Introduction to inverters: structure, operating principles and functions

Czym jest falownik?

An inverter is a converter that converts DC power (from a battery or storage battery) into fixed-frequency, constant-voltage, or frequency-regulated and voltage-regulated alternating current. It consists of an inverter bridge, control logic, and filter circuit. It consists of semiconductor power devices and drive and control circuits. With the advancement of microelectronics technology and power electronics technology, new high-power semiconductor devices and advanced drive control circuits have been born. Currently, devices commonly used in inverters include insulated gate bipolar transistors (IGBTs), power field effect transistors (MOSFETs), MOS-controlled thyristors (MCTs), and intelligent power modules (IPMs), which are advanced and easy to control. Examples of high-power technology. Control circuits have evolved from analog integrated circuits to using single-chip microprocessors or digital signal processors (DSP) for control, allowing inverters to continue to progress in terms of systematization, comprehensive control, energy savings, and multi-function.

Components of an inverter

DC input: The DC input of the inverter receives DC power input from the power source or battery. This part usually includes input connectors, input protection circuitry, etc.

Inverter circuit: The inverter circuit is the core part of the inverter and is responsible for converting DC power into AC power. Inverter circuits usually consist of power semiconductor devices (such as thyristors, IGBTs, MOSFETs, etc.) and corresponding control circuits to achieve voltage and frequency conversion.

Control circuit: The control circuit is used to control and regulate the inverter to ensure the stability and accuracy of the output voltage and frequency. The control circuit is usually implemented by a microcontroller or digital signal processor, including closed-loop control systems and protection functions.

Output filter circuit: The output filter circuit is used to filter out harmonics and interference in the inverter output to improve the quality and stability of the output voltage. The output filter circuit usually includes components such as inductors and capacitors.

Heat dissipation system: The inverter generates heat during operation, so an effective heat dissipation system is required to cool electronic devices and circuits to ensure their normal operating temperature. The cooling system usually includes heat sinks, cooling fans, or liquid cooling systems.

Protection circuit: The protection circuit is used to protect the inverter from abnormal conditions such as overload, overvoltage, overcurrent, short circuit, etc., and to ensure the safety and stability of the inverter and connected equipment.

Output terminal: The output terminal of the inverter provides the converted AC power output and is connected to the corresponding load equipment, such as home appliances, motors, etc. The output usually includes an output connector and output protection circuitry.

Jak działa falownik

The inverter operates using a similar principle as a switching power supply. It utilizes an oscillation chip or specialized circuit to regulate the output oscillation signal. This signal is then amplified to continuously switch the field-effect tube. By adjusting its AC properties, the inverter can produce a sine wave alternating current akin to what is found on the power grid.

The inverter begins by taking in direct current (DC) from a DC power source, such as a battery, storage battery, or solar panel.

DC-AC conversion:

Switching conversion: The power semiconductor devices (such as MOSFET, IGBT, etc.) inside the inverter work in a high-frequency switching manner to convert DC power into high-frequency alternating current (AC). The gate drive circuit of the power switch tube can be controlled by a logic circuit or a special control chip, a general-purpose microcontroller or a DSP chip, etc., and has the voltage stabilization capability of the inverter output.

Modulation and Control:

The PWM signal is then generated through the PWM control inverter to provide a margin. The amplitude can vary from 10% to 20%, and the modification from low to high is not limited; just reduce the PWM duty cycle. Therefore, the input DC voltage fluctuation range of the inverter is -15% to 20%. As long as the voltage of the device allows, there is no restriction. Only modest output pulse width adjustments (equivalent to chopping) are required. PWM adjusts the on and off times of the switching elements to control the output AC waveform. PWM technology makes the output waveform closer to a sine wave and can adjust the output voltage and frequency.

Filtering and shaping:

Filter circuit: The converted high-frequency alternating current is filtered by the filter circuit (including inductors and capacitors) to remove high-frequency components and smooth the waveform, making it close to a pure sine wave. The function of the filter circuit is to eliminate high-frequency noise and harmonic components during the switching process to obtain smooth AC output.

