A refrigeration system is powered primarily by a photovoltaic source and by an alternating current (AC) source as a backup. A variable frequency drive is used for controlling a powered component of the refrigeration system. The variable frequency drive includes drive circuitry configured to provide variable frequency power via an output interface, a first interface configured to receive power from the photovoltaic source, a second interface configured to receive AC power from the AC source, a DC bus coupled to the drive circuitry and configured to transmit power to the drive circuitry. The drive circuitry receives power from the first interface when the power from the photovoltaic source is adequate to power the drive circuitry and receives power from the second interface when the power from the photovoltaic source is not adequate to power the drive circuitry.