Modular time synchronization injection module

Abstract

Modular Time-Synchronized Injection Modules. In the prior art power grid system, power line control is accomplished by a large substation-based system that uses a high voltage (HV) circuit to obtain an injectable impedance waveform that can generate oscillations on the HV power line. Currently, intelligent impedance injection modules (IIMs) are proposed for interactive power line control and line balancing. These IIMs distributed on the high voltage lines or mounted on mobile platforms and connected to the HV power lines generate and inject waveforms locally in an intelligent manner to provide interactive responsiveness to commands from the utility for power line control. These IIMs typically include a plurality of impedance injection units (IIUs), which are transformerless flexible AC transmission systems interconnected in series-parallel connections, and the output pulses are additive and time-synchronized to generate appropriate waveforms that can achieve the desired response and provide interactive power flow control when injected onto the HV transmission line.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 721,749, filed on August 23, 2018, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to reducing harmonic components of impedance injection for balancing and controlling power flow on a power grid by providing a pseudo-sinusoidal voltage established by synchronized injection from a plurality of distributed injection modules that are smoothed into a sine wave by the impedance of a high voltage power line. Background Art

[0004] Most electric utilities use energy management systems (EMS) / supervisory control and data acquisition (SCADA) control systems to control the grid system. Figure 2 Such a generation-distribution system 200 is shown in which a substation-based static synchronous series compensator (SSSC) 204 is connected to the power line 108 and is directly controlled by the utility 206 through a communication line 207 for line balancing. In these cases, both the generator 203 and the load 205 are also shown as being connected at the substation. These control systems provide connection and communication between the power flow control units at the substation 204, from which the distribution load 205 is also connected. These utility control systems are used to limit load imbalances on the power lines of power transmission on the grid. Since the systems are directly controlled by the utility 206, their reaction to disturbances and imbalances on the grid is slow. The systems as indicated are typically substation-based high-power systems that are programmed to inject high voltages onto the high voltage (HV) transmission lines 108.

[0005] These line balancing systems generate and inject impedance as a high power square wave, which will cause harmonic oscillations in the grid because the voltage required by these ground based units to generate and inject for line control is high. Therefore, these systems are usually designed to generate as Figure 2A , the high voltage switches switch at high speed and power to generate a series of square waves of varying amplitudes, which when smoothed provide a sine wave for injection onto the HV transmission line 108. The use of specialized power-hungry high voltage and high speed switches that require high reliability, instantaneous blocking capability, high voltage insulation, and liquid cooling to remove the heat generated when switching makes these substation-based units expensive to operate and maintain.

[0006] In addition to utility-based control of power flow on the HV transmission lines 108 using intelligent impedance injection modules (IIMs) coupled to the power lines, a current move in the industry is to use distributed and localized control. Figure 1 Such an implementation is shown in Figure 1 In FIG. 1 , a HV transmission line 108 connected between a power generation point 104 and a load 106 is suspended from a high voltage tower 110. The figure shows an IIM 102 suspended on the power line in HV operation of the power line. These IIMs with built-in intelligence are able to identify any local power flow control needs and any disturbances on the HV transmission line 108 and provide immediate and effective local corrective actions by generating and injecting corrective impedances onto the HV transmission line.

[0007] A more advanced example of system 200 is shown in Figure 3 200A, as shown, includes a system 200A of distributed impedance injection modules (IIMs) 300 distributed on HV transmission lines 108 between substations 204. The IIMs 300 are directly attached to the HV transmission lines 108 of the grid, which are suspended from HV towers 201 and insulated from the ground. Generators 203 and loads 205 are typically connected to the HV transmission lines 108 of the grid at the substation 204. The IIMs 300 are communicatively connected or coupled to a local intelligence center (LINC) 302 via a high-speed communication link 303, which allows communication and response by the IIMs 300 in the local area at subsynchronous speeds when necessary. The LINC 302 is also connected to other LINCs via high-speed communication links 303 to coordinate the activities of local IIM 300 groups. The supervisory utility 206A monitors the activities of the system 200A using a command and communication link 207 connected to the LINC 302 and the substation 204. The supervisory utility 206A is able to interactively control the local IIM 300 via a communication link connecting the local IIM 300 to the LINC 302 . Figure 4 is a block diagram showing the main components of the intelligent IIM 300. Figure 4 , the IIM 300 includes at least the impedance generation and injection module 100, intelligent control capability 402 having at least a clock with time synchronization capability, and a high-speed communication link 410.

[0008] Figure 5An exemplary transformer coupled IIM 500 is shown having two coupling transformers 506A and 506B that couple the IIM to the HV transmission line 108 to inject impedance onto the HV transmission line 108 for line balancing and interference cancellation. The secondary transformer 501 is used as a sensor unit for any interference on the power line and also extracts power from the power line to provide the necessary power to converters 505A and 505B to generate the required impedance to be injected onto the HV transmission line 108. The generation and injection are controlled by inputs from the sensor and power supply unit 502 to the main controller 503, which provides inputs to controllers 504A and 504B coupled to the respective converters 505A and 505B. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Embodiments of the present disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.

[0010] Figure 1 is a block diagram illustrating a conventional distributed impedance injection module (IIM) directly attached to a HV transmission line.

[0011] Figure 2 is a schematic diagram illustrating a conventional non-distributed control system based on a substation having a static synchronous series compensator (SSSC) for grid control.

[0012] Figure 2A The generation of a pseudo-sinusoidal waveform using high power high frequency switching is shown.

[0013] Figure 3 is a diagram illustrating a conventional power grid system with a distributed and hierarchical intelligent control system.

[0014] Figure 4 is a block diagram illustrating a conventional dynamic smart impedance injection module with local and global time synchronization capabilities.

