Plug-and-play ripple pacifier for DC voltage links in power electronics systems and DC power grids

Patent metadata

Field	Value
Publication number	US-10594207-B2
Application number	US-201515771320-A
Country	US
Kind code	B2
Filing date	Oct 23, 2015
Priority date	Oct 23, 2015
Publication date	Mar 17, 2020
Grant date	Mar 17, 2020

Abstract

In many power electronics systems, there is an intermediate DC-link stage for facilitating the power processing of different sources to their loads. A device called a plug-and-play ripple pacifier (RP) directly plugged into the DC-link, and actively removes undesired DC-link ripple, thereby eliminating the reliance on electrolytes capacitors for stabilizing the system and remove ripple. Importantly, the use of this device is non-invasive to the operation of its host systems, and requires no modification of existing hardware. It is suitable for the protection of DC utilities/systems and can also be used as a direct replacement of ripple-canceling E-Caps in power converters device.

First claim

What is claimed is:

1. A power converter for stabilizing a DC-link interface to DC utilities and systems and which is connected to an AC/DC converter, comprising: first and second capacitors C o , C s each with first and second ends, the first capacitor being connected across a DC link; an inductor L connected in series with a first switch S 1 , the series being connected between the first end of the second capacitor C s and the DC link, a second switch S 2 connected between a junction of the first switch and the inductor and the second end of the second capacitor, and a control circuit that alternately operates said first switch and second switch to control the absorption of a DC ripple by presenting a variable impedance to the DC link; and wherein the power converter is connected to the DC-link interface without altering it so it functions as a two-port device that is plug-&-play.

2. The power converter of claim 1 wherein the control circuit only requires a voltage of the DC link.

3. The power converter of claim 1 wherein it is programmable to provide different types of impedance.

4. The power converter of claim 1 wherein the control circuit operates at a frequency higher than double the frequency of an input AC of the AC/DC converter.

5. The power converter of claim 1 wherein the control circuit comprises: a first comparator that compares the voltage across the second capacitor with a reference voltage and creates a first error signal; a converter for changing the first error signal into a first current signal; a functional modifier that modifies the current through the first capacitor to a second current signal; a second comparator for comparing the first and second current signals to generate a third current signal; a third comparator for comparing the current through the inductor to the third current signal to generate a fourth current signal; a current controller that converts the fourth current signal into switching signals for the first switch and second switch.

6. The power converter of claim 5 wherein the functional modifier is a capacitance multiplier.

7. The power converter of claim 5 wherein the functional modifier is a generalized impedance that can be programmed to emulate different impedances.

8. The power converter of claim 7 wherein the generalized impedance can be programmed to be one of a resistor, inductor or non-linear device.

9. A DC voltage system that provides DC voltage to DC utilities and systems, comprising: a power converter for providing the DC voltage to a DC link to which the DC utilities and systems are connected; and a ripple pacifier connected across the DC link, said ripple pacifier presenting variable impedance to the DC link so as to reduce an AC ripple in the DC link, said ripple pacifier relying only on the DC voltage for control and not adversely affecting the DC link.

10. The DC system of claim 9 wherein the power converter is a boost PFC rectifier.

11. The DC system of claim 9 wherein the power converter is a buck boost converter.

12. The DC system of claim 9 wherein the power converter is one of a step-up, step-down or step-up/down power electronics converter or an AC/DC converter including a full-bridge converter, half-bridge converter and multi-level converter or their derivative or combination.

13. The DC system of claim 9 wherein the power converter acts to perform at least one of the following: an emulated impedance, active power filter, voltage ripple reduction or improved stability margin of DC voltage linked power stages.

14. The DC system of claim 9 wherein the power converter acts as a second ripple pacifier to suppress or filter voltage ripple of a particular frequency that doubles main frequency commonly occurred in an AC-DC power converter systems.

15. A method for controlling an AC ripple from a switched mode power electronic converter connected to a DC link of a host DC voltage system, comprising the steps of: providing a two terminal device across the DC link; causing the two terminal device to emulate the AC ripple and to reflect the AC ripple in the impedance it presents to the DC link so as to reduce the AC ripple; causing the impedance to be presented in such a way as to not alter the DC link; controlling the two terminal device based on the measurement of the DC link.

16. The method of claim 15 , wherein the step of controlling involves alternately switching impedance elements in the two terminal device to vary the impedance presented by the two terminal device.

17. The method of claim 15 wherein the step of controlling operates at a frequency higher than double the frequency of the AC ripple.

Assignees

• Univ Hong Kong

Inventors

• Li Sinan
• Lee Ting Leung Albert
• Tan Siew Chong
• Hui Shu Yuen Ron

Classifications

• H02J1/02

  Arrangements for reducing harmonics or ripples · CPC title

• H02M1/15 Primary

  using active elements · CPC title

• H02J1/001

  Hot plugging or unplugging of load or power modules to or from power distribution networks · CPC title

• H02M7/4826

  operating from a resonant DC source, i.e. the DC input voltage varies periodically, e.g. resonant DC-link inverters · CPC title

• H03K7/08

  Duration or width modulation {; Duty cycle modulation} · CPC title