WO2020237662A1

WO2020237662A1 - Brake chopper

Info

Publication number: WO2020237662A1
Application number: PCT/CN2019/089634
Authority: WO
Inventors: Eduardo Rath ROHR; Guangming PEI; Hua Wei; Min Li; Ulrich Schlapbach
Original assignee: Abb Schweiz Ag
Priority date: 2019-05-31
Filing date: 2019-05-31
Publication date: 2020-12-03

Abstract

Embodiments of present disclosure relates to a DC voltage chopper device. The DC voltage chopper device comprises a first chopper circuit configured to be coupled between a first DC voltage line of a DC voltage link and a neutral point terminal. The first chopper circuit comprises a first resistor, and a first switch coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link. By utilizing the embodiments of the present disclosure, the DC voltage device may be easily configured, and can protect the electrical system from overvoltage.

Description

BRAKE CHOPPER

TECHNICAL FIELD

Example embodiments of the present disclosure generally relate to electricity transmission and more particularly, to a brake chopper for overvoltage protection and excess energy absorption during electricity transmission.

BACKGROUND

Neutral Point Clamped (NPC) topology is widely used in high voltage converters. In order to protect the converter from an overvoltage failure, a brake chopper is often installed to dissipate the energy feed from load side.

In case of the overvoltage, the large current caused by the overvoltage is transmitted through the brake chopper, and the resistor of the brake chopper generates heat according to Joule’s law, such that the energy can be transformed into heat dissipated by the resistor.

Conventionally, the brake chopper is coupled between the upper rectifier or converter and the lower rectifier or converter, and has a resistor coupled in parallel to a circuit breaker. In case of overvoltage, the circuit breaker is opened to have the current flow through the resistor. Chinese patent application CN108432107A describes such an approach. However, such approach may drive up cost and footprint since the circuit breaker and resistor need to withstand the entire current caused by the DC voltage link.

SUMMARY

Example embodiments of the present disclosure propose a solution for DC voltage chopper device and electrical system.

In a first aspect, it is provided a DC voltage chopper device. The DC voltage chopper device comprises a first chopper circuit configured to be coupled between a first DC voltage line of a DC voltage link and a neutral point terminal. The first chopper circuit comprises a first resistor, and a first switch coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link.

In a second aspect, it is provided an electrical apparatus. The electrical apparatus comprises a voltage sensor configured to detect a first voltage of a DC voltage link; a DC chopper voltage device of the first aspect configured to be coupled to the DC voltage link; a controlling center coupled to the voltage sensor and the DC voltage chopper device. The controlling center is configured to receive a first voltage signal indicative of the first voltage from the voltage sensor; determine an overvoltage of the DC voltage link based on the first voltage signal; in response to determining the overvoltage, transmit a first driving instruction to cause a first chopper circuit coupled between a first DC voltage line of the DC voltage link and a neutral point terminal to flow a first current caused by the overvoltage.

In a third aspect, it is provided a method for manufacturing a DC voltage chopper device. The method comprises providing a first chopper circuit configured to be coupled between a first DC voltage line of a DC voltage link and a NP terminal. The first chopper circuit comprises a first resistor, and a first switch coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link.

According to the embodiments of the present disclosure, the DC voltage device may be easily configured, and can protect the electrical system from overvoltage.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the following detailed descriptions with reference to the accompanying drawings, the above and other objectives, features and advantages of the example embodiments disclosed herein will become more comprehensible. In the drawings, several example embodiments disclosed herein will be illustrated in an example and in a non-limiting manner, wherein:

Fig. 1 illustrates an electric system in accordance with some example embodiments of the present disclosure;

Fig. 2 illustrates a brake chopper circuit in accordance with some example embodiments of the present disclosure;

Fig. 3 illustrates a method for manufacturing a brake chopper device in accordance with some example embodiments of the present disclosure; and

Fig. 4 illustrates a method for manufacturing an electronic device in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or corresponding reference symbols refer to the same or corresponding parts.

