First, the basic principle of inverter

Inverter is a device that converts direct current to alternating current, its main principle is to use the switching characteristics of semiconductor devices (such as field effect tubes or thyristors, etc.) to control the power supply voltage and current through rapid switching, so as to achieve the conversion of direct current to the corresponding frequency and voltage of alternating current. Specifically, when the input direct current passes through a semiconductor device in the inverter, it is divided into a series of pulse signals, which are filtered and adjusted to produce an alternating current of the same frequency, amplitude and waveform as the desired output. Inverters are widely used in solar power generation, wind power generation, household appliances, UPS and other fields.

Second, inverter circuit structure

The internal circuit structure of the inverter is divided into two parts, namely, the control circuit and the power circuit.

The control circuit mainly realizes the signal regulation and control of the inverter, including the control of the switching state of the thyristor or the field effect tube, the generation of high frequency drive pulse signal and the protection of the function. The control circuit usually consists of a microprocessor or a complex circuit board.

The power circuit is the core component of the inverter, which converts the DC power supply to the AC output, including the rectifier circuit, the filter circuit and the inverter output circuit. The rectifier circuit converts the input alternating current into direct current, the filter circuit smooths the rectified direct current, and the inverter output circuit uses semiconductor devices to convert direct current into alternating current with the required voltage, frequency and waveform.

The internal circuit structure of the inverter is complex and requires scientific and precise design and manufacturing process to ensure its performance and safety.

Three, full bridge inverter

Full-bridge inverter is a common inverter circuit, which is widely used in industry, aviation, ocean and other fields. The basic principle is to achieve AC output by alternating the DC power supply through four switching tubes (often using IGBT or MOSFET).

Specifically, the four switching tubes in the full-bridge inverter can be divided into two groups: the upper and lower bridge arms. The upper bridge arm is composed of two switching tubes and a midpoint, and the lower bridge arm is also composed of two switching tubes and a midpoint. In each half-cycle, the two switching tubes on one of the bridge arms are switched on and the two switching tubes on the other bridge arm are disconnected, which makes the DC voltage of the power supply successively connected to the output L1 and L2 at the midpoint, thus forming a positive and negative half cycle of the AC.

In the control of full-bridge inverter, it is necessary to carry out precise switching control on the four switching tubes to ensure that they can be correctly switched on and off in different states. In addition, auxiliary components such as filter capacitors and inductors are required to smooth the output waveform and reduce transient and noise interference.

In short, the full bridge inverter has the advantages of simple and reliable, stable output, etc., and is widely used in high performance requirements.

Fourth, inverter PWM control principle and structure

Pulse Width Modulation (PWM) control is one of the main control technologies of the inverter. Its basic principle is to adjust the frequency and amplitude of the output waveform by controlling the on-time of the switching tube.

Specifically, PWM control is to convert the DC power supply into a set of short pulse signals and control its duty cycle to achieve high-quality AC output. In the inverter, the comparative PWM control mode is used, that is, the input signal is compared with a Gaussian wave, an error signal is generated, and the control signal of the inverter switch tube is generated according to the error signal, so that it can realize high-frequency modulation and generate the required waveform. In the concrete implementation, the opening and closing of each switch tube can be completed through the calculation of the controller and the control of the PWM chip.

The PWM control structure of inverter mainly consists of comparator, error amplifier, low-pass filter and PWM controller. The comparator is mainly responsible for generating the error signal and feeding it into the error amplifier; The error amplifier amplifies the error signal and outputs PWM control signal. The PWM controller transmits the PWM signal to the switching tube such as IGBT or MOSFET to realize the control of the output waveform.

In short, PWM control is an important technology for inverter to achieve high-quality AC output, with high precision, good stability and other characteristics, and has been widely used in solar power generation, electric vehicles and other fields.

Five, there are several main communication protocols of the inverter

The main communication protocols of the inverter are as follows:

1, Modbus protocol: Modbus is a common serial communication protocol, which can realize the data exchange between different devices. In the inverter, Modbus protocol can realize remote monitoring and control, including real-time monitoring of inverter output power, voltage, current and other parameters, and adjust the output waveform and frequency.

2, CAN bus protocol: CAN bus protocol is a wide area network (WAN) based network protocol, with high reliability, high speed, high system integration characteristics. In the inverter, the CAN bus protocol can realize the data exchange and control between multiple inverters, as well as the communication with other devices.

3, Ethernet protocol: Ethernet is a local area network (LAN) based standard network protocol, its data transmission rate is fast, high flexibility, support a variety of applications and other characteristics, so that the inverter can communicate through the Internet, the use of Web-based interface to set the inverter parameters and other functions.

4, Zigbee wireless protocol: Zigbee is a low-power wireless protocol, which can establish a stable and secure network in the home, office and other environments, supporting direct communication between target devices. In the inverter, the adoption of Zigbee wireless protocol can realize the wireless communication between the inverter and other devices, and expand the scope of monitoring and control.

In short, different communication protocols are used in the inverter to quickly and accurately achieve data exchange and remote control, providing users with more efficient and convenient services.

Six, What is the main role of the inverter in the BMS, what is the role

The home energy storage inverter mainly plays the following roles in the BMS (battery management system), and plays the following roles:

1, DC/AC inverter: the battery of the home energy storage system stores direct current, and alternating current is needed when the home uses electricity. Inverters can convert direct current into alternating current and supply it to household electrical equipment or into the public grid.

2, grid support: energy storage inverters can not only supply power to the home, but also feed excess electrical energy (obtained by photovoltaic modules, etc.) into the grid. At the same time, the inverter can also adjust the household electricity load, reduce the power consumption in the peak period, and achieve the valley height balance.

3, BMS integration: The inverter can be integrated with the battery management system (BMS), by monitoring and controlling the battery voltage, current and other parameters, to achieve accurate control and protection of the energy storage system. For example, when the battery is low, the inverter can stop supplying power to the grid according to the instructions of the BMS to avoid damaging the battery and affecting the service life.

4, energy saving and emission reduction: the inverter can optimize the control of household electricity load, reduce the dependence on traditional fossil energy, so as to achieve the purpose of energy saving and emission reduction and environmental protection. At the same time, the inverter can also buy and sell electricity at the right time in the power market, saving electricity costs.

In short, as one of the core products of the home energy management system, the home energy storage inverter has a variety of important functions and roles, and can further improve the efficiency and control accuracy of home energy use by integrating with the battery management system and other devices.

Seven, the inverter DC-DC circuit

The DC-DC in the inverter refers to the DC-DC converter. In the inverter, DC-DC is mainly used to adjust and convert the input voltage to meet the power supply requirements of the inverter and its output load. Specifically, DC-DC can achieve the following functions:

1, voltage rise and fall: when the input voltage of the inverter is lower than the output voltage, DC-DC can increase the voltage to ensure the normal operation of the inverter. Conversely, when the input voltage is higher than the output voltage, the DC-DC can reduce the voltage to reduce the power loss of the inverter.

2, current control: DC-DC can achieve accurate control of the output current according to the needs of the output load by changing the switching frequency and duty ratio and other parameters to prevent the impact of circuit overload or power supply fluctuations on the output load.

3, energy storage: DC-DC can also achieve energy storage and management, such as through the use of battery packs, to achieve the storage and reuse of renewable energy generated by photovoltaic or wind energy.

4, safety protection: In the inverter overload, short circuit, undervoltage and other abnormal circumstances, DC-DC can immediately cut off the input power to avoid further damage to the inverter and output load.