阅读说明：本技术 电组合件 (Electrical assembly ) 是由 C·C·戴维森 A·诺兰 A·J·博内特 于 2020-02-05 设计创作，主要内容包括：一种电组合件包括多个模块(36),每个模块(36)包括至少一个开关元件(38)和至少一个能量存储装置(40),每个模块(36)中的所述或每个开关元件(38)和所述或每个能量存储装置(40)被布置成可组合以选择性地提供电压源,其中每个模块(36)包括相应的传感器(46),所述相应的传感器(46)配置成监测所述多个模块(36)中的至少一个其他模块,每个传感器(46)配置成选择性地检测所述或每个对应的被监测模块(36)中的操作危险的发生。(An electrical assembly comprising a plurality of modules (36), each module (36) comprising at least one switching element (38) and at least one energy storage device (40), the or each switching element (38) and the or each energy storage device (40) in each module (36) being arranged to be combinable to selectively provide a voltage source, wherein each module (36) comprises a respective sensor (46), the respective sensor (46) being configured to monitor at least one other module in the plurality of modules (36), each sensor (46) being configured to selectively detect the occurrence of an operational hazard in the or each corresponding monitored module (36).)

1. An electrical assembly (20) comprising a plurality of modules (36), each module (36) comprising at least one switching element (38) and at least one energy storage device (40), the or each switching element (38) and the or each energy storage device (40) in each module (36) being arranged to be combinable to selectively provide a voltage source, wherein each module (36) comprises a respective sensor (46), the respective sensor (46) being configured to monitor at least one other module of the plurality of modules (36), each sensor (46) being configured to selectively detect the occurrence of an operational hazard in the or each corresponding monitored module (36).

2. The electrical assembly (20) of claim 1, wherein at least one sensor (46) of the plurality of sensors (46) is configured to monitor two or more other modules of the plurality of modules (36), and/or at least one module (36) of the plurality of modules (36) is monitored by two or more sensors (46) of the plurality of sensors (46).

3. The electrical assembly (20) according to any one of the preceding claims, further comprising a controller (52), the controller (52) configured to communicate with the plurality of sensors (46), wherein the controller (52) is configured to trigger a protection function of the electrical assembly (20) in response to detection of an occurrence of an operational hazard in at least one module (36) of the plurality of modules (36).

4. The electrical assembly (20) of claim 3, wherein the controller (52) is configured to trigger a protection function of the electrical assembly (20) only in response to a plurality of detections of an occurrence of an operational hazard in at least one module (36) of the plurality of modules (36).

5. The electrical assembly (20) according to claim 3 or claim 4, wherein the controller (52) is configured to trigger a first protection function of the electrical assembly (20) in response to detection of a first number of occurrences of operational hazards in at least one module (36) of the plurality of modules (36), the first protection function being an alarm notification, and wherein the controller (52) is configured to trigger a second protection function of the electrical assembly (20) in response to detection of a second number of occurrences of operational hazards in at least one module (36) of the plurality of modules (36), the second protection function being a deactivation of one or more modules (36) of the plurality of modules (36), the second number being higher than the first number.

6. The electrical assembly (20) according to any one of claims 3 to 5, wherein the controller (52) is configured to trigger a protective function of the electrical assembly (20) in response to detection of an occurrence of an operational hazard in at least one of the plurality of modules (36) in combination with detection of an occurrence of the same operational hazard by one or more sensors (46) external to the module (36).

7. The electrical assembly (20) according to any one of the preceding claims, wherein the plurality of modules (36) includes a first set of modules (36) and a second set of modules (36), the first set of modules (36) and the second set of modules (36) being arranged to face each other, the sensor (46) of each module (36) of the first set of modules (36) being configured to monitor at least one module (36) of the modules (36) of the second set of modules (36), the sensor (46) of each module (36) of the second set of modules (36) being configured to monitor at least one module (36) of the modules (36) of the first set of modules (36).

8. The electrical assembly (20) according to any one of the preceding claims, comprising a reflective surface (48), the reflective surface (48) being arranged such that the sensor (46) in at least one module (36) of the plurality of modules (36) is configured to monitor the or each corresponding monitored module (36) by reflection of the or each corresponding monitored module (36).

