VPT12 Phase Lock Loop
small hydro controllers
-An inexpensive electronic governor and control system for hydroelectric power plants using synchronous AC generators from half a kilowatt to 100 kilowatts.
"What is it?"
- A box you hang on the wall and connect to the power plant with a heavy cable. Needs a small amount of water for cooling. Small units can be located in the home if the power lines coming in are large enough. Larger ones should be located in the powerhouse.
- Has a water tank with a number of electric heating elements, and built-in electronics. In a simple installation, nothing else is needed to control the plant. More features can be added if desired.
"What does it do?"
- Controls the speed of the plant's generator very precisely and manages the day to day operation of the plant in other ways as well - details below.
"Why do I need one?"
- You don't. If you are willing to gaze at a frequency meter 10 times a day, switch on a kilowatt's worth of appliances for every kilowatt you turn off and buy lots of spare light bulbs you can get along without a controller just fine. And I definitely haven't met you yet. A controller keeps your power plant at the right speed and the right frequency, and helps to protect it and all your electrical appliances from damage.
"Without getting technical, what is a phase lock loop anyway?"
- It's a situation where the timing of something is kept in sync with the timing of something else. Phase just means how far along any repetitive process has gotten. The phases of the moon are a good example. In your powerhouse it means the angle the rotating machinery is passing through at any given moment, as it makes a complete revolution. The VPT12 controls this with a quartz crystal. That means the accuracy of the plant's speed is every bit as good as that of the quartz crystal at all times.
"What's so great about that?"
It gives speed accuracy that is every bit as good as the accuracy of the crystal. And in our units, the crystal can be digitally tuned for even better accuracy. If you find that after a long time your electric clock is gaining or losing time slightly, you can adjust the speed of the plant - and hence its frequency - in steps of 30 parts per million until the frequency is extremely accurate. In tests, it took only 10 seconds to adjust two of these controllers - not connected to each other in any way - so that one had not lost or gained on the other one by more than 1 second after ten days.
Features - in brief
- Highly accurate quartz phase lock loop speed control using heaters in a water tank.
- Turbine water control, co-ordinated with the above.
- Emergency shutdown - two types (requires water control on turbine).
- High-precision load management - 15 loads controlled over 1 pair of small wires.
- Management decoder in the home has plant status display lamps.
- 5 status lamps on the front of the main unit also.
- LCD display screen.
- Computer interface.
- Screwdriver adjustment for matching to heavy or light weight machinery.
- Automatically shuts off water tank if overheated, and uses turbine water control instead.
Ballast tanks can contain any number of heating elements, each with its own triac, with 4 being the normal minimum (3 if you have a good, well costructed generator with low internal resistance). Many of the tanks we have built have sides of 3/4 inch by 3 inch aluminum bar, top & bottom of 1/2 inch by 3 inch aluminum bar and front and back of 1/8 or 3/16 inch aluminum plate, all bolted together with blind holes (except for the heating element through-holes) and no welds.
Features - in detail
(Lots of detail - you might want to save this and read it offline)
- Locks the plant's AC power solidly in step with a quartz crystal so the speed of the plant is highly accurate. Clocks in the home, which often depend on this, will keep good time and the user's electronic equipment will run better and safer.
- Heaters in a water tank are used for this purpose. By varying the current fed to the heaters, the load on the plant, and hence its speed, is precisely controlled. Earlier technology used in small hydro controls would simply keep the plant's speed within a certain tolerance, - an electronic version of the magnificent old hydraulic governors found in 19th and early 20th century hydroelectric powerhouses, which sometime weighed more than a thousand pounds, had great quantities of gears, shafts, belts, pumps, valves and other complex mechanical apparatus and cost more than the rest of the machinery put together. And you had to deal with much grease and oil. Or rather the plant's on-staff maintenance engineer did.
