NEW YORK (TheStreet) - SunPower (SPWRA), Southern Union (SUG), Chesapeake Midstream Partners (CHKM) and Bristow Group (BRS) clocked smart gains this week, while Frontline (FRO - Get Report), Yingli Green Energy Holding (YGE), GT Solar International (SOLR) and Trina Solar (TSL) fared badly.

Among the advancers, SunPower gained 10.1%.

Southern Union topped the charts, jumping 2.7%. Williams has increased its bid on the company to about $5.6 billion in cash, topping its own previous bid of $5 billion in cash.

Chesapeake Midstream Partners rose 1%, Bristow Group edged up 0.9% and PAA Natural Gas Storage ( PNG) moved 0.9% higher.

Complete Production Services ( CPX) advanced 0.8% after equity analyst Brian Uhlmer at Global Hunter Securities raised the stock's rating to buy from accumulate with a target price of $45 per share.

Williams Partners ( WPZ) advanced 0.7% on receiving an FERC endorsement to increase its Transco natural gas pipeline network by another 142,000 dekatherms of incremental firm natural gas transportation capacity by November 2012.

EQT Corporation ( EQT - Get Report) rose 0.5% after SunTrust Robinson's equity analyst Neal Dingmann upgraded the stock to buy from neutral with a 12-month target price of $68 per share.

Frontline was the top lagger, shedding 14.2% after Morgan Stanley lowered its price target to $14.5 from $16. Credit Suisse has also cut the stock's price target from $18 per share to $12.

Yingli Green Energy lost 14% after Goldman cut its rating on the stock to sell from neutral with a price target of $8 per share.

GT Solar and Trina Solar declined 11.3% and 11.2%, respectively.

CGG Veritas ( CGV) erased 10.9% after Barclays Capital downgraded the stock to equal weight from overweight with a target price of 31 euros per share.

Reversing to the downside were Denbury Resources ( DNR - Get Report) down 8.9%, EXCO Resources ( XCO) shedding 8.9%, Hess Corp ( HES - Get Report) trimming 7.9%, Suntech Power Holdings ( STP) erasing 7.8%, Bill Barett Corporation ( BBG) losing 7.7% and Talisman Energy ( TLM) retreating by 7.6%.

ReneSola ( SOL - Get Report) lost 7.5% after the company lowered its second-quarter revenue guidance to the range of $235 million to $245 million, from $280 million to $300 million, owing to declining wafer prices.

Statoil ASA ( STO) decreased 7.4% after Standard & Poor's equity analyst Christine Tiscareno downgraded the stock to sell from buy.

Other losers included SandRidge Energy ( SD - Get Report), First Solar ( FSLR - Get Report), STR Holdings ( STRI), Eni SPA ( E), Oasis Petroleum ( OAS - Get Report), Pioneer Natural Resources ( PXD - Get Report) and YPF SA ( YPF - Get Report).