WO2016179411A1 - Dispositif de commande de mode avertissement et procédé associé pour des dispositifs de puissance réactive - Google Patents

Dispositif de commande de mode avertissement et procédé associé pour des dispositifs de puissance réactive Download PDF

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Publication number
WO2016179411A1
WO2016179411A1 PCT/US2016/031020 US2016031020W WO2016179411A1 WO 2016179411 A1 WO2016179411 A1 WO 2016179411A1 US 2016031020 W US2016031020 W US 2016031020W WO 2016179411 A1 WO2016179411 A1 WO 2016179411A1
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WO
WIPO (PCT)
Prior art keywords
reactive power
distribution network
measurement
power distribution
power device
Prior art date
Application number
PCT/US2016/031020
Other languages
English (en)
Inventor
Dincer Bozkaya
Anthony KAM
James Simonelli
Jing Huang
Original Assignee
Gridco, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Gridco, Inc. filed Critical Gridco, Inc.
Publication of WO2016179411A1 publication Critical patent/WO2016179411A1/fr

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Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/70—Regulating power factor; Regulating reactive current or power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H02J3/1821—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators
    • H02J3/1835—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control
    • H02J3/1864—Arrangements for adjusting, eliminating or compensating reactive power in networks using shunt compensators with stepless control wherein the stepless control of reactive power is obtained by at least one reactive element connected in series with a semiconductor switch
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation

Definitions

  • Reactive power also known as VAR(s), which stands for Volt-Ampere(s) Reactive
  • VAR Volt-Ampere
  • control has been widely deployed in electrical transmission and distribution networks for various purposes, including enhancing power quality and voltage profile, reducing loss, and the like.
  • VAR devices which are capable of producing or consuming reactive power, also known as VAR devices or reactive power devices, are often deployed for such purposes.
  • VAR devices include, inter alia, capacitors, inductors, reactors, Static VAR Compensators (SVCs), Static Synchronous Compensators (STATCOMs), inverters, and similar type devices.
  • SVCs Static VAR Compensators
  • STATCOMs Static Synchronous Compensators
  • inverters and similar type devices.
  • the last example also includes as a special case of inverters associated with (distributed) energy sources, such as solar panels, wind turbines or energy storage.
  • VAR devices have been deployed at or near both power distribution substations and at various portions of power distribution networks for decades.
  • a VAR device can be controlled in a variety of different ways. Some control schemes are not be based on feedback, e.g., the VAR device is turned on and off (or its VAR output adjusted) based on a pre-set timer, temperature, or manual command. Other control schemes may incorporate feedback, e.g., the device is turned on and off (or its VAR output adjusted) based on measured voltage or measured reactive power flow at one or more points in the power distribution network. In these cases, the quantity being measured (e.g., voltage, reactive power flow, etc.) influences the VAR device's operation and may be affected by the operation of other VAR devices deployed within or coupled to the power distribution network.
  • Some control schemes are not be based on feedback, e.g., the VAR device is turned on and off (or its VAR output adjusted) based on a pre-set timer, temperature, or manual command.
  • Other control schemes may incorporate feedback, e.g., the device is turned on and off (or its VAR output adjusted) based on
  • the VAR device in question measures an electrical quantity M of the power distribution network.
  • M can be the voltage measured at a certain point in the network, such as the terminals of the VAR device, or the reactive power flow measured at a certain point in the network, such as in the main conductor close to the VAR device.
  • the control scheme used to vary output should be selected to ensure stability or convergence of the sequences ⁇ mo, «3 ⁇ 4, ⁇ ⁇ ⁇ ⁇ and ⁇ q ⁇ , qi,... ⁇ . Otherwise, both the VAR output Q and the measured value M can oscillate, which is generally undesirable.
  • the device stops adjusting Q (i.e., it keeps its current VAR output Q constant); as a result, M also stays within the guard band, at least until further changes elsewhere in the network.
  • the guard band can be specified by the center-point and tolerance (m*, Am), by its boundaries ( «3 ⁇ 4min, «3 ⁇ 4max), etc.
  • the conventional guard band method is widely deployed, especially for VAR devices whose output changes in discrete, sizeable steps, such as any devices based on capacitors.
  • the size or width of the guard band (2Am, or equivalently, m max - «3 ⁇ 4mi n ) is programmed to be larger than the change in M due to the minimum-sized change in the value of Q (e.g. due to switching on or off a single capacitor or module).
  • the control scheme makes minimum-sized step changes in Q
  • the measured value M should also change in steps smaller than the guard band, so that the system stabilizes in response to a perturbation of , either by M falling within the guard band or by the device reaching a limit on its output Q.
  • the guard band method can be highly effective in both achieving stability and maintaining M close to the desired value m*.
  • the guard band method may work well for a single VAR device in isolation, it is often insufficient to ensure stability when multiple VAR devices are deployed on the same power distribution network.
  • the measured value M j depends on the output Qj and the outputs of other devices Q k (where k ⁇ j).
  • the measured value at a first VAR device depends on the outputs of the other VAR devices on the power distribution network.
  • the influence of the VAR devices on each other can create instability in the power distribution network. This instability can occur if the outputs of multiple VAR devices change simultaneously or almost simultaneously. Even if the output of each VAR device changes by a relatively small amount— e.g., too small to produce a significant change in by itself— together, these small changes may increase or decrease M by more than the guard band size. For instance, the combined influence of simultaneous small output changes from multiple devices can cause the measured value to jump from below the guard band (M ⁇ m* - Am) to above the guard band (M > m* + Am), or vice versa. In the worst case, this may lead to oscillation of the outputs of the VAR devices as the measured value keeps jumping across the guard band. The system may take a long time to converge or may never converge.
  • the outputs of the VAR devices can be coordinated or jointly controlled to avoid inducing an oscillatory response.
  • this kind of communication or coordination is not often feasible or cost effective.
  • the guard bands can be widened, e.g., to accommodate the change in M due to simultaneous or near simultaneous changes in output from multiple VAR devices as opposed to a single VAR device. However, this degrades accuracy because the eventual value is typically further away from the desired value m*.
  • changing the guard band may require a more detailed study of the characteristics of the network and/or a good knowledge of the number and capabilities of the VAR devices, both of which may be impractical, especially if the VAR devices are not owned by the electric utility.
  • each VAR device may have a variable timer that delays the corrective action (change in Qj) to break the synchronicity that causes oscillation.
  • Each VAR device measures the electrical parameter M j , then acts only its timer expires.
  • the timer duration can be (pseudo)randomized, or can depend on the measurement M j (e.g., how far M j is from the guard band).
  • M j e.g., how far M j is from the guard band.
  • the inventors have recognized that there are certain drawbacks associated with conventional approaches to varying VAR in a power distribution network.
  • the inventors have recognized that using VAR devices that act after different delays reduces the speed with which the VAR devices respond to undesired changes in the measured electrical quantity (e.g. voltage, reactive power, etc) of the power distribution network.
  • the delays can be on the order of seconds or tens of seconds, which is long enough to cause an undesired degradation in the performance of the power distribution network.
  • Embodiments of the present technology include reactive power devices and methods of providing and/or varying reactive power that address the drawbacks in conventional approaches.
  • an electrical property e.g., a voltage, a reactive power, etc.
  • a power distsribution network can be measured. It can be determined whether or not the measurement of the electrical property is outside a predefined set of values.
  • a random number can be obtained, and it can be determined whether or not the random number meets a predefined criterion.
  • the reactive power provided to the power distrubtion network can be varied.
  • reactive power provided to a power distribution network with a state machine switchable between a normal state and a caution state can be varied.
  • a first measurement of an electrical property of the power distribution network can be made.
  • the reactive power provided to the power distribution network can be varied based at least in part on the first measurement.
  • the reactive power provided to the power distribution network can be varied by a first amount if the first measurement is outside a first predefined set of values.
  • an instability criterion can be detected.
  • the method can include transitioning from the normal state to the caution state.
  • a reactive power device for providing reactive power to a power distribution network includes a reactive power source, a switch in series with the reactive power source to connect the reactive power source to the power distribution network, and a controller operably coupled to the switch.