[0015] Figure 5 is a circuit diagram illustrating a conventional dynamically responsive IIM having a transformer of an HV transmission line coupled to a grid.

[0016] Figure 6 is a circuit diagram illustrating an example of an impedance injection unit (IIU) of a transformer-less flexible alternating current (AC) transmission system (TL-FACTS), wherein one or more IIUs may constitute an impedance injection module IIM.

[0017] Fig. 6A is a circuit diagram illustrating a local master control module of a TL-FACTS based IIU with an associated local clock according to one embodiment.

[0018] Figure 6B is a circuit diagram illustrating a local master control module of a TL-FACTS based IIU having an associated local clock that can be synchronized with a global clock according to one embodiment.

[0019] Figure 7 is a block diagram illustrating an IIM having a series-parallel connection including four TL-FACTS based IIUs according to one embodiment.

[0020] Fig. 7A is another exemplary block diagram of an IIM having, as an example, nine TL-FACTS based IIUs interconnected in a 3×3 matrix as a power flow control subsystem for use in a mobile power flow control application according to another embodiment.

[0021] Figure 7B is an exemplary illustration of a mobile platform having three power flow control subsystems for three high voltage lines of a power grid.

[0022] Figure 7C is an exemplary illustration of subsystems as deployed by a mobile platform and connected to an electrical grid.

[0023] Figure 8 is a block diagram illustrating time delays between groups of exemplary IIMs distributed on an HV transmission line.

[0024] Fig. 9 is a diagram illustrating exemplary smooth sinusoidal waveforms of multiple low impedance / voltage rectangular injection waveforms generated by multiple IIUs.

[0025] Fig.10 is a diagram illustrating an exemplary time synchronized injection of a rectangular waveform onto an HV transmission line to achieve a pseudo-sinusoidal waveform.

[0026] Fig.11 is a diagram illustrating the timing required to generate a pseudo-sine waveform.

[0027] Fig.12 is a diagram illustrating a local master control module having processing capabilities for identifying disturbances on an HV transmission line according to one embodiment.

[0028] Fig.13 is a flow chart of a process for grid system control using synchronous injection of impedance according to one embodiment.

[0029] Fig.14 is a table showing the time delays that need to be synchronized to achieve a pseudo-sinusoidal waveform according to one embodiment. DETAILED DESCRIPTION

[0030] Various embodiments and aspects of the present disclosure will be described with reference to the details discussed below, and the accompanying drawings will illustrate various embodiments. The following description and the accompanying drawings are illustrative of the present disclosure and should not be construed as limiting the present disclosure. Many specific details are described to provide a thorough understanding of the various embodiments of the present disclosure. However, in some cases, well-known or traditional details are not described in order to provide a concise discussion of embodiments of the present disclosure.

[0031] References in the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment can be included in at least one embodiment of the present disclosure. The phrase "in one embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment.

[0032] Recently, a transformerless flexible AC transmission system (TL-FACTS) with lower weight and cost has also been developed and implemented as an IIU for line balancing and control. An exemplary TL-FACTS-based IIU 600 is shown in FIG. Figure 6. The TL-FACTS based IIU 600 is powered by power extracted from the HV transmission line 108 via a secondary transformer 501 connected to a sensor and power supply block 502 and provided to a DC power supply 604. Having a DC power supply 604 across the capacitor helps to improve the generation of the injection impedance across the terminals 601A-B and optimize the impedance injection onto the HV transmission line 108. The local master controller 503 is enabled with intelligence to respond to power line disturbances and imbalances sensed by the sensor and power supply module 502 coupled to the power line 108. The master local control 503 also has a local clock therein that is synchronizable with an external clock. The master local control 503 has a high-speed wireless connection or interface 410 that is connected to adjacent IIMs and LINCs 302 (as previously described) via a high-speed link 303. These high-speed communication links are used to provide switching control and synchronization signals to the master local control 503, which in turn provides necessary control instructions to the switching control blocks 603A-D of the FACTS switches 602, wherein each FACTS switch 602 includes a control block (e.g., control block 603A-D) and a FACTS device 605. The FACTS device 605 includes a switching device (e.g., a bipolar junction transistor (BJT), a field effect transistor (FET), a metal oxide semiconductor field effect transistor (MOSFET), or the like). Based on the switching control signal from the master local control 503, each of the switching control blocks 603A-D controls its corresponding FACTS device 605, which in turn controls the impedance injection terminals 601A-B connected in series across the HV transmission line 108. The TL-FACTS-based IIU 600, due to its light weight, allows multiple of them to be connected or coupled to the HV transmission line 108 and operated in series or parallel mode or a combination thereof. A single or multiple interconnected TL-FACTS based IIUs 600 may form a single IIM 300 that is directly connected to the high voltage power line 108 and operates at a pseudo ground at the HV power line voltage. A protection switch 606 (i.e., open / close) is provided that is used to close and short the impedance injection terminals 601A-B during a fault condition on the HV transmission line 108 and thereby bypass the circuitry of the TL-FACTS based IIUs 600 contained in the distributed IIM 300 and protect the FACTS devices and control circuitry from damage and failure.

[0033] As described, the IIM 300 extracts power from the HV transmission lines to generate and inject impedance into the power lines in an intelligent manner to control and balance the power flow on the grid. The self-aware IIM 300 with built-in data processing capabilities and intelligence for local decision making is also equipped with a high-speed communication capability or interface 410 that allows sub-cycle communication between local IIMs 300 and connected LINCs 302 within a local area. The LINCs 302 distributed across the local area are also enabled with high-speed communication capabilities that allow them to communicate with adjacent LINCs 302 at sub-cycle speeds. Therefore, the distributed IIM 300 is able to identify changes and disturbances in power line characteristics at a local level in a coordinated manner and react to them very quickly. In addition, as detailed earlier, these intelligent IIMs 300 provide the ability to localize control of line currents and line balances, with interactive response capabilities where necessary. Where necessary, IIMs 300 in adjacent local areas can act in concert through communicatively coupled LINCs 302 to react to disturbances on HV transmission lines 108 and provide responses to instructions and commands from supervisory utility 206 for local line management. High-speed communication capabilities and hierarchical control capabilities are disclosed in co-pending U.S. patent application no. 15 / 068,397 filed on March 11, 2016, currently issued as U.S. Patent No. 10,097,037, the disclosure of which is incorporated herein by reference in its entirety.

