??Inverters have taken a prominent role in the modern technological world due to the sudden rise of electric cars and renewable energy technologies.

 由于電動汽車和可再生能源技術的突然興起，逆變器在現代技術世界中扮演了重要角色。

?? Inverters convert DC power to AC power, they are also used uninterrupted power supplies, control all of electrical machines and active power filtering. This video will explain how to get a pure Sinusoidal electric power output from DC power input, in a step by step logical manner.

  逆變器將直流電轉換為交流電，這一過程可以為電機工作和有功功率的轉換提供不間斷的電源。這個視頻將逐步講解如何從DC電源輸入中獲得純正弦電源的輸出。

??Alternating current periodically reverses its direction.  For this reason,  the average value of an alternating current over a cycle will be zero.  Before proceeding to sine wave production, let's see how a square wave alternating current is produced.  In fact, the old type inverter is used to produce simple square wave as their output.

 交流電會周期性地反轉其方向。因此，整個周期內交流電的平均值為零。在進行正弦波介紹之前，讓我們看看如何產生方波交流電。 實際上，舊式逆變器通過產生簡單的方波作為其輸出的。

?? Let's build an interesting circuit as shown with four switches and one input voltage. This circuit is known as full bridge inverter. 

 讓我們構建一個有趣的電路，如圖所示，其中包含四個開關和一個輸入電壓，該電路稱為全橋逆變器。

?? The output is drawn between points A and B. To make this circuit analysis easier, let's replace this actual load with a hypothetical load. Just note the current flow when switches S1 and S4 are on, and S2 and S3 are off.  

輸出在點A和點B之間繪制，為了簡化此電路分析，讓我們用一個假設負載替換此實際負載。當開關S1和S4接通，而S2和S3關斷時，注意此時電流流向。

?? Now just do the reverse and observe the current flow. It is clear that the current flow is the opposite in this case, as is the output voltage across the load. This is the basic technique that produces a square wave alternating current.

現在，只需進行相反的操作并觀察電流。顯然，在這種情況下，電流流動是相反的，負載兩端的輸出電壓也是如此。以上，就是產生方波交流電的基本原理。

?? We all know that the frequency of the AC supply available in our homes is 60 Hz. This means that we need to turn the switch on and off 120 times in a second, which is not possible when manually or by using mechanical switches. 

 我們都知道，我們家中可用的交流電源的頻率為60 Hz。這意味著我們需要在一秒鐘內將開關打開和關閉120次，這在手動或使用機械開關時是不可能的。

?? We introduce semiconductor switches, such as Mosfet for this purpose. They can turn on and turn off thousands of times per second. With the help of control signals, we can turn transistors on or off very easily. 

 為此，我們引入了半導體開關，例如MOSFET。它們每秒可以打開和關閉數千次。借助控制信號，我們可以非常輕松地打開或關閉晶體管。

?? The square wave output is a high approximation of sine wave output. Old inverter is used to produce them. That's why you hear a humming noise when you run your electric fan or other appliances using square wave power. They also heat up electric equipment. 

方波輸出是正弦波輸出的高度近似，而老的控制器一般產生的是方波電流。這就是為什么在使用方波電源運行電風扇或其他設備時聽到嗡嗡聲的原因，此外，它們還會加熱電氣設備。

?? Modern inverters produce pure sinusoidal output. Let's see how they achieve it. 

 然而，現代的逆變器輸出的是正弦電流，下面讓我們看看他們是如何實現的？

?? A technique called Pulse Width Modulation is used for this purpose. 

 為此，使用了一種稱為脈沖寬度調制的技術。

?? The logic of Pulse Width Modulation is simple. Generate the DC voltage in the form of pulses of different widths. In regions where you need higher amplitude, it will generate pulses of larger width. The pulses for the sine wave look like this.

 脈沖寬度調制的邏輯很簡單。以不同寬度的脈沖形式產生直流電壓，在需要更高幅度的區域中，它將生成更大寬度的脈沖。正弦波的脈沖看起來像這樣：

?? Now here is the tricky part, what will happen if you average these pulses in a small time interval.  You will be surprised to see that the shape of the average pulses looks very similar to the sine curve. The finer the pulses used, the better shape the sine curve will be. 

 這里面最有技巧的一部分是：如果在較短的時間間隔內，對這些脈沖求平均，會發生什么？你會驚訝地發現平均脈沖的形狀看起來與正弦曲線非常相似。使用的脈沖越精細。正弦曲線的就形狀越好。

?? Now, the real question is how to make these pulses and how do we average them in a practical way? Let's see how they are implemented in an actual inverter.

