NL2021569B1 - Method and system for hierarchically controlling cascaded statcom system - Google Patents

Method and system for hierarchically controlling cascaded statcom system Download PDF

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Publication number
NL2021569B1
NL2021569B1 NL2021569A NL2021569A NL2021569B1 NL 2021569 B1 NL2021569 B1 NL 2021569B1 NL 2021569 A NL2021569 A NL 2021569A NL 2021569 A NL2021569 A NL 2021569A NL 2021569 B1 NL2021569 B1 NL 2021569B1
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sub
module
voltage
output voltage
initialization
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NL2021569A
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Dutch (nl)
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Sun Yao
Hou Xiaocao
Su Mei
Han Hua
Shi Guangze
Liu Zhangjie
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Univ Central South
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    • 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
    • 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
    • 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
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • 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

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Control Of Electrical Variables (AREA)

Abstract

The present disclosure provides a method for hierarchically controlling a cascaded STATCOM system, comprising steps of: generating an initialization 5 parameter set in an upper controller; transmitting the initialization parameter set to multiple lower controllers, wherein each lower controller is configured to connect with and control a sub-module of the system; generating a PWM initialization modulation signal based on the initialization parameter set, and sending the signal to each sub-module so as to start up the system, and gathering voltage and current output 10 from each sub-module after started, obtaining a PWM real-time modulation signal based on calculation on values of the voltage and current gathered, and controlling a voltage output from the sub-module, automatically detaching a connection of a sub-module with the system once detecting abnormal voltage or current, and reporting a message of failure, and receiving the message of failure, regenerating an 15 initialization parameter set and transmitting it to each lower controller so as to reallocate the voltage output from each of remaining sub-modules.

Description

METHOD AND SYSTEM FOR HIERARCHICALLY CONTROLLING CASCADED STATCOM SYSTEM
Technical Field
The present disclosure relates to power electronic control system, particularly to a method and a system for hierarchically controlling a cascaded STATCOM system.
Technical Background
Static Synchronous Compensator, referred to as STATCOM hereinafter, is a typical inverter composed by power electronics, with no DC power source placed in the DC side of the front end, and outputs DC voltage merely by means of DC capacitor. STATCOM is generally applied in reactive power compensation for the power system so as to maintain the voltage stability thereof In Medium/High voltage power system, in view of the limited capability of single power electronic device for withstanding over voltage and over current, the modular multi-level technique is generally adopted. Switching stresses occurred in single electronics device can be lowered through cascading modules of inverter. Compared with the typical neutral point clamped multi-level converter, the cascaded STATCOM system has advantages of independent sub-module, being easily extended, and simple structure etc., and thus is widely applied in the field of the Medium/High voltage power system for reactive compensation.
For the cascaded STATCOM system of the Medium/High voltage power system, it is essential to implement cooperative controlling among the submodules. With respect to the existing study, all the control goals are fulfilled in the centralized structure. In this case, a centralized controller is needed to gather global information such as signals of output voltage and current, voltage across the capacitor placed in the DC side of all modules, and voltage across the grid side, and process and provide given reference signals, so as to implement balanced voltage across the capacitors of all the modules, balanced reactive compensation between the modules, and synchronized frequency with the grid voltage. Since the signals transmitted therefrom are alternative and periodical, it is necessary to adopt high band-width communication during signal transmission.
In addition, since the global information for being gathered is considerably enormous, especially in the case of a large number of cascaded modules of extreme high-voltage power system, the centralized controller with powerful processing capability is needed. In the meantime, one single centralized controller manages all the modules, and thus packet loss or delay taking place in one single module will easily incur communication failure of the whole cascaded STATCOM system. Therefore, the reliability of the whole system will be significantly influenced due to the failure in the single module.
To overcome the above drawbacks, such as lowering requirements for communication bandwidth of cascaded STATCOM system and processing capability of the central controller, and enhancing communication reliability of the whole system, a novel control structure is needed, so that the application scale of the cascaded STATCOM system is expanded and thus the application cost can be further reduced.
Summary of the Invention
To solve the above technical problems, the present disclosure provides a method for hierarchically controlling a cascaded STATCOM system, comprising steps of: generating an initialization parameter set in one upper controller for starting up the cascaded STATCOM system; transmitting, by the upper controller, the initialization parameter set to multiple lower controllers via communication link, with each lower controller controlling each sub-module of the cascaded STATCOM system, wherein each lower controller is configured to connect with and control a corresponding one of sub-modules of the cascaded STATCOM; generating, in each lower controller, a PWM initialization modulation signal based on the initialization parameter set received, and sending the PWM initialization modulation signal as a command to each sub-module in real time so as to start up the cascaded STATCOM system, and in the meantime gathering voltage and current output from each sub-module after started; obtaining, in each lower controller, a PWM real-time modulation signal in each lower controller based on further calculation on values of the voltage and current gathered in real time, and controlling a voltage output from the module correspondingly connected thereto by the PWM real-time modulation signal; automatically detaching a connection of one of the sub-modules with the system, once detecting abnormal voltage or current in said one of sub-modules by the lower controller, and reporting a message of failure to the upper controller; and receiving, by the upper controller, the message of failure, regenerating an initialization parameter set and transmitting it to each lower controller, so as to reallocate the voltage output from each of remaining sub-modules in the cascaded STATCOM system.
