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PV grid-connected inverter works

DC inverter into alternating current, if the DC voltage is low, the AC transformer step through that get the standard AC voltage and frequency. Large-capacity inverter, due to a higher DC bus voltage, the AC output is generally not required that can achieve step-up 96v to 220v power inverter transformer 220V, in the small-capacity inverter, due to low DC voltage, such as 12V, 24V, it must be designed to boost circuit. Medium and small-capacity inverters generally have a push-pull inverter circuit, full-bridge inverter circuit and high frequency boost inverter circuit are three push-pull circuit, the step-up transformer neutral plug connected to the positive supply, two power tubes alternatively, the output AC power is obtained, since the ground side of the power transistor connected to the drive control circuit is simple and, in addition to the transformer has a leakage inductance to limit the short circuit current, thereby increasing the reliability of the circuit. The disadvantage is that the use of low transformers, inductive load driving ability is poor. Full-bridge inverter circuit to overcome the shortcomings of the push-pull circuit, the pulse width of the power transistor to regulate the output, i.e., the output AC voltage RMS change. Since the circuit has continued flow loop, even for inductive load, the output voltage waveform is not distorted. The disadvantage of this circuit is that the upper and lower arm of the power transistor is not common ground, solar power inverter and therefore must be used exclusively drive circuit or the use of isolated power. In addition, to prevent the upper and lower arm joint conduction occurs, must be designed to be shut off conduction circuit, which must be set dead time, the circuit structure is more complex.

Principles and Applications of inverters in photovoltaic systems

1 . Requires a high efficiency. Due to the current high prices of solar cells , in order to maximize the use of solar cells, improve system efficiency, we must seek to improve the efficiency of the inverter . 2 . Requires a high reliability. Currently photovoltaic systems are mainly used in remote areas, many power plants unattended and maintenance , which requires an inverter circuit with a reasonable structure, strict screening of components and require 2500w charge inverter an inverter with a variety of protection features such as input DC reverse polarity protection , AC output short circuit protection , thermal overload protection and so on. 3 . DC input voltage is required to adapt to a wide range, the terminal voltage of the solar cell and the intensity of sunlight varies with load changes , although the battery voltage of the solar cell has an important role, but because the battery voltage with the remaining battery capacity and internal resistance change fluctuate , particularly when the aging of the battery terminal voltage range is large, such as 12V battery , the terminal voltage may vary between 10V ~ 16V, which requires a larger inverter must be within the range of the DC input voltage guaranteed to work , and to ensure that the AC output voltage stability . 4 . In the medium and large -capacity 12 volt power inverters photovoltaic system , inverter power output should be less distortion sine wave . This is due in large capacity systems, the use of a square wave power supply , the output will contain more harmonics , high harmonics will generate additional losses , load a lot of photovoltaic systems for communications or instrumentation, these equipment on the grid have higher quality requirements, among the large-capacity photovoltaic power generation system and network operation , in order to avoid contamination of public electricity grid, also called a sine wave inverter output current. DC inverter into alternating current, if the DC voltage is low, the AC transformer step through that get the standard AC voltage and frequency. Large -capacity inverter, due to a higher DC bus voltage, the AC output is generally not required that can achieve step-up transformer 220V, in the small -capacity inverter, due to low DC voltage, such as 12V, 24V, it must be designed to boost circuit. Medium and small -capacity inverters generally have a push-pull inverter circuit, full-bridge inverter circuit and high frequency boost inverter circuit are three push-pull circuit , the step-up transformer neutral plug connected to the positive supply , two power tubes alternatively , the output AC power is obtained , since the ground side of the power transistor connected to the drive control circuit is simple and , in addition to the transformer has a leakage inductance to limit the short circuit current, thereby increasing the reliability of the circuit . The disadvantage is that the use of low transformers, inductive load driving ability is poor . Pure sine wave power inverter Full-bridge inverter circuit to overcome the shortcomings of the push-pull circuit , the pulse width of the power transistor to regulate the output , i.e., the output AC voltage RMS change. Since the circuit has continued flow loop , even for inductive load , the output voltage waveform is not distorted . The disadvantage of this circuit is that the upper and lower arm of the power transistor is not common ground , and therefore must be used exclusively drive circuit or the use of isolated power .

