Note: Descriptions are shown in the official language in which they were submitted.
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DISTRIBUTED WIRELESS HOME AND COMMERCIAL
ELECTRICAL AUTOMATION SYSTEMS
Copyright Notice
[0002] 2005 Lagotek Corporation. A portion of the disclosure of this patent
document contains material that is subject to copyright protection. The
copyright
owner has no objection to the facsimile reproduction by anyone of the patent
document or the patent disclosure, as it appears in the Patent and Trademark
Office
patent file or records, but otherwise reserves all copyright rights
whatsoever. 37 CFR
1 _71(d).
Technical Field
[0003] The invention pertains to control systems for controlling various
electrical
loads, apparatus and systems in the context of home and commercial automation,
with particular focus on improvements in user convenience, energy efficiency
and
refiabiiitv.
Background of the Invention
[0004] Home automation heretofore is either very limited, to basic tasks such
as
remote control of light dimmers and switches, or it involves complicated,
expensive,
custom hardware and software The known home automation systems have very
limited "inteiiigence" and awkward interfaces. Simple wireless modules for
lights and
household appliances are commercially available from Intermatic Incorporated
of
Spring Grove, IL. See www.intermatic.com. Other wireless light modules
including
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dimmers are available from Lutron and Zwave. It is well
known that harmonic interference on AC power lines causes
heat loss inefficiencies, and undue wear on equipment such
as transformers. Harmonics are caused by non-linear loads,
such as typical light dimmers, because they actively switch
the power on and off to adjust the light level, as
distinguished from a passive regulator such as a
potentiometer or rheostat which, although resistive and
therefore linear, is highly energy inefficient.
[0005] Passive solutions, such as filters, are known for
reducing harmonic distortion, but they have limitations and
also dissipate energy. Active solutions have been developed
for reducing harmonics in 4-wire, 3-phase systems, as taught
in U.S. Patent No. 5,568,371 to Pitel et al. That solution,
however, is not applicable to the usual single-phase
household circuit. Moreover, Pitel et al. describe an
active filter that requires substantial hardware housed in a
separate box.
[0006] The need remains for improvements in home and
commercial automation to reduce costs, enable a wide variety
of applications without custom hardware development, improve
user convenience and comfort, as well as reliability.
Summary
According to one broad aspect, the invention
provides a method for reducing harmonics in residential
power circuits thereby saving energy by reducing dissipation
in distribution transformers that supply such circuits, the
method comprising: monitoring current-versus-phase
characteristics of an electrical current through a single-
phase load circuit in a residential power circuit; providing
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a controllable power regulator for each of at least two non-
linear loads in the load circuit; and responsive to said
monitoring step, controlling the power regulators to effect
a corresponding selected start phase in each power
regulator, the start phases being selected as different from
one another so as to reduce harmonics in the power circuit.
According to another broad aspect, the invention
provides a method for reducing harmonics in residential
power circuits thereby saving energy by reducing dissipation
in distribution transformers that supply such circuits, the
method comprising: monitoring current-versus-phase
characteristics of an electrical current through a single-
phase load circuit in a residential power circuit, where the
load circuit includes a non-linear load; providing a
controllable power regulator coupled to a linear load in the
load circuit; and responsive to said monitoring step,
controlling the power regulator so as to regulate power
supplied to the linear load so as to minimize harmonic
distortion that would otherwise arise in the load circuit
from the non-linear load.
[0007] The present invention is directed in various
aspects to a variety of improvements in home or commercial
automation and energy savings. Additional aspects and
advantages will be apparent from the following detailed
description of preferred embodiments, which proceeds with
reference to the accompanying drawings.
Brief Description of the Drawings
[0008] Fig. lA is a front plan view illustrating
replacement of a conventional light switch with a central
controller.
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[0009] Fig. 13 is an exploded view illustrating a central
controller sized and arranged for installation in lieu of a
conventional light switch or outlet in a standard home
electrical box.
5[0010] Figs. 2A-2C illustrate examples of front panel
display content of a central controller.
[0011] Fig. 3 is one example of a home automation network
illustrating application of various components including
integrated as well as external wireless controllers.
[0012] Fig. 4 is a functional hardware block diagram of
one example of a central controller consistent with the
present invention.