  • the controller is configured to perform a measurement of an electrical property of the power distribution network, determine if the measurement of the electrical property is outside a predefined set of values, obtain a random number in response to determining that the measurement of the electrical property is outside the predefined set of values, determine if the random number meets a predefined criterion, and actuate the switch so as to vary the reactive power provided to the power distribution network in response to determining that the random number meets the predefined criterion.
  • a reactive power device for providing reactive power to a power distribution network includes a reactive power source, a switch in series with the reactive power source to connect the reactive power source to the power distribution network, and a controller operably coupled to the switch.
  • the controller is configured to make a first measurement of an electrical property of the power distribution network and to implement a state machine for varying the reactive power provided to the power distribution network based on the first measurement.
  • the state machine is configured to transition from a normal state to a caution state.
  • reactive power provided to a power distribution network with a reactive power device controlled by a state machine is varied.
  • the state machine can be switchable between a normal state and a caution state.
  • reactive power can be provided to the power distribution network with the reactive power device if a voltage of the power distribution network is outside a first predefined range of voltages.
  • the state machine can be transitioned from the normal state to a caution state if the voltage of the power distribution network is outside a second predefined range of voltages.
  • a reactive power device for providing reactive power to a power distribution network includes a housing, at least one removable reactive power module disposed within the housing to provide the reactive power to the power distribution network, an AC disconnect, and an access panel attached to the housing to provide access to the at least one removable reactive power module.
  • the AC disconnect can be in series with the at least one removable reactive power module to disconnect the at least one removable reactive power module from the power distribution network for removal of the at least one removable reactive power module from the housing.
  • Advantages of the present technology include but are not limited to: independent operation of VAR devices (without the need for coordination or joint control); faster corrective action and convergence than timer-based methods; and proper operation even if there is only one VAR device on the power distribution network (or, equivalently, if the VAR devices on the power distribution network cross-influence each other to a negligible extent).
  • An exemplary process for providing or varying reactive power can be implemented with capacitors, SVCs, STATCOMs, inverter, and similar type VAR devices.
  • the inventive processes can be implemented in or by an external controller (e.g., for a capacitor bank) or as part of the control logic of the VAR device (e.g., in an SVC, STATCOM, or inverter).
  • the inventive processes can be implemented as software inside a controller, processor, firmware, hardware, and the like, as discussed in further detail below.
  • FIG. 1 shows a power distribution network with distributed, decentralized reactive power devices that provide voltage and volt-ampere reactance (VAR) compensation to reduce energy consumption, lower peak demand, and increase system efficiency.
  • VAR voltage and volt-ampere reactance
  • FIG. 2 illustrates in perspective view a modular reactive power device, in an open configuration, according to an embodiment.
  • FIG. 3 illustrates in perspective view a VAR module of the modular reactive power device of FIG. 2.
  • FIG. 4 illustrates in perspective view a capacitor of the VAR module of FIG. 3.
  • FIG. 5 is a schematic illustration of the human-machine interface (HMI) of the modular reactive power device of FIG. 2.
  • FIG. 6 is a schematic block diagram of the modular reactive power device of FIG. 2.
  • FIG. 7 is a schematic wiring diagram of a power module of the modular reactive power device of FIG. 2.
  • FIG. 8 is a schematic wiring diagram of a series switch of the module reactive power device of FIG. 2.
  • FIGS. 9A-9C illustrate in sequence a method for replacing a VAR module of the module reactive power device of FIG. 2.
  • FIG. 10 is a schematic wiring diagram of a VAR module having an inductor, according to an embodiment.
  • FIG. 11 illustrates in perspective view the VAR module having the inductor of FIG. 10.
  • FIG. 12 is a schematic block diagram of a modular reactive power device, including an AC disconnect having a switch, according to an embodiment.
  • FIG. 13 is a schematic block diagram of a modular reactive power device, including an AC disconnect having a circuit breaker, according to an embodiment.
  • FIG. 14 is a schematic block diagram of a modular reactive power device, including an AC disconnect having pluggable fuses, according to an embodiment.
  • FIG. 15A illustrates a state transition diagram for reactive power control with a normal state and a caution state.
  • FIG. 15B is a flow chart of operation in the normal state of FIG. 15 A.
  • FIG. 15C is a flow chart of operation in the caution state of FIG. 15 A.
  • FIG. 15D is a flow chart of an alternative operation in the caution state of FIG. 15 A.
  • FIG. 16 shows a state transition diagram for reactive power control with a normal state and a caution state.
  • FIG. 17 shows a state transition diagram for reactive power control with a normal state and two caution states.
  • FIG. 18 shows a state transition diagram for reactive power control with three normal states and a caution state.
  • FIG. 1 shows a power distribution network 180 with distributed, decentralized reactive power devices 100 (also referred to herein as VAR devices or power devices" or “SVCs”) that provide voltage and volt-ampere reactive (VAR) compensation to reduce energy consumption, lower peak demand, and increase system efficiency, according to an embodiment.
  • Each reactive power device 100 is configured to be electrically coupled to the power distribution network 180, and communicatively (e.g., wireless communication) coupled to a remote management system 155 via a wireless communication network 156.
  • the reactive power devices 100 can be implemented as static VAR compensators (SVCs) that are controlled and monitored remotely via the remote management system 155.
  • SVCs static VAR compensators
  • the remote management system 155 is itself accessed remotely by a management console 157 (e.g., a compute device) communicatively coupled to the remote management system 155.
  • a management console 157 e.g., a compute device
  • the SVCs 100 can be monitored and controlled locally in the field.
  • each SVC may be controlled by a locally implemented state machine to provide voltage or reactive power support based on local conditions.
  • the use of SVCs in this manner can be used in combination with overall sub-station and power distribution system equipment actions in an attempt to optimize voltage and VAR.
  • profiles of the complete distribution system also called volfVAR optimization (WO)).
  • WO volfVAR optimization
  • a specialized version of WO, known as conservation voltage reduction (CVR) can also be implemented where the objective is to reduce the power system voltage (but still within acceptable voltage limits) in order to increase total power system energy efficiency and peak power reduction.
  • SVC devices can provide an important role in CVR programs by using their VAR capability to provide autonomous local voltage support in sections of the power distribution system where the voltage would otherwise be below acceptable levels.
  • these SVCs can be small enough and light enough for quick and easy installation by a single lineman as a solution to 'small' low voltage problems. They can have modular components, with removable access panels, making it fast and simple to both configure them at the warehouse and maintain and upgrade them after installation. Hot-swappable VAR modules make it easy to increase the largest and smallest voltage boosts offered by a single SVC— even after installation— without the need for a wide inventory of different SVCs.
  • the SVC's radio and surge suppressors can be upgraded or replaced without having to remove the SVC from the pole. This can extend the SVC's service life to 15 years, 20 years, or more. Status indicators and an alternating current (AC) disconnect provide added safety and speed during maintenance.
  • AC alternating current
  • FIG. 2 illustrates in perspective view a modular reactive power device 100, in an open configuration, for providing reactive power to a power distribution network, according to an embodiment.
  • the modular reactive power device 100 also referred to herein as the "power device” 100
  • the power device 100 includes various removable and/or interchangeable modular components.
  • the power device 100, and at least a portion of the components disposed therein and/or coupled thereto, can be operated on and/or replaced by an operator of the device 100 within the field of operation (also referred to herein as a "field hot-swap" or a "field upgrade”), as opposed to, for example, requiring entire removal and/or replacement of a power device.
  • Providing for such quick, efficient and safe maintenance of the power device 100 in the field can limit labor and installation time and costs, as well as undesirable outage time of the power device 100 and/or a portion of the power distribution network. Moreover, such modularity of components prevents or limits wasteful retiring of otherwise useable components.
  • the power device 100 includes a housing 110 coupled to an access panel 150 configured to be manipulated (e.g., by an operator in the field) between a closed configuration and an open configuration, and vice versa, such that components of the power device 100 can be serviced and/or replaced.
  • the access panel 150 is movably coupled to the housing 110 via two hinge connections.
  • any suitable coupling members can be used to movably couple the access panel to the housing.
