WO2017098338A1

WO2017098338A1 - Light weight static voltage regulator for ac mains

Info

Publication number: WO2017098338A1
Application number: PCT/IB2016/050956
Authority: WO
Inventors: Rakesh Goel; Ankur Goel
Original assignee: Rakesh Goel; Ankur Goel
Priority date: 2015-12-07
Filing date: 2016-02-23
Publication date: 2017-06-15

Abstract

The present disclosure relates to a static voltage regulator having three-legs power stage with LC filters. First, second, and third leg of the power stage can respectively be connected to Line-Out, Line-In, and Neutral with LC filters. Special modulation technique can be used to reduce losses. A MCU with embedded software individually implements Neutral level switching on the first leg, Line-In Up-converter with PFC on the second leg to make DC bus, and Line-Out mains generation with regulated voltage on the third leg.

Description

LIGHT WEIGHT STATIC VOLTAGE REGULATOR FOR AC MAINS

FIELD OF INVENTION

[0001] The present disclosure relates to a solid-state light weight static voltage regulator cum stabilizer for AC mains. More particularly, the present disclosure relates to a high frequency static regulator with reduced hardware and improved technique.

BACKGROUND OF THE INVENTION

[0002] The background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] One existing type of automatic voltage stabilizer is the multiple relay type stabilizer with step transformer, wherein relays are sometimes replaced by Triac or solid state switches, and controller either by discrete hardware or by MCU (micro-controller unit). Servo voltage regulator is better than step transformer type stabilizer as it controls output voltage continuously with better accuracy.

[0004] Generally, a static regulator is a replacement of servo stabilizer which consists of a high frequency converter and a low frequency (50 or 60 Hz) series transformer to regulate the output AC voltage, making the static regulator lighter compared to normal servo stabilizer due to replacement of AC variable transformer (variac) by solid state converter.

[0005] FIG. 1 illustrates a block diagram of a conventional servo stabilizer, wherein the stabilizer includes a variac, a series transformer to add or subtract delta voltage, a servo motor to move the position of the variac, and a control circuit to drive the servo motor. FIG. 2 illustrates a block diagram of a conventional static voltage regulator in which the conventional variac is replaced by a high frequency power stage, a low frequency 50 or 60 Hz series transformer, and MCU or DSP based control circuit.

[0006] However, static regulator though lighter than a servo stabilizer, is not a true lightweight product as it uses bulky low frequency series transformer. There is therefore a need for an architecture, framework, system, and method for a more efficient, compact and light-weight AC voltage regulator that completely eliminates low frequency transformer. [0007] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0008] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about." Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0009] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[00010] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

OBJECTS OF THE INVENTION

[00011] An object of the present disclosure is to provide a static voltage regulator for alternating current.

[00012] Another object of the present disclosure is to provide a light weight static voltage regulator.

[00013] An object of the preset disclosure is to provide a light-weight AC voltage regulator that completely eliminates use of low frequency transformer.

[00014] An object of the present disclosure is to provide a circuit architecture for voltage regulator that can control output voltage continuously with better accuracy.

SUMMARY

[00015] The present disclosure provides a solid-state light weight static voltage regulator cum stabilizer for AC mains that can regulate and automatically maintain a constant mains AC voltage. An embodiment of the present disclosure provides a static voltage regulator having three-leg power stage connected with LC filter and a micro controller unit (MCU) configured to operate the three leg power stage. In an exemplary implementation, first, second, and third leg of the three-legs of the power stage can respectively be connected to Neutral, Line-in and Line-Out that are also connected to three channel LC filter. In an exemplary implementation, the static voltage regulator can use a special modulation technique to reduce losses. A MCU with embedded software individually implements Neutral level switching on first leg, Line-In Up- converter with Power Factor Correction (PFC) on second leg to make DC bus, and Line-out mains generation with regulated voltage on third leg.

