JP5099873B2 - Inverter current limit control - Google Patents

Description

  The present invention relates to a vehicle auxiliary system that supplies power to a same load by independent control in a parallel system in which a plurality of auxiliary power supply devices that are inverters configured by power conversion switching elements and convert a DC power supply to an AC power supply are connected in parallel. The present invention relates to a power supply device.

FIG. 1 shows an embodiment of a parallel system in which a plurality of auxiliary power supply devices are connected. The auxiliary power supply includes an input contactor 2 connected in series to the input power supply 1, a charging resistor 3 and a charging resistor short contactor 4 for preventing an inrush current, an input filter reactor 5, and an input power supply 1. A backflow prevention element 6 for preventing backflow, an input circuit comprising a security capacitor 7 in the event of a power failure of the input power supply 1, a discharge resistor 8 for discharging the charge of the security capacitor 7, and a discharge contactor 9. The output circuit includes a discharge circuit, a power conversion switching element 10, an output filter reactor 11 and output filter capacitor 12 for smoothing the inverter current 14, and an output contactor 13 for outputting the output current 15 to the load 16. The

A plurality of auxiliary power supplies having the same configuration perform independent control so as to balance the output current 15 with respect to the load 16 and to supply the same power.

In the parallel system, a plurality of auxiliary power supply devices are connected to the load 16, and even when a failure occurs in a part of the auxiliary power supply device and the output is stopped, the output contactor 13 of the stopped auxiliary power supply device is instantaneously connected. By opening, it is a system that can continue to supply power to the load without interruption by other auxiliary power supply devices.

However, in a parallel system in which different control methods such as voltage control and current control are performed by each auxiliary power supply, the auxiliary power supply responsible for voltage control stops and the parallel system is configured only by the current-controlled auxiliary power supply The output voltage may fluctuate and the load 16 may be damaged. Thus, each auxiliary power supply device performs voltage control, so that a parallel system that continues power supply without interruptions as long as the output capacity is allowed is put into practical use, regardless of the auxiliary power supply device that fails and stops. .
Japanese Patent Publication No. 10-94259

  When each auxiliary power supply performs voltage control, the balance of the output capacity is equalized by detecting the cross current between the auxiliary power supplies, but the phase of the output voltage of each auxiliary power supply is different at the time of startup. A large cross current is generated. As a phase synchronization method at the time of startup, a method of giving a startup command to each auxiliary power supply device at the same time is used. However, it is difficult to achieve complete synchronization, and high-speed phase synchronization control is necessary.

  However, when performing synchronous control from a cross current using transmission such as train information devices, detection of the cross current depends on the transmission speed, period, etc., so a delay occurs in the detection, and the phase synchronization is delayed, resulting in a load There is a problem that overcurrent occurs.

According to the first aspect of the present invention, in a parallel system in which outputs of a plurality of auxiliary power supply devices that perform phase synchronization control are connected, the detected inverter current is coordinate-transformed to obtain an effective part and an ineffective part of the inverter current. When the valid and invalid values of the inverter current reach the set conditions, the output voltage command value including the phase synchronization control is increased or decreased according to the value, and the output control command is issued while continuing the phase synchronization control. It is characterized by limiting.

  In a parallel system composed of multiple auxiliary power supplies that each perform voltage control, when the voltage phase of each auxiliary power supply is different at startup, etc., power is supplied to the load by preventing overcurrent due to delay in synchronous control Can be continued.

  An inverter current is detected by a detector attached for the purpose of output control, protection detection, etc., and coordinate conversion is performed to convert it into rotating coordinates. A limiter value is provided for each of the effective and ineffective portions of the inverter current, and when the limiter value is exceeded, the output voltage command is reduced according to that value, thereby suppressing the current flowing through the load to a safe level. At that time, the phase correction by the cross current is continuously performed to synchronize the phases of the auxiliary power supply devices.

In FIG. 2, the feedback system control command for the valid and invalid values is obtained by converting the output voltage command value including the parallel control element obtained from the output voltage command value, the output voltage, the output current, and the cross current feedback value into the rotating coordinate system. The three-phase inverter current is converted into an effective current and a reactive current by performing coordinate conversion from stationary coordinates to rotating coordinates.

