You have the right to convert your bankruptcy case at any time from Chapter 7 to Chapter 13. In fact, you can convert to Chapter 13 at any time. Even if the trustee objects, the bankruptcy court may grant your petition.
Although you have a right convert your case, you still have to comply with qualification requirements. For example, you must show proof of regular income in order to receive approval for conversion to Chapter 13.
There are many reasons you might want to convert from Chapter 7 to Chapter 13. One of the more common reasons is if you fall behind on your house payments and cannot catch up. Converting to Chapter 13 will stop foreclosure and give you a chance to catch up through the repayment plan.