ZA200805913B

ZA200805913B - Wireless or can bus remote load shedding module

Info

Publication number: ZA200805913B
Application number: ZA200805913A
Authority: ZA
Inventors: Guilin Zheng
Original assignee: Guilin Zheng
Priority date: 2007-12-11
Filing date: 2008-07-07
Publication date: 2010-01-27
Also published as: CN201142577Y

Description

I . ) | | .-~ ‘Wireless or CAN bus remote load sheddinsmodud 0 8 / 0 5 9 1 3

Technology Field

This invention is a kind of programmable wireless remote load shedding module (for channels), which can be applied independently or integrated with remote meter reading systems. This module can be applied in prepaid power consumption management and remote peak-load management based on deliberately classification of the loads.

Background Technology

The household power load can be classified into indoor lighting, outdoor lighting, geysers, kitchen appliances and etc. It is possible for the power utilities to properly disconnect the corresponding classes of loads in peak season without serious negative influence on the inhabitants’ living styles. The loads are classified according to the significance of the load in different time for inhabitants’ living style. Such kind of peak-load management can decrease the demand pressure for power utilities without serous negative influence on the inhabitants’ living style. This is actually a kind of compromise between the decrease of power demand pressure for power utilities and the influence on inhabitants’ living. For example, in the peak-load period, it is proper to disconnect the household geysers. This module can be integrated into other products, such as monitoring and management software v2.0 for integrated meter reading system ST-PPH-GP, can realize a lot of kinds of demand side management models, for example, prepaid and credit grade management matching.

Summary of Invention

This invention provides a wireless remote load shedding module to manage remote classified loads. : The wireless programmable remote load shedding module including: at least one magnetic latching relay used as an actuator for load connection or disconnection, where at least one relay is used per load,

a 3 communication circuits and a corresponding external communication interface used to communicate with external wired or wireless long-distance equipment for transferring load shedding information, a microprocessor adapted for data acquisition and output control forming a hardware unit of the module, a relay status detection circuit to collect the running status of each relay (i.e. on or off), the circuit including zero-crossing detection and AC current prediction to determine the proper time for connection and disconnection of the load to minimise the switching current, multi-branch relay control circuits which are responsible for sending on or off commands, in the form of positive or negative pulses, to the corresponding magnetic latching relays, and a solid-state power resource module for supplying DC power to all the above modules.

All the modules may be connected to the corresponding interfaces of the microprocessor.

There may be four magnetic latching relays responsible for indoor lighting, outdoor lighting, geysers and kitchen appliances, respectively.

An E2ROM memory unit may be connected to the microprocessor, and the E2ROM memory unit is adapted to store configuration information and to receive programmable commands for the relays. :

The communication circuit may include: a CAN-bus communication circuit, which is responsible for communication with external equipment through a CAN-bus, the CAN-bus communication circuit including an extemal interface, which is responsible for staggered communication with other modules, or similar equipment, through the CAN-bus a RS232 communication circuit, which is responsible for communication with external equipment, the RS232 communication circuit

Vo 4 ® 2008705913 including an external interface of the RS232 circuit, which is responsible for external wireless communication.

Compared with existing technologies, this utility model has the following features:

A module can be connected by wire or wireless style with other modules or data acquisition devices to establish a network. Thus the local data can firstly be collected by free communication channel in the residential area, and then be transmitted to the monitoring center by GPRS or other communication networks, such that it is very convenient to establish remote control networks and integrated into the remote control into remote meter reading system.

Magnetic latching relays are employed for load control for they can be controlled simply by voltage pulses, which avoids providing electricity for ‘relays continuously. So the dissipation of relays’ coils will be reduced and the reliability will be improved.

Brief Description of the Drawings

The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings. In the drawings:

Figure 1 is a general schematic of a module in accordance with the : invention.

Figure 2 is a CAN-bus circuit schematic of a module in accordance with : the invention.

Figure 3 is a RS232 circuit schematic of a module in accordance with the invention.

Figure 4 is a MCU interface schematic of a module in accordance with the invention.

Figure 5 is a four-channel relay control circuit schematic of t a module in accordance with the invention.

Figure 6 is a relay status detection circuit schematic of a module in accordance with the invention.

Figure 7 is a circuit diagram of a module in accordance with the invention.

Figure 8 is a solid-state power supply circuit schematic of a module in accordance with the invention. :

Figure 9 is a system connection diagram of a module in accordance with the invention.

Figure 10 is the flow chart of a program in accordance with the invention.

Detailed Implementation

As shown in Figure 9, an ammeter (12) and a load shedding module (14) are installed in each residence. Indoor lighting, outdoor lighting, geysers, and kitchen appliances are respectively connected with the corresponding channel of the load shedding model (14). A data acquisition module (16) for a meter reading system is installed in each residence fo collect ammeter data. This data of different residences are gathered through wireless communication (18). The load shedding module (14) is connected with the data acquisition module by a CAN bus, and is embedded into the meter reading system. In this way, the monitoring center can read not only each user's ammeter data but also control different classes of consumers’ loads according to demand of decrease load pressure.