[0034] The IIM 300, with or without a transformer, still injects a square wave onto the power line, but at a reduced amplitude. These individual impedance injections (usually in the form of voltage) tend to be less prone to generating harmonic oscillations on the HV transmission line 108 due to the low amplitude injections. However, when high voltages are to be generated and injected onto the HV transmission line 108, one embodiment of the disclosed method uses multiple IIUs 600 from more than one distributed IIM 300 in one or more local areas that work together to inject impedance onto the power line in order to interactively control based on input from a supervisory utility 206 for power system management and / or for power flow control and line balancing applications. The injected voltages are then additive (or aggregated) and can therefore generate harmonic oscillations in the HV transmission line 108. It would therefore be desirable if the impedance injection from the plurality of distributed IIMs 300 could be made pseudo-sinusoidal in nature and then smoothed into a sinusoidal waveform without the expense of high speed, high voltage switching circuitry of previous substation-based implementations using static synchronous series compensators (SSSCs) 204 connected to the power lines 108 and directly controlled by the utility 206.

[0035] like Figure 7Band 7C As shown in , another embodiment is a plurality of interconnected IIUs 600 forming an IIM 300 assembled on one or more mobile platforms that can be transported and deployed as needed at locations along any grid system's HV transmission line to provide any necessary interactive control capabilities.

[0036] Yet another embodiment is the ability for multiple interconnected IIUs 600 forming an IIM 300 to be assembled as mobile or ground based units at a substation and connected to the high voltage power lines of the grid to provide any necessary interactive control capabilities.

[0037] According to one embodiment, a system for injecting impedance onto a high voltage (HV) transmission line is disclosed. The system includes one or more distributed impedance injection modules (IIMs) 300 coupled to the HV transmission line 108. In some embodiments, as part of each IIM 300 including a secondary winding or other alternative sensing capability, a sensor attached to each power line is configured to detect a disturbance, flow imbalance, or other change in characteristics, such as temperature increase or vibration, of the HV transmission line 108 to which the sensor is attached. Sensed changes such as disturbances, flow imbalances, or other changes in characteristics of the HV transmission line are transmitted to the IIM 300, the LINC 302, and the supervisory utility 206 via an available communication link. The master control module 503 of the IIM 300 is configured to identify available resources on the HV transmission line and generate and provide switching control signals to the identified resources for controlling impedance injection to provide interactive control capabilities to commands and instructions from the system supervisory utility 206, and also respond to any detected disturbances, flow imbalances, or changes in characteristics of the HV transmission line 108. A local clock coupled to the master control module is configured to command the start of impedance injection and the stop of impedance injection by the IIU 600 identified as a resource. Impedance injection is controlled by the master control module 503, where the local clock is synchronizable with other local clocks in one or more distributed IIMs and is also synchronizable with the clock in the LINC coupled to the IIM 300.

[0038] According to one embodiment, a method for synchronously injecting impedance onto a high voltage (HV) transmission line 108 is disclosed. The method is performed by an impedance injection module (IIM) 300 coupled to the HV transmission line 108. A disclosed method includes identifying, by a master controller 503 of the IIM 300, a disturbance, a power flow imbalance, or a change in a characteristic of the HV transmission line. The method may also include receiving commands from a network operator / supervisory utility 206 and providing interactive responses to the commands from the network operator / supervisory utility 206, the network operator / supervisory utility 206 identifying a problem with the grid system or a system control requirement and providing commands and interactive control instructions. The method may also include defining an impedance injection waveform by the intelligent master control module 503 in response to the identified disturbance or imbalance, generating injection information including synchronization timing based on the generated impedance injection waveform, sending the injection information to one or more neighboring IIMs 300 identified as available resources, and initiating impedance injection onto the HV transmission line based on the injection information.

[0039] According to an embodiment, a system for injecting impedance onto a HV transmission line using a plurality of distributed IIMs 300 including a plurality of TL-FACTS-based IIUs 600 is disclosed. As an example: the system includes one or more TL-FACTS-based IIUs 600 connected in series and / or parallel combination as a first IIM 300 having a first coordinated impedance injection capability onto the HV transmission line 108, and, where applicable, includes a second set of TL-FACTS-based IIUs 600 connected in series and / or parallel combination as having a second coordinated impedance injection capability onto the HV transmission line 108. The first set of TL-FACTS-based IIUs 600 and the second set of TL-FACTS-based IIUs 600 form two IIMs 300 that are distributed and connected in series with the HV transmission line 108 and enable high-speed sub-cycle communication. Each IIU 600 of each group is enabled to inject a rectangular impedance, typically in the form of a voltage, onto the HV transmission line based on injection information generated for impedance injection, the injection information including synchronization timing established by the master controller 503 of the IIM 300 that identified the interference. In order to reduce harmonic oscillations on the HV transmission line 108, the master controller 503 is enabled to generate impedance injection information so that the impedance injections from each IIU 600 are timed in such a way that when aggregated, the injected impedance forms a pseudo-sinusoidal waveform. By synchronizing the time delay between the impedance injections from each of the IIUs 600 in a coordinated manner, the first and second impedance injections are enabled to cumulatively form a pseudo-sinusoidal impedance waveform for injection onto the HV transmission line.