- When electronic governors came along, size, weight, complexity and cost were dramatically reduced. Like the old hydraulic units, these controllers could tell quite accurately HOW OFTEN the generator was completing a revolution - but had no idea of WHEN that revolution was completed and no way of controlling that. So if these kinds of timing errors slowly built up, there was no way these controllers could fix it. Later, some controllers were given the ability to do what large power grids had been doing for years - they could count the number of AC cycles the plant had produced and if serious errors had built up, they could speed up the plant or slow it down a tiny amount for a few hours until the user's electric clocks again read the correct time.
- This controller takes things another step forward. Instead of simply adjusting plant load to correct speed errors, it controls the exact timing of every degree of rotation of the generator - more like an industrial-strength version of the technology that drives the tape-head wheel inside a VCR. Thus the plant's speed is not merely adjusted, it is solidly "locked on" at the precise value. If the generator's rotating parts arrive at a certain point a few milliseconds late, for example, This controller will slightly reduce load until the machinery "catches up" again. The speed of the generator, measured over one minute, one month or one year, is thus an exact function of the controller's quartz crystal timing system. The unit's timing is very slightly adjustable, so that if the user wants more accuracy than even the quartz time base can provide, it is a simple matter to achieve this. In tests, a Carson Electronics controller circuit board sitting on the bench was adjusted so that it matched the timing of the small hydro in use at the site, which also had one of these controllers running it. The unit on the bench then remained in step with the rotating generator in the powerhouse for over two hours although it was not equipped with any water heaters or means of control whatever. Interestingly, if this test is done at a site where a small hydro is controlled by another of these controllers, or a site connected to the public electrical grid, the "lock" light will come on and may stay lit for hours. At a site where another type of controller is in use, the "lock" light may not come on at all, or if it does, it may go out again in a few seconds due to the variations in the power.
- The controller never switches the heaters on or off when power is applied. Instead, it waits until the AC stops flowing, as all AC power does 120 times each second. This eliminates the risk of distorting the AC power or causing radio and TV interference.
- Able to control the water going to any turbine that's equipped for this. Normally uses water control to reduce power if more than about two thirds of the heating power in its tank is on. This way it is able to control plants with more power output than its water tank can absorb. These are often operated by a 12 volt car battery and a battery charger.
- Can reduce water to the turbine if the headpond level starts to drop. The software in the unit contains a user-settable reservoir time constant which will allow the turbine water control to maintain a constant reservoir level without surges, and use all the water in the stream if the penstock is big enough. Hardware for this function is currently being developed.
- The controller has a number of "failsafe" systems built into it including automatic re-start of its software if, for example, lightning strikes and temporarily scrambles the unit's on-board computer.
- If the water tank overheats, perhaps due to a plugged water filter or other loss of cooling water, the unit will sense this and begin using the turbine's water control as a speed control rather than a kilowatts control.
- If the electric power to the controller itself fails, the water control's 12 volt battery will power the controller and allow it to shut down the plant safely with the water control.
- If all else fails the unit issues an emergency shutdown command which can be picked up by the turbine's emergency shutdown system (usually involving some sort of falling weights attached to the water control arms) and stop the plant. This works even if all power to all the electronics in the controller is lost, the plant is dead and the battery is dead. Serious overspeed will also make the controller issue a shutdown command.
- Far more electrical loads such as baseboard heaters etc. can be connected to the plant than it will actually run all at once. The controller will then distribute the available electricity to as many things as possible without overloading the plant, and keep all the rest turned off. If more power is available later, it will allow other loads to come on. Note that it doesn't "force" any controlled load to be on - it only "allows" it to be used in whatever manner is usual in the home, such as by a thermostat on the wall. To avoid annoyance, electrical devices connected to this should be unobtrusive ones that don't cause problems if they switch off without warning. Electric baseboard heaters and water heaters are a good choice.
- The controlled loads are arranged in order of priority. What the user considers most important will come on first and go off last. For example, in a home, an electric water heater would probably be more important than any one of several baseboard heaters, because there's only one water heater and if it is not allowed to operate for several hours due to insufficient power available, taking a shower will soon be no fun at all. However a three second interruption due to someone pulling the trigger on a large power tool would never be noticed, and will certainly help the power tool to get started.