DETAILED DESCRIPTION

The subject matter described herein will now be discussed with reference to several example embodiments. These embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein, rather than suggesting any limitations on the scope of the subject matter.

The term “comprises” or “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” The term “or” is to be read as “and/or” unless the context clearly indicates otherwise. The term “based on” is to be read as “based at least in part on. ” The term “being operable to” is to mean a function, an action, a motion or a state can be achieved by an operation induced by a user or an external mechanism. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ”

Unless specified or limited otherwise, the terms “mounted, ” “connected, ” “supported, ” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Furthermore, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. In the description below, like reference numerals and labels are used to describe the same, similar or corresponding parts in the Figures. Other definitions, explicit and implicit, may be included below.

The term “neutral point” is widely used in DC transmission of high-power application. In this disclosure, it refers to a middle point in potential that has half potential of a DC voltage link. Unless specified or limited otherwise, the terms “resistor” , “capacitor” , “inductor” , “switch” , “thyristor” , “IGBT” and other electrical element may include one or more element that has the same function and operates together to achieve the function. For example, a resistor may refer to two or more resistors connected in serial to function as one resistor.

As mentioned above, the conventional brake chopper is coupled between the upper rectifier or converter and the lower rectifier or converter, and may drive up cost and footprint since the circuit breaker and resistor need to withstand the entire current caused by the DC voltage link. As such, it is desired to provide a new brake chopper that may reduce cost.

Fig. 1 illustrates an electric system 100 in accordance with some example embodiments of the present disclosure. The electric system 100 is of NPC topology, and includes alternative current (AC) source 12, a transformer 14 and an inverter 16. The AC source 12 generates AC electricity.

The transformer 14 is coupled to the AC source 12, and has a primary winding and two secondary windings to generate a first transformed AC voltage and a second transformed AC voltage respectively. The first secondary winding is coupled to the upper rectifier 15 to generate a first direct current (DC) voltage V _DC via a first inductor L1 from the first transformed AC voltage. The second secondary winding is coupled to the lower rectifier 17 to generate a second DC voltage –V _DC via second inductor L2 from the second transformed AC voltage.

The inverter 16 is coupled to the upper and lower rectifiers 15 and 17 to transform the DC voltages of a DC voltage link into an AC voltage. The transformed AC voltage may apply to a motor. Although an inverter 16 is illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, a load may be provided to replace the inverter 16.

In Fig. 1, the middle node between the upper rectifier 15 and the lower rectifier 17 is coupled to the inverter 16 via a resistor R2. The node between the resistor and the inverter 16 is the neutral pointe (NP) terminal. Although the resistor R2 is illustrated in the configuration, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the resistor R2 may be omitted in some example since the connection line itself have resistance.

The NP terminal NP is coupled to a power ground GND via a capacitor C3 in parallel to a resistor R1 for maintaining the potential of the NP terminal. Although the capacitor C3 and the resistor R1 are illustrated in the configuration, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the capacitor C3 and the resistor R1 may be omitted in some example.

A first capacitor C1 and a second capacitor C2 are provided between the positive line V _DC and the negative line –V _DC with the middle node coupled to the NP terminal so as to maintain the potential of the NP terminal. Although the differential configuration of positive and negative transmission lines is illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the DC voltage chopper device herein may apply to a single terminal configuration including a positive transmission line and a ground line.

A fault may occur on at least one of the transmission lines V _DC and –V _DC. The fault may cause an overvoltage on the at least one of the transmission lines V _DC and –V _DC. If the overvoltage is not eliminated immediately, this may cause severe damage to the rectifiers and/or inverters.

To remove the overvoltage, a DC voltage chopper device 10 is coupled between the positive transmission line V _DC and the negative transmission line –V _DC. The DC voltage chopper device 10 may include a first DC chopper circuit or an upper DC chopper circuit 40, and a second DC chopper circuit or a lower DC chopper circuit 60. The middle node between the upper and lower DC chopper circuit 40 and 60 are coupled to the NP terminal.

