Modular multilevel converter system

Patent metadata

Field	Value
Publication number	US-10673319-B2
Application number	US-201716473717-A
Country	US
Kind code	B2
Filing date	Dec 5, 2017
Priority date	Dec 26, 2016
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

The present invention relates to an MMC converter system which can quickly cut off fault current by installing a plurality of disconnecting switch units on a line connected between two MMC converter devices. The MMC converter system comprises: a first MMC converter device including a plurality of serially connected sub modules; a second MMC converter device including a plurality of serially connected sub modules; a first disconnecting switch unit installed on a line between the first and second MMC converter devices; and a second disconnecting switch unit connected in series to the first disconnecting switch unit on the line, wherein each of the first and second disconnecting switch units comprises a mechanical switch installed on the line so as to open and close the line and a diode connected in parallel to the mechanical switch, and the two diodes are installed in opposite directions to each other.

First claim

The invention claimed is:

1. A modular multilevel converter system, comprising:
a first MMC converter device ( 110 ) including a plurality of sub modules connected in series with each other;
a second MMC converter device ( 210 ) including a plurality of sub modules connected in series with each other;
a first disconnecting switch unit ( 120 ) provided on a line between the first and second MMC converter devices; and
a second disconnecting switch unit ( 220 ) connected in series to the first disconnecting switch unit on the line,
wherein the first and second disconnecting switch units ( 120 and 220 ) respectively include mechanical switches ( 121 and 221 ) provided on the line so as to open and close the line and diodes ( 122 and 222 ) connected in parallel to the mechanical switches ( 121 and 221 ), and the two diodes ( 122 and 222 ) are provided in opposite directions to each other,
wherein the sub-modules ( 111 and 211 ) in the first and second MMC converter devices ( 110 and 210 ) respectively include:
capacitors ( 101 and 201 ) storing energy;
first semiconductor switches ( 102 and 202 ) and second semiconductor switches ( 103 and 203 ) connected in series with each other and connected in parallel to the capacitors;
third semiconductor switches ( 104 and 204 ) and fourth semiconductor switches ( 105 and 205 ) connected in series with each other and connected in parallel to the capacitors;
first output terminals (T 1 and T 1 ′) connected to first intermediated points (N 1 and N 1 ′) of the first semiconductor switches ( 102 and 202 ) and the second semiconductor switches ( 103 and 203 );
second output terminals (T 2 and T 2 ′) connected to any one of first switching terminals (S 1 and S 1 ′) connected to second intermediate points (N 2 and N 2 ′) of the third semiconductor switches ( 104 and 204 ) and the fourth semiconductor switches ( 105 and 205 ), and second switching terminals (S 2 and S 2 ′) connected to common points (NO and NO′) of the second semiconductor switches ( 103 and 203 ), the capacitors ( 101 and 201 ), and the fourth semiconductor switches ( 105 and 205 ); and
switching units ( 106 and 206 ) performing switching so that the second output terminals (T 2 and T 2 ′) are connected to any one of the first switching terminals (S 1 and S 1 ′) and the second switching terminals (S 2 and S 2 ′).

2. The system of claim 1 , wherein the first and second disconnecting switch units ( 120 and 220 ) respectively further include:
a serial connection of capacitors ( 123 and 223 ) connected in parallel to the diodes ( 122 and 222 ) and resistors ( 124 and 224 ).

3. The system of claim 1 , wherein when power is supplied from the first MMC converter device ( 110 ) to the second MMC converter device ( 210 ), the mechanical switch ( 121 ) of the first disconnecting switch unit ( 120 ) is closed and the mechanical switch ( 221 ) of the second disconnecting switch unit ( 220 ) is opened so that current output from the first MMC converter device ( 110 ) flows to the second MMC converter device ( 210 ) through the mechanical switch ( 121 ) of the first disconnecting switch unit ( 120 ) and the diode ( 222 ) of the second disconnecting switch unit ( 220 ).

4. The system of claim 1 , wherein when power is supplied from the second MMC converter device ( 210 ) to the first MMC converter device ( 110 ), the mechanical switch ( 221 ) of the second disconnecting switch unit ( 220 ) is closed and the mechanical switch ( 121 ) of the first disconnecting switch unit ( 120 ) is opened so that current output from the second MMC converter device ( 210 ) flows to the first MMC converter device ( 110 ) through the mechanical switch ( 221 ) of the second disconnecting switch unit ( 220 ) and the diode ( 122 ) of the first disconnecting switch unit ( 120 ).

