楊旭紅,陳 陽(yáng),賈 巍,方劍峰,羅 新,高子軒
基于RBF神經(jīng)網(wǎng)絡(luò)的電壓外環(huán)滑??刂频腣ienna整流器
楊旭紅1,陳 陽(yáng)1,賈 巍2,方劍峰1,羅 新1,高子軒1
(1.上海電力大學(xué)自動(dòng)化工程學(xué)院,上海 200090;2.上海太陽(yáng)能工程技術(shù)研究中心,上海 200241)
以Vienna整流器為研究對(duì)象,針對(duì)其傳統(tǒng)電壓外環(huán)滑模變結(jié)構(gòu)控制不變性和對(duì)系統(tǒng)參數(shù)擾動(dòng)敏感的問(wèn)題,分析了以逼近率為基礎(chǔ)的滑模變結(jié)構(gòu)控制算法,提出了一種基于RBF神經(jīng)網(wǎng)絡(luò)的自適應(yīng)電壓外環(huán)滑模控制算法。該控制算法通過(guò)將RBF神經(jīng)網(wǎng)絡(luò)與滑模控制算法有效結(jié)合,同時(shí)將中點(diǎn)電位平衡控制加入到RBF神經(jīng)網(wǎng)絡(luò)自適應(yīng)電壓外環(huán)滑模控制算法的設(shè)計(jì)中,使用RBF神經(jīng)網(wǎng)絡(luò)對(duì)電壓外環(huán)非線性系統(tǒng)進(jìn)行自適應(yīng)逼近,能夠有效降低切換增益,削弱抖振,增強(qiáng)系統(tǒng)的抗干擾能力。最后,通過(guò)仿真分析與實(shí)驗(yàn)測(cè)試驗(yàn)證所提控制算法的有效性。將所提出的控制算法與傳統(tǒng)滑??刂扑惴?、PI控制算法進(jìn)行比較,結(jié)果表明采用這種電壓外環(huán)控制算法能夠?qū)χ绷鬏敵鲭妷耗繕?biāo)值進(jìn)行快速跟蹤,平衡中點(diǎn)電位,改善了系統(tǒng)的動(dòng)靜態(tài)性能,提升了其抗干擾能力。
Vienna整流器;電壓外環(huán);滑??刂疲悔吔?;RBF神經(jīng)網(wǎng)絡(luò)
Vienna整流器以其獨(dú)特的優(yōu)勢(shì)受到越來(lái)越多的關(guān)注和應(yīng)用。由于Vienna整流器的單向潮流特性,主要用于中、大功率場(chǎng)合的單向整流或兩級(jí)變流器的前級(jí)升壓整流模塊。目前,典型的應(yīng)用場(chǎng)合包括航空電源、直流不間斷電源(UPS)、直流充電樁等[1-3]。
目前,對(duì)Vienna整流器的研究主要集中在建立與分析數(shù)學(xué)模型、優(yōu)化脈沖寬度調(diào)制技術(shù)和優(yōu)化設(shè)計(jì)環(huán)路控制策略三方面。文獻(xiàn)[1-2]研究了Vienna整流器一些典型的數(shù)學(xué)模型;文獻(xiàn)[3-9]對(duì)其調(diào)制算法進(jìn)行了整體優(yōu)化設(shè)計(jì)。對(duì)于Vienna整流器的外環(huán)電壓多采用PI控制,但系統(tǒng)存在由輸出電壓誤差線性求和造成的輸出電壓超調(diào)大以及由積分環(huán)節(jié)飽和引起的動(dòng)態(tài)響應(yīng)速度慢等缺點(diǎn),因此有必要從電壓外環(huán)著手進(jìn)行控制系統(tǒng)的優(yōu)化設(shè)計(jì)。文獻(xiàn)[10]使用ADRC(自抗擾控制)來(lái)設(shè)計(jì)電壓外環(huán)控制器,在一定程度上解決了輸出電壓快速性與超調(diào)之間的矛盾;文獻(xiàn)[11-12]采用滑??刂圃O(shè)計(jì)電壓外環(huán)控制器,可以來(lái)解決Vienna整流器非線性系統(tǒng)控制問(wèn)題,輸出電壓快速性與超調(diào)之間的矛盾也得到了進(jìn)一步解決。文獻(xiàn)[13]提出將模糊算法應(yīng)用到滑??刂破髦?,直流側(cè)輸出的電壓性能得到進(jìn)一步優(yōu)化,電流的THD也得到了優(yōu)化。以上電壓外環(huán)控制策略存在的共同缺點(diǎn)是都要另外用PI控制器來(lái)進(jìn)行中點(diǎn)電位的控制[14-15]。
