Let's look at your wolf first. A base wolf has AC 13, 11 hp, proficiency in Perception and Stealth, and not much more to help in its survival. UA Ranger's Companion's Bond gives it some considerable benefits at level 3, first of them being the ability to add your proficiency bonus to its AC and damage rolls, in addition to its skills, saving throws, and attacks it has proficiency with. Next, it gains two skill proficiencies and becomes proficient in all saving throws. Oh, plus all benefits of your Favored enemy.
What all of this means is that your wolf has AC 15, still 11 hp, but is proficient in all saving throws and has some skills that may help it further. As you gain levels, your beast will increase its maximum hp and proficiency bonus (applied to its AC, saves, skills, attack and damage rolls) at a rate similar to yours, and with a d8 Hit Die, it will not fall far behind. Sure, now it might have less than half your maximum hp, but at later levels it might have more than your party's Wizard or Bard. And even if it dies, you can call it back using 8 hours (can be done during other PC's long rest) and 25gp - to compare, a Potion of Healing (2d4+2) would cost at least twice that.
Now, how to keep it alive. You might have to employ some clever tactical thinking here, but even at 3rd level it should survive one or two blows from the enemy brutes, maybe even a spell. And if it gets hurt, you can just tell it to Disengage and retreat, and take a rest or heal it directly afterwards. As for tactics, a few come to mind:
1) Hit and Run/Assassinate. This utilizes the wolf's Stealth proficiency and comes down to it striking from the enemy's blind spot, Biting to knock the target prone and running away if it finds the situation too dangerous for its liking.
2) Keep it close. If you fight as a duo, you never have to worry about your companion being too far away to be healed, or getting surrounded without anybody to provide help. If you're a Halfling or a Gnome, you might even want to consider riding it into battle!
There are also some other points that may help. First, wolf's Bite can knock its target prone. This gives the wolf, you, and any other ally attacking this target advantage on attacks against it (while within 5', otherwise disadvantage), while having the prone target attack at disadvantage. This heavily shifts the balance in favor of the wolf, even when fighting 1v1. Second, Keen Hearing and Smell paired with proficiency in Perception means that the wolf can notice danger much faster than others, and will rarely be surprised. Third, Pack Tactics, which can help you quickly dispatch a powerful opponent together or curb the numbers of an uneven fight to better match your preferences, especially when paired with a successful knockdown on Bite.
To summarize, your best bet seems to either utilize the wolf's heightened awareness and Stealth to keep it out of harm's way, or heeding the saying "the best defense is a good offence", neutralizing your foes before they have a chance to do any serious damage.