[0040] In the event that the available resources in one of the local areas are insufficient and additional resources are needed to respond to the disturbance, the controller 503 of the IIM 300 that enables the identified resources to connect to the adjacent local area via high-speed communication capabilities with the LINC 302 and access the required additional resources from the adjacent local area and through it to the adjacent LINC 302.

[0041] There are four possible ways to achieve time synchronization of the clock associated with the IIM 300 (as previously described).

[0042] 1. Use a master controller with a master clock that provides commands to the master controller of each IIM 300 to start and stop impedance injection from the TL-FACTS-based IIU 600 that make up the IIM 300 at the appropriate times. Typically, in this implementation, the master controller 503 is in the LINC 302, which is enabled with high-speed communication links to the distributed IIM 300 and adjacent LINCs 302. In an implementation based only on LINC 302, the master controller 503 in the LINC 302 is the only unit with a clock, and instructions are transmitted to the distributed IIM 300 through a high-speed communication link. Such a system will fail as long as the communication link fails. Therefore, although lower in cost, this type of implementation is not optimal.

[0043] 2. Use the frequency and phase of the current flowing on the power line to establish relative time, one such method is to establish relative time through zero crossing detection. Each local master control module 503 has zero crossing detection capability internally, and all commands as to when to start injection and when to stop injection relative to zero crossing are provided to the IIM 300. The IIMs rely on zero crossings as a reference for their internal timers. These have the following disadvantages: when used with absolute time, correcting the transmission frequency through impedance injection works better. In addition, interference on the line may cause the timer to miss the zero crossing event. This is a low-cost method, but is not currently a reliable method and is therefore not a preferred implementation.

[0044] In both of the above cases, the local master controllers do not have a clock associated with them. Therefore, they are lower cost solutions that rely on an external clock or zero-crossing waveform to initiate action. Generally, these are not optimal for providing high speed corrective action for problems on HV transmission lines.

[0045] 3. The third option is to use a local master controller with a synchronizable clock that is synchronized with the master clock at the utility 206 or LINC 302. In this case, the master controller in the utility 206 or LINC 302 can provide instructions and commands to the distributed IIM 300, which can be temporarily stored. The TL-FACTS-based IIU 600 included in the IIM 300 then injects impedance onto the HV transmission line according to the received and stored instructions. In this case, intermittent communication failures do not affect the operation of the IIM 300 because the local clock can still operate in a synchronized mode if the link is reestablished in short order. Therefore, this is the currently preferred implementation for implementation on a power grid system.

[0046] Fig. 6A is a circuit block diagram illustrating a local master control module of a TL-FACTS based IIU with an associated local clock according to one embodiment. Fig. 6A In the embodiment of the present invention, the local master control module 503 of an IIM (e.g., IIM 300) is coupled to a local clock 606A, which can be synchronized with a clock associated with a utility that is connected to the LINC 302 and connected to the local clock of the IIM using a communication capability to provide local synchronization between all local IIMs 300. Such a timing system is easy to implement and provides the ability to synchronize all local clocks of the IIMs 300 connected under the LINC 302 by using a high-speed communication link 303 that connects all LINCs 302 across all IIMs 300 through the power grid system 200A. Even if the communication link fails, the instructions downloaded to the local master control module 503 can be executed by the IIM 300 in a time-synchronized manner because the local clocks remain synchronized over a period of time. A major drawback of such a system is that in the event of a prolonged failure of the communication link 305 from the utility to the LINC 302 or a failure of the high speed link 303 from the LINC 302 to the IIM 300, the local clock 606A associated with the local IIM 300 may become unsynchronized.

[0047] 4. The fourth option is to have the local master controller have a clock that is synchronized with a global master clock such as a Global Positioning System (GPS) clock. This is the most accurate option and is Figure 6B as shown in .

[0048] Figure 6B is a circuit diagram illustrating a local master control module of a TL-FACTS based IIM having an associated local clock that can be synchronized with a global clock according to one embodiment. Figure 6BIn the embodiment, the local master control module 503 has a local clock 606B associated therewith, which can be synchronized with a global master clock such as a GPS clock 607 to provide synchronization across the local and global IIMs 300 on the power grid system 200A. Such a system is more complex and more expensive, but ensures that in the event of any communication failure, the local clock 606B continues to operate in a synchronized manner, provides any necessary synchronization inputs to the master control module 503 of the IIM 300, and maintains synchronization of the local and global IIMs 300 on the power grid system 200A.

[0049] The described embodiments are shown by way of example only, and other synchronization methods are possible, such as having a GPS synchronizable clock on the LINC 302 that is used to synchronize the local master clock module associated with the IIM 300 via the high speed communication link 303. In such a case, a failure in the communication between the LINC 302 and the local controller 606A would cause the local IIM 300 connected to a particular LINC 302 to be out of sync, while other IIMs across the electrical grid 200 continue to function correctly.

[0050] Figure 7 is a block diagram illustrating an IIM having a series-parallel connection of an IIM based on TL-FACTS according to one embodiment. Figure 7 In the embodiment of the present invention, four TL-FACTS-based IIUs 600-1 to 600-4 together form (or are included as part of) an impedance injection module 300, which is to be suspended from a power line (e.g., HV transmission line 108). In one embodiment, IIUs 600-1 and 600-2 are connected in parallel, and IIUs 600-3 and 600-4 are also connected in parallel. In one embodiment, two groups or pairs of parallel-connected IIUs 600-1, 600-2 and 600-3, 600-4 are connected in series to form the IIM 300. When a sine wave travels down the high voltage (HV) power line 108, the time delay between the two pairs of IIMs is t1.