現在真正的問題是：如何產生這些脈沖，以及如何以將其在實際中應用? 讓我們看看如何在實際的逆變器中實現它們。

?? Two comparators are used for this purpose. Comparators compare a sine wave with triangular waves.  One comparator uses a normal sine wave,  and the other comparator uses an invertion sine wave.  

為此使用了兩個比較器。比較器將正弦波與三角波進行比較。一個比較器使用正常的正弦波；另一個比較器使用反向正弦波。

?? The first comparator controls S1 and S2 switches. And the secondcomparator controls S3 and S4.  

第一比較器控制S1和S2開關，第二比較器控制S3和S4。

?? S1 and S2 switches determined voltage level at point A and the other two switches determined voltage level at point B. 

S1和S2的切換，決定了A點的電壓電平；其他兩個的切換決定了B點的電壓電平。

?? You can see that the one branch of comparative output is fitted with a logic not gate.  This will make sure that when S1 is on S2 will be off . This also means that we can never turn on S1 and S2 at the same time, which will cause the DC circuit to short circuit. 

可以看到比較器輸出的一個分支裝有邏輯非門。這將確保當S1打開時S2將關閉，這也意味著我們永遠不能同時打開S1和S2，這將導致DC電路短路。

?? The switching logic of PWM is simple. When the sine way value is more than the triangular wave, comparator produces 1 signal, otherwise zero signal. 

PWM的開關邏輯很簡單：當正弦波值大于三角波時，比較器將置1，否則置0。

?? Now observe voltage variation at first comparator according to this logic. 

現在，根據此邏輯在第一個比較器處觀察電壓變化：

?? Control signal of 1 turns on the MOSFET. The voltage pulse is produced at point A are shown. 

MOSFET上控制信號置1，A點處產生的電壓脈沖如下圖：

?? Apply the same switching logic and observe the voltage pulses generated at point B. 

采用相同的開關邏輯，觀察B點處的電壓脈沖如下圖：

?? Since we are drawing output voltage between point A and B, the net voltage will be the difference between A and B. This is the exact pulse train we need to create the sine wave. The finer the triangular wave, the more accurate the pulse train will be.

由此，我們可以在點A和點B之間繪制輸出電壓，因此凈電壓將是點A和點B之間的差，這正是我們需要產生正弦波的確切脈沖序列。三角波越精細，脈沖序列將越精確。

?? Now the next question is how do we practically implement the averaging. 

 現在，下一個問題是我們如何實際中實現平均化。

?? To make it exactly sinusoidal, energy storage elements such as inductors and capacitors are used to smoother power flow. They are called passive filters. Inductors are used to smoothen the current. And capacitors are used to smooth in the voltage.

 為了使其精確地呈正弦形，使用了諸如電感和電容之類的能量存儲元件來平滑功率流。它們稱為無源濾波器。電感用于平滑電流。電容用來平滑電壓。

??  All in all, with an inverter bridge, a good PWM technique, and a passive filter, you can generate sinusoidal voltage and operate all of your appliances without any fuss. 

 總而言之，借助逆變器電橋、良好的PWM技術和無源濾波器，您可以產生正弦電壓，并且可以輕松操作所有設備。

??  The inverter technology we have explained so far has only two levels of voltage.  What if we introduce one more voltage level. This will give better approximation of the sine wave and can reduce instantaneous error.

 到目前為止，我們解釋的逆變器技術只有兩個電壓電平，如果再引入一個電壓電平該怎么辦。這樣可以更好地近似正弦波，并可以減少瞬時誤差。

?? Such Multilevel Inverter Technology is used in high precision applications like wind turbines and electric cars.

 這種多電平逆變器技術用于風力渦輪機和電動汽車等高精度應用中。

??  Inverters are used in the electric cars have intelligent frequency and amplitude control. In fact, frequency controls the speed of an electric car and amplitude controls the power of it. This way inverters act as the brain of electric cars by producing electric power ideal for driving conditions.

 電動汽車中使用的逆變器具有智能的頻率和幅度控制。實際上，頻率控制電動汽車的速度，振幅控制電動汽車的功率。通過這種方式，逆變器通過產生理想的駕駛條件電力來充當電動汽車的大腦。

總結

以上就是關于逆變器工作原理的介紹，三句話簡單總結下：

1). 通過MOSFET開關，我們在全橋逆變電路上產生高頻變化的方波

2). 通過比較器的應用，產生正弦波所需要的脈沖序列

3). 通過電容、電感等儲能元件，獲得精確的交流電，實現電機的控制和功率的轉換。