Single chip microcomputer realizes intelligent electricity meter with time-sharing billing

introduction

The time-of-use smart meter is a novel single-chip intelligent energy metering product that adapts to the time-of-use electricity system. It not only retains the main functions of the original three-phase/single-phase meter , but also adds the function of calculating power consumption and electricity charges by time. This method can play a very important role in solving the problem of unbalanced power load and giving full play to the existing power generation capacity.

1. Structural principle of intelligent time-sharing electricity meter

This intelligent watt-hour meter maintains the current three-phase/single-phase watt-hour meter as the electricity measurement standard. It only punches a very small photoelectric detection hole on the dial, so that a pulse signal is given every time the dial rotates. After amplification and shaping, this pulse signal is used as the input signal of the external counting pulse of the microcontroller.

Generally speaking, the intelligent time-of-use electricity meter can be composed of two parts. The first part is the original three-phase/single-phase electricity meter, which can still be used as an electricity metering system alone. That is to say, every time the dial rotates one circle, it is driven by gears and the mechanical counter displays the electricity consumption. This original function remains unchanged; the second part is the newly added single-chip microcomputer system, which mainly inputs the signal of the number of circles of the dial in the form of counting pulses from T0, and then processes this signal appropriately according to the provisions of the time-based electricity billing system, so as to give the electricity consumption of the user in each billing period, and then directly calculate the user's electricity bill according to the time-of-use billing price standard. The design principle structure of the time-of-use intelligent electricity meter is shown in Figure 1.

2. Implementation of time-sharing billing

It is easy to record the electricity consumption using this smart meter. The technical difficulty lies in separating the electricity consumption according to different billing periods (high, medium and low peak periods) so as to multiply the different unit prices to calculate the total electricity bill for the user. The key to solving this problem is to have an absolute time standard.

This design uses a programmable timer as the time reference for the smart meter. The so-called "absolute time reference" means that even in the case of a power outage, the meter does not rotate, and no pulse signal is given, the timer must operate as usual. Otherwise, if the power is cut off for a few hours and the timer also stops working for a few hours, it may mistake the low peak period for the peak period..., thereby disrupting the entire time-of-use billing system. Since power outages occur frequently, practical time-of-use billing smart meters must have a backup power supply. During a power outage, the processing process of the smart meter is as follows: when a power outage signal is detected, the microcontroller can be interrupted through INT1, and the IDL bit of PCON is set in the interrupt service subroutine to put the microcontroller into an idle operation state, and the backup power supply is connected at the same time. Then the backup power supply is switched to the external timer so that the timer does not stop working. During the power outage, if the set timing time has arrived, that is, a certain billing period has arrived, the timer INT0 will send an interrupt request signal. Since INT0 is programmed as a high priority interrupt and INT1 is a low priority interrupt, the interrupt request of INT0 can still be responded to during the interrupt of INT1, so that the microcontroller ends the idle operation state and settles the electricity fee for a certain billing period in the interrupt service subroutine of INT0. Therefore, by using the idle operation state of the microcontroller, on the one hand, the consumption of backup power can be reduced during the power outage; on the other hand, the work of settling electricity fees can also proceed as usual without any impact. After the calculation is completed, the microcontroller can still return to the idle operation state and wait for the grid voltage to recover.

In order to distinguish the three different billing periods of high, medium and low peak, a shiftable flag can be set in the INT0 interrupt service subroutine. Each interruption shifts once, and three times constitutes a cycle, that is, after shifting three times, it returns to the initial value position. In this way, the position of the flag can be used to determine which billing period the system is in, and thus enter the corresponding electricity fee settlement subroutine. [page]

3 Main functions of the new smart electricity meter

The start and end time of the three different billing periods of high, medium and low peaks in a day and the unit price of electricity charges for each period can be entered by the power supply department through the keyboard when installing and activating the smart meter, and then sealed. During the operation of the smart meter, the meter should have the following main functions:

(1) The original three-phase/single-phase watt-hour meter can display the user's cumulative electricity consumption;

(2) Through the LED display of the single-chip system, the cumulative power consumption of each section, the total cumulative power consumption, the cumulative electricity charges of each section, and the total cumulative electricity charges can be displayed as needed;

(3) Various data can be printed as needed;

(4) You can check the electricity consumption and electricity charges during different time periods of the day;

(5) Equipped with backup power supply, which can switch automatically.

(6) The above data can be sent out from the serial port as needed, and then transmitted to the central control room of the power supply department through a wired/wireless data transmitter, so that the power supply department can keep abreast of the electricity consumption and electricity fee settlement of all relevant units at any time;

(7) After the power supply department collects the electricity fee on a monthly basis, the above amount can be cleared by pressing the reset button and the accumulation starts again;

(8) For units with electricity consumption limits, the power supply department can preset electricity consumption limits and provide over-limit alarm and double billing functions for the excess portion.

4 Conclusion

According to the time-sharing electricity billing system, this paper proposes a design method of a time-sharing billing intelligent watt-hour meter based on a single-chip microcomputer system and an absolute time standard. The implementation scheme of time-sharing billing in the system is analyzed in detail.