ZA200905412B - Electricity supply monitoring and control methodology and device for peak and long term electricity demand control - Google Patents

Description

NE... J 7

ELECTRICITY SUPPLY MONITORING AND CONTROL METHODOLOGY

AND DEVICE FOR PEAK AND LONG TERM ELECTRICITY DEMAND

CONTROL

FIELD OF THE INVENTION

This invention relates to an electricity supply monitoring and load demand control device and the methodology to achieve such load monitoring and © control, whereby the electricity supply to a particular user or customer can be switched off should the user's electricity load (i.e. the amount of electricity being consumed) exceed a preset user-specific load or consumption limit. The same invention will all ow peak demand to be controlled on a dynamic basis, as well as longer term electricity demand, so as to achieve longer term savings on a sustainable basis. This is akin to an electricity rationing scheme, however, in this invention this capability is integrated with peak demand controls.

This preset allowable limit can be changed remotely via a wireless or other communications means, to allow an electricity supply utility to manage its total or regional load demand in accordance with its available electricity supply. Therefore, should the available electricity supply decrease, the local electricity supply utility can lower remotely the maximum load for each electricity consumer, resulting in electricity consumers exceeding the preset { limit being switched off to balance the load and leaving other consumers : with an electricity demand below their particular preset limits, unaffected.

The electricity supply utility can therefore balance its loads without having to resort to blanket or regional load shedding, which negatively affects critical electricity users, such as hospitals.

oo o B2009/054 12

BACKGROUND OF THE INVENTION

A need exists for electricity supply utilities to manage its load demand to required levels in order for peak demands not to exceed generation capacity, or for regional supply utilities not to exceed the capacity limits imposed on it by its own electricity supply utility. Such limits may vary from time to time in accordance with total demand and the prevailing supply capacity. Exceeding supply capacity or supply limits can result in emergency shutdowns, severe financial penalties, etc. Additionally, longer term sustainable electricity usage savings are required. Ideally one device and system should provide both capabilities, thus also allowing it to be used with off-line pre-paid meters, and other existing metering and controlling infra-structure.

The most often used methodology to control electricity consumption demand is to completely shut down the supply to specific areas, mainly by switching off substations, which is commonly referred to as load shedding.

This has a negative effect in that all consumers connected to the particular substation are then disconnected, including hospitals, schools, and traffic lights at intersections.

Another methodology is to remotely switch off non essential loads, such as geysers; however, the reduction in load as a result of such ripple control, is not enough in many cases, therefore resulting in regional load shedding. In addition, current ripple controliers do not allow the utility to unequivocally control load, since these ripple controllers do not measure the load and are generally unable to communicate with the utility.

Other electricity demand limiting interventions include time-of-use billing, : where charges will increase during times of high peak demand, and rationing, where a user will be provided a maximum amount of electricity to be consumed during, for example, a month.

The above interventions suffer from a number of disadvantages, the main

4 i 2 one being that all the users get grouped together, with no consideration being had for a specific user's actual electricity consumption, which can have unjust consequences.

OBJECTS OF THE INVENTION

This invention aims to provide an electricity supply monitoring and control methodology and device for both peak and long term electricity demand control, using remotely downloadable limits for peak usage, where such limits can be changed dynamically for immediate peak demand control, and where the longer term limits are used for long term, sustainable electricity savings over longer periods, such as over a day, week or over a month.

It is thus an aim of the present invention to provide the electricity supply utilities with a means to control and manage peak electricity demand, as well as long term electricity usage on a predictable and reliable basis, without having to rely on unpredictable ripple control of geysers, or without having to employ regional load shedding. : A further aim of the present invention is to provide the utilities with a means to sense actual loading from electricity users on an instantaneous basis, thereby allowing the utility to manage those users who are using excessive electricity by switching their electricity supplies off for a duration that will cause the average electricity loading not to exceed required limits.

Yet a further aim is to allow the utilities to control remotely peak demand, and for allowing the utility to unequivocally set, again remotely, a maximum peak load. :

A further aim is to provide the electricity user with a display, showing actual electricity being consumed and the maximum allowed load, so as to promote and encourage voluntary electricity saving.

