Power Quality For The Digital Age INVERTING SOLAR POWER A N E N V IRONME N TA L P OT E N T I A L S W HI T E PA PER

Transcription

1 Power Quality For The Digital Age INVERTING SOLAR POWER A N E N V IRONME N TA L P OT E N T I A L S W HI T E PA PER

2 Introduction Heat in the System The modern facility has been revolutionized by advancements to electrical equipment. The fluctuation of oil and coal prices and concerns of global warming have significantly Most of the loads used in the modern facility are computer based loads such as PLC Reducing increased machines heat the demand and motors in the electrical for alternative controlled system energy. by VFD s. is critical Oil and These to sophisticated improving coal are diminishing power loads quality. resources require Wire which power is the to heart operate also contribute of the and electrical a communication significant distribution pollution channel system. to the to A control environment typical facility the load s with can have parameters. hazardous tens of CO2 thousands Traditionally, emission. of feet facilities of wire would throughout dedicate the two facility separate and lines, wire is one a major for power source and of one heat. for Heat communication. prematurely Alternative energy has focused on wind, geothermal and solar generation. While the degrades This increased wire quality the infrastructure causing both expenditure, energy losses the and maintenance burnout of the budget wire. and electrical availability of oil and coal will be exhausted, solar energy is an infinite source of energy The losses resistance in the system. in an electrical system is never constant. It depends on various factors such with no as harmful humidity, residues length such of wire as CO2. Power line communications technology and high allows frequency facilities noise. to use Wire low is the voltage main power conduit lines of electricity to transmit and data. is central This means to the facilities electrical do system. not need Resistance to run separate in the wire wire converts throughout a portion the Solar generation can have a positive impact on energy prices and global warming. As the of facility, electrical greatly energy reducing into heat. costs and significantly improving the production process. generation of solar power increases, some tough questions about the generation process Heat While in power the wire line communication decreases the efficiency technology of significantly the distribution reduced system. infrastructure It also creates costs a and fire hazard. need to electrical Contraction be answered. losses, the and Solar technology expansion power unlike is susceptible of wire other due power to to poor cooling is generated power and quality. heating in direct Noise of wire current generated loosens (DC). wire inside However, connections. the the facility electrical can This interfere makes distribution it or possible completely system for the requires disrupt electricity alternating communication to arc current and the data. (AC). heat This output means can reach 1800 degrees Fahrenheit. This is enough heat to ignite wood or insulation. solar power must be inverted from DC to AC before the power can be usable. However, Skin effect and proximity effect are the two major sources of heat in wire. inverting DC to AC creates noise and power pollution on the fundamental waveform. The Communication Highway Theoretically, since both data and power are transmitted at much different frequencies, both should be able to use the same wire without the signals interfering. The communication channel is comprised of data in the form of bits (binary digits); the sinusoidal waveform consists of sinusoids along the waveform. To understand this, imagine a two lane highway. Assume the lanes are designed based on auto speed. Cars drive 80mph on the left, while trucks drive 50mph on the right. As long as all cars and all trucks remain in the required lanes, there will not be collisions or congestion. However, if a truck moves to the left lane while maintaining its same speed of 50mph, it would cause congestion and/or collisions. In this example, left lane is the communication channel while the right lane is the power line channel. Cars are the data bits while the trucks are sinusoids. In order for this to function properly the frequencies on the power line and communication channel must remain at the intended frequency.

3 Solar Generation Solar Generation Solar power generation is adopting various new approaches, the most popular method is to use photovoltaic cells (PV Cells). PV cells are array shaped cells which are mounted Solar power generation is adopting various new approaches, the most popular method on solar panels. Photovoltaic cells consist of semiconductor materials which help in the is to use photovoltaic cells (PV Cells). PV cells are array shaped cells which are mounted generation of electrical charge. The solar cell with the help of its semiconductor nature on solar panels. Photovoltaic cells consist of semiconductor materials which help in the generation will convert of electrical the photon charge. energy The solar from cell the with sun the into help an of electron. its semiconductor Electrons nature created by this will process convert can the maintain photon energy an electrical from the charge sun into and can electron. easily Electrons flow through created a medium by this resulting process in electrical can maintain current. an electrical charge and can easily flow through a medium resulting in electrical current. The following picture demonstrates the photovoltaic effect. The following picture demonstrates the photovoltaic effect. Sunlight (photon) Sunlight (photon) PV cell PV cell Semiconductor Semiconductor material material Photon Photon Electron Flow Electron Flow

4 The current generated by this process is DC. The voltage of the solar power is small in magnitude, approximately 48VDC. However, the distribution system is designed for AC. Industrial and commercial loads require AC in order to function. This means the power generated by the solar cells is not useful for industrial applications. Solar generation facilities use inverters to convert this DC to a usable AC. These inverters convert the DC to AC directly after generation. Next, the AC is fed through the transformer, the voltage is stepped up and then transmitted through the transmission lines. From this point, the distribution of solar power behaves like any other method of power generation. The use of inverters is the key difference between solar power generation and other power generation. Other power sources generate AC, but in solar generation, DC power is generated and then inverted to AC and then transmitted. This conversion of power from DC to AC creates electrical problems in the facility, such as switching transients and high frequency noise. Switching transients and high frequency noise will result in an inefficient electrical distribution system. Noise Generation There are different types of inverters used in the process of inverting DC to AC, however, quasi state AC sine wave inverters are the most common. These inverters use power semiconductor technology to convert DC to AC. The types of power semiconductor devices used are Insulated Gate Bipolar Transistor (IGBT), Gate Turn Off Thyristor (GTO), and Emitter Turn Off Thyristor (ETO). In order to produce the required AC, the power semiconductor devices are turned on and off at a specific frequency. This turning on and off of the power semiconductor device requires extreme precision. Because of improper turning on and off of the gates, inverters are transient noise generators. Any change in the timing of frequency due to noise will result in surge or transient in the AC output voltage. This can damage equipment and decrease the efficiency of the electrical system.