According to one embodiment of the disclosure, it is preferred that the initialization parameter set comprises an initialization voltage value, an initialization phase angle and a nominal reactive power reference.
According to one embodiment of the disclosure, the step of generating an initialization parameter set in an upper controller for starting up the cascaded STATCOM system, further comprises sub-steps of: generating the initialization voltage value and the initialization phase angle based on an amplitude value and a phase angle of a voltage detected from a power grid; obtaining a nominal reactive power reference based on schedule and allocation of global system optimization.
According to one embodiment of the disclosure, the step of obtaining PWM real-time modulation signal further comprises sub-steps of: calculating a current reactive power of the sub-module based on voltage and current output from a back end of the sub-module, so as to determine a phase angle reference of an output voltage; calculating a current active power of the sub-module based on a voltage value detected on a front end DC capacitor of the of the sub-module and a voltage reference on the front end DC capacitor, so as to determine an amplitude reference of the output voltage; composing the phase angle reference and the amplitude reference into a voltage reference output from the sub-module; and obtaining the PWM real-time modulation signal to be sent from the lower controller based on the voltage reference.
According to a method for hierarchically controlling cascaded STATCOM system in the disclosure, it is preferred that in the sub-step of calculating a current reactive power of the sub-module based on voltage and current output from a back end of the sub-module so as to determine a phase angle reference of an output voltage, an amplitude of the output voltage from the sub-module to be controlled is obtained based on the following equation:
wherein, V represents the amplitude reference of the output voltage from STATCOM module /, Vo represents the initialization voltage value provided by the upper controller, Vda represents the voltage value on the front end DC capacitor of STATCOM module /, V*dc represents the voltage reference value on the front end DC capacitor, kp is a positive gain, Vg represents an amplitude of the real-time voltage across the power grid, Vg* represents an amplitude of the nominal voltage of the power grid, and Nfew represents the number of modules taking part in compensation for fluctuation of the voltage across the power grid, wherein in general Nfewx 10%N~20%N, N represents the number of sub-modules of cascaded STATCOM system.
According to a method for hierarchically controlling cascaded STATCOM system in the disclosure, in the sub-step of calculating a current reactive power of the sub-module based on voltage and current output from a back end of the sub-module so as to determine a phase angle reference of an output voltage, the phase angle reference of the output voltage from the sub-module to be controlled is obtained based on the following equation:
wherein, co, represents an angular frequency reference of the output voltage from
STATCOM module /, ω* represents a nominal angular frequency of the power grid, kp is a positive control gain, Q* represents a nominal reactive power reference provided by the upper controller, V, represents an amplitude reference of the output voltage from STATCOM module /, and V* represents an amplitude of the output voltage from a single module in a nominal state which is obtained from steady-state analysis.
In one embodiment of the disclosure, it is preferred that impedance of a connection between each sub-module of the cascaded STATCOM system and the power grid is modified to be of resistance characteristic through adding a virtual resistor or placing a real resistor therein, and thus a power transmission characteristic of each STATCOM submodule under a grid-connected with resistance characteristic is represented as follows:
wherein Pi and Qi respectively represent the active power and reactive power output from STATCOM sub-module /, \Zime\ represents impedance modulus of the grid-connected, and Vg and Sg respectively represent the amplitude value and the phase angle of the voltage across the power grid.
According to another aspect of the present disclosure, a system for controlling a cascaded STATCOM system is provided, which comprises: an upper controller, for generating initialization parameter set and transmitting the initialization parameter set via communication link so as to start up the cascaded STATCOM system, multiple lower controllers, each being communicatively connected to the upper controller and connected with a corresponding one of sub-modules of the cascaded STATCOM system via hard wire, each lower controller being used for: generating a PWM initialization modulation signal based on the initialization parameter set received and sending the PWM initialization modulation signal as a control command to each sub-module in real time so as to start up the cascaded STATCOM system, and in the meantime gathering voltage and current
output from the sub-modules after started; obtaining a PWM real-time modulation signal based on further calculation on values of the voltage and current gathered in real time, and controlling a voltage output from the sub-module correspondingly connected thereto by the PWM real-time modulation signal; and automatically detaching a connection of one of the sub-modules with the system, once detecting abnormal voltage or current in said one of the sub-modules, and reporting a message of failure to the upper controller, wherein the upper controller further includes a failure processing unit for receiving the message of failure, regenerating an initialization parameter set and transmitting it to each of multiple lower controllers so as to reallocating the voltage output from each of remaining sub-modules in the cascaded STATCOM system.