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Ci . - B2009/056 12

A further aim of the invention is to provide the electricity user with an audible alarm to indicate that the user is exceeding the maximum allowed load, thereby providing the electricity user with a warning to disconnect loads until the electricity limit is no longer exceeded. Additionally, a further aim is to provide the electricity user with the option to receive cellphone

SMS messages and warnings related to actual usage and limits for both peak demand control, and for electricity rationing.

A further aim is therefore to reduce remotely peak electricity demand to the available supply levels on a dynamic basis.

Yet a further aim is to allow the utilities to set remotely a maximum total amount of electricity which can be used over a preset period, such as for a day, or a week, or a month, this to be displayed to the electricity user, and with the electricity supply being switched off automatically at the user's premises side, once this total amount of electricity is exceeded during the specific period.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an electricity supply monitoring and control device comprising: a microprocessor with an associated program memory; non volatile storage memory for storing data, the data including a user-specific electricity consumption limit; means to read the amount of electricity being consumed by at least one circuit monitored by the monitoring and control device, the at least one circuit comprising a main load circuit; a communications component to allow the device to communicate

© B2009/054 12 with a management and control system via a data transmission network, the communications component being arranged to receive the user-specific electricity consumption limit and transmit the amount of electricity being consumed by the at least one circuit, the user-specific electricity consumption limit being set by the management and control system depending upon the available electricity capacity and allowed peak demands and the actual total consumption by all the connected electricity consumers; and an integrated relay based circuit switch connected to the microprocessor, the microprocessor being arranged to switch on and off the main load circuit if the user-specific electricity consumption limit is being exceeded by the user.

In an example embodiment, the communications component can receive a revised user-specific electricity consumption limit from the management and control system, which can be adjusted by the management and control system depending upon data being received by the management and control system from a plurality of monitoring and control devices and/or a plurality of grid connected electricity energy meters.

In an example embodiment, the device includes a user display means connected to the microprocessor to display the user-specific electricity consumption limit and/or the electricity being consumed by the user.

In an example embodiment, the monitoring and control device has a unique identifying code, allowing the monitoring and control device to be uniquely identified.

In an example embodiment, a circuit switch is provided to completely switch off the load when the pre-set limit is exceeded.

In an example embodiment, a tamper sensing circuit is provided, which will detect when the device is opened or moved, and which will then transmit an alarm message to the management and control system for further action.

In an example embodiment, the device communicates with the management and control system wirelessly, with the management and control system being arranged to transmit the revised user-specific electricity consumption limit in kilowatt-hours. The management and control system can also extract electricity consumption data remotely, with the management and control system thus being able to provide commands to the monitoring and control device to remotely enable or disable the monitoring and control device, and to set the user-specific electricity consumption limit. This limit value can be stored in the non volatile storage memory of the device, and can be overwritten or changed when necessary.

In a further embodiment, the monitoring and control device is monitored and controlled via a GSM cellular modem, with the electricity consumption being able to be picked up from the monitoring and control device, and the user-specific electricity consumption limit being downloaded remotely via the GSM cellular modem.

According to a second aspect of the invention there is provided an electricity supply monitoring system comprising: a management and control system; and an electricity supply monitoring and control device comprising: a microprocessor with an associated program memory; non volatile storage memory for storing data, the data including a user-specific electricity consumption limit; means to read the amount of electricity being consumed by at least one circuit monitored by the monitoring and control device, the at least one circuit comprising a main load circuit;

Ts £2009/054 12 a communications component to allow the device to ) communicate with a management and control system via a data transmission network, the communications component being arranged to receive the user-specific electricity consumption limit and transmit the amount of electricity being consumed by the at least one circuit, the user-specific electricity consumption limit being set by the management and control system depending upon the available electricity capacity and allowed peak demands and the actual total consumption by all the connected electricity consumers; and an integrated relay based circuit switch connected to the microprocessor, the microprocessor being arranged to switch on and off the main load circuit if the user-specific electricity consumption limit is being exceeded by the user, whether this be the short term maximum peak demand, or the total electricity consumed over a longer preset period of time, such as on a daily, weekly or monthly basis.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawing 1 shows a basic circuit diagram of an electricity supply monitoring and control device according to an example embodiment of the present invention, the circuit comprising a main processor, a display, a GSM communications module, and an integrated watt-hour measurement controller;