Voltage regulation:

Feedback control: The inverter’s built-in feedback control system continuously monitors the output voltage and current and adjusts it according to the preset values to ensure the stability of the output voltage and frequency. The feedback control system can quickly respond to load changes and maintain stable output.

Output:

AC output: The modulated, converted and filtered AC power is output through the output terminal and supplied to various AC loads, such as household appliances, electronic equipment, etc. The output AC power is generally a sine wave of 220V, 50Hz (or 110V, 60Hz, depending on the specific application and region).

Inverter Features

1. High conversion efficiency and fast startup. Nowadays, with the development of technology, the energy conversion efficiency of inverters is usually higher, generally above 90%. The conversion efficiency of inverters produced by JCPOWER can reach up to 94%.

2. It comes with safety protection mechanisms: under-voltage protection, short-circuit protection, reverse connection protection, overload protection, high-voltage protection, and over-current protection.

3. Most inverters use fully anti-oxidation-treated aluminum casings with good heat dissipation performance.

4. Stable voltage and frequency: The inverter can output stable voltage and frequency to ensure that the connected load can work normally.

5.Intelligent control:

• Digital control: Use a microcontroller or digital signal processor (DSP) for control, which improves control accuracy and response speed.
• Maximum Power Point Tracking (MPPT): In solar photovoltaic systems, the inverter is able to dynamically adjust the input voltage to maximize the output power of the solar panel.

Strong compatibility:

Adapt to different types of loads: Inverters can adapt to resistive loads (such as lights and electric heaters), inductive loads (such as motors and transformers), and capacitive loads (such as computers and electronic equipment).
Compatible with various battery types: It is compatible with lead-acid batteries, lithium batteries, and other types of batteries to meet the needs of different energy storage systems.

Modular design:

Easy expansion and maintenance: Many inverters adopt a modular design to facilitate system expansion and maintenance.

Inverter application scenarios

• Household applications: home photovoltaic systems, uninterruptible power supply (UPS) systems, emergency backup power supplies, and power supply for household appliances.
• Industrial applications: industrial automation control, industrial UPS systems, renewable energy systems, energy storage systems, industrial equipment power supply, communications and data centers.
• Mobile applications: car inverters, boat inverters, outdoor activities and camping, mobile shops and food trucks.

Precautions for using the inverter

1. The battery voltage must be consistent with the DC input voltage of the inverter. For example, a 12V inverter must be connected to a 12V battery.
2. The inverter output power must be greater than the total power of all loads, leaving a 20% margin. High-power electrical appliances and electrical appliances with motors require more margin to ensure normal use.
3. The connecting posts at the DC voltage input end of the inverter are marked with positive and negative poles. Red is the positive pole (+), and black is the negative pole (-). The battery is also marked with positive and negative poles; red is the positive pole (+), and black is the negative pole (-). When connecting, you must connect the positive pole (red to red) and the negative pole. Connect negative (black connects black). The diameter of the connecting wire must be thick enough, and the length of the connecting wire must be reduced as much as possible.
4. The inverter should be placed in a cool, ventilated, and dry place to prevent contact with rain, away from flammable and explosive materials, and placed alone and away from other objects.
5. It is strictly prohibited to use an inverter with a damaged shell.
6. Please keep your hands dry when connecting the battery, and make sure there are no other metal objects on your hands.
7. Please use a dry rag or anti-static cloth to clean the inverter.
8. When the inverter cannot be used normally, please refer to the user manual for troubleshooting.

Wniosek

Inverter technology will always be updated and improved upon as long as it exists. Inverters, a crucial component of power conversion, will be utilized in an increasing number of applications, encouraging smart and effective energy use. But in order to prevent safety mishaps, you also need to use the inverter in a standard way.

Często zadawane pytania