阅读说明：本技术 用于验证数字电能线完整性的方法 (Method for verifying integrity of digital power line ) 是由 斯坦利·玛丽尼埃克 乔纳森·凯西 斯蒂芬·伊夫斯 于 2018-04-26 设计创作，主要内容包括：通过检测或预防来确保在采样周期期间存在线电压干扰的情况下数字电力系统中传输线电压测量值的完整性,具体方式如下：(a)获取传输线电压的至少三个测量值,对这些测量值进行数值分析以产生多项式函数,并基于各个测量值的方差大小来估算该多项式函数的精度；(b)在该采样周期期间对该传输线施加负偏压或正偏压,并获取电压测量值以确定施加该偏压后的电压变化率；(c)将第一传输线上的第一采样周期的开始时间参照第二传输线上的第二采样周期进行移位以减少传输线上的采样周期的重叠；和/或(d)使第一传输线和第二传输线上各自的采样周期的开始时间同步。(The integrity of transmission line voltage measurements in a digital power system in the presence of line voltage disturbances during a sampling period is ensured by detection or prevention by: (a) obtaining at least three measurements of the transmission line voltage, numerically analyzing the measurements to produce a polynomial function, and estimating the accuracy of the polynomial function based on the magnitude of variance of the respective measurements; (b) applying a negative or positive bias voltage to the transmission line during the sampling period and obtaining a voltage measurement to determine a rate of change of the voltage after the bias voltage is applied; (c) shifting a start time of a first sampling period on a first transmission line with reference to a second sampling period on a second transmission line to reduce overlap of the sampling periods on the transmission lines; and/or (d) synchronizing the start times of the respective sampling periods on the first and second transmission lines.)

1. A method for ensuring the integrity of transmission line voltage measurements in a digital power system comprising one or more transmitters, the method comprising:

monitoring and controlling the voltage on the respective transmission line using each transmitter;

ensuring the integrity of transmission line voltage measurements in the presence of line voltage disturbances during a sampling period includes at least one of the following four methods:

a) obtaining at least three measurements of the transmission line voltage during the sampling period, wherein the voltage measurements may be affected by electrical interference; numerically analyzing the measurements to produce a polynomial function that approximates the unperturbed transmission line voltage measurements; estimating the accuracy of the polynomial function based on the magnitude of the variance of the respective measurements from the approximation; and interrupting power to the transmission line if the estimated accuracy does not meet the minimum accuracy requirement;

b) applying a negative bias or a positive bias to the transmission line during the sampling period; obtaining a voltage measurement to determine a rate of change of voltage after the bias voltage is applied; and interrupting power to the transmission line if the rate of change of voltage exceeds predetermined minimum and maximum values;

c) the digital power system at least comprises a first transmission line and a second transmission line, and the starting time of a first sampling period on the first transmission line is shifted with reference to a second sampling period on the second transmission line so as to reduce the overlapping of the sampling periods on the two transmission lines, thereby preventing electromagnetic noise from being induced from one transmission line to the other transmission line; and

d) wherein the digital power system comprises at least a first transmission line and a second transmission line, the start time of the first sampling period on the first transmission line is synchronized with the start time of the sampling period on the second transmission line to allow electromagnetic noise from the two transmission lines to decay to an acceptable value before the end of the sampling period, thereby making at least a portion of the remaining sampling period available for interference-free voltage measurement.

2. The method of claim 1, wherein the numerical analysis of the voltage measurements takes the form of linear regression.

3. The method of claim 1, wherein the numerical analysis of the voltage measurements takes the form of a non-linear regression.

4. The method of claim 1, wherein the numerical analysis of the voltage measurements takes the form of digital filtering.

5. The method of claim 1, wherein the numerical analysis of the transmission line voltage is passed through an analog filter circuit before being measured for the numerical analysis.

6. The method of claim 1, wherein the bias voltage is generated by an operational amplifier circuit.

7. The method of claim 1, wherein the bias voltage is generated by a voltage divider circuit.

8. The method of claim 7, wherein at least one resistance value in the voltage divider circuit is generated by controlling the resistance of a transistor.

