vertical axis wind turbine mounted with PMG produces AC. without connecting battery or load on DC side the turbine will run with normal speed. when the battery or any of the load is connected then the turbine speed gets reduced.How to maintain speed?

Sir, I have Vertical axis wind turbine of capacity 100W. It is connected to Permanent magnet generator which produces 3 phase AC. Then it is rectified to DC by using H bridge rectifier. The problem is that when I connect the battery or any of the load, the turbine speed will reduces and generation become less even though there is constant wind speed. Without battery or any of the load, the turbine will run with normal speed. So how can I overcome this problem by maintaining the speed of the turbine with the help of matlab?