-To do load management, the controller sends signals over one pair of small copper wires to a decoder box in the home which can then control up to 15 loads in order of importance as decided by the user. The signal on the wires has a peak voltage of 12 volts and has enough power to run the electronics and light up all the status lamps on about 3 decoders as well as telling them what to display and what to switch on. If more decoders are to be placed on the same line or if the lines are very long, the decoders can be powered from the home's AC wiring instead.
- The load management decoder box has 20 LED lamps which show which loads are permitted and which are disallowed, along with two lamps that show movement of the turbine's water arm, one lamp that shows when the plant is locked on speed, and one lamp that starts flashing if the controller's water tank overheats.
- There are 5 LED lamps on the front panel of the controller.
-Three lamps show plant speed (low, ok and high). Nothing too complicated here. A yellow lamp for low, a green one for ok and a red one for high. You will only see the yellow one light up if the plant is overloaded or losing power I.E belts slipping, air in penstock etc). The red one will only light up if the ballast tank water supply or heaters fail or the total ballast load is too small for the plant.
- An orange LED lamp shows "phase". In other words, whether the generator, in its rotation, gets to the right place at the right time (this isn't quite the same as "speed". For example, In North America and Australia the seasons pass by at exactly the same rate (same "speed") but at different times. All the southern seasons are half a year "out of phase" with the northern ones. If a similar situation develops between the plant's AC power and the precision quartz-clocked AC inside the controller, the phase LED will go on, usually meaning someone's running something pretty big off the plant or the tank has overheated and been shut down. If a frequency error develops, one can look at the phase lamp to see how serious it is - the worse the error, the faster this lamp will flash - one flash per second means a one hertz error and so on.
- The final lamp, a blue one marked "lock", indicates that the controller, after careful testing, is confident that the water tank system is working and that the plant is truly under control, not just doing the right thing by chance. At this point the controller turns on the lock lamp and, if water control exists, it gives a considerable amount more water to the turbine, perhaps all of it. This will probably be more water than the user's present requirements demand. But thanks to the magic of the phase-lock-loop, the generator doesn't speed up as the water is increased. The excess electricity is diverted into the tank heaters, for instant transfer to the user when needed; meanwhile it is used to govern the plant, with just enough load being applied to keep the generator held to the correct speed and phase.
- If the plant gets thrown out of lock it's usually because somebody's using some large electrical device (a 200 horsepower electric motor perhaps?) or roughhousing the whole system in some other way. The lock light goes out. No problem - the plant will generally re-lock a couple of seconds later. However the lock light won't come back on just yet - as mentioned, careful testing is done first to confirm that the lock is real.
-If water control alone is being used and the heaters in the tank are disconnected or not there, the lock light will never come on.
- There is a screwdriver adjustment on the front of the unit, entitled "damping". This is used to set the controller to match the amount of mass or weight that the rotating parts of the plant have, so the unit can respond as efficiently as possible to everything the plant does and everything the people using it do to the plant. The adjustment is turned more clockwise for heavier plants or those with a flywheel attached, and counterclockwise for lightweight or very small plants that can respond faster. If the response is set too fast (too far counterclockwise), a point will be reached where the response gets "jittery" and the room lights may be seen to flicker slightly. If you must adjust this, it's sometimes nice to have a computer hooked up in case the flickering of the lights is not readily apparent - the computer display shows what the heaters in the tank are doing and you can see the jitter easily on that. Just back off a bit from the point where the jittery behavior starts, and the setting will be correct. Or try having the whole scene illuminated by a few small light bulbs, say 15 watts each. These bulbs will show up any flicker better than large bulbs. The human eye is most sensitive to flickering light at the edges of vision, so look away from the bulbs somewhat to see the flicker better.
- there is an on-off switch on the front panel. Caution: turning off the controller when it is operating the plant, especially when it is "locked", could cause overspeed to develop.