9. The method of claim 1, wherein the bias voltage is generated by a power circuit.

10. The method of claim 1, wherein the integrity of transmission line voltage measurements in the presence of line voltage interference during the sampling period is ensured by: (a) obtaining at least three measurements of the transmission line voltage during the sampling period, wherein the voltage measurements may be affected by electrical interference; numerically analyzing the measurements to produce the polynomial function, the polynomial function approximating disturbance-free transmission line voltage measurements; estimating the accuracy of the polynomial function based on the magnitude of the variance of the respective measurements from the approximation; and interrupting power to the transmission line if the estimated accuracy does not meet the minimum accuracy requirement.

11. The method of claim 1, wherein the integrity of transmission line voltage measurements in the presence of line voltage interference during the sampling period is ensured by: (b) applying a negative bias or a positive bias to the transmission line during the sampling period; obtaining a voltage measurement to determine a rate of change of voltage after the bias voltage is applied; and interrupting power to the transmission line if the rate of change of voltage exceeds predetermined minimum and maximum values.

12. The method of claim 1, wherein the integrity of transmission line voltage measurements in the presence of line voltage interference during the sampling period is ensured by: (c) the start time of the first sampling period on the first transmission line is shifted with reference to the second sampling period on the second transmission line to reduce the overlap of the sampling periods on the two transmission lines, thereby preventing electromagnetic noise from being induced from one transmission line to the other.

13. The method of claim 1, wherein the integrity of transmission line voltage measurements in the presence of line voltage interference during the sampling period is ensured by: (d) the start time of the first sampling period on the first transmission line is synchronized with the start time of the sampling period on the second transmission line to allow the electromagnetic noise from the two transmission lines to decay to an acceptable value before the end of the sampling period, thereby making at least a portion of the remaining sampling period available for interference-free voltage measurement.

Background

Digital power or digital electrical energy may be characterized as any power format that distributes power in discrete, controllable energy units. Packet Energy Transfer (PET) is a novel digital power protocol disclosed in U.S. patent No. 8,068,937, U.S. patent No. 8,781,637 (ivus 2012), and international patent application PCT/US2017/016870 filed on 7.2.2017.

Compared to conventional analog power systems, a major factor in identification in digital power transmission systems is the separation of electrical energy into discrete units; and the individual energy units may be associated with analog and/or digital information that may be used for purposes of optimizing safety, efficiency, resiliency, control, or routing. Since energy in a PET system is transferred as discrete quantities or quanta, such energy may be referred to as "digital power" or "digital electrical energy.

As described in itu 2012, the power supply controller and the load controller are connected by a power transmission line. The power supply controller of ivus 2012 periodically isolates (disconnects) the power transmission line from the power supply and analyzes at least the voltage characteristics present at the terminals of the source controller before and immediately after the line is isolated. The time period during which the power line is isolated is referred to as a "sampling period" by the ivus 2012, and the time period during which the power supply is connected is referred to as a "transfer period". The rate of rise and decay of the voltage on the line before, during, and after the sampling period reveals whether a fault condition exists on the power transmission line. Measurable faults include, but are not limited to, short circuits, high line resistance, or the presence of individuals improperly contacting the lines.

The ivus 2012 also describes digital information that can be sent between the power supply and the load controller over the power transmission line to further enhance safety or provide general characteristics of energy transfer, such as total energy or voltage at the load controller terminals. One method for communicating over the same digital power transmission line used for power is further described and improved in U.S. patent No. 9,184,795 (the affton patent).

One application of digital power distribution systems is for safely distributing Direct Current (DC) power from the source side to the load side of the system in digital format and at elevated voltages.

U.S. published patent application No. 2016/0134331a1 (ivus power element) describes packaging power side components of ivus 2012 in various configurations into devices known as digital power transmitters.

Us patent No. 9,419,436 (the ivus receiver patent) describes packaging various configurations of the load side components of ivus 2012 into a device called a digital power receiver.

Disclosure of Invention

The method described below is based on the earlier work of ivus 2012 and, with a view to the novel method, minimizes errors in transmission line fault detection. These errors may be caused by electrical noise or other disturbances that may affect the integrity of the data sensed from the transmission line when performing the packet energy transfer protocol.

Digital power or digital electrical energy may be characterized as any power format that distributes power in discrete, controllable energy units. Digital power systems periodically isolate the transmission line from the power supply and load to analyze characteristics of the analog line that reflect possible faults or human contact with the transmission line. The detection of line faults involves periodic measurement of the transmission line voltage. However, actual transmission line voltage measurements are often affected by electrical noise or unwanted oscillations. The disclosed method can be used to ensure the integrity of analog measurements for fault detection, thereby preventing false-positive or false-negative line fault determinations.