Solar PV inverters connected to the grid layout and safety issues

Today's solar inverter layout needs based on current sensor compact , low-cost and reliable ground current detection scheme . LEM whereby specially designed CT series sensors. 300 watt power inverter They are rated in the range of 100mA, 200mA and 400mA different current devices provide linear output 5 volts at rated current . At 80 % and 90 % of the rated current conditions , the response time of less than 20 milliseconds and 60 milliseconds. Using high-tech design ( " flux gate " ) is the key to accurately measure small dc or ac current especially under conditions of low offset or drift ; measure DC and AC currents up to 18 kHz . CT can be mounted on a PCB, the small size, light weight, there is a through hole for passing through the phase line . Mounted on the PCB CAS / CASR / CKSR closed-loop current sensor with the same flux gate technology ; can be isolated AC and DC current measurement , they cover the range of 6 to 50Arms rated , the highest rating of three times the value of the measurement , same frequency up to 300 kHz (+ /-3dB). According to the latest requirements of the inverter design trends they were specifically designed to improve the performance 24 volt power inverters of the following areas: common mode interference , temperature drift ( offset and gain ; Depending on the model , the maximum zero temperature drift of 7 to 30ppm / K), the response time ( less than 0.3 sec ) , the insulation level of the +5 volt supply and compact size .

Wide range of uses How to Protect

Power inverter applies not only to vehicle systems , as long as there is DC12V power of the occasion, can use the power inverter will convert DC12V AC220V AC, bring convenience to your life . 5 high and low voltage alarm and shutdown role is reflected in how ? High and low voltage power inverter when the alarm on and off the red LED lights , 4000 watt power inverters and an alarm sounds . Protection Power inverter when the battery using the battery , the battery voltage drops to 9.5V, the power inverter will automatically shut down to ensure that the car can be started normally , the battery will not be damaged. Power inverter is an electronic circuit by internal settings, battery protection function automatically . 8 What is the most prone to failure ? How do I exclude ? When using a power inverter , shutdown and alarm if the phenomenon , check the following: 1 ) driven by electrical power exceeds the value of the rated power of the inverter . 2 ) power inverter and battery and electrical connections are good . 3 ) Use the process down , whether the Pure sine wave power inverter temperature alarm , then a period of inactivity can continue to use . Note that the use of battery power inverter power system voltage value, and read the instructions before using the fine .

The basic principle of a system

The inverter power input for the battery (+12 V, capacity 90A · h), frequency output is a square wave voltage (50Hz, 310V). The block diagram shown in Figure 1 . Currently , new technologies constitute DC / AC inverter lot, but taking into account the specific conditions of use and cost, and reliability of the power supply still uses typical secondary 800 watt power inverter transformation, ie DC / DC converter and a DC / AC inverter . First, the DC / DC converter to the inverter DC12V high frequency square wave voltage by boosting the high-frequency step-up transformer , and then rectified and filtered to obtain a stable DC voltage of about 320V ; then the DC / AC inverter for converting a square wave mode , will become a stable DC voltage rms slightly larger than the inverse square-wave voltage of 220V ; then obtained by LC filter frequency of 50Hz is 220V AC voltage to drive the load.

2 DC / DC conversion Because of relatively low voltage side of the transformer primary , the transformer in order to improve the utilization of lower cost , DC / DC conversion shown in Figure 2 , push-pull circuit , the primary center tap connected to the battery , Pure sine wave power inverter with the ends of the switch control , alternate work can improve the conversion efficiency. The push-pull circuit with fewer switching devices , double-ended working volume of the transformer is relatively small , the duty cycle can be increased , increasing the output power ....

