I have an msts time series, hourly data of electricity prices that have daily, weekly and yearly seasonality. I am decomposing the data using TBATS. Data I am using covers 365 days.
Residuals have almost zero mean and a normal distribution. However there seems to be some correlation. The data I am using has a lot of spikes with high variance so is this normal? How can I improve the decomposition? How should I evaluate the Ljung Box Test?
data: Residuals from TBATS Q* = 22076, df = 8733, p-value < 2.2e-16
X-squared = 858.16, df = 48, p-value < 2.2e-16