The upper and lower DC chopper circuit 40 and 60 may have similar or symmetric configuration. The difference between them is that the upper DC chopper circuit 40 is coupled between the positive transmission line V _DC and the NP terminal, while the lower DC chopper circuit 60 is coupled between the NP terminal and the negative transmission line –V _DC. Thus, the upper chopper circuit 40 will be described hereinafter, while the description for the lower chopper circuit 60 is omitted for brevity.

The electrical system 100 may have a first voltage sensor 13 and a second voltage sensor 19 to periodically or continuously measure or monitor the voltages of the positive transmission line V _DC and the negative transmission line –V _DC, respectively. Although the first and

second voltage sensors

13 and 19 are illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, a voltage sensing unit may apply to sense both the voltages of the positive transmission line V _DC and the negative transmission line –V _DC.

The first and

second voltage sensors

13 and 19 transmit indications of the measured voltages to the controlling center 18. The controlling center 18 may determine an overvoltage based on the measured voltages. For example, in case that the detected voltage for the positive transmission line V _DC exceeds a predetermined voltage value, the controlling center 18 determines an overvoltage accordingly.

Although the first voltage sensor 13 is illustrated to be separate from the upper chopper circuit 40, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the first voltage sensor 13 may be incorporated in the upper chopper circuit 40 or the brake chopper device 10. Analogously, the second voltage sensor 19 may be incorporated in the lower chopper circuit 60 or the brake chopper device 10. In another example, the voltage sensing unit which may apply to sense both the voltages of the positive transmission line V _DC and the negative transmission line –V _DC may be incorporated in the brake chopper device 10.

In response to determining the overvoltage, the controlling center 18 may control at least one of the upper and lower chopper circuits 40 and 60 to flow the current caused by the overvoltage. For example, in case that an overvoltage occurs at the positive line V _DC, the controlling center 18 may cause the current caused by the overvoltage to flow through the upper chopper circuit 40 to the NP terminal. Analogous operation may apply to overvoltage at the negative transmission line –V _DC and the lower chopper circuit 60.

In another example, in case that the overvoltage occurs at both the positive and negative transmission lines V _DC and –V _DC, the controlling center 18 may cause the current caused by the overvoltage to flow through the upper and lower chopper circuits 40 and 60 to the NP terminal.

Fig. 2 illustrates a brake chopper circuit 40 in accordance with some example embodiments of the present disclosure. The brake chopper circuit 40 may include a switch 42 and a resistor 44 coupled to the switch 42. The switch 42 and a resistor 44 are serially coupled between the positive transmission line V _DC and the NP terminal. During overvoltage removal, a large amount of current flows through the resistor 44, causing a lot of energy generated in accordance with Joule’s law.

As such, the built up energy may be transformed into heat, and the heat can be dissipated on the resistor 44. In this event, the energy will not accumulate in the rectifiers or inverters, and the DC voltage chopper device thus prevents the electrical system from overvoltage. In practice, resistance of the resistor 44 may be customized as needed.

The first switch may include an insulated gate bipolar transistor (IGBT) . Although an IGBT is illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, a MOSFET for power electronics or an integrated gate commutated thyristors (IGCT) may be applied.

The brake chopper circuit 40 may include a driving circuit 41, an interface circuit 43 and a current sensor 45. Although the brake chopper circuit 40 is illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the brake chopper circuit 40 may include the first voltage sensor 13.

In another example, at least one of the driving circuit 41, the interface circuit 43 and the current sensor 45 is not included in the brake chopper circuit 40. Instead, the at least one of the driving circuit 41, the interface circuit 43 and the current sensor 45 may be provided by an independent circuit device.

The driving circuit 41 is configured to turn on or off the first switch 42 in response to receiving the instruction from the controlling center 18. The sensor 45 is configured to periodically or continuously measure or detect the current flowing through the resistor 44. In an example, the sensor 45 is configured to continuously measure or detect the current flowing through the resistor 44 in synchronization with the turning-on of the switch 42, and send the sensed signal to the interface circuit 43.