9. The electrical assembly (20) according to any one of the preceding claims, wherein each sensor (46) comprises an infrared radiation detector, a fire sensor, an ultraviolet radiation detector and/or an arcing sensor.

10. The electrical assembly (20) according to any one of the preceding claims, wherein each sensor comprises a near field arcing sensor.

11. The electrical assembly (20) of claim 10 when dependent on claim 3, wherein the controller (52) is configured to trigger a protection function of the electrical assembly (20) only in response to a plurality of detections of an occurrence of arcing in at least one module (36) of the plurality of modules (36).

12. The electrical assembly (20) according to any one of the preceding claims, wherein each module (36) is configured to communicate with at least one other module of the plurality of modules (36) such that switching of a switching component of the module (36) in communication is synchronized to minimize or eliminate interference with detection of the operational hazard.

13. The electrical assembly (20) according to any one of the preceding claims, wherein each module (36) comprises a switch detector configured to detect switching of at least one switch component (38) of at least one other module of the plurality of modules (36), each module (36) being configured to synchronize switching of its one or more switch components (38) with the detected switching of the one or more switch components (38) of the or each other module (36) to minimize or eliminate interference with the detection of the operational hazard.

14. The electrical assembly (20) according to any one of the preceding claims, wherein the electrical assembly (20) is a converter (20) or a circuit interruption device, preferably wherein the electrical assembly (20) is a converter (20) for DC power transmission and/or reactive power compensation at high or medium voltage.

15. A method of monitoring an electrical assembly (20) comprising a plurality of modules (36), each module (36) comprising at least one switching element (38) and at least one energy storage device (40), the or each switching element (38) and the or each energy storage device (40) in each module (36) being arranged to be combinable to selectively provide a voltage source, the method comprising the steps of:

providing each module (36) with a respective sensor;

monitoring at least one other module (36) of the plurality of modules (36) using the respective sensor (46) in each module (36); and

each sensor (46) is used to selectively detect the occurrence of an operational hazard in the or each corresponding monitored module (36).

Technical Field

The present invention relates to: an electrical assembly comprising a plurality of modules, each module comprising at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module being arranged to be combinable to selectively provide a voltage source; and a method for monitoring such an electrical assembly, preferably for use in medium and high voltage power applications. In particular, the invention may relate to a converter, preferably for DC power transmission and/or reactive power compensation at high or medium voltage.

Background

In power transmission and distribution applications, it is known to use electrical devices based on so-called chain-link modules, each of which is configured to selectively provide a voltage source to facilitate a range of electrical functions, such as power conversion or circuit interruption.

Disclosure of Invention

According to a first aspect of the present invention there is provided an electrical assembly comprising a plurality of modules, each module comprising at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module being arranged to be combinable to selectively provide a voltage source, wherein each module comprises a respective sensor configured to monitor at least one other module in the plurality of modules, each sensor being configured to selectively detect the occurrence of an operational hazard in the or each corresponding detected module.

The configuration of the plurality of modules may vary at the module level. In an example, one or more of the plurality of modules may take the form of a half-bridge module comprising a pair of switching elements connected in parallel with an energy storage device in a half-bridge arrangement to define a 2-quadrant unipolar module that may provide zero or positive voltage and may conduct current in two directions. In another example, one or more of the plurality of modules may take the form of a full bridge module comprising two pairs of switching elements connected in parallel with the energy storage device in a full bridge arrangement to define a 4-quadrant bipolar module capable of providing a negative, zero or positive voltage and capable of conducting current in two directions.

Furthermore, some or all of the plurality of modules may be electrically connected in series to define a chain-link converter, but may also be electrically connected to each other in other ways to define various circuit topologies.

There are various ways in which each sensor may be included in a corresponding module. Each sensor may be integrated, mounted, or built into the structure of the corresponding module, such as the housing or other structural features of the corresponding module.

For the purposes of this specification, operational risk is intended to mean a risk or risk of having or causing a deleterious effect on the operation of a module. Examples of operational hazards include, but are not limited to, fire and arcing (arc). Examples of detrimental effects include, but are not limited to, physical or electrical damage to one or more components of the module, diminished functionality of one or more components of the module, and a reduction in ratings of one or more components of the module.