本文將RBF神經(jīng)網(wǎng)絡(luò)[16-17]與Vienna整流器的電壓環(huán)路滑??刂破飨嘟Y(jié)合,設(shè)計(jì)出了基于RBF神經(jīng)網(wǎng)絡(luò)的電壓環(huán)自適應(yīng)滑模控制器。RBF神經(jīng)網(wǎng)絡(luò)的收斂速率快,結(jié)構(gòu)簡(jiǎn)單,具有最佳近似性并非常適用于實(shí)時(shí)的在線控制。將RBF神經(jīng)網(wǎng)絡(luò)和滑??刂平Y(jié)合起來(lái),利用RBF神經(jīng)網(wǎng)絡(luò)逼近電壓外環(huán)滑模的非線性函數(shù),有效減小啟動(dòng)器增益和抖動(dòng)。同時(shí),將中點(diǎn)電位平衡控制與RBF神經(jīng)網(wǎng)絡(luò)自適應(yīng)滑??刂埔黄鸺尤耄纬闪诵碌碾妷和猸h(huán)控制算法,即RBF神經(jīng)網(wǎng)絡(luò)自適應(yīng)控制算法,不僅節(jié)省了資源,而且改善了控制性能。最后,利用Simulink仿真和實(shí)驗(yàn)驗(yàn)證與其他控制器進(jìn)行了對(duì)比分析,結(jié)果表明新型控制算法能夠?qū)χ绷鬏敵鲭妷耗繕?biāo)值進(jìn)行快速跟蹤,平衡中點(diǎn)電位,提高了系統(tǒng)的動(dòng)態(tài)性和魯棒性,具有更大的優(yōu)勢(shì)。
圖1 Vienna整流器拓?fù)浣Y(jié)構(gòu)圖
式中:
對(duì)系統(tǒng)輸出求導(dǎo),可得
為了減弱滑模變結(jié)構(gòu)的抖動(dòng),設(shè)計(jì)趨近率形式如式(8)。
對(duì)式(7)求導(dǎo),可得
對(duì)式(9)化簡(jiǎn)可得
控制系統(tǒng)滿足式(11)。
求解式(11)可得
定理1:
由式(13)可得該控制系統(tǒng)滿足存在性和可達(dá)性的條件,定理1得證。
取性能指標(biāo)函數(shù)為
采用最速下降法對(duì)神經(jīng)網(wǎng)絡(luò)進(jìn)行學(xué)習(xí)和在線調(diào)整,隱含層的基函數(shù)通常選擇如式(16)所示的高斯基函數(shù)。
選用Matlab仿真軟件對(duì)所設(shè)計(jì)網(wǎng)絡(luò)進(jìn)行訓(xùn)練。使用同一樣本對(duì)隱含層神經(jīng)元個(gè)數(shù)從6到16的網(wǎng)絡(luò)進(jìn)行訓(xùn)練并比較結(jié)果,如表1所示。
表1 不同數(shù)量隱含層神經(jīng)元節(jié)點(diǎn)的神經(jīng)網(wǎng)絡(luò)測(cè)試結(jié)果
根據(jù)表1實(shí)驗(yàn)效果,的取值為15。
圖3 神經(jīng)網(wǎng)絡(luò)模型結(jié)構(gòu)圖
由圖3可知,其輸出表達(dá)式為
圖3所示網(wǎng)絡(luò)的理想輸出值記為
式(27)是連接權(quán)值的魯棒更新算法。
在設(shè)計(jì)Lyapunov函數(shù)時(shí)考慮包含滑模面與魯棒自適應(yīng)率,具體表達(dá)式為
對(duì)式(28)求導(dǎo)得
式中:
所以該控制系統(tǒng)滿足存在性和可達(dá)性的條件[26]。
因此,基于RBF神經(jīng)網(wǎng)絡(luò)自適應(yīng)控制器的設(shè)計(jì)結(jié)構(gòu)如圖4所示。
圖4 基于RBF神經(jīng)網(wǎng)絡(luò)自適應(yīng)控制器
Fig. 4 Adaptive controller based on improved RBF neural network
綜上所述,得到如圖5所示的Vienna整流器控制原理框圖。
圖5 三相Vienna整流器控制框圖
通過(guò)表2(除控制器部分)里的仿真參數(shù)來(lái)驗(yàn)證控制算法的有效性。
表2 仿真參數(shù)
則式(32)可寫(xiě)為
綜合考慮成本、裝置體積以及性能指標(biāo),本文選取的電感量為3.5 mH。
圖6 直流側(cè)輸出端電壓波形
圖7 交流輸入端a相電壓、電流波形
圖8 有功功率、無(wú)功功率波形
圖9 負(fù)載突變時(shí)a相電流頻譜
圖10 負(fù)載穩(wěn)定后a相電流頻譜
圖11 負(fù)載突變時(shí)兩種控制算法動(dòng)態(tài)仿真分析