The interface circuit 43 may process the current signal, if necessary, and transmit an indication of the current flowing through the resistor 44 to the controlling center 18. The controlling center 18 receives the current signal indicative of the current from a first interface circuit of the DC voltage chopper device.

The resistor 44 may need to be replaced sometimes, because the large current striking the resistor 44 may cause the resistor 44 to age or degrade. The controlling center 18 may determine a condition or a temperature of the first resistor based on the first current signal and the first voltage signal. In an example, the controlling center 18 may determine a resistance of the resistor 44 based the sensed current and the detected voltage V _DC at the starting stage of the electrical system.

The resistance of the resistor 44 may vary as the resistor 44 ages and temperature varies. Thus, the resistance of the resistor 44 at the starting stage may be used to indicate a comparable parameter at the room temperature, such as 20℃. The controlling center 18 may determine a difference between the determined resistance and an initial resistance of the first resistor stored in a lookup table inside the controlling center 18.

The initial resistance of the first resistor indicates the original resistance at the room temperature. The controlling center 18 may in turn determine the condition of the first resistor based on the determined difference. Although difference comparison is illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the controlling center 18 may directly determine the condition based on the resistance of the resistor 44, if the controlling center 18 has stored a mapping relationship between resistance at room temperature and condition.

In case that the controlling center 18 determines that the resistor 44 cannot serve, the controlling center 18 may transmit an alert to users so as to indicate that the resistor 44 needs to be replaced. As such, potential damage may be avoided in advance since the resistor 44 may be replaced in advance before it has a fault.

In an embodiment, the temperature of the resistor 44 during running may be determined or monitored. It is known that resistance of a resistor may vary depending on the temperature of the resistor. In the embodiment, the resistance of resistor 44 may be determined based on the detected voltage V _DC and the current flowing through the resistor 44, as described above.

The controlling center 18 may have a lookup table storing relationship between resistance of the resistor 44 and temperature. As such, the controlling center 18 may determine temperature of the resistor 44 by looking into the table. In some examples, the resistance of the resistor 44 at the starting stage may be taken into consideration for calibration.

In some examples, the controlling center 16 may further determine overcurrent, short circuit, open circuit and resistor overheat fault based on the detected voltage V _DC, the sensed current and pre-stored table.

It is generally desired to keep NP potential stable at the middle of the DC voltage link. Conventionally, numerous solutions with topology change (hardware) or software algorithm have been proposed. An example of conventional approach based on hardware is to add switches connecting to higher DC voltage capacitor. The switches are turned on to cause energy stored in the inductor, and they are turned off to transfer the energy to the lower DC voltage capacitor. From the perspective of controlling complexity, it is easy, but it increases hardware cost.

Some software-based solutions, such as space vector pulse width modulation (SVPWM) and sinusoidal pulse width modulation (SPWM) are complex in controlling topology. In addition, the SVPWM solution may increase the output voltage harmonic, and the SPWM may lower the efficiency of DC voltage.

The embodiments disclosed herein may provide a simple and low cost solution. In an embodiment, the controlling center 18 is configured to receive first and second voltage signals indicative of the first and second voltages (V _DC, -V _DC) of the DC voltage link. The controlling center 18 may determine a voltage difference based on the first and second voltage signals, and determine an imbalance of a neutral point (NP) based on the determined voltage difference.

For example, the controlling center 18 may compare the determined voltage difference with a predetermined voltage value. If the determined voltage difference is greater than the predetermined voltage value, the imbalance of the neutral point (NP) occurs.