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[0013] Fig. 5 is a simplified residential floor plan illustrating an example
of an
HVAC application of the invention for improved convenience and energy
efficiency.
[0014] Fig. 6 is a simplified schematic diagram illustrating an asymmetric
biprocessor architecture of a central controller in accordance with one aspect
of-the
invention.
[0015] Fig. 7A shows linear loads in a single-phase A.C. power circuit.
[0016] Fig. 7B shows the essentially sinusoidal electrical cun-entwaveform in
the
circuit of FIG. 7A.
[0017] FIG. 8A illustrates a plurality of non-(inear loads, here conventional
light
dimmers each set to 33% brightness.
[0018] FIG. 8B shows the resulting non-linear electrical current waveform
through
the loads of FIG. 8A.
[0019] FIG. 9A illustrates a system in accordance with one embodiment of the
present invention for normalizing non-linear loading in a single-phase power
circuit to
reduce harmonic distortions.
[0020] FIG. 9B shows the resulting load current using intelligent controliers
for
phase control to linearize the load.
[0021] FIG. 10 illustrates a system arranged for regulating a resistive load
so as
to compensate for one or more non-linear loads in the same circuit.
[0022] FIG. 11 shows illustrative waveforms and communication paths for the
system of FIG. 10.
[0023] FIG. 12 shows a waveform generated by the central controller for
normalizing the circuit of FIGS. 10 and 11 by regulating the resistive load.
Detailed Description of Preferred Embodiments
[0024] Nomenclature Note: In the provisional application, we used the term
"Control Panel" to refer to "microprocessor based electronic device, capable
of
running operating systems which supports the wireless protocol, graphical user
interface, touch screen functionality ...". (Provisional page 3.) In the
present
application, we will instead use the term "central controlier" to refer to
various
devices and embodiments functionally similar to what was previously called the
"Control Panel". This is to avoid confusion as the typical Central Controller,
in
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accordance with some embodiments of the invention, will itself include a front
panel
or control panel that provides an interface to the controller.
[0025] Thus "control panel" will be used herein consistent with its ordinary
meaning. For example, in one preferred embodiment, a central controller is
disposed in a standard electrical box, and the front panel of the central
controller is
installed over it, similar to a conventional light switch cover plate. The
term "central
controller" is not intended to imply that only one central controller can be
used in a
given installation such as a home or office. To the contrary, in most cases, a
pluraiity of central controllers will be deployed so as to form a distributed
or mesh
network, communicating with one another as further described later. That said,
a
single central controller can be used in smaller applications.
[0026] The provisional application also defined a "wireless controller" as,
"any
chip implementing one or more of several radio interfaces to allow
communication
over wireless links with various communication networks supporting the
wireless
protocol." This may be confusing, both internally and because the typical
central
controller described herein in some embodiments is correctly characterized as
wireless. In this document, we will use "wireless transceiver" to refer to
apparatus
that implements communication over a wireless channel, which may comprise an
access point, for example in the case of 802.11 implementations, or not, as in
the
case of Bluetooth or other ad hoc wireless protocols.
[0027] The central controller preferably includes one or more wireless
transceivers for communication with other central controllers in the same
network,
and for communications with various other components, some of which are
"controllers" (but not central controllers). The central controller(s) is
where the
user(s) mainly interface with the system. Other controliers, such as dimmers,
respond to commands from a central controller to operate lights or other
electrical
loads. Controllers can be deployed for various electrical and mechanical
tasks, as
further described below.
[0028] In accordance with the present invention, various embodiments of a
central controller are disclosed. The central controller preferably is
wireless, but it
can be hardwired for communications. Other particulars of preferred
embodiments
are as follows.
[0029] Basically, the central controller is a microprocessor-based electronic
device to enabie home or commercial automation functionality. It is the main
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hardware component of a home automation network, although as noted there can
be
more than one central controller. The central controller preferably executes
at least
one industry standard operating system, so that it provides an "open platform"
for
third party application software developers. Some of those applications will
include
lighting (both interior and exterior of a structure), HVAC (heating,
ventilation and air
conditioning), security (audio, motion detecting, video surveillance, etc.),
entertainment, energy savings, etc. lmplementation of any desired application
can
be accomplished with suitable programming and applying the invention as
described
herein.