Drawing 2 shows a basic circuit diagram of the connections to connect the monitoring device shown in Drawing 1 to a mains power supply, comprising a current transformer, a circuit switching relay, and a step down mains transformer; and

Drawing 3 shows a high level schematic diagram of an electricity supply oo N 2009705412 monitoring system to control total load using preset limits, the system comprising an electricity supply monitoring and control device, which may be of the type illustrated in - Drawings 1 and 2, and a management and control system that is in communication with the monitoring and control device.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring first to Drawing 1, and according to an example embodiment, a microchip PIC18F6628 microprocessor (U3) is used to control the operation of the supply monitoring device shown in Drawing 1. This processor may have an internal 96 kbytes flash memory for storing an operating program.

Additionally, the processor contains a 3936 byte static random access memory (RAM) used to store constants, stacks, and other dynamically changeable data. Semi-permanent paramaters, such as GSM number strings, a user-specific electricity consumption limit, SIM PIN and calibration data may be stored in the internal serial electrically changeable memory (EEPROM) of 1024 bytes. This processor has a large number of general purpose input/output pins (GPIO pins), allowing it to drive the circuit switching relays (RL1 to RL4 in Drawing 2) via the relay coil buffers.

The processor (U3) of the example embodiment also contains an internal

UART used to interface to the GSM GPRS modem (M1) via the serial transmit data (TXD) and receive data (RXD) signals. The processor (U3) operates with a 8 MHz crystal (X1) and a 5 volt DC power supply. The processor's 1°C serial peripheral bus is used to drive the user display (LCD1). The processor (U3) controls the circuit switching relays via 4 output ports, being PAO to PA3. When these ports are at logic level 1, the corresponding relay (RL1 to RL4 in Drawing 2) is activated via a driver transistor (only one of which is shown in Drawing 2, namely Q1), thereby "activating the relevant relay.

The user display (LCD1) may comprise a 16 character by 2 line liquid oo 2009/7054 12 crystal display with a serial 1°C interface, such as the LCD162-12 from

Digital Orbital. The software transmits a display address to the LCD module, this indicates the position of displayable characters transmitted to the display (LCD1), and will allow a character to be displayed at any of the top and bottom lines of 8 characters per line. The LCD incorporates a character generator, able to display fundamentally the ASCII character set in accordance with the standard 7 bit data being presented to the character generator. The character data is then transmitted to the LCD, with the character corresponding to the data then being displayed at the specific address. The data being displayed will be the averaged instantaneous electricity consumption in kilowatt-hours. Additionally, the display may also show the user-specific electricity consumption limit, also in kilowatt-hours.

Turning back to Drawing 1, a CS5460 single phase watt-hour limiting unit controller (U2) from Cirrus Logic may be used to determine energy consumption in watt-hours. This controller (U2) has 2 main high resolution analog to digital converters, these being used to determine the RMS value of the mains voltage, as well as the instantaneous current consumption presented by the particular load. By using the instantaneous voltage and current, the CS5460 calculates the RMS voltage, the RMS current, and the instantaneous power. Power is derived by multiplying RMS current and voltage at a rate of 4000 calculations per second. Thus, the instantaneous electrical energy being consumed is measured via an electronic circuit, which determines the mains voltage, the current of the load, and then accumulates this over time to derive the instantaneous energy consumed on a kilowatt-hour basis.

The CS5460 is a CMOS monolithic power measurement integrated circuit with an integrated energy computation engine. The CS5460 performs measurements of instantaneous current, instantaneous voltage, instantaneous power, energy, RMS current, and RMS voltage. The se measurements are output as 24-bit signed values. Instantaneous calculations are performed at a 4000 Hz rate whereas current RMS, voltage

RMS, and energy in watt-seconds are performed at a 1 Hz rate.