Each sensor may be configured to detect the occurrence of an operational hazard by sensing one or more characteristics or events associated with the occurrence of the operational hazard.

Including a respective sensor in each module to monitor at least one other module of the plurality of modules provides improved sensor coverage (coverage) as compared to using an external sensor that relies on line of sight to detect operational hazards (e.g., camera, ultraviolet radiation detector, infrared radiation detector, etc.). This is because the plurality of modules may be arranged such that one or more of the plurality of modules cannot be easily viewed by a line-of-sight sensor external to the electrical assembly. This is especially true when multiple modules are arranged in a long straight line.

Configuring the respective sensor of each module to monitor at least one other module of the plurality of modules improves reliability in detecting operational hazards in the electrical assembly by avoiding problems associated with configuring each sensor to monitor only the module that includes the sensor. More particularly, when each sensor is configured to monitor only the module comprising that sensor, the failure of a single sensor may lead not only to a failure that is dangerous to detect operation, but also to a false positive detection of the operational danger, which may lead to an interruption of the normal operation of the electrical assembly due to, for example, a premature triggering of the protective function of the electrical assembly. Furthermore, when a given sensor is configured to monitor only the module that includes the sensor, the sensor is exposed to operational hazards that occur in the monitored module, thus increasing the risk of sensor failure and thereby reducing the reliability in detecting operational hazards in the electrical assembly. While it may be possible to customize each sensor to improve its reliability in monitoring only the module comprising the sensor and at the same time avoid the above-mentioned problems, this would result in a more complex sensor design and thus a more expensive solution for detecting the occurrence of operational hazards in the module of the electrical assembly.

In addition, configuring the respective sensor of each module to monitor at least one other module of the plurality of modules allows the electrical assembly of the present invention to be configured to provide a reliable and sensitive operational hazard detection system with built-in redundancy. For example, at least one of the plurality of sensors may be configured to monitor two or more other modules of the plurality of modules, and/or at least one of the plurality of modules may be monitored by two or more of the plurality of sensors. This not only provides redundancy in the monitoring of each module, but can also be used to reduce the likelihood of false positive detections by requiring multiple detections in sequence for operational hazards that will be deemed to have occurred. This in turn reduces the reliability requirements of each sensor and thereby provides for the use of relatively inexpensive off-the-shelf sensors.

The electrical assembly of the present invention may further comprise a controller configured to communicate with the plurality of sensors, wherein the controller is configured to trigger a protection function of the electrical assembly in response to detection of an occurrence of an operational hazard in at least one of the plurality of modules.

The controller may take the form of a global controller configured to communicate with each of the plurality of sensors. The controller may be configured to communicate with one or more of the plurality of sensors via a direct communication link and/or communicate with one or more of the plurality of sensors via an indirect communication link.

For the purposes of this specification, the protective function of an electrical assembly is intended to mean the operation of the electrical assembly that eliminates, limits, or prevents deleterious effects on the affected module(s).

Examples of protection functions of the electrical assembly include, but are not limited to, deactivation (deactivation) of one or more of the plurality of modules and alarm notification. Examples of deactivation of one or more of the plurality of modules include, but are not limited to, tripping the electrical assembly through the use of a circuit interrupting device, electrical bypass of one or more modules, and electrical isolation of one or more modules. Examples of alert notifications include, but are not limited to, audio alerts, visual alerts, and electronic alerts sent to remote units such as computers and handheld devices.

In such embodiments employing the controller, the controller may be configured to trigger the protective function of the electrical assembly only in response to a plurality of detections of the occurrence of an operational hazard in at least one of the plurality of modules.

Configuring the controller in this manner reduces the risk of a false positive detection triggering the protection function, which would interrupt normal operation of the electrical assembly.

In further such embodiments employing the controller, the controller may be configured to trigger a first protection function of the electrical assembly in response to detection of a first number of occurrences of operational hazards in at least one of the plurality of modules, the first protection function being an alarm notification, and wherein the controller may be configured to trigger a second protection function of the electrical assembly in response to detection of a second number of occurrences of operational hazards in the at least one of the plurality of modules, the second protection function being deactivation of one or more of the plurality of modules, the second number being higher than the first number.