When the inverter current rotational coordinate system active current and reactive current exceed the limiter upper limit, the feedback system control command is attenuated by a value multiplied by an arbitrary control gain G, and the inverter current rotational coordinate system active current and reactive current are limited. When the value falls below the lower limit, the feedback system control command is amplified by a value multiplied by an arbitrary control gain G.

The limiter lower limit of the rotating coordinate system effective current of the inverter current is an arbitrary value less than 0 ampere, and the upper limit is an arbitrary value equal to or greater than the rated value of the inverter current effective amount. The limiter of the rotating coordinate system reactive current of the inverter current is an arbitrary value that is not 0 amperes in both the upper and lower limits.

  In this way, by increasing or decreasing the output control command according to the inverter current value, the output voltage value is reduced until the phase of each auxiliary power supply device is synchronized by cross current control or the like, preventing the output overcurrent from flowing to the load, Enables parallel synchronous operation.

In FIG. 3, the feedback system control command for valid and invalid is obtained by converting an output voltage command value and an output voltage control command including a parallel control element obtained from a feedback value such as output voltage, output current, cross current, and the like into a rotating coordinate system. The three-phase inverter current is converted into an effective current and a reactive current by performing coordinate conversion from stationary coordinates to rotating coordinates.

  In order to prevent an inrush current with respect to the load 16, the auxiliary power supply for vehicles performs a soft start so as to reach the rated output voltage by gradually increasing the output voltage from 0 volts when starting the inverter. Therefore, the effective amount of the inverter current fluctuates transiently until the rated output voltage is reached regardless of the parallel operation.

Therefore, by setting the limiter value at the time of soft start according to the output voltage as shown in (Equation 1), it is possible to reduce the rise delay until the rated output voltage value at the time of soft start. In (Expression 1), Ls is the limit value of the inverter current for the effective or ineffective portion, L is the limit value of the inverter current for the effective or ineffective portion at the rated output, and Vcs is the output voltage command value during the soft start, Vcr is a voltage command value at the rated output. However, Vcs does not include control terms due to inverter current limitation, output voltage, and output current feedback.
Ls = L × Vcs / Vcr ―――― (Formula 1)

  When Vcs is smaller than Vcr, the inverter current is also small. Therefore, by setting the absolute value of the limiter value Ls to be small, the rotating coordinate system effective current and reactive current of the inverter current are set to the limiter values according to the output voltage value. Thus, the amount of increase / decrease in the feedback system command value can be reduced, and the time required to reach the rated output voltage can be shortened.

It is explanatory drawing which showed the Example of the parallel system which connected the some auxiliary power supply apparatus. It is explanatory drawing which showed the calculation method of inverter current limiting control. Example 1 It is explanatory drawing which showed the calculation method of inverter current limiting control. (Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input power supply 2 Input contactor 3 Charging resistor 4 Charging resistor short contactor 5 Input filter reactor 6 Backflow prevention element 7 Capacitor for security at the time of input power failure 8 Discharge resistor 9 Discharge contactor 10 Power conversion switching element ( Inverter)
11 output filter reactor 12 output filter capacitor 13 output contactor 14 inverter current 15 output current 16 load

Claims (1)

Vehicles connected in parallel to the same load and connected to each other to capture the output current information of other devices, and adjust the voltage phase so that the output current phase of the own device matches that of the other devices (each performing phase synchronization control) In the auxiliary power supply device, for each of the effective part (the same phase as the voltage phase) and the ineffective part (the component shifted by 90 ° from the voltage phase) of the own output voltage (Equation 1) Ls = L × Vcs / Vcr,
Ls is the limiter value of the inverter current that is effective or ineffective,
L is the limit value of the inverter current that is valid or invalid at the rated output,
Vcs is an output voltage command value during soft start, Vcr is a voltage command value at rated output,
An inverter current limit control system characterized in that a limiter is provided in consideration of soft start conditions based on the fact that the Vcs does not include a control term based on inverter current limit, output voltage, or output current feedback.

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