JP6658012B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device connected to a power system via a system connection switch, and in particular, can safely open a system connection switch, disconnect a load from a power system, and shift to independent operation when a system abnormality occurs. It relates to a possible power converter.

  FIG. 2 is a circuit diagram of a power converter (hereinafter, referred to as a parallel voltage sag compensator) connected to a power system. The parallel type sag compensator connected to the electric power system via a circuit breaker (not shown) includes a system interconnection switch (hereinafter, referred to as a high-speed switch) 1 and a PCS (Power Conditioning Subsystem) 2. The PCS 2 includes a switching unit including an LC filter 3 and an AC / DC converter 4 such as an IGBT. A power storage device 5 such as a secondary battery or an electric double layer capacitor is connected to a DC link of the AC / DC converter 4 having an inverter / converter function. AC power is supplied via the AC power supply.

  When the power system is normal, the parallel voltage sag compensator is connected to the system via the high-speed switch 1 as shown in FIG. 3 to charge and discharge power for the purpose of leveling loads and cutting power peaks. Do. Alternatively, the gate of the PCS 2 is stopped in a state in which the DC energy is charged in preparation for the sag compensation operation, and the apparatus stands by. When an abnormality occurs in the power system, as shown in FIG. 4, the high-speed switch 1 is shut off, the load 7 is disconnected from the power system, and the PCS is shifted to the self-sustained operation, whereby stable power is supplied to the load 7 within a predetermined time. Supply.

  FIG. 5 is a control block diagram of the parallel type sag compensator. The system abnormality detecting unit 10 detects the voltage Vs of the power system. A signal is output, and a connection command to the interconnection operation control unit 12 is output to the switching unit 11. The interconnection operation control unit 12 includes a current command value calculation unit 13 and an ACR control unit 14.

  The current command value calculation unit 13 generates a current command value by adding the value obtained by multiplying the effective component of the charge / discharge current command value by the SIN wave and the value obtained by multiplying the invalid component of the charge / discharge current command value by the COS wave. . The ACR control unit 14 controls the generated current command value so that the detected current Iinv of the PCS 2 matches. The control signal from the ACR control unit 14 is added to the SIN wave and input to the PWM signal generation unit 15 to generate a gate signal of the AC / DC converter 4.

When an abnormality occurs in the power system and the detection voltage Vs falls below a predetermined value, the system abnormality detection unit 10 outputs an abnormality occurrence signal to the gate signal generation unit of the high-speed switch 1 to turn off the high-speed switch 1. At the same time, a switching signal is output to the switching means 11 to switch to the independent operation control unit 16 side, and the independent operation control unit 16 and the PWM signal generation unit 15 are connected. As a result, the voltage control signal calculated by the AVR control unit 17 so that the voltage command value matches the detection voltage Vout of the PCS2 is input to the PWM signal generation unit 15 via the switching unit 11, and the PCS2 operates independently. . The PCS 2 that has been operated independently supplies stable power to the load 7 at a predetermined voltage at a predetermined voltage.
The system abnormality detection unit 10 determines that a power failure has occurred when the voltage falls below a preset voltage.

  Patent Documents 1 to 3 and the like are known as a method for detecting a power outage in a power system.

JP 2006-242739 JP-A-2002-369370 Japanese Patent Publication No. 61-29219

  The system abnormality detection unit 10 shown in FIG. 5 determines that a power failure has occurred when the voltage falls below a preset voltage. When a synchronous motor is connected as the load 7, a counter electromotive force is generated as a characteristic of the synchronous motor even when the AC power supply is opened. In particular, when the moment of inertia of the synchronous motor is large, the kinetic energy of the rotating body increases, and the AC voltage decreases slowly. Therefore, even if an abnormality occurs in the power system in which the synchronous motor is connected to the load 7 of the parallel sag compensator and the upper circuit breaker is opened and a power failure occurs, the power is detected by the parallel sag compensator. Since the AC voltage drops slowly, the power failure detection is delayed.

  By increasing the time from the occurrence of the power failure to the transition to the instantaneous sag compensation operation, the frequency of the back electromotive force of the synchronous motor decreases. If the parallel voltage sag compensator operates in the lowered state, there is a possibility that a difference occurs between the output voltage waveform of the device and the back electromotive force waveform, and the synchronous motor may lose synchronism.

  An object of the present invention is to provide a power conversion device that can quickly detect an abnormality in a system even when a back electromotive force is generated by connecting a synchronous motor to a parallel type voltage sag compensator.

According to the present invention, a load is connected to a power system via a high-speed switch, an abnormality of the power system is detected by a system abnormality detection unit, the high-speed switch is turned off by the detected abnormality signal, and the load is connected to the load