[00016] In an aspect, the static voltage regulator can include a three-channel LC filter, a three-leg power stage, and a micro controller unit (MCU) configured to remove harmonics and generate regulated voltage output. In an exemplary implementation, the static regulator can include a three-channel LC filter, a three leg power stage having first leg connected to the Neutral, second leg connected to the Line-In, and third leg connected to the Line-Out, and a micro-controller configured to control switching on the first leg, second leg, and the third leg so as to remove harmonics from the mains AC signal and generate a regulated voltage output.

[00017] In an exemplary implementation, the first leg is configured to provide Neutral level switching; the second leg is configured to work as Up-converter, and the third leg is configured to supply the regulated voltage output. In an exemplary implementation, the three-leg power stage can include a plurality of switches that can individually be controlled through switching command.

[00018] In an exemplary implementation, the micro-controller unit (MCU) or Digital Signal Processor (DSP) can be configured to sense properties of incoming mains signal at the line-in and feedback signal from the third leg, and generate switching commands based on sense properties and feedback signals to individually control the switching on the first leg, second leg, and the third leg. Properties of the incoming mains signal can include any or a combination of voltage, current, frequency, and phase information. Properties of the incoming mains signal can be determined by executing the high speed interrupt service routine.

[00019] In an exemplary implementation, plurality of switches of the three leg power stage can include a first set of switches comprising a first switch, a second switch, and a third switch connected in parallel with high voltage side of a voltage supply unit, and second set of switches comprising a fourth switch, a fifth switch, and a sixth switch connected in parallel with low voltage side of the voltage supply unit. In an exemplary implementation, the first switch and the fourth switch can be connected in series to control the Line-Out though the third leg of the three leg power stage, the second switch and fifth switch can be connected in series to the line-in through second leg of the three leg power stage, and third switch and sixth switch can be connected in series to control the neutral through a first leg of the three leg power stage.

[00020] In an exemplary implementation, the micro-controller unit (MCU) can be configured to sense properties of incoming mains signal at the Line-In and feedback signal from the third leg, and generate switching commands for turning ON/ OFF selected switches of the plurality of switches of the three leg power stage to generate the regulated voltage output. BRIEF DESCRIPTION OF DRAWINGS

[00021] In the Figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label with a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[00022] FIG. 1 illustrates a typical block diagram of a conventional servo stabilizer.

[00023] FIG. 2 illustrates a typical block diagram of a conventional static voltage regulator.

[00024] FIG. 3 illustrates an exemplary block diagram of invented static voltage regulator in accordance with an embodiment of the present disclosure.

[00025] FIG. 4 illustrates an exemplary simplified scheme of three-channel power stage with filters used in this application in accordance with an embodiment of the present disclosure.

[00026] FIG. 5 illustrates exemplary captured waveforms of the present disclosure.

[00027] FIG. 6 illustrates further exemplary waveforms of the present disclosure.

[00028] FIG. 7 illustrates simulated waveforms in an exemplary aspect of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

[00029] Embodiments of the present disclosure generally relate to a static regulator to regulate the mains AC voltage. In an aspect of the present disclosure, phase bridge and three LC (inductor-capacitor) filters can be configured to implement the proposed static regulator.

[00030] In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the present invention. It will be apparent to one skilled in the art that embodiments of the present invention may be practiced without some of these specific details.

[00031] Embodiments of the present invention include various steps, which will be described below. The steps may be performed by hardware components or may be embodied in machine-executable instructions, which may be used to cause a general-purpose or special- purpose processor programmed with the instructions to perform the steps. Alternatively, steps may be performed by a combination of hardware, software, firmware and/or by human operators. [00032] If the specification states a component or feature "may", "can", "could", or "might" be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[00033] Although the present disclosure has been described with the purpose of implementing static voltage regulator, it should be appreciated that the same has been done merely to illustrate the invention in an exemplary manner and any other purpose or function for which the explained structure or configuration can be used, is covered within the scope o the present disclosure.

