The inverter is done bad, the houses are burned!

Photovoltaic systems include components, brackets, combiner boxes, distribution cabinets, inverters, cables and other accessories, which only the inverter as the brain “CPU”, with proactive detection and prevention capabilities, when the grid failure or component malfunction , the inverter will be sampled by the current sensor and voltage to make timely judgments, indicating “executing agency” contactor or breaker opens to protect the personal safety, power, equipment and so on.

The inverter inside AC contactors, DC circuit breakers, AC circuit breaker, where they are installed in different functions are not the same, AC contactor assume regular boot off the action, usually to first reduce the power inverter, AC contactor will begin operations. DC circuit breaker main role is to disconnect between modules and inverters, when the component or DC cables short circuit, grounded; inverter bus capacitors, IGBT short circuit occurs, it must be removed from the DC switch.

From a security point of view, the inverter input DC switches and AC switches are made of molded case circuit breakers, circuit breakers with automatic over-current and short circuit protection. When the inverter short circuit fault occurs, can timely make solar battery positive and negative pole to separate, cut off the power grid and inverters contact.

Now some of the inverter in order to reduce the cost, the load switch and fuse the mode to replace the circuit breaker, brought a great hidden danger to the grid and solar modules.

Due to the short circuit solar component is about 1.06 times the rated current, while the minimum fusing current fuse is more than 1.2 times the rated current, so when the inverter short circuit fault, DC fuse would not have blown, solar component will produce a short circuit. If not promptly treated, a fire may occur.

It is strongly recommended that you select regular inverter factory manufactured products, the only way to protect the inverter and you other equipment! Our company produced the inverters have quality assurance, We provide both off-the-shelf and customized design service, OEM or ODM service for your choice! Welcome to consult the discussion!


How inverter batteries connected in series and in parallel?

The difference of Voltage between four 1.5V batteries in series and in parallel

The voltage remain at 12V when two 12V batteries are connected in parallel; the voltage become 24V when two 12V batteries are connected in series, and the voltage is 48V when four 12V batteries are connected in series.

When the batteries are connected in series, the positive terminals should connect to the negative terminals. And when the batteries are connected in parallel, the positive terminals should connect to themselves, and the negative terminals should connect to themselves. If you want to increase the battery capacity, you should choose the connect way in parallel, and if you want to improve the battery voltage, then the connect way in series should be chose.

What is off-grid inverter system?

Off-grid power system is the most widely used system at present which can be used in completely separate environments. It can be used to solve the problem that a place away from urban areas, and the electricity is inconvenient, or with power shortage , especially that it suitable to use in the place where needs an independent power supply, such as the mountains, the fishing-boats and so on.

Off-grid system components Figure

1,The devices for Off-grid systems: The most basic device include solar panels, off-grid inverter, solar charge controller, battery and so on, which we introduced in the article “How inverter works“.

2,Date reference for off-grid inverter system configuration: the size we configured for off-grid power generation system is mainly to see the size of the load power, and the working time of the load, that is to say, you should figure up the total power you want to use. And the back-up time also should be considered, if continuous rains, you should calculate the working days for your loads. All of the above factors must be considered. We can know that the power load is 1000W, continuous working time is 5 hours, then the amount of electricity consumed is 5 kWh, if you want to send out 5 kWh, theoretically 1000-1500W is sufficient. But in fact, our configuration is 2KW, because of the reason of efficiency. For solar panels in off-grid systems, the actual and theoretical power generation capacity is still a big gap, that is to say, there will be some loss of power when the solar panels being charged, and under normal circumstances, the conversion efficiency should be about 70% when the allocation of voltage is in a reasonable case. And of course, there will be power losses between any devices, but more or less only. Overall system efficiency from the network should be around 50-60%, due to that, the efficiency of the panel is 70%, the battery discharge depth is generally about 80%, and the efficiency of inverter is usually around 90%, integrated down, the efficiency of the system is 50- 60%.

3,The following sets of conventional configuration instructions to do next:

To do a system that can supply power for TV, computers and other small appliances. The problem we must first consider is the power, we should know how many hours the above appliances to be used, if there’s still a sunny day, we should calculate how long can emit so much electricity. And then, the issues such as solar panels and batteries should be considered. Please check the configuration I recommended as follows: 500W solar panel, 2 units of 50AH battery, 1 unit 1000W off-grid inverter, and 1 unit 20A controller. And here I want to explain the reason why use two batteries. Because most cost-effective solar panels is now the 36V 250W polycrystalline panel,  its good to the charge battery with 24V voltage, if you are use it to charge a 12V battery, and use of an ordinary PWM charge controllers, then when you actually charge the maximum power is only 12V * 8A = about 96W, so the actually power for use is less than 100W for 250W board. This way will cause great waste.

How to choose the inverter. There’s a very important relationship between the efficiency and the allocation of voltage in above mentioned things in this series. Operating power of the inverter is usually recommended within 80% of nominal maximum power, that is to say, for 1000W inverter, we recommended maximum load with less than 800W, which can improve the safety of the inverter.

The configuration of voltage is mainly refer to the power of the load, and the voltage of the solar panel. And here we recommend the configuration relationship as follow: for Load of 1000W or less, you can use a voltage of 12 to 24V, for 1000-2000W load, we recommend using a voltage of 48V or 24V, and for 2000W or more load, be sure to use a voltage of 48V.

The reasons are as follow:

For 1000W load with 12V voltage, the current is about 85A, it’s very high, not very safe.

