Abstract: Techniques and solutions are described for implementing virtual table schemas. A virtual table schema includes a logical pointer that is used to target a table that includes data and is defined according to the virtual table schema. Values assigned to the logical pointer can be used to target tables at different locations, such as in-memory storage or in dynamic storage of a database management system. The dynamic storage includes an in-memory buffer cache and persistent storage. The logical pointer can be updated to point to the in-memory storage or the dynamic storage, including based on use statistics. Similarly, a table having data for the virtual table can be transitioned between the in-memory buffer cache and the persistent storage, including based on use statistics for the virtual table. A value for the logical pointer can be updated when the table is transferred between the in-memory buffer cache and the dynamic storage.

Abstract: Provided is a hybrid control device for a static synchronous compensator (STATCOM), the device including: a first arithmetic operation unit calculating the deviation between a reference voltage desired to be controlled by the STATCOM and output voltage to be output so as to output the same; a proportional integral (PI) controller performing PI control on the deviation output from the first arithmetic operation unit within a range between a new inductive reactive current maximum value and a new capacitive reactive current maximum value, so as to output a reactive current output value; and a second arithmetic operation unit adding the preset reactive current set value to the reactive current output value output from the PI control unit so as to output a reactive current reference value.

Abstract: Systems and methods for generating a metadata log in a database recovery system include generating, at its primary system, a metadata log for a logging period. A change applied to a metadata object accessible from the primary system is detected, and upon detection, the system identifies a pair of a unique metadata identifier and a metadata type for the changed metadata object and determines a metadata structure of the changed metadata object. A data exchange object for the metadata structure is generated and a data exchange element from the data exchange object is created. The metadata log is updated with log information that includes the data exchange element and the pair, which is associated with the data exchange element. Upon the logging period ending, the metadata log is transmitted to a secondary system of the database recovery system for replaying. Related apparatus, systems, techniques and articles are also described.

Abstract: Proposed is a power supply device for a submodule controller of a modular multilevel converter (MMC) connected to a high voltage direct current (HVDC) system, which generates and supplies power through by hydraulic turbine generation using coolant flowing through a heat sink that cools a submodule. The power supply device includes a heat sink disposed inside the submodule of the MMC converter to cool the submodule using coolant; a pipe having an inlet configured to supply the coolant to the heat sink and an outlet configured to discharge the coolant to outside of the heat sink and configured to form a flow path to cause the coolant supplied through the inlet to flow to the heat sink; and a hydraulic turbine generator disposed at one side of the pipe to generate power by the coolant flowing through the pipe and supply the power to the submodule controller.

Abstract: Technologies are described for performing replication of data within a database environment having a source node and a replica node. The source node executes a database operation on at least one database table stored by the source node. The source node asynchronously sends the database operation to the replica node. A prepare commit request is synchronously sent from the source node to the replica node. The source node receives a synchronous precommit acknowledgement from the replica node. The precommit acknowledgement indicates that the database operation was executed at the replica node. The source node commits a transaction associated with the database operation.

Abstract: A modular multilevel converter (MMC) converter including an auxiliary sub-module provided between an upper converter arm and a lower converter arm of the MMC converter is provided. An MMC converter includes an auxiliary sub-module including: an energy storage unit storing a DC voltage in the sub-module; a first semiconductor switch connected to the energy storage unit; a second semiconductor switch connected to the first semiconductor switch; a third semiconductor switch connected to the second semiconductor switch; and a switching controller turning ON/OFF the first to third semiconductor switches, wherein a mid-point between the first and second semiconductor switches is connected to the sub-module of the upper converter arm, a mid-point between the second and third semiconductor switches is connected to a load connection terminal, and a mid-point between the third semiconductor switch and the energy storage unit is connected to the sub-module of the lower converter arm.

Abstract: Technologies are described for performing replication of data within a database environment having a source node and a replica node. The source node executes a database operation on at least one database table stored by the source node. The source node asynchronously sends the database operation to the replica node. A prepare commit request is synchronously sent from the source node to the replica node. The source node receives a synchronous precommit acknowledgement from the replica node. The precommit acknowledgement indicates that the database operation was executed at the replica node. The source node commits a transaction associated with the database operation.

Abstract: Technologies are described for facilitating transaction processing within a database environment. A commit protocol provides for the atomic commit or rollback of a transaction that includes an operation that modifies a metadata entity of the database system and one or more other operations that modify metadata entities or data records of the database system. Innovations are provided for detecting and resolving deadlocks that may arise during transaction processing. Innovations are also provided for providing versioning of metadata entities, including invalidating metadata entities cached at a slave node during the commit at a master node of a transaction that creates a new version of the metadata entity.

Abstract: Provided is a hybrid control device for a static synchronous compensator (STATCOM), the device including: a first arithmetic operation unit calculating the deviation between a reference voltage desired to be controlled by the STATCOM and output voltage to be output so as to output the same; a proportional integral (PI) controller performing PI control on the deviation output from the first arithmetic operation unit within a range between a new inductive reactive current maximum value and a new capacitive reactive current maximum value, so as to output a reactive current output value; and a second arithmetic operation unit adding the preset reactive current set value to the reactive current output value output from the PI control unit so as to output a reactive current reference value.

Abstract: A modular multilevel converter (MMC) converter including an auxiliary sub-module provided between an upper converter arm and a lower converter arm of the MMC converter is provided. An MMC converter includes an auxiliary sub-module including: an energy storage unit storing a DC voltage in the sub-module; a first semiconductor switch connected to the energy storage unit; a second semiconductor switch connected to the first semiconductor switch; a third semiconductor switch connected to the second semiconductor switch; and a switching controller turning ON/OFF the first to third semiconductor switches, wherein a mid-point between the first and second semiconductor switches is connected to the sub-module of the upper converter arm, a mid-point between the second and third semiconductor switches is connected to a load connection terminal, and a mid-point between the third semiconductor switch and the energy storage unit is connected to the sub-module of the lower converter arm.