According to the system for controlling the cascaded STATCOM system, the lower controller includes: a reactive power frequency controlling unit, for calculating a current reactive power of the sub-module based on voltage and current output from a back end of the sub-module, so as to determine a phase angle reference of an output voltage; an active power voltage controlling unit, for calculating a current active power of the sub-module based on a voltage value detected on a front end DC capacitor of the sub-module and a voltage reference on the front end DC capacitor, so as to determine an amplitude reference of the output voltage; a synthesis unit, for composing the phase angle reference and the amplitude reference into a voltage reference output from the sub-module; and a PWM modulation signal output unit, for obtaining a PWM real-time modulation signal to be sent from the lower controller based on the voltage reference value.
To solve problems in centralized control framework of the cascaded STATCOM system, the present disclosure provides a hierarchical control framework based on multiple time scales, wherein the upper ancillary controller is in charge of services like starting up of the whole system, power allocation and failure management etc., so that single sub-module controlled by the corresponding lower controller can achieve autonomous balancing of voltage across the DC capacitor and autonomous synchronization of the power grid frequency.
Advantages of the present disclosure are generally as follows: 1) the designed hierarchical control can decouple different controls from each other based their different time scales, wherein the upper controller is designed for provide the ancillary services in slow time scale, and the lower controller is designed for controlling of single sub-module in fast time scale, and thus the hierarchy of the control is clear and can be easily implemented. 2) the control method provided herein can achieve autonomous balancing of the voltage on the capacitor and autonomous synchronization of frequency of the power grid without schedule from a central controller; 3) both the physical structure of the cascaded STATCOM system and the lower controller are designed in modules and thus can be flexibly extended; 4) the hierarchical control method presented herein significantly reduces the communication traffic between the upper controller and the lower controllers and thus improves the reliability of the system and reduces the cost of the communication of the system; 5) the hierarchical control method presented herein enable to promote wide application of the cascaded STATCOM system in extreme high voltage power system.
Other features and advantages of the present disclosure will be further explained in the following description, and will partly become self-evident therefrom, or be understood through the implementation of the present disclosure. The objectives and advantages of the present disclosure will be achieved through the structures specifically pointed out in the description, claims, and the accompanying drawings.
Brief Description of the Drawings
The accompanying drawings, together with the embodiments, are provided for a further understanding of the present disclosure, and constitute a part of the description, and are not intended to limit the present disclosure, wherein
Fig. 1 shows a structure block diagram of a cascaded STATCOM system according to one embodiment of the present disclosure;
Fig. 2 shows an internal structure block diagram of one sub-module in the cascaded STATCOM system;
Fig. 3 shows waves of the voltages output from four sub-modules in steady state and the voltage and current of the power grid;
Fig. 4 shows waves of the frequencies of the four sub-modules and the voltage across DC capacitor of the front end; and
Fig. 5 shows waves of active power and reactive power output from the four sub-modules.
Detailed Description of the Embodiments
The present disclosure will be explained in detail below with reference to the accompanying drawings, so that the objective, technical solutions and advantages thereof can be understood more clearly. It should be noted that each embodiment and feature thereof can be combined each other if there is no conflict, and the technical solutions formed thereby are all fallen in the scope of the present disclosure.
As shown in Fig. 1, a hierarchical control structure block diagram of a cascaded STATCOM system according to one embodiment of the present disclosure is presented.
The upper controller is connected to each of multiple lower controllers via communication link. Each lower controller is correspondingly connected with each sub-module in the cascaded STATCOM system via hard wires. The voltage output of each sub-module is controlled by the lower controller correspondingly connected therewith. Then, the upper controller sends a start-up command to combine the whole cascaded STATCOM system into the power grid.
As described above, the control system of the present disclosure is divided into two layers from time scale of response control, one is a layer with slow time scale, and the other is a layer with fast time scale. There is a low band-width communication between the upper controller with slow time scale and the lower controller with fast time scale. The content of the low band-width communication is mostly that the upper controller sends a startup command for the system to the lower controller, and the lower controller reports a message of failure to the upper controller when detecting a failure in the STATCOM sub-module being correspondingly connected therewith. In this way, the upper controller is in charge of services like starting up of the whole system, power compensation and failure management etc., and the lower controllers respectively and independently control each module being connected therewith so that single sub-module controlled by the corresponding lower controller can enable autonomous balancing of voltage across the DC capacitor, autonomous synchronization of the power grid frequency, and given reactive power compensation.
In particular, the upper controller generates initialization parameter set for starting up the cascaded STATCOM system based on calculation and schedule and allocation of the global system optimization. The initialization parameter set comprises initialization voltage value, initialization phase angle and reactive power for compensation. The upper controller generates initialization phase angle So and initialization voltage value Vo for starting up the STATCOM system based on information of amplitude and phase angle of the voltage of the power grid obtained by a phase locked loop, so as to achieve a grid connection with no impact of the cascaded STATCOM system. Reactive power reference Q* to be compensated can be obtained by schedule and allocation of the global system optimization.
Then, the initialization parameter set as mentioned above can be transmitted to each lower controller via the communication links between the upper controller and each lower controller.
Multiple lower controllers generate PWM initialization modulation signal based on the received initialization parameter set and send the PWM initialization modulation signal as a command to each submodule in real time which is correspondingly connected therewith so as to start up the cascaded STATCOM system.
