PV inverter overview Inverter, also known as power regulator, can be used in solar power generating systems as independent power supplies or grid-connected. According to waveform modulation, inverters can be square wave, step wave, sine wave, or integrated three-phase. In grid-connected systems, inverters can be transformer-type or transformer less.Structure of PV inverter Semiconductor devices make up the boost circuit and inverter bridge circuit of the inverter, which adjusts direct AC conversion power. Following are the primary semiconductor devices:
(1) Current sensor: demands high accuracy, rapid reaction, low temperature resistance, high temperature resistance, etc., different current sensors consume varied power, usually Hall current sensor for current sampling;
(2) Current transformer: broad current range, often BRS series;
(3) Reactor.Working principle of PV inverters PV inverters have a boost circuit and an inverter bridge circuit. The boost circuit boosts the DC voltage to the output voltage, while the bridge circuit converts it to fixed frequency AC voltage. Thus, the boost and inverter bridge circuits convert DC power to AC points.Photovoltaic inverters have 10 common issues and processing techniques.
1. Utility problems Too low, too high voltage and frequency are utility power abnormalities (error codes F00-F03).① Determine if the machine's safety standard fulfils local power grid criteria.② Verify AC output terminal connections and measure voltage using a multimeter.③ Disconnect the PV input, restart the machine, and check for normal operation.④ If the issue persists, contact the distributor.
2. Low insulation impedanceF07 error. ① Disconnect the PV input, restart the machine, and check for regular operation.② Verify PV+ and PV- earth resistance exceeds 500KΩ.For issues below 500KΩ, contact the local inverter distributor or battery board provider for assistance.
3. Excessive leakage currentF20 error Disconnect the PV input, restart the machine, and check for regular operation.② If unsuccessful, contact the distributor.
4. Radiator and ambient temperatures are too highF12, F13 errors. ① Disconnect the PV input, restart the machine, and check for regular operation after a few minutes of cooling.② Verify if ambient temperature exceeds machine's typical range.If the issue persists, contact the distributor.
5. Monitoring without dataWiFi tracking:Connect the inverter WiFi, check the monitoring page for inverter information, re-plug the built-in WiFi module or check the external WiFi RS485 connection if there is no inverter information, and if you can't search the inverter WiFi, check the built-in WiFi module for poor contact or the external WiFi power.To monitor GPRS, test the Internet signal strength of the same service provider at the inverter installation location. Check for weak contact or unpowered external GPRS modules.
6. Low insulation impedance Use exclusion. Remove all the power cables on the input side of the inverter, then connect them one by one, use the inverter power-on detection of insulation impedance to find the problem strings, check the DC connector for a water-flooded shorting bracket or burnt fusion shorting bracket, and check the component for a black spot burnt at the edge that causes component leakage.
7. Leakage current fault Low-quality equipment, poor installation, and the inappropriate placement exacerbate this problem. Failure points abound: low-quality DC connectors, components, component installation height is unqualified, grid-connected equipment of low quality or water leakage, and similar problems can be found through the sprinkler ** point and solved by good insulation. If the problem is the material province, replace the material.
8. The inverter does not respond DC input wires should not be reversed, the normal DC connection has an anti-dumbing effect but the crimp terminals do not. Please read the inverter manual to verify that the positive and negative terminals and crimp are critical. The inverter's reverse short circuit protection allows it to start normally after normal wiring.
9. Grid faultGrid overvoltage: The work's heavy load (power consumption of large working hours) and light load (power consumption of less rest time) is reflected here, in advance to survey the grid voltage, and inverter manufacturers to communicate with the grid to do a combination of technology to ensure that the project design within a reasonable range, do not "take for granted", especially in rural power grids, the inverter to the grid, the inverter is very important. Rural grids and inverters have strict voltage, waveform and distance limits. Most overvoltage problems are caused by raw grid light load voltages exceeding or approaching safety protection values. If the grid line is too long or poorly crimped, the power plant cannot operate normally and steadily. The answer is to determine the power supply authority to coordinate the voltage or disconnect the grid and monitor the quality of the power station construction." Grid under-voltage" : This problem is similar to grid over-voltage, but it can also result in a false voltage if the independent phase voltages are too low, the load distribution on the grid is incomplete, and the phases of the grid are dropped or disconnected. Grid Frequency Over/Under: Grid Frequency Over/Under: The presence of this difficulty in a normal grid indicates poor grid health.No grid voltage? Check the grid tie lines.Check for grid phase defect, or no voltage line.
10. DC overvoltage protectionWith component pursuit of high-efficiency process improvement, power level is constantly updated to rise, as are component open-circuit voltage and operating voltage. Temperature coefficients must be considered at the design stage to avoid overvoltage and hard damage to equipment at low temperatures.
SIX TECHNOLOGICAL TRENDS IN DEVELOPING PV INVERTERS
Trend 1: Inverter hardware is evolving rapidly, including SiC, CAN, DSP and new topologies, resulting in improved efficiency. China's efficiency has reached A+, with the goal of A+++.
Trend 2: centralised inverter power, efficiency, voltage increases.2.5MW and other higher power level inverters will be extensively employed since they cost roughly 0.1 yuan/W less than 1MW square array, reducing the initial expenditure of 10 million for a 100MW power plant. Cable matching guarantees DC part loss consistency.The 1500V system will dominate large-scale power plant construction. Except for the components, it saves 0.2 yuan/W, or 20 million for a 100MW power station.
Trend 3: String inverters are increasing in power density and power per unit. String inverters continue to grow in power up to 80kW, increase in power density, and decrease in weight for challenging applications where installation and maintenance are difficult. 40kW string inverters from Sunny Power are the lightest in the industry, weighing only 39kg. Sunny Power has always used intelligent fan cooling to prevent internal component temperature increase and improve inverter overload capacity in high-temperature conditions.
Trend 4: More Module-Level Products Modules such as Enphase microinverters and SolarEdge power optimizers are becoming more common. Industry research firm GTM expects shipments of module-level power electronics (MLPE) to increase from 1.1GW in 2013 to more than 5GW in 2017.
Trend 5: Grid Adaptability and Greater Safety and Reliability Protection Leakage protection, SVG functionality, LVRT, DC module protection, insulation impedance detection protection, PID protection, lightning protection, PV positive and negative reverse polarity protection, and other ever-improving features increase the grid adaptability and system safety of inverters.
Trend 6: Improved inverter environmental adaptability With the increased use of photovoltaic power stations in harsh environments like coastal, desert, plateau, etc., the inverter's corrosion resistance, sand resistance, and other environmental adaptability are improving to ensure high reliability.
Zhao Wei said that through a variety of new technologies, the application of new products continues to promote PV technology, improve system efficiency PR, reduce system life cycle cost of electricity (LCOE), and ultimately achieve Internet parity, which is everyone's common struggle.The power station design will be modified, system integration improved, and an integrated inverter, medium voltage transformer solution can simplify the system to the extreme, decreasing costs, simplicity of use, efficiency, and dependability.PV inverter industry development is rising, a variety of new technologies, new products, ever-changing, adaptive to local conditions, a hundred competitions; in large ground power stations, centralised solutions for initial investment are lower, later operation and maintenance costs are only string 1/3, a number of power station operation results show that string power generation with centralised is the user's preferred choice; 2/2.5M String inverters in distributed applications are also growing, and high power, efficiency, and power density are the future directions. PV + Internet will become mainstream, and PV + energy storage applications will have a bright future.