Principle Power Inverter

Using a thyristor circuit to convert the direct current alternating current, this corresponds to a reverse process of the rectifier, the inverter defined. For example: Application 6000 watt power inverters thyristor electric locomotives, so that when the downhill braking DC motor as a generator to run the locomotive's potential energy into electrical energy, trans go to the AC grid. Another example is the operation of a DC motor, to make it quick braking, the electric motor as a generator also allows operation of the motor kinetic energy into electrical energy, anti-delivered to the grid. The inverse DC into AC inverter circuit circuit called. In certain cases, the same set of thyristor rectifier circuit not only for, but also as an inverter. Converter in the inverter state, if the inverter AC side connected to AC power, the inverter converts DC to AC power with a frequency counter to go, called active inverter. If the change is not the AC side current grid connection, but directly to the load, which is a frequency inverter converts DC or AC adjustable frequency supplied to the load, then called passive inverter. AC frequency converter uses this principle to work. Except for the active inverter inverter 2000 watt DC reversible speed control system, but also for the exchange of spare lines rotor induction motor cascade control and other aspects of HVDC.

Inverter Precautions

1 , the DC voltage to be consistent Access to each inverter has a DC voltage value , such as 12V, 24V , etc., and asked to choose the battery voltage must be consistent with the DC input voltage of the inverter . For example , 12V 12V battery inverter must choose . 2 , the inverter output power must be greater than the use of electrical power , especially when starting power 1500w with charger inverter for large appliances such as refrigerators, air conditioners , but also leave bigger margin. 3, the positive and negative must be connected correctly Access to the inverter DC voltage labeled positive and negative . Red is positive ( + ) , black is negative ( - ) , also marked on the battery positive and negative , red is positive ( + ) , black is negative ( - ) must be connected to the connection being positive ( red pick red ) and negative to the negative ( black to black ) . Cable diameter must be rough enough, and to minimize the length of the cable . 4 , should be placed in ventilated, Pure sine wave power inverter dry place to guard against rain , and with the surrounding objects distance of more than 20cm away easily Burning explosive materials , or cover other items should not be placed on the machine , the ambient temperature of not more than 40 ℃. 5 , the charging can not be performed simultaneously with the inverter . That is not the inverter of the inverter output of the charging plug into an electrical circuit. 6 , the two switched intervals of not less than 5 seconds ( off the input power ) . 7 , with a dry cloth or anti-static cloth to keep the machine clean. 8 , the input and output connections of the machine before , first shell properly grounded machine. 9 , in order to avoid accidents, non- user to open the case to operate and use. 10 suspected faulty machine , please do not continue to operate and use , should be promptly cut off the solar inverters input and output , by qualified service personnel or maintenance units for inspection. 11 , when connecting the battery , make sure your hands are no other metal objects to avoid short-circuit the battery , the body burns .

Principle Power Inverter

Using a thyristor circuit to convert the direct current alternating current, this corresponds to a reverse process of the rectifier, the inverter defined. For example: Application 3000w charge function inverter thyristor electric locomotives, so that when the downhill braking DC motor as a generator to run the locomotive's potential energy into electrical energy, trans go to the AC grid. Another example is the operation of a DC motor, to make it quick braking, the electric motor as a generator also allows operation of the motor kinetic energy into electrical energy, anti-delivered to the grid. The inverse DC into AC inverter circuit circuit called. In certain cases, the same set of thyristor rectifier circuit not only for, but also as an inverter. Converter in the inverter state, if the inverter AC side connected to AC power, the inverter converts DC to AC power with a frequency counter to go, called active inverter. If the change is not the AC side current grid connection, but directly to the load, which is a frequency inverter converts DC or AC adjustable frequency supplied to the load, then called passive inverter. AC frequency converter uses this principle to work. Except for the active inverter DC reversible electric power inverter speed control system, but also for the exchange of spare lines rotor induction motor cascade control and other aspects of HVDC.