[0030] In one preferred embodiment, the central controller is sized and
arranged
to fit inside of a standard household electrical box of the type that would
commonly
house a conventional light switch or outlet. A small central controller could
be fit into
a single switch box, while a two-gang, three-gang or larger box can
accommodate a
larger central controlier and a correspondingly larger display panel -further
described below. FIG. IA illustrates the front appearance of a light switch
replaced
by a central controller in accordance with an embodiment of the invention.
FIG. 1 B
is an exploded view showing in more detail how a central controller can be
deployed
in a standard electrical box. The household wiring (available in the box)
provides
power for the central controller, although it can be battery powered or have
battery
backup.
[0031] The front panel of the central controller, which is removable for
service and
generally covers the central controller, preferably includes a display screen,
which
preferably comprises a touch-sensitive area, at least in part, for user input
by
touching an icon or other textual or graphic indicia to make a selection or
adjustment.
[0032] The display / touch screen can be employed by suitable programming to
provide an effective graphical user interface. In a simple example, one screen
display (not shown) can be used to emulate a conventional light switch or
dimmer
control. This is a useful default value, say for a bedroom, where the user
commonly
enters the room and expects a light switch in the usual location inside the
door. A
central controller can replace the light switch in that box, and the default
screen
display can look like a light switch, and indeed function to turn the light
off and on,
responsive to a user press of the touch screen.
[0033] Referring again to FIG. 2A, it illustrates certain preferred features
of the
front panel. For example, the panel includes a few "hard" buttons -actual
physical
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buttons, that can be operated at any time without using the touch screen.
These are
labeied for illustration as "Application" and "Select". Continuing the bedroom
example, after the default display is used to turn on the light, the user may
press
"Application" to see a list or set of icons representing applications
currently available
to her at that central controller. She may select "Audio" by pressing the
corresponding icon, in which case the screen display changes again to present
the
audio player controls of FIG. 2A. By touching the screen where the pause,
play, etc
buttons are shown, the user can conveniently operate the audio system from the
central controller. This is accomplished by a wireless controller that is
inside or
coupled to the audio equipment to receive corresponding commands from the
central
controller.
[0034] Note the top of the screen display preferably shows the location of the
central controller, for example "Room Two" (FIG. 2A), "Living Room" (FIG. 2B),
"Kitchen" (FIG. 2C) etc. The display preferably also includes a screen number
where
a given function requires more than one screen display. For example, in the
living
room, the lighting control screens span a total of six screens, with screen
"2/6"
shown in FIG. 2B. These principles of graphical user interface can be applied
to
other applications as well. In general, the central controller can interact
with any
electrical apparatus or system within the local network. The tocal network
comprises
one or more central controllers together with one or more, preferably many,
controllers that communicate with the central controller and interact with
various
apparatus coupled to those controllers, such as audio, video, HVAC equipment,
lighting, etc.
[0035] Some of these features are illustrated in FIG. 3-a simplified network
diagram. In this example, a central controller impiements wireless
communications,
shown by dashed lines, with various components of the network. For example, a
wireless controller "A" is connected to a motorized damper for HVAC control.
It
adjusts the damper in response to commands from the central controller.
Another
wireless controller "B" is connected to a video camera for security
surveillance. The
controller can adjust the camera in response to commands from the central
controller, as well as communicate video data to the central controller.
Surveillance
software in the central controller may include, for exampie, image recognition
software for detecting an intruder outside the premises by analyzing the
captured
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video data. A wireless hub can be used to interface multiple appliances to a
central
controller where they are not coupled to it directly.
[0036] Wireless controllers may vary in their parkicular features and
characteristics as necessary. A simple, low cost controller, for example, can
be used
merely to switch a light or outlet on and off responsive to remote commands.
Simple
wireless modules for lights and household appliances are commercially
available
from intermatic Incorporated of Spring Grove, IL. See www.intermatic.com.
Other
wireless light modules including dimmers are available from Lutron and Zwave.
