雙有源橋鉗位變換器的簡(jiǎn)單PWM移相控制策略

孫 玥，程新功，王魯浩，曹立霞，丁廣乾

雙有源橋鉗位變換器的簡(jiǎn)單PWM移相控制策略

孫 玥１，程新功１，王魯浩１，曹立霞２，丁廣乾１

(1.濟(jì)南大學(xué)自動(dòng)化與電氣工程學(xué)院，山東 濟(jì)南 250022；2.山東建筑大學(xué)信息與電氣工程學(xué)院，山東 濟(jì)南 250101)

針對(duì)傳統(tǒng)移相控制方法下雙有源橋變換器會(huì)產(chǎn)生較大電流應(yīng)力和在寬電壓范圍下低效率運(yùn)行的問題，提出一種面向雙有源橋鉗位變換器的簡(jiǎn)單PWM移相控制策略。首先，利用鉗位開關(guān)的運(yùn)行周期和占空比取代變換器內(nèi)移相比，以簡(jiǎn)化原邊H橋工作過程并提高控制自由度。然后，計(jì)算了副邊H橋開關(guān)管的占空比。通過分析所提出的移相控制策略的工作原理和軟開關(guān)特性，推導(dǎo)出以傳輸功率標(biāo)幺值為控制量的線性大信號(hào)模型。最后，采用基于TMS320F2808為控制器的實(shí)驗(yàn)平臺(tái)進(jìn)行驗(yàn)證。實(shí)驗(yàn)結(jié)果展示了簡(jiǎn)單PWM移相控制降低了變換器的電壓應(yīng)力和電流應(yīng)力，顯著提升了變換器的傳輸效率。

雙有源橋；鉗位變換器；簡(jiǎn)單控制；調(diào)制方法；效率

0 引言

電池儲(chǔ)能可以平抑風(fēng)力發(fā)電、光伏發(fā)電的功率波動(dòng)，提高并網(wǎng)風(fēng)電場(chǎng)、光伏電站的電能質(zhì)量，促進(jìn)電力系統(tǒng)穩(wěn)定運(yùn)行[1-4]。搭建科學(xué)合理的能量傳輸系統(tǒng)是實(shí)現(xiàn)儲(chǔ)能和新能源友好互動(dòng)的關(guān)鍵所在。雙有源橋(Dual Active Bridge, DAB)變換器具有能量雙向流動(dòng)、電氣隔離、功率密度高以及易于實(shí)現(xiàn)軟開關(guān)等特點(diǎn)[5-8]，已在直流配電網(wǎng)、電動(dòng)汽車、分布式能源等領(lǐng)域廣泛應(yīng)用[9-12]。

電池儲(chǔ)能環(huán)節(jié)存在電壓寬范圍變化情況，為提高其傳輸效率，控制DAB變換器在寬電壓下高效運(yùn)行至關(guān)重要。一般情況下，DAB的控制方式主要分為移相控制和直流變壓控制。

單移相(Single Phase Shift, SPS)控制是DAB最簡(jiǎn)單的控制策略，該控制操作簡(jiǎn)單、易于實(shí)現(xiàn)[13]，但在輸入輸出電壓幅值不匹配時(shí)，電流應(yīng)力和回流功率會(huì)大幅提升，降低變換器的效率[14]。擴(kuò)展移相(Extended Phase Shift, EPS)控制相比SPS控制減小了回流功率并擴(kuò)大了零電壓開通(Zero Voltage Switching, ZVS)的操作范圍，提高了傳輸效率[14]。雙重移相(Dual Phase Shift, DPS)控制相比EPS控制功率調(diào)節(jié)范圍大，傳輸功率方向改變時(shí)切換容易，提高了調(diào)節(jié)的靈活性[15-16]。隨著控制自由度增加，文獻(xiàn)[17]提出三重移相(Triple Phase Shift, TPS)控制，TPS控制的研究主要集中在優(yōu)化運(yùn)行領(lǐng)域。由于這種控制方式存在3個(gè)控制量，增加了控制維度。但是，TPS控制具有12種工作模態(tài)，模態(tài)切換和優(yōu)化問題求解困難[18]。

