I actually worked a little on this problem some years ago (as a lab tech; take my knowledge with a gain of salt).
One of the largest components in an inverter (such as found in a Toyota Prius) is the capacitor bank. I'll ignore the electrical design and just assert you need X capacitance to get this done. At least in automotive world, polymer film capacitors are used for this purpose. A polymer film capacitor is made from a (very long) sheet of polymer coated on both sides with a thin layer of metal and rolled up into a cylinder. They get quite bulky at capacitances required by these inverters. The other downside is polymer film cannot handle high temperature. I believe the Prius includes an whole extra cooling loop (in addition to the main loop attached to the engine, which runs hotter than the capacitors) to keep the capacitors cool, so that's even more bulk.
A multi-layer ceramic capacitor of similar capacitance can be much smaller, and can handle far greater temperatures than any polymer. The reason why polymer film is preferred is that when ceramic capacitors fail, they do so catastrophically in much the same way as a ceramic dinner plate shatters. At sufficient voltage, or at lower voltage with a sufficient defect, the ceramic will breakdown: a conduction path will form between the electrodes through the ceramic, which will heat the surrounding area, causing thermal expansion, shattering, and permanent destruction of the capacitor.
The same thing happens in polymer film capacitors, except that because the material is flexible, it does not shatter, and only a small hole around the defect will be ablated away. The remaining capacitor loses some capacitance, but otherwise functions normally.
So one way to create a smaller inverter is to use smaller capacitors, but you've got to match capacitance, voltage-handling ability, and fail gracefully.
Increase the frequency, yes. That's what I thought as well.
But then you run into other issues. The higher the frequency, the less "neat" are the up/down transitions, so your power elements (MOS-FET or whatever) spend more time in that twilight zone, which is exactly where they dissipate most power. And you want to avoid that.
Anyway, it's worth investigating along these lines.
One of the largest components in an inverter (such as found in a Toyota Prius) is the capacitor bank. I'll ignore the electrical design and just assert you need X capacitance to get this done. At least in automotive world, polymer film capacitors are used for this purpose. A polymer film capacitor is made from a (very long) sheet of polymer coated on both sides with a thin layer of metal and rolled up into a cylinder. They get quite bulky at capacitances required by these inverters. The other downside is polymer film cannot handle high temperature. I believe the Prius includes an whole extra cooling loop (in addition to the main loop attached to the engine, which runs hotter than the capacitors) to keep the capacitors cool, so that's even more bulk.
A multi-layer ceramic capacitor of similar capacitance can be much smaller, and can handle far greater temperatures than any polymer. The reason why polymer film is preferred is that when ceramic capacitors fail, they do so catastrophically in much the same way as a ceramic dinner plate shatters. At sufficient voltage, or at lower voltage with a sufficient defect, the ceramic will breakdown: a conduction path will form between the electrodes through the ceramic, which will heat the surrounding area, causing thermal expansion, shattering, and permanent destruction of the capacitor.
The same thing happens in polymer film capacitors, except that because the material is flexible, it does not shatter, and only a small hole around the defect will be ablated away. The remaining capacitor loses some capacitance, but otherwise functions normally.
So one way to create a smaller inverter is to use smaller capacitors, but you've got to match capacitance, voltage-handling ability, and fail gracefully.