In
preferred embodiments, a central controller in accordance with the present
invention
executes application software and includes wireless transceivers that are
compatible
with these existing modules so as to include them in the new network. More
sophisticated controllers, called "intelligent controllers," are discussed
later with
regard to managing harmonics caused by non-linear loads.
[0037] FIG. 3 also illustrates a wireless controller "C" coupled to an
appliance
such as a stove. The central controller can check to ensure that the stove is
not left
on when no one is at home. Motion or thermal detectors, as part of the
network, can
be used to determine whether people are at home. The same sensors are
conveniently used for HVAC/ comfort control, automated lighting applications,
security, etc. In that regard, a door lock device is shown in FIG. 3 as well.
Here, the
wireless transceiver capability is integrated into the door lock device
itself; a
separate wireless controller is not required. This device can be used to
remotely
lock or unlock the door, but also to report its status, open, closed, locked,
to the
security application software executing on the central controller in some
embodiments of the invention. Various security algorithms can be used to
secure
the wireless communications in the network and prevent unauthorized intrusion.
[0038] FIG. 4 is a simplified hardware block diagram of one example of a
central
controller consistent with the present invention. Interconnections among the
various
components are omitted to avoid obscuring the drawing. Preferably, the CPU is
an
industry standard off-the-shelf microprocessor, along with internal and or
external
memory as appropriate, including both volatile and non-volatile memory such as
flash memory. Preferably the CPU is provided with at least one standard
embedded
operating system such as Windows CE , Linux Embedded, QnX or the like.
[0039] In the example illustrated, sensors are provided for sensing local
ambient
temperature, proximity (of a person), ambient light level, and so on. A
microphone
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enables voice command inputs (in cooperation with voice recognition software
stored
in the memory and executable on the CPU). A speaker enabies audible alarms,
warnings or other announcements. A service connection, for example a standard
connector such as an USB port can be provided for diagnostics, software
loading,
etc. Alternatively, the wireless transceiver can be used for communication
with a
computer or similar device for such functions. Other embodiments may have more
of fewer sensors, inputs or outputs. Additional details of various specific
embodiments of the invention will be within the design capabilities of persons
skilled
in eiectronics and microprocessor applications in view of the present
disclosure. A
alternative biprocessor architecture that incorporates the secondary processor
is
described later.
[0040] FIG. 5 is a simplified residential floor plan to illustrate selected
aspects of
HVAC control using the present invention. Here, each room iliustrated includes
a
motion or proximity sensor "M" and a temperature sensor'T". These may be
"standalone" remote sensor units, with the ability to communicate with a
centrai
controller. Or, one or more of them may itself be a local central controller
in that
room. Either way, comfort control software executing on the central controller
can
determine which rooms are occupied, as well as the current temperature of each
room. Based on that information, it can adjust each local room HVAC damper(s)
to
optimize comfort while minimizing energy consumption. The system can also be
used to control the HVAC system itself as part of this process.
[0041] To briefly summarize this section, the invention enables a user to
conveniently: control any wireless light switch in any room; control any
wireless
power outlet; control any other electrical appliance which can be controlled
via
wireless protocol (coffee makers, rice makers, floor lamps, pool/tub
electrical
systems, smoke detectors, electrical locks, garage openers, etc), i.e.
appliances that
have integrated or "built-in" wireless control capability; and access media
stored on
the wireless server or on any other media storage device connected directly or
indirectly by the wireiess protocol to other system components. Of course,
some
embodiments of the invention will implement fewer than all of these features;
they
are not all required by the invention. The key point is that the central
controller and
distributed network described herein can be used in myriad ways, without
significant
hardware changes or added expense, because this svs' am is fundamentally
application software driven.
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[0042] Additional functionality can include: monitor video from any video
camera
or other video signal source connected directiy or indirectly by the wireless
protocol
to other system components; access settings and control the HVAC system in the
household; have voice communication via the phone or inside the household
between two or more central controller's; operate electrical devices which
support
infrared remote controls via the device which is equipped with the wireless
controller
and infrared emitter; access, control, query any other electronic devices via
wireless
protocol or infrared sequences.
[0043] All the foregoing functions of the central controller can be accessed
with
the touch screen or by voice command, or automatically (under software
control) in
response to sensor inputs, time or other trigger conditions or a combination
of trigger
conditions. In a preferred embodiment, any particular setting or parameter of
the
system can be used as a part of a saved profiie. Any profile can be selected
by user
or automatically (according to schedule, day light, etc.).
