EP1465037A2

EP1465037A2 - A method and system for alternating current regulation

Info

Publication number: EP1465037A2
Application number: EP04076919A
Authority: EP
Inventors: Douglas S. Schatz; Richard A. Scholl; Geoffrey N. Drummond; David J. Christie
Original assignee: Advanced Energy Industries Inc
Current assignee: Advanced Energy Industries Inc
Priority date: 1998-12-30
Filing date: 1999-12-29
Publication date: 2004-10-06
Also published as: EP1465037A3

Abstract

Circuitry and methods for regulating alternating current regulation uses energy storage and release principles to boost or buck voltage to permit regulated ac operation with parallel and series bi-directional switch elements (12) and (13) operated at either variable duty cycles or frequencies to accommodate bipolar ac operation. Each bi-directional switch element may include a diode bridge (8) or (10) and directionally limited switches such as semiconductor switches. The system can be used to regulate ac even during sub-cycle dips, can be used to simulate controlled dips, can be used to correct power factor for loads, and can be applied in multiphase operations.

Description

I. TECHNICAL FIELD

The present invention relates to alternating current regulation. Specifically, it provides a method and system for low cost regulation of alternating current applications and includes embodiments that may be useful for ac fault simulation, non-linear load power factor correction, and reactive load correction in three phase systems.

II. BACKGROUND OF THE INVENTION

In the generation and delivery of power, utility companies must face natural problems such as tree limbs falling across power lines, ice storms which may create ice loads on power lines causing them to fall, lightning strikes on power lines, and many types of electrical defects which can occur in substations. These problems can and often do cause disturbances on power being delivered to the utility customers.

These disturbances may or may not cause the user of the power, the utility customer, problems. Some industries, such as petroleum processing plants, and residences, are usually not much affected by these disturbances, provided that sensitive equipment such as electronics are protected by surge suppressing devices. Other industries, such as data processing centers and semiconductor fabrication plants, can be seriously affected by surges or dips on the power coming into their facilities. In the former case loss of data is possible and in the latter loss of product; in both cases the losses are often extremely expensive, and can run to the millions of dollars for an incident or disturbance which may last only a few cycles of the incoming power (that is, for a small fraction of a second).

Many studies of power quality at various sites have been conducted, and they typically show that, while surges in power do occur, they make up a very small fraction of the total problem, and the dominant disturbance which causes expense is a dip, or momentary reduction in power. Typically the dip is a reduction in voltage of less than 50% of the nominal voltage, with a duration of less than one second. In one study, 95% of the problem-causing disturbances were dips in voltage which lasted less than 20 cycles (1/3 second) and in which the magnitude of the dip was less than 30% of nominal (i.e., 70% of the voltage remained). In another study, of an average of five dips per month, the majority of voltage dips were to a voltage of from 70% to 90% of nominal, and most sags had a duration of 10 cycles or less. From these studies one can see that if a regulator were available which could handle dips as large as 50% (that is, could provide a steady output in the presence of as little as half nominal voltage), a very large fraction of the problems would be ameliorated.

There are a number of prior art technologies which can be brought to bear to bring the power quality at the user's load to a level which does not cause problems. One such technology is the Dynamic Voltage Restorer, or DVR. This device can do voltage correction, or regulation, for a brief period, and works by adding a compensating voltage to the power line to correct for a "sag" or dip in the power line voltage. It is generally not designed to protect against complete outages or severe dips. The DVR is a transformer with multiple taps such that electronic switches, usually thyristors, can be switched to provide a "boost" of fixed amounts, such as 5% per step. Thus a voltage of 5, 10, 15, 20% or other multiple of 5% can be added to the power line at its output. The DVR can be made very large, and therefore capable of handling megawatts of power, and at high powers is reasonable in cost per kilowatt. Its disadvantages are the inability to provide smooth output power, as it can only switch in steps, and its large size and weight. Because of this large size and weight, it is not a portable device.

