Turbocharged engine system and a method of controlling boost pressure

A turbocharged engine system comprising:

• an internal combustion engine, the internal combustion engine in fluid communication with an intake subsystem and an exhaust subsystem;
• a turbocharger arranged to supply a boost pressure to the internal combustion engine via a turbine coupled to a compressor wheel, the turbine being located in the exhaust subsystem and the compressor wheel being located in the intake subsystem;
• an electric compressor arranged to inject a compressed fluid into the exhaust subsystem upstream of the turbine such that, in use, the compressed fluid injected by the electric compressor into the exhaust subsystem maintains a speed of or accelerates the turbine and thereby maintains or increases the boost pressure supplied to the internal combustion engine by the turbocharger;
• and
• one or more control valves arranged to control an injection timing, pressures, and quantity of the compressed fluid injected into the exhaust by the electric compressor, wherein the one or more control valves comprise a bypass valve arranged to bypass the electric compressor, wherein the bypass valve is configured to lower the pressure of the compressed fluid injected by the electric compressor and increase a mass flow through the electric compressor to prevent compressor surge events on the electric compressor.