Abstract: An MMC converter linked to a HVDC system and a sub-module are proposed. The sub-module includes: first and second power semiconductor switches serially connected in the same direction, each including a semiconductor switch and a diode connected in anti-parallel to the semiconductor switch; a capacitor parallelly connected to the first and second power semiconductor switches serially connected; a first terminal connected to a first node between the first and second power semiconductor switches; a second terminal connected to a second node between the second power semiconductor switch and the capacitor; a third power semiconductor switch of which a side is connected to the second node, the third power semiconductor switch including a semiconductor switch and a diode connected in anti-parallel to the semiconductor switch; and a third terminal connected to a terminal of an AC grid system and connected to the other side of the third power semiconductor switch.

Abstract: Disclosed is a display module including a transparent display panel and a frame to fix a side of the transparent display panel, wherein the frame has a communication unit to receive data from the outside, a controller to process the received data and to output a drive command corresponding to the processed data and a display drive unit to drive the transparent display panel in response to the drive command from the controller. A display system includes a system body and a display module detachably mounted in the system body.

Abstract: Technologies are described for facilitating transaction processing within a database environment. A commit protocol provides for the atomic commit or rollback of a transaction that includes an operation that modifies a metadata entity of the database system and one or more other operations that modify metadata entities or data records of the database system. Innovations are provided for detecting and resolving deadlocks that may arise during transaction processing. Innovations are also provided for providing versioning of metadata entities, including invalidating metadata entities cached at a slave node during the commit at a master node of a transaction that creates a new version of the metadata entity.

Abstract: Methods and systems are disclosed for managing replication of metadata in a master-slave database environment. While metadata is managed on a master node using database tables with transaction guarantees, metadata copies on the slave node are managed using a lightweight key-value store. In exemplary embodiments, master metadata database tables are mapped to respective key-value structures at one or more slave nodes. The key-value structures have entries pointing to respective metadata objects, which include copies of metadata items stored in the master metadata database tables. The key-value structures can be hierarchically organized under a parent key-value structure. Metadata object versions can be organized as a linked list to facilitate multi-version concurrency control. Methods are disclosed for building the key-value store, for retrieving metadata from the store, for updating the store, for providing multi-version concurrency control, and for pruning obsolete metadata versions. Variants are disclosed.

Abstract: Provided is an electric device including: a main body comprising a storage chamber with an opening; a door coupled to the main body and comprising a transparent display panel such that the transparent display panel covers at least a part of the opening when the door is closed; a movement detector being configured to detect a movement of the transparent display panel and output a movement detection signal corresponding to the movement; and a controller configured to identify a position of the transparent display panel based on the movement detection signal, and control the transparent display panel to reverse an image displayed on the transparent display panel based on the identified position of the transparent display panel being changed from a first position to a second position.

Abstract: Systems and methods for generating a platform-independent metadata catalog framework of a database system are disclosed. These include receiving, at the database system, a metadata object, and determining a version of the received metadata object. Responsive to determining that a metadata catalog, which has catalog entries associated with unique versions of metadata objects, does not include a catalog entry associated with the version of the received metadata object, a catalog entry in the metadata catalog is created. The created catalog entry is then associated with the version of the received metadata object. Furthermore, a version number based on the version of the received metadata is generated, which is associated with the created catalog entry. Related apparatus, systems, techniques and articles are also described.

Abstract: A power supply for a submodule controller of an MMC converter, which supplies driving power to a submodule controller of an MMC connected to an HVDC system. The power supply includes: a bridge circuit unit including an energy storage unit storing a DC voltage of a series-connected submodule of the MMC converter, and multiple power semiconductor devices connected in parallel to the energy storage unit in a bridge form; a first resistor unit connected in parallel to the energy storage unit, and configured with at least one series-connected resistor; a second resistor unit connected in series to the first resistor unit; a switch unit connected in parallel to the first resistor unit; and a DC/DC converter converting a voltage output from output terminals formed in both ends of the second resistor unit into a low voltage, and supplying the same to the submodule controller.

Abstract: Methods and systems are disclosed for managing replication of metadata in a master-slave database environment. While metadata is managed on a master node using database tables with transaction guarantees, metadata copies on the slave node are managed using a lightweight key-value store. In exemplary embodiments, master metadata database tables are mapped to respective key-value structures at one or more slave nodes. The key-value structures have entries pointing to respective metadata objects, which include copies of metadata items stored in the master metadata database tables. The key-value structures can be hierarchically organized under a parent key-value structure. Metadata object versions can be organized as a linked list to facilitate multi-version concurrency control. Methods are disclosed for building the key-value store, for retrieving metadata from the store, for updating the store, for providing multi-version concurrency control, and for pruning obsolete metadata versions. Variants are disclosed.

Abstract: Disclosed is a display module including a transparent display panel and a frame to fix a side of the transparent display panel, wherein the frame has a communication unit to receive data from the outside, a controller to process the received data and to output a drive command corresponding to the processed data and a display drive unit to drive the transparent display panel in response to the drive command from the controller. A display system includes a system body and a display module detachably mounted in the system body.

Abstract: Disclosed herein are system, method, and computer program product embodiments for minimizing table lock duration during lost change resynchronization between a source table and a replica table. An embodiment operates by detecting a restart at a source node or a replica node. A source table at the source node is then locked based on the detection. A database transaction is then created for a lost change resynchronization operation and the source table is unlocked. The database transaction is then compared to another database transaction based on its timestamp. Based on the comparison, either the database transaction for the lost change resynchronization operation or the other database transaction is executed.