A second technology used to ameliorate these problems is the High Speed Electronic Transfer Switch, or HSETS. The HSETS is used when an alternate source of power is available from the utility. That is, the utility runs two power lines into the customer's facilities, one from each of two substations, and the HSETS can switch the input power to the facility from a source with a lowered voltage level to the second, backup source, which presumably is undisturbed. Of course, optimum performance requires that the two sources be as independent of one another as possible, as a dip on both cannot be dealt with. The cost is not high per megawatt handled, but as it must be installed together with an alternate power feed from a separate substation, and must handle the entire power load of the facility, the installation, or initial, cost is high, generally over $1,000,000.

A third solution involves storage of energy. In this case a storage unit stores energy which may be used to supplement the utility power during a dip and therefore provide unblemished power to the user's load. The energy storage may be through an electric field device, such as a capacitor, a magnetic field device such as an inductor, a chemical device, such as a battery, or a mechanical device, such as a flywheel/generator. Such devices have the advantage of being able to supply power during a complete outage, or blackout, because they can deliver the energy they have stored during normal operation. Also, they can maintain a constant output of power during a dip without drawing a proportional additional current from the incoming power line again because of the stored energy. They have two principal disadvantages: they are costly, and the stored energy can be dangerous if a fault causes it to be released abruptly.

Heretofore, then, there have been solutions to the problem of inferior power quality but they have been either expensive, or are affordable only for large power users, and all are large and heavy, making them unsuitable for portable installation.

A regulator of low frequency ac power as described heretofore is also an adjuster of low frequency ac power. As used herein, the term "regulator" implies a unit which contains circuitry to maintain the output voltage, current, or power at a constant value independent of changes in input line voltage or load impedance. The term adjuster encompasses the concept of a regulator, but also may be used to describe a circuit which merely raises or lowers the output power, without the circuitry to maintain the output constant under changing conditions. That is, a regulator is a special case of the adjuster, with the regulation circuitry required to maintain the output.

Heretofore there has been available variable transformers which can provide continuous adjustment, without regulation, of low frequency ac power, but these "variable auto transformers" are large, expensive, and heavy and have sliding contacts, or "brushes" which wear in time and cause reliability problems.

The high cost of power dips is due to poor power quality on the one hand, and poor immunity on the part of equipment of certain types on the other. To address this, some organizations are setting standards for equipment behavior under conditions of power dips, and requiring newly designed equipment for their use be able to withstand dips of larger magnitude for short times and lesser magnitude for longer times. In one case, as an example, a standard has been proposed which would require that equipment operate normally in the presence of a power dip of up to 50% for three to twelve cycles, 30% for twelve to thirty cycles, and 20% for thirty to sixty cycles. Testing equipment to ensure that it meets this standard is not easy. For one thing, the equipment must be run in actual production conditions to ensure that the test is valid with regard to "normal" operation, but another difficult task is to simulate the dip on the power line. This is not so hard if the times involved are long, but if the equipment would operate through a power dip of 50% for 0.2 seconds (12 cycles at 60 Hz) but not longer (thus meeting the specification), the test setup must create a dip of just that length and no longer. This precludes the use of relays and mechanical contactors. Also, the test, to be accurate, must start a dip at any phase of the power line, and this requires a nicety of timing not possible with mechanical devices. The only device available which can switch voltage levels fast enough is the DVR, and the nature of the semiconducting devices (thyristors) permits changes to be made only at the end of cycles if they are to last for a number of full cycles, and in any event the DVR is not portable, and portability is very important in test equipment.

Some loads have an entirely different problem for the power source: they have poor power factor. If the root-mean-square voltage times the root-mean-square current (called the VA product) is larger than the power, which can happen if there is a reactive component to the load impedance or if the load is non-linear, then transformers, circuit breakers, and other power delivery components must be increased to accommodate. The ratio of power to VA product is called the power factor. If this ratio is less than about 0.9 it begins to be a problem in the power system, and in many districts the utility may charge more per unit of power if a facility has a low power factor. There are methods available to correct power factor if caused solely by reactive components, but there is not currently available a small, lightweight, inexpensive method of correcting power factor in large installations due to non-linear loads. Also, the methods used to adjust for poor power factor due to reactive loads can be bulky and awkward and it would be advantageous to have available a small, lightweight method of accomplishing correction of power factor even for reactive loads.