Methods for ensuring the integrity of data used to determine transmission line faults when performing packet energy transfer are described herein, wherein various embodiments of the methods and apparatus for performing the methods may include some or all of the elements, features, and steps described below.

In an embodiment of a method for ensuring the integrity of transmission line voltage measurements in a digital power system including one or more transmitters, the voltage on one or more transmission lines is monitored and controlled using the respective transmitter. The integrity of transmission line voltage measurements in the presence of line voltage interference during a sampling period is ensured by using at least one of the following four methods.

In a first method, at least three measured values of the transmission line voltage are acquired during the sampling period, wherein these voltage measured values may be influenced by electrical disturbances. The measurements are numerically analyzed to produce a polynomial function that approximates the interference-free transmission line voltage measurements. Estimating the accuracy of the polynomial function based on the magnitude of the variance of the respective measurements from the approximation, and interrupting the power to the transmission line if the estimated accuracy does not meet a minimum accuracy requirement.

In a second method, a negative or positive bias is applied to the transmission line during the sampling period. Obtaining a voltage measurement to determine a rate of change of voltage after the bias voltage is applied; and interrupting power to the transmission line if the rate of change of voltage exceeds predetermined minimum and maximum values.

In a third method, wherein the digital power system includes at least a first transmission line and a second transmission line, a start time of a first sampling period on the first transmission line is shifted with reference to a second sampling period on the second transmission line to reduce an overlap of the sampling periods on the two transmission lines, thereby preventing electromagnetic noise from being induced from one transmission line to the other transmission line.

In a fourth method, wherein the digital power system includes at least a first transmission line and a second transmission line, the start time of a first sampling period on the first transmission line is synchronized with the start time of a sampling period on the second transmission line to allow electromagnetic noise from the two transmission lines to decay to an acceptable value before the end of the sampling period, thereby making at least a portion of the remaining sampling period available for interference-free voltage measurement.

In performing the Packet Energy Transfer (PET) protocol inherent to digital power, a portion of the total energy packet period is allocated for transferring energy from the power source to the load. This portion is called the transfer period. The remaining time in the packet cycle is allocated for detecting failures and for transferring data. This portion of the packet is referred to as the sampling period. In one embodiment, a controller on the power supply side of the system monitors the decay of the transmission line voltage during the sampling period. The change in the decay rate may indicate various fault conditions including a short circuit or a human contact with the transmission line conductor.

There are many practical considerations in the PET protocol related to ensuring fault detection integrity. The first consideration is to take a valid measurement of the transmission line voltage during the sampling period when oscillations occur on the transmission line due to "reflected waves". When the current pulse reaches the end of the line and is reflected back to the original position, a reflected wave is generated. When these reflections are observed at any point of the transmission line, they will appear as voltage oscillations. These oscillations may cause errors in determining the line voltage decay rate during the PET sampling period.

The second consideration is that the line-to-line capacitance associated with long transmission lines is too large. The capacitance may reach a level that masks the effects of the decrease in line-to-line resistance.

A third consideration is the coupling of electromagnetic interference (EMI) to the transmission line pair. Interference may originate from other transmission line pairs in close proximity, including other digital power transmission line pairs.

The methods described herein address these considerations through prevention and detection.

From a preventive point of view, multiple parallel transmission lines transmitting digital electrical energy are interleaved, which means that the start of an energy packet in one transmission line is intentionally shifted in time relative to the other transmission lines. Specifically, the sampling periods of the multiple energy packets are arranged as many as possible so that they do not occur simultaneously in the closely adjacent transmission lines. As will be described in more detail below, transmission line reflections produce oscillations that are the source of EMI; and the EMI may cause interference in adjacent transmission line pairs. Line reflections are stimulated by a sudden decrease in line current caused by the start of the sampling period. If EMI occurs during the sampling period, the adjacent transmission lines containing digital power are most susceptible to interference from EMI because the transmission line series impedance is much higher in this portion of the power packet, meaning that EMI may be generated with less power.

Two detection methods are described herein.

A first detection method uses a bias circuit to drive the transmission line pair to a desired voltage. The simplest form of bias circuit is a resistor divider. By measuring the transmission line voltage while applying the bias voltage for a known period of time, a value indicative of the impedance between the lines can be calculated. If the value exceeds a predetermined acceptable value, a fault will be registered and power to the transmission line interrupted. In addition to detecting faults on the transmission line, the measurement is also used to detect hardware problems, such as short circuit faults of line disconnection equipment. If the line break device does not successfully interrupt the current to the transmission line, the line voltage will not decay during the measurement period, indicating that the line break device or the supported circuitry has been damaged.