[0044] The user interface of the central controller is designed to accommodate
people's habit of entering a room and switching the light on. To do so, the
user
interface in one embodiment implements the "default switch" virtual button.
This
graphic button is displayed as the default screen display on the cc after a
short time-
out period following the last active user input. Any combination of the
parameters or
settings can be controlled by the "default button". Thus, for example, where
each
bedroom has a central controller installed, the occupant need merely touch the
central controller panel once upon arrival to set lighting, audio, heat, etc.
as
determined by that user's personal profile. Profiles can be used in individual
spaces
and or network-wide. Some illustrative home-wide profiles are as follows:
[0045] Profile 1: No one home
Lighting: Lights off except, after dark, ON bathroom #1 and bedroom #3
and hall #2.
Security: Full ON after one minute for exit, check door locks, commence
video surveillance.
Comfort: Lower all living spaces to 62-degrees F.
Entertainment: Off
[0046] Profile 2: Home: Commencing at 4:00 pm on weekdays
Lighting: Lights ON after dark, OFF bathroom #1 and all bedrooms; ON
living room default settings
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Security: door and window chimes only, discontinue video surveillance.
Comfort: Raise all living spaces to 72-degrees F.
Entertainment: Audio enabied, download daily news feed.
[0047] Profile 3: Sunday morning; etc...._Profile 4: Sunday afternoons, etc.
[0048] Profile 5: short vacation, and so on. Profiles are created under
software
control and stored in non-volatile memory in the appropriate central
controller.
Asymmetrical biprocessor architecture
[0049] An asymmetrical biprocessor architecture is optional but preferred to
improve the reliability, availability and serviceability of home or commercial
automation systems such as those described above.
[0050] Modern home automation system contain hundreds electronic components
and hundred of thousands to millions lines of lines of software code. The
failure of a
single component (hardware and software) may render the system compietely
unusable which is unacceptable for home automation applications. There is a
need
for reliable, available and easily services and updated system.
[0051] There are two main contributing factors that can lead to failure in a
home
automation system:
1. Software errors. Bugs occurs because it's impracticable to provide
100% testing of large programs.
2. Main processor has a lot of dependencies on other electronic
components. Failure of any of these components as failure of CPU itself makes
the
whole system unworkable. Also, the typical system contains fragile components
(ike
a touch screen, so there is always a risk that this screen can be broken, and
even
when formally the system is alive, it becomes very difficult to use it.
[0052] We propose a new design for reliable home automation systems using two
different processors. As described above, a home automation system comprises
at
least one central controller. lt may used several of them. In many cases, all
of the
central controllers will be the same - to lower cost and simplify installation
of a
distributed network. We propose that a central controller comprise at least
two
different processors.
[0053] Referring now to FIG. 6, a simplified schematic diagram illustrates one
example of an asymmetric biprocessor architecture of a central controller in
accordance with one aspect of the invention. Here, a Processor A is a main
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controller which performs the full-scale functionality of the system,
optionaliy
including "nice-to-have" but non-essential features like speech recognition, a
graphical user interface, position sensors, etc. Preferably it is a relatively
fast
processor, which is connected to external memory (ROM and or RAM) as described
earlier. On the contrary, the Processor B is relatively siow embedded
microcontroller, with few dependencies on external components. It has three
main
functions:
1. Verify that the program in Processor A is alive and is performing
normally (watchdog functionality).
2. In the case of failure in Processor A, it switches the main controlling
circuits of periphery on itself and performing the basic functionality (e.g_,
turning the
lights/electrical loads on/off).
3. Log all system failures in a non-volatile memory joumal.
[0054] As shown in the figure, a switch controlled by Processor B is used to
take
over interaction with all peripheral devices and interfaces in the event that
Processor
B detects a failure of Processor A. Monitoring is implemented via the
communication
link shown. The software for Processor B preferably contains relatively few -
only
several hundred lines of code, so that the algorithms can be 100% tested.
Accordingly, the risk of a software bug in Processor B is much (by the
inventors'
estimate better than 100 times) lower.