III. DISCLOSURE OF THE INVENTION

It is an object of this invention to provide a reliable design for a low frequency ac voltage regulator with fewer parts and more reliable parts than prior art designs.

It is a further object of the present invention to provide a design for a low frequency ac voltage regulator which is simple and which can be manufactured easily at a manufacturing cost lower than prior art designs.

It is yet a further object of the present invention to provide a design for a low frequency ac voltage regulator which can be smaller and lighter in weight than prior art designs, permitting it to be used in portable designs. Naturally, this may enhance the scope of application of such regulators.

It is also an object of the present invention to provide a design for a low frequency ac voltage regulator which can achieve stable yet faster control over its output power than was possible using prior art techniques.

The present invention also has the object of providing more stable performance into critical loads in the presence of incoming power which may vary rapidly.

It is yet another object of the present invention to provide a design for a low frequency ac voltage regulator which is capable of supplying smooth output waveforms, even in the presence of sub-cycle transients on the incoming power.

It is a further object of the present invention to provide a design for a simulator capable of supplying reductions ("dips") in an otherwise steady power stream which are short (<1 sec) and controllable to a small fraction of a cycle.

It is another object to provide a means for correcting power factor in a power system due to non-linearity in the power load.

It is yet another object to provide a means for correcting power factor in a power system due to reactive components in the power load.

Accordingly, the present invention provides a novel circuit operating at high frequency which can produce an output voltage higher than its input voltage without transformers or low frequency inductors, using switchmode power supply techniques, and a related circuit which can produce an output voltage smaller than its input voltage without transformers or low frequency inductors, also using switchmode power supply techniques. Both circuits can, with suitable control circuitry, correct power factor.

Naturally, further goals and objects of the invention are disclosed throughout other areas of the specification and claims.

IV. BRIEF DESCRIPTIONS OF THE DRAWINGS.

Figure 1 is a simplified circuit diagram of a dc "boost" circuit as used in dc power supplies.

Figure 2 is a simplified circuit diagram of a dc "buck" circuit as used in dc power supplies.

Figure 3 shows the output of the regulator circuit with a sinusoidal input.

Figure 4 shows the output of the regulator with a bipolar sinusoidal input waveform.

Figure 5 is a simplified circuit diagram of a boost regulator circuit according to the teachings of the present invention for regulation of single phase power lines.

Figure 6 is a simplified circuit diagram of an ac buck regulator circuit according to the teachings of the present invention for simulation of single phase power line dips.

Figure 7 is a representation of an oscillogram of a three-cycle power line dip, the top and bottom dashed lines showing the nominal voltage, the inner dashed lines showing the reduced line voltage, solid reduced sinusoid showing an unregulated dip, and the dashed sinusoid showing the regulated output.

Figures 8a and 8b are representations of two alternative circuits which permit the use of unipolar switches in alternating current circuits. Figure 8a shows a series field effect transistor arrangement; Figure 8b shows a parallel field effect transistor arrangement. In each, the inner connections (small circles) indicate the drive signal connections.

Figures 9a and 9b are block diagrams of two types of three phase voltage regulator circuits according to the teachings of the present invention. Figure 9a shows a Y-Δ connection three phase regulator; Figure 9b shows a Δ-Y connection three phase regulator.

V. BEST MODES FOR CARRYING OUT THE INVENTION

As can be seen from the drawings, the basic concepts of the present invention may be embodied in many different ways. The concept of a "boost" regulator is well known in the prior art. Referring to Figure 1, which shows a classical dc boost regulator, its operation will be explained. The dc source of power is connected through inductor 3 and diode 5 to load 7. Switch 4 is connected from the junction of inductor 3 and diode 5 to the dc power common lead, as is the other terminal of load 7. Small capacitors 2 are used at both the input and the output to filter high frequency transients.