[0051] In some embodiments, the IIM 300 may include a single IIU 600 or multiple IIUs 600 (eg, four or more as described above) interconnected in a series-parallel configuration, which may also be used as a base subsystem unit in mobile power flow control applications or installed at a substation. Fig. 7AAnother exemplary and non-limiting implementation of an IIM 300 as a power flow control subsystem 700A is shown, wherein a plurality of IIUs 600 are connected in series-parallel, wherein 'm' = 3 IIUs 600 are connected in a series string, as shown in 702A, wherein 'n' = 3 such strings are connected in parallel, as shown in 703A, to form an IIM 300 as subsystem 700A in an exemplary mobile power flow control application. A bypass protection switch 701A is shown, which is used to protect the interconnected IIUs of subsystem 700A in the event of power surges and power system faults.

[0052] Figure 7B An exemplary implementation of a mobile platform is shown, which in one embodiment has three subsystems 700A on a mobile carrier 704B (e.g., a vehicle such as a trailer or any other wheeled vehicle capable of carrying equipment), wherein the subsystems 700A are on an insulator 702B that insulates the subsystems 700A from the ground, and the subsystems are spaced apart from each other by a distance 'S'. In one embodiment, the mobile carrier 704B can be transported to any remote or substation location to provide grid monitoring and control capabilities as required by the supervisory utility 206, for example, to control and manage the overall power system 200.

[0053] Figure 7C A mobile platform 700B is shown having three connections to a three-phase high voltage power line 108 of a power grid 700C. The three subsystems 700A are connected in series with the HV power line 108 by disconnecting the HV power line 108 and supporting both ends with insulators 701C to maintain tension in the HV power line. In one embodiment, connectors 702C are then used to connect each subsystem 700A (which may be a transformerless subsystem) across the cut ends.

[0054] Figure 8 is an exemplary block diagram illustrating time delays between groups of exemplary IIMs distributed on an HV transmission line. Figure 8 , a group of four IIMs 300, each IIM having four TL-FACTS based IIUs connected in a series-parallel combination (as described above). The four IIMs 300 are represented as 300a, 300b, 300c and 300d distributed on the HV transmission line 108. The power line 108 is typically suspended from the tower 201 and isolated from the tower, but they can also be connected to the power line in other ways, such as mounted on a mobile platform and connected to the power line or in a substation area to provide redundancy and expansion capabilities. The time delay between IIMs 300a and 300b is represented as t2, the time delay between 300b and 300c is represented as t3, and the time delay between 300c and 300d is also represented as t2, as shown in FIG. Figure 8 as shown in .

[0055] Fig. 9 is a diagram illustrating an exemplary smooth sinusoidal waveform formed by multiple rectangular injection waveforms that are timed and synchronized. Fig. 9 , an example of the creation of a pseudo-sinusoidal impedance waveform from 16 injected rectangular waves 902 is shown. The sine wave 901 is formed by smoothing out the cumulative impedance injection. The impedance injection is rectangular in shape. In one embodiment, a single impedance injection unit having a set of 16 TL-FACTS-based IIUs (e.g., IIU600) connected in parallel attached to the HV transmission line can inject an exemplary 16 rectangular waveforms 902 from a single location, where the waveforms as shown are easily synchronized. But this type of installation results in a large and heavy IIM 300, which makes it difficult to be supported directly on the HV transmission line. It also increases the cost of such IIMs because they are dedicated to high-value impedance injection. When the IIM 300 is a lighter weight series-parallel configuration distributed on the HV transmission line 108 as shown above, the synchronization and control for forming the injected waveform 902 becomes more difficult without high-speed mutual communication and local synchronization of clocks between local IIM300s distributed across the HV transmission line, and high-speed mutual communication between adjacent LINCs 302.

[0056] Fig.10 is a diagram illustrating an exemplary time-synchronized injection of a rectangular waveform into an HV transmission line to achieve a pseudo-sinusoidal waveform. Fig.10 In, from Figure 7 The injection waves of the group of TL-FACTS-based IIUs 600-1 to 600-4 form an IIM 300. Four such IIMs 300a-d distributed on the HV transmission line 108 are Figure 8 600-1a, 600-2a, 600-3a, etc.), where x is the designation code of the TL-FACTS-based IIU 600 in the IIM 300 and y is the designation of the IIM 300a, b, c, or d, respectively. In this example, it is assumed that the amplitude of the injection waveform from each TL-FACTS-based IIU 600 is a constant value 1002, but this is not mandatory. Fig.10As shown in , the magnitude of the injected impedance is constant, but this is not mandatory as long as the variation is accounted for in the time delay of generating the pseudo-sinusoidal waveform. In this case, the impedance injection waveform from each of the 16 TL-FACTS based IIUs 600 of the four IIMs 300 distributed on the HV transmission line must be synchronized with the impedance injection from the other 15 TL-FACTS IIUs for the start of injection and the stop of injection to generate the pseudo-sinusoidal waveform. Fig.11 1 and 2. The generation of the impedance injection and the start time 1101 and stop time 1102 requirements for the injection are shown in FIG. Fig.10 The duration of the injection is shown in . In the case of mobile container based applications, such as in mobile system control applications including power flow control or in fixed location system control applications including power flow control, such as substation applications, the time delay is negligible and only the synchronization and timing injection delays have to be considered when generating the necessary waveforms.

[0057] Since IIM 300, a, b, c and d are distributed on the HV transmission line, it is necessary to consider Figure 8 and 9 The delay shown in , to obtain a pseudo-sinusoidal waveform. The delay of the synchronization of the waveforms from the four IIM 300 is Fig.14 , including the start delay. For ease of understanding, the first start is indicated as t0, and all other starts are shown with reference to the t0 time.