此外，文獻(xiàn)[19]提出直流變壓控制，該控制由于H橋逆變器的輸出交流電壓必須低于直流側(cè)電壓，變壓器變比決定了其調(diào)壓能力，所以該方式限制了變換器的調(diào)壓范圍。文獻(xiàn)[20]基于移相控制提出一種調(diào)制方法提高電壓增益，但該調(diào)制方法會(huì)產(chǎn)生較大的電壓應(yīng)力。在寬電壓范圍的應(yīng)用中，DAB的性能通常不能達(dá)到最大[21]。

為提高變換器性能，文獻(xiàn)[22]根據(jù)文獻(xiàn)[23]提出雙有源橋鉗位(Dual Active Bridge Clamp, DABC)變換器的拓?fù)浣Y(jié)構(gòu)，由于變壓器原邊側(cè)輸出電壓為五電平，降低了高頻變壓器兩端的電壓應(yīng)力。同時(shí)，該拓?fù)浣Y(jié)構(gòu)在不同電壓轉(zhuǎn)換比下電流應(yīng)力顯著降低。但該控制方法復(fù)雜，操作難度大。

1 簡(jiǎn)單PWM控制的工作原理及模型分析

1.1 簡(jiǎn)單PWM控制策略的工作模態(tài)分析

圖1 雙有源橋鉗位變換器

圖2 簡(jiǎn)單PWM移相控制原理波形圖

Fig. 2 Waveform of simple PWM phase shift control strategy

圖3 簡(jiǎn)單PWM移相控制策略半周期的工作狀態(tài)

由于電感電流前半周期和后半周期波形具有對(duì)稱性，后半周期的模態(tài)分析與前半周期類似。

1.2 簡(jiǎn)單PWM移相控制策略穩(wěn)態(tài)特性推導(dǎo)

SPS控制的額定電流為[24]

根據(jù)式(8)、式(13)、式(14)得到簡(jiǎn)單PWM移相控制的電流應(yīng)力標(biāo)幺值為

SPS控制的額定傳輸功率為[41]

根據(jù)式(8)—式(12)得到簡(jiǎn)單PWM移相控制的傳輸功率為

根據(jù)式(16)和式(17)對(duì)簡(jiǎn)單PWM移相控制的傳輸功率標(biāo)幺化，則有

假定負(fù)載是固定電阻，輸出功率為

Buck模式下的電壓增益為

2 簡(jiǎn)單PWM控制策略的調(diào)制方法

圖4 簡(jiǎn)單PWM移相控制策略和文獻(xiàn)[22]提出的控制策略寬電壓范圍對(duì)比

DAB變換器減小開關(guān)損耗的重要途經(jīng)是開關(guān)管實(shí)現(xiàn)軟開關(guān)控制[25]。由于開關(guān)S0在變換器中起到電壓鉗位的作用，在整個(gè)負(fù)載范圍內(nèi)除開關(guān)S0外，所有開關(guān)的零電壓開通都很容易獲得，它確保了最小的開關(guān)損耗和更高的傳輸效率，如圖5所示。

圖5 V1側(cè)H橋和V2側(cè)H橋軟開關(guān)特性

圖6 雙有源橋鉗位變換器傳輸功率隨移相比變化的曲線

3 基于線性化功率模型的控制方案

DABC變換器進(jìn)行能量傳輸需要自身的開關(guān)來進(jìn)行控制，開關(guān)導(dǎo)通與關(guān)斷的過程是一個(gè)非線性過程。常規(guī)的模型以移相比作為輸入變量，所建立的大信號(hào)模型存在嚴(yán)重的非線性，只能通過推導(dǎo)出相應(yīng)的小信號(hào)模型來分析控制系統(tǒng)[26]，而小信號(hào)模型階數(shù)高，耦合嚴(yán)重，會(huì)大大增加分析的復(fù)雜性和控制器的設(shè)計(jì)難度[18]。本文基于PI控制器構(gòu)建一個(gè)線性化簡(jiǎn)潔的大信號(hào)模型，通過控制標(biāo)幺化傳輸功率，DABC運(yùn)行狀態(tài)變化時(shí)傳輸功率快速地轉(zhuǎn)換成輸出功率，保證DABC在寬電壓范圍內(nèi)能高效運(yùn)行，實(shí)現(xiàn)快速精準(zhǔn)的動(dòng)態(tài)控制[27]。

