Simscape - Number of equations exceeds number of variables

[James]

Hi guys I am attempting to model a very simple fuel tank with a pump taking fuel out at a constant rate in Simscape with custom components. The volume in each tank is calculated at each time step with a table lookup of height volume tables which are taken from the geometry of the tank, here I am simply using a cube geometry, so depending on what height the fuel is, the lookup table will give the volume of fuel for that height. When I run the simscape model I receive the error "Number of equations exceeds the number of variables". My code for the components are below;

component HVTable

nodes
Q=TRIAL.domainFuel; %Q:right
end

parameters (Size=variable)
InitialVolume = {20000,'l'}; %Initial Tank Volume
Height = {[0,500,1000,1500,2000,2500,3000,3500,4000,4500,5000],'mm'}; %Fuel Height
Volume = {[0,12500,25000,37500,50000,62500,75000,87500,100000,112500,125000],'l'}; %Fuel Volume
end


outputs
h = {0,'mm'}; %h:left
end

variables
V = {0,'l'};
flow_out={0,'l/s'};
end

function setup
V=InitialVolume;
through(flow_out,Q.Q_jet,[]);
end

equations

V.der == -flow_out;
h == tablelookup(Volume,Height,V,interpolation=linear);

end

end



component BayAMBA

parameters
V={1000,'l'}; % Initial Fuel Volume
TankSize={8000,'l'}; % Tank Size
end

parameters (Size=variable)
Volume = {[1, 2, 4, 8, 10],'l'};
Height = {[0.1, 0.2, 0.4, 0.8, 1],'mm'};
end



nodes
I=TRIAL.domainFuel; % I:left
O=TRIAL.domainFuel; % O:right
end

inputs
H={0,'mm'}; %H:left
end


variables
VolumeFluid={0,'l'};
VolumeUll={0,'l'};
P={0,'Pa'};
end


function setup
if V<0
error ('Volume cannot be negative.')
end

if TankSize<V
error ('Fuel Volume cannot exceed Tank Size.')
end

across(P,I.P,[]);
across(P,O.P,[]);

end

equations

VolumeFluid==tablelookup(Height,Volume,H,interpolation=linear,extrapolation=nearest);
VolumeUll==TankSize-VolumeFluid;
P==0;

end

end



component FixedRate_Pump

nodes
T = TRIAL.domainFuel; % T:left
X = TRIAL.domainFuel; % X:right
end

parameters
commanded_pump_rate = {0.7, 'l/s'}; % Source flow rate
end

variables
P={0,'Pa'};
flow_rate={0,'l/s'}; %flow rate
end

function setup
across(P, T.P, X.P);
through(flow_rate, T.Q_jet, X.Q_jet);
end

equations

flow_rate == commanded_pump_rate;

end


end


Can anyone give me help to find what may be causing this error? Any comments would be greatly appreciated.