Sine-wave inverter is a kind of inverter. It is a power electronic device that converts DC electric energy (power battery, storage battery) into current (generally 220V, 50Hz sine wave). Inverter and ACDC converter are the reverse process. The ACDC converter or power adapter converts 220V AC power into DC power for use, while the inverter has the opposite effect, so it is named.
Sine-wave inverter is an electrical energy conversion device that converts direct current into alternating current. It completes the inverter task by turning on and off power semiconductor devices according to specific laws. Modern inverter technology is a science that studies the theory, application and design method of inverter circuits. It is a practical technology based on industrial electronics technology, semiconductor device technology, modern control technology, modern power electronics technology, pulse width modulation technology, semiconductor converter technology and magnetic materials. Therefore, the application of sine wave inverter runs through many fields of society and life.
Basic structure
Sine-wave inverter is a conversion device that converts DC power into AC power. It converts DC power into AC power by controlling the on and off of semiconductor power switching devices (such as SCR, GTO, GTR, IGBT and power MOSFET). The circuit that controls the power switch on and off is the control circuit of the inverter. The control circuit outputs a certain voltage pulse to make the power switch on and off in the power conversion circuit according to a certain rule. At this time, the output of the power main circuit is a specific harmonic combination, and finally the required voltage waveform is obtained through the filter circuit. The basic structure of the sine wave inverter system is shown in Figure 1.
Input circuit
The input of the inverter is usually DC (or the DC obtained by the rectification and filtering of the mains power), which includes DC power from the DC power grid, battery, photovoltaic cell and other ways. Generally, these electric energy cannot be directly used as the input side voltage of the inverter, but can only be used as the input of the inverter after passing through a certain filter circuit and EMC circuit.
Inverter main circuit
The main circuit of the inverter is a power conversion circuit composed of power switching devices. The structure of the main circuit is divided into many types. The main circuit form is also different under different input and output conditions. Each power conversion circuit has its advantages and disadvantages. In the actual design, the most appropriate circuit topology should be considered as the main circuit structure.
control circuit
According to the output requirements of the inverter, the control circuit generates one or more groups of pulse voltage through certain control technology, and acts on the power switch tubes through the drive circuit to make the power switch tubes turn on or off in the specified order, and finally obtains the required voltage waveform at the output end of the main circuit. The function of the control circuit is very important for the inverter system. The performance of the control circuit directly determines the quality of the output voltage waveform of the inverter.
output circuit
The output circuit generally includes output filter circuit and EMC circuit. If the output is DC, a rectifier circuit should be added at the back. For the inverter with isolated output, the front stage of output circuit shall also have isolation transformer. The output circuit can be divided into open loop and closed loop control according to whether the output needs a voltage stabilizing circuit. The output of the open loop system is only determined by the control circuit, while the output of the closed loop system is also affected by the feedback circuit, making the output more stable.
Auxiliary power supply
Some parts of the control circuit and input/output circuit or chips have specific input voltage requirements, and the auxiliary power supply can meet the specific voltage requirements in the circuit. Generally, the auxiliary power supply is composed of one or several DC-DC converters. For the occasion of AC input, the auxiliary power supply is completed by the combination of rectified voltage and DC-DC converter.
protection circuit
The protection circuit usually includes input overvoltage, undervoltage protection, output overvoltage, undervoltage protection, overload protection, overcurrent and short-circuit protection. There are other protections for inverters working in specific situations, such as temperature protection in low or high temperature situations, air pressure protection in some air pressure changes, and humidity protection in humid environments.
Category edit broadcast
There are many kinds of classification methods for inverters, which can be divided into three categories according to the characteristics of output wave: sine wave inverter, square wave inverter and trapezoidal wave inverter. The sine wave inverter outputs sine wave alternating current, while the square wave inverter outputs square wave alternating current with poor quality.