  • an access panel can slide relative to the housing to provide access to the components of the power device 100.
  • the access panel 150 includes a panel stop member 154 configured to secure the access panel 150 in its open configuration such that the power device 100 can be serviced without undue interference from and/or undesirable movement of the access panel 150.
  • the access panel 150 houses a removable wireless connection module 152 (also referred to herein as "communication module”).
  • the communication module 152 can be any suitable component, subsystem, and/or device that can communicate with a network.
  • the communication module 152 can be a network interface card and/or the like that can include at least a wireless radio (e.g., a WiFi® radio, a cellular radio, etc.).
  • the communication module 152 is operably coupled to a controller 140 disposed within the housing 110, and is configured to send signals to and/or receive signals from a remote management system (not shown in FIG. 2) within a network.
  • the communication module 152 is removably coupled to the access panel 150 such that the communication module 152 can be replaced and/or upgraded without having to replace additional components, e.g., the access panel 150 and/or the entire power device 100. It should be obvious to those skilled in the art that the communication module can also be removably coupled to other locations within the housing, and is not necessarily coupled to the access panel.
  • the power device 100 includes a removable reactive power module portion 120 (also referred to herein as "power module” or “reactive power source”).
  • the power module portion 120 includes four individually field- replaceable volt-ampere reactive (VAR) modules 126 (also referred to herein as “VAR modules” or “VAR power source”).
  • VAR volt-ampere reactive
  • Each VAR module 126 includes two capacitors, and is configured to provide up to about 5 kVAR.
  • any suitable number of VAR modules and capacitors can be used, and each VAR module can be configured to provide any suitable amount of reactive power.
  • a power module portion can include only one VAR module, while in other embodiments the power module portion can include multiple VAR modules, such as two or three VAR modules.
  • Each VAR module 126 of the power module portion 120 is removably operably and electrically coupled to a power bar 124.
  • the power bar 124 is coupled to the housing 110.
  • the power bar 124 includes four alternating current (AC) outlets, each configured to electrically communicate with a VAR module 126.
  • AC alternating current
  • any suitable number of AC outlets and/or power bars can be used and disposed within a housing to electrically communicate with the VAR modules.
  • the number of AC outlets can correspond to a number of VAR modules within a power module portion, e.g., a power module portion can include three VAR modules and a power bar can include three AC outlets.
  • a power bar can have a single AC outlet configured to electrically communicate with multiple (e.g., two or more) VAR modules.
  • the housing 110 includes a ground connection 112 for safety and electrical property measurement purposes.
  • a power module portion can include a VAR housing to contain, secure, and/or protect one or more VAR modules within the housing (e.g., housing 110) of the power device.
  • the VAR housing can be configured to electrically communicate both with a power bar (e.g., similar to the power bar 124) and with each VAR module contained in the VAR housing.
  • FIGS. 3 and 4 illustrate a detailed perspective view of a VAR module 126 separated from the housing 110, and a detailed perspective view of a capacitor 128 of the VAR module 126, respectively.
  • the VAR module 126 includes two capacitors 128, each collectively housed in and protected by a capacitor insulator 121 and a cap insulator 123. Both the capacitor insulator 121 and the cap insulator 123 are configured to seal and limit or prevent electrical shock to an operator of the VAR module 126.
  • the cap insulator 123 defines protrusions configured to operably mate with corresponding features of the the housing 110 to facilitate mounting of the VAR module 126 to the housing 110.
  • Each capacitor 121 is operably and electrically coupled to an electrical connector 129 via an electrical coupling 127.
  • the cap insulator defines an opening O configured to allow the electrical coupling 127 to pass therethrough.
  • At least a portion of the electrical connector 129 is non-conductive, (e.g., formed at least in part from a plastic material), and thus touch-safe by an operator.
  • the electrical connector 129 is configured to be removably (e.g., removable by an operator without tools) coupled to the power bar 124.
  • the capacitor 128 (see e.g., FIG. 4) is configured to provide up to 5 kVAR.
  • a reactive power module locking plate 122 (also referred to herein as "locking plate”) is operably coupled to the VAR modules 126, as shown in FIG. 2.
  • the locking plate 122 is configured to secure the VAR modules 126 in a locked positon during operation of the power device 100, and to release the VAR modules 126 such that the one or more VAR modules 126 can be removed from the housing 110 and/or replaced.
  • the locking plate 122 is configured to be manipulated between its locked and released position, and vice versa, without tools (e.g., by a hand of an operator). Without requiring tools, an operator can quickly and safely service or replace one or more of the VAR modules 126.
  • the locking plate 110 includes a spring-release latch; in alternative embodiments, any suitable securement mechanism can be used.
  • the power device 100 includes an AC disconnect 130 configured to operably connect and operably disconnect the VAR modules 126 from the power distribution network 180.
  • the AC disconnect 130 when engaged (as shown in FIG. 2), places the power module 120 in operable and/or in electrical communication with the power distribution network 180.
  • the AC disconnect 130 when engaged, is disposed in series with the power module 120 and the power distribution network 180. In this manner, disengaging the AC disconnect 130 breaks operable and/or electrical communication between the power module 120 and the power distribution network 180.
  • an operator can disengage the AC disconnect 130 to prevent power transmission and/or electrical communication between the power distribution network 180 and power bar 124 and/or the power module 120.
  • the AC disconnect With the AC disconnect in its disengaged position, the capacitors within the power module 120 are allowed to de-energize or drain, thereby allowing an operator to safely service the power module 120.
  • the AC disconnect 130 can be disengaged, and an operator can safely service and/or replace the one or more VAR modules 126 in the field and without physically removing the power device 100 (e.g., from a pole or other structure to which the power device 100 is mounted), after waiting a short time (e.g., 3-6 minutes) for the VAR modules 126 to de-energize.
  • a short time e.g., 3-6 minutes
  • the power device 100 includes a single AC disconnect and four VAR modules 126, however, in alternative embodiments, a power device can include any suitable number of AC disconnects and any suitable number of VAR modules.
  • a power device having two VAR modules can include two AC disconnects each in serial electrical communication with either VAR module.
  • a single AC disconnect can be configured to, when disengaged, break electrical communication between multiple (e.g., two) VAR modules. In this manner, a single AC disconnect can be disengaged to de-energize multiple VAR modules.
  • the AC disconnect 130 includes a plug (e.g., including conductive pin(s) and corresponding receptacle(s) to establish an electrical connection) configured to be disengaged by a user by pulling a portion of the plug.
  • a plug e.g., including conductive pin(s) and corresponding receptacle(s) to establish an electrical connection
  • an AC disconnect can include any suitable disengagable mating component(s) (e.g., a switch, a circuit breaker, removable and/or pluggable fuses, etc.) configured to disengage the power module 120 from the power bar 124 to allow the power module 120 to de-energize.
  • the power device 100 includes two AC input terminals 160 (e.g., two cable glands) configured to communicate power between the power device 100 and the power distribution network 180, when coupled to, for example, input wires (not shown).
  • a power device 100 can include a terminal cover or protector to protect and/or support connections to the AC input terminals.
  • the power device 100 includes a field-removable surge arrestor 170 in operable and/or electrical communication with the AC terminal 160, and in turn, the power distribution network 180.
  • the surge arrestor 170 can prevent the voltage surge from reaching or otherwise affecting any circuitry operably downstream the surge arrestor 170, e.g., the power module 120.
  • the power device 100 can include an indicator (e.g., a light emitting diode) configured to indicator (e.g., illuminate) when the surge arrestor needs to be serviced and/or replaced.
  • the indication e.g., the illumination
  • the power device 100 further includes fuses (not shown) and fuse access holes 1 15 configured to receive and be removably coupled to the fuses.
  • the fuses when coupled to the fuse access holes 1 15, provide access (e.g., via a voltage meter) to determine voltage throughout the power device 100. For example, an operator can use the fuses to confirm that the power device 100 is safe to service (e.g., zero voltage).
  • the power device 100 further includes a power switch (not shown in FIG. 2) that is disposed in series with and operably between the power module 120 and the power distribution network 180, and configured to operably connect and/or operably disconnect the power module 120 and the power distribution network 180.
