This article will provide you with all the details you will need to know about solar power inverters; these include connection types, calculations and sample projects. Even though there are no structural differences between normal power inverters and solar power inverters, they are called solar power inverters because they are sold with that name on the market and they are more often used in solar energy systems.
- What Is a Solar Power Inverter?
- Working Principle of Power Inverters. How Do Solar Inverters Work?
- Types of Solar Panel Power Inverters
- The difference between grid-tie inverter and stand alone inverter
- Power Inverters Output Wave form Types
- Solar Power Inverter Input and Output Voltages
- Power Inverter Protection Systems
- How to wire Solar Panels to Inverter?
- Solar Power Inverter Circuit Diagrams
- How to Choose the Right Power Inverter?
- Power Inverters Monitoring Systems
- Where to buy Solar Power Inverters?
- Average Costs of a Solar Inverter
- Frequently Asked Questions
What Is a Solar Power Inverter?
In electrical systems, a current has two different descriptions.These are:
Direct Current (DC): In such electrical systems, current has the same value as voltage. For example, a system that has 50V value constantly feeds on 50V voltage. In the graphic below, you can see voltage-time graphic in detail. Here you can see how voltage is constantly steady.
Alternating Current (AC): Today, all the devices that work through the grid, work with AC systems. The most important feature of this system is that the voltage between two tips constantly changes. In the graphic below, you can see how voltage changes according to time.
The main function of solar power inverters is to change the DC system which is stored in accumulators and batteries into AC system which is used by devices that work through grid. In short, it provides the transformation from DC to AC. We will examine solar power inverters that come with many different power and voltage options in detail shortly.
Working Principle of Power Inverters. How Do Solar Inverters Work?
There are two different connection points as input and output. By connecting the DC system to input part, AC power is obtained from the output part. But, how do solar power inverters carry out this transformation process? Solar inverters are composed of two different units:
1.) Convert Unit: Here, the voltage comes as DC to the system and is converted into AC by means of transistors and other electronic components. For example, if 10V DC voltage comes into the system, unsynchronized MOSFET and BJT transistors or special integrated circuits made specifically for this purpose, produce voltages changing between -10V and +10V periodically.
How do solar power inverters convert DC to AC? In the picture below, you can see this conversion process in detail.
2.) Amplifier Unit: Transformers are electrical components that are used to increase or decrease the AC values on the grid. Since they work with the magnetic current principle they are definitely used in AC systems. For example, it is used to convert 1000V AC voltage into 220V or 110V AC voltage, or into a higher voltage such as 10000V or 35000V. The basic system here is increasing or decreasing the current value while the power is the same.
For example, there is a system connected to the input of the transformer which is 200V, but 1000V voltage is required from the output. What is the output current?
The answer is very easy. Since the power that goes in and out of the transformer will be the same;
P (power) = I (current) x V (Voltage)
P-input = 200 x 4 = 800W
P-out = 1000 x (I-out)
800 = 1000 x (I-out)
I-out = 0.8A
If we go back to our main subject, transformers are used in power inverters in order to increase the voltage. The necessary AC voltage required to make transformers work, which is produced in the first unit, is transmitted to this area and here AC voltage is converted into 110V or 220V which are the grid values. In the picture below, you can see how a transformer unit works.
Types of Solar Panel Power Inverters
There are two different power inverter types according to the grid connections:
Stand Alone (Off-Grid) Inverters: They are the inverters that work separately from the grid. Electronic devices are connected to the inverter output directly. The main reason why they work separately from the grid is because there is no hardware that would enable them to work synchronously with the grid.
Stand-Alone inverters have DC input and AC output units. Output wave doesn't necessarily have to be full sine. They can have modified sine or true sine output structures. We will go into detail on those wave types shortly.
Grid Tie (Synchronous) Inverters: These are the inverters that are connected to the grid. The sine wave of the grid shows V-T (voltage-timing) compatibility. When the voltage of the grid has pick value, the inverter output voltage is also the same.
Since grid tie power inverter systems are connected to the grid, they may keep on working even though the electricity is on. There is no need to connect the devices to the inverter output separately. Connecting the inverter output to the grid appropriately will be sufficient. In the picture below you can see grid-tie power inverter connection.