5. The system of claim 1 , wherein when power is supplied from the first MMC converter device ( 110 ) to the second MMC converter device ( 210 ), the sub-modules ( 111 ) of the first MMC converter device ( 110 ) are provided so that the second output terminal (T 2 ) is connected to the first switching terminal (S 1 ) by switching of the switching unit ( 106 ), and the sub-modules ( 211 ) of the second MMC converter device ( 210 ) is provided so that the second output terminal (T 2 ′) is connected to the second switching terminal (S 2 ′) by switching of the switching unit ( 206 ).

6. The system of claim 1 , wherein when power is supplied from the second MMC converter device ( 210 ) to the first MMC converter device ( 110 ), the sub-modules ( 211 ) of the second MMC converter device ( 210 ) are provided so that the second output terminal (T 2 ′) is connected to the first switching terminal (S 1 ′) by switching of the switching unit ( 206 ), and the sub-modules ( 111 ) of the first MMC converter device ( 110 ) are provided so that the second output terminal (T 2 ) is connected to the second switching terminal (S 2 ) by switching of the switching unit ( 106 ).

7. The system of claim 1 , wherein the first intermediate points (N 1 and N 1 ′) are respectively connected to emitter terminals (E and E′) of the first semiconductor switches ( 102 and 202 ) and collector terminals (C and C′) of the second semiconductor switches ( 103 and 203 ).

8. The system of claim 1 , wherein the second intermediate points (N 2 and N 2 ′) are respectively connected to emitter terminals (E and E′) of the third semiconductor switches ( 104 and 204 ) and collector terminals (C and C′) of the fourth semiconductor switches ( 105 and 205 ).

9. The system of claim 1 , wherein the common nodes (NO and NO′) are respectively connected to emitter terminals (E and E′) of the second semiconductor switches ( 103 and 203 ), negative terminals of the capacitors ( 101 and 201 ), and emitter terminals (E and E′) of the fourth semiconductor switches ( 105 and 205 ).

10. The system of claim 5 , wherein when a fault occurs in the line ( 10 ) while power is being supplied from the first MMC converter device ( 110 ) to the second MMC converter device ( 210 ) through the line ( 10 ),
the sub-modules ( 111 ) of the first MMC converter device ( 110 ) cuts off a fault current flowing from the first MMC converter device ( 110 ) to the line by allowing a sum of voltages of the sub-modules ( 111 ) to form a reverse voltage in a state that the second output terminal (T 2 ) and the first switching terminal (S 1 ) are connected, and cuts off the fault current flowing from the second MMC converter device ( 210 ) to the line by the diode ( 222 ) in a state that the mechanical switch ( 221 ) of the second disconnecting switch unit ( 220 ) is opened.

11. The system of claim 6 , wherein when a fault occurs in the line ( 10 ) while power is being supplied from the second MMC converter device ( 210 ) to the first MMC converter device ( 110 ) through the line ( 10 ),
the sub-modules ( 211 ) of the second MMC converter device ( 210 ) cuts off a fault current flowing from the second MMC converter device ( 210 ) to the line by allowing a sum of voltages of the sub-modules ( 211 ) to form a reverse voltage in a state that the second output terminal (T 2 ′) and the first switching terminal (S 1 ′) are connected, and cuts off the fault current flowing from the first MMC converter device ( 110 ) to the line by the diode ( 122 ) in a state that the mechanical switch ( 121 ) of the first disconnecting switch unit ( 120 ) is opened.

Assignees

• Hyosung Heavy Ind Corp
• Kim Hee Jin
• Hur Kyeon

Inventors

• Kim Hee Jin
• Hur Kyeon
• Lee Dong Su
• Kang Jae Sik
• Jung Ju Yong
• Kim Sang Min
• Na Jong Seo

Classifications

• H02M2001/325

  Electricity · mapped topic

• H02M5/4585

  having a rectifier with controlled elements · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H02M1/32 Primary

  Means for protecting converters other than automatic disconnection · CPC title

• H02M7/4835 Primary

  comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage · CPC title