Because the line is actively biased to the target voltage, this approach can overcome some of the effects of EMI or high capacitance on the transmission line. The tradeoff between using a bias and simply opening the power disconnect switch is that the bias current may mask the effect of low current line-to-line faults on the transmission line because the system must distinguish the difference between the fault current and the bias current to properly register the fault.

A second detection method involves determining whether the voltage measured on the transmission line during the sampling period is too noisy to support a valid measurement. This method, referred to as anomaly detection, quantifies the deviation of the transmission line voltage from an ideal reference line during a sampling period. If the deviation exceeds a predetermined maximum, the measurement is deemed invalid. After a predetermined number of invalid measurements, the line is deemed to be in a fault state and power to the transmission line will be interrupted.

Drawings

Fig. 1 is a block diagram of an embodiment of a secure power distribution system.

Fig. 2 is a graphical representation of a packet energy transfer voltage (PET voltage) waveform.

Figure 3 shows the effect of line oscillation on the PET voltage waveform.

Fig. 4 shows the interleaving of two PET voltage waveforms.

Fig. 5 illustrates how one PET waveform causes noise on the neighboring waveforms.

Fig. 6 illustrates limitations in interleaving three PET waveforms.

Fig. 7 shows the combined interleaving and synchronization of the three PET waveforms.

Fig. 8 is a block diagram of a PET system with a synchronization signal.

FIG. 9 illustrates the effect of high line capacitance in a PET waveform.

In the drawings, like numerals refer to the same or similar parts throughout the different views; and prime notation is used to distinguish between different embodiments of the same item or items sharing the same reference number. The figures are not necessarily to scale; rather, emphasis is placed upon illustrating the particular principles of the examples discussed below. For any figure that includes text (words, reference numbers, and/or numbers), alternative versions of the figure without the text should be understood as part of the present disclosure; and thus may be replaced by a formal alternative drawing without such text.

Detailed Description

The foregoing and other features and advantages of various aspects of the present invention will be apparent from the following more particular description of various concepts and specific embodiments of the invention within the broader scope of the invention. The various aspects of the subject matter introduced above and discussed in greater detail below may be implemented in any of numerous ways, as the subject matter is not limited to any particular implementation. Examples of specific embodiments and applications are provided primarily for purposes of illustration.

Unless otherwise defined, used, or characterized herein, terms (including technical and scientific terms) used herein are to be construed as having a meaning that is consistent with their accepted meaning in the context of the relevant art and are not to be construed in an idealized or overly formal sense unless expressly so defined herein.

The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of example embodiments. As used herein, singular forms such as "a" and "an" are intended to include the plural forms as well, unless the context indicates otherwise. In addition, the terms "comprising," "including," and "comprising" specify the presence of stated elements or steps, but do not preclude the presence or addition of one or more other elements or steps.

A representative digital power system as initially described in ivus 2012 is shown in fig. 1. The system comprises a power supply 1 and at least one load 2. The PET protocol is activated by operating the switch 3 to periodically disconnect the power supply from the power transmission line. When the switch is in the open (non-conducting) state, the line also passes through the isolating diode (D)₁)4 from any stored energy that may reside at the load 2.

Igfsh 2012 provides several versions of alternative switches that can be substituted for D₁And all versions can produce similar results when used in the presently described method. Capacitor (C)₃) And 5 denotes an energy storage element on the load side of the circuit.

The transmission line has a natural line-to-line resistance (R)₄)6 and line-to-line capacitance (C)₁)7. The PET system architecture as described by Ifss 2012 adds an additional line-to-line resistance (R)₃)8 and line-to-line capacitance (C)₂)9. At the moment when the switch 3 is opened, C₁And C₂Has been stored to react with R₄And R₃The added value of (c) is inversely proportional to the rate-decaying charge. Due to the isolation of the diode (D)₁)4 reverse blocking behavior, capacitor (C)₃)5 do not pass through R₃And R₄And discharging is performed. Capacitance (C)₁And C₂) Is proportional to the voltage across them and can be measured at points 16 and 17 by the power controller 18 or the load controller 19.