- If a water control has been included in the unit, there will be a toggle switch on the front of the tank, larger than the on-off switch, which allows the user to start up or shut down the plant by manually moving the turbine's water control arm. Push the switch down to reduce the water, or up to increase it. The center position on the switch puts the water control back in the capable hands of the controller. Or if the controller isn't switched on, the center position will simply leave the water control at its existing setting.
-There is a small LCD screen which explains what the controller is doing. Currently, it displays the following (may be different in future versions):
-When the unit is first powered up or is reset, the manufacturer's name and the serial number of the unit's internal software are displayed for three seconds. If you want to take your time reading the serial number, the message will remain indefinetely if you press the reset button about once every two seconds.
The screen might look loke this:
-During normal operation, the number of managed loads enabled and the amount of excess power still available are displayed, each figure being updated every three seconds. In addition, movement of the water control arm on the turbine is indicated by "<" or ">" at the lower right corner of the screen depending on which way it's moving. If the water control is not moving, nothing shows here. If the water control arm is against a limit switch, any motion commands will still be visible here but further motion toward the limit switch will of course not take place.
The screen might look like this:
-If the user puts a screwdriver in the damping adjustment hole (see above) and turns the adjustment, a number from 0 to 25 appears at lower right, showing the setting of the screwdriver adjustment. This number soon goes away when the user stops rotating the adjustment, and the water control display returns.
The screen might look like this:
- If the water tank overheats for any reason, the following is displayed until the user switches the controller off & on or presses the reset button:
- If the plant runs too fast, an overspeed warning is displayed until the plant manages to re-lock. If the overspeed was due to an overheat trip of the ballast tank, the overheat message will be displayed, not the overseed message.
The screen might look like this:
To implement load management in the home, you need a Carson Electronics LMD (load management decoder) that installs in the home in a normal 1-piece rectangular electrical outlet box. You also need to fit a solid state relay (provided by us or others) to each load to be controlled or a central bank of them in a large electric box (the decoder can go on the front of the same box), and you need to run a 1-pair telephone line to the powerhouse from the decoder in the home and from each solid state relay to the decoder, which will then control up to 15 managed loads in priority steps, as well as displaying what the controller is doing (water up, water down, locked/not locked, tank overheat warning and which of your managed loads are on or off anywhere on the system). Extra decoders can be connected to the 2-wire line for control in other buildings or locations or just to get a display of what's happening. These decoders can be powered by AC from the house wiring. Or, if there aren't too many of them, the incoming signal will power the decoders. For running signal-powered, there should be less than 4 decoders and the control wiring size should be increased from the normal 24 or 22 gauge if longer than 500 feet or if the LED's on the decoders look like they're flickering or dimming out.
- On the front panel of the decoder is a status lamp for each of the 15 controlled loads, plus lamps showing water up, water down, locked, and tank overheated. The only lamp which is a duplicate of one on the main controller is the lock lamp. The decoder's front panel has spaces marked out in which to write the name of each managed load.
- As many load management decoder boxes as desired may be connected to a single pair of signal wires coming from the main controller. They will all display the same thing. From the decoder, a pair of small wires must be run to each solid state switch for switching the managed loads off & on.
- On the main controller front panel is a small hole, behind which is a reset button. One use for this is to keep the sign-on message on the screen longer if you're having trouble reading it before it disappears. GENTLY press the button by poking a piece of wire or other object through the hole.
- The front panel of the main controller has a 9 pin socket where a line to a personal computer can be plugged in. The 9 pin socket is wired the same as the serial port on an AT computer.
Other kinds of computers can also be connected but at present there's only software available for the IBM type (XT or AT). Using a Mac, for example, you'd have to use a communications program and the things you would need to type in sometimes get rather technical.
- Only three conductor cable is required. No modems are needed to interface with a personal computer if the cable is less than 500 feet long - just plug into the computer's serial port. For long lines, surge protection devices can be supplied which help to protect both the controller and the personal computer from damage by lightning and other types of electrical surges.