Figure 2: Typical three-phase full-bridge voltage input inverter
Figure 2: Typical three-phase full-bridge voltage input inverter
Inverter is usually divided into voltage input type and current input type. Unlike DC chopper, its modulation pulse width is related to sine wave, so the output current or voltage is close to sine wave. Due to the need for a large number of inductive components to simulate the current source, current-supply inverters are rarely used for electric vehicle drive. Voltage input inverter has simple circuit structure and can conduct bidirectional energy conversion, so it is almost used in electric vehicles. Typical three-phase full-bridge voltage input inverter is shown in Figure 2.
According to different needs, its output waveform can be square wave or pulse width modulation waveform, and the pulse width modulation scheme can be divided into sine PWM, current hysteresis PWM, voltage space SVPWM, etc. The inverter can use PWM technology to output pulse width modulation waveform to induction motor and permanent magnet synchronous motor. The appropriate scheme can effectively suppress harmonics, make better use of DC voltage and reduce DC voltage fluctuation.
Principle editing broadcast
The function of the inverter is to convert DC into AC. It consists of inverter bridge and SPWM wave module! The drive module is composed of a filter circuit, and the SPWM inverter circuit is the key to generate pure sine wave. The generation of SPWM wave module has always been the focus of research. SPWM is pulse width modulation technology, that is, pulse waveform with variable duty cycle. PWM control technology is based on this conclusion. Control the conduction and turn-off of the semiconductor switch device, so that the output end gets a series of pulses with equal amplitude and unequal width! To obtain the required waveform equivalently when performing pulse width modulation! If the duty cycle of the pulse series is arranged according to the sine law, the output voltage can be filtered to obtain the sine waveform! At the same time, the harmonic component in the load current is greatly reduced, which is called sine wave pulse width modulation.
Development history editing and broadcasting
The development of sine wave inverter technology has always been closely linked with the development of power devices and control technology, and has gone through five stages since its inception.
The first stage: from 1950s to 1960s, the birth of thyristor (SCR) created conditions for the development of sine wave inverter;
The second stage: In the 1970s, the appearance of turn-off thyristor (GTO) and bipolar transistor led to the development and application of inverter technology;
The third stage: in the 1980s, the advent of power field-effect transistor, insulated gate field-effect transistor and MOS controlled thyristor laid the foundation for the high-power development direction of the inverter;
The fourth stage: In the 1990s, the development of microelectronics technology made new control technologies such as vector control technology, multi-level control technology, fuzzy control technology and repetitive control technology better applied in the inverter field, which greatly promoted the development of inverter technology;
Stage 5: At the beginning of the 21st century, with the continuous progress and improvement of power electronics technology, modern control theory and microelectronics technology, inverter technology is developing towards high efficiency, high frequency, high reliability, high power density and intelligence.
Editing and broadcasting of development trend
With the rapid development of power electronics technology and the improvement of inverter control performance requirements in various industries, sine wave inverters have also developed rapidly. At present, the development direction of inverters is mainly as follows:
High-frequency
High-frequency refers to increasing the working frequency of power switching devices, which can not only reduce the volume of the whole system, but also have a good effect on suppressing audio noise, and improve the dynamic response ability of the inverter output voltage. High-frequency power switching devices correspond to high-frequency isolation transformers. The application of high-frequency isolation transformers has further reduced the volume of the whole system.
High performance
The effective value is the main parameter of the output voltage of the inverter. The effective value of the output voltage of the high-performance inverter is stable, and has high waveform quality and strong ability to adapt to nonlinear load. Because the load carried by the inverter will suddenly change in many times, high performance inverter requires high transient response performance of the output voltage. Another important parameter of AC output voltage is frequency. A good inverter requires not only stable effective value of output voltage, but also stable frequency. Only inverters with the above characteristics can be called high-performance inverters.
Parallel technology
The current inverter technology can produce high-power products, but in high-power applications, once the inverter system breaks down, the system will be paralyzed. In the system composed of low-power inverters through parallel technology, the normal operation of each unit does not affect the operation of other units, which greatly improves the reliability of the whole system.