Meanwhile, the lower controllers gather voltage and current output from the sub-modules after started, generate a PWM real-time modulation signal based on further calculation on the gathered voltage and current value, and control voltage output from the sub-module being correspondingly connected therewith by means of the PWM real-time modulation signal.
To ensure synchronization of output voltage, the lower controller of the present disclosure immediately gather the voltage on the DC capacitor of the front end of STATCOM sub-module to calculate the control, which is totally different from the prior art.
When the lower controllers detect abnonnal voltage or current value in the sub-modules, they can automatically detach the connection of one of the modules with the system and make the sub-module with failure in short circuit through a bypass switch, and then report a message of failure to the upper controller via the communication link.
The upper controller receives the reported failure message, and regenerates an initialization parameter set and transmitting it to each of multiple lower controllers via the communication link so as to reallocate the voltage output from each of remaining modules in the cascaded STATCOM system.
The reallocated initialization voltage value Vo can be calculated as the following equation:
wherein N represents the total number of STATCOM modules, Nm,r represents the number of STATCOM modules in normal operating state, and V* represents amplitude of output voltage of single sub-module in nominal state obtained by steady-state analysis.
In the case of failure, only the amplitude of the voltage to be reallocated needs to be recalculated by the upper controller, rather than the initialization phase angle and reactive power to be compensated.
As shown in Fig. 2, the internal structure of the lower controller i being connected with the sub-module i is presented, hi the figure, the lower controller i further includes reactive power frequency controlling unit, active power voltage controlling unit, synthesis unit and PWM modulation signal output unit. The reactive power frequency controlling unit is used for calculating the current reactive power of the submodule based on the voltage and current output from the back end, so as to determine the phase angle reference of the output voltage.
In Fig. 2, reactive power real output (λ of submodules can be calculated by a reactive power calculation unit. By taking nominal reactive power reference Q* and reactive power real output O, and nominal angular frequency ω* as input, the angular frequency reference oj, of the output voltage to be used to control output can be calculated. Then the phase angle reference can be obtained by transforming the angular frequency reference oj,.
In particular, the angular frequency reference ω, of the voltage is obtained based on the following equation:
wherein, ω, represents an angular frequency reference of the output voltage from STATCOM module /, ω* represents a nominal angular frequency of the power grid, kp is a positive gain, Q* represents a nominal reactive power reference provided by the upper controller, Vi represents an amplitude of the output voltage from STATCOM module /, and V* represents the amplitude of the output voltage from a single module in the nominal state which is obtained from steady-state analysis.
Additionally, the active power component of the sub-module to be controlled can be obtained by calculating on voltage Vda on DC capacitor of the front end gathered by the lower controller. Thus, this component of the lower controller can be called active voltage control unit. As shown in Fig.2, the amplitude reference V, of the voltage output from the sub-module to be controlled can be determined by calculating the current active power output based on the voltage value gathered on DC capacitor of the front end of the sub-module and the voltage reference on the DC capacitor of
the front end:
wherein, Vi represents the amplitude reference of the voltage output from STATCOM module /, Vo represents the initialization voltage value provided by the upper controller, V,k·, represents the voltage value on the front end DC capacitor of STATCOM module /, V*dc represents the voltage reference on the front-end DC capacitor of, kP is a positive gain, Vg represents an amplitude of the real-time voltage across the power grid, Vg* represents an amplitude of the nominal voltage of the power grid, and 7V/ew represents the number of sub-modules taking part in compensation for fluctuation of the voltage across the power grid, wherein in general Λ10%N~20%N, N representing the number of sub-modules in the cascaded STATCOM system.
As shown in Fig.2, the calculated amplitude reference and angular frequency reference of the output voltage are transmitted to a synthesis unit (not shown), and then the synthesis unit composes the phase reference and the amplitude reference into a voltage reference value output from the sub-module to be correspondingly controlled.
Since output characteristic of each sub-module is no longer a typical current supply, but a voltage supply, the frequency of the output voltage can be automatically synchronized with the power grid, and there is no need to gather the frequency of the power grid in real time and thus significantly reduces the communication traffic of the controllers. In addition, since the voltage output from single STATCOM sub-module can be controlled based on the voltage on the capacitor of the sub-module in the present disclosure, and balance between active power loss and reactive power loss of the sub-module is maintained reasonably, autonomous balance of the voltage on local DC capacitor can be achieved.
To control the sub-modules in PWM, the resulted voltage reference is sent to PWM modulation signal output unit. PWM modulation signal output unit creates PWM real-time modulation signal of the lower controller based on the voltage
reference.
Impedance of the connection between each module of the cascaded STATCOM system and the power grid is can be modified to be of resistance characteristic through a virtual resistor or placing a real resistor therein, and thus a power transmission characteristic of each STATCOM sub-module with grid-connected resistance characteristic can be represented as follows:
wherein P, and 0, respectively represent the active power and reactive power of STATCOM module /, |Z&!e| represents impedance modulus of the grid-connected, and Vg and respectively represent the amplitude value and the phase angle of the voltage across the power grid.
