PIC hydro system controller
Posted on Jun 2, 2012 8506
Under: PIC Microcontroller Circuits
The ELC presented here has some flexibility, thanks to being software-controlled, but also has its limitations: It's intended for microhydro systems that employ a single-phase synchronous alternator, working at 220-240V, 50Hz, in a power range up to 25 kilowatts, and using up to eight dump loads, some or all of which can be `useful` loads, such as water boilers or room heaters. It can be built for 120V systems too, simply by using the proper power transformer, but then it will be limited to half the power. It can also be configured for 60Hz (or any other reasonable frequency) simply by setting a parameter in the software. In the form presented here, four of the outputs are used in prioritized fashion, with the other four having all the same (last) priority, with power being distributed among them.
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This can be changed in the software too, allowing any combination from fully sequentially prioritized, to fully "democratic" among all outputs. This ELC uses a quartz crystal for reference, and in normal operation it locks the generator/turbine speed to this quartz, resulting in highly accurate frequency control. The software allows fine tuning of the frequency. However, if a heavy load change momentarily pulls the system out of lock, the resulting missing or surplus cycles will not be recovered; instead the system will try to recover the correct speed as quickly as possible. For this reason, in the presence of such transient loads it might not be stable enough to accurately run clocks that use the line frequency for reference, despite having quartz control. I have no line-frequency-dependent clock, so I haven't tested how accurate such a clock is with this ELC. The core of this ELC is a PIC microcontroller. I used a 16F628, which is one of the most common PICs, inexpensive, easy to get, and quite powerful and versatile. It also has just about the right number of pins for this application. The whole ELC consists of little more than this PIC, the power supply, and the power circuit built around eight TRIACs. The power transformer has two secondaries. One of them is used to power the circuit, by means of a totally conventional circuit using a bridge rectifier, filter capacitor, and three-terminal regulator. The other...