Configuring the controller in this manner enables the electrical assembly to provide an early warning of operational hazards occurring in at least one of the plurality of modules upon reaching the first number of detections before automatically deactivating the affected module(s) upon reaching the higher second number of detections. This allows the electrical assembly to minimize false positive detection (or multiple false positive detections) that cause unnecessary interruptions in the normal operation of the electrical assembly, and at the same time alert the operator that an operational hazard may occur.

In an embodiment of the invention, the controller may be configured to trigger the protection function of the electrical assembly in response to the detection of the occurrence of an operational hazard in at least one of the plurality of modules in combination with the detection of the occurrence of the same operational hazard by one or more sensors external to the module. This results in a coordinated operational hazard detection system that may be configured to detect a wider range of operational hazards.

Each sensor may be configured to monitor at least one module disposed opposite, adjacent, or proximate to the module that includes the sensor. Further, each sensor may be configured to monitor at least one module in a line of sight of the module that includes the sensor.

In further embodiments of the invention, the plurality of modules may include a first set of modules and a second set of modules, the first set of modules and the second set of modules being arranged to face each other, the sensor of each module of the first set of modules being configured to monitor at least one module of the modules of the second set of modules, the sensor of each module of the second set of modules being configured to monitor at least one module of the modules of the first set of modules.

In still further embodiments of the invention, the electrical assembly may comprise a reflective surface, for example a mirror (mirror), arranged such that the sensor of at least one of the plurality of modules is configured to monitor the or each corresponding monitored module by reflection of the or each corresponding monitored module. This is particularly useful for monitoring any module that cannot be viewed through any module sensor that relies on line of sight.

Each sensor may include an infrared radiation detector, a fire sensor, an ultraviolet radiation detector, and/or an arcing sensor. The fire sensor may be, for example, an infrared radiation detector. The arc sensor may be, for example, an ultraviolet radiation detector or a near field arcing sensor.

Each module may include multiple sensors of the same type, multiple sensors of different types, and/or one or more hybrid sensors configured to detect different operational hazards.

In embodiments of the invention employing a sensor in the form of a near field arc sensor, the controller may be configured to trigger the protection function of the electrical assembly only in response to a plurality of detections of the occurrence of arcing in at least one of the plurality of modules. This not only reduces the likelihood of false positive detections by requiring multiple near field arc sensors to detect the same operational hazard, but also makes it easier to pinpoint (pinpoint) the precise module in which the operational hazard is occurring.

Optionally, each module may be configured to communicate with at least one other module of the plurality of modules such that the switches of the switching assemblies of the communicating modules are synchronized to minimize or eliminate interference with the detection of the operational hazard.

Each module may be configured to communicate with one or more other modules via direct communication links and/or with one or more other modules via indirect communication links. Each module may be configured to communicate with one or more other modules via a global communication system.

The ability to synchronize the switching of the switching components of the module provides a quiet electrical environment that helps detect the occurrence of operational hazards.

Further optionally, each module may comprise a switch detector, for example a radio receiver, configured to detect switching of at least one switching component of at least one other module of the plurality of modules, each module being configured to synchronize switching of its one or more switching components with the detected switching of the one or more switching components of the or each other module to minimise or eliminate interference with detection of an operational hazard. This configuration is particularly useful when communication between modules is not available due to communication failure or by design.

The invention is applicable to a wide range of electrical devices and apparatus requiring the use of a plurality of modules, each module comprising at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module being arranged to be combinable to selectively provide a voltage source. For example, the electrical assembly may be a converter or a circuit interrupting device, such as a hybrid DC circuit breaker. In particular, the electrical assembly may be a converter for DC power transmission and/or reactive power compensation at high or medium voltage.

According to a second aspect of the present invention there is provided a method of monitoring an electrical assembly comprising a plurality of modules, each module comprising at least one switching element and at least one energy storage device, the or each switching element and the or each energy storage device in each module being arranged to be combinable to selectively provide a voltage source, the method comprising the steps of:

providing each module with a respective sensor;

monitoring at least one other module of the plurality of modules using a respective sensor in each module; and

each sensor is used to selectively detect the occurrence of an operational hazard in the or each corresponding monitored module.

The features and advantages of the electrical assembly of the first aspect of the invention and its embodiments apply mutatis mutandis to the method of the second aspect of the invention and its embodiments.