To verify the feasibility of the proposed control scheme, a low-voltage system including four cascaded modules is also implemented based on real-time HIL tests on OPAL-RT platform. The nominal reactive power capacity of each STATCOM module is 20 kVar, and the active power loss of each module is about 1 kW. The results of the real-time HIL tests are as shown in Fig. 3-5.
Fig. 3 shows waves of the voltages output from four sub-modules in steady state and the voltage and current of the power grid. From Fig. 3, in steady state, the four sub-modules have same amplitude, phase angle and frequency of the output voltage, and thus the output voltage from the sub-modules are balanced.
Fig. 4 shows waves of the frequencies of the four sub-modules and the voltage across DC capacitor of the front end. From Fig. 4, in several time periods after starting up, the system is in steady state. Meanwhile, the four sub-modules have same frequency of 50Hz as the power grid, and thus achieving autonomous frequency synchronization. In addition, the voltage on DC capacitor of the four sub-modules are basically maintained at 200V, and thus achieving a stable voltage output.
Fig. 5 shows power response of the four sub-modules, i.e., output active power response and output reactive power response. From Fig. 5, in state of nominal voltage of the power grid, the four sub-modules absorb 5kW active power to compensate the loss by the sub-modules itself, and thus achieve balance between the absorption and loss of the power. In addition, all the four sub-modules can make lOkVar of nominal reactive power compensation, and thus support the steady of the voltage of the power grid.
It should be understood that the embodiment disclosed herein is not limited to the specific structures or process steps disclosed herein, but should be extended equivalents of the technical features which persons skilled in the art can appreciate. It should be still understood, terms used herein are merely for describing specific embodiments and not intended to be limitation. “One embodiment” or “embodiments” mentioned in the description indicate that specific features, structures, or characteristics are involved in at least one embodiment of the present disclosure. Therefore, the phrases “one embodiment” or “embodiments” in each place throughout the description do not always mean the same embodiment.
Although the above examples are intended for explaining a principle of the present disclosure in one or multiple applications, for the person skilled in the art, it is obvious to make various modifications to formations, usages, or details of implementation without departing away from the concept and idea of the present disclosure on the condition that there is no need for inventive labors.

Claims (9)

1. Werkwijze voor het hiërarchisch besturen van een cascade-STATCOM-systeem, omvattende stappen van: genereren van een initialisatieparameterset in een hoger besturingsorgaan voor het opstarten van het cascade-STATCOM-systeem: zenden, door het hogere besturingsorgaan, van de initialisatieparameterset naar meerdere lagere besturingsorganen via een communicatieverbinding, waarbij elk lager besturingsorgaan is ingericht om met een corresponderend exemplaar van submodules van het cascade-STATCOM-systeem verbinding te maken en deze te besturen; genereren, in elk lager besturingsorgaan, van een PWM-initialisatiemodulatiesignaal gebaseerd op de ontvangen initialisatieparameterset, en zenden van het PWM-initialisatiemodulatiesignaal als een commando naar elke submodule in realtime om het cascade-STATCOM-systeem op te starten, en in de tussentijd verzamelen van uitgangsspanning- en stroom van elke submodule nadat deze is gestart; verkrijgen, in elk lager besturingsorgaan, van een PWM-realtimemodulatiesignaal gebaseerd op verdere berekening op in realtime verzamelde waardes van spanning en stroom, en besturen van een uitgangsspanning van de submodule die daarmee corresponderend is verbonden door het PWM-realtimemodulatiesignaal; automatisch verbreken van een verbinding van een van de submodules met het STATCOM-systeem, wanneer abnormale spanning of stroom is gedetecteerd in genoemd exemplaar van de submodules door het lagere besturingsorgaan, en rapporteren van een foutbericht aan het hogere besturingsorgaan; en ontvangen, door het hogere besturingsorgaan, van het foutbericht, opnieuw genereren van een initialisatieparameterset en zenden daarvan naar elk lager besturingsorgaan om de uitgangsspanning van elke resterende submodule in het cascade-STATCOM-systeem opnieuw toe te wijzen.A method for hierarchically controlling a cascade STATCOM system, comprising the steps of: generating an initialization parameter set in a higher controller for starting the cascade STATCOM system: sending, by the higher controller, the initialization parameter set to a plurality of lower control members via a communication link, each lower control member being adapted to connect and control a corresponding copy of sub-modules of the cascade STATCOM system; generating, in each lower controller, a PWM initialization modulation signal based on the received initialization parameter set, and sending the PWM initialization modulation signal as a command to each sub-module in real-time to start up the cascade STATCOM system, and in the meantime collecting output voltage and current of each sub-module after it has been started; obtaining, in each lower controller, a PWM real-time modulation signal based on further calculation on values of voltage and current collected in real time, and controlling an output voltage of the sub-module correspondingly connected thereto by the PWM real-time modulation signal; automatically disconnecting one of the sub-modules from the STATCOM system when abnormal voltage or current is detected in said sub-module copy by the lower controller, and reporting an error message to the higher controller; and receiving, by the higher controller, the error message, regenerating an initialization parameter set and sending it to each lower controller to reassign the output voltage of each remaining sub-module in the cascade STATCOM system. 