  • the controller 140 is in operable communication with the communication module 152, and in turn, a remote management system (not shown in FIG. 2) such that the controller 140 can be reconfigured or otherwise manipulated from the remote management system.
  • the controller 140 of the power device 100 is operably coupled to the power switch, and is configured to actuate the power switch to vary reactive power provided to the power distribution network 180 by the power device 100. As described in further detail herein, the controller 140 can actuate the power switch in response to any suitable criteria.
  • the controller 140 performs a measurement of one or more electrical properties (e.g., a voltage, a current, etc.) of the power distribution network 180.
  • the controller 140 further determines if the measurement meets or exceeds one or more predefined values.
  • the controller 140 determines that the measurement of the one or more electrical properties exceeds a predefined set of values, the controller 140, in response to such determination, can obtain a random number, and then determine whether or not the random number meets one or more predefined criteria. If, for example, the controller 140 determines that the random number meets the one or more predefined criteria, the controller 140 can be configured to actuate the power switch to vary the reactive power provided by the power device 100 to the power distribution network 180.
  • the controller 140 can be configured to implement a state machine for determining when to operate the power switch (e.g., based on the voltage measurement of the AC power).
  • the power device 100 further includes a safety sensor 145 operably coupled to the controller 140 and configured to sense a position (e.g., open, closed), of the access panel 150.
  • a safety sensor 145 operably coupled to the controller 140
  • the controller 140 can determine the position of the access panel 150 based on a signal generated by the safety sensor 145, and the controller 140 can be configured to respond in any suitable manner. For example, in some instances, in response to an indication by the safety sensor 145 that the access panel 150 is in an open position, the controller 140 can be configured to actuate the power switch.
  • the controller 140 in response to the access panel 150 being transitioned from its closed configuration to its open configuration, can be configured to actuate the switch to operably decouple the power device 100 from the power distribution network 180, thereby operably decoupling the power module 120 from the power distribution network 180.
  • the controller 140 can be configured to enable the power module 120 (e.g., enable the power module 120 to convey power to the power distribution network 180).
  • the controller 140 can be configured to, in response to an indication by the safety sensor 145 that the access panel 150 is in an open position, put the power device 100 into a suspend state in which the power module 120 will remain in its current state (i.e., the state just prior to the access panel 150 being opened) such that the number of VAR modules 126 electrically coupled to the power distribution network 180 will not change.
  • the controller 140 can be configured to transition the power device 100 to an inactive mode in response to an indication that the access panel 150 is in its open configuration.
  • the safety sensor 145 can be operably coupled to all visual indicators of the power device 100, and in response to the safety sensor 145 being depressed, the controller 140 can be configured to cause all of the indicators to illuminate for a time period (e.g., 8-10 seconds) to allow an operator to perform a visual verification that each indicator is properly functioning. Upon expiration of the time period (which can be any time period suitable for an operator to visually verify), the indicators can return to normal or default configuration.
  • the controller 140 is operably coupled to the human- machine interface (HMI) 190.
  • the HMI 190 is configured to provide or otherwise indicate a status of the power device 100 and/or any of the components of the power device 100.
  • the HMI 190 is configured to indicate one or more of the following: a status of the power device 100, a status of the power module 120, a status of one or more VAR modules 126 (or one or more capacitors therein), a state of the power device 100 (e.g., whether the power device 100 is in a suspend state, an auto state, an active state, an inactive state, an alarm state, etc.), and/or a communication status of the power device (e.g., a communication status of the connection module 152).
  • the HMI 190 is visible from outside the housing 110 when the access panel 150 is in its open configuration.
  • the HMI indicators are operational only when the access panel 150 is open.
  • the HMI 190, or a portion thereof is visible from outside both the housing 110 and the access panel 150 when the access panel is in its closed configuration.
  • an access panel defines or includes a transparent portion and/or a window to allow visible access to the HMI from outside the housing 110 and the access panel 150.
  • FIG. 5 is a schematic illustration of the HMI 190.
  • the HMI 190 is implemented on a flexible-printed-circuit that includes physical switches, light emitting diodes (LEDs), and associated labels.
  • the HMI 190 is configured to enable and/or disable the power device 100, e.g., in response to an instruction (e.g., depression of a button of the HMI 190) from an operator.
  • an instruction e.g., depression of a button of the HMI 190
  • the HMI 190 includes a reset button, an auto/manual button, a communication (comms) reset button, an auto indicator, an active indicator, an alarm indicator, a comms indicator, and four VAR module indicators.
  • the indicators include light emitting diodes (LEDs) configured to illuminate in response to particular or predefined events to provide a visual indication, e.g., to an operator in the field.
  • the indicators can include any suitable mechanism to provide an indication or signal, e.g., an audible signal.
  • the reset button when depressed, causes a reboot of the power device 100.
  • the reset button can be configured such hat depression of the reset button (e.g., by an operator) for a period of time (e.g., 5 seconds) causes the power device 100 to reboot.
  • the auto/manual button when depressed, enables an operator to toggle the power device
  • the controller 140 can be configured to toggle the power device 100 in response to depression of the auto-manual button only if the auto- manual button is depressed twice within a period of time (e.g., 5 seconds).
  • the comms reset button when depressed, enables an operator to toggle only the power for the connection module 152, resulting in a reset of communication functions of the connection module 152.
  • the auto indicator is configured to not illuminate when the power device 100 is in its manual (or inactive) state, illuminate in a constant manner when the power device 100 is in its auto (or active) state, and alternate between illumination and no illumination (e.g., blink) when the auto-manual button has been depressed once, but not twice, within the time period.
  • the active indicator is configured to illuminate when the power device 100 is in its normal state in which the power device 100 is actively regulating voltage associated with the power distribution network 180.
  • the active indicator is configured to not illuminate when the power device 100 is in its manual (or inactive) state. Further, the active indicator is configured to blink when the power device 100 is transitioning between its inactive and active states.
  • the alarm indicator is configured to illuminate when the power device 100 has detected a hardware failure, indicating that the power device 100 needs to be repaired.
  • the alarm indicator is configured to not illuminate when no active alarms exist and the power device 100 hardware is functioning as intended. Further, the alarm indicator is configured to blink when the power device 100 is experiencing one or more active alarms.
  • the comms indicator is configured to illuminate when the removable wireless connection module 152 is in communication with a remote device (i.e., a device remote from the power device 100.
  • the comms indicator is configured to blink when the power device 100 is downloading software. Further, the comms indicator is configured to not illuminate when no communication exists between the connection module 152 and a remote device.
  • the VAR module indicators include four separate indicators (e.g., 4 separate LEDs), i.e., one for each VAR module 126.
  • Each VAR module indicator is configured to illuminate when the VAR module 126 to which it is operably coupled is working properly and is active.
  • Each VAR module indicator is configured to not illuminate when the VAR module 126 to which it is operably coupled is inactive. Further, each VAR module indicator is configured to blink when the VAR module 126 to which it is operably coupled or assigned is disabled (e.g., due to a detected fault), or not installed.
  • the HMI 190 further includes a fault status indicator 142 that is visible from outside the power device 100 such that an operator can view the fault status indicator 142 without opening the access panel 150 and/or otherwise manipulating the power device 100.
  • the fault status indicator 142 can be configured to illuminate in response to any suitable predefined event. For example, in some instances, the fault status indicator 142 is configured to illuminate when one or more VAR modules 126 needs replacement. Further, in some instances, the fault status indicator 142 is configured to illuminate when any component of the power device 100 has failed, and/or when software stored at and/or processed by the power device 100 is booting and/or has failed to properly boot.
  • FIG. 6 illustrates a schematic block diagram of the power device 100, showing how in this embodiment the components of the power device 100 are operably coupled and operably arranged with respect to each other.
  • FIG. 7 illustrates in more detail a schematic wiring diagram of the power module 120. As shown, the VAR modules 126 of the power module 120 are electrically coupled to each other in a parallel arrangement and between the AC terminals 160. Further, each VAR module 126 is electrically coupled with a switch 116 in series between the VAR module 126 and one of the AC terminals 160.