[0055] Given that the number of dependent components is smaller in this
design,
the possibility of hardware failure is lower as well (it is proportional to
the number of
dependent components and pin count of the processor). This contrasts with a
simple "mirroring" or backup scheme in which a second processor, identicai to
Processor A, is deployed as a backup. That approach improves reliability, but
at
higher cost, and with inferior results.
Energy Savings Technigues
[0056] In this section we describe new methods and systems for saving energy
in
residential and commercial facilities, especially those where non-linear loads
create
harmonic distortions on the supply. In some embodiments, we seek to normalize
electrical loads associated with dimming light systems and other non-linear
electrical
loads. Such normalization reduces heat dissipation in distribution
transformers and
the harmonic distortion created by non-linear loads that are typical in most
residential
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and commercial electrical systems. In some embodiments, energy savings are
accomplished by leveraging a distributed home automation network.
[0057] Thus one aspect of the present invention enhances distributed wireless
automation systems by introducing system level components that reduce harmonic
distortion and heat that can cause energy inefficiencies and electrical
infrastructure
failures. The sources of these inefficiencies are lighting systems that
utilize dimming
controls, computer and pulse power supplies, televisions and other non-linear
loads.
[0058] One aspect of the invention is directed to reducing K-factor and
associated
energy losses by intelligent control of dimmed electrical loads by the
distributed
home automation network. The electrical load in a typical residential location
is non-
linear and consequently it generates harmonic currents -mainly odd harmonics
in
the case of single-phase nonlinear loads. These currents are usually
dissipated in
distribution transformers resulting in overheating and energy losses. The
harmonic
distortions are quantitatively described by a"K-Factor," defined as
K-Factor = S(lh)2h2
where lh is the load current at harmonic h, expressed in a per-unit basis such
that
the total RMS current equals one amp, i.e., S(lh)2 = 1.0
[0059] K-Factor is a weighing of the harmonic load currents according to their
effects on transformer hating, as derived from ANS!/IEEE C57.110. A K-Factor
of
1.0 indicates a linear load (no harmonics). The higher the K-Factor, the
greater the
harmonic heating effects. Figure 7A shows linear load when K-Factor = 1 and
thermal losses in the distribution transformer are low. FIG. 7B shows the
essentially
sinusoidal electrical current waveform through the load of FIG. 7A. However,
many
of the modern electronic loads increasingly found in residential and
commercial
buildings are nonlinear-dimmed light, computers, pulse power supplies, etc.
The
typical K-factor value for the office is usually from 4 to 9 which,
corresponds to the 15
- 20% increase in the heat losses.
[0060] FIG. 8A illustrates a plurality of non-linear loads, here conventional
light
dimmers, set to 1/3 brightness, in a single-phase power circuit. FIG. 8B shows
the
resulting non-linear electrical current waveform through the load of FIG. 8A.
This
waveform has substantial harmonic distortion, meaning that there is
substantial
current flow in the third and subsequent odd harmonics of the line fundamental
frequency (60 Hz.). As noted earlier, this scenario leads to thermal losses,
equipment wear, and voltage waveform degradation in the power supply system.
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[0061] In accordance with the present invention, improved power control is
implemented to remedy this situation, without sacrificing operational
functionality in
any noticeable way. Two schemes are presented; regulating individual non-
linear
loads so they work better together; and using the presence of a linear load to
normalize the overall system current flow.
[0062] First, we propose to use a distributed network of sensor and dimmers
(power regulators) to reduce harmonic distortions and associated heat losses.
Referring now to FIG. 9A, three dimmers are again shown as loads. Here, a
current
sensor labeled "A" is deployed in the circuit to measure the current waveform.
It
functions to measures the shape of the current waveform and transfer this
information to a central controller, using wired or wireless network
protocols.
[0063] The central controller, labeled "B" in FIG. 9A, analyses the harmonic
distortions and calculates a start phase for each of the dimmers to minimize
the total
harmonic currents. This is preferably implemented through the use of "smart
dimmers" which means a dimmer that can select start phase and optionally stop
phase of the power line cycle in response to a control signal or command. In
some
embodiments, the control signal is transmitted to the smart dimmers from the
central
controller via a wireless communication channel. It could also be hard-wired.