Miniaturization
Miniaturization is the result of high frequency, because the main way to make the inverter miniaturization is to increase the operating frequency of the switch tube and use high frequency transformer. Another method is to improve the control method, optimize the spectrum of SPWM wave and reduce the filter volume.
High input power factor
Many inverter systems use a certain topology circuit to convert DC into high-frequency AC pulse, and then conduct rectification to obtain the required DC voltage. The peak of the output current will reduce the input power factor, and improving the input power factor can effectively solve the harmonic pollution of the inverter to the grid.
Intelligence and digitalization
The digitization of the inverter is not simply the application of digital devices in the inverter, such as FPGA and SCM, but the whole system depends on the computing power of digital devices and discrete control method. With the development of hardware, the processor speed is getting higher and higher, which impels the inverter to develop in the direction of intelligence and digitalization.
Application field of sine wave inverter
New energy utilization
In a broad sense, new energy refers to solar energy, including wind energy, water potential energy, chemical energy, etc. New energy such as solar energy and wind energy will become the main energy. These new energies are usually collected by photovoltaic cells made of semiconductor materials and converted into various kinds of electric energy that people need by certain scientific and technological means. Inverter technology is one of the key technologies.
Eliminate harmonic pollution of mains power
The effective management of harmonic pollution can not only improve the operation quality of electrical equipment and energy conservation, but also relate to the safety of national electricity. By rectifying the mains power and then converting it to the mains power standard using modern inverter technology, the harmonic pollution of the mains power can be purified and the safety of electric equipment and users can be protected. Inverter is an important part of small wind power generation system. It undertakes the task of converting DC power into AC power for load power supply.
