Multiplex communications – Communication techniques for information carried in plural... – Combining or distributing information via time channels
Reexamination Certificate
1998-12-04
2002-05-14
Ngo, Ricky (Department: 2731)
Multiplex communications
Communication techniques for information carried in plural...
Combining or distributing information via time channels
C375S357000
Reexamination Certificate
active
06389041
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a synchronization system and a synchronization method for synchronizing a synchronous-multisystem control apparatus comprising a plurality of systems operating synchronously with each other for each fixed control period. More particularly, the present invention relates to a synchronization system and a synchronization method for synchronizing a synchronous-multisystem control apparatus which comprises a plurality of systems operating synchronously with each other and is capable of at least operating with only one system.
In addition, the present invention relates to a communication control apparatus, or more particularly, relates to a communication control apparatus having an error-recovery function using a repeated-transmission technique.
Furthermore, the present invention relates to a synchronous-multisystem control apparatus comprising a plurality of control circuits and a degradation-control method or, in particular, relates to a synchronous-multisystem control apparatus and a degradation-control method capable of raising the availability factor of a system controlled by the synchronous-multisystem control apparatus and the degradation-control method.
A power converting apparatus comprises a power converter for converting power and a controller for controlling the power converter. The power converter comprises a plurality of switching devices. The power converter turns the switching devices on and off in accordance with gate pulse signals generated by the controller in order to convert power from direct-current power into alternating-current power or vice versa, or to shape the waveform of power. Thus, when an error is generated in the controller, power output by the power converter becomes abnormal.
Causes of generation of an error in the controller include a harsh environment of the site of power converting apparatus in which noise is most likely generated by an external source and introduced into the controller from the external source, radiated light such as alpha light introduced into the controller and deteriorating components of the controller.
Such a power converting apparatus is typically applied to systems such as a power generating system, an industrial production system, a railroad system and a public utility system. As generally known, such systems play roles of importance to society. It is thus necessary to prevent an abnormality from being generated in the power converting apparatus because an abnormality generated in the power converting apparatus will have a big impact on society. For this reason, there is demanded a controller which is capable of normally continuing control of the power converter even if an error is generated in the controller. In order to implement such a controller, a method to operate the controller as a multisystem controller is generally adopted.
In a multisystem control apparatus comprising a plurality of controllers provided for the same plurality of systems, it is necessary to synchronize the systems with each other. Methods for synchronizing a plurality of systems with each other include a technique to synchronize clock signals of the systems and a technique to synchronize beginnings of pieces of processing for the systems.
The technique to synchronize clock signals of systems comprises the step of generating the clock signals having phases shifted from each other by a predetermined number of angular degrees by relatively delaying a source oscillation signal from another, and for any specific system, the steps of:
forming a judgment as to whether the rising or falling edge of a clock signal of each other system leads ahead of or lags behind the rising or falling edge of the clock signal of the specific system;
selecting and outputting a clock signal lagging behind the clock signal of the specific system by a predetermined phase if a result of the judgment indicates that the clock signal of the specific system is leading ahead of a majority of clock signals of the other systems; and
selecting and outputting a clock signal leading ahead of the clock signal of the specific system by a predetermined phase if a result of the judgment indicates that the clock signal of the specific system is lagging behind a majority of clock signals of the other systems.
Technologies for implementing the technique to synchronize clock signals of systems are disclosed in Japanese Patent Laid-open No. Sho 56-47120.
In the case of the technique to synchronize beginnings of pieces of processing for systems, on the other hand, a central processing apparatus of each of the systems is connected to a majority-decision making circuit and a timer. The technique comprises the steps of:
setting a value in the timer with predetermined timing;
outputting time-up information upon the lapse of a predetermined period of time;
supplying pieces of time-up information generated by all the systems to the majority-decision making circuit; and
supplying an output determined by a decision based on a majority and made by the majority-decision making circuit, if any, to the central processing apparatus connected to the majority-decision making circuit as an interrupt.
Technologies for implementing the technique to synchronize beginnings of pieces of processing for systems are disclosed in Japanese Patent Laid-open No. Sho 62-57051.
Control executed by the power converting apparatus, which adopts the technique to synchronize beginnings of pieces of processing for systems and is employed in a power generating system, comprises an iterative sequence of steps of:
sampling the voltage and/or current generated by the power generating system;
determining on/off timings of switching devices employed in the power converting apparatus; and
outputting gate pulse signals.
The sequence is repeated at a period of typically several tens of microseconds to several milliseconds. Thus, the beginnings of pieces of processing, that is, the start points of control periods, can be recognized. As a result, the systems can be loosely coupled.
In a synchronous-multisystem controller employed in a power converting apparatus adopting the technique to synchronize clock signals of the systems, on the other hand, there is a requirement to prevent a control period from being shifted even if the length of time it takes to transmit of a clock signal differs from system to system. It is thus necessary to tightly couple the systems.
In a synchronous-multisystem controller employed in a power converting apparatus, by the way, there is also a requirement to normally continue control of a power converter to sustain the operation of the synchronous-multisystem controller even if an error is generated in a controller of a system. It is thus necessary to prevent a failure occurring in a system from affecting the other systems, that is, to loosely couple the systems.
For the above reason, the technique to synchronize clock signals of systems is not appropriate for a synchronous-multisystem controller employed in a power converting apparatus. It is rather the technique to synchronize beginnings of pieces of processing for systems that can be said to be appropriate for a synchronous-multisystem controller employed in a power converting apparatus.
In the technique to synchronize beginnings of pieces of processing for systems, however, processing is started by an interrupt generated by a decision based on a majority of pieces of time-up information. In consequence, if a decision based on such a majority can not be made for some reasons such as the fact that only a controller of one system is operating, an interrupt can not be generated. In such a case, control to turn on and off switching devices employed in the power converter is suspended inevitably. As a result, there is raised a problem of a flowing overcurrent damaging the switching devices.
A controller which is capable of normally continuing control of the power converter even if an error is generated in the controller is also required for controlling equipment other than a power converting apparatus. Ot
Bando Akira
Hotta Takashi
Imaie Kazuhiro
Kido Mitsuyasu
Morita Yuichiro
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Ngo Ricky
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