Photovoltaic - Market & Product Gerenzano, November 2010 1 GEFRAN Drive & Motion
The Renewable Energies Introduction 2 GEFRAN Drive & Motion 2
The PV Technology 3 GEFRAN Drive & Motion November 2010
Working concept of a PV control system By the DRIVE it depends the By the DRIVE it depends the POWER CONVERSION from POWER CONVERSION from the PV PANELS to the MAINS the PV PANELS to the MAINS PHOTOVOLTAIC GENERATORS BETTER CONVERSION BETTER CONVERSION EFFICENCY with low LOSSES EFFICENCY with low LOSSES means HIGHER PROFITABILITY of the HIGHER PROFITABILITY of the PLANT INVESTMENT PLANT INVESTMENT DC Power The PV Inverter affects between the 5% and 10% on AC the whole value of the PV MAINS System 2 WAYS COUNTER AC Power 4 GEFRAN Drive & Motion
PV Plants – Main Components � SOLAR CELL : � PV Generator . The photovoltaic cells are mainly made of semiconductor material (silicon) forming a sheets (wafer), assembled in modules and then in panel . A series connection of these panels forms the string and a parallel of these ones the generator (PV field). When placed under the sun, on the generators surface a magnetic field is generated, and consequently a flowing of DC current PHOTOVOLTAIC GENERATOR CELL MODULE Many cells assembled in PANEL STRING PV GENERATOR a common Many modules Many panels Many strings PARALLEL structure assembled in SERIES connected to obtain the needed a common connected power (kw) structure The voltage of the PV system is The current of the PV system is equal to the sum of the voltage of the sum of the currents of the “n” the panels or modules present on strings parallel connected a single string 5 November 2010
PV Plants – Main Components � INVERTER � The PV Inverter is the device that converts the DC current into AC current. Is based on a AFE (Active Front End) technology, being the operation a traditional continuous recovering of energy towards the AC mains. The AFE technology is necessary also to produce a “clean energy” to be sento to the mains and then is mandatory a quite UNITARY COSFI and THD < 3%...5% DC AC POWER POWER 6 GEFRAN Drive & Motion November 2010
PV Plants – Main Components � COUNTER (Meter) � 1 or 2 WAYS Counter for all the grid-connected PV systems. 1 Way counter if there is only energy production 2 Ways counter if there is there is energy production but contemporary consumption by the users / producer. (eg domestic plants) 7 GEFRAN Drive & Motion November 2010
PV Plants – Main Components � PV String Box and String Main Switch: � The String Box , is a “hub” for the parallel connection of the strings. The electronic devices here implemented are used to detect the current of each string and eventual failures, allowing a continuous monitoring of the modules itself. The monitoring is normally carried out via RS485 Serial line communication, with the “data logger” and the inverter � The Main Switch of the string box is useful to section a single box for an eventual need of switch it off, allowing a disconnection of just a part of the PV plant 8 GEFRAN Drive & Motion November 2010
PV Plants – Main Components � DATA LOGGER � Remote diagnosis control system or “Data Logger” allows the remote monitoring through a web connection of each single part of the plants and contemporary the trend of the power generation and the consequent earn in term of money. The control of the plant is normally done on a dedicated web portal These devices are provided with a wide range of communication protocols such as Ethernet, GSM, ISDN, GPRS… 9 GEFRAN Drive & Motion November 2010
The PV System Configuration – Integration Level � Reminding the share of the PV plant type in 3 main categories and users: • Domestic & Small Commercial • Factory & Public • Utilities & PV Park: Fully integrated in the house architecture (Building Integrated o BIPV) , where the system is integrated in structure such as roof. The modules used in this way, reduce at minimum the sight impact also being more expensive respect to the module for other installation typologies. Mainly used for Domestic & Small Commercial application Average power plants: 1,5kW….6kW (3kW is the most common) 10 GEFRAN Drive & Motion November 2010
The PV System Configuration – Integration Level Partially integrated or semi-integrated , where the modules are placed on the roofs, coverage, fronts, balusters, railings of the buildings, in such a way that no parts of the building architecture has to be modified or removed Mainly used for Factory & Public application Average power plants: 10kW….100kW 11 GEFRAN Drive & Motion November 2010