2. Werkwijze voor het hiërarchisch besturen van een cascade-STATCOM-systeem volgens conclusie 1, waarbij de initialisatieparameterset een initialisatiespanningswaarde, een initialisatiefasehoek, en een nominaal-reactief-vermogensreferentie omvat.The method for hierarchically controlling a cascade STATCOM system according to claim 1, wherein the initialization parameter set comprises an initialization voltage value, an initialization phase angle, and a nominal reactive power reference. 3. Werkwijze voor hiërarchisch besturen van een cascade-STATCOM-systeem volgens conclusie 2, waarbij de stap van het genereren van een initialisatieparameterset in een hoger besturingsorgaan voor het opstarten van het cascade-STATCOM-systeem verder deelstappen omvat van: genereren van de initialisatiespanningswaarde en de initialisatie-fasehoek gebaseerd op een amplitudewaarde en een fasehoek van een vanuit een elektriciteitsnetwerk gedetecteerde spanning; en verkrijgen van een nominaal-reactief-vermogensreferentie gebaseerd op planning en toewijzing van de globale systeemoptimalisatie.The method of hierarchically controlling a cascade STATCOM system according to claim 2, wherein the step of generating an initialization parameter set in a higher controller for starting the cascade STATCOM system further comprises sub-steps of: generating the initialization voltage value and the initialization phase angle based on an amplitude value and a phase angle of a voltage detected from an electricity network; and obtaining a nominal reactive power reference based on planning and allocation of the global system optimization. 4. Werkwijze voor hiërarchisch besturen van een cascade-STATCOM-systeem volgens conclusie 3, waarbij de stap van het verkrijgen van het PWM-realtimemodulatiesignaal verder deelstappen omvat van: berekenen van een huidig reactief vermogen van de submodule gebaseerd op de uitgangsspanning en -stroom van een backend van de submodule, om een fasehoek-referentie van een uitgangsspanning te bepalen; berekenen van een huidig actief uitgangsvermogen van de submodule gebaseerd op een spanningswaarde gedetecteerd op een frontend gelijkstroomcondensator van de submodule en een spanningsreferentie van de frontend gelijkstroomcondensator, om een amplitude-referentie van de uitgangsspanning te bepalen; samenstellen van de fasehoekreferentie en de amplitudereferentie tot een uitgangsspanningsreferentie van de submodule; en verkrijgen van het vanuit het lagere besturingsorgaan te zenden PWM-realtimemodulatiesignaal gebaseerd op de spanningsreferentie.The method of hierarchically controlling a cascade STATCOM system according to claim 3, wherein the step of obtaining the PWM real-time modulation signal further comprises sub-steps of: calculating a current reactive power of the sub-module based on the output voltage and current of a backend of the sub-module, to determine a phase angle reference of an output voltage; calculating a current active output power of the sub-module based on a voltage value detected on a front-end DC capacitor of the sub-module and a voltage reference of the front-end DC capacitor, to determine an amplitude reference of the output voltage; composing the phase angle reference and the amplitude reference to an output voltage reference of the sub-module; and obtaining the PWM real-time modulation signal to be sent from the lower controller based on the voltage reference. 5. Werkwijze voor hiërarchisch besturen van een cascade-STATCOM-systeem volgens conclusie 4, waarbij in de deelstap van het berekenen van een huidig reactief vermogen van de submodule gebaseerd op de uitgangsspanning en -stroom van een backend van de submodule, om een fasehoek-referentie van een uitgangsspanning te bepalen, een amplitude van de uitgangsspanning van de te besturen submodule wordt verkregen gebaseerd op de volgende vergelijking:The method of hierarchically controlling a cascade STATCOM system according to claim 4, wherein in the sub-step of calculating a current reactive power of the sub-module based on the output voltage and current of a back-end of the sub-module, around a phase angle To determine the reference of an output voltage, an amplitude of the output voltage of the sub-module to be controlled is obtained based on the following equation: waarbij Vi de amplitudereferentie van de uitgangsspanning van STATCOM-module / representeert, V,» de initialisatiespanningswaarde verschaft door het hogere besturingsorgaan representeert, Vdd de spanningswaarde op de frontend gelijkstroomcondensator van STATCOM-module i representeert, V*dc de spanningsreferentie op de frontend gelijkstroomcondensator representeert, kp een positieve versterking is, Vg een amplitude van de realtime spanning over het elektriciteitsnetwerk representeert, Vs* een amplitude van dewhere Vi represents the amplitude reference of the output voltage of STATCOM module, V, represents the initialization voltage value provided by the higher controller, Vdd represents the voltage value on the frontend DC capacitor of STATCOM module i, V * dc represents the voltage reference on the frontend DC capacitor , kp is a positive gain, Vg represents an amplitude of the real-time voltage across the electricity network, Vs * an amplitude of the nominale spanning van het elektriciteitsnetwerk representeert, en N/tw het aantal submodules dat deelneemt aan het compenseren van fluctuatie van de spanning over het elektriciteitsnetwerk representeert, waarbij in het algemeen Njhv~ 10%N~20%N, waarbij TV het aantal submodules in het cascade-STATCOM-systeem representeert.nominal voltage of the electricity network, and N / tw represents the number of sub-modules participating in compensating for fluctuation of the voltage across the electricity network, with generally Njhv ~ 10% N ~ 20% N, where TV represents the number of sub-modules in the cascade STATCOM system. 