[0058] Since the speed of transmission on the HV transmission line 108 is very fast, the 300 meter separation between the IIMs will only cause a delay of about 1 to 2 microseconds. Transmission delays can generally be ignored at present time, and impedance injection can be synchronized to time across multiple IIMs 300a-d. The method as described provides additional precision for the impedance injection scheme for future applications.

[0059] Having built-in intelligence and a synchronizable clock with high-speed communication capability 410 in each of the group of locally interconnected IIMs 300a-d, with a local supervisory LINC 302, enables the group of IIMs to be locally and globally time synchronized. This helps to consistently generate the required delays across the locally connected IIMs 300 to function as a group to generate and inject a pseudo-sinusoidal waveform onto the HV transmission line.

[0060] It should also be noted that the examples described are intended to illustrate the present invention and are not meant to be limiting. For example, many more than four TL-FACTS-based IIUs 600 may be used to form an IIM 300, and multiple IIMs 300 distributed over HV transmission lines 108 communicatively interconnected in a local area connection may be used to generate and inject the desired impedance value and the desired number of synchronized injection waveforms to generate a pseudo-sinusoidal impedance waveform. It should also be noted that a similar waveform may also be generated and injected during the other (negative) half cycle time.

[0061] Other exemplary embodiments may have indicated mobile platform and substation implementations where there is no time delay because all IIUs 600 are co-located.

[0062] In addition to the examples of implementations described above, having an intelligent IIM 300 with time synchronization with sufficient processing power enables the IIM 300 to provide interactive control to the utility for system management, and also enables the IIM 300 to locally identify any disturbances and power flow imbalances on the high voltage power lines, coordinate with other distributed IIMs 300s, and generate appropriate waveforms necessary to overcome such disturbances and power flow imbalances. The intelligent IIM 300s can also identify available resources (e.g., available IIMs) in the local and global power grid 200, for example, when additional resources are needed to take corrective action, and use the communication system to enable integrated waveform generation capabilities using these resources. Fig.12 Such a local self-aware intelligent system control block diagram is shown in FIG. The local master controller 503 in this exemplary system includes an intelligent processing engine 1201 that provides intelligence and independent decision making capabilities to the IIM 300. Sensors attached to the power lines sense and extract the conditions of the HV transmission lines to which they are coupled. In one embodiment, the sensors typically provide the sensed information to the utility, and in another embodiment described herein, the information is sensed locally and provided to a local module, which is a disturbance / flow imbalance identification module 1202 that identifies changes in the characteristics of the HV transmission lines.

[0063] In all cases, whether it is an embodiment in which the utility receives sensed information and provides commands in response to the received information, or an embodiment in which sensing and flow control are handled locally, the utility is able to provide interactive instructions and commands to the local IIM for impedance injection to meet the target grid system control objectives. In this case, the local disturbance / flow imbalance identification module 1202 is not used because the IIM 300 interactively responds to commands and instructions for impedance injection from the supervisory utility 206. In this embodiment, these impedance injection instructions received by the IIM 300 are passed to the local injection definition module 1203 for execution.

[0064] exist Fig.12 In the embodiment shown in and described herein, changes in the identification of the HV power line are communicated to the injection definition module 1203 for corrective execution by the disturbance / flow imbalance identification module 1202 .

[0065] The local injection definition module 1203 defines the response waveform to be injected using instructions received from the supervisory utility 206 in the first embodiment or the identified interference data from 1202 in the second embodiment. The resource check and resource identification module 1204 communicates with the local IIM 300s and LINC 302 at high speed via the communication link 303 through the communication module 1206, collecting information about the availability of resources to achieve the necessary injection impedance waveform. The injection detail decision module 1205 generates detailed injection requirements through each of the identified resources available to the IIM 300. The start of the injection time, the end of the injection time and the amplitude of the injection for each of the identified resources include details. The communication module 1206 transmits this information to the corresponding resource IIM 300 through the high-speed communication link 303 by using the wireless connection established by the wireless communication capability 410. Once the response capability of the corrective action taken on the interference on the HV transmission line is established and communicated, the injection start and monitoring module 1207 starts the injection of the waveform via the high-speed communication link of the communication module 1206 and monitors its progress. The monitoring module 1207 will continue to monitor and repeat the injection until the imbalance is corrected or the root cause of the disturbance is eliminated.

[0066] Fig.13 is an exemplary flow chart of a process for providing HV transmission line control using synchronized injection of impedance according to one embodiment. For example, the process may be performed by intelligent IIMs (e.g., IIMs 300a-d), and distributed IIMs 300 synchronize their clocks across the grid or interactively respond to commands and information from a supervisory utility (as defined by S1302).

[0067] In step S1301 , sensors coupled to the HV power transmission lines sense changes in grid characteristics (eg, temperature increase or vibration) and power flow.

[0068] There are two options for processing the sensed data, as shown at step S1302 .

[0069] In a first embodiment (option 1), the sensed information is transmitted to the supervisory utility 206 at step S1303A. The supervisory utility processes the received data and generates control commands for impedance injection and provides them back to the local master controller in the IIM, as shown at step S1304A.

[0070] In the second embodiment (Option 2), the sensed data is sent to the local master controller 503 of the IIM 300 as at S1303B. The interference identification module 1202 of the local master controller 503 identifies the type of local problems and interference on the grid from the extracted information and generates instructions for impedance injection (S1304B).

[0071] The local master controller 503 having intelligence and processing capability 1201 built into the IIM 300 receives the impedance injection instruction and generates an impedance injection solution in the form of a waveform that can resolve the identified problem or disturbance and reestablish stability of the HV transmission line 108 of the grid 200 ( S1305 ).

[0072] The IIM 300 then utilizes the communication capability 1206 with the high speed link 303 to connect it to the local distributed local IIM 300s, using the resource inspection and identification module 1204 of the local master controller 503 to identify active resources, which may or may not be readily available FACTS devices and controllers to generate the necessary waveforms for the impedance injection solution (S1306).