[00034] Different embodiments of the present disclosure provide a solid-state light weight static voltage regulator cum stabilizer for AC mains. Embodiments of the present disclosure relate to a static regulator to regulate a main AC voltage to automatically maintain a constant voltage level. An embodiment of the present disclosure provides a static voltage regulator having three-leg power stage connected with LC filter and micro controller unit (MCU) configured to operate the three-leg power stage. In an exemplary implementation, first, second, and third leg of the three-legs of the power stage can respectively be connected to Neutral, Line-In, and Line-Out that are also connected to three channel LC filter. In an exemplary implementation, the static voltage regulator can use special modulation technique to reduce losses. A MCU with embedded software individually implements Neutral level switching on first leg, Line-In Up-converter with PFC on second leg to make DC bus, and Line-out mains generation with regulated voltage on third leg.

[00035] The static voltage regulator includes a three-channel LC filter, a three leg power stage and a micro controller unit (MCU) or Digital Signal Processor (DSP) configured to remove harmonics and generate regulated voltage output. In an exemplary implementation, the static regulator include a three-channel LC filter having a first channel connected to Neutral, second channel connected to Line-In and third channel connected to Line-Out, a three leg power stage having first leg connected to the neutral, second leg connected to the Line-In and third leg- connected to the Line-Out and a micro-controller configured to control switching on the first leg, second leg and the third leg so as to remove harmonics from the mains AC signal and generate a regulated voltage putout.

[00036] In an exemplary implementation, the first leg is configured to provide Neutral level switching, the second leg is configured to work as Up-converter and the third leg is configured to supply the regulated voltage output. In an exemplary implementation, the three leg power stage can include plurality of switches that can individually be controlled through switching command.

[00037] In an exemplary implementation, the micro-controller unit (MCU) can be configured to sense properties of incoming mains signal at the line-in and feedback signal from the third leg and generate switching commands based on the sense properties and feedback signal to individually control the switching on the first leg, second leg and the third leg. The properties of the incoming mains signal can include any or combination of voltage, current, frequency and phase information. The properties of the incoming mains signal can be determined by executing the high speed interrupt service routine.

[00038] In an exemplary implementation, the plurality of switches of the three leg power stage can include a first set of switches comprising of a first switch, a second switch and a third switch connected in parallel with high voltage side of a voltage supply unit, and second set of switches comprising of a fourth switch, a fifth switch and a sixth switch connected in parallel with low voltage side of the voltage supply unit. In an exemplary implementation, the first switch and the fourth switch can be connected in series to control the Line-Out though the third leg of the three leg power stage, the second switch and fifth switch can be connected in series to the Line-In through second leg of the three leg power stage, and third switch and sixth switch can be connected in series to control the Neutral through a first leg of the three leg power stage.

[00039] In an exemplary implementation, the micro-controller unit (MCU) can be configured to sense properties of incoming mains signal at the Line-In and feedback signal from the third leg and generate switching commands for turning ON/ OFF selected switches of the plurality of switches of the three leg power stage to generate the regulated voltage output.

[00040] FIG. 3 illustrates an exemplary block diagram 300 of the proposed static voltage regulator in accordance with an embodiment of the present disclosure. Major components of the proposed static voltage regulator include a three-leg power stage 302, a three-channel LC filter 304, and a micro-controller unit (MCU) 306 to control output current. The proposed static voltage regulator operates at high frequency, ensuring small size of LC filters and also reducing overall weight of the proposed system. FIG. 4 illustrates a simplified scheme of three-leg power stage 302 with LC filter 304, wherein, as can be seen, the Neutral is controlled by switches CH and CL (named as the first leg of the power stage), Line-In is controlled by BH and BL (named as second leg of the power stage), and Line-Out is controlled by AH and AL (named as third leg of the power stage).

