A controller with a fluent regulation of power for a perfect utilization of PV surpluses
During recent years the owners of PV power plants have been thinking of how to use the surpluses of produced electricity and to get the highest possible income from operating the PV power plant. Based on the current prices of electricity surpluses, which in many cases are supplied to the grid free of charge, it is necessary to consume the largest amount of produced electricity by yourself. During daytime the PV power plant supplies fluctuating power. Almost all produced electricity is delivered during the time when owners are not at home. In this case it is ideal to install an automatic controller which ensures that the majority of generated electricity will be effectively utilized.
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To make the PV power plant automatic, it is essential to evaluate the current production and consumption of electricity, which is performed by measuring transformers connected to the inputs of the automatic controller. This is achieved by evaluating the consumption of electrical appliances which are switched on manually and are not operated by the controller. Based on this information the controller connects other appliances according to user’s priority to minimize any overflow of power into the grid. This system is designed to use the maximum of own produced electricity from PV power plant and also to save significant money for buying expensive electricity from existing electricity trader (which will certainly increase by a few percentage year-on-year).
The chart shows how to use all electricity from the PV power plant with a proper sizing and setting of GreenBonO
Pulse control in a range between 0% and 100% of the rated wattage of appliances
To be able to consume any excess of PV energy at any time, it is necessary to continuously adapt the current wattage of appliances to the size of surpluses. The GreenBonO regulator ensures a smooth control by managing a power thyristor device – SSR (Solid State Relay)..
The output signal of the PI regulator controls the switching density of individual sinusoidal periods by SSR. Therefore it controls a power of appliances connected to the SSR output in a full extent of their nominal values (0 – 100%).
Let’s suppose PV surpluses of 100W, the first appliance with rated input power 500W.
The controller output comes to stay when SSR switches every fifth period and the boiler takes off 20% of its rated output, i.e. 100W.
The second control signal ensures a gradual connection of appliances. Once the controller reaches a saturation in one of the two limits of its output, it is obvious that a continuous regulation occurs beyond a controllable range. Therefore after a specified period of continuous duration of this state (2 seconds) the number of connected appliances is automatically corrected; either another appliance which is in a row is added by switching on relays or one appliance is turned off by switching off the last closed relay. If after this process the saturation still occurs, the correction algorithm of appliances will repeat (it will connect or disconnect the next stage).
This simple algorithm is very efficient and ensures the correct control function without the device knowing the size of individual appliances. It responds correctly to any changes of electricity consumption using hotspots – whether appliances are connected randomly or for example a boiler is disconnected by a thermostat after warming up.
Continuously controlled versus uncontrolled (connected only) appliances
Pulse regulation is allowed for electrothermal appliances only. By no means try to connect a motor to a controlled branch (it can burn soon) or contactor coil or relay.
Please remember that e.g. a boiler can not use this function throughout the day because it can be heated up and disconnected by a thermostat. This situation can be resolved by switching (via a commutation) a pulse regulation to another appliance.
Single-phase and three-phase version
Depending on the number of measured phases a device (one and the same) supports three versions of utilization (with a different firmware):
There is a current transformer with a linear range of 0 – 12A built inside a device. This range of current measuring is sufficient for PV power plants about 5 kW; for greater power you can use an external measuring transformer with a higher current range. Single-phase version requires a sufficient number of single-phase appliances. The phase with PV power plant is measured and controlled. Other two phases are not measured, so their current is not taken into account in the regulation and is always purchased from the grid. Therefore, it is desirable in this version to transfer as many single-phase circuits of the offtake point to this measured phase as possible; otherwise the regulation has no effect.
Three-phase version (for old electricity meters only):
The device can also measure all three phases using three external measuring transformers connected to its analog inputs. In this case GreenBonO can control single-phase and three-phase appliences. Complete domestic energy consumption is taken into account using the three-phase measurement. In this version the performance of PV power plant may be substantially higher (hundreds of kW). The only condition is adequate peripherals sizing of GreenBonO controller: current measuring transformers and switching devices.
This version is designed for three-phase PV power plants only. It is for offtake points with electricity meter which (according to a new energy decree) evaluates (and charges) the flow of electricity through each phase separately. In such an offtake point there is a need to control the consumption of surpluses in each phase separately. Thus firmware of GreenBonO controller, designed for this version, is equipped with three independent PI controllers. Each PI controller independently manages the take-off in its phase (through its SSR). Also, for each of the five relay is set which PI controller regulates it and then has to switch the contactor of additional load supplied from the assigned phase. To control appliances in each phase separately it is necessary to use single-phase appliances or three-phase appliances connected into a star where the star node must be set to zero. Also, it is necessary to evenly divide the relay from the cascade to all three phases which significantly reduce the number of degrees of regulation. This results in a higher ratio between pulse controlled consumption and continuous consumption and therefore also more flicker (flashing bulbs). Therefore, the application of this version should only be used for small three-phase PV power plants. In areas where the performance of three-phase PV power plants exceeds 10 kW, three pieces of GreenBonO controller are required.
Owners of PV power plants who want to make the most of their produced energy
Owners of family houses
Operators of PV power plants who are not at home during the day and want to make the most of their produced energy
Everyone who does not want to give free energy to the grid and in the evening to buy electricity back
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TERMS Corp. was established in 1992 as a purely technological company which builds up on a high quality, knowledge, a long-term development and a stability.
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It does not finish at the electricity production
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The optimization and progressive integration and regulation of all energetic systems in your house can also be a part of our services.
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