5 Panel Mounting System There are two types of solar panel mounting systems: fixed system and tracking system. The fixed system is comprised of stationary solar panels. These panels are fixed to the mounting station and cannot move. This system is inefficient because the panels are not capable of tracking the movement of the sun. This means that the solar panels only receive the maximum amount of sunlight for a few hours while the rest of the day the panels receive only partial amounts of sunlight. In order to achieve maximum solar energy, the solar panel needs to track the sun movement and direct the PV cell towards the sunlight. This is also called active tracking. Motors are used to rotate the solar panel so that is tracks the sun. This tracking system is extremely sensitive and a minor change in the speed of the motor can significantly change the direction of the solar panel. This can decrease the efficiency of collecting solar energy and significantly reduce return on investment for solar generation. Changes in the speed of the motors are caused by disturbances on the power line, such as noise and switching transients. Figure 2: Active solar tracking system. Solar Solar panel Panel tracks trucks the the sun sun DC Motor Electrical Panel

6 Figure 2 demonstrates the movement of the solar panel with respect to change in the Figure 2 demonstrates the movement of the solar panel with respect to a change in the sun position. The motor used at the solar panel will tilt the panel s position according to position of the sun. The motor used at the solar panel will tilt the panel s position according the sun s position so that maximum sunlight is collected by the solar panel. to the sun s position so that maximum sunlight is collected by the solar panel. Figure 2 demonstrates the movement of the solar panel with respect change in the These tracking devices and solar panels are controlled and monitored by sophisticated sun position. The motor used at the solar panel will tilt the panel s position according to technology such as data acquisition systems and remote monitoring systems. Since the sun s position so that maximum sunlight is collected by the solar panel. these loads are sensitive, and recording or monitoring data requires high precision, high frequency These tracking noise devices must and be solar limited panels at are these controlled loads. and High monitored frequency by sophisticated noise will cause data technology such as data acquisition systems and remote monitoring systems. Since loss, miss programming of the computerized load, bit loss, improper encryption and these loads are sensitive, and recording or monitoring data requires high precision, high decryption, erratic behavior of devices. frequency noise must be limited at these loads. High frequency noise will cause data loss, miss programming of the computerized load, bit loss, improper encryption and Solar Storage decryption, erratic behavior of devices. Solar Solar energy Storage is intermittent, meaning all available output must be taken when available. This energy must be stored or transported over transmission lines. Batteries are used to Solar energy is intermittent, meaning all available output must be taken when available. store This energy the excess must be solar stored energy or transported so it can over be transmission used during lines. night Batteries or a are day used without to sufficient sunlight. store the excess solar energy so it can be used during night or a day without sufficient sunlight. Adding all these devices together, a solar power plant looks like the following. Adding all these devices together, a solar power plant looks like the following. Figure 3: Solar Generation Facility Figure 3: Solar Generation Facility DC Facility DC Facility Charge Controller AC Panel Charge Controller Batteries Inverter EP AC Panel DC Input DC AC Inverter Batteries EP DC Input DC AC

7 Power stations like hydral, coal and nuclear generate pure power free from electrical noise. However, due to the use of inverters, solar energy facilities generate polluted AC power. This pollution must be filtered before feeding this power to transmission lines, otherwise the electrical losses on on the the transmission lines lines will will increase. increase. The electrical The electrical noise noise will also will cause also malfunction cause malfunction of solar of panel solar active panel tracking active tracking system system and degrade and degrade the charging the charging capacity of capacity the batteries. of the batteries. The EP Solution High frequency noise on the fundamental waveform must be removed after the power is inverted from DC to AC. Environmental Potentials waveform correction technology is designed to filter high frequency noise from 1kHz to to 2MHz. EP EP waveform correction technology will absorb the the high high frequency frequency noise noise and and thermally thermally convert convert the noise the into noise heat. into This heat. ensures This ensures noise noise will not will residue not distribute out to to any any part part of of the the system including the the ground. Environmental Potentials will not only protect the inverter from external noise, but it it will will also protect the computerized programmable loads that control the solar panels. EP EP will will also increase the efficiency of the motor used for active tracking and therefore increases the solar energy generation. Conclusion Inverters and nonlinear devices are a crucial step in the process of generating solar power. Inverters are used to convert DC to AC. However, inverters use semiconductor devices which create switching transients in the electrical distribution system. The waveform generated by inverters is non-sinusoidal and contains high frequency noise. This results in an inefficient electrical distribution system, increased electrical losses and an increase of electrical maintenance in the system. High frequency noise on the signal can cause erratic behavior of programmable logical circuits used for the solar panels which will decrease the efficiency of the solar panels. The motor used to rotate the solar panels will also be affected by the noise on the fundamental waveform which can result in misalignment of solar panels. This will cause a reduction of solar energy generation. Correcting the sinusoidal nature of the waveform and removing high frequency noise will increase the efficiency of the generation process and ensure clean power is distributed to equipment. Environmental Potentials patented waveform correction technology eliminates noise, improves the sinusoidal nature of the waveform, and protects all sensitive electric equipment. This ensures the solar tracking system performs at its maximum capability and that the power generated is free from noise and transients.

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