As described in Igves 2012, stored in C₁And C₂A change in the decay rate of the energy in (a) may indicate the presence of a crossline fault on the transmission line. The difference between normal operation and failure as proposed by ibufss 2012 is shown in fig. 2.

Referring again to fig. 1, the switch (S1)3, the power controller 18, the resistor (R)₁)10, switch (S2)11, and resistor (R)₃) The combination of 8 may be referred to as a transmitter 20. Switch (S4)15, resistor (R)₅)14, load controller 19, diode (D)₁)4, capacitance (C)₂)9, and a capacitor (C)₃) The combination of 5 may be referred to as a receiver 21.

FIG. 3 illustrates a first practical consideration when performing PET-the oscillation of the transmission line voltage due to reflection or EMI. Oscillations can affect the integrity of fault detection, increasing the difficulty of extracting the voltage decay rate caused by normal energy dissipation in the line capacitance due to the interference caused by the oscillations. The oscillations may produce false or false-negative test results because the abnormally attenuated transmission line voltage during the sampling period indicates a transmission failure. When the oscillation amplitude is small, analog or digital filtering can improve the measurement; however, if the oscillations are large, the analog measurement may become unusable.

The oscillations shown in fig. 3 may come from electromagnetic interference outside the transmission line or from other closely adjacent pairs of transmission lines, including other pairs of digital power transmission lines. In particular, longer transmission lines are subject to "reflections", wherein the current pulse will reach the end of the line and then reflect back to the original position. When these reflections are observed at any point of the transmission line, they will appear as voltage oscillations. The oscillation is exacerbated by electromagnetic radiation reflected from transmission lines in immediately adjacent pairs of digital power lines. If EMI occurs during the sampling period, the adjacent transmission line containing the digital power is most susceptible to EMI interference because the transmission line impedance is much higher in this portion of the power packet, allowing interference to build up with less power.

As summarized previously, the methods described herein can apply both the prevention method and the detection method to manage the actual operational aspects of the digital power on the transmission line.

One method of preventing ringing interference is illustrated in fig. 4, where two adjacent pairs of digital power transmission lines are offset or interleaved in time so that their sampling periods do not occur simultaneously. This offset allows the oscillation to decrease before the end of the sampling period, as illustrated by point 26, allowing the line attenuation to be effectively measured once the oscillation amplitude drops to an acceptable level. Without interleaving, the sampling periods may overlap; and electromagnetic radiation from the first pair may lengthen the oscillation of the second pair, possibly until the oscillation consumes a full sampling period, as shown at point 28 of fig. 5.

An acceptable but less desirable method for controlling line oscillation is to synchronize the energy packets of the two transmission lines so that the sampling periods begin at the same time. In this way, line oscillations will occur and decay at about the same rate, allowing measurements to be taken at a later time in the sampling period when the oscillations decay to an acceptable level.

In fact, for a large number of transmission line pairs, both the synchronization technique and the interleaving technique may be used, because as the number of transmission line pairs increases, it is not possible to avoid overlap using the interleaving technique alone. In the example of fig. 6, it is not possible to shift more than the two transmission line packets shown, because there are no remaining sampling periods in any of the three waveforms that would not be affected by the start of a sampling period in another adjacent transmission line. The overlap will again lengthen the oscillation 28 during the sampling period. To solve this problem, as shown in fig. 7, the sampling periods of two of the transmission lines may be synchronized, and the sampling period of the third transmission line may be offset or interleaved.

Referring to fig. 1, to facilitate the interleaving function, the transmitter of the present embodiment incorporates a synchronization input to the power supply controller 18. Referring to fig. 8, in certain embodiments, the master controller 30 generates a synchronization signal, which may be in the form of a pulse waveform or data element embedded in the serial communication stream. Each transmitter 20, 20 ', 20 "holds an identifier in its individual controller that associates the controller with its respective transmission line 32, 32', 32". When the transmitter controller detects the synchronization pulse, the transmitter controller will apply the appropriate offset to the start time of the energy packet according to its sequential position of the transmission line in the transmission line group 32, 32', 32 ".

Fig. 9 illustrates a second consideration when performing measurements during a sampling period. As shown by the attenuation at point 34 in fig. 9, the attenuation of the transmission line voltage during the sampling period may be very small when the transmission line capacitance is high relative to the lower capacitance line. This makes the line-to-line fault detection less sensitive, which may result in missing a fault condition.