[0073] If the local area resources available to the IIM 300 are insufficient to generate the waveform for the impedance injection solution, then the neighboring location IIM 300 connected via a LINC (e.g., LINC 302) or even resource availability beyond, a distributed IIM 300 available on the high voltage transmission line is identified for use in generating an impedance injection waveform to resolve the problem or disturbance on the HV transmission line of the grid (S1307).

[0074] For example, the IIM 300A uses built-in intelligence and processing capabilities to further extract the capabilities of each of the identified resources and put together an impedance generation and injection pattern with the time of the start of injection, the amplitude of injection, and the stop time of injection to generate the necessary sequence, which when combined, produces a waveform shape and amplitude to overcome the problem or disturbance on the power grid 200 (S1308).

[0075] An impedance injection pattern for generating a response impedance waveform for injection onto the HV transmission line 108 is provided to the corresponding identified resource via the high-speed communication link 303 ( S1309 ).

[0076] The distributed IIMs 300 identified as available resources, acting interactively together in time synchronization, are able to generate and inject the necessary impedance injection waveform onto the high voltage power line of the grid ( S1310 ).

[0077] The combined injected pseudo-sinusoidal waveform generated by the aggregation of the individual injected impedance waveforms is smoothed by the impedance of the HV transmission line to reduce any unwanted oscillations due to impedance injection while providing the required impedance injection response for system control ( S1311 ).

[0078] Although the disclosed invention is described using specific implementations as examples, it is intended to be illustrative and not restrictive only. Practitioners in the art will be able to understand and modify them based on new innovations and concepts as they are made and become available. The present invention is intended to include these modifications that are consistent with the inventive ideas discussed.

Claims

1. A system for injecting impedance into a high voltage power transmission line, the system comprising: a plurality of sensors distributed on and coupled to the high voltage power transmission line, configured to detect changes in power flow on the high voltage power transmission line and changes in characteristics of the high voltage power transmission line and to communicate the sensed data to the local impedance injection module; One or more distributed impedance injection modules, each of which includes one or more impedance injection units based on a transformerless flexible AC transmission system, which are coupled to the high-voltage power transmission line, and each impedance injection unit based on a transformerless flexible AC transmission system includes: The main control module is configured to receiving sensed data from one or more local sensors and generating instructions for impedance injection in response to detected changes, identifying an impedance injection module available for impedance injection as a resource for impedance injection on a high voltage power transmission line, and generating and providing a switching control signal to the identified resource for controlling impedance injection from the identified resource in response to a detected change in the high voltage power transmission line characteristic and a change in power flow on the high voltage power transmission line; and a local clock coupled to the master control module and configured to command the start of impedance injection and the stop of impedance injection controlled by the master control module, wherein the local clock is synchronizable with other local clocks in the distributed impedance injection modules; and The impedance injection unit of the transformerless flexible AC transmission system injects impedance into the high voltage power transmission line at different start and stop times, so that a pseudo-sinusoidal impedance waveform is generated when the impedance is aggregated.

2. The system of claim 1, wherein a local clock in each impedance injection unit of the transformerless flexible AC transmission system is synchronized with the phase and frequency of the current to establish the relative time of commanding the start and stop of impedance injection.

3. The system of claim 1, wherein a local clock in each impedance injection unit of the transformerless flexible AC transmission system is synchronized with a master clock at one of a local intelligent center or a supervisory utility of the monitoring system.

4. The system of claim 1, wherein a local clock in each impedance injection unit of the transformerless flexible AC transmission system is synchronized with a master global clock to command the start and stop of impedance injection.

5. The system of claim 1, wherein each impedance injection unit of the transformerless flexible AC transmission system further comprises a high-speed communication interface for communicating with another impedance injection module in a local area and a sub-loop of a local smart center, for transmitting switching control signals from a master controller, and for coordinating impedance injection of identified resources, and also for responding to any locally detected disturbance or imbalance on the high voltage power transmission line for controlling line current and line balance in the local area, and enabling each distributed impedance injection module to interactively respond to instructions from a supervisory utility to meet target grid system objectives.

6. The system of claim 1, wherein each transformer-less FACTS based impedance injection unit further comprises a plurality of FACTS switches, the switches collectively forming the transformer-less FACTS based impedance injection unit.

7. A system for injecting an impedance waveform into a high voltage power transmission line, the system comprising: A plurality of sensors distributed on and coupled to a high voltage power transmission line, the sensors being configured to sense and monitor the high voltage power transmission line for changes in power flow and changes in characteristics of the high voltage power transmission line, and to transmit the sensed and monitored data from the sensors to a supervisory utility for analysis and generation of instructions to command one or more distributed impedance injection modules on the high voltage power transmission line to meet a target grid system target, each impedance injection module comprising one or more impedance injection units based on a transformerless flexible alternating current transmission system coupled to the high voltage power transmission line, each impedance injection module comprising: The main control module is configured to receiving a command from a supervisory utility and identifying an impedance injection waveform in response to meet a target grid system objective; identifying an impedance injection module that can be used for impedance injection as a resource on a high voltage power transmission line, and generating and providing a switching control signal to the identified resources for controlling impedance injection from an impedance injection unit of each of the identified resources to generate an identified impedance injection waveform; and a local clock coupled to the master control module and configured to command the start of impedance injection and the stop of impedance injection controlled by the master control module, wherein the local clock is synchronizable with other local clocks in the distributed impedance injection modules; wherein the synchronized injections of impedance waveforms from the identified resources are aggregated to generate an impedance injection waveform in response to meet a target grid system objective; and The aggregated impedance injection waveform is a pseudo-sinusoidal waveform.