In the method of the present invention, at least one of the plurality of sensors may be used to monitor two or more other modules of the plurality of modules, and/or at least one of the plurality of modules may be monitored by two or more of the plurality of sensors.

The method of the present invention may comprise the step of triggering a protection function of the electrical assembly in response to the detection of the occurrence of an operational hazard in at least one of the plurality of modules.

In such embodiments, the method of the present invention may comprise the step of triggering the protection function of the electrical assembly only in response to a plurality of detections of the occurrence of an operational hazard in at least one of the plurality of modules.

In further such embodiments, the method of the present invention may comprise the steps of:

triggering a first protection function of the electrical assembly in response to detection of a first number of operational hazards occurring in at least one of the plurality of modules, the first protection function being an alarm notification; and

triggering a second protection function of the electrical assembly in response to detection of a second number of occurrences of operational hazards in at least one of the plurality of modules, the second protection function being deactivation of one or more of the plurality of modules, the second number being higher than the first number.

In still other such embodiments, the method of the present invention may comprise the steps of: in response to the detection of the occurrence of an operational hazard in at least one of the plurality of modules in combination with the detection of the occurrence of the same operational hazard by one or more sensors external to the module, triggering a protection function of the electrical assembly.

In the method of the present invention, the plurality of modules may include a first group of modules and a second group of modules, the first group of modules and the second group of modules being arranged to face each other, and the method may include the steps of:

monitoring at least one module of a second set of modules using the sensors of each module of the first set of modules; and

at least one of the modules of the first set of modules is monitored using the sensors of each module of the second set of modules.

In the method of the invention, the electrical assembly may comprise a reflective surface, and the method may comprise the steps of: monitoring the or each corresponding monitored module using the sensor of at least one of the plurality of modules by reflection of the or each corresponding monitored module from the reflective surface.

In the method of the invention, each sensor may comprise an infrared radiation detector, a fire sensor, an ultraviolet radiation detector and/or an arcing sensor.

In the method of the present invention, each sensor may comprise a near field arcing sensor.

The method of the invention may comprise the steps of: the protection function of the electrical assembly is triggered only in response to a plurality of detections of an occurrence of arcing in at least one of the plurality of modules.

The method of the invention may comprise the steps of: the switches of the switching components of the modules are synchronized to minimize or eliminate interference with the detection of operational hazards.

The method of the invention may comprise the steps of: each module is configured to communicate with at least one other module of the plurality of modules such that switching of the switching components of the communicating modules is synchronized to minimize or eliminate interference with detection of operational hazards.

The method of the invention may comprise the steps of:

providing each module with a respective switch detector;

detecting a switch of at least one switching component of at least one other module of the plurality of modules using the respective switch detector of each module; and

each module is configured to synchronise the switching of its one or more switching assemblies with the detected switching of the one or more switching assemblies of the or each other module to minimise or eliminate interference with the detection of operational hazards.

In the method of the invention, the electrical assembly may be a converter or a circuit interruption device, preferably wherein the electrical assembly is a converter for DC power transmission and/or reactive power compensation at high or medium voltage.

It will be appreciated that the use of the terms "first" and "second", etc. in this patent specification are merely intended to help distinguish between similar features (e.g., first and second sets of modules), and are not intended to indicate the relative importance of one feature to another unless otherwise specified.

Drawings

Preferred embodiments of the invention will now be described, by way of non-limiting example, with reference to the accompanying drawings, in which:

fig. 1 shows a voltage source converter according to an embodiment of the invention;

fig. 2 shows a switching valve of the voltage source converter of fig. 1;

fig. 3 shows a top view of an arrangement of switching valves of the voltage source converter of fig. 1;

FIG. 4 shows a half bridge module for use in the switching valve of FIGS. 2 and 3; and

fig. 5 shows a full bridge module for use in the switching valve of fig. 2 and 3.

The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic for clarity and conciseness.

Detailed Description

The following embodiments of the invention are primarily for use in High Voltage Direct Current (HVDC) applications, but it will be appreciated that the following embodiments of the invention are applicable, mutatis mutandis, to other applications operating at different voltage levels, for example medium voltage levels. It will be further appreciated that the following embodiments of the invention are described with reference to a converter for DC power transmission and/or reactive power compensation, but are applicable mutatis mutandis to other types of electrical devices, such as a hybrid DC circuit breaker.