[00041] In an aspect, FIG. 5 illustrates exemplary captured waveforms of the present disclosure, wherein channel C2 at 502 is a synchronized signal to trigger the scope to see stable waveforms, C4 at 508 is the waveform of Neutral, C3 at 506 is the Line-In waveform, while CI at 504 is the Line-Out waveform captured at final input-output points after LC filters. Math at 510 is the difference of Line-In and Neutral (C3-C4).

[00042] FIG. 6 illustrates further exemplary waveforms of the present disclosure, wherein channel C2 at 602 is same synchronized signal to trigger the scope to see stable waveforms. C4 at 608 is the waveform of Neutral after power stage and before LC filters. C3 at 606 is the Line- In waveform, while CI at 604 is the Line-Out waveform captured at power stage before LC filters.

[00043] In an aspect, the present disclosure demonstrates simplified and lightweight hardware compared to any other AC voltage regulator. A high speed interrupt service routine measures analog signals, processes, and computes incoming mains signal, based on which, its voltage, frequency and phase information are computed. In an aspect, the Neutral can be controlled by completely tuning ON either CH or CL based on the electrical angle of this incoming mains signal. Both switches CH and CL can be configured to be OFF near zero crossing of the incoming signal, as is clearly shown at 608 in FIG. 6. As the CH and CL are turned ON or OFF, it significantly reduces switching losses on this leg of the power stage. Turning OFF both switches CH and CL has an additional advantage of eliminating high circulating current due to slight error in computation of the electrical angle.

[00044] In an aspect, Line-In is connected to second leg of the power stage, which is controlled by BH and BL. Here, PWM is applied on one switch at a time between BH and BL based on electrical angle of the incoming mains signal, wherein the duty cycle of this PWM is controlled based on the position of the input sine wave to maintain good Power Factor (PF). This stage works as an Up-converter (Boost converter) in which one switch is modulated and diode on other switch delivers power to the DC bus. This is clearly shown at 506 in FIG. 5. Inductor of the LC filter connected on this leg can also work as PFC inductor to transfer power to the DC bus.

[00045] In another aspect, Line-Out can be connected to third leg of the power stage, which can be controlled by AH and AL. Sine modulation can be generated on this leg by modulating both AH and AL switches with dead time insertion. The LC filter on this leg can filter PWM ripples and controlled AC mains voltage can be available at Line-Out. A control loop ensures regulated output voltages between Line-Out and Neutral. 504 at FIG. 5 shows that modulation on this leg is disabled and its waveform is copy of 508 (Neutral waveform). This explains that Line-Out voltage is zero in this condition. 604 at FIG. 6 shows that modulation on this leg is enabled and its waveform is different from 608 (Neutral waveform), which explains that Line-Out voltage is available as a difference of 604 and 608.

[00046] FIG. 7 illustrates exemplary simulated waveforms of the present disclosure, wherein 702 is the left scale that is bipolar to explain mains waveform w.r.t. Earth. 704, on the other hand, is the right scale that is unipolar and explains the waveforms w.r.t. floating common of the power stage. In an aspect, the simulation can be conducted with assumptions of Line-In at 200V AC, Line-Out at 220V AC, and DC Bus at 350V DC. The Line-In is shown at 706, and Line-Out is shown at 708, which shows that voltage at Line-Out 708 is boosted to 220V AC as it is higher than Line-In 706. 710 indicates Line-In2, Line-Out2, and Neutral2 w.r.t. floating common of the power stage, wherein the neutral is switched to floating common or to DC bus positive by turning completely ON CH or CL. Therefore, the potential between Earth and floating common of the power stage continuously changes as per electrical angle.

[00047] To explain further, the Line-In and Line-Out signals are bipolar due to sine wave, while the power stage works on unipolar DC bus. Switching of Neutral ensures that all 3 signals (Neutral, Line-In, Line-Out) lies within 0 to DC bus positive. First half cycle modulation on Line-Out is normal with zero offset while second half cycle modulation on Line-Out is inverter with offset equal to DC bus voltage.