8. The system of claim 7, wherein each impedance injection unit of the transformerless flexible AC transmission system further comprises a high-speed communication interface for sub-cycle communication with another impedance injection module and a local smart center within a local area for communicating switching control signals from a master controller and for coordinating impedance injection of identified resources in response to instructions from a supervisory utility to meet target grid system objectives; in, All impedance injection modules within a local area that communicate with one local intelligent center are local impedance injection modules.

9. The system of claim 7, wherein the local clock in each impedance injection module is synchronized with one of a master clock at a utility supervisory location or a master global clock.

10. The system of claim 1, wherein the impedance injection unit based on the transformerless flexible AC transmission system injects impedance into the high-voltage power transmission line at different start and stop times, respectively, so that when injected into the high-voltage power transmission line, the aggregation of rectangular waveforms generated by the impedance injection unit based on the transformerless flexible AC transmission system identified as the impedance injection module of the resource generates a pseudo-sinusoidal impedance waveform.

11. A method for synchronously injecting impedance into a high voltage power transmission line, the method being performed by a plurality of impedance injection modules coupled to the high voltage power transmission line, the method comprising: Identify disturbances or power flow imbalances on high voltage power transmission lines, or receive commands from supervisory utilities for use in meeting target grid system objectives; defining an impedance injection waveform in response to an identified disturbance, power flow imbalance, or a command received from a supervisory utility; generating injection information based on a defined impedance injection waveform, wherein the generated impedance injection waveform is a pseudo-sinusoidal waveform; sending injection information to one or more local impedance injection modules; and Impedance injection onto the high voltage power transmission line is initiated based on the injection information.

12. The method of claim 11, further comprising: determining whether local resources from one or more local impedance injection modules are available to generate an impedance injection waveform; as well as In response to determining that local resources are available, an impedance injection waveform is generated using the local resources.

13. The method of claim 12, further comprising: In response to determining that local resources from the one or more local impedance injection modules are unavailable, identifying one or more impedance injection modules in a neighboring location having available resources to generate an impedance injection waveform; as well as An impedance injection waveform is generated using available resources of one or more impedance injection modules in adjacent locations.

14. The method of claim 11, wherein: The injection information includes the injection start time, the injection stop time and the amplitude of the impedance injection waveform.

15. The method of claim 14, wherein the start time and the stop time are synchronized with a phase and a frequency of a current in the high voltage power transmission line as a relative time.

16. The method of claim 14, wherein: The start and stop times are synchronized with a master clock at the supervisory utility.

17. The method of claim 14, wherein: The start time and stop time are synchronized with the master global clock.

18. The method of claim 11, wherein: The injection information is sent to the one or more local impedance injection modules via a local intelligence center that is communicatively coupled to the one or more local impedance injection modules for high speed communication.

19. The method of claim 11, wherein: The local impedance injection module injects impedance into the high voltage power transmission line at different injection start and stop times respectively using the injection information, so that a pseudo sinusoidal impedance waveform can be established.

20. A system for injecting impedance into a high voltage transmission line, comprising: A group of impedance injection units based on a transformerless flexible AC transmission system in a series-parallel configuration, which are used as impedance injection modules distributed on a high-voltage power transmission line; wherein a first impedance injection module having a first set of impedance injection units based on a transformerless flexible alternating current transmission system is coupled to the high voltage power transmission line and provides a first set of impedance injections to the high voltage power transmission line; and a second impedance injection module having a second set of impedance injection units based on a transformerless flexible AC transmission system coupled to the high voltage power transmission line and providing a second set of impedance injections onto the high voltage power transmission line; wherein a first impedance injection module and a second impedance injection module are connected in series on the high voltage power transmission line for providing first and second sets of impedance injections; When the injected impedance is aggregated on the high voltage power transmission line, the time delays between the corresponding impedance injections from the impedance injection units of the transformerless based flexible AC transmission system are all synchronized to form a pseudo-sinusoidal impedance waveform.

21. The system of claim 20, wherein the distributed impedance injection module is assembled on a mobile platform, the mobile platform being transportable and deployable along a high voltage power transmission line included at a substation and connected to the high voltage power transmission line for impedance injection.

22. The system of claim 20, wherein each transformer-based FACTS impedance injection unit from the first and second sets of transformer-based FACTS impedance injection units comprises: a sensor configured to detect a disturbance or imbalance on a high voltage power transmission line; a master control module configured to provide switching control signals for controlling impedance injection for controlling line current and line balance and grid control objectives in response to command inputs from a supervisory utility or detected disturbances or imbalances on the high voltage power transmission line; A local clock coupled to the main control module and configured to command the start of impedance injection and the stop of impedance injection controlled by the main control module, wherein the local clock is synchronizable with other local clocks in first and second sets of impedance injection units of the transformerless flexible AC transfer system to coordinate impedance injection onto the high voltage power transmission line based on the switching control signal.

23. The system of claim 22, wherein each impedance injection unit of the transformerless flexible AC transmission system further comprises a high-speed communication interface for performing sub-cycle communication with other impedance injection units of the transformerless flexible AC transmission system in a local area in response to a detected disturbance or imbalance on the high-voltage power transmission line, so as to control line current and line balance in the local area.

24. The system of claim 22, wherein the local clock of each impedance injection unit of the transformerless flexible AC transmission system is synchronized with (i) a detection signal based on line current and frequency as a relative time, (ii) a master clock at a supervisory utility of the monitoring system, or (iii) a master global clock.

25. The system of claim 22, wherein: The first and second groups of impedance injection units based on a transformerless flexible AC transmission system inject impedance into the high voltage power transmission line at different start and stop times, respectively, so that the rectangular waveforms generated from the first and second groups of impedance injection units based on a transformerless flexible AC transmission system generate a pseudo-sinusoidal impedance waveform when aggregated.

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