- The PC software we provide is currently DOS-based. It's freeware. It runs well on anything from the most ancient XT or Tandy 1000 right up to a Pentium and can be used under DOS, Windows 3.1 or Windows 95 either full-screen or in a DOS window. It runs in the background very well and can continue to display plant operation while you're using another piece of Windows software. I often log onto the Web using Netscape while watching my hydro plant display at the same time. The software is tolerant of all sorts of bad communications and doesn't care about or require any hardware handshake signals - this is true at both the PC end and the controller end of the cable. You do not have to make any extra connections or loops at the serial port of the computer - only the ground, data in and data out lines are used, hence the ability to use only a 3-wire cable. The program will instantly recover, without human intervention, from any line problems up to and including somebody chopping the line in half with an axe and then splicing it back together again.
- The computer screen will display, in color or black and white depending on your monitor, what the plant is doing and provides some simple control and configuration functions. Many of the controller's LED lamps are simulated on the screen. You can type in labels to identify the "lamps" indicating each managed load - such as "Main House - Kitchen baseboard heater" etc. This list is stored on your hard drive and will come up with the program when you start it. Also available is the opportunity to specify the size in kilowatts of each managed load so the controller will know exactly when enough power is available to allow it to switch on. This list is stored in the controller itself so that it is available when no PC is connected. Or you can ask the controller to generate the list automatically by testing the power demands of each managed load in turn.
- A display of the current configuration of your controller can be displayed, along with the controller's sign-on message so you can check the serial number stored in the controller.
- By pressing the B (throttle Back) key, the plant's water control can be made to crank down to the point where no excess power is being absorbed and no managed loads are on - in this situation it is safe to briefly shut off the controller for maintenance, changing a water filter, etc. The controller can be put back in normal operation when ready, by pressing the U (throttle Up) key.
- By pressing the C key, you get the chance to configure the controller to match your own plant, fine tune the frequency, etc.
- The lower right corner of the screen has a display of all the binary data coming in from the controller. This is a sea of constantly changing ones and zeros we can happily ignore. The feature might disappear in future versions - it gives a technical person a detailed idea of what sort of a conversation the controller is having with the PC but isn't of much interest otherwise.
- Future versions of the personal computer software may be Windows-only (we'll still provide the DOS version for that creaky old twelve dollar computer in your powerouse) and will probably look like a video of the controller with its lights and LCD screen in operation, along with some other information at the bottom or around the edges, and will be viewed on your favourite Web Browser. Available functions will be more or less the same.
Normal configuration is: controller mounted in tank and ready to go. Just hang it on the wall, connect to generator through some kind of adequate switch, and run water through it.
Controls are an on-off toggle switch and, if water control is installed, a water up/down/auto toggle switch.
Minimum configuration is controller without ballast tank; this requires mounting one triac beside each heater on customer-supplied tank & wiring to unit. Or water control alone can be used, with no constant-load ballast. The latter system gives speed, not phase, control.
All controllers provide water control signals and load management signals at all times, so if these functions are installed later, the controller is ready to operate them.
The controller is entirely reprogrammable while in place in the powerhouse. If and when improvements are developed to the firmware that runs your plant for you, the unit can be upgraded without disconnecting a thing. And the hardware already exists inside the controller to implement all sorts of possible future add-ons such as monitoring bearing temperature, head level control, powerhouse security, belt slippage etc. etc. - almost every conceivable software feature we or our customers were able to dream up over the years is already provided for at the hardware level in this design. For simplicity though, many people may just want to hang a standard unit on the wall, hook up to the generator and the cooling water and leave their plant in its capable hands.
To implement water control you also need an electric or electric/hydraulic actuator and need to order, or specify that we provide, the correct switching circuit built into the controller or retrofitted to it. A battery and charger will be required to run this motor.
The Hydro Mania page also includes plans for a proven and inexpensive jackscrew-based linear actuator which is very reliable.
