IC660BBD023汽輪機(jī)模塊DFIG的動(dòng)態(tài)控制是通過功率變流器來實(shí)現(xiàn)的,該變流器使電網(wǎng)的電氣頻率與轉(zhuǎn)子的機(jī)械轉(zhuǎn)速解藕,從而實(shí)現(xiàn)變速運(yùn)行(Ekanauyake 等,2003)。模擬控制方案為:轉(zhuǎn)子側(cè)變流器提供轉(zhuǎn)矩控制以及端電壓控制,或者提供整個(gè)系統(tǒng)額功率因數(shù)(PF)控制;而電網(wǎng)側(cè)變流器控制直流鏈接的電壓。在有些應(yīng)用場(chǎng)合,網(wǎng)側(cè)變流器被用來提供無功功率??刂品桨改繕?biāo)是從風(fēng)力中捕獲最大功率??刂品桨钢校W(wǎng)側(cè)變流器用來維持直流母線電壓恒定,并為轉(zhuǎn)子與交流系統(tǒng)之間的功率交換提供通路,且要求這種功率交換以單位功率因數(shù)進(jìn)行(Pena等,1996; Holdsworth 等,2003)。
IC660BBD023汽輪機(jī)模塊受功率變流器容量的限制,在任意風(fēng)速下保持最大風(fēng)能是不現(xiàn)實(shí)的。對(duì)于很低風(fēng)速,要求風(fēng)機(jī)運(yùn)行在幾乎恒定的轉(zhuǎn)速下(A-B段)。旋轉(zhuǎn)速度同時(shí)還經(jīng)常受到空氣動(dòng)力噪聲的限制,在這些點(diǎn)上,控制器允許轉(zhuǎn)矩在轉(zhuǎn)速幾乎不變的條件下增加(C-D段),直至到達(dá)額定轉(zhuǎn)矩。如果風(fēng)速進(jìn)一步增大到超出風(fēng)力機(jī)的額定轉(zhuǎn)矩,控制器將控制風(fēng)機(jī)運(yùn)行在D-E段,保持電磁轉(zhuǎn)矩恒定。當(dāng)系統(tǒng)運(yùn)行到E點(diǎn)后,槳距調(diào)節(jié)將取代轉(zhuǎn)矩控制來限制氣動(dòng)輸入功率。對(duì)于非常高的風(fēng)速,槳距控制將調(diào)節(jié)輸入功率直至達(dá)到停機(jī)風(fēng)速。
2.3風(fēng)力機(jī)仿真模型
風(fēng)力機(jī)是指風(fēng)機(jī)主軸前輪轂系統(tǒng),物理結(jié)構(gòu)包括輪轂、槳葉、變槳系統(tǒng)。為了便于控制研究,風(fēng)力機(jī)模型基于穩(wěn)態(tài)建立,并且假定驅(qū)動(dòng)鏈有足夠硬度,系統(tǒng)摩擦系數(shù)和轉(zhuǎn)動(dòng)慣量計(jì)入了整個(gè)機(jī)組驅(qū)動(dòng)鏈輸出功率可以按下式進(jìn)行計(jì)算:2.4全功率測(cè)試平臺(tái) 以全功率測(cè)試為設(shè)計(jì)理念,采用大功率變頻器拖動(dòng)異步電機(jī)方案來模擬風(fēng)機(jī)輪轂、葉片系統(tǒng),拖動(dòng)整個(gè)風(fēng)機(jī)機(jī)艙,實(shí)現(xiàn)整機(jī)全功率并網(wǎng)發(fā)電過程和試驗(yàn)數(shù)據(jù)存儲(chǔ)、輸出。 由于定位為整機(jī)測(cè)試,測(cè)試臺(tái)需要對(duì)整個(gè)機(jī)艙部分進(jìn)行車間地面測(cè)試,如果變流器設(shè)計(jì)不在機(jī)艙,則需要在測(cè)試臺(tái)旁邊工位安放變流器。測(cè)試臺(tái)采用變頻器拖動(dòng)異步電機(jī)加減速機(jī)方案來模擬實(shí)現(xiàn)風(fēng)動(dòng)力,通過變頻器轉(zhuǎn)矩和轉(zhuǎn)速控制異步電機(jī)來模擬實(shí)現(xiàn)風(fēng)力機(jī)特性,完成在不同風(fēng)況下風(fēng)力機(jī)轉(zhuǎn)速、轉(zhuǎn)矩、功率輸出模擬。貝加萊的X20系列控制器以及I/O的平均無故障時(shí)間(MTBF)達(dá)到了50萬小時(shí)。所有產(chǎn)品均通過了苛刻的歐洲CE、UL等認(rèn)證測(cè)試,并滿足了鐵道部電氣系統(tǒng)的A級(jí)EMC測(cè)試要求。此外,為了進(jìn)一步提高系統(tǒng)的可靠性能,貝加萊還推出了全對(duì)稱式的冗余方案。如 圖2。兩臺(tái)完全一樣的CPU同時(shí)運(yùn)行著一模一樣的程序,并掛接相同的I/O以及通訊模塊。在運(yùn)行期間只有一臺(tái)CPU是主站(擁有控制權(quán)),而另一臺(tái)處于熱備狀態(tài)(無控制權(quán))。
Therefore, reducing radial cutting force is an important principle to reduce radial runout. The following methods can be used to reduce radial runout:
1. Use sharp toolsSelect a larger rake angle to make the tool sharper to reduce cutting force and vibration. Selecting a larger tool relief angle can reduce the friction between the main relief surface of the tool and the elastic recovery layer of the transition surface of the workpiece, so as to reduce the vibration. However, the front angle and back angle of the tool should not be too large, otherwise the strength and heat dissipation area of the tool will be insufficient. Therefore, different rake angles and rake angles should be selected according to specific conditions. During rough machining, the rake angle can be smaller. However, during finishing machining, for the sake of reducing the radial runout of the tool, the rake angle and rake angle should be larger to make the tool sharper.
2. Use tools with high strength
There are mainly two ways to increase the strength of the tool. First, the diameter of the tool bar can be increased. Under the same radial cutting force, the diameter of the tool bar can be increased by