Electrical system and control method

1 . A method of operating an electrical system comprising: a passive filter, an active power converter, a first AC connecting bus extending between the active power converter and the passive filter, a second AC connecting bus extending between the passive filter and an AC network, a DC connecting bus extending between the active power converter and a DC network, and a monitoring arrangement, the method comprising:

operating in a first mode including:

monitoring an AC voltage on the first AC connecting bus using the monitoring arrangement; and

determining a plurality of parameters of an operating AC voltage of the AC network based on the monitored AC voltage on the first AC connecting bus; and

subsequently operating in a second mode including:

controlling the active power converter to convert a DC voltage received from the DC network into an AC voltage for supply to the AC network via the passive filter, wherein controlling the active power converter is based on:

a mathematical model of a set of electrical characteristics of the passive filter; and

the plurality of parameters of the operating AC voltage of the AC network.

2 . The method of claim 1 , wherein each of the plurality of parameters of the operating AC voltage on the AC network is selected from a group consisting of: a phase, a fundamental frequency, and a magnitude of the operating AC voltage on the AC network.

3 . The method of claim 1 , wherein:

subsequently operating in the second mode includes:

controlling a duty cycle, a switching frequency and/or a switching phase of the active power converter.

4 . The method of claim 1 , wherein:

the plurality of parameters of the operating AC voltage on the AC network includes a fundamental frequency and a phase of the operating AC voltage on the AC network; and

operating in the second mode includes:

controlling the active power converter to match:

a fundamental frequency and a phase of the AC voltage on the second AC connecting bus; with

the fundamental frequency and the phase, respectively, of the operating AC voltage of the AC network.

5 . The method of claim 1 , wherein:

the plurality of parameters of the operating AC voltage on the AC network includes a magnitude of the operating AC voltage on the AC network; and

controlling the active power converter is further based on:

a magnitude of a voltage of the DC network.

6 . The method of claim 1 , wherein:

operating in the first mode includes:

determining the plurality of parameters of the operating AC voltage of the AC network based on:

the monitored AC voltage on the first AC connecting bus; and

a mathematical model of the set of electrical characteristics of the passive filter.

7 . The method of claim 1 , wherein:

operating in the first mode further includes:

controlling the active power converter to convert an AC voltage received from the AC network via the passive filter into a DC voltage for supply to the DC network.

8 . The method of claim 1 , wherein the AC network is an AC grid network.

9 . An electrical system comprising: a passive filter, an active power converter, a first AC connecting bus extending between the active power converter and the passive filter, a second AC connecting bus extending between the passive filter and an AC network, a DC connecting bus extending between the active power converter and a DC network, a monitoring arrangement configured to monitor an AC voltage on the first AC connecting bus, and a controller adapted to control the active power converter based on the monitored AC voltage on the first AC connecting bus;

wherein the controller is adapted to perform a method of operating the electrical system, the method comprising:

operating in a first mode including:

monitoring an AC voltage on the first AC connecting bus using the monitoring arrangement; and

determining a plurality of parameters of an operating AC voltage of the AC network based on the monitored AC voltage on the first AC connecting bus; and

subsequently operating in a second mode including:

controlling the active power converter to convert a DC voltage received from the DC network into an AC voltage for supply to the AC network via the passive filter, wherein controlling the active power converter is based on:

a mathematical model of a set of electrical characteristics of the passive filter; and

the plurality of parameters of the operating AC voltage of the AC network.

10 . The electrical system of claim 9 , wherein the passive filter includes at least one reactive electrical component.

11 . The electrical system of claim 9 , wherein the active power converter includes at least one active power switching component.

12 . A software program comprising instructions which, when executed by the controller of the electrical system of claim 9 , cause the controller to execute a method of operating the electrical system, the method comprising:

operating in a first mode including:

monitoring an AC voltage on the first AC connecting bus using the monitoring arrangement; and

determining a plurality of parameters of an operating AC voltage of the AC network based on the monitored AC voltage on the first AC connecting bus; and

subsequently operating in a second mode including:

controlling the active power converter to convert a DC voltage received from the DC network into an AC voltage for supply to the AC network via the passive filter, wherein controlling the active power converter is based on:

a mathematical model of a set of electrical characteristics of the passive filter; and

the plurality of parameters of the operating AC voltage of the AC network.

13 . A machine-readable medium having stored thereon the software program of claim 12 .