從表3可以看出,基于雙閉環(huán)PI控制算法直流電壓輸出曲線的超調(diào)量和調(diào)節(jié)時(shí)間最大,分別達(dá)到46.625%和0.033 s(一個(gè)半電網(wǎng)周期),同時(shí)輸入電流的THD也比較大,中點(diǎn)平衡特性比較差。當(dāng)運(yùn)用滑??刂茖?duì)電壓外環(huán)控制算法進(jìn)行改進(jìn)時(shí),系統(tǒng)直流輸出曲線的超調(diào)量降低了36%,但是系統(tǒng)的響應(yīng)速度降低了,上升時(shí)間從0.003 s增加到0.009 s(半個(gè)電網(wǎng)周期),此時(shí)調(diào)節(jié)時(shí)間也變小了;輸入端電流的THD也減小了,中點(diǎn)電位平衡能力得到提升,系統(tǒng)的有功功率變化比較穩(wěn)定,無(wú)功功率基本穩(wěn)定在零,不會(huì)出現(xiàn)負(fù)值,傳統(tǒng)的電壓外環(huán)滑模控制算法對(duì)系統(tǒng)控制性能的提升起到了較大的作用。
圖12 雙閉環(huán)PI控制
圖13 新控制算法
圖14 反饋線性化+滑??刂?/p>
圖15 新控制算法
表3 控制性能參數(shù)對(duì)比
運(yùn)用RBF神經(jīng)網(wǎng)絡(luò)對(duì)傳統(tǒng)的電壓外環(huán)滑??刂七M(jìn)行改進(jìn),優(yōu)化成一種新型的外環(huán)電壓控制算法。超調(diào)量、上升時(shí)間、調(diào)節(jié)時(shí)間等動(dòng)靜態(tài)性能都得到了進(jìn)一步的提升,運(yùn)用這種電壓外環(huán)控制算法對(duì)電壓外環(huán)進(jìn)行控制時(shí),直流輸出曲線的超調(diào)量變?yōu)?.625%,上升時(shí)間和調(diào)節(jié)時(shí)間也得到了進(jìn)一步的減小,分別變?yōu)?.003 s和0.004 s;輸入電流THD在負(fù)載啟動(dòng)后和穩(wěn)定時(shí)分別為3.81%和1.73%,電流畸變小了。
為驗(yàn)證本文所提出的改進(jìn)滑模電壓外環(huán)控制策略的有效性,搭建了如圖16所示的Vienna整流器實(shí)驗(yàn)平臺(tái)。實(shí)驗(yàn)參數(shù)依然如表2所示??刂破鞑捎玫轮輧x器TMS320F2812,數(shù)字信號(hào)處理器可通過(guò)RT-LAB的模擬量輸入輸出通道與下位機(jī)通信實(shí)現(xiàn)閉環(huán)控制。
圖16 Vienna整流器實(shí)驗(yàn)平臺(tái)
圖17 反饋線性化+滑??刂?/p>
圖18 新控制算法
表4 不同控制算法執(zhí)行時(shí)間對(duì)比
本文提出了一種新型基于反饋線性化電流內(nèi)環(huán)和基于RBF神經(jīng)網(wǎng)絡(luò)的電壓外環(huán)三相三電平Vienna整流器混合控制策略。與傳統(tǒng)的反饋線性化加滑?;旌峡刂葡啾?,該控制算法綜合考慮了直流電壓、中點(diǎn)電位平衡和輸入側(cè)電流3個(gè)控制目標(biāo),使系統(tǒng)的靜動(dòng)態(tài)性能得到了進(jìn)一步提升。用Simulink搭建仿真模型,與雙PI控制和傳統(tǒng)的混合控制進(jìn)行性能對(duì)比,并且經(jīng)過(guò)實(shí)驗(yàn)測(cè)試驗(yàn)證,結(jié)果表明:采用新型混合控制算法,在系統(tǒng)啟動(dòng)和負(fù)載突變的時(shí)候既提升了系統(tǒng)響應(yīng)速度,又使系統(tǒng)的抗干擾能力得到進(jìn)一步提升,同時(shí)滿足系統(tǒng)控制性能要求,保證交流側(cè)輸入電流為正弦,變??;輸出端得到電壓可控且紋波小的直流電壓,中點(diǎn)電位達(dá)到平衡。
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Vienna rectifier with voltage outer loop sliding mode control based on an RBF neural network
YANG Xuhong1, CHEN Yang1, JIA Wei2, FANG Jianfeng1, LUO Xin1, GAO Zixuan1
