Achieve a more efficient and reliable solar inverter design

As energy demand continues to grow, there are reports that China in 2010 will become the number one emitter of carbon dioxide; while the scarcity of fossil fuels, to make renewable energy become a global topic. Therefore, the development of solar photovoltaic technology to become China's key energy saving strategy. "EE" market analysis report pointed out that in 2008 China mainland photovoltaic cell production ranks first in the world has such as Suntech, JA, China Sunergy and SkyTeam Elite and a number of PV cell manufacturers. The financial crisis also gave the Chinese solar PV industry an opportunity to integrate and upgrade.

Currently, the solar PV market (including photovoltaic modules and inverters) is about 30% per year cumulative annual growth rate. Solar inverter is the role of solar radiation and illumination changes with the DC voltage converted into grid-compliant AC output; while for the majority of electronics engineers, solar inverter is a technical field worthy of attention. So below describes the solar inverter design techniques that require their attention, challenges and corresponding solutions.

Based on the special nature of the solar inverter and to maintain the design of high efficiency, which requires continuous monitoring of the solar panel array voltage and current, solar panel array to understand the instantaneous output power. It also requires a current control feedback loop is used to ensure solar panel array operating at maximum output power point, in order to cope with changing high input.

Currently, there are a variety of solar inverter topologies, the most common is for single-phase half-bridge, full bridge and Heric (Sunways patent) inverters, as well as for three-phase six-pulse bridge and midpoint clamp bit (NPC) inverter; Meanwhile, the design needed to comply with safety standards, and when a failure occurs in the network can be quickly disconnected from the grid. Therefore, the solar inverter basic design criteria, including the rated voltage, capacity, efficiency, battery energy efficiency and the quality of the output AC power, maximum power point tracking (MPPT) efficiency, communications, and security features.

Rated voltage: solar inverter main function is from the photovoltaic panels (sometimes the regulated DC voltage) is converted to a variable DC voltage to an AC voltage to drive the load or to the power grid. The most common single-phase and three-phase AC voltages were 120V/220V and 208V/380V; while industrial applications, 480V are also common. The selected inverter topology, the output of the AC voltage range will determine the DC bus voltage, and the rated voltage of each semiconductor switch.

Capacity: It is the solar inverter rated power is another argument. The values ​​in the 200W (panel integration module) to hundreds of kilowatts. Greater capacity, the greater the volume of the inverter, the higher the price. The cost of solar inverters dollars / watt measured. On a right design, the determined capacity, must be surge overload conditions, and continuous working mode into consideration.

Efficiency: Each solar inverter has its efficiency (output power / input power) requirements, for example, a typical multi-kilowatt system efficiency of 95%. Array-based solar energy conversion efficiency is relatively low (about 15%) of the fact, therefore, the solar panels with a minimum output power is to get the most efficient inverter has a very important significance.