A voltage source converter according to an embodiment of the invention is shown in fig. 1 and is generally indicated by reference numeral 20.

The voltage source converter 20 comprises first and second DC terminals 22, 24 and a plurality of converter branches. Each converter limb extends between first and second DC terminals 22, 24 and comprises first and second limb portions separated by a respective AC terminal 26. In each converter limb, a first limb portion extends between the first DC terminal 22 and the AC terminal 26, and a second limb portion extends between the second DC terminal 24 and the AC terminal 26.

In use, the first and second DC terminals 22, 24 of the voltage source converter 20 are connected to a DC network 28, and the AC terminal 26 of each converter limb of the voltage source converter 20 is connected to a respective AC phase of a three-phase AC network 30 via a transformer arrangement 32.

Each limb portion includes a switching valve 34 in the form of a chain-link converter defined by a plurality of series-connected modules 36. Each module 36 comprises a plurality of switching elements 38 and at least one capacitor 40, the plurality of switching elements 38 and the or each capacitor 40 in each such module 36 being arranged to be combinable to selectively provide a voltage source. Each switching valve 34 may include up to several hundred modules.

Fig. 2 shows a perspective view of the on-off valve 34. The on-off valve 34 includes two modular container (containment) tower structures 42, each of the modular container tower structures 42 resembling a rectangular box. The modular vessel tower structures 42 are arranged side-by-side such that their longer sides face each other. Each modular vessel tower structure 42 houses a plurality of rows of modules 36, wherein each row extends along a longer side of the corresponding modular vessel structure, and wherein the plurality of rows of modules 36 are stacked on top of each other. The power electronics of each module 36 are preferably located outside of the corresponding module container tower structure 42 for ease of maintenance.

Fig. 3 shows a top view of six switching valves 34 of the voltage source converter. The six on-off valves 34 are arranged in a row such that there are two outer on-off valves 34 arranged at both ends of the row, and four inner on-off valves 34 arranged between the two outer on-off valves 34. For two outer on-off valves 34, one longer side faces the longer side of the adjacent on-off valve 34, and the other longer side faces the wall 44. For four internal switching valves 34, one longer side faces the longer side of the adjacent switching valve 34, and the other longer side faces the longer side of the other adjacent switching valve 34.

Each module 36 may vary in topology, examples of which are described below.

Fig. 4 schematically shows the structure of an exemplary module 36 in the form of a half-bridge module 36 a. The half-bridge module 36a includes a pair of switching elements 38 and a capacitor 40. The pair of switching elements 38 are connected in parallel with a capacitor 40 in a half-bridge arrangement to define a 2-quadrant unipolar module 36a, which 2-quadrant unipolar module 36a may provide zero or positive voltage and may conduct current in both directions.

Fig. 5 schematically shows the structure of an exemplary module 36 in the form of a full bridge module 36 b. The full bridge module 36b includes two pairs of switching elements 38 and capacitors 40. The pair of switching elements 38 are connected in parallel with a capacitor 40 in a full-bridge arrangement to define a 4-quadrant bipolar module 36b, which 4-quadrant bipolar module 36b can provide a negative, zero or positive voltage and can conduct current in both directions.

Each switching element 38 takes the form of an Insulated Gate Bipolar Transistor (IGBT) connected in parallel with an anti-parallel diode. It is envisaged that in other embodiments of the invention each IGBT may be replaced by a gate turn-off thyristor, a field effect transistor, an injection enhanced gate transistor, an integrated gate commutated thyristor or any other self-commutated semiconductor device. It is also contemplated that in other embodiments of the present invention, each IGBT may be replaced by a plurality of series-connected IGBTs, and/or each diode may be replaced by a plurality of series-connected diodes.

It is also contemplated that in still other embodiments of the present invention, each capacitor 40 may be replaced by a different type of energy storage device (e.g., a battery or fuel cell) capable of discharging and storing energy to selectively provide a voltage.