The difference between grid-tie inverter and stand alone inverter
1.) While Grid-Tie works with the grid online, stand alone systems work separately from the grid.
2.) While grid-tie inverter outputs are full sine, stand alone inverters can produce outputs such as square, modified sine or true sine. Almost all electronic devices that work with AC voltage can work with these wave outputs.
3.) Since grid tie inverters have more complex electronic systems, they are more expensive than stand alone inverters which actually have the same features.
4.) You can find grid tie inverters in the market with more power and voltage options. It is a more commonly used product.
5.) You can collect the electricity that you give to the grid with grid tie inverters, from the government. There are many legal regulations and incentives in America, Britain, France and many other countries regarding this issue.
Power Inverters Output Wave form Types
a.) Square Wave Power Inverters: This is the inverter type which gives square output waves. This is the cheapest and easiest inverting process. Square wave output can make almost all grid devices work between 50 – 60 Hz. But there is a possibility that this inverter may harm these devices if used long-term. In the picture below, you can see 110V AC square wave output.
b.) Modified Sine Wave power Inverters: Output wave is square but it undergoes a special process to make it more similar to sine. Modified sine wave is a more commonly used method than square wave. It can make all AC devices work. You can't connect such devices to the grid online because grid voltage is pure sine. In the picture below, you can see modified sine waveform.
c.) True Sine Wave power Inverters: These are the inverters whose output wave type is pure sine. There is no difference between the grid voltage and this inverter output. If they have the necessary electronic hardware, they can be connected to the grid online. In all grid tie inverters, this wave technology is used. In the picture below, you can see true sine waveform.
Solar Power Inverter Input and Output Voltages
We mentioned that solar power inverters make DC ->AC voltage conversion. Inverters' output voltages are the same with the necessary input voltage values for the electronic devices that are sold to work. Their intended use is to take the DC voltage which is found in solar panels or batteries and convert it into AC voltage that these devices can use.
Power Inverter Output Voltages: City grid voltages have values such as 110V, 115V, 120V, 220V and 240V around the world. That's why the power inverters that are produced have AC outputs which have these voltage values.
Power Inverter Input Voltages: Input voltages are DC and they differ a lot. There are power inverters which have input voltages between 6V – 9V. Below, you can see the input and output values of solar power inverters of some brands and models:
- Magnum Energy MS-4024 Inverter: 4000W, Input Voltage: 25V DC, Output Voltage: 120V AC
- Solar Edge SE3300US-ER: 3300W, Input Voltage: 36V DC, Output Voltage: 210-240V AC
- MorningstarSureSineSI-300-115V-UL: 300W, Input Voltage: 24V DC, Output Voltage:115V AC
- Xantrex Trace TR1512: 1500W, Input Voltage: 12V DC Output Voltage: 120V AC Output
- AIMS Compact PWRINV500012W: 5000W, Input Voltage:10 - 15V DC, Output Voltage:120V AC
Power Inverter Protection Systems
According to their production technologies, solar power inverters can include many different protection systems. The most well known protection systems are;
Over temperature shutdown: They are also known as thermal protection systems. When a power inverter converts power over the capacity it has or at values very close to this capacity it may overheat and break down. Electronic parts generally start to break down over 90oC. In order to prevent this from happening, heat sensitive sensors are placed inside the power inverters, and this enables shutdowns at high temperatures or decrease of the power transmitted. These parts called PTC or NTC send the necessary temperature information to the central processing unit when high temperatures are reached and this activates the protection.
Automatic Overload Protection: Overload protection which is another protection system, works in order to prevent breakdowns caused by burns of the parts which are caused by power load which exceeds the capacity of the device. For example, if an inverter which has 4000W capacity is loaded with 4300W power, the protection system is activated and gives the necessary warning to the user such as closing the device and decreasing the transferred power.