  • FIG. 8 illustrates in more detail a schematic wiring diagram of each series switch 116.
  • each series switch 116 includes an electromechanical relay 135, a module isolation fuse 131, a current in-rush limiter inductor 132, a voltage transient protector 133 (including a resistor operably coupled in series to a capacitor), and two power semi-conductor AC switches 134 (SCRl and SCR 2, also referred to herein as the "SCRs") coupled to each other in a parallel configuration.
  • the SCRs 134 in use, provide pass through current to limit or prevent undesirable bounce and wear (e.g., wear of metal contacts of the relay) of the relay.
  • undesirable bounce and wear e.g., wear of metal contacts of the relay
  • FIGS. 9A- 9C illustrate in sequence a method for replacing a VAR module 126 of the power device 100.
  • FIG. 9A illustrates the power device 100 with the access panel 150 in its open configuration and the locking plate 122 in its locked configuration.
  • an operator can unlock or otherwise manipulate the locking plate 122 to its unlocked or open configuration, as shown in FIG. 9B.
  • the spring-release latch can be manipulated to release the locking plate 122 from its locked position.
  • one or more VAR modules 126 can be accessed by an operator in the field. With such access, the operator can disconnect an electrical connector 129 from a VAR module 126 and then remove (e.g., slide) the VAR module 126 from the the housing 110, as illustrated in FIG. 9C. With the VAR module 126 removed, a replacement VAR module 126 can be installed in the housing 110 by sliding the VAR module 126 into the housing 110 and connecting the electrical connector 129 thereto. With the one or more VAR modules 126 replaced, the operator can then engage or lock the locking plate 122 (e.g., using the spring- release latch) into its locked configuration (e.g., as illustrated in FIG. 9A).
  • the power device 100 includes a reset switch operably coupled to the controller 140 and configured to reset, when actuated, the power module 120 to a particular state, e.g., a default state.
  • the power device 100 can include an activity switch operably coupled to the controller 140 and configured to switch the power module 120 from an active mode to an inactive mode, and vice versa.
  • the power device 100 can include a communication reset switch operably coupled to the controller 120 and configured to reset the removable wireless connection module 152 between states, e.g., reset the connection module 152 to a default state.
  • the one or more switches described herein can be manually operated, automatically operated, or any suitable combination thereof.
  • VAR modules 126 have been illustrated and described herein as including capacitors, in alternative embodiments, one or more VAR modules of a power module can include any suitable device configured to store electrical energy.
  • a VAR module 226 of a power device 200 can include an inductor configured to provide reactive power similarly to as described with respect to the capacitors of the VAR module 126.
  • the VAR module 226 is electrically coupled to a series switch 216.
  • the power device 200 can be constructed the same as or similar to, and function the same as or similar to the power device 100 described above. Thus, some details regarding the power device 200 are not described herein.
  • FIG. 11 illustrates the VAR module 226 separated from the power device (not shown).
  • the VAR module 226 includes an inductor 228 housed in and protected by an inductor insulator 221.
  • the inductor insulator 221 is configured to seal and limit or prevent electrical shock to an operator of the VAR module 226.
  • the inductor 228 is operably and electrically coupled to an electrical connector 229 via an electrical coupling 227.
  • the electrical connector 229 includes a non-conductive portion (e.g., formed at least in part from a plastic material), and thus is touch-safe by an operator.
  • the electrical connector 229 is configured to be removably (e.g., removable by an operator without tools) coupled to the power bar (not shown in FIG. 11).
  • the VAR module 226 and its associated components can be configured to function similar to the VAR module 126.
  • a VAR module can include both a capacitor and an insulator.
  • the insulator can be disposed over at least a part of the capacitor to limit or prevent undesirable charge accumulating on the capacitor, for example, from electrical contact with the housing.
  • the VAR module can include a similar electrical connector in electrical communication with the capacitor to connect the capacitor to associated circuitry of the reactive power device.
  • an AC disconnect switch includes a plug (e.g., AC disconnect 130).
  • a power device 300 includes an AC disconnect 330 having a switch.
  • the AC disconnect 330 can be configured to operably connect and/or operably disconnect the removable reactive power module portion 320 (also referred to herein as "power module") from the power distribution network 380.
  • the AC disconnect 330 can be actuated by an operator in the field and/or by an operator remote from the power device 300, e.g., by use of the power management system in communication with the connection module and controller.
  • the AC disconnect 330 when in its closed configuration, places the power module 320 in operable and/or in electrical communication with the power distribution network 380. Conversely, the AC disconnect 330, when in its open configuration (as shown in FIG. 12), breaks operable and/or electrical communication between the power module 320 and the power distribution network 380.
  • the power device 300 can be constructed the same as or similar to, and function the same as or similar to the power device 100 described above. Thus, some details regarding the power device 300 are not described herein. It should be understood that for features and functions not specifically discussed, those features and functions can be the same as or similar to the power device 100.
  • a power device 400 includes an AC disconnect 430 having a circuit breaker.
  • the AC disconnect 430 can be configured to operably connect and/or operably disconnect the removable reactive power module portion 420 (also referred to herein as "power module”) from the power distribution network 480.
  • the AC disconnect 430 can be actuated by an operator in the field and/or by an operator remote from the power device 400, e.g., by use of the power management system in communication with the connection module and controller.
  • the AC disconnect 430 when in its closed configuration, places the power module 420 in operable and/or in electrical communication with the power distribution network 480.
  • the AC disconnect 430 when in its open configuration (as shown in FIG. 13), breaks operable and/or electrical communication between the power module 420 and the power distribution network 480.
  • the power device 400 can be constructed the same as or similar to, and function the same as or similar to the power device 100 described above. Thus, some details regarding the power device 400 are not described herein. It should be understood that for features and functions not specifically discussed, those features and functions can be the same as or similar to the power device 100.
  • a power device 500 includes an AC disconnect 430 having pluggable fuses.
  • the AC disconnect 530 can be configured to operably connect and/or operably disconnect the removable reactive power module portion 520 (also referred to herein as "power module") from the power distribution network 580.
  • the pluggable fuses installed (as shown in FIG. 14) and properly functioning, the power module 520 is in operable and/or in electrical communication with the power distribution network 580.
  • the pluggable fuses blown and/or removed by an operator (e.g., in the field), operable and/or electrical communication between the power module 520 and the power distribution network 580 is interrupted and/or broken.
  • the power device 500 can be constructed the same as or similar to, and function the same as or similar to the power device 100 described above. Thus, some details regarding the power device 500 are not described herein. It should be understood that for features and functions not specifically discussed, those features and functions can be the same as or similar to the power device 100.
  • an inventive reactive power device may include or be operably coupled to a controller or processor with hardware, software, and/or firmware that implements a state machine for varying reactive power.
  • the state machine keeps track of whether the reactive power device is in "normal” state (also referred to herein as “normal” mode) or "caution” state (also referred to herein as “caution” mode).
  • caution or normal
  • caution also referred to herein as “caution” mode
  • the state machine transitions between the normal and caution states depending on measurements of voltage, reactive power, current, and/or other electrical properties of the power distribution network.
  • the reactive power device's status or output may also trigger or inhibit transitions among states.
  • the act of measuring may be controlled by a different software or firmware or hardware process, which is distinct from the state machine (software or firmware or hardware) process.
  • Some underlying mechanism e.g., a scheduler in an operating system
  • the terms “measure,” “take a measurement,” “perform a measurement,” and the like may refer to reading a register or memory location where a measured value is stored, the measured value having been previously written to that location by the measurement process.
  • the terms “first measurement,” “second measurement,” and the like do not necessarily imply one measurement being taken at a point in time before or after the other.
  • a “first measurement” may be a voltage at time Tl
  • a “second measurement” may be a voltage at time T2 (measured at the same location or different locations), and Tl may be before, after, or simultaneous with T2.
  • FIG. 15A shows a state transition diagram between a normal state 1510 and a caution state 1520.