. The CS5460 contains both a serial SDI compliant interface port, as well as energy to pulse rate conversion interface pins. These are not used in this embodiment, only the serial SDI interface is used to set up the S5460 device, and to read the energy once every second. The CS5460 contains a number of internal configuration registers, which are largely set up at start- up. These set up the clock dividers, enabling the digital filters. The gain adjustments are made in order to compensate for gain in the current transformer, mains RMS input voltage changes, etc. The resistor based voltage divider of R11 and R68, as well as the similar network of R12 and R7 reduces the AC input voltage to the VIN+ and VIN- input pins to safe levels below 250 mV RMS. Resistors R13 and R9 reduce the already low I_In current sensing voltage by a factor of 16.6. This will reduce a current transformer maximum output voltage of 3.3 Volts RMS for a mains current loading of 30 Amperes to less than 250 mV RMS at the I_IN+ pin of the

CS5460 device.

A current transformer (CT1), as shown in Drawing 2, is used to derive an isolated, low voltage signal which is fully proportional to the current being consumed by the monitoring device. © The current transformer, type

CSE187-L, has a primary winding in series with the live mains conductor to the monitoring device. The secondary winding provides an isolated RMS - low voltage output proportional to the RMS current being consumed by the load attached to the monitoring device at 110 mVolts per Ampere sensed on the mains side, and can sense up to 30 Ampere on the mains side. This provides the instantaneous load voltage. The low voltage signal is converted to a digital value by a high resolution analog to digital converter, integrated in the CS5460. The output of this analog to digital converter is digitally filtered to provide a noise free digital representation of the instantaneous current. This single ended voltage, being I_RMS, is connected to IN+ of the CS5460, which is the current input. The negative input of this differential signal is grounded. The voltage inputs (VIN+ and

VIN-) pins come from the secondary of a 12 volt, centre tapped transformer (T2). Power is fundamentally derived in the CS5460 by multiplying the sensed RMS voltage and current. After suitable calibration, this provides the instantaneous power representation, in watts. This becomes energy when accumulated over time, such as over an hour to represent watt-hours, or kilowatt-hours for higher consumption.

The secondary output voltage from the same transformer may further connected to the anode of 2 diodes, these being used to generate the DC supply voltage for the monitoring device. A 7805 linear voltage regulator (REG1) provides the 5V DC regulated supply for the monitoring device circuitry.

Referring back to Drawing 1, and now also to Drawing 3, communications to a management and control system is via the use of a GSM modem module, M1, being a Telit GT864 quad band GSM modem. The trigger signal is an output from the PIC processor (U3) to the GSM modem to switch the modem on and off. The GSM modem will remain switched on : for most of the time to allow it to receive control messages. Alternative communications means to the management and control system may be accomplished by using the industry standard WiMax wireless communications means, using, for example, standard infrastructure from

Cisco. Many local governments and municipalities are considering implementing WiMax to provide connectivity infra-structure to residents in its region. The monitoring device will then be able to utilize this infrastructure. An alternative will be to use medium to long range mesh based wireless communications, which may be dedicated to monitoring device reading. In this case, a TinyOneLite RF 433 MHz module from One : RF Technology, embedded with their Mesh Protocol stack may be used.

Each monitoring device will be fitted with this module in place of the GSM modem (M1). The typical transmission distance will be up to 5 km line of sight, however, the mesh protocol will substantially extend this range by allowing messages to hop through modems in order to reach the management and control system, even though it may be situated more than km away from the monitoring device.