FIG. 1 helps to show a first method for detecting high line capacitance and other line-to-line faults. Increasing the line bias provides additional current to charge or discharge the line capacitance. The power controller 18 functions to close the solid-state switch (S3)13, which connects the resistor (R)₂)12 are connected across the transmission line conductors. This is through R₂The "pull down" effect of (a) provides a negative bias to the transmission line. By closing solid state switch (S3)13 and solid state switch (S2)11 simultaneously, another bias circuit can be created that provides a greater range of control over the bias voltage set point, which forms a voltage divider comprising resistor (R1)10 and resistor (R2)12 on the transmission line positive pole.

The voltage decay rate after the bias voltage is applied during the sampling period is then compared to predetermined maximum and minimum values. If the decay rate is too high or too low (i.e., above a predetermined maximum or below a predetermined minimum), the decay rate is indicative of a line fault. The failure caused by high attenuation may be caused by human contact or foreign objects placed on the transmission line. Low attenuation faults may be caused by excessive line capacitance or hardware faults. Then, the power controller 18 may interrupt the current to the transmission line by opening the disconnection switch (S1) 3.

A second detection method involves determining whether the voltage measured on the transmission line during the sampling period is too noisy to support a valid measurement. This method, referred to as anomaly detection, quantifies the deviation of the transmission line voltage from an ideal reference line during a sampling period. If the deviation exceeds a predetermined maximum, the measurement is deemed invalid. After a predetermined number of invalid measurements, the line is deemed to be in a fault condition; and power to the transmission line will be interrupted. A preferred method is to accumulate a series of voltage samples during a sampling period and compare these samples to an imaginary, non-vertical straight line using numerical regression, as shown by the dashed line 24 in figure 3. A line represents the normal attenuation rate of a transmission line if the line is not disturbed by line reflections or electromagnetic interference (EMI). There are a variety of methods known to those skilled in the art for performing linear numerical regression. One method that may be used in the current method is the "least squares" method. If there is little EMI or line oscillation, the variance that exists between the imaginary line and the actual data sample will be small, since most of the data samples will be very close to the line. In the case of noisy or oscillating transmission lines, the variance or "residual" can be large; since many samples will be far from the notional line. Determining coefficient (r) commonly used in linear regression²) A model for predicting whether a desired line can be used as a potential actual decay rate of a transmission line during a sampling period is expressed as follows:

r²＝Cov(x，y)²/[Var(x)²·Var(y)²]，

wherein:

r²to determine the coefficients;

x is the sample time relative to the start of the sample period;

y is the voltage value of the sample taken at time x;

cov (x, y) is the covariance of x and y;

var (x) is the variance of x; and is

Var (y) is the variance of y.

The calculation of variance and covariance is well known to those skilled in the art of numerical regression. r is²A low value of (c) means that the notional line is not a viable model for potential attenuation of the transmission line voltage. If r is²If the value of (d) is lower than a predetermined value, the power supply controller will register a fault; and the power supply controller will interrupt power to the transmission line.

Summary, ramifications and scope:

the power controller 18 and the load controller 19 may include logic devices such as microprocessors, microcontrollers, programmable logic devices, or other suitable digital circuitry for executing control algorithms. The load controller 19 may take the form of a simple sensor node that collects data relating to the load side of the system and does not necessarily require a microprocessor.

The controllers 18 and 19 may be computing devices, and the systems and methods of the present disclosure may be implemented in a computing system environment. Examples of well known computing system environments and their components that may be suitable for use with the systems and methods include, but are not limited to, personal computers, server computers, hand-held or laptop devices, tablet computing devices, smart phones, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputers, mainframe computers, distributed computing environments that include any of the above systems or devices, and the like. A typical computing system environment and its operation and components are described in many prior patents, such as U.S. patent No. 7,191,467 owned by Microsoft corporation (Microsoft Corp.).

The methods may be performed by non-transitory computer-executable instructions, such as program modules. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular data types. The methods may also be practiced in distributed computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote computer storage media including memory storage devices.

The processes and functions described herein may be stored in a computer in the form of software instructions in a non-transitory manner. The components of a computer may include, but are not limited to, a computer processor, a computer storage medium serving as a memory, and a system bus that couples various system components including the memory to the computer processor. The system bus may be any of several types of bus structures including: a memory bus or memory controller, a peripheral bus, and a local bus using any of a variety of bus architectures.

