【正文】 der to form a dclink that feeds an inverter. Balanced threephase voltages are supplied to the load by this inverter. Since the inverter also determines load frequency, it is not necessary to operate the generator at constant speed corresponding to 60 Hz. In order to make engine operation as efficient as possible, speed is varied from 1800 rpm to 4000 rpm according to a loadversusspeed relationship considered optimal for the engine. Such variable speed operation affects generator design in several ways, of which the most important for our study is the effect it has on the value of main generator’s synchronous inductance. With standard generator design, at minimum speed a relatively large main generator’s field current would be required in order to achieve the rated generator output voltage. That would result in large exciter’s armature currents, and overheating of the exciter. The minimum amount of cooling (due to minimum speed) would make this problem even more serious. In order to avoid this, generator designers increased the number of turns of the main generator’s armature windings. That resulted in a smaller field current required to obtain the rated output voltage but, at the same time, it significantly increased main generator’s synchronous inductance. A peculiarity of the system shown in Fig. is the fact that both synchronous machines, the exciter and main generator, have electronic load: they feed reactive dc loads through diode rectifiers. If a synchronous machine were an ideal voltage source, Fig. would represent its simplified circuit diagram with a diode bridge and a dc current source load. It is a textbook example of how nonlinear, switching elements (diodes) cause nonsinusoidal ac waveforms [1]. In Fig. , va, vb and vc are sinusoidal voltages with amplitude Vp and a phase shift of 120o one with respect to another. Idc is a constant dc current representing dc load. Average value of the dc voltage at the rectifier’s output can be calculated asFig. . Ideal threephase voltage source feeding a dc current source load through a diode rectifier.Fig. . Ac waveforms of the system shown in Fig. .Fig. shows qualitative waveforms of phase voltage va and phase current ia. It can be seen that, due to diode rectification and currentsource dc load, the phase current has a quasisquare waveform. First harmonic of ia, ia1, is also shown. Its amplitude can be calculated asIt is important to notice in Fig. that voltage is in phase with current’s first harmonic. Therefore, from the point of view of the ac input’s fundamental voltage and 4 current harmonics, an ideal diode rectifier with a current source dc load behaves like a nonlinear resistor.Fig. . Nonideal voltage source feeding a current source dc load through a diode rectifier.The situation is somewhat more plicated if ac side’s parasitic inductances Ll are considered [1]. These inductances normally represent transformer or power line leakage inductance, and need to be placed in series with ideal voltage sources va, vb and vc, as shown in Fig. . They cause nonideal operation of the diode bridge, . they cause diode mutations to be noninstantaneous。 the time required for mutation is usually expressed in terms of mutation angle u, which is a function of parasitic input inductance Ll, line frequency ω and output current Idc [1]:Noninstantaneous diode mutations cause distortion in diode bridge input voltage waveforms, vAB, vBC and vCA, while edges of the current waveform have some finite slope. Also, the average value of the output dc voltage is somewhat reduced pared to the ideal case, and it can be expressed as [1]:It needs to be understood that () and () describe an ideal operation of thediode rectifier in an average sense: they express average dc output voltage by means ofinput ac peak voltage, and fundamental harmonic of input ac current by means of theoutput dc current. These expressions do not contain any information about the voltage ripple at the dc side and the current’s higher harmonics at the ac side. A synchronous generator is never an ideal voltage source, and it is even less so if it is characterized by a large value of synchronous inductance. If it is connected to a diode rectifier, inductance Ll from Fig. is of the order of magnitude of the generator’s synchronous inductance. Therefore, it can be expected that the exciter’s and the main generator’s ac terminal voltage and current waveforms will be heavily distorted [2][7]. Fig. shows measured waveforms of the system from Fig. and can serve as an example of such distortion. It can be seen that the main generator’s linetoline voltage is a quasisquare wave, and the current is also far from being sinusoidal.這項工作是出于需要研究動力學與控制設(shè)計的系統(tǒng)，其框圖如圖 。這是一個150千瓦的發(fā)電機組，其中天然氣發(fā)動機驅(qū)動的同步發(fā)電機，在整個這段文字，也可稱為主發(fā)電機與逆變器輸出。通過一個單獨的，較小的同步機的勵磁主發(fā)電機提供勵磁電壓。勵磁機的構(gòu)造的定子和電樞繞組在轉(zhuǎn)子上的繞組字段。，使得能夠糾正勵磁機的電樞交流電壓由旋轉(zhuǎn)的二極管橋，連接整流器的輸出直接到主發(fā)電機繞組的字段。 研究系統(tǒng)框圖主發(fā)電機的輸出整流由另一個二極管電橋，以形成一個直流環(huán)節(jié)的逆變器饋送。平衡三相電壓，由該逆變器提供給負載。由于逆變器也確定負載的頻率，這是沒有必要的操作以恒定的速度對應(yīng)于60赫茲的發(fā)電機。為了使盡可能高效的發(fā)動機運轉(zhuǎn)速度的變化從1800 rpm至4000 rpm認為是最優(yōu)的發(fā)動機的負荷與速度的關(guān)系。這種變速操作在幾個方面影響發(fā)生器的設(shè)計，這在我們的研究中最重要的是它具有主發(fā)電機的同步電感的值的效果。發(fā)生器的設(shè)計標準，在最低轉(zhuǎn)速需要一個比較大的主發(fā)電機的勵磁電流，以達到額定發(fā)電機輸出電壓。這會導致大勵磁機的電樞電流，勵磁過熱。最低的制冷量（由于最低速度），使這個問題更為嚴重。為了避免這種情況，發(fā)電機設(shè)計師主發(fā)電機的電樞繞組的匝數(shù)增加了許多。這導致了一個更小的字段取得額定輸出電壓所需的電流，但在同一時間，它顯著地增加主發(fā)電機的同步電感。圖中所示的系統(tǒng)的另一特。 ，電子負載的事實，即：它們喂飽反應(yīng)通過二極管整流器的直流負載。如果是一個同步機是一個理想的電壓源，圖 。這是一個非線性的，導致開關(guān)元件（二極管）的典型例子非正弦波形的交流波形[1]。，VB和VC正弦電壓幅值VP和120。的一相移相對于另一些。 Idc是一個恒定的直流電流，直流負載。整流器的輸出端的直流電壓的平均值可以計算為 (11) 非常適于通過一個二極管整流的三相電壓源供給的直流電流源負載。 系統(tǒng)中ac波形?？梢钥闯龅氖?，由于二極管整流和電流源的直流負載，相電流有一個準方波形。 IA，IA1，第一高次諧波也同時顯示?？梢杂嬎愠銎湔穹鶠? （12）重要的是要注意到在圖 ，電壓與電流的一次諧波相位。因此，從交流輸入的基波電壓和電流諧波與電流源的直流負載，一個理想的二極管整流器的點的行為像一個非線性電阻。 非理想電壓源供給的電流源通過一個二極管整流的直流負載。情況較為復雜，如果AC側(cè)的寄生電感會被認為是1。這些電感通常指變壓器或電力線的漏感，需要被放置在理想的電壓源的串聯(lián)與VA，VB和Vc，即他們導致二極管減刑的非瞬時換向所需的時間通常是在換向角U，這是一個功能寄生輸入電感LL，線路頻率ω表示和輸出電流Idc[1]：