A software routine will firstly set up the watt-hour controller with values written to its gain registers, these values specific to the particular monitoring device to derive an accurate watt-hour reading. This is required due to tolerances in components, including the current transformer and the voltage transformer. A number of different calibration techniques exist and may be used. A simple calibration technique used is to first calibrate accurately the instantaneous power measured in watts, by using 4 different known and accurate high wattage resistive loads, including using resistor banks, and changing the gain register values to reflect the correct load for the particular RMS mains voltage being applied. For example, resistors providing loads of 25 W, 250 W, 2.5 kW, and 5 kW at 220 V RMS will provide a range of loads for calibration purposes. Variations from 220 V

AC RMS must be factored into the reading, using the simple formula of W=i x V, and W=MainsVoltage?/ load resistance. For example, using a resistive load of 22 ohms, the load will be 2200 W at 220 Volts RMS. At 210 V RMS the load will be 2004 W. A laboratory quality accurate AC volt monitoring device must be used to measure the AC RMS voltage during the calibration process, this will facilitate accurate calibration.

In operation the software will read the energy consumed every second from the CS5460, this will then be accumulated to provide the amount of watts used per minute. The processor contains an internal timer, which will interrupt the processor every second, this in turn will allow software routines to accumulate registers every minute and every hour. The kilowatt-hours consumed will be displayed to the user, and will be compared to the maximum allowed limit stored in EEPROM. This limit is also displayed, allowing the electricity user to monitor consumption against the limit. Should the limit be exceeded, a warning message will be displayed, optionally accompanied by an audible alarm as well. A time limit of 5 minutes will be typically provided to disconnect loads in order to reduce consumption to below the preset limit. Should the consumption still be above the limit, the relay switch will either switch off, and will remain off for a period, typically being 30 minutes, after which it will switch on again, or the electricity to the user will be disconnected for a period according to the :

amount of electricity that was used so as to balance the electricity load to the limits imposed by the utility. The consumption can be read remotely via the GSM modem on command.

For longer term electricity rationing, the total electricity consumed will be accumulated over the specific period, which could be a day, week or , month. This accumulated usage will be displayed, along with the maximum allowed electricity. As soon as the total consumption approaches the specific period maximum, the alarm will sound, which in turn will be followed by the disconnection of the electricity for the specific remainder of the period. An additional feature will be that the electricity supply monitoring and control device will transmit a data message to the management and control system indicating the imminent disconnection of the electricity supply to the particular user who is exceeding the downloaded limit. This will then result in an optional GSM SMS message to the electricity user warning the user of the imminent switch off.

Furthermore, additional early warning messages of excessive electricity usage can be sent to the users.

The management and control system may communicate with a monitoring device by first calling a particular monitoring device via a GSM data call.

Upon answering, the monitoring device will send the following data to the management and control system: unique monitoring device identification number, typically being a 10 digit number, the kilowatt-hour limit, and will then read the current consumption as reported by the monitoring device.

Once the monitoring device has acquired this limiting data, it will store it, - and then continuously compare it against the electricity being consumed. If the limit is exceeded, the relay will switch the load off for a period of time typically being at least 30 minutes, after which it will switch on again, with the testing against the pre-set limit commencing again.

In an alternative embodiment, a calculation may be used to balance the load to the limit, as follows:- :

Limit = a in kWhours

Actual usage = b in kWhours

Excess ratio = ¢ = Limit/Actual usage

Time switched on in an hour is = Excess ratio * 60 in minutes

For example, if a limit is 5000 kWhours, and actual usage is 7500 kWhours, then the particular load will be switched off for 20 minutes per hour to achieve an average of 5000 kWhours. This will be calculated and set by the control system via a downloaded command defining the switch off period, or locally by the electricity supply monitoring and control device. In yet another embodiment, the management and control system will determine centrally what the load limits are, based on the required load limits, the current load as determined by either grid meters, or by reading the load from each electricity usage monitoring and control device, and determining from this what the new load limit for each consumer should be.

This may be simply in the form of a blanket percentage reduction in load, or may be a specific load. Once determined, the load limits are communicated to the electricity usage monitoring and control devices via the GSM network.

This invention thus provides an alternative methodology to be used, which will not result in complete shut down of regions, but will still, however, provide the utility with a methodology to achieve its peak as well as longer term load and usage limits. In order to accomplish this load management functionality, an intelligent, self contained electricity load sensing and control switch is provided, which will disconnect loads connected to a mains alternating current power supply should the load exceed a preset or downloaded maximum allowed demand consumption load, either in the very short term for peak demand controls, or over a longer term, such as over a daily, weekly or monthly period, in order to achieve ongoing sustainable savings, without having to resort to blanket load shedding over large areas.

