摘要:針對傳統(tǒng)永磁同步電機滑??刂浦写嬖诘幕6墩翊蠹绊憫俣嚷膯栴},設(shè)計了一種新型趨近律,在傳統(tǒng)指數(shù)趨近律的基礎(chǔ)上加入可變比例系數(shù)并引入系統(tǒng)狀態(tài)變量和滑模面的冪次項,減小抖振的同時提高了趨近速率。隨后,為了避免引入轉(zhuǎn)速誤差的微分項,減小系統(tǒng)高頻抖振,采用積分滑模面,設(shè)計了永磁同步電機改進滑模速度控制器。針對控制策略中負載擾動波動會導致系統(tǒng)控制精度降低、抖振增大的問題,設(shè)計了一種基于新型飽和函數(shù)的擴張狀態(tài)觀測器估計負載擾動,并將擾動估計值前饋至改進滑模控制器中,進一步提高了系統(tǒng)的抗擾性能。數(shù)值仿真結(jié)果表明:所提出的控制策略可顯著提高電機動態(tài)性能和抗擾性。在電機受負載轉(zhuǎn)矩波動影響時,比PI控制電機超調(diào)量減小約23.1%,響應速度提高62.5%,比傳統(tǒng)滑模控制電機超調(diào)量減小約15.3%,響應速度提高50%。新型滑模趨近律還可以有效降低滑模抖振,與傳統(tǒng)滑模控制器相比,采用改進滑??刂破麟姍C抖振降低約50%。
關(guān)鍵詞:永磁同步電機;滑模控制;新型趨近律;擴張狀態(tài)觀測器;擾動前饋補償
中圖分類號:TM351 文獻標志碼:A
DOI:10.7652/xjtuxb202403019 文章編號:0253-987X(2024)03-0204-08
Improved Sliding Mode Control with Disturbance Rejection for Load Torque
Observation of Permanent Magnet Synchronous Motors
SHAO Baoling1,2, LIU Ling1,2, HU Mingyao1,2
(1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China;
2. School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China)
Abstract:To address issues like large chattering and slow response in traditional sliding mode control of permanent magnet synchronous motors (PMSMs), a new type of reaching law is designed. This approach incorporates a conventional exponential reaching law with an adaptable proportionality coefficient, system state variables, and the power term of the sliding mode surface to mitigate chattering while enhancing convergence speed. To avoid introducing differential terms of speed error and reduce high-frequency chattering in the system, an integral sliding mode surface is used to design an improved PMSM speed controller. To address the issue of reduced control accuracy and increased chattering in the control system caused by load disturbance fluctuations, a novel saturation function-based extended state observer (ESO) is devised. This ESO is utilized to estimate the load disturbance and the estimated disturbance value is fed forward to the improved sliding mode controller to further enhance the system’s disturbance rejection capability. The numerical simulation results demonstrate that the proposed control strategy substantially improves the dynamic performance and disturbance rejection of the motor. When the motor is affected by load torque fluctuations, compared to PI control, the proposed control strategy reduces overshoot by about 23.1% and increases response speed by 62.5%. Compared to traditional sliding mode control, the proposed control strategy reduces overshoot by about 15.3% and increases response speed by 50%. The new sliding mode reaching law can effectively reduce sliding mode chattering. Compared to traditional sliding mode controllers, the improved sliding mode controller reduces motor chattering by about 50%.