Other application fields
Inverters are also widely used in many other fields, such as AC motor speed regulation, motor braking regenerative energy feedback, uninterruptible power supply system, induction heating, arc welding power supply, variable frequency power supply, etc.
Edit and broadcast the advantages of sine wave inverter
Inverter technology has many advantages:
1. Adjust the amplitude and frequency of output voltage or current flexibly;
2. Convert the direct current in the battery into alternating current or other forms of direct current;
3. Significantly reduce the volume and weight of electrical equipment and save materials;
4. High efficiency and energy saving;
5. Fast dynamic response, good control performance and good electrical performance index;
6. Fast protection.
正弦波逆变器是逆变器的一种，它是把直流电能(动力电池、蓄电池)转变成交流电(一般为220V，50Hz正弦波)的电力电子装置。逆变器与ACDC转化器是相反的过程。由于ACDC转化器或电源适配器将220V交流电整流变成直流电来使用，而逆变器的作用与此相反，因此而得名。
正弦波逆变器是将直流电转化为交流电的电能变换装置，它是通过功率半导体器件按照特定规律的导通与关断来完成逆变任务的。现代逆变技术是研究逆变电路理论和应用及设计方法的一门科学，它建立在工业电子技术、半导体器件技术、现代控制技术、现代电力电子技术、脉宽调制技术、半导体变流技术和磁性材料等科学基础上的一门实用技术，因此正弦波逆变器的应用贯穿于社会和生活的多个领域。
基本结构
正弦波逆变器是将直流电转换成交流电的变换装置，它是通过控制半导体功率开关器件(如SCR， GTO， GTR， IGBT和功率MOSFET等)的导通和关断，把直流电能转化为交流电能。控制功率开关管导通和关断的电路就是逆变器的控制电路，控制电路输出一定的电压脉冲，使功率变换电路中的功率开关管按照一定规律导通和关断，这时功率主电路的输出为特定的谐波组合，最后通过滤波电路得到需要的电压波形。正弦波逆变器系统的基本结构如图1所示。
输入电路
逆变器的输入通常是直流电(或市电经过整流滤波得到的直流电)，这些直流电包括直流电网、蓄电池、光伏电池以及其他方式得到的直流电。通常这些电能不能直接作为逆变器输入侧电压，而是通过一定的滤波电路和EMC电路之后才作为逆变器的输入。
逆变主电路
逆变器主电路是由功率开关器件组成的功率变换电路，主电路的结构形式分很多种，不同的输入输出条件下，主电路形式也不相同，每种功率变换电路都有它的优缺点，在实际设计中应考虑最合适的电路拓扑作为主电路结构。
控制电路
控制电路按照逆变器输出的要求，通过一定的控制技术产生一组或者多组脉冲电压，通过驱动电路作用于功率开关管，使功率开关管按照指定的次序导通或者关断，最终在主电路输出端得到所需的电压波形。控制电路的作用对于逆变系统至关重要，控制电路的性能直接决定了逆变器输出电压波形的质量。
输出电路
输出电路一般包括输出滤波电路和EMC电路，如果输出为直流电，应在后面加入整流电路。对于隔离输出的逆变器，输出电路前级还应有隔离变压器。根据输出是否需要稳压电路，可将输出电路分为开环和闭环控制，开环系统输出量只由控制电路决定，而闭环系统中输出量还受反馈回路影响，使输出更加稳定。
辅助电源
控制电路与输入输出电路的某些部分或芯片有特定的输入电压要求，辅助电源可满足电路中特定的电压需求。通常情况下辅助电源由一个或几个DC-DC变换器构成，对于交流输入的场合，辅助电源由整流后的电压与DC-DC变换器组合完成。
保护电路
保护电路通常包括输入过压、欠压保护、输出过压、欠压保护、过载保护、过流和短路保护。对于在特定场合工作的逆变器还有其他保护，如在温度很低或者很高的场合需要有温度保护，在某些气压变化的情况下还要有气压保护，在潮湿的环境中要有湿度保护等。
分类编辑 播报
逆变器有许多种分类方法，根据输出波弦性质可分为三类：正弦波逆变器、方波逆变器和梯形波逆变器。正弦波逆变器输出的是正弦波交流电，方波逆变器输出的则是质量较差的方波交流电。
图2：典型三相全桥电压输入型逆变器
图2：典型三相全桥电压输入型逆变器