The controlling center 18 may selectively turn on one of first and second switches of the DC voltage chopper device in response to determining the imbalance of the neutral point (NP) . For example, if the determined voltage difference is greater than the predetermined voltage value and the absolute value of voltage V _DC is greater than the absolute value of the voltage –V _DC, the controlling center 18 may turn on the switch 42 of the upper DC chopper circuit 40 to drag the potential of NP terminal to a middle point between the voltage V _DC and the voltage –V _DC.

Analogously, if the determined voltage difference is greater than the predetermined voltage value and the absolute value of voltage V _DC is below than the absolute value of the voltage –V _DC, the controlling center 18 may turn on the switch of the lower DC chopper circuit 60 to drag the potential of NP terminal to a middle point between the voltage V _DC and the voltage –V _DC so as to keep NP potential stable at the middle of the DC voltage link.

As such, the embodiments herein may balance the NP potential, in addition to protecting the DC voltage link from overvoltage, and a stable DC voltage may thus be obtained.

Although the configuration of the first DC voltage circuit 40 is illustrated, this only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the driving circuit 41, the interface circuit 43 and the sensor of the first DC voltage chopper circuit 40 and the driving circuit, the interface circuit and the sensor of the second DC voltage chopper circuit 60 may be provided as a configuration including a single driving circuit, a single interface circuit and a single current sensor.

The single driving circuit may be configured to drive the switches of the first and second DC voltage chopper circuits, the single interface circuit may communicate with both the first and second DC voltage chopper circuits, and the single current sensor may sense current of the first and second DC voltage chopper circuits.

Fig. 3 illustrates a method 200 for manufacturing a DC brake chopper device in accordance with some example embodiments of the present disclosure. The method can be applied to manufacture the DC chopper device 10. At 202, it is provided a first chopper circuit. The first chopper circuit may be the DC chopper circuit 40, and configured to be coupled between a first DC power supply (V _DC) of a DC voltage link and a neutral point terminal.

In an example, it is also provided a second chopper circuit. The second chopper circuit may be the DC chopper circuit 60, and configured to be coupled between a second DC power supply (-V _DC) of a DC voltage link and the neutral point terminal.

It is to be understood that the description of the brake chopper device with respect to Figs. 1 and 2 can be applied to the DC brake chopper device of Fig. 3

Fig. 4 illustrates a method 300 for manufacturing an electronic device in accordance with some example embodiments of the present disclosure. The electronic device may include at least one of the components as depicted in Fig. 1.

At 302, it is provided a voltage sensor. The voltage sensor may be the voltage sensor 13 in Fig. 1, and configured to detect a first voltage (V _DC) of a DC voltage link. In an example, it is provided another voltage sensor. The another voltage sensor may be the voltage sensor 19 in Fig. 1, and configured to detect a second voltage (-V _DC) of a DC voltage link.

At 304, it is provided a DC voltage chopper device. The DC voltage chopper device may be the DC voltage chopper device 10 of Fig. 1, and configured to be coupled to the DC voltage link so as to protect the DC voltage link from overvoltage.

At 306, it is provided a controlling center. The controlling center may be the controlling center 18, and coupled to voltage sensor and the DC voltage chopper device. The controlling center may receive an indication of the detected voltage, and communicate with the DC voltage chopper device.

It is to be understood that the description of the brake chopper device with respect to Figs. 1 and 2 can be applied to the electronic device of Fig. 4.

Hereinafter, some example implementations of the subject matter described herein will be listed.

Item 1: There is provided a DC voltage chopper device. The DC voltage chopper device comprises a first chopper circuit configured to be coupled between a first DC voltage line of a DC voltage link and a neutral point terminal. The first chopper circuit comprises a first resistor, and a first switch coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link.

Item 2: According to the DC voltage chopper device of Item 1, the DC voltage chopper device further comprises a second chopper circuit configured to be coupled between a second DC voltage line of the DC voltage link and the NP terminal. The second chopper circuit comprises a second resistor, and a second switch coupled to the second resistor and configured to flow a second current caused by another overvoltage of the DC voltage link.