  • the reactive power device In the normal state 1510, the reactive power device "acts normally". In one embodiment, it measures one or more electrical properties of the power distribution network and, if those electrical properties are outside a specified set of values, varies reactive power provided to the power distribution network, without first waiting through an explicit timed delay after the measurement. This enables the reactive power device to respond quickly to correct undesirable network conditions (e.g., low or high voltages). If the reactive power device senses potential instability or oscillations in the network, it enters the caution state 1520. (Otherwise it stays in normal state.)
  • the reactive power In the caution state 1520, the reactive power "acts cautiously".
  • the device probabilistically varies reactive power provided to the power distribution network as described in greater detail below. By varying reactive power probabilistically instead of deterministically, the reactive power device is less likely to cause or perpetuate network instabilities.
  • the state machine remains in the caution state 1520 until it senses a clearing criterion, at which point it transitions to the normal state 1510.
  • FIG. 15B is a flowchart that illustrates one embodiment of how the reactive power device operates while in the normal state 1510 of FIG. 15 A.
  • the controller of the reactive power device measures an electrical property (1511), such as the voltage or reactive power at a particular point in the power distribution network, and compares M to a programmed set of values (1512), e.g., a guard band. If M is outside the set of values, the reactive power device adjusts its VAR output Q (1513) in an attempt to bring M back to a value within the set of values.
  • Other example VAR devices may adjust their VAR outputs using proportional-integral (PI) control.
  • PI proportional-integral
  • the controller of the VAR device While in the normal state 1510, the controller of the VAR device also checks for potential instability (1515) in the voltage or reactive power of the power distribution network or in the reactive power that it is providing to the power distribution network. If the controller detects an instability, the VAR device transitions into caution state (1516). Otherwise, the VAR device remains in normal state (1514). Likewise, ifM is within the set of values, the controller remains in the normal state (1514) without adjusting the VAR output of the reactive power device.
  • the VAR device's behavior in the caution state 1520 is an engineering design choice.
  • the VAR device may take actions which are "cautious" in the sense that the actions are less likely to cause (or perpetuate) unstable conditions in the network.
  • Such "cautious" actions may include making small, probabilistic adjustments to Q and attempting to break any synchronization between multiple VAR devices.
  • the criterion for potential instability (used in 1515), also called the normal-to- caution state transition criterion, may include or be based on observations that directly prove or strongly suggest that instability is already happening or might be imminent.
  • the exact definition of what constitutes potential instability is an engineering design choice.
  • the following exemplary rules may be used:
  • Last-Action Rule The VAR device stores a record or indication of the last adjustment made to Q in a memory. If the last adjustment was supposed to increase (decrease) M, and has increased (decreased) by an excessive amount, then the VAR device transitions into the caution state 1520. This may be based on the principle that an excessive increase or decrease strongly suggests that other VAR devices exist and are acting (almost) synchronously, which if allowed to continue may lead to undesired (e.g., oscillatory) behavior. [0099] The exact threshold for an excessive amount can be defined variously. For example, if the controller is programmed with a guard band, then any value of M above or below the guard band can be considered excessive.
  • the controller may use a second predefined set of values, extending above and/or below the guard band (e.g., by 10%, 25%, or 50%), to detect instability.
  • the VAR device can also be programmed with a rule to calculate, or can use historical data to estimate, the expected change in M due to the last adjustment to Q.
  • An excessive amount can be defined as any actual change in M greater than a certain multiple (e.g., 1.5x or 2x) of the expected change.
  • the threshold for an excessive amount can also be defined, at least in part, with reference to other internal variables, including user-defined thresholds on , changes in , Q, and changes in Q.
  • the VAR device stores a record or indication of the voltage or reactive power ( ) values that it has measured (or some summary thereof) in a memory. If, during the most recent instability detection period, the VAR device has measured at least one M value which is deemed “too low” and it has also at another time measured another M value which is deemed “too high,” then the VAR device transitions into the caution state 1520. If the controller has observed values of M that are "too low” and "too high,” this suggests that may be oscillating.
  • the length of the instability detection period is a matter of engineering choice.
  • Some specific examples may include a fixed duration, or the duration since the last measurement of M within a certain set of values, such as the guard band.
  • the threshold for "too low” and “too high” are also matters of engineering choice, and may be derived from thresholds programmed or estimated based on network characteristics.
  • One example may be any value below (above) the guard band is considered “too low” ("too high”).
  • the guard band can be used to adjust Q (similar to conventional methods) while a different range derived (at least in part) from the guard band, e.g., by expanding or shrinking the guard band, may be used to define the thresholds for "too low” and "too high” values.
  • the controller may transition from the normal state 1510 to the caution state 1520 based on a pair of successive voltage or reactive power measurements.
  • the controller may determine the first and second measurements are within a single predefined set of values or within respective predefined sets of values. For instance, if the first measurement is within a first (continuous) range (e.g., a voltage greater than 250 V) and the second measurement is within a second continuous range (e.g., a voltage less than 230 V) that does not overlap with the first continuous range, the controller may determine that the state machine should change to the caution state 1520.
  • a first (continuous) range e.g., a voltage greater than 250 V
  • a second continuous range e.g., a voltage less than 230 V
  • FIG. 15C is a flowchart that illustrates one embodiment of how the reactive power device operates while in the caution state 1520 of FIG. 15 A.
  • the controller measures the electrical property (e.g., voltage or reactive power) of the power distribution network (1521) and determines whether or not the electrical property M is outside a predefined set of values (e.g., the guard band or a range wider than the guard band) (1522). If the electrical property Mis outside the predefined set of values, the controller obtains a random value R (1523).
  • the electrical property e.g., voltage or reactive power
  • the random value R can obtain the random value R by generating a pseudorandom number, by sampling the system time of the reactive power device and optionally taking the least significant (least predictable) bits, or by using a measured value, such as the voltage of the reactive power device, and optionally taking the least significant (noisiest) bits.
  • the controller compares the random value R to a criterion C (1525) in order to determine whether or not to vary its VAR output. If the random value is expressed in binary format, for example, the controller may determine if certain bits (e.g., the least significant bits) in the binary expression meet predefined logical or arithmetical criteria.
  • the criterion C is a predefined criterion; e.g., if the random value is
  • the criterion C may be that the number is less than 0.5.
  • the controller varies the reactive power provided to the power distribution network (1526). In some cases, the controller varies the reactive power by an amount smaller than the variation typically applied in the normal state 1510, e.g., a smallest step size in the VAR output by the reactive power device. The controller may also vary the reactive power based on recent variations in reactive power and/or recent measurements of voltage or reactive power.
  • the controller does not vary the reactive power provided to the power distribution network. In either case, the controller may determine whether or not to remain in the caution state 1520 or transition (1527) to the normal state 1510.
  • the probabilistic reactive power variation provided by the reactive power device in the caution state 1520 can be characterized as "(virtual) coin flipping": the controller of the VAR device (pseudo)randomly decides whether to act or not, with probability of action P. This is called “coin flipping” because it is equivalent to (virtually) flipping a (potentially biased) coin with probability P of showing "heads.” If the controller of the VAR device decides not to act based on the outcome of the coin flip, then it does not adjust Q, at least until the next
  • VAR device decides to act based on the coin flip, then it adjusts Q based on . If multiple VAR devices are flipping coins independently and simultaneously, then typically only a fraction of the VAR devices should vary their VAR outputs at a given time. This reduces the likelihood that all of the VAR devices will act simultaneously to create undesired oscillations in reactive power or voltage across the voltage distribution network.
  • the value of the coin-flip probability of action P can be a programmed by the controller to be constant (e.g. 25% or 50%), or it can be a function of (e.g., how far is from a programmed guard band), and/or other internal variables, e.g., time the VAR device has spent in caution state 1520, previous adjustments to Q that have been made while in caution state 1520, previous measured values of , and the like.
  • P may depend on what the most recent adjustment to Q was and what effect it had on M (and whether the effect was "excessive" similar to the "Last- Action Rule" for detecting potential instability disclosed above).
  • the controller may use one function to adjust Q based (at least in part) on M when in the normal state 1510 and a different function to adjust Q based (at least in part) on M when in the caution state 1520, as illustrated in FIG. 15D.