圖7 DABC變換器的大信號(hào)模型

在DABC變換器的閉環(huán)控制系統(tǒng)中采用PI控制器[29]，其控制規(guī)律為

由此可將DABC變換器的閉環(huán)控制等效為圖7(c)，其中閉環(huán)傳遞函數(shù)的特征方程為

通過極點(diǎn)配置的方法可以得到

圖8 簡(jiǎn)單PWM移相控制原理圖

4 實(shí)驗(yàn)分析

圖9 DABC實(shí)驗(yàn)平臺(tái)

表1 實(shí)驗(yàn)平臺(tái)參數(shù)

圖10 控制系統(tǒng)結(jié)構(gòu)

圖12 負(fù)載R變化時(shí)輸出電壓和輸入、輸出電流瞬態(tài)實(shí)驗(yàn)波形

圖13 效率曲線對(duì)比

5 結(jié)論

本文基于DABC變換器提出了一種簡(jiǎn)單PWM移相控制策略，并對(duì)其進(jìn)行建模仿真分析和實(shí)驗(yàn)，可以得出以下結(jié)論：

1) 利用S0的占空比和開關(guān)周期實(shí)現(xiàn)變換器在一個(gè)移相比下?lián)碛?個(gè)控制自由度，提高了變換器傳輸功率的可控性，增強(qiáng)了功率調(diào)節(jié)的靈活性。變壓器原邊電壓為五電平，降低了電壓應(yīng)力。

3) 通過占空比和變壓器匝數(shù)比結(jié)合，DABC變換器在BUCK模式下可以獲得更寬的電壓范圍，提高了變換效率；在寬電壓范圍下，該變換器電流應(yīng)力較小，較小的電流應(yīng)力可以延長(zhǎng)開關(guān)管的使用壽命，并且可以選擇較低等級(jí)的開關(guān)管，從而降低開關(guān)管的成本。

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Simple PWM phase shift control strategy for a dual active bridge clamp converter

SUN Yue1, CHENG Xingong1, WANG Luhao1, CAO Lixia2, DING Guangqian1

(1. School of Electrical Engineering, University of Jinan, Jinan 250022, China;2. School of Information and Electrical Engineering, Shandong Jianzhu University, Jinan 250101, China)

A simple PWM phase shift control strategy for a dual active bridge clamp converter is proposed to address the problems of large current stress and low transmission efficiency over a wide voltage range in the conventional phase shift control method. First, the operational period and duty cycle of the clamp switch are used instead of the inter phase shift ratio of the converter to simplify the primary H-bridge operation and improve the degrees of control freedom. Then the duty cycle of the secondary H-bridge switches is calculated. By analyzing the working principle and soft switching characteristics of the proposed phase shift control strategy, a linear large-signal model is derived with the unified transmission power per-unit value as the control quantity. Finally, an experimental platform based on TMS320F2808 as the controller is used for verification. The results demonstrate that the simple PWM phase shift control reduces the voltage stress and current stress of the converter and significantly improves its transmission efficiency.

dual active bridge; clamp converter;simple control; modulation method; efficiency

10.19783/j.cnki.pspc.211433

國(guó)家自然科學(xué)基金項(xiàng)目資助(61803174)；山東省自然科學(xué)基金項(xiàng)目資助(ZR2019BF024，ZR2020ME198)

2021-10-25；

2022-01-19

孫 玥(1996—)，男，碩士研究生，研究方向?yàn)殡p有源橋DC-DC變換器控制技術(shù)與應(yīng)用；E-mail: sunyue_996@ 163.com

程新功(1973—)，男，通信作者，博士，教授，研究方向?yàn)殡娏﹄娮蛹夹g(shù)、新能源發(fā)電等；E-mail: cse_cxg@ ujn.edu.cn

王魯浩(1987—)，男，博士，講師，研究方向?yàn)閺?fù)雜能源系統(tǒng)建模優(yōu)化、優(yōu)化理論及應(yīng)用。E-mail: cse_wanglh@ ujn.edu.cn

This work is supported by the National Natural Science Foundation of China (No. 61803174).

(編輯 魏小麗)