Keywords:permanent magnet synchronous motor; sliding mode control; new reaching law; extended state observer; disturbance rejection feedforward compensation
永磁同步電機(PMSM)由于體積小,可靠性高等特點,在電動汽車、軌道交通等新興領(lǐng)域得到了廣泛應用。這就要求對PMSM有高性能和高精度的控制,然而PMSM是一種高度非線性的系統(tǒng),其動態(tài)性能受到諸多因素的影響,傳統(tǒng)PI控制策略容易受內(nèi)部參數(shù)變化和外部負載擾動的影響,在很多場合不能滿足控制精度的要求[1-3]。因此,為了提高系統(tǒng)魯棒性,增強系統(tǒng)動態(tài)性能,諸多非線性控制方法被應用在PMSM調(diào)速系統(tǒng)中,包括滑模控制[4-13]、自適應控制[14-15]、預測控制[16-17]和模糊控制[18]等。
滑模控制具有魯棒性強、響應迅速等特點,越來越多的研究采用滑模變結(jié)構(gòu)理論設(shè)計PMSM控制系統(tǒng),然而由于滑模固有的抖振問題,使得其應用于控制系統(tǒng)時會給控制系統(tǒng)帶來高頻抖振。因此,目前針對滑模變結(jié)構(gòu)控制的研究主要集中在降低滑模抖振上。文獻[19]設(shè)計了一種采用可變邊界層的非奇異快速終端滑模面,在不影響跟蹤精度的前提下降低了系統(tǒng)抖振,但是沒有考慮外部擾動變化對控制系統(tǒng)的影響,導致系統(tǒng)魯棒性較差。文獻[20]設(shè)計了一種負載轉(zhuǎn)矩擴展滑模觀測器,將觀測到的負載轉(zhuǎn)矩進行前饋補償,提高了滑模控制系統(tǒng)的抗擾性,但由于滑??刂破髦写嬖谵D(zhuǎn)速的微分項,導致系統(tǒng)受高頻噪聲干擾較大,存在較大的抖振現(xiàn)象。文獻[21-22]采用積分滑模面設(shè)計滑??刂破鳎苊饬宿D(zhuǎn)速微分對控制系統(tǒng)性能的影響,減小了系統(tǒng)穩(wěn)態(tài)誤差。文獻[23]設(shè)計了一種自適應快速終端滑模面,并采用Luenberger觀測器估計系統(tǒng)擾動量的大小,將擾動估計值前饋至滑模控制器,增強了系統(tǒng)抗擾能力,減小了抖振現(xiàn)象。文獻[24]設(shè)計了一種模糊滑模速度控制器,降低了控制系統(tǒng)對電機參數(shù)的依賴,并在一定程度上減小了系統(tǒng)抖振。
在上述文獻的基礎(chǔ)上,為了進一步提高PMSM控制系統(tǒng)性能,減小滑模抖振,本文設(shè)計了一種新型滑模趨近律,在傳統(tǒng)指數(shù)趨近律中結(jié)合可變比例系數(shù),并加入系統(tǒng)狀態(tài)變量和滑模面的冪次項, 減小控制系統(tǒng)抖振的同時增大了系統(tǒng)狀態(tài)趨近滑模面的速度。采用積分滑模面設(shè)計了滑模速度控制器,減小穩(wěn)態(tài)誤差,提升控制系統(tǒng)精度。此外,為了減小負載擾動對系統(tǒng)控制性能的影響,設(shè)計了基于新型飽和函數(shù)的擴張狀態(tài)觀測器(ESO)觀測擾動變化,將觀測器前饋至滑??刂破?,增強了系統(tǒng)抗擾性,并對設(shè)計的滑模控制器進行穩(wěn)定性證明。仿真結(jié)果表明,本文提出的控制策略響應速度快、系統(tǒng)抖振小,并且可以有效抑制負載擾動對系統(tǒng)的影響。
1 新型趨近律設(shè)計
針對傳統(tǒng)滑??刂品椒憫俣嚷?、抖振大等問題,可以通過設(shè)計趨近律的方法增大系統(tǒng)響應速度,減小滑模抖振。常用的指數(shù)趨近律為