The circuit operates as follows: Switch 4 is closed periodically at a frequency f_s for a fraction η of the period 1/f_s. During the time the switch is closed current rises in inductor 3 at a rate equal to the input voltage V_i divided by the inductance L of inductor 3. When switch 4 opens, the magnetic field of inductor 3 starts to collapse, which causes the voltage across switch 4 to rapidly rise. This causes conduction of diode 5, carrying the inductor current into load 7, at a higher voltage than V_i. There is therefore a voltage difference across the inductor equal to the output voltage V_o minus the input voltage V_i. This voltage difference causes a drop in the current in inductor 3, at a rate of (V_o-V_i)/L. In steady state, this drop in current (when the switch is open) is equal to the rise in current when the switch is Vi L tc =(Vo -Vi ) L to closed: Here t_c is the time the switch is closed and t_o is the time it is open. Since t _c+t_o=1/f_s, and t_c=η/f_s, the above equation provides the result that Vo Vi =11-η So the duty cycle η of the switch determines the ratio of the output to input voltage, called the "boost" factor, V_o/V_i. If the switch is closed for only a small fraction of the total period, the factor η is small, and the output is nearly equal to the input. As the switch is closed a larger and larger fraction of the total time, the output voltage increases relative to the input. For the output to be held steady during the time the switch is off, the inductance L must be large enough to support a small change in current; this value depends upon the resistance R of the load 7 as well in a manner well known to those skilled in the art. Diode 5 conducts only when switch 4 is open, so the diode and the switch conduct alternately.

A close relative of this circuit provides a "buck" circuit, as shown in Figure 2. Here the diode 5 has exchanged positions with the switch 4 as compared to the boost circuit, and the circuit reversed input-to-output. Analysis of the operation of the buck circuit is along the same lines taken with the boost circuit. Here when the switch is closed the difference between the input and the output voltage appears across inductor 3, and when the switch is open the diode conducts to maintain the current in inductor 3 (note again that the switch and the diode conduct alternately). Equating as before the rise and fall of the current in inductor 3 in steady state yields: Vo L to =(Vi -Vo ) L tc and Vo Vi =η assuming that the current flow in inductor 3 is continuous.
Here, of course, the output voltage is smaller than the input voltage.

Both circuits can operate as dc transformers; that is, at a fixed duty factor η they have a constant ratio of input to output voltage. Thus, if connected to a source of varying dc voltage, the output variation will be a faithful representation of the input variation, but multiplied by the transformation ratio, which is bigger than unity for the boost circuit and smaller than unity for the buck circuit, provided that the switching period t_c+t_o is short compared to the variations in the input voltage. This is represented in Figure 3, wherein is depicted the beginning of a sinusoidal waveform. Superimposed on this is a series of pulses, each representing the closing-of switch 4, with the output waveform represented by the dark line. As can be seen, the dark line approximates the sinusoid, and would more closely approximate it if the frequency of the pulses were higher (that is, if the pulses were more closely spaced). Either of the two circuits will produce this result, with the boost circuit "amplifying" the input voltage and the buck circuit "reducing" it.

Both of these circuits operate only on direct current. For the circuits shown in Figures 1 and 2, and for the output shown in Figure 3, the polarity of the power source is shown as positive (positive up). For a circuit operating on a negative supply (negative up), one would reverse the direction of the diode. Of course, in either case the switch must be arranged to conduct electricity in the appropriate direction.

Neither circuit can operate with an alternating input, because of the necessity of polarizing both the diode and, generally, the switch. It will be clear that it is not possible to simultaneously select the diode orientation and switch polarity for positive and negative input voltages. This has prevented using these circuits for alternating power in the past.

