Three Of My Common Grammar Mistakes

My Three Common Grammar Mistakes:
It has been quite a long time since the beginning of my learning English. Generally speaking, it is not a easy work. One of the reasons is that Chinese is my mother tongue, and there are plenty of difference between these two languages, grammar in particular. After finish my two writing assignments, I find three common grammar mistakes of my assignment writting.
First of all, there comes the problem of word form. For instance, there is a sentence in my essay: "When comparing with previous or existing energy supply, solar power is much more clean and less polluted." Here, what I wanted to do is to compare the two kinds of energy supply and let people figure out the environmental benefit of solar energy. However, there is word form problems with the word comparing and polluted. Since it is passive voice for solar energy which is the subject and the word polluted is of passive meaning, the sentence should be changed into the correct one:"when being compared with previous or existing energy supply, solar power is much more clean and less polluting." There are quite a lot of word form mistakes in my essay, and mainly it is because I have problems with catching the exact and extent meanings of the words I used. From my point of view, memorising will be a good way.
Secondly, I notice that I have some mistakes on subject verb agreement. In my essay, one of the incorrect sentences is "Moreover, solar power need to be generally applied." Here, solar power is singular, then the verb after it should agree with a singular form. Then the correct one is "Moreover, solar power needs to be generally applied." Generally, the mistakes are due to carelessness. However, there are often some other conditions in which SVA mistakes happen easily, like the subjects have different meaning on both singular and plural, the subjects can act as both countable and uncountable, or the subjects and verbs separated by some other patterns.
Besides, another mistake which often appears in my essays is article mistakes. This is the kind of mistake that happens much more commonly, such an "Hybrid engine vehicle technology, the opponents clam, is not economically worthwhile to most of the consumers who are currently using the conventional engine vehicles."(conventional engine vehicles is referred for the first time) and "Nevertheless, the potential problems of driving HEV, claimed by those big car companies, have been minimized to the lowest extent." Here, each of the sentences has the problem of article. In the first one, as I marked, conventional engine is mentioned for the first time, so there should be a "the" ahead because "the" is used for none that everyone has known. And so does the second sentence.
After summarising all my common grammar mistakes, I realize that so many easy mistakes are there in my English writing. It seems there is a urgent need to improve it. Hope to improve and refine my grammar skills by taking this course.