Principle Power Inverter

The DC circuit is called reverse into AC inverter circuit. In certain cases, the same set of thyristor rectifier 3000w charge function inverter circuit not only for, but also as an inverter. Converter in the inverter state, if the converter is connected to an AC power source AC side, the direct current to alternating current with a frequency inverter to the grid to counter, called active inverter. If the change is not the AC side current grid connection, but directly to the load, which is a frequency inverter converts DC or AC adjustable frequency supplied to the load, then called passive inverter. AC variable speed is the use of this principle works. Except for the active inverter DC reversible speed control system, solar power inverter but also for the exchange of Rao line rotor induction motor cascade control and other aspects of HVDC.

Car Inverter brief

Car inverter (power converters, Power Inverter) is a way to convert the DC power DC12V and AC220V AC mains the cnbou sine wave inverters same, for general electrical use, is a convenient vehicle power converters. Car power inverter in foreign markets was generally welcomed. Abroad due to the higher prevalence of motor vehicles, work or travel to a battery driven electrical connector and a variety of tools to work with inverters. After China entered the WTO, the domestic market, more and more private transport, therefore, as a DC car power inverter for use on the move to AC converter, will bring a lot of convenience to your life, is a standing Automotive vehicle loaded with supplies. By car cigarette lighter output inverter can be 20W, 40W, 80W, 120W 150W power until the specification. Then a large number of power inverter to be received via cable on the battery. The appliances connected to the output of the power converter can be used in a variety of appliances like the car as easy to use at home. Appliances that can be used are: cell phones, laptop computers, digital cameras, inverter bypass switch cameras, lighting, electric shavers, CD players, game consoles, handheld computers, power tools, car refrigerator and a variety of travel, camping, emergency medical treatment>

Automotive Power

Car power inverter power called , is a way to convert the DC power DC12V and AC220V AC mains the same , for general electrical use , is a convenient power converters , 3000w charge inverter as commonly used in the automotive named. General use car power car battery or cigarette lighter power supply , the first such low-voltage direct current is converted to DC 265V or so ; then is the real transformation stage , it will transform high voltage DC to AC 220V, 50Hz for . With the car power , you can put all the family moved to the car using small appliances such as mobile phones , laptop computers, digital cameras , car refrigerators, cameras , DVD , etc., thus making the car there is a feeling of home away from home . Since its launch , many limitations of using those appliances in the car will no longer exist , people can really enjoy , " and family -friendly, connected with the world " feeling . Car power not only apply to vehicle systems , as long as there are occasions DC12V DC power supply , power inverter can be used , will convert DC12V AC220V AC, bring convenience to people's lives . Car power fully take into account the external environment , when an overload or short circuit protection will be automatically shut down. The output voltage of the power supply through the feedback confirmed the car itself can make the voltage stability, voltage variation is less than the rated load and 10V. It should be noted that the purpose of the car power supply output and the same mains voltage Pure sine wave power inverter to meet the needs of appliances , automotive power actually output is an analog sine wave and the sine wave of the mains is true , the two slightly different , generally do not affect the use, it is the working principle of automotive power decision .