Claims (13)

wo CLAIMS

1. An electricity supply monitoring and control device comprising: a microprocessor and associated program memory; non-volatile storage memory for storing data, the data including a user-specific electricity consumption limit; means to read the amount of electricity being consumed by at least one circuit being monitored, the at least one circuit : comprising a main load circuit; a communications component to allow the device to communicate with a management and control system via a data transmission network, the communications component being arranged to receive the user-specific electricity consumption limit and transmit the amount of electricity being consumed by the at least one circuit, the user-specific electricity consumption limit being set by the management and control system depending upon the available electricity capacity and allowed peak demands and the actual total consumption by all the connected electricity consumers; and an integrated relay based circuit switch connected to the microprocessor, the microprocessor being arranged to switch on and off the main load circuit if the user-specific electricity consumption limit is exceeded by the user.

2. The device of claim 1, wherein the communications component can receive a revised user-specific electricity consumption limit from the management and control system, which can be adjusted by the management and control system depending upon data being received by the management and control system from a plurality of monitoring and control devices and/or a plurality of grid connected electricity energy meters.

3. The device of either claim 1 or claim 2, wherein the device includes a user display means connected to the microprocessor to display the user-specific electricity consumption limit and/or the electricity being consumed by the user.

4, The device of any one of the preceding claims, wherein the monitoring and control device has a unique identifying code, allowing the monitoring and control device to be uniquely identified.

5. The device of any one of the preceding claims, wherein a circuit switch is provided to switch off the load when the user-specific electricity consumption limit is exceeded.

6. The device of any one of the preceding claims, wherein a tamper sensing circuit is provided, which will detect when the device is opened or moved, and which will then transmit an alarm message to the management and control system for further action.

7. The device of any one of the preceding claims, wherein the device communicates with the management and control system wirelessly, with the management and control system being arranged to transmit the revised user-specific electricity consumption limit in kilowatt- hours.

8. The device of claim 7, wherein the management and control system can extract electricity consumption data remotely, with the management and control system thus being able to provide commands to the monitoring and control device to remotely enable or disable the monitoring and control device, and to set the user- specific electricity consumption limit.

9. The device of claim 8, wherein the user-specific electricity consumption limit can be stored in the non volatile storage memory of the device, and can be overwritten or changed when necessary.

10. The device of any one of the preceding claims, wherein the monitoring and control device is monitored and controlled via a GSM cellular modem, with the electricity consumption being able to be picked up from the monitoring and control device, and the user- specific electricity consumption limit being downloaded remotely via the GSM cellular modem.

11. An electricity supply monitoring system comprising: a management and control system; and an electricity supply monitoring and control device comprising: a microprocessor with an associated program memory; non volatile storage memory for storing data, the data including a user-specific electricity consumption limit; means to read the amount of electricity being consumed by at least one circuit monitored by the monitoring and control device, the at least one circuit comprising a main load circuit; a communications component to allow the device to communicate with a management and control system via a data transmission network, the communications component being arranged to receive the user- specific electricity consumption limit and transmit the amount of electricity being consumed by the at least one circuit, the user-specific electricity consumption limit being set by the management and control system depending upon the available electricity capacity and allowed peak demands and the actual total consumption by all the connected electricity consumers; and an integrated relay based circuit switch connected to the microprocessor, the microprocessor being arranged to switch on and off the main load circuit if the user-specific electricity consumption limit is being exceeded by the user, whether this be the short term maximum peak demand, or the total electricity consumed over a longer preset period of time, such as on a daily, weekly or monthly basis.

12. An electricity supply monitoring and control device substantially as herein described and illustrated.

13. An electricity supply monitoring system substantially as herein described and illustrated. DATED THIS 37° DAY OF AUGUST 2009 BOWMAN GILFILLAN INC. (JOHN & KERNICK) FOR THE APPLICANT