式中:k、ε均為控制器參數(shù);-εsgn(s)代表等速趨近項;-ks代表指數(shù)趨近項;s為滑模面。當系統(tǒng)狀態(tài)遠離滑模面時,指數(shù)項發(fā)揮主要作用,以提高趨近速度;而當系統(tǒng)狀態(tài)接近滑模面時,等速項對趨近速度的影響較為顯著,這在一定程度上減小了抖振。
由于含指數(shù)趨近項的趨近律不能保證有限時間到達滑模面,因此需要結(jié)合等速趨近項。但是,系統(tǒng)到達滑模面的速度由k決定,增加系統(tǒng)響應速度必然會增大滑模抖振。在等速趨近項中增大的ε可以加快系統(tǒng)到達滑模面的時間,增強系統(tǒng)動態(tài)性能,但是ε過大又會導致系統(tǒng)抖振增加。
在傳統(tǒng)指數(shù)趨近律的基礎(chǔ)上,設(shè)計了一種新型趨近律如下
如果系統(tǒng)狀態(tài)離滑模面較遠,即[JB(|]s[JB)|]較大,則(1-ε1)e-δ[JB(|]s[JB)|]趨于0,且sgn([JB(|]s[JB)|]-1)=1,此時系統(tǒng)狀態(tài)以變系數(shù)趨近律k1[JB(|]s[JB)|]a/ε1和指數(shù)趨近律k2[JB(|]s[JB)|]bs到達滑模面。隨著系統(tǒng)狀態(tài)靠近滑模面,[JB(|]s[JB)|]減小,ε1+(1-ε1)e-δ[JB(|]s[JB)|]趨近于1,且k2[JB(|]s[JB)|]bsgn([JB(|]s[JB)|]-1)趨近于k2,滑模面的趨近律可簡化為-k1sgn(s)-k2s。因此,新型趨近律的設(shè)計可以在遠離滑模面時加快系統(tǒng)的收斂速度,在靠近滑模面時降低收斂速度,減小抖振,在增大系統(tǒng)響應速度的同時減小系統(tǒng)抖振。
2 基于新型趨近律的滑??刂破?/p>
2.1 永磁同步電機數(shù)學模型
為簡化分析,采取如下假設(shè):忽略磁路飽和;忽略磁滯與渦流損耗;轉(zhuǎn)子上無阻尼繞組。則PMSM在d-q-o旋轉(zhuǎn)坐標系下的定子電壓方程為
式中:ud、uq分別為定子電壓在d、q軸上的分量;id、iq分別為定子電流在d、q軸上的分量;Ld、 Lq為電機的d、q軸電感;ω為電角速度;ψf為轉(zhuǎn)子磁鏈。
對于表貼式永磁同步電機,電磁轉(zhuǎn)矩方程為
式中:Te為電機電磁轉(zhuǎn)矩;np為電機極對數(shù);TL為負載轉(zhuǎn)矩;J為轉(zhuǎn)動慣量。
2.2 擴張狀態(tài)觀測器設(shè)計
電機實際運行時,負載擾動和電機參數(shù)等都會隨時間變化,為了保證系統(tǒng)穩(wěn)定,滑模控制的開關(guān)增益需要給定一個大于擾動上界的值。在擾動未知的情況下,滑模增益一般要選取一個較大的值,這會造成系統(tǒng)的抖振增大。為了減小抖振,提出利用擴張狀態(tài)觀測器觀測電機總擾動,并將觀測值前饋至滑模控制器,考慮參數(shù)不確定性影響的情況,可將永磁同步電機的運動方程表示為
3 數(shù)值仿真分析
本節(jié)通過仿真驗證所提出的控制策略的有效性。仿真所用PMSM參數(shù)如表1所示,采樣頻率為10kHz。為確保仿真結(jié)果對比的公平性,首先調(diào)節(jié)基于指數(shù)趨近律的滑模控制器性能至最佳,控制參數(shù)為ε=23,k=5。隨后控制改進滑??刂破鲄?shù)k1=23,k2=5,調(diào)節(jié)其余參數(shù)確保改進滑模控制器性能至最佳,所用參數(shù)如表2所示。PI控制器參數(shù)為kp=0.07,ki=31.42。
電機起動時轉(zhuǎn)速給定為1000r/min,在第1s轉(zhuǎn)速給定變?yōu)?500r/min。電機負載轉(zhuǎn)矩在第3s階躍增加1N·m,在第5s階躍減小1N·m。PI控制器仿真結(jié)果如圖2所示,基于等速趨近律的滑??刂破鞣抡娼Y(jié)果如圖3所示,基于新型趨近律的滑模控制器仿真結(jié)果如圖4所示。