逆变器通常分为电压输入型和电流输入型。与直流斩波器不同的是，其调制脉冲的宽度和正弦波相关，因此输出的电流或电压接近正弦波。由于需要大量的电感元件来模拟电流源，所以电流供给式逆变器很少用于电动汽车驱动。电压输入型逆变器电路结构简单且能进行双向能量转换，所以电动汽车上几乎都采用用这种逆变器。典型三相全桥电压输入型逆变器如图2所示。
根据不同的需要，它的输出波形可以为方波或脉宽调制波形，脉宽调制方案又可以分为正弦PWM、电流滞环PWM、电压空间SVPWM等。逆变器可以采用PWM技术给感应电动机和永磁同步电机输出脉宽凋制波形，合适的方案可以有效抑制谐波，更好地利用直流电压，减少直流电压波动。
原理编辑 播报
逆变器的功能是把直流电转变成交流电，它由逆变桥、SPWM波模块!驱动模块和滤波电路组成，其中SPWM逆变电路是产生纯正正弦波的关键。SPWM波模块产生一直是研究的热点，SPWM就是脉冲宽度调制技术，也就是占空比可变的脉冲波形，PWM控制技术就是以该结论为理论基础。对半导体开关器件的导通和关断进行控制，使输出端得到一系列幅值相等而宽度不相等的脉冲!来等效地获取所需要的波形， 在进行脉宽调制的时候!如果使脉冲系列的占空比按照正弦规律来安排，则输出电压经过滤波可以得到正弦波形!同时使得负载电流中的谐波成分大为减小，称之为正弦波脉宽调制。
发展历程编辑 播报
正弦波逆变器技术的发展始终与功率器件及其控制技术的发展紧密结合，从开始发展至今共经历了五个阶段。
第一阶段：20世纪50年代到60年代，晶闸管(SCR)的诞生为正弦波逆变器的发展创造了条件；
第二阶段：20世纪70年代，可关断晶闸管(GTO)及双极型晶体管的出现使逆变器技术得到了发展和应用；
第三阶段：20世纪80年代，功率场效应管、绝缘栅型场效应管和MOS控制晶间管的问世为逆变器的大功率发展方向奠定了基础；
第四阶段：20世纪90年代，微电子技术的发展使新的控制技术如矢量控制技术、多电平控制技术、模糊控制技术和重复控制等技术在逆变领域得到了较好的应用，极大的促进了逆变器技术的发展；
第五阶段：21世纪初，随着电力电子技术、现代控制理论和微电子技术的不断进步和改进，逆变器技术朝着高效率、高频化、高可靠性、高功率密度和智能化的方向发展。
发展趋势编辑 播报
随着电力电子技术的高速发展和各行业对逆变器控制性能要求的提高，正弦波逆变器也得到了快速发展，目前逆变器的发展方向主要为：
高频化
高频化指的是提高功率开关器件的工作频率，这样不但可以减小整个系统的体积，而且对音频噪声有很好的抑制作用，同时提高了逆变器输出电压的动态响应能力。高频工作的功率开关器件对应于高频隔离变压器，高频隔离变压器的应用对整个系统的体积又有了进一步的减小。
高性能化
有效值是逆变器输出电压的主要参数，高性能的逆变器输出电压有效值稳定，同时有很高的波形质量，适应非线性负载的能力强。由于很多时候逆变器所带的负载会突变，高性能逆变器要求输出电压有较高瞬态响应性能。对于交流输出电压的另一个重要参数是频率，好的逆变器不但要求输出电压有效值稳定，而且要求频率也稳定。具有上述特点的逆变器才能称得上是高性能逆变器。
并联技术
目前的逆变器技术可以制作出大功率产品，但是在大功率应用场合一旦这个逆变器系统出现故障，将会导致系统瘫痪。而在由小功率逆变器通过并联技术组成的系统中，每个单元的正常工作与否都不影响其它单元的工作，这样对于整个系统的可靠性就有了极大的提升。
小型化
小型化是对应于高频化的结果，因为使逆变器小型化主要方法就是提高开关管工作频率，使用高频变压器。另一种方法是改进控制法，优化SPWM波的频谱从而减小滤波器体积。
高输入功率因数化
很多逆变系统使用一定的拓扑电路把直流电转换成高频交流脉冲，再进行整流得到所需的直流电压。输出电流出现的尖峰会降低输入功率因数，提高输入侧功率因数可以有效解决逆变器对电网产生谐波污染。
智能化与数字化
逆变器的数字化不是简单在逆变器中应用数字器件，如FPGA和单片机，而是整个系统依靠数字器件的计算能力和离散控制法完成。随着硬件的发展，处理器速度越来越高，促使逆变器向着智能化与数字化的方向发展。
正弦波逆变器的应用领域编辑 播报
新能源利用
新能源从广义上来说指太阳能,它包括风能、水的势能、化学能等。新的能源如太阳能、风能将成为主要能源。这些新能源通常用半导体材料制成的光伏电池收集，运用一定的科学技术手段转化成人们需要的各种各样的电能，逆变技术就是其中的关键技术之一。
消除市电谐波污染
对谐波污染的有效管理不仅能够提高用电设备运行质量和能源节约,而且关系到国民用电安全的问题。通过对市电整流后利用现代逆变技术再转换为市电标准,可以净化市电的谐波污染,保护用电设备和用户安全。 逆变器是小型风力发电系统中重要的组成部分,它承担将直流电转换成交流电为负载供电的任务。
其他应用领域
逆变器还广泛应用于其他多个领域,如交流电动机变速调速、电动机制动再生能源回馈、不间断电源系统、感应加热、弧焊电源、变频电源等。
正弦波逆变器的优点编辑 播报
采用逆变技术有很多优越性：
1.灵活地调节输出电压或电流的幅度和频率；
2.将蓄电池中的直流电转换成交流电或其他形式的直流电；
3.明显地减小用电设备的体积和重量，节省材料；
4.高效节能；
5.动态响应快、控制性能好、电气性能指标好；
6.保护快。