Ground Fault Protection: In high capacity solar cell power inverters, grounding systems are essential. In order to protect the devices that are connected to the system and in order for the inverter to work more efficiently, the grounding should be done properly. If a high capacity power inverter has not been grounded properly, by means of the protection system that it has inside, it will warn the user and carry out the necessary processes. If grounding is not done properly, ground, not short circuit connection is carried out automatically and thus the system is protected.
Short Circuit Protection: By means of this protection system, the short circuit problem which is caused by the output cables touching one another due to user misuse is prevented. During short circuit, the device is immediately put on passive condition and is shut down. Other names for this protection system are known as AC Overcurrent protection and DC Overcurrent protection.
How to wire Solar Panels to Inverter?
We mentioned that solar power inverters have certain input values. For example, an inverter which has 24V input value works properly between the 22 – 28 V range. In order for solar panel blocks to be properly connected to inverters, the solar panel output voltage should be compatible with the power inverter input voltage. We have written other articles about solar panels and parallel and series connections of solar cell systems.
Example: How can we wire 10 solar panels with 24V output capacity to a solar power inverter which has a 48V input value?
Here the important point is to make the solar panel connections the same as the solar power inverter input. That's why we have a solar panel block which has the power of 48V and 5I and is comprised of 5 X parallel and 2 X series connections, and this block is wired to the inverter.
Solar Power Inverter Circuit Diagrams
There are sample solar power inverter pictures and illustrations below. We will publish detailed articles and documents on this issue soon.
- 1000W DC-AC Pure Sine Wave Power Inverter Circuit Diagram
- 250 to 5000W - 220V Power Inverter
- 300W Simple Power Inverter
How to Choose the Right Power Inverter?
In order to make the right power inverter choice, you should specify the answers for the following questions:
a.) How Much Power Do You Need? You have to specify where and how you will use the inverter. For example, if you are going to use it at your house, you should know for how long you are going to use the device and the power of this device. For example, if you have 2000W washing machine, 1000W dishwasher, 200W television and 500W lighting system, assuming that those devices work at the same time, you should get an inverter with the power of 3700W. It would be more suitable to get an inverter that has a power a little higher than this power however, for example 4000W.
b.) What is your Total Solar Panel System Power? The total power of the solar panels that you have will be what determines the power inverter that you will require. If you are providing the power that you obtain from the solar panels through the solar inverter directly to the grid without storing it, the total inverter power should be close to the value of the solar panel system power. For example, if you have 10KW solar panel system power, it would be suitable for you to use an inverter with 10KW power. If you are storing the power that is obtained from the solar panels in accumulators, you can use an inverter with a lower power. Here the determining factor is the total power need that is specified in a.
c.) Where to use the Solar Power Inverter? Solar power inverters can be used in many areas. We mentioned that there are power inverters according to their output wave form types. For devices that have high technology, it would be appropriate to use an inverter which has pure sine output. Some of these products are;
- Network Hardware
- Medical Equipment
- Laboratory Equipment
- Washing Machines
- LCD TVs
If you the power inverter is going to be used on simpler electronic devices or lighting systems, you should choose inverters with modified sine or pure sine output. You can use this type of inverter in vehicles such as cars, boats or recreational vehicles.
Power Inverters Monitoring Systems
Some power inverters have special software which allows them to be monitored and controlled remotely. Over the internet or broadband network and via computers or smart phones, the data on the power inverter can be read and the inverter can be controlled. Much data such as total power, input voltage, output voltage, working time, malfunctions or faults can be monitored remotely. In the picture below, an inverter monitoring system can be seen in detail.
Where to buy Solar Power Inverters?
You can purchase the solar power inverters you need from many different addresses over the internet or in stores. Below, you can see the addresses of these stores, their websites and phone numbers.
URL: Wholesale Solar
Address: 412 N. Mt. Shasta Blvd. Mt. Shasta, CA 96067
Phone: 1 (800) 472-1142
URL: Solar Electric Supply
Address: 2880 Research Park Dr. #100 - Soquel, CA 95073
URL: MR Solar
Address: 642 Ponte Villa South - Baltimore, MD 21230
URL: Xantrex Power Inverters
Address: 3700 Gilmore Way - Burnaby, BC, Canada
URL: The Inverter Store
Address: 9736 S. Virginia St. STE A - Reno, NV 89511
Before purchasing solar power inverters, calculate how much power you need and make sure to pick the inverters that have the best price/performance values. Soon we will publish the best solar power inverter article.