By changing the state of the switching elements 38, the capacitor 40 of each module 36 is selectively bypassed or inserted into the corresponding chain-link converter. This selectively directs current through the capacitor 40 or causes current to bypass the capacitor 40 so that the module 36 provides a zero or positive voltage in the case of the half-bridge module 26a and a negative, zero or positive voltage in the case of the full-bridge module 36 b.

It is possible to establish a combined voltage across each chain-link converter that is higher than each available voltage from its individual module 36 via inserting capacitors 40 of a plurality of modules 36, each providing its own voltage, into each chain-link converter. In this way, the switching of the switching elements 38 in each module 36 causes each chain-link converter to provide a stepped variable voltage source, which allows the generation of a voltage waveform across each chain-link converter using a step-wise approximation. Thus, the switching element 38 in each switching valve 34 is switchable to selectively allow and inhibit current flow through the corresponding capacitor 40 in order to control the voltage across the corresponding branch portion. This in turn allows power to be transferred between the DC and AC networks 28, 30 through the switching of the switching elements 38 of the modules 36 using the voltage source converter 30 to provide a stepped variable voltage source and thereby generate voltage waveforms so as to control the configuration of the AC voltage waveforms at the corresponding AC terminals 26 to facilitate the transfer of power between the DC and AC networks 28, 30.

During operation of the voltage source converter 20, a fire may occur in one or more modules 36 of the voltage source converter 20. Since the gap between adjacent switching valves 34 is significantly smaller than the length of the longer sides of the switching valves 34, it may be difficult to detect the occurrence of a fire in any module 36, which module 36 is visually hidden from view sensors outside the voltage source converter 20.

In order to achieve a reliable detection of any fire occurrence in the module 36, the voltage source converter 20 comprises a fire detection system configured as follows.

Each module includes a respective sensor 46 in the form of an infrared radiation detector.

In each internal switching valve 34, each sensor 46 faces outwardly toward the corresponding modular vessel tower structure 42 so as to face the plurality of modules 36 adjacent the internal switching valve 34. In the modular vessel tower structure 42 of the external on-off valve 34 facing the internal on-off valve 34, each sensor 46 faces outwardly toward the corresponding modular vessel tower structure 42 so as to face the plurality of modules 36 adjacent to the internal on-off valve 34. In the modular vessel tower structure 42 facing the external on-off valves 34 of the walls 44, a mirror 48 is arranged on each wall 44 such that each sensor 46 faces the reflection of a plurality of modules 36 of the same modular vessel tower structure 42. Fig. 3 illustrates a sensor cover 50 for some of the sensors 46 in each on-off valve 34.

In this manner, each sensor 46 of each on-off valve 34 is able to monitor for the occurrence of a fire in a plurality of other modules 36, and each module 36 is monitored by a plurality of sensors 46.

Alternatively, for a modular vessel tower structure 42 of an external on-off valve 34 facing an internal on-off valve 34, an additional infrared radiation sensor (not shown) may be mounted on the wall 44 such that the additional infrared radiation sensor faces the module 36 of the external on-off valve 34. In this way, the occurrence of a fire in the module 36 of the external switching valve 34 can be detected by using an additional infrared radiation sensor.

The voltage source converter 20 also includes a controller 52 configured to communicate with the plurality of sensors 46. Upon detecting infrared radiation above a certain level corresponding to the occurrence of a fire, each sensor 46 transmits an electrical signal to the controller 52 indicating the occurrence of a fire. Upon receiving the electrical signal, the controller 52 triggers a protection function of the voltage source converter 20, such as issuing an alarm notification or tripping the voltage source converter 20.

To reduce the risk of false positive detection, the controller 52 is preferably configured to trigger the protection function only in response to the plurality of sensors 46 detecting a fire occurring in the affected module 36. It is further preferred that controller 52 be configured to provide an early warning of a fire occurring in an affected module 36 prior to automatically deactivating the affected module 36. This is accomplished by configuring the controller 52 to first issue an alarm notification upon receiving a signal from the sensor 46 corresponding to a first number of detections of a fire in the affected module 36 (e.g., 2-3 detections), and then trip the voltage source converter 20 in response to a second, higher number of detections of a fire in the affected module 36 (e.g., 4 or more detections).

Alternatively, the controller 52 may be configured to trigger the protection function of the voltage source converter 20 in response to detection of a fire occurrence in the affected module 36 in combination with detection of the same fire occurrence by one or more sensors 46 external to the module 36.