The main control circuits of the utility model are composed of sub-circuits shown in Figure 1 to Figure 8.

As shown in Figure 1, the microprocessor (10) is a new type of industrial controller, and it is the core part. It coordinates the operations of other circuits and sends ammeters’ information. The type of microprocessor isuPD78F0881, which has 32K bytes internal program memory and built-in }

CAN bus controller. The frequency of the clock is 4MHz, and the rate of CAN bus is up to 100Kbit/s. The following peripheral circuits can be included: clock circuit, CAN bus communication circuit (20), RS232 communication circuit (22), control output circuit, relay status detection circuit, and E2ROM memory bo 6

The clock circuit provides a digital square wave that can be viewed directly or used to drive other circuits, such as MCU and provides : precise software timing signal.

The E2ROM memory (24) stores identification address of the module, configuration information of network properties, and characteristic parameters of each relay. When the power supply is restored after power failure, the MCU will first reset with the data stored in memory to configure the module.

As shown in figure 2, staggered circuits communicate with external devices through CAN bus. The communication includes sending out the running information of module to and receiving control commands and messages from monitoring centre. CAN is ideally suited in applications requiring a high number of short messages in a short period of time with high reliability in rugged operating environments. The optical coupler 6N137 with high speed is employed as isolator for CAN, and the CAN {ransceiver is

TJA1040.

As shown in Figure 3, wireless communication circuits with + peripheral devices are RS232 interfaces. The RS232 communication chip is

SP3220 (26). A RS232 interface can conveniently be connected to currently popular wireless devices, such as digital radio and ZigBee module. With

RS232 interface employed, a wireless communication network can be established in residential areas, especially suitable for the areas where it is difficult to wire communication network cabling.

As shown in Figure 5, a control circuit for four channels of relays is isolated with microprocessor by TLP521-4 optical coupler. It can receive instructions from the microprocessor (10), and provides pulse voltage for operations of magnetic latching relays.

As shown in Figure 6, relay status detection circuit adopts a single channel optical coupler chip NEC2501 to detect the alternative voltage yo | 7 of each channel's output. The circuit collects the status of relays and estimates the zero-crossing point of the alternative current. With the mechanical switching time considered, the detection circuit makes the relay to be precisely switched on or off at the next zero-crossing point after it receives switching instructions. In this way, it is possible to avoid the occurrence of electric spark at the time of switching and the lifespan of the relays can be prolonged.

As shown in Figure 8, a solid-state module--WA3-220S12 is adopted for power supply, providing DC power for the whole system. Its input voltage widely ranges from AC85V to AC265V, and its output voltage is

DC12V. DC12V is provided directly for relay control circuits, and converted to

DC5V for other circuits by a DC/DC module B1205. CAN bus power is achieved step-down from DC12V by using of SPX1117. In this way, the relay control circuit, microprocessor (10) and communication chip can be completely isolated.

As shown in Figure 10, when the MCU (10) is powered it runs the initialization program first, then the status detection program of the four relays. The corresponding indicators will show the relays’ status. Then MCU (10) enters into a loop waiting program, which will be interrupted when MCU (10) receives the command from the monitoring centre by CAN bus. The MCU (10) will process the data from the monitoring centre and send out proper control commands. The same process happens when the MCU (10) receives the command from the monitoring centre by the RS232 interface (22). When : the interrupt program is finished, the MCU (10) will run the waiting loop program again.

Claims

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1. A wireless programmable remote load shedding module including: at least one magnetic latching relay used as an actuator for load \ connection or disconnection, where at least one relay is used per load, communication circuits and a corresponding external communication interface used to communicate with external wired or wireless long-distance equipment for transferring load shedding information, a microprocessor adapted for data acquisition and output control forming a hardware unit of the module, a relay status detection circuit to collect the running status of each relay

(i.e. on or off), the circuit including zero-crossing detection and AC current prediction to determine the proper time for connection and disconnection of the load to minimise the switching current, : multi-branch relay control circuits which are responsible for sending on or off commands, in the form of positive or negative pulses, to the corresponding magnetic latching relays, and a solid-state power resource module for supplying DC power to all the above modules.

2. A wireless module according to claim 1, wherein all the modules are connected to the corresponding interfaces of the microprocessor.

3. A wireless module according to claim 1, wherein there are four magnetic latching relays responsible for indoor lighting, outdoor lighting, : geysers and kitchen appliances, respectively.

4. A wireless module according to claim 1, wherein an E2ROM memory unit is connected to the microprocessor, and the E2ROM memory unit is adapted to store configuration information and to receive programmable commands for the relays.

P. 9

5. A wireless module according to claim 1, wherein the communication circuit includes: a CAN-bus communication circuit, which is responsible for communication with external equipment through a CAN-bus, the CAN-bus communication circuit including an external interface, which is responsible for staggered communication with other modules, or similar equipment, through the CAN-bus a RS232 communication circuit, which is responsible for communication with external equipment, the RS232 communication circuit including an external interface of the RS232 circuit, which is responsible for external wireless communication. Dated this 7" day of July 2008 Adams & Adams Applicants Patent Attorneys