由圖2可知,采用傳統(tǒng)PI控制,電機存在響應速度慢、抗擾性較差等問題。電機轉(zhuǎn)速由1000r/min升至1500r/min時,存在約40r/min的超調(diào)量,并且電機轉(zhuǎn)速經(jīng)過0.07s才趨于穩(wěn)定。電機突增負載時,電機轉(zhuǎn)速下降了65r/min;電機突卸負載時,電機轉(zhuǎn)速增加64r/min,經(jīng)過0.08s電機轉(zhuǎn)速趨于穩(wěn)定。
由圖3可知,采用基于指數(shù)趨近律的傳統(tǒng)滑??刂茣r,電機響應速度和抗擾能力都得到一定提升。電機轉(zhuǎn)速由1000r/min升至1500r/min時,電機轉(zhuǎn)速經(jīng)過0.06s達到給定轉(zhuǎn)速;電機突增負載時,電機轉(zhuǎn)速下降59r/min,電機突卸負載時,電機轉(zhuǎn)速增加58r/min,經(jīng)過0.06s電機轉(zhuǎn)速趨于穩(wěn)定。
由圖4可知,采用基于新型趨近律的滑模控制時,電機響應速度和抗擾能力得到明顯提升。電機轉(zhuǎn)速由1000r/min升至1500r/min時,電機轉(zhuǎn)速經(jīng)過0.02s達到給定轉(zhuǎn)速,比PI控制響應速度提高了71.4%,比傳統(tǒng)滑??刂祈憫俣忍岣?6.6%。電機突增負載時,電機轉(zhuǎn)速下降了50r/min,電機突卸負載時,電機轉(zhuǎn)速增加了51r/min,經(jīng)過0.03s電機轉(zhuǎn)速即趨于穩(wěn)定,比PI控制電機超調(diào)量減小約23.1%,響應速度提高62.5%,比傳統(tǒng)滑模控制電機超調(diào)量減小約15.3%,響應速度提高50%。
圖5為基于擴張狀態(tài)觀測器的負載轉(zhuǎn)矩估計結(jié)果。由圖5可知,觀測器可以較為準確地估計負載轉(zhuǎn)矩,在電機突增和突卸負載時也可以快速跟蹤負載轉(zhuǎn)矩的變化,響應速度較快。
圖6為分別采用傳統(tǒng)滑??刂破骱突谛滦挖吔傻幕?刂破麟姍C穩(wěn)定運行時轉(zhuǎn)速抖振情況??梢钥吹剑捎眯滦突?刂破骺梢杂行Ы档投墩?,相比傳統(tǒng)滑??刂破?,電機抖振降低約50%。
4 結(jié) 論
本文提出了一種基于負載轉(zhuǎn)矩觀測的永磁同步電機改進滑模控制策略。針對傳統(tǒng)滑??刂浦写嬖诘幕6墩窦绊憫俣嚷膯栴},在傳統(tǒng)指數(shù)趨近律的基礎(chǔ)上加入可變比例系數(shù)并引入系統(tǒng)狀態(tài)變量和滑模面的冪次項,設(shè)計了一種新型趨近律;結(jié)合擴張狀態(tài)觀測器實時估計負載轉(zhuǎn)矩,將負載轉(zhuǎn)矩的估計值前饋至滑??刂破?,提高了系統(tǒng)的抗擾性。通過數(shù)值仿真分析,將本文提出的控制策略與傳統(tǒng)PI控制、基于傳統(tǒng)指數(shù)趨近律的滑??刂七M行了對比,結(jié)果表明,本文所提出的控制策略可以有效提高電機動態(tài)性能和抗擾性能,電機負載轉(zhuǎn)矩波動時轉(zhuǎn)速恢復時間短,超調(diào)量小,電機穩(wěn)定運行時也可以有效削弱系統(tǒng)抖振。
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(編輯 杜秀杰)
收稿日期:2023-09-15。
作者簡介:邵保領(lǐng)(1999—),男,碩士生;劉凌(通信作者),男,副教授,博士生導師。
基金項目:國家自然科學基金資助項目(51977173)。
網(wǎng)絡(luò)出版時間:2023-10-26網(wǎng)絡(luò)出版地址:https:∥link.cnki.net/urlid/61.1069.T.20231026.0925.002