[00048] The three-legs of power stage have different functions as explained earlier. Therefore, the power devices and inductors can be different for cost optimization. The switches on Neutral can operate at low speed (twice of line frequency). Therefore, its switches CH and CL can be implemented using low speed low drop IGBTs. The value of its inductor in LC filter can be too small or zero. The switches on Line-In can operate as active PFC at high frequency. Therefore, its switches BH and BL can be implemented using high speed IGBT or High power MOSFET. Its inductor in LC-filter can be designed to handle full power in up converter mode. Finally, the switches on Line-Out operate as PWM to generate output voltage at high or medium frequency. Therefore, its switches AH and AL can also be implemented using medium speed IGBT, wherein the inductor in LC filter can be designed to attenuate PWM ripples from output.

[00049] A small filter capacitor can be sufficient on the DC bus as power in and out is approximately same on the DC bus in real time. Therefore, the need to hold energy for just one PWM cycle.

[00050] The bypass of Line-In to Line-Out is also very easy in this invention just by turning ON switches on their respective legs opposite to switches of Neutral leg. To explain further, switches CL, BH and AH are turned ON during first half cycle. Similarly, switches CH, BL and AL are turned ON during second half cycle.

[00051] In this invention, only 3 leg power stage and 3 channel LC filter is connected to three power lines namely Neutral, Line-In and Line-Out. Therefore, this inverter can be designed by connecting 3 power lines to 3 channel power stage in any sequence with appropriate software.

[00052] While embodiments of the present invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions, and equivalents will be apparent to those skilled in the art, without departing from the spirit and scope of the invention, as described in the claim.

ADVANTAGES OF THE INVENTION

[00053] The present disclosure provides a static voltage regulator for alternating current.

[00054] The present disclosure provides a light weight static voltage regulator.

[00055] The preset disclosure provides a light-weight AC voltage regulator that completely eliminates use of low frequency transformer.

[00056] The present disclosure provides circuit architecture for static voltage regulator that can control output voltage continuously with better accuracy.

Claims

CLAIMS: What we claim is

1. A static voltage regulator to regulate a mains AC voltage, the static regulator comprising: a three-channel LC filter having first channel connected to Neutral, second channel connected to Line-In, and third channel connected to Line-Out;

a three leg power stage having first leg connected to the Neutral, second leg connected to the Line-In, and third leg-connected to the Line-Out; and

a micro-controller unit (MCU) or Digital Sign a Processor (DSP) configured to control switching of the first leg, second leg, and the third leg so as to remove harmonics from the mains AC signal and generate a regulated voltage putout.

2. The static voltage regulator of claim 1, wherein the first leg is configured to provide Neutral level switching, the second leg is configured to work as Up-converter, and the third leg is configured to supply the regulated voltage output.

3. The static voltage regulator of claim 1, wherein the three leg power stage comprises a plurality of switches that are individually controlled through switching command.

4. The static voltage regulator of claim 1 , wherein the MCU is further configured to sense properties of incoming mains signal at the Line-In and sense feedback signal from the third leg, and generate at least one switching command based on the sensed properties of the of incoming mains signal and of the feedback signal to individually control the switching of the first leg, the second leg, and the third leg.

5. The static voltage regulator of claim 4, wherein the properties of the incoming mains signal comprise any or a combination of voltage, current, frequency and phase information.

6. The static voltage regulator of claim 4, wherein the properties of the incoming mains signal are determined by executing a high speed interrupt service routine.

7. The static voltage regulator of claim 3, wherein the plurality of switches comprise:

a first switch, a second switch, and a third switch connected in parallel with high voltage side of a voltage supply unit; and a fourth switch, a fifth switch, and a sixth switch connected in parallel with low voltage side of the voltage supply unit, wherein the first switch and the fourth switch are connected in series to control the Line-Out though the third leg of the three leg power stage, and wherein the second switch and fifth switch are connected in series to the Line- In through second leg of the three leg power stage, and wherein the third switch and the sixth switch are connected in series to control the neutral through a first leg of the three leg power stage.