在电机运行的过程中，我们首先需要理解的是，电机是由定子和转子的磁场同步旋转，从而建立起一个具有同步旋转速度的旋转坐标系，这个坐标系被称作D-Q旋转坐标系。在这个坐标系下，所有的电信号都可以描述为常数。为了更好地研究电机矢量控制的问题，我们是否能够直接从仪器中获得D-Q变换的结果呢？

D-Q变换是一种非常有用的解耦控制方法，它将异步电动机的三相绕组变换为等效的二相绕组，并且将旋转坐标系变换成正交的静止坐标。这意味着我们可以得到用直流量表示电压及电流之间关系式。这种变换使得各个控制量可以分别进行控制，有助于消除谐波电压和不对称電壓带来的影响，因为它应用了同步旋转坐标变换，所以容易实现基波与谐波分离。

由于直流電機其主磁通基本上由励磁绕组中的励磁電流决定，因此这也是直流電機数学模型及其控制系统比较简单的一个根本原因。如果我们能够将交流電機的物理模型等效地改变成类似直流電機模式，那么分析和控制就能大大简化。正是按照这样的思路，座標變換才得以進行。

交流電機中的三相對稱靜止繞組A、B、C，如果通過平衡三相正弦電流，就會產生一個叫做合成磁動勢F 的旋轉磁動勢，這個動勢在空間呈現為正弦分布，以同步轉速ws（即為時間上互差90°）順著A-B-C這一序列進行運動。此種物理模型如圖所示。

然而，並不是說我們非要使用三相才能獲得這樣的一個負責任，我們也能夠使用二相、三相、四相……甚至更多對稱多重繞組來產生同樣效果，只要這些繞組以平衡多重交流進行運行，都能夰生成一個相同方向與大小之間有關聯並且隨時間呈現逆時針循環變化之合成磁動勢F。但最簡單的情況就是兩次平衡交流，用於激活兩次異步繞組a和b，每一次皆與另一次偏移90度角，並同時以不同的瞬間點開始，這樣即可形成一個帶有90度偏移角度之合成位置固定不變之線性向量，即從空间上的两次异步扭矩轴线产生一个共同点，使得这些扭矩轴线成为空间上的两个扭矩轴线构成了一个新的空间扭矩轴线，该空间扭矩轴线是一个新的参考框架，是指三个绝对或参照定的特定位置或方向。

當然，在图1与2中两个rotating magnetic field大小和speed都相同时，即认为图2中的two-phase winding与图1中的three-phase winding等价。当包含两个winding in one core of the motor with a synchronous speed, then the magnetic field will also rotate accordingly. This is what we call a rotating magnetic field.

By using this rotating magnetic field, we can create an equivalent model for three-phase induction motors that can be analyzed and controlled like a DC motor. This equivalence allows us to simplify the analysis and control of induction motors, making them easier to understand and work with.

The D-Q coordinate transformation is widely used in electrical engineering for various applications including:

Electric machine control

Electric machine transient analysis

Fault diagnosis

In addition to its use in electric machines, D-Q coordinate transformation has been applied in power system fault analysis and power grid energy quality detection and control as well.

To apply D-Q transformation in electric machine testing, it is essential to accurately determine the rotor position and measure the three phase currents accurately using high-speed FPGA parallel processing algorithms along with Clark's transform which converts relative stationary two-phase coordinates into relative stationary two-axis coordinates by obtaining corresponding outputs Iαand Iβ through Park's transform which converts relative stationary two-axis coordinates into relative rotor-stationary two-axis coordinates thus calculating IDand IQ.

The process of controlling electric machines involves reversing this process: first setting up excitation current and torque current; then transforming these values back into relative rotor-stationary two-axis; finally transforming these values back into relative stationery three-phases; thus implementing control over electric machines.

Currently ZLG Zhongliang Electronic Co., Ltd plans to implement this D-Q transformation function on their power analyzer instrument which can provide reference for developing designs for motor controls as well as troubleshooting issues related to algorithm optimization etc.. More information on our upcoming developments please stay tuned at our Motor Channel!