Item 3: According to the DC voltage chopper device of Item 1 or 2, at least one of the first and second switches includes an insulated gate bipolar transistor or an integrated gate commutated thyristors; and the first and second chopper circuits are configured to operate independently from each other.

Item 4: According to the DC voltage chopper device of any of Items 1-3, the DC voltage chopper device further comprises a first current sensor configured to sense the first current flowing through the first chopper circuit.

Item 5: According to the DC voltage chopper device of any of Items 1-4, the DC voltage chopper device further comprises a first driving circuit coupled to the first switch and configured to turn on the first switch in response to detecting the overvoltage of the first DC voltage line.

Item 6: According to the DC voltage chopper device of any of Items 1-5, the DC voltage chopper device further comprises a first interface circuit coupled to the first current sensor and configured to receive a first current signal indicative of the first current from the first current sensor; and transmit the first current signal to a controlling center.

Item 7: According to the DC voltage chopper device of any of Items 1-6, the first interface circuit is coupled to the first driving circuit and further configured to receive a first driving instruction from the controlling center in response to detecting the overvoltage; and transmit the first driving instruction to the first driving circuit to cause the first current flowing through the first resistor.

Item 8: There is provided an electrical apparatus. The electrical apparatus comprises a voltage sensor configured to detect a first voltage of a DC voltage link; a DC chopper voltage device of any of Items 1-7 configured to be coupled to the DC voltage link; a controlling center coupled to the voltage sensor and the DC voltage chopper device. The controlling center is configured to receive a first voltage signal indicative of the first voltage from the voltage sensor; determine an overvoltage of the DC voltage link based on the first voltage signal; in response to determining the overvoltage, transmit a first driving instruction to cause a first chopper circuit coupled between a first DC voltage line of the DC voltage link and a neutral point terminal to flow a first current caused by the overvoltage.

Item 9: According to the electrical apparatus of Item 8, the controlling center is further configured to receive a first current signal indicative of a first current from a first interface circuit of the DC voltage chopper device, the first current sensed by a first sensor of the DC voltage chopper device; and determine a condition or a temperature of the first resistor based on the first current signal and the first voltage signal.

Item 10: According to the electrical apparatus of Item 8 or 9, determining the condition of the first resistor comprises determining a resistance of the first resistor based the first sensed current and the detected voltage; determining a difference between the determined resistance and an initial resistance of the first resistor stored in a lookup table; and determining the condition of the first resistor based on the determined difference.

Item 11: According to the electrical apparatus of any of Items 8-10, the controlling center is further configured to transmit an alert in response to determining a condition of requiring replacement.

Item 12: According to the electrical apparatus of any of Items 8-11, the controlling center is further configured to receive a second voltage signal indicative of the second voltage of the DC voltage link; determine a voltage difference based on the first and second voltage signals; and determine an imbalance of a NP based on the determined voltage difference.

Item 13: According to the electrical apparatus of any of Items 8-12, the controlling center is further configured to in response to determining the imbalance of the NP, selectively turn on one of first and second switches of the DC voltage chopper device.

Item 14: According to the electrical apparatus of any of Items 8-13, the electrical apparatus further comprises a first rectifier coupled to a first power supply of the DC voltage link and the NP terminal to generate the first voltage with a first alternative current (AC) current from a first secondary winding; and a second rectifier coupled to a second power supply of the DC voltage link and the NP terminal to generate the second voltage with a second AC current from a second secondary winding.

Item 15: There is provided a method for manufacturing a DC voltage chopper device. The method comprises providing a first chopper circuit configured to be coupled between a first DC voltage line of a DC voltage link and a NP terminal. The first chopper circuit comprises a first resistor, and a first switch coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. On the other hand, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A DC voltage chopper device (10) comprising:

a first chopper circuit (40) configured to be coupled between a first DC voltage line (V _dc) of a DC voltage link and a neutral point (NP) terminal, the first chopper circuit (40) comprising:

a first resistor (44) , and

a first switch (42) coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link.
The DC voltage chopper device of claim 1, further comprising:

a second chopper circuit (60) configured to be coupled between a second DC voltage line (-V _dc) of the DC voltage link and the NP terminal, the second chopper circuit (60) comprising:

a second resistor, and

a second switch coupled to the second resistor and configured to flow a second current caused by another overvoltage of the DC voltage link.
The DC voltage chopper device of claim 2, wherein at least one of the first and second switches includes an insulated gate bipolar transistor (IGBT) or an integrated gate commutated thyristors (IGCT) ; and

the first and second chopper circuits are configured to operate independently from each other.
The DC voltage chopper device of claim 1, further comprising:

a first current sensor (45) configured to sense the first current flowing through the first chopper circuit (40) .
The DC voltage chopper device of claim 4, further comprising:

a first driving circuit (41) coupled to the first switch and configured to turn on the first switch in response to detecting the overvoltage of the first DC voltage line.
The DC voltage chopper device of claim 5, further comprising:

a first interface circuit (43) coupled to the first current sensor and configured to

receive a first current signal indicative of the first current from the first current sensor; and

transmit the first current signal to a controlling center.
The DC voltage chopper device of claim 6, wherein the first interface circuit is coupled to the first driving circuit and further configured to

receive a first driving instruction from the controlling center in response to detecting the overvoltage; and

transmit the first driving instruction to the first driving circuit to cause the first current flowing through the first resistor.
An electrical apparatus comprising:

a voltage sensor (13) configured to detect a first voltage of a DC voltage link;

a DC chopper voltage device (10) of any of claims 1-7 configured to be coupled to the DC voltage link;

a controlling center (18) coupled to the voltage sensor and the DC voltage chopper device, and configured to

receive a first voltage signal indicative of the first voltage from the voltage sensor;

determine an overvoltage of the DC voltage link based on the first voltage signal;

in response to determining the overvoltage, transmit a first driving instruction to cause a first chopper circuit (40) coupled between a first DC voltage line (V _DC) of the DC voltage link and a neutral point (NP) terminal to flow a first current caused by the overvoltage.
The electrical apparatus of claim 8, wherein the controlling center is further configured to

receive a first current signal indicative of a first current from a first interface circuit of the DC voltage chopper device, the first current sensed by a first sensor of the DC voltage chopper device; and

determine a condition or a temperature of the first resistor based on the first current signal and the first voltage signal.
The electrical apparatus of claim 9, wherein determining the condition of the first resistor comprises:

determining a resistance of the first resistor based the first sensed current and the detected voltage;

determining a difference between the determined resistance and an initial resistance of the first resistor stored in a lookup table; and

determining the condition of the first resistor based on the determined difference.
The electrical apparatus of claim 10, wherein the controlling center is further configured to transmit an alert in response to determining a condition of requiring replacement.
The electrical apparatus of claim 8, wherein the controlling center is further configured to

receive a second voltage signal indicative of the second voltage of the DC voltage link;

determine a voltage difference based on the first and second voltage signals; and

determine an imbalance of a neutral point (NP) based on the determined voltage difference.
The electrical apparatus of claim 12, wherein the controlling center is further configured to

in response to determining the imbalance of the neutral point (NP) , selectively turn on one of first and second switches of the DC voltage chopper device.
The electrical apparatus of claim 12, further comprising:

a first rectifier coupled to a first power supply of the DC voltage link and the NP terminal to generate the first voltage with a first alternative current (AC) current from a first secondary winding; and

a second rectifier coupled to a second power supply of the DC voltage link and the NP terminal to generate the second voltage with a second AC current from a second secondary winding.
A method (200) for manufacturing a DC voltage chopper device, comprising:

providing (202) a first chopper circuit configured to be coupled between a first DC voltage line (Vdc) of a DC voltage link and a neutral point (NP) terminal, the first chopper circuit comprising:

a first resistor, and

a first switch coupled to the first resistor and configured to flow a first current caused by an overvoltage of the DC voltage link.