Where to buy used (Second Hand) Power Inverters? Addresses of some stores where you can buy second hand and properly working power inverters are shown below.
Average Costs of a Solar Inverter
Power inverters have varied prices according to their power capacities, field of use, and production technologies.
Sample price values are;
- 100W - 1000W: $50 to $1500
- 1000W - 5000W: $300 to $6000
- 5000W - 25KW: $2000 to $20.000
The most important factors that affect the prices are the manufacturing company and the output wave form.
Q: What is Maximum Power Point Tracking (MPPT)?
A: In some of the power inverters which are produced with new technology, MPPT system is used. MPPT is a system that enables the power which is loaded from the output according to the inverter's input current and voltage values, to be maximally transmitted. In order to adjust the output power, it can automatically increase or decrease the output current and voltage. The main purpose of the MPPT system is to help the inverter work at the highest efficiency.
Q: What is a Solar Power High Frequency Inverter?
A: All the normal inverters produce output voltage with 50Hz/60Hz frequency. But high frequency inverters can produce output voltage at frequencies such as 20 MHz for some special devices. You can never power your electronic devices at your home with these inverters.
Q: What are Three Phase Power Inverters?
A: Power inverters are not just produced for residential use. Inverters produced for commercial and industrial use have higher output capacities. The electronic devices used in industry or some commercial fields work with RST system known as three phase. That's why you should use 3 phase power inverters produced especially for these devices. The output voltage of these inverters are AC 380V.
Q: Does an Inverter Store the Power?
A: Power inverters absolutely do not store electric power. The storing process uses batteries.
Q: Where do I find Grounding and Mounting Instructions?
A: The instructions on installation and grounding are inside the package of the power inverter that you purchased. If you cannot find the manual explaining these processes, you can get help from us by providing the brand and model information.
Q: Can I use the Normal Power inverter with Solar Panel Systems?
A: Yes. You can use normal power inverters with solar panel systems easily. The most important thing is to make sure the solar panel system's output voltage is the same as the power inverter's input voltage.
Q: What is the difference between solar inverter and normal power inverter?
A: There are no differences between these two groups. It's just that some companies manufacture their products as solar power inverters. But the working structure and functions of normal inverters and solar inverters are the same.
Q: How does Power Inverter convert DC to AC?
A: Above we provided a detailed explanation about this. DC voltage is converted into AC voltage by means of transistors and integrated circuits.
Q: What are the most common Power Inverter electrical Input voltages?
A: The most commonly used input voltage values are: 12V, 24V, 25V, 36V, 48V, 64V, 72Vand 96V. Besides those, there are many different input voltage values but 90% of the products in the market are produced according to this standard.
Q: How do I make a Solar Power Inverter?
A: You can find the sample projects and part lists in order to make a homemade solar power inverter in the solar power section. We give you the prices of the parts and the places that you can purchase them in detail.
Q: How can I find Solar Power Inverter Projects?
A: We will be publishing sample solar power inverter projects and their plans in our renewable energy website soon. There will be detailed explanations in the project articles with PDF and Doc appendices.
Q: What kind of wires or cables will I need to connect Solar Panel Bank to Power Inverter?
A: The length and thickness of the cables differ depending on the power that you have or require. For example, if you are going to have 70A current over a copper cable, you will need at least 25mm2 of 4AWG model cable. Since the length of the cable that you are going to use will cause power loss, you should use shorter and thicker cables.
The easiest way to decrease the current that goes through the cable is to choose a power inverter that has a higher input voltage. For example, with an inverter that has 96V DC input instead of 12V, 70A, the current can be decreased down to 9A value. This will help you lower your cable costs as well. Having the batteries that stores the energy close to the solar power inverter will help you lower your installation costs and increase efficiency as well.
We have mentioned a lot of issues on solar power inverters in this article. If you have anything else that you want to know besides these or if you need help with your projects, you can use the "comments" section below. Our experts will be happy to answer your questions.