(1. School of Automation Engineering, Shanghai Electric Power University, Shanghai 200090, China; 2. Shanghai Solar Energy Engineering Technology Research Center, Shanghai 200241, China)
A Vienna rectifier is used as the research object, and an adaptive voltage outer loop sliding mode control algorithm based on the approximation rate is analyzed for its traditional voltage outer loop sliding mode variable structure control invariance and sensitivity to system parameter perturbation. By effectively combining the RBF neural network with the sliding mode control algorithm, the algorithm also adds the midpoint potential balance control to the design of the RBF neural network adaptive voltage outer-loop sliding mode control algorithm. It uses the RBF neural network for adaptive approximation of the voltage outer-loop nonlinear system. This can effectively reduce the switching gain, weaken the jitter and enhance the anti-interference capability of the system. Lastly, simulation analysis and experimental tests are conducted to verify the effectiveness of the proposed control algorithm. The algorithm is compared with the traditional sliding mode control algorithm and the PI control algorithm, and the results show that the use of this voltage external loop control algorithm can provide fast tracking of the target value of the DC output voltage and balanced midpoint potential. This improves the dynamic and static performance of the system and enhances its anti-interference capability.
Vienna rectifier; voltage outer ring; sliding mode variable structure control; near rate; RBF neural network
10.19783/j.cnki.pspc.211361
2021-10-08;
2021-11-23
楊旭紅(1969—),女,通信作者,博士,教授,研究方向?yàn)橹悄茈娋W(wǎng)控制技術(shù)、火電和核電機(jī)組的仿真建模及控制技術(shù)等。E-mail: yangxuhong.sh@163.com
This work is supported by the National Natural Science Foundation of China (No. 51777120).
國(guó)家自然科學(xué)基金項(xiàng)目資助(51777120);上海市2021年度“科技創(chuàng)新行動(dòng)計(jì)劃”項(xiàng)目資助(21DZ1207502)
(編輯 魏小麗)