6. Werkwijze voor hiërarchisch besturen van een cascade-STATCOM-systeem volgens conclusie 5, waarbij in de deelstap van het berekenen van een huidig reactief vermogen van de submodule gebaseerd op de uitgangsspanning en -stroom vanuit een backend van de submodule, om een fasehoekreferentie van een uitgangsspanning te bepalen, de fasehoekreferentie van de uitgangsspanning van de te besturen submodule wodrt verkregen gebaseerd op de volgende vergelijking:The method of hierarchically controlling a cascade STATCOM system according to claim 5, wherein in the sub-step of calculating a current reactive power of the sub-module based on the output voltage and current from a backend of the sub-module, to a phase angle reference of to determine an output voltage, the phase angle reference of the output voltage of the sub-module to be controlled is obtained based on the following equation: waarbij co, een hoekfrequentie-referentie van de uitgangsspanning van STATCOM-module i representeert, co* een nominale hoekfrequentie van het elektriciteitsnetwerk representeert, kp een positieve versterking is, Q* een nominaal-reactief-vermogensreferentie verschaft door het hogere besturingsorgaan representeert, Vi een amplitude van de uitgangsspanning van STATCOM-module i representeert, en V* de amplitude van de uitgangsspanning van een enkele module in de nominale toestand welke aan de hand van een stationaire-toestandsanalyse is verkregen.where co, represents an angular frequency reference of the output voltage of STATCOM module i, co * represents a nominal angular frequency of the electricity network, kp is a positive gain, Q * represents a nominal-reactive power reference provided by the higher controller, Vi represents a amplitude of the output voltage of STATCOM module i, and V * represents the amplitude of the output voltage of a single module in the nominal state obtained by a stationary state analysis. 7. Werkwijze voor hiërarchisch besturen van een cascade-STATCOM-systeem volgens conclusie 6, waarbij impedantie van de verbinding tussen elke module van het cascade-STATCOM-systeem en het elektriciteitsnetwerk gewijzigd kan worden om weerstandskarakteristiek te hebben door het toevoegen van een virtuele weerstand of plaatsing van een echte weerstand daarin, en zodoende een vermogenstransmissiekarakteristiek van elke STATCOM-submodule met netwerk-verbonden weerstandskarakteristiek als volgt gerepresenteerd kan worden:The method of hierarchically controlling a cascade STATCOM system according to claim 6, wherein impedance of the connection between each module of the cascade STATCOM system and the electricity network can be changed to have resistance characteristic by adding a virtual resistor or placement of a real resistor therein, and thus a power transmission characteristic of each STATCOM sub-module with network-connected resistor characteristic can be represented as follows: waarbij Pi respectievelijk Qj het actief uitgangsvermogen en reactief uitgangsvermogen van STATCOM-module / representeren, \Znne\ de impedantiemodulus van het verbonden netwerk representeert, en Vg respectievelijk Óg de amplitudewaarde en de fasehoek van de spanning over het elektriciteitsnetwerk representeren.wherein Pi and Qj respectively represent the active output power and reactive output power of STATCOM module, \ Znne \ represents the impedance modulus of the connected network, and Vg respectively represent the amplitude value and the phase angle of the voltage across the electricity network. 8. Systeem voor hiërarchisch besturen van een cascade-STATCOM-systeem, omvattende: een hoger besturingsorgaan voor het genereren van een initialisatieparameterset en het zenden van de initialisatieparameterset via een communicatieverbinding om het cascade-STATCOM-systeem op te starten, meerdere lagere besturingsorganen, elke communicatief verbonden met het hogere besturingsorgaan en verbonden met een corresponderend exemplaar van de submodules van het cascade-STATCOM-systeem via een kabel, waarbij elk lager besturingsorgaan wordt gebruikt voor: genereren van een PWM-initialisatiemodulatiesignaal gebaseerd op de ontvangen initialisatieparameterset, en zenden van het PWM-initialisatiemodulatiesignaal als een commando naar elke submodule in realtime om het cascade-STATCOM-systeem op te starten, en in de tussentijd verzamelen van uitgangsspanning en -stroom van de submodules nadat deze zijn gestart; verkrijgen van een PWM-realtimemodulatiesignaal gebaseerd op verdere berekening op in realtime verzamelde spanning en stroom, en besturen van een uitgangsspanning van de submodule die daarmee corresponderend is verbonden door het PWM-realtimemodulatiesignaal; en automatisch verbreken van een verbinding van een van de submodules met het cascade-STATCOM-systeem, wanneer abnormale spanning of stroom is gedetecteerd in genoemd exemplaar van de submodules, en rapporteren van een foutbericht aan het hogere besturingsorgaan, waarbij het hogere besturingsorgaan verder een foutverwerkingseenheid omvat voor het ontvangen van het foutbericht, opnieuw genereren van een