage would be given by:

(42) $\begin{array}{cc}{v}_P^{\mathrm{ss}}\left(t\right)\approx V_P^{*}+\underset{\underset{\Delta v_P\left(t\right)}{︸}}{\frac{1}{{C_P\left(V_P^{*}\right)}^2}{f}_P\left(t\right)}=V_P^{*}+\Delta v_P\left(t\right)& \left(13\right)\end{array}$

(43) with V.sub.P* and Δv.sub.P(t) denoting constant reference value and instantaneous ripple of v.sub.P(t), respectively. It should be emphasized that magnitude constraints of Δv.sub.P(t) are related to electronic capacitor operational requirements as well as the rated voltage value of C.sub.P while being independent on the rest of system power converters' operational restrictions.

(44) Assuming:
v.sub.P.sup.MIN<v.sub.P.sup.ss(t)<v.sub.P.sup.MAX,  (14)

(45) the value of the auxiliary power matching capacitance is determined from:

(46) $\begin{array}{cc}{C}_P=\frac{1}{V_P^{*}}\max \left(\frac{\underset{t}{\max }{f}_P\left(t\right)}{v_P^{\mathrm{MAX}}-V_P^{*}},\frac{\underset{t}{\min }{f}_P\left(t\right)}{v_P^{\mathrm{MIN}}-V_P^{*}}\right),& \left(15\right)\end{array}$

(47) and minimized by setting:

(48) $\begin{array}{cc}{V}_P^{*}=\sqrt{\frac{1}{2}\left({\left(v_P^{\mathrm{MAX}}\right)}^2+{\left(v_P^{\mathrm{MIN}}\right)}^2\right)}.& \left(16\right)\end{array}$

(49) It is interesting to note that DC link ripple is independent of the value of C.sub.P and is governed by the emulated capacitance value and regulation abilities of electronic capacitor converter only. Hence, in case the DC link voltage controller is capable of satisfying (5), capacitance C.sub.B is emulated by the electronic capacitor, from the DC link point of view, while actually utilizing the total capacitance of C.sub.R+C.sub.P.

(50) Control System

(51) The electronic capacitor/inductor device comprises a control system as illustrated in FIG. 5. The controller consists of three main subsystems: capacitance/induction emulation 62, loss compensation 64, voltage/current regulation 66 and modulator 68 as shown in FIG. 5.

(52) The emulation block 62 may emulate the capacitance/inductor terminal voltage/current behavior by setting the DC link voltage/current reference to be based at least in part on the capacitance/inductance to be emulated C.sub.B/L.sub.B and more particularly as:

(53) $\begin{array}{cc}{v}_{\mathrm{DC}}^{*}=\frac{1}{C_B}\int i_C\left(t\right)\mathrm{dt}\mathrm{or}{i}_{\mathrm{DC}}^{*}=\frac{1}{L_B}\int v_C\left(t\right)\mathrm{dt}& \left(17\right)\end{array}$
Loss Compensation

(54) The loss compensation block 64 calculates the DC current/voltage term drawn by the electronic capacitor/inductor to compensate internal losses as:
i.sub.0=f.sub.1(v.sub.P*−v.sub.P) or v.sub.0=f.sub.2(v.sub.P*−v.sub.P)  (18)

(55) where f.sub.1(⋅) and f.sub.2(⋅) are the compensating functions.

(56) Voltage/Current Regulation

(57) The voltage/current regulation block 66 calculates the control signal d to the power converter as:
d=g.sub.1(v.sub.DC*−v.sub.DC) or d=g.sub.2(i.sub.DC*−i.sub.DC)  (19)

(58) where g.sub.1(⋅) and g.sub.2(⋅) are the regulation functions.

(59) Modulator

(60) The modulator block 68 modulates the control signal d into switching sequence sent to the power converter.

Example

(61) As an example, consider (for brevity and clarity) a unity-power-factor operating single-phase rectifier, driving a DC load. Hence,
p.sub.C(t)=P.sub.L cos 2ω.sub.1t  (20)

(62) with P.sub.L and ω.sub.1 symbolizing load power and grid frequency, respectively. In case a bidirectional buck-boost electronic capacitor converter (v.sub.P<v.sub.DC) is utilized, power matching capacitance may ideally be reduced to:

(63) $\begin{array}{cc}{C}_P=\frac{P_L}{\left(\sqrt{2}-1\right){{\omega }_1\left(V_{\mathrm{DC}}^{*}\right)}^2}& \left(21\right)\end{array}$
for v.sub.P.sup.MIN=0, v.sub.P.sup.MAX=V.sub.DC*. In reality, somewhat higher matching capacitance may be selected to allow safety margins and improve robustness against abrupt load changes. Steady state input voltage and output current of the ACRC are then obtained as

(64) $\begin{array}{cc}{v}_P\left(t\right)=V_P^{*}\sqrt{1+\frac{P_L}{C_P{{\omega }_1\left(V_P^{*}\right)}^2}\sin 2{\omega }_{1}t}\mathrm{and}& \left(22\right)\\ i_{\mathrm{DC}}\left(t\right)=\frac{P_L}{V_{\mathrm{DC}}^{*}}\cos 2{\omega }_{1}t,& \left(22\right)\end{array}$

(65) respectively, FIG. 7A demonstrates experimental results with P.sub.L=350 W and C.sub.B=270 μF while FIG. 7B demonstrates experimental results with P.sub.L=350 W, C.sub.P=22 μF and emulated capacitance of 270 μF. Apparently, the results are very close, verifying the proposed method.

(66) The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean “including but not limited to”.

(67) The term “consisting of” means “including and limited to”.

(68) The term “consisting essentially of” means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

(69) As used herein, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

(70) It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub combination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

(71) Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

(72) All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.