Method for testing electric system and electric system

1. A method for testing an electric system comprising a first inverter and one or more second inverters, the method comprising:

a) starting the first inverter and connecting a DC input of the first inverter to at least one DC power source;

b) providing and sustaining with the first inverter an AC voltage of a predetermined magnitude and a predetermined frequency at the AC output of the first inverter;

c) starting at least one second inverter and connecting an AC output of the started at least one second inverter to the AC output of the first inverter; and

d) supplying with the first inverter reactive power to the started at least one second inverter and supplying with the first inverter active power to the started at least one second inverter.

2. The method of claim 1 , wherein steps c) and d) are performed for each second inverter either simultaneously or at different times.

3. The method of claim 1 , wherein the at least one DC power source comprises one or more photovoltaic panels.

4. The method of claim 1 , wherein in step a) the starting of the first inverter comprises charging a DC circuit of the first inverter from at least one DC power source.

5. The method of claim 1 , wherein in step c) the starting of the at least one second inverter comprises charging a DC circuit of the at least one second inverter from AC power supplied by the first inverter.

6. The method of claim 1 , the method further comprising:

e) connecting a DC input of at least one started second inverter to at least one of said one or more DC power sources;

f) providing and sustaining with said at least one started second inverter the AC voltage of the predetermined magnitude and the predetermined frequency at the AC output of the at least one second inverter connected to a load; and

g) restarting the first inverter and supplying with said at least one started second inverter reactive power to the first inverter.

7. A computer program product comprising computer program code embodied on a non-transitory computer readable medium, wherein execution of the program code in a computer causes the computer to carry out the steps of the method according to claim 1 .

8. An electric system comprising:

a first inverter;

one or more second inverters;

one or more DC power sources; and

control means configured to:

a) start the first inverter and connect a DC input of the first inverter to at least one DC power source;

b) provide and sustain with the first inverter an AC voltage of a predetermined magnitude and a predetermined frequency at the AC output of the first inverter;

c) start at least one second inverter and connect an AC output of the started at least one second inverter to the AC output of the first inverter; and

d) supply with the first inverter reactive power to the started at least one second inverter and supply with the first inverter active power to the started at least one second inverter.

9. The electric system of claim 8 , wherein the control means are configured to perform c) and d) for each second inverter either simultaneously or at different times.

10. The electric system of claim 8 , wherein the DC power source comprises one or more photovoltaic panels.

11. The electric system of claim 8 , wherein, during a), the control means are configured to charge a DC circuit of the first inverter from at least one of said one or more DC power sources when starting the first inverter.

12. The electric system of claim 8 , wherein, during c), the control means are configured to charge a DC circuit of the at least one second inverter from AC power supplied by the first inverter when starting the at least one second inverter.

13. The electric system of claim 8 , wherein the control means are configured to:

e) connect a DC input of at least one started second inverter to at least one of said one or more DC power sources;

f) provide and sustain with said at least one started second inverter the AC voltage of the predetermined magnitude and the predetermined frequency at the AC output of the at least one second inverter connected to a load; and

g) restart the first inverter and supply with said at least one started second inverter reactive power to the first inverter.

14. An electric system comprising:

a first inverter;

one or more second inverters;

one or more DC power sources; and

a control arrangement comprising a processor and a non-transitory memory storing instructions that, when executed by the processor, cause the control arrangement to:

start the first inverter and connect a DC input of the first inverter to at least one DC power source;

provide and sustain with the first inverter an AC voltage of a predetermined magnitude and a predetermined frequency at the AC output of the first inverter;

start at least one second inverter and connect an AC output of the started at least one second inverter to the AC output of the first inverter;

supply with the first inverter reactive power to the started at least one second inverter; and

supply with the first inverter active power to the started at least one second inverter.