Automatic voltage regulation system of DC power supply screen silicon chain based on ATMAGE16 single chip microcomputer

At present, a large number of integrated automated substations in the power system have been newly built and renovated, which has enabled a large number of DC power panels to be applied in the power system. In order to make the system configuration reasonable, it can more reliably and stably increase the DC power supply for the substation and ensure the normal and reliable operation of the substation equipment. The working position of the voltage regulating unit that provides a stable DC voltage for the control bus is also extremely important. 

Voltage regulating unit: The voltage regulating method of silicon chain step-down is adopted. The voltage regulating capacity of the closing bus is configured according to the maximum discharge capacity of the closing load, and the voltage regulating capacity of the control bus is configured according to the maximum impact current of the control load. In order to make the system simple and easy to maintain, the closing bus is usually adopted without using the voltage regulating unit but directly the terminal voltage of the battery. At the same time, the silicon chain is required to have a manual/automatic voltage regulation conversion function, so that when the automatic voltage regulation function of the silicon chain fails, it can be converted to manual voltage regulation, which can also ensure the normal operation of the silicon chain and ensure the reliable power supply of the control bus. 

The DC power panel silicon chain automatic voltage regulating device based on the ATMAGE16 single-chip microcomputer combines the silicon chain, DC contactor, and voltage automatic detection device. The device automatically drives the contactor according to the control bus voltage, and adjusts the "on" and "off" of the silicon chain through the "open"/"close" of the contactor, changing the control bus voltage to keep it within the rated value range. The device can also operate in the manual voltage regulation state, forcibly closing or disconnecting the execution contactor, and adjusting the output voltage.

ATMAGE16 is a high-performance, low-power 8-bit AVR microprocessor that uses a RISC reduced instruction structure. Most instructions execute in a single machine cycle, and it works very easily on slow devices such as silicon chain automatic voltage regulation. It has 8 10-bit analog-to-digital converters, which is what we are concerned about, because automatic voltage regulation involves sampling of two DC voltages, and 8 10-bit ADs are sufficient, without the need for external AD chips. It has 32 programmable I./O ports, which are sufficient to dynamically display two three-digit DC voltages and human-machine interfaces. Its power consumption is very low. In the 1MHz operating mode, the operating current is only 1.1mA. The chip has a watchdog circuit inside to ensure that the program automatically returns to the normal program track in the event of a runaway. The following is a schematic diagram of the control system composed of the ATMAGE16 single-chip machine:

From the schematic diagram, we can see that the DC silicon chain voltage regulation system constructed with the ATMAGE16 single-chip machine has a very simple structure, without many auxiliary chips, and has very high reliability.

The silicon chain voltage regulation system is mainly composed of several major units such as working power supply, display system, AVR single chip microcomputer, DC voltage detection, and execution system. The display system consists of two three-digit common cathode digital tubes and ULN2003 as bit drivers. The segment selection of the digital tube is taken to the PB port of AVR. The two digital tubes display the battery voltage and the voltage on the control bus respectively. The AVR single chip microcomputer is the core of the whole system. The voltage on the battery and the control bus is sent to the PA0 and PA1 ports of the single chip microcomputer for AD conversion through resistor voltage division to obtain the actual voltage value. The two voltages are calculated and compared to obtain the level of the I/O port of the relay that should be driven. The execution system drives the relay according to the calculated I/O level to control the conduction and stop of the multiple diode combinations on the silicon chain, thereby realizing voltage changes on the silicon chain to ensure that the voltage on the control bus is basically constant.

The above is the main flow chart of the program. The key technology of system programming is to fully consider that the voltage regulation system is a slow system. The voltage regulation unit should not act too frequently. Therefore, sampling requires averaging to avoid interference. After sampling, it is necessary to delay for 10 seconds before sampling again. The change of the two values ​​is within a very small value to be considered valid. Otherwise, sampling is repeated until the correct value is sampled. This is to avoid the battery voltage fluctuation caused by the battery voltage loss caused by the short-term use of the battery on the closing busbar, which affects the control busbar. The calculated S value is the basis for the DC silicon chain voltage regulation. The S value must be judged by the Schmidt hysteresis curve, that is, the high-level change threshold and the low-level change threshold. The advantage of this is to avoid frequent action of the relay at a fixed point to affect the service life. The DC power supply panel is an important power supply equipment in the substation. Therefore, the operation of the step-down silicon chain program must be stable and reliable. A watchdog circuit must be added to the program loop. The program must be compiled strictly in accordance with the structured program to prevent the program from running away. In the event of failure of the automatic adjustment system, the system also has a manual adjustment part.

Conclusion

The DC power supply screen silicon chain automatic voltage regulation system based on ATMAGE16 single-chip microcomputer adopts advanced single-chip microcomputer technology to automatically adjust the voltage on the control bus. It has a series of advantages such as accurate voltage adjustment, rapid response, high reliability, simple circuit, convenient maintenance, and low cost. It is worthy of promotion and application.