import re


def convert_ip_address(ip_address: str):
    """
    This function converts a ipv4 address in standard string format to a HEX representation

    :param ip_address: string with IPv4 address in format '192.168.0.1'
    :return: HEX representation of IPv4 address (string)
    """
    if re.search('^((25[0-5]|(2[0-4]|1[0-9]|[1-9]|)[0-9])(\.(?!$)|$)){4}$', ip_address) is None:
        return None
    ip_addr = ip_address.split('.')
    for i in range(4):
        ip_addr[i] = hex(int(ip_addr[i]))[2:]
        while len(ip_addr[i]) < 2:
            ip_addr[i] = '0' + ip_addr[i]
    ip_address = ip_addr[0] + ip_addr[1] + ' ' + ip_addr[2] + ip_addr[3]
    return ip_address