  • some kind of proportional (or PI) control may be used (e.g., to make big adjustments to Q if is far from some ideal or nominal value); while in the caution state 1520, a different proportional (or PI) control (e.g., with different coefficients or numerical settings) or a constant response (e.g., the smallest possible step change in Q) may be used (1531) to reduce the chances of creating an undesired response inM.
  • a different proportional (or PI) control e.g., with different coefficients or numerical settings
  • a constant response e.g., the smallest possible step change in Q
  • the function used to adjust Q based on M in the caution state 1520 is different from the function used in normal state, e.g., if the function used in caution state makes smaller changes for a given voltage variation or measurement, then it may reduce or eliminate any instability or oscillation.
  • a reactive power device e.g., a STATCOM or inverter
  • Q may be capable of adjusting Q in a (practically) continuous range.
  • one way to act cautiously is to adjust Q based not only on M, but also decrease the successive step change sizes in Q, e.g., exponentially based on the time spent in the caution state 1520, the number of adjustments, or measurements already made.
  • the likelihood of causing or perpetuating instabilities can be lowered because big step changes inM (due to cross-influence of multiple devices) are less likely.
  • the VAR device stays in the caution state 1520 until the controller detects one or more clearing criteria, at which point it transitions (1527) to a normal state 1510.
  • the clearing criterion should indicate or suggest that the power distribution network is stable and is likely to remain stable.
  • clearing criteria include, but are not limited to: [00115] Measurement-in-Range Rule: The clearing criterion can include K consecutive measurements of M within a predefined set of values (e.g., the guard band or a range related to the guard band), where K ⁇ 1. It can also include K (not necessarily consecutive) measurements of M within the set of values out of the last L measurements, where L > K ⁇ 1 , or K
  • Transforming-a-Potential-Instability Rule A rule that can be used to detect or determine the presence of an instability or potential instability may be used or adapted for sensing a clearing criterion. If the rule would not have declared potential instability for a given voltage or reactive power measurement or set of voltage or reactive power measurements, then the clearing criterion is deemed to be satisfied for the same voltage or reactive power measurement or set of voltage or reactive power measurements. Likewise, if the rule would have declared a potential instability for a given measurement, then the clearing criterion is deemed to be unsatisfied for the same measurement. Further modifications may be made to the transformed rule, e.g., in terms of measurement threshold, number of measurements, etc.
  • a simple version of the Bimodal-Measurement Rule for detecting potential instabilities can be transformed into the following clearing criterion: if, during the most recent instability detection period, the VAR device has not observed both "too low” and “too high” values of M (e.g., values of M both above and below the guard band), then the clearing criterion is met, and the controller cause the VAR device to re-enter Normal state.
  • M e.g., values of M both above and below the guard band
  • the controller of the VAR device may use different instability criteria and clearing criteria.
  • the VAR device can use a clearing criterion which is based on bimodal measurement, but sense a potential instability using the Last- Action Rule, the Conservative Rule, or the Bimodal-Measurement Rule with a different instability detection period and/or different thresholds for determining that a value is "too low" or "too high.”
  • the instability and clearing criteria may be selected so that it is harder to leave the caution state 1520 than to enter it.
  • the instability and clearing criteria may be selected so that it is easier to leave the caution state 1520 than to enter it.
  • a VAR device can have multiple different caution and/or normal states. These caution and normal states can be equivalently implemented as single caution and normal states with further differentiation based on other internal variables. Whether or not the state machine should be implemented with multiple caution and/or normal states, or with a single caution and/or normal state with further differentiation based on internal variables is an engineering implementation question, and may be answered based on the implementation environment, programming language used, and the like.
  • each of the different caution (or normal) states can be associated with its own (potentially different) state transition rules (for transitioning to other caution or normal states) based on its own (potentially different) definitions of potential instability or clearing criterion.
  • Each of the different caution (or normal) states can also have its own (potentially different) method of "acting cautiously” or “acting normally,” e.g., different timer durations, different coin-flip probabilities, different ways to decide whether and how to adjust the reactive power device's output Q.
  • the caution (or normal) state may be viewed as having state transition rules or actions which depend on those internal variables.
  • a VAR device in caution state can decide, depending on certain internal variables, which clearing criteria to use, whether to adjust its internal variables (e.g., the coin-flip probability P or guard band size), etc.
  • FIG. 18 shows a transition diagram for a state machine that transitions among three different normal "sub"-states and a single caution state. Even though FIG. 18 shows three normal "sub"-states, an actual implementation may be based on a single normal state with further differentiation based on internal variables, e.g., a log of past values, or flags derived thereof.
  • the three "sub"-states in FIG. 18 shows three normal "sub"-states, an actual implementation may be based on a single normal state with further differentiation based on internal variables, e.g., a log of past values, or flags derived thereof.
  • Normal-N is a normal state with no memory of M value(s) which are out of guard band
  • Normal-H is a normal state with memory of value(s) which are above «3 ⁇ 4max, but no memory of value(s) which are below «3 ⁇ 4min
  • Normal-L is a normal state with memory of M value(s) which are below ttimhi, but no memory of M value(s) which are above «3 ⁇ 4max-
  • FIG. 18 It shows examples of the state transitions and examples of the Bimodal-Measurement Rule for detecting potential instabilities. If written in an appropriate programming language, this pseudo-code can be stored on a non-volatile computer-readable medium and accessed by a processor in the controller to control how the reactive power device responds to measurements of voltage or reactive power in the power distribution network.
  • StepStateMachine ( )
  • measuredM MeasureMvalue () ;
  • AdjustQ_Normal (measuredM)
  • AdjustQ_Normal (measuredM)
  • AdjustQ_Normal (measuredM)
  • AdjustQ_Caution (measuredM) ;
  • AdjustQ_Caution (measuredM) ;
  • AdjustQ_Normal (measuredM)
  • P can be a different fixed value, // or P can depend on measuredM or on other internal variables // such as time spent in CAUTION
  • the reactive power device measures a voltage of the power distribution network and compares the measured voltage to four voltage thresholds: V xl0 ⁇ V l0 ⁇ V hi ⁇ V xhi .
  • These thresholds can be fixed, set by the user, or adjusted automatically by the controller based on historical measurements or in response to user commands.
  • These four thresholds partition the possible voltage values into 5 non-overlapping ranges or bands (which form a slight generalization of the traditional guard band). In a normal state, the state machine adheres to the following truth table:
  • FIG. 16 shows a state transition diagram for a state machine with two states for operating a reactive power device: ⁇ Normal, Caution ⁇ .
  • This example state machine implements the Conservative Rule for instability criterion.
  • the reactive power device makes voltage readings that are out of range (e.g., too high or low)
  • the reactive power device switches capacitor(s) in or out as appropriate, then transitions to caution state.
  • caution state the reactive power device "flips a coin” if the voltage is out of range, then switches capacitor(s) in or out based on the coin flip and remains in caution state regardless of the coin flip.
  • the reactive power device switches at most one capacitor at a time when in caution state. If the voltage is in range, e.g., for a single measurement or for three measurement cycles, then the reactive power device stays in or transitions to normal state.
  • Reactive power devices controlled by a two-state state machine also perform better than reactive power devices with randomized delays.
  • VAR reactive power
  • Each of these VAR devices considers any voltage ⁇ 230V to be low and any voltage > 250V to be high.
  • the state-machine VAR devices in normal state respond to high and low voltage measurements much more quickly than variable-timer VAR devices: TABLE 2: Variable Timer Response to High and Low Voltage Measurements
  • VAR 229V Increase VAR Network event causes voltage to drop; in reaction both devices act (without timer) by increasing VAR
  • This state machine implements a version of the Last Action Rule for instability criterion.
  • the reactive power device when in a caution state, it also remembers its last action (e.g., switch in vs. switch out). It acts cautiously only if the next appropriate action is opposite to the last action to prevent possible oscillation. As a result, it may converge more quickly in certain situations than the two-state configuration.
  • switching out the first capacitor involves a coin flip, because the appropriate action (switching out a capacitor in response to high voltage) is opposite to the last action (switching in a capacitor).
  • the three-state configuration may converge more quickly when correcting or compensating with an insufficient response to a low or high voltage measurement.
