本論文主要探討魚座標轉換原理，經由計算與直觀二種方法得知：魚座標之水平與垂直座標變化量( )，分別與馬達的電流與轉矩漣波有直接的關係，故可由磁通魚形，得知諧波對馬達的影響。另一方面，若是適當地選擇魚座標之水平軸 的起始旋轉角度 ，則亦可將魚座標轉換技術應用於其他PWM，得到完整且對稱的磁通魚，進而計算其諧波指標 ，以判斷各種切換模態之優劣。
本文中，首度應用魚座標轉換技術於電壓空間向量脈寬調變(VSV-PWM)，並在固定切換頻率與定子電氣頻率的相同條件下，經由 及 的計算得知：VSV-PWM之性能優於S-PWM。同時，文中亦深入探討VSV-PWM之設計原理，並利用減少切換損失的原則，推論其參考電壓向量切換表，並以流程圖表示完整的設計步驟。
此外，吾人亦深入探討直接轉矩控制(DTC)理論，包括磁通與轉矩磁滯控制，並根據磁通行進方向與電壓向量方向一致的原則，推論其電壓向量切換表。本文亦將磁通磁滯控制，視為一種脈寬調變法則，並嘗試利用磁通魚形判斷其性能優劣。然而，此法係變頻切換，故磁通軌跡較無對稱性，其對應之磁通魚亦不對稱，但仍可用魚形判斷其性能優劣。
本論文亦歸納魚形法之切換模態的設計重點與精神，經由分析其優缺點，以瞭解魚形法與其他切換模態之差異。最後，將文中所述之切換模態作綜合性的比較，並藉由Matlab軟體模擬與實作，驗證理論之正確性。

The fish coordinate transformation is mainly investigated in this thesis. The detailed calculation and inspection insight reveal that the current and torque ripples are directly related to the variations of the fish coordinates of and , respectively. The harmonic effects on the motor can be thereby obtained by observing the shape of the flux fish. On the other hand, if the starting angle r in the fish coordinate transformation is chosen appropriately, the fish transformation technique can be applied to the various PWMs. The intact and symmetric flux fish can be obtained. It can be used to calculate the harmonic figure F and judge the merits of the various switching patterns.
In this thesis, the fish coordinate transformation is originally applied to the voltage-space vector pulsewidth modulation (VSV-PWM). On the basis of the same conditions of fixed switching and the electric frequency of the stator, it shows that the performance of VSV-PWM is superior to that of S-PWM from a viewpoint of the figure of the quality measure F and the total harmonic distortion THD. To reduce the switching losses, a switching table of voltage vector is derived for VSV-PWM. Its flowchart completely illustrates the design procedure.
In addition, the direct torque control theory is also reviewed in this thesis. It includes the flux and torque hysteresis controls. By virtue of the principle of alignment of the flux and voltage vectors of the stator, the vector switching table can be derived. The flux hysteresis control is treated as one kind of PWM in the thesis so that the shape of flux fish can be used to evaluate its figure of merit. Unfortunately, the symmetry of the flux fish can be not maintained due to the variable frequency switching.
The key point of the switching pattern of the fish method is included in this thesis. By analyzing the merits and faults, the differences among various switching patterns are revealed. In the end, comparison results verified by simulation and experiments are also presented.

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