The PV System Configuration – Integration Level Not integrated or ground mounted , where the system is installed on the ground such as electric centrals or also on the building roofs but with a particular placing, that allows also through sun- follower devices the best exploitation of the sunlight in any moment of the day. These plants are distinguishing for the highest productivity being engineered with advanced technological tools Mainly used for Utilities & PV Park application Average power plants: >100kW (also MW) 12 GEFRAN Drive & Motion November 2010
Systems type: comparison off grid vs grid-connected � According to the direct access to the mains, the plants are divided as: - OFF GRID : autonomous systems so called “island” because disconnected from the mains - GRID CONNECTED : systems connected to the mains (also called on-grid) OFF GRID In the systems off grid it is necessary the use of batteries (energy accumulator) to accumulate the electric energy and warranty the continuous delivery also in the period when the GRID-CONNECTED generator doesn’t produce energy (medium lifetime of the In the grid-connecetd types, the system include battery is 15 years) also a counter (so called “meter”) to measure the Othe important components are the “charge regulator” whose energy cosumption of the system itself intallation preserve the battery from peak load and avoid also the discharge of the battery. PV GENERATOR PV GENERATOR GEFRAN Drive & Motion 13 November 2010
The Inverter Technology 14 GEFRAN Drive & Motion November 2010
The main Inverter Duties The main duties of the inverter are the following 1.DC/AC Energy conversion 2.Clean power production through Unitary COSFI and THD < 3% 3.Synchronization of the output V & F with the one of the AC mains 4.Highest Efficiency of the system 15 GEFRAN Drive & Motion November 2010
The main Inverter Duties PV application: technological requirement for the inverter � Unitary Cosfi (Power Factor) the input current and voltage on the mains must be perfectly synchronized. This allows to avoid energy loss on the main and produce undesired noises. Mandatory. � THDi � 3% to limit the harmonic distortion, cause of overheating of components such as cables, transformers, capacitors and noises toward the AC main itself. The sinus waveform is perfect without any distortion � Efficiency value : whose level define the capability to produce the highest quantity of energy, meaning the highest productivity corresponding to the best “PROFIT” for the user . The efficiency of the inverter is the traditional value defined by the output losses of the power components due to their heating. The value is normally close to 97…98 % for the 1ph drive and around the 96% for the 3ph series with trafo and 98% trafoless *** � MPPT Maximum Power Point Traking . The power of the PV module is a value difficult to be kept constant, being the sun an intermittent source of energy. For this reason the inverter in a wide range of operative conditions, has to follow in each instant the point of maximum power (MPPT), that means a target point on the V-I characteristic curve of the PV generator, for which is resulting the maximum power transfer towards the load and the main. The MPPT is a specific control algorithm of the inverter for PV application 16 GEFRAN Drive & Motion November 2010
The main Inverter Typologies Inverter with internal transformer • The LV/LV transformer ensure the galvanic insulation with the AC mains • It is normally mandatory for powers higher than 20kW and up to 100kW • The LV/HV transformer in mandatory for powers over 100kW • Furthermore, the trafo rises the voltage level to a value suitable for the delivery to the AC mains. Note: for the single phase drive , the trafo is mandatory for powers > 6kw Advantages: • Safe and quality of the mains: best control of the current sent to the mains avoiding DC current components 460Vdc 400Vac 17 GEFRAN Drive & Motion November 2010
The main Inverter Typologies Inverter “trafoless” • Are normally used in multi-inverter plants, where the distribution to the mains is performed through a HV/HV transformer • The three pahse inverter are available in a power range from 20kW up to 250kW and also the single phase models have a line provided without trafo • The trafoless inverter are in this case equipped with specific devices against the DC components Advantages: • Higher level of efficiency (2% higehr) thanks to the reduction of the trafo losses • Lower cost of the inverter (better ROI for the user) • Lower weight of the inverter 460Vdc HV/HV Trafo 290Vac 18 GEFRAN Drive & Motion November 2010
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