  • the overall response is just as fast as if there is no caution state.
  • FIG. 18 shows a four-state configuration that provides both fast response speed and fast stabilization for providing reactive power using a version of the Bimodal-Measurements Rule.
  • the states in FIG. 18 include: ⁇ Normal-N, Normal-L, Normal-H, Caution ⁇ .
  • the reactive power device remembers what types of voltages (low vs. high) that it has observed since it was last in the Normal-N state. The reactive power device act cautiously once it has observed both low and high voltages, but not before.
  • the reactive power device In Normal-L state, if the voltage is OK (e.g., on the next measurement cycle, over next three measurement cycles, etc.), the reactive power device enters Normal-N state. If the voltage is low (extremely low), the reactive power device switches in one capacitor (one or more capacitors) without a coin flip and remains in Normal-L state. If the voltage is high or extremely high, the reactive power device flips a coin and switches out a capacitor (or not) depending on the coin flip. Regardless of the coin flip result, the reactive power device enters the Caution state.
  • the reactive power device In Normal-H state, if the voltage is OK (e.g., on the next measurement cycle, over next three measurement cycles, etc.), the reactive power device enters Normal-N state. If the voltage is high (extremely high), the reactive power device switches out one capacitor (one or more capacitors) without a coin flip and remains in Normal-H state. If the voltage is low or extremely low, the reactive power device flips a coin and switches in a capacitor (or not) depending on the coin flip. Regardless of the coin flip result, the reactive power device enters the Caution state.
  • the Caution state is like the Caution state in the two-state configuration. If voltage is OK, the reactive power device enters Normal-N state. If the next voltage measurement is out of range, the reactive power device flips a coin and switches one capacitor in or out based on the coin flip and the voltage measurement. Regardless of the coin flip result, the reactive power device remains in the Caution state.
  • coin flips may be unnecessary because the reactive power devices have seen only low or high voltages, not both. As a result, they respond quickly to the voltage measurement.
  • tails may vary, e.g., as a function of time or measured voltage. For instance, if the voltage has been consistently high (or consistently low) for several cycles, the probability of taking corrective action (adjusting VAR) may increase. Similarly, if the voltage has been flip-flopping, the probability of taking corrective action may decrease. The probability of acting may also depend on how far the voltage is out of range (guard band), with larger voltage differences leading to a higher probability of corrective action and smaller voltage differences leading to a lower probability of corrective action.
  • the reactive power device may also dynamically redefine "cautious" behavior.
  • the reactive power device may use varying probabilities to switch in or out different numbers of capacitors (e.g., 0, 1, 2, 3, or 4 capacitors) instead of always switching in or out a fixed number of capacitors in response to a given voltage measurement.
  • the reactive power device may also store the number of connected caps n cap at the last Normal state and use this information to inform future actions. For instance, if a unit leaves Normal state via a "switch-all capacitors" action, then it may allow a fast (non-cautious) retreat to a setting with n cap ⁇ 1 capacitors switched in or out and act cautiously after that.
  • one or more embodiments of the caution state controller and method thereof for reactive power devices of this invention may be particularly useful in the following scenarios: (1) using reactive power to control voltage or reactive power flow for a desired network which benefits from taking the first corrective action as soon as possible; (2) the VAR devices do not have stringent limits on the number of adjustments performed; (3) there is no preferred way to know, or control, the number of other VAR devices on the same network, nor is there a good infrastructure for inter-device communication; and (4) the cross-influence between VAR devices or the chance of instability is not negligible.
  • one or more embodiments of the caution mode controller and method thereof for reactive power devices of this invention may be embodied as a system, method or a computer program product.
  • One or more embodiments of the caution mode controller and method thereof for reactive power devices of this invention may take the form of the controllers shown in the accompanying figures, a processor, firmware, hardware, and/or software (including firmware, resident software, micro-code, and the like) or a combination of both hardware and software that may all generally be referred to as a "module", "engine” or “system” which may be part of or separate from the VAR device.
  • One or more embodiments of this invention may take the form of a computer program product embodied in one or more computer-readable medium(s) having computer readable program code/instructions embodied thereon.
  • the computer-readable media or memory may be a computer-readable signal medium or a computer- readable storage medium.
  • a computer-readable storage medium or memory may be, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing.
  • Other examples may include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD- ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.
  • the computer-readable storage medium or memory may be any tangible medium that can contain, or store one or more programs for use by or in connection with one or more processors on a company device such as a computer, a tablet, a cell phone, a smart device, or similar type device.
  • a company device such as a computer, a tablet, a cell phone, a smart device, or similar type device.
  • Computer program code for the one or more programs for carrying out the instructions or operation of one or more embodiments of the caution mode controller and method thereof for reactive power devices this invention may be written in any combination of one or more programming languages, including an object oriented programming language, e.g., C++, Smalltalk, Java, and the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages.
  • object oriented programming language e.g., C++, Smalltalk, Java, and the like
  • conventional procedural programming languages such as the "C" programming language or similar programming languages.
  • These computer program instructions may be provided to a processor of a general purpose computer, a controller, processor, or similar device included as part of one or more VAR devices, or separate from the VAR devices special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
  • the computer program instructions may also be stored in a computer-readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer- readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks.
  • the computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer-implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.
  • inventive embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed.
  • inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein.
  • any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
  • inventive concepts may be embodied as one or more methods, of which an example has been provided. The acts performed as part of the method may be ordered in any suitable way. Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments.
  • a reference to "A and/or B", when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
  • the phrase "at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements.
  • This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified.
  • At least one of A and B can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

L'invention concerne un appareil et des procédés permettant de fournir une puissance réactive à un réseau de distribution électrique et/ou de la faire varier. Dans certains modes de réalisation, un appareil comprend une source de puissance réactive, un commutateur en série avec la source de puissance réactive pour raccorder la source de puissance réactive au réseau de distribution électrique, et un dispositif de commande couplé de manière fonctionnelle au commutateur. Le dispositif de commande est conçu pour effectuer une mesure d'une propriété électrique du réseau de distribution électrique, pour déterminer si la mesure de la propriété électrique est à l'extérieur d'un ensemble prédéfini de valeurs, pour obtenir un nombre aléatoire en réponse à la détermination que la mesure de la propriété électrique est à l'extérieur de l'ensemble prédéfini de valeurs, pour déterminer si le nombre aléatoire satisfait un critère prédéfini, et pour actionner le commutateur de manière à faire varier la puissance réactive fournie au réseau de distribution électrique en réponse à la détermination que le nombre aléatoire satisfait le critère prédéfini.
PCT/US2016/031020 2015-05-05 2016-05-05 Dispositif de commande de mode avertissement et procédé associé pour des dispositifs de puissance réactive WO2016179411A1 (fr)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5081591A (en) * 1990-02-28 1992-01-14 Westinghouse Electric Corp. Optimizing reactive power distribution in an industrial power network
US20040254688A1 (en) * 2003-06-13 2004-12-16 Chassin David P. Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices
US7058484B1 (en) * 1998-12-31 2006-06-06 Patrick Henry Potega Software for configuring and delivering power
US20110285362A1 (en) * 2010-05-23 2011-11-24 Reactive Technologies Oy Reactive power management
US20130096724A1 (en) * 2011-09-16 2013-04-18 Deepakraj Divan Systems and Methods for Edge of Network Voltage Control of a Power Grid

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5081591A (en) * 1990-02-28 1992-01-14 Westinghouse Electric Corp. Optimizing reactive power distribution in an industrial power network
US7058484B1 (en) * 1998-12-31 2006-06-06 Patrick Henry Potega Software for configuring and delivering power
US20040254688A1 (en) * 2003-06-13 2004-12-16 Chassin David P. Electrical power distribution control methods, electrical energy demand monitoring methods, and power management devices
US20110285362A1 (en) * 2010-05-23 2011-11-24 Reactive Technologies Oy Reactive power management
US20130096724A1 (en) * 2011-09-16 2013-04-18 Deepakraj Divan Systems and Methods for Edge of Network Voltage Control of a Power Grid

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