Either circuit could be made to operate in a bipolar mode (i.e., with ac power), however, if advantage is taken of the fact that the diode and the switch conduct alternately. That is, if the diode is replaced by a switch, the circuit would operate on ac input, provided that the switches could conduct in both directions. A semiconductor switch is generally able to operate in one direction of current flow only, but if the switch is placed within a diode bridge, the action of the four diodes is to force current flow through the switch always in the same direction regardless of the direction of current flow external to the bridge. If the semiconductor switches were, then, replaced by a switch surrounded by a diode bridge, and if two switches are used, both halves of a sinusoidal input waveform could be handled with either a boost or buck configuration. This approach permits the regulation of alternating powers. In this mode, (without the reserve mentioned below) a boost circuit may be used to compensate for dips in the incoming power, and a buck circuit may be used to compensate for surges.

Generally, power dips may be of larger concern as they are more common. Thus a boost topology may be of higher practical value in some applications. However, even with only a boost configuration, by adjusting the input to be smaller than nominal (such as through the use of an autotransformer), thereby requiring a certain level of boost at nominal line, an amount of power surge could be handled by a boost topology as well.. This could occur -- without combining or perhaps further switching between boost and buck circuitry -- by lowering the nominal boost level during the power surge. Conversely, a buck circuit intended to handle surges may be used to handle a certain level of dips perhaps through a similar use of an autotransformer to provide slightly higher than nominal voltage, requiring a certain level of bucking action at nominal line. This "reserve" of buck may then be used to provide a measure of compensation for dips. In either case, the reserve (of buck or boost) and be available to handle at least some amount of an opposite condition.

Returning to the basic arrangement for understanding, the resulting output is represented in Figure 4. Here each rectangle indicates a complete cycle of the switches in the circuit and again the dark line indicates the nature of the approximated output. Also as before, the higher the switching frequency (the shorter the period of the pulses) the closer the dark line would approximate the sinusoid. And again, either of the two circuits will produce this result, with the boost circuit "amplifying" the input voltage and the buck circuit "reducing" it.

The resulting circuits are shown in Figures 5 and 6 for the boost and buck circuits respectively. Either of the two circuits will produce the result shown in Figure 4 for a sinusoidal input, with the boost circuit "amplifying" the input voltage and the buck circuit "reducing" it.

In Figures 5 and 6, the ac input power 14 is applied to the circuit, and inductor 3, capacitors 6 and load 7 perform in the same roles as they had in Figures 1 and 2. Switch 4 and diode 5, respectively, have each been replaced by a

diode bridge

8 and 10, respectively, surrounding a

semiconductor switch

9 and 11, respectively, here shown as an Insulated Gate Bipolar Transistor (IGBT), but it should be noted that this switch could be replaced by a Field Effect Transistor (FET), Bipolar Junction Transistor (BJT) or other kind of electronic switch as would be known by a worker skilled in the art. As should be easily understood, these circuit elements serve as

bi-directional switch elements

12 and 13, respectively. The parallel bi-directional switch-element 12 replaces the switch in the boost arrangement; the series bi-directional switch element 13 replaces the diode in the boost arrangement. Similarly, in the buck circuit arrangement shown in Figure 6, the parallel bi-directional switch element 12 replaces the diode in the buck arrangement; the series bi-directional switch element 13 replaces the switch in the buck arrangement. Also, in each the diode bridge could be replaced by a series combination of FET devices, as shown n Figure 8a, or by a pair of series combinations of a diode and FET, said pair of elements placed in parallel, as shown in Figure 8b. Other combinations are possible as well, and any circuit which permits bilateral flow of current to be controlled by a drive signal will serve the purpose of the invention.