It
would also be equivalent to transmit the control signaling in the power line
itself, a
signaling technique that is well known for other uses. Preferably, the control
analysis
is carried out in software in the central controller, and most preferably it
is
implemented in an application software program loaded and executed in the
central
controlier.
[0064] FIG. 9B illustrates one solution in which each lobe of the power line
current waveform is divided into three segments, during each of which a
corresponding one of the lighting (or other) loads receives power. The overall
effect
is to minimize harmonics, i.e., the resulting current waveform for the system
is
substantially linear. This is accomplished by sending on-phase and off-phase
commands to the smart dimmers, for example assigning load B to be ON during 60-
120 degrees phase angle, and again at 240-300 degrees, etc. This aspect of the
invention improves the power line voltage quality, and saves electrical energy
previously dissipated in distribution transformers due to harmonic current
heating.
Moreover, the size/weight of the distribution transformer can be decreased due
to
lower heat dissipation; again saving costs.
13
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[0065] Second, we propose another solution to address non-linear loading
issues.
This second solution can be used together with the first solution, or as an
alternative.
It will typically require somewhat less hardware (fewer control components).
This
solution takes advantage of the ability to control a resistive (linear) load
in the same
network, and does so in a way that compensates for or "normalizes" the
harmonic
distortion that results from non-linear loading of the types described above.
A
residential electric water heater is a good example of a linear (resistive)
load.
Importantly, it will function with a non-linear supply.
[0066] FIG. 10 illustrates one embodiment of this second solution. Here, a
current sensor "A" is used, as before, to capture the electrical current
waveform in
the system. It sends the waveform data to a central controller "B", preferably
by a
wireless channel. In both the first and second solutions, the current sensor
(load
current waveform) data should be updated periodically. This update can be
scheduled, pushed, polled or any other convenient mechanism. Advantageously,
in
a home automation network context, the application software can be arranged to
update the current sensor data whenever a change in made to the lighting
settings,
either manually or programmatically as discussed elsewhere herein.
[0067] A linear load, in this example a water heater, is depioyed in the
circuit as
other loads, linear and non-linear. The water heater power is regulated by a
"smart
controller" or "intelligent controller" functionally similar to the "smart
dimmer"
described earlier, i.e., a controller that can select start phase and
optionally stop
phase of the power line cycle for powering an attached load in response to a
control
signal or command. A smart controller can handle larger loads typically than a
smart
dimmer. In some embodiments, the control signal is transmitted to the smart
controller from the central controller via a wireless communication channel.
The goal
is to regulate current through the linear load in a manner that normalizes the
non-
linear loads present.
[0068] FIG. 11 provides an example that illustrates this process in one
application. Here, the AC line (live) has two loads of interest - a color TV
(non-linear
load) and a water heater (resistive load). A current shape sensor detects the
total
current -as indicated in insert "T". The current waveform T exhibits
excursions from
the sinusoid (evidencing harmonics) caused by the non-linear TV load. The
current
shape is communicated to the central controller. It can be represented or
encoded in
various ways.
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[0069] An "intelligent controller" is deployed to regulate current to the
water
heater responsive to a control signal or command as described earfier. In this
example, the central controller, preferably in software, analyses the current
waveform "T" and determines a complementary or normalizing waveform - shown in
FIG. 12 - for regulating the resistive (water heater) load. The water heater
works as
well as before, but with this waveform, the overall system load in normalized
to that it
is substantially sinusoidal, i.e., it exhibits a minimum of harmonic
distortion. This
provides the same benefits as mentioned above. Details of the normalizing
communications and commands, e.g. coding, error protection, resolution, etc.
are
matters of design choice for a given application. Preferably, the invention is
embodied in systems that leverage industry standard wireless protocols,
microprocessor operating systems, API's and the like.
[0070] The inventors estimate that a typical residential system could enjoy
energy
economy up to 10% - 20% using the present inventions, and this savings is
independent of other energy savings methods.
[0071] It will be obvious to those having skill in the art that many changes
may be
made to the details of the above-described embodiments without departing from
the
underlying principles of the invention. The scope of the present invention
should,
therefore, be determined only by the following claims.