Knowledge of the power inverter

Definitions Power inverter ( car power ) is a way to convert the DC power DC12V and AC220V AC mains the same , for general electrical use , is a convenient power converters. ?Market conditions Power Inverter in foreign markets was generally welcomed. Abroad due to the higher prevalence of motor vehicles , there is no occasion when they go out in the mains work or travel to connect car battery with an inverter , electrical appliances best power inverter and power tools driven by what works to promote After China's entry into WTO, more and more private buyers in the domestic market , therefore , as a DC power inverter for use in the car on the move to AC power converter will bring convenience to your life , but also the essential car owners supplies. Wide range of uses Power inverter applies not only to vehicle systems , as long as there is DC12V power of the occasion, can use the power inverter will convert DC12V AC220V AC, bring convenience to your life . 5 high and low voltage alarm and shutdown role is reflected in how ? High and low voltage power inverter when the alarm on and off the red LED lights , and an alarm sounds . Protection Power inverter when the battery using the battery , the battery voltage drops to 9.5V, the power inverter will automatically shut down to ensure that the car can be started normally , the battery will not be damaged. How to Protect Power inverter is an electronic circuit by internal settings, battery protection function automatically . 8 What is the most prone to failure ? How do I exclude ? When using a power inverter , shutdown and alarm if the phenomenon , check the following: 1 ) driven by electrical power exceeds the value of the rated power of the inverter . 2 ) power inverter and battery and electrical connections are good . 3 ) Use the process down , whether the temperature alarm , then a period of inactivity can continue to use . Note that the use of battery power inverter power system voltage value, and read the instructions before using the fine .

Multi series inverter

Multi series inverter for electric car has many advantages . Type series arrangement greatly increases the output voltage vector , enhances the flexibility to control and improve the accuracy of control ; while reducing the fluctuation of the motor Pure sine wave power inverter neutral point voltage . Inverter bypass charging characteristics can be improved flexibility and regenerative braking control . With the growing concern for the urban environment , the development of electric cars got a rare opportunity. In urban traffic , the electric bus due to the large carrier , comprehensive benefits , become the object of priorities. Electric buses were powered by a three-phase AC motor, because the motor power, three-phase inverter device needs to withstand effects of high voltage and high current stress , high dv / dt and severe electromagnetic radiation , and the need for good cooling. The use of multi- series structure of power inverter is a single device reduces voltage stress , reducing 24v inverter the device's requirements; reduce the dv / dt value , reducing the electromagnetic radiation , heating devices are greatly reduced ; due to output increase the level of species , the control performance is better. Multi series inverter suitable for high-power electric vehicle drive system. Using multiple tandem structure , a plurality of batteries connected in series can reduce the risk that will reduce the switching device and reducing the stress of electromagnetic radiation. But the number of batteries needed increased 2 -fold. Multiple tandem structure of the output voltage vector species greatly increased, thus increasing the flexibility of the control and improve the accuracy of control ; motor while reducing the fluctuation of the neutral point voltage . In order to maintain the balance of each set of battery power , the need to ensure a solar inverters consistent runtime battery discharge time. Through the bypass mode , the flexibility to charge the battery pack , regenerative braking torque can be controlled

Principles and Applications of inverters in photovoltaic systems

Harmonic characteristics and hazards

Arc welding inverter with its high efficiency power conversion is known, along with the practical power control devices and large -capacity direction, arc welding inverter will also vehicle power inverters be entering the high-frequency , high-capacity era. Arc welding inverter on the grid , it is a big power rectifier is essentially due to power electronic devices produced after the commutation process along very steep pulse , causing serious harmonic interference. The inverter input current is a sharp wave , that the grid contains a large higher harmonics. Between the higher voltage and current harmonics severe phase shift , resulting in low power factor of the welder . The problem is that the current low-frequency distortion of a common problem of power electronic devices currently in the communications industry, household appliances have attracted considerable attention. In addition , the current multi-use hard-switching inverter welding mode during switching power devices for space inevitably produce harmonic interference. These interference by near-field and far-field coupling of conduction disturbances , severe pollution of the surrounding environment and 5000 watt inverter the power of electromagnetic environment, which will not only reduce the circuit itself inverter reliability and quality make operation of the power grid and adjacent equipment severely affected.

Because of the relatively low-voltage transformer primary side, the transformer to increase the utilization of lower cost, DC / DC converter, the push-pull circuit, the primary center tap is connected to a battery, a switch control having an end portion, alternating work efficiency can be improved. The push-pull switching circuit device with less double-ended working volume of the transformer is relatively small, the duty cycle can be increased, increasing the output power ....

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