initialisatieparameterset en zenden daarvan naar elke van meerdere lagere besturingsorganen om de uitgangsspanning van elke van de resterende submodules in het cascade-STATCOM-systeem opnieuw toe te wijzen.A system for hierarchically controlling a cascade STATCOM system, comprising: a higher controller for generating an initialization parameter set and sending the initialization parameter set via a communication link to start up the cascade STATCOM system, multiple lower controllers, each communicatively connected to the higher controller and connected to a corresponding copy of the sub-modules of the cascade STATCOM system via a cable, each lower controller being used to: generate a PWM initialization modulation signal based on the received initialization parameter set, and send the PWM initialization modulation signal as a command to each submodule in real time to start the cascade STATCOM system, and in the meantime collect output voltage and current from the submodules after they are started; obtaining a PWM real-time modulation signal based on further calculation on voltage and current collected in real time, and controlling an output voltage of the sub-module correspondingly connected to it by the PWM real-time modulation signal; and automatically disconnecting a connection from one of the submodules to the cascade STATCOM system when abnormal voltage or current is detected in said instance of the submodules, and reporting an error message to the higher controller, the higher controller further including an error processing unit for receiving the error message, regenerating an initialization parameter set and sending it to each of a plurality of lower controllers to reassign the output voltage of each of the remaining sub-modules in the cascade STATCOM system. 9. Systeem voor besturen van een cascade-STATCOM-systeem volgens conclusie 8, waarbij het lagere besturingsorgaan omvat: een reactief-vermogenbesturingseenheid, voor het berekenen van een huidig reactief vermogen van de submodule gebaseerd op uitgangsspanning en -stroom van een backend van de submodule, om een fasehoekreferentie van een uitgangsspanning te bepalen; een actief-vermogenspanningsbesturingseenheid, voor het berekenen van een huidig actief vermogen van de submodule gebaseerd op een spanningswaarde gedetecteerd op een frontend gelijkstroomcondensator van de submodule en een spanningsreferentie van de frontend gelijkstroomcondensator, om een amplitudereferentie van de uitgangsspanning te bepalen; een synthese-eenheid, voor het samenstellen van de fasehoekreferentie en de amplitudereferentie tot een uitgangsspanningsreferentie van de submodule; en een PWM-modulatiesignaaluitvoereenheid voor het verkrijgen van een vanuit het lagere besturingsorgaan te zenden PWM-realtimemodulatiesignaal gebaseerd op de spanningsreferentiewaarde.The cascade STATCOM system control system of claim 8, wherein the lower controller comprises: a reactive power control unit, for calculating a current reactive power of the sub-module based on output voltage and current of a backend of the sub-module to determine a phase angle reference of an output voltage; an active power voltage control unit, for calculating a current active power of the sub-module based on a voltage value detected on a front-end DC capacitor of the sub-module and a voltage reference of the front-end DC capacitor, to determine an amplitude reference of the output voltage; a synthesis unit, for compiling the phase angle reference and the amplitude reference to an output voltage reference of the sub-module; and a PWM modulation signal output unit for obtaining a PWM real-time modulation signal to be sent from the lower controller based on the voltage reference value.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080232143A1 (en) * 2007-03-16 2008-09-25 Chia-Chi Chu Method of designing a static synchronous compensator based on passivity-based control
WO2015078471A1 (en) * 2013-11-28 2015-06-04 Vestas Wind Systems A/S Reconfiguration of the reactive power loop of a wind power plant
CN105977994A (en) * 2016-01-15 2016-09-28 湖南大学 Cascaded STATCOM reactive power compensation control method based on current feedback correction optimization
CN108233394A (en) * 2018-02-10 2018-06-29 国家电网公司 A kind of capacitive coupling voltage balancing control method suitable for Y type chain types STATCOM

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102073501A (en) * 2011-01-04 2011-05-25 浙江工商大学 Method for implementing central controller of network equipment based on logic functional block
CN103474984B (en) * 2013-03-13 2015-04-01 湖南工业大学 Cascade STATCOM direct-current capacitor voltage balance control method in wind power plant environment
CN104218592A (en) * 2014-02-26 2014-12-17 锦州拓新电力电子有限公司 Direct current capacitor voltage control method for power units of SVG (static VAR generator)
US10096998B2 (en) * 2014-07-23 2018-10-09 Mitsubishi Electric Research Laboratories, Inc. Distributed reactive power control in power distribution systems

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080232143A1 (en) * 2007-03-16 2008-09-25 Chia-Chi Chu Method of designing a static synchronous compensator based on passivity-based control
WO2015078471A1 (en) * 2013-11-28 2015-06-04 Vestas Wind Systems A/S Reconfiguration of the reactive power loop of a wind power plant
CN105977994A (en) * 2016-01-15 2016-09-28 湖南大学 Cascaded STATCOM reactive power compensation control method based on current feedback correction optimization
CN108233394A (en) * 2018-02-10 2018-06-29 国家电网公司 A kind of capacitive coupling voltage balancing control method suitable for Y type chain types STATCOM

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