The inclusion of a respective sensor 46 in each module 36 to monitor a plurality of other modules 36 not only enables reliable monitoring of all modules 36 regardless of the length of the longer side of the on-off valve 34, but also improves reliability in detecting a fire in the voltage source converter 20 by avoiding the aforementioned problems associated with configuring each sensor 46 to monitor only the module 36 including that sensor 46. In addition, configuring the respective sensors 46 of each module 36 to monitor a plurality of other modules 36 results in a reliable and sensitive fire detection system with built-in redundancy. This not only provides redundancy in the monitoring of each module 36, but may also serve to reduce the likelihood of false positive detections by requiring multiple detections in sequence for a fire to be considered to have occurred. This in turn enables the use of a simpler and less expensive off-the-shelf sensor 46.

The on-off valve may be arranged in a different manner than the embodiment shown in fig. 2 and 3.

In one example, the on-off valve may comprise a plurality, e.g. 4-6 in number, of modular vessel tower structures arranged in a line. Each modular vessel tower structure may have a square aspect ratio. In such a switching valve, each modular vessel tower structure may house a respective plurality of modules, and electrical connections may be made between the modular vessel tower structures to define a series connection of modules of the modular vessel tower structure. A plurality of such on-off valves may be arranged in a row such that there are two external on-off valves arranged at both ends of the row, and one or more internal on-off valves arranged between the two external on-off valves. In this way, the sensor of each module may be configured to monitor a plurality of other modules, in particular one or more modules in the adjacent module container tower structure(s) of the same on-off valve and/or one or more modules in at least one module container tower structure of the adjacent on-off valve(s). With respect to the latter, preferably, the sensor of each module may be configured to monitor one or more modules in the nearest modular vessel tower structure of the adjacent on-off valve(s).

It will be appreciated that in other embodiments of the invention, the sensors 46 of the above-described embodiments may be configured to detect other types of operational hazards in the module 36.

In one such example, each sensor 46 may take the form of a near field arc sensor 46 rather than an infrared radiation detector. Arcing in the on-off valve 34 is a fire hazard. It is therefore important to precisely locate the module 36 where the arc is occurring so that it can be removed. It will be appreciated that an ultraviolet radiation detector may be used to sense the occurrence of arcing in module 36.

Each near field arc sensor 46 is configured as a radio frequency inductive loop sensor 46 to detect arcing having a frequency of 50 MHz. Each near field arc sensor 46 is typically sensitive to arcs in the range of several meters. This not only enables each near field arc sensor 46 to detect the occurrence of an arc in its own module 36 and adjacent sub-modules 36, but also allows the identification of the arc source to be localized to a small area.

In the event that an arc occurs in a module 36, the arc will be detected by the near field arc sensors 46 of the same module 36 and also by the near field arc sensors 46 of other nearby modules 36. The use of multiple near field arc sensors 46 to detect the same arc occurrence makes it easier to pinpoint the precise module 36 where the arc is occurring. Moreover, by configuring the controller 52 to trigger the protection function of the voltage source converter 20 only in response to a plurality of detections of arc occurrences in the affected module 36, the risk of false positive detections may be reduced.

Optionally, the controller 52 may be configured to trigger the protection function of the voltage source converter 20 in response to the detection of an arc occurrence in the affected module 36 in combination with the detection of the same arc occurrence by one or more sensors 46 external to the module 36.

A possible source of interference with the detection of an arc occurrence by the near field arc sensor 46 is switching noise from (a) the high voltage power supply unit (switching regulator) on the adjacent module 36 and (b) the switching of the switching element 38 of the module 36. Accordingly, it is desirable to remove the source of interference in order to provide a quiet electrical environment that facilitates detection of an arc occurrence.

Interference caused by switching noise may be mitigated by communication between modules 36 to enable configuration of modules 36 to achieve synchronization between switching operations of oscillators of switching regulators and/or switching of switching elements 38 of modules 36. When communication between modules 36 is not available, a radio receiver (not shown) in each module 36 may be used to detect the switching operation of the switching regulator of an adjacent module 36 in order to enable the configuration of the modules 36 to achieve synchronization between the switching operations of the oscillator of the switching regulator.