For 2000W load with 12V voltage, the current is near 170A, it’s very unrealistic. .

For 3000W load with 12V voltage, the current is near 250A, theoretically feasible, but in reality, really not seen. You should imagine that how thick the wire you need if the current over-250A

If using 24V voltage for above loads, the current will be decreased by 50%, if the system with 48V voltage, the current will be decreased by more 50% which is only a quarter of the current above. And it’s obviously to see the Safety and feasibility.

About the battery capacity. The decisive factor is that how much electricity you want to save, and it can be calculated by the power of load and the working time. For example, you have a load of 1KW to run four hours (four kWh of electricity). A 100AH the battery can save about 1.2 kWh, relatively speaking, the depth of discharge is 80%, then 1.2 * 80% = 0.96 kWh or so, that is to say a 100AH battery usually has a kilowatt or so, if you want to keep four kWh of electricity, it will need four batteries. I said above. 1KW load recommended 12V-24V system, this is also not absolute, if you have four batteries, they can be composed of whole system, that is 12V, and also the whole string can be 48V with two strings in parallel and two strings in series, that is 24V, this also should combine your board to decide. We recommend this power system with 24V or 48V voltage because of the high efficiency and the good scalability. Late upgrades do not have to consider the problem that replacing the inverter and controller.

How to choose the controller: the type of controller, usually we use PWM type, in the above configuration, we have this controller is based mainly in terms of, if you want to use MPPT controller for the above system, the voltage of this configuration can be appropriate to relax. For example, you can use the panel of 30V to charge 12V battery, which is entirely possible. And the efficiency is the same with the efficiency for PWM controller to charge 24V Battery.

The application of inverter

A power inverter converts DC power or direct current to standard AC power or alternating current, which allows you to run electrical equipment off your car or marine battery for mobile applications, emergencies or simple convenience.

Power inverters are small rectangular devices that have a trailing wire with a jack that plugs directly into the cigarette lighter on the dashboard. They might also come with jumper-like cables for connecting directly to a battery. The device normally has one or two outlets for standard electrical cords. Your laptop, small-screen television, video game player or portable DVD theater are all examples of devices that will get you through a long ride, assuming you’re not the one driving!

Power inverters are great for camping at parks that do not provide electricity. The toaster, blender, and boom box can all still be used. On your boat you can plug in the digital movie camera to capture those great water-skiing videos you might have missed after the camera’s battery ran low!

In a utility outage a power inverter can be used for emergency electricity. Just run an extension cord from your car into the house, or if you have a charged spare battery you can connect the power inverter directly. Plug in a radio to tune into important alerts, run essential medical equipment, lights, or whatever else you need that falls within the inverter’s power limits.

News and Policies for PV inverter

In 2011, both Germany and China decrease the subsidy for PV industry, which influencing development of PV industry negatively. Nevertheless, this is a good sign of PV industry. It implies that PV industry walk out of government’s swaddle. The drive force of PV industry switched from subsidy to cost. Negative impact of new subsidy policy will only last for a short time.

Wang Sicheng, a researcher from energy research institute of SDRC, claimed that total PV installation volume in China would reach 100GW in 2020, because of the explicit cost decrease trend. Zhao Wenyu, the vice chairman of China Renewable Energy Institute, predicted that annual installation volume in 2011 will be 500~700MW in China. All these indicate a fast growth of China PV inverter industry in future.

On Mar. 11th, earthquake in Japan resulted in a nuclear leakage. On Mar. 12th, Zhang Lijun, the vice minister of environment protection minister, claimed that this leakage accident will not change the plan and development of Chinese nuclear power. Although nuclear power strategy in China will not be easily changed, this tragedy raises public concern about safety of nuclear power plant in worldwide range. In short term the fast development of nuclear power will be constrained. Solar power will benefit from this accident.

Types of inverter and its development

1.On-grid inverter
On-grid inverter contains Max Power Point Tracing (MPPT) module and inverter unit (DC-AC). Inverter always needs to trace the max power to generating power. Therefore, voltage, frequency and phase of AC Output should be the same as those of grid.
2.Off-grid inverter
Off-grid inverter transmits power by energy storage device. Voltage and current are in a stable situation. Therefore, power of off-grid inverter is highly related to power and quality of load.
The technology of large power electronic elements is the foundation of development of modern inverter technology, because the key component of inverter is electronic elements.
PV inverter is developing to higher frequency and smaller size. Inverters without isolation transformer are the mainstream now. The most promising direction is micro-converter and mini-inverter (module inverter). Enphase, an English energy company, Microinverter, an US company, and Solarmagic technique of State Semiconductor of America draw attention of public.
Due to heterogeneous sunshine, diversity of PV module, complexity of installation, such as BIPV and tree shade on rural house, micro-inverter has a much wider market. Inverter will realize modularization and generate in a distributed pattern.
The difference between A and B, please see: 《What’s the difference between On-grid inverter and Off-grid inverter?

What’s the difference between On-grid inverter and Off-grid inverter?

Off-grid inverter(Figure 1 shows), by name of view, it is a kind of Inverter that not linked with Power Grid.
Solar modules will be sent electricity stored in the battery, and then through the off grid inverter to convert the DC power in the battery into AC 220V to load.
Similarly, On-grid inverter(Figure 2 shows)is that convert DC power sources from solar panels to high –voltage power, and then flow into the grid, but without the need of battery storage, this is the difference between them.