A computer typically includes one or more of a variety of computer readable media accessible by the processor and including both volatile and nonvolatile media, and removable and non-removable media. By way of example, computer readable media may comprise computer storage media and communication media.

Computer storage media may store software and data in a non-transitory state, and includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of software and data, such as computer readable instructions, data structures, program modules, or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed and executed by a processor.

Memory includes computer storage media in the form of volatile and/or nonvolatile memory such as Read Only Memory (ROM) and Random Access Memory (RAM). A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements within the computer, such as during start-up, is typically stored in ROM. RAM typically contains data and/or program modules that are immediately accessible to and/or presently being operated on by the processor.

The computer may also include other removable/non-removable, volatile/nonvolatile computer storage media such as (a) a hard disk drive that reads from or writes to non-removable, nonvolatile magnetic media; (b) a disk drive that reads from or writes to a removable, non-volatile disk; and (c) an optical disk drive that reads from or writes to a removable, nonvolatile optical disk such as a CD ROM or other optical media. The computer storage media may be coupled to the system bus by a communication interface, which may include, for example, electrically conductive wires and/or fiber optic channels for transmitting digital or optical signals between the components. Other removable/non-removable, volatile/nonvolatile computer storage media that can be used in the exemplary operating environment include magnetic tape cassettes, flash memory cards, digital versatile disks, digital video tape, solid state RAM, solid state ROM, and the like.

The drives and their associated computer storage media provide storage of computer readable instructions, data structures, program modules and other data for the computer. For example, a hard disk drive, internal or external to the computer, may store an operating system, application programs, and program data.

The synchronization signal for synchronizing or offsetting the PET waveforms described herein and shown in fig. 6 may also be generated by one of the power controllers controlling the transmission lines 32, 32', 32 ", thereby eliminating the need for a separate master controller. The power controller that generates the signal will become the master controller. There are several ways to determine which controller is the master controller. For example, the power controller with the lowest serial number may assume the primary role.

The bias circuits described herein may be constructed using an active power supply or operational amplifier circuit designed to drive the transmission line voltage to a predetermined voltage set point. Although more complex than a simple voltage divider circuit, active devices (e.g., operational amplifiers) can drive the transmission line voltage to the target set point faster than resistive voltage dividers.

An alternative method of constructing a resistive divider bias circuit is to employ a partially enhanced solid state switch 3 (e.g., S1 of fig. 1). If the switch (S1)3 is implemented as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), the device is partially enhanced by using a voltage lower than the normal gate drive voltage. In the partially enhanced state, the MOSFET behaves like a resistor.

The linear regression method described herein for deriving the notional line of transmission line attenuation may also be implemented by analog filtering circuitry or digital filtering algorithms. Linear regression is described in this specification because the power controller requires minimal processor resources to execute the algorithm. However, many numerical regression techniques well known to those skilled in the art may be employed. These techniques can be generally classified as linear, multi-linear, and non-linear numerical regression.

In describing embodiments of the present invention, specific terminology is employed for the sake of clarity. For the purposes of this description, specific terms are intended to include at least technical and functional equivalents that operate in a similar manner to accomplish a similar result. In addition, in some instances where a particular embodiment of the invention includes multiple system elements or method steps, those elements or steps may be replaced with a single element or step. Also, a single element or step may be substituted with a plurality of elements or steps serving the same purpose. Further, while the invention has been shown and described with reference to specific embodiments thereof, it will be understood by those skilled in the art that various substitutions and alterations in form and details may be made therein without departing from the scope of the invention. Still further, other aspects, functions, and advantages are within the scope of the invention; and not necessarily all embodiments of the invention achieve all advantages or achieve all of the features described above. In addition, steps, elements, and features discussed herein in connection with one embodiment may be equally used in connection with other embodiments. The contents of references (including literature references, journal articles, patents, patent applications, etc.) cited throughout this document are hereby incorporated by reference in their entirety for all purposes; and all suitable combinations of embodiments, features, characteristics and methods from these references and this disclosure may be included in embodiments of the invention. Still further, the components and steps identified in the background section are integral to the present disclosure and may be used in conjunction with or instead of the components and steps described elsewhere in the present disclosure within the scope of the present invention. In the method claims which recite a plurality of stages in a specific order (or in the case of methods recited elsewhere) with or without the addition of ordinal preface characters to facilitate reference, the stages should not be construed as limited in time to the order in which they are recited unless otherwise indicated or implied by terms or phrases.