Also, not shown in Figures 5 and 6 is the circuitry required to provide a drive signal to the semiconductor switch, or the logic to determine the timing of the drive pulses, as the exact method of accomplishing this would also be apparent to a worker skilled in the art. Naturally, for the regulator, circuitry would be required to measure the output voltage and adjust the length of the pulses to maintain the output voltage to a desired (nominal) level. In order to provide a steady voltage across the power system load, the output voltage of the regulator may be compared to a steady "reference" signal, and the conduction time of the switch adjusted to produce an output equal to the reference. A steady smooth sinusoidal waveform of the same frequency as the power line may be used as a reference. Such a waveform may be generated by a sine wave oscillator, or generated digitally by use of a sine table memory circuit coupled with a digital-to-analog converter. It will be clear that in the former case the oscillator may need to be phase locked to the power line to ensure that the comparison is made correctly, and in the latter case the lookup should be made synchronously with the power line perhaps through phase locking of the clock circuits to the power line. Thus, where in a dc circuit, the desired reference signal would be a simple dc level, in this application the reference to which the output should be compared would be a standard sinusoidal signal, likely phase locked to the input sinusoid.

These circuits may be used not only for output voltage regulation or simple adjustment, but also as a form of power factor regulation for non-linear loads. If a load is non linear, when a sinusoid of voltage is impressed upon it, the current will not be sinusoidal. The power, therefore, as the product of voltage and current is also non-sinusoidal, and therefore contains harmonic content. The resulting high frequency current components of the power can cause difficulties in the power distribution system. By modifying the control circuitry it is possible to create an output voltage with a waveform which is not a sinusoid, just so that the input current is kept sinusoidal, eliminating the harmonic currents. This is a type of power factor correction, for which the subject invention is well suited.

For the simulator circuit, a different logic, also apparent to a worker skilled in the art, would be required to reduce the output by a selectable percentage for a selectable time with a selectable phase relative to the input sinusoid. Since it may be assumed that the input voltage would be steady during the test, no feedback is required in this case, and the pulse width need only be adjusted by an amount required to provide the percentage change desired, with the timing and length of the adjustment providing the phase and length of the simulated "dip".

It should be noted that, while the above discussion assumes that the frequency of the switching is held constant and the time of transition from one switch being closed to the other being closed varied, it would be equally valid to hold the time of transition constant and to vary the frequency, because either method would vary the duty cycle η of the switch.

It should also be noted that, while Figures 5 and 6 show the switch to be formed by an Insulated Gate Bipolar Transistor (IGBT) enclosed within a diode bridge, it is also possible to form series and parallel combinations with IGBT elements or Field Effect Transistors as shown in Figures 8a and 8b, and these possibilities and others as heretofore mentioned may be employed and even mixed in a single embodiment without departing from the essence of the invention. As those skilled in the art should easily understand, in the parallel arrangement the Field Effect Transistors 15 may be configured with diodes 16 to achieve the desired effect. These arrangements may even be more efficient. As one can easily understand, the diode bridge shown in Figures 5 and 6 has the advantage of requiring but a single switching element, with the diodes providing the alternating current capability. The diodes do, however, drop a certain small voltage. This voltage, multiplied by the load current, may represent a loss which is converted into heat in the diodes, and may need to be cooled as a result. As one can understand, the configurations in Figures 8a and 8b, while utilizing two switches, may present a smaller voltage drop than the diode bridge arrangement of Figures 5 and 6, and so may represent a smaller loss. That is, use of the switch elements of Figures 8a and 8b may generally result in a more efficient power regulator than possible using the diode bridge, although at a cost of additional switches and switch drive circuitry.

Figures 9a and 9b show two embodiments of a three-phase version of the ac regulator. In these embodiments each phase may be regulated independently, or control circuits may be employed which couple the actions of the three regulators 16. Figure 9a shows one arrangement in which the multiple phase supply (three phases are shown) is transformed by a y-delta transformer 18. The resulting signals are then regulated by conceptually separate regulators 16 as discussed earlier. As shown in Figure 9b a similar arrangement is accomplished for a delta-y transformer 17.

The discussion included in this application is intended to serve as a basic description. The reader should be aware that the specific discussion may not explicitly describe all embodiments possible; many alternatives are implicit. It also may not fully explain the generic nature of the invention and may not explicitly show how each feature or element can actually be representative of a broader function or of a great variety of alternative or equivalent elements. Again, these are implicitly included in this disclosure. Where the invention is described in device-oriented terminology, each element of the device implicitly performs a function. Additional apparatus claims may not only be included for the device described, but also additional method or process claims may be included to address the functions the invention and each element performs. Neither the description nor the terminology is intended to limit the scope of the claims which are supportable by this patent application.

It should also be understood that a variety of changes may be made without departing from the essence of the invention. Such changes are also implicitly included in the description. They still fall within the scope of this invention. A broad disclosure encompassing both the explicit embodiment(s) shown, the great variety of implicit alternative embodiments, and the broad methods or processes and the like are encompassed by this disclosure and.may be relied upon when drafting any additional claims for the patent. It should be understood that such language changes and broad claiming may be accomplished at any time during pendency of this application (or any continuations or divisional of it). Claims designed to cover numerous aspects of the invention both independently and as an overall system are to be understood as supported by this disclosure.

In addition, each of the various elements of the invention and claims may also be achieved in a variety of manners. This disclosure should be understood to encompass each such variation, be it a variation of an embodiment of any apparatus embodiment, a method or process embodiment, or even merely a variation of any element of these. Particularly, it should be understood that as the disclosure relates to elements of the invention, the words for each element may be expressed by equivalent apparatus terms or method terms -- even if only the function or result is the same. Such equivalent, broader, or even more generic terms should be considered to be encompassed in the description of each element or action. Such terms can be substituted where desired to make explicit the implicitly broad coverage to which this invention is entitled. As but one example, it should be understood that all actions may be expressed as a means for taking that action or as an element which causes that action. Similarly, each physical element disclosed should be understood to encompass a disclosure of the action which that physical element facilitates. Regarding this last aspect, the disclosure of a "switch" should be understood to encompass disclosure of the act of "switching" -- whether explicitly discussed or not -- and, conversely, were there only disclosure of the act of "switching", such a disclosure should be understood to encompass disclosure of a "switch." Such changes and alternative terms are to be understood to be explicitly included in the description.

The foregoing discussion and the claims which follow describe the preferred embodiments of the invention. Particularly with respect to the claims it should be understood that changes may be made without departing from their essence. In this regard it is intended that such changes would still fall within the scope of the present invention. It is simply not practical to describe and claim all possible revisions which may be accomplished to the present invention. To the extent such revisions utilize the essence of the invention each would naturally fall within the breadth of protection accomplished by this patent. This is particularly true for the present invention since its basic concepts and understandings are fundamental in nature and can be applied in a variety of ways to a variety of fields.

All these disclosed aspects may be claimed -- now or at a later stage of the application -- either separately or in various permutations or combinations. Further, to the extent the methods claimed in the present invention are not further discussed, they should be understood as natural outgrowths of the system or apparatus claimed. Therefore, separate and further discussion of the methods is unnecessary as they otherwise claim steps that are implicit in the use and application of the system or the apparatus claims. Furthermore, while many steps are organized in one logical fashion, other sequences may occur. Therefore, the method claims should not be construed to include only the order of sequence and steps presented. As to the claims' use of the term "comprise" or variations such as "comprises" or "comprising", unless the context otherwise requires, these terms are intended to imply the inclusion of a stated element or step or group of elements or steps but not the exclusion of any other element or step or group of elements or steps. Such terms should be interpreted in their most expansive form so as to afford the applicant the broadest coverage legally permissible in countries such as Australia and the like.

Thus, the applicant should be understood to have support to claim at least: i) a regulator device as herein disclosed and described, ii) the related methods disclosed and described, iii) similar, equivalent, and even implicit variations of each of these devices and methods, iv) those alternative designs which accomplish each of the functions shown as are disclosed and described, v) those alternative designs and methods which accomplish each of the functions shown as are implicit to accomplish that which is disclosed and described, vi) each feature, component, and step shown as separate and independent inventions, and vii) the various combinations and permutations of each of the above.

Claims

A method of simulation of disturbances on low frequency ac power sources across a load comprising:

a. supplying an input power having an alternation period;

b. storing energy from said input power in an energy storage element for a time short compared to said period;

c. discharging said energy into said load;

d. repeating (a)-(c) at a frequency substantially higher than the reciprocal of said period; and

e. adjusting the ratio of said time to the reciprocal of said frequency to produce a desired disturbance across said load.
The method of simulation of disturbances on low frequency ac power sources across a load as described in claim 1 wherein said energy storage element comprises an inductor.
The method of simulation of disturbances on low frequency ac power sources across a load as described in claim 1 or 2 wherein said frequency is in the range from 1 kHz to 1000 kHz.
The method of simulation of disturbances on low frequency ac power sources across a load as described in claim 1 or 2 wherein storing energy further comprises causing a charging semiconductor switch to conduct such that said energy storage element is connected to a source of said input power.
The method of simulation of disturbances on low frequency ac power sources across a load as described in claim 1 or 2 wherein discharging further comprises causing a discharging semiconductor switch to conduct such that said energy storage element is connected to said load.
A method of adjusting low frequency ac power factor comprising:

a. supplying an input power having an alternation period and a power factor;

b. storing energy from said input power in an energy storage element for a time short compared to said period;

c. discharging said energy into said load;

d. repeating (a)-(c) at a frequency substantially higher than the reciprocal of said period; and

e. adjusting the ratio of said time to the reciprocal of said frequency to bring said power factor to a desired value.
A simulator of disturbances on low frequency ac power sources across a load comprising:

a. a source of input power having an alternation period;

b. an energy storage element;

c. a first switch to cause said energy storage element to be connected across said input power for a time short compared to said period;

d. a second switch connected to cause discharging of said energy into said load;

wherein said switches operate at a frequency substantially higher than the reciprocal of said period and wherein the ratio of said time to the reciprocal of said frequency is adjusted to produce a desired disturbance across said load.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 7 wherein said energy storage element comprises an inductor.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 7 or 8 wherein said frequency is in the range from 1 kHz to 1000 kHz.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 7 or 8 wherein said first and second switches each comprise semiconductor switches.
A simulator of disturbances on low frequency ac power sources across a load comprising

a. a source of input power having an alternation period and a first and second lead;

b. an energy storage element connected in series with said first lead;

c. a first switch connected from said second lead to said first lead at a point after said energy storage element;

d. a second switch connected in series with said first lead at a point after said first switch

wherein said load is connected from said first lead to said second lead at a point after said second switch.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 11 wherein said energy storage element comprises an inductor.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 11 wherein said first and second switches comprise semiconductor switches.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 13 wherein said first and second semiconductor switches each comprise a diode bridge connected across a semiconductor switch element such that current always flows in said element in the same direction, while permitting current flow in said switch in alternating directions.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 13 wherein said first and second semiconductor switches each comprise a pair of Field Effect Transistors connected in series.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 13 wherein said first and second semiconductor switches each comprise a pair of the series combination of a diode and a Field Effect Transistor, said pair connected in parallel.
A simulator of disturbances on low frequency ac power sources across a load comprising:

a. a source of input power having an alternation period and having a first and second lead;

b. an first switch connected in series with said first lead;

c. a second switch connected from said second lead to said first lead at a point after said first switch;

d. an energy storage element connected in series with said first lead at a point after said first switch

wherein said load is connected from said first lead to said second lead at a point after said energy storage element.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 17 wherein said energy storage element comprises an inductor.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 17 wherein said first and second switches comprise semiconductor switches.
The simulator of disturbances on low frequency ac power sources across a load as described in claim 19 wherein said first and second semiconductor switches each comprise a diode bridge connected across a semiconductor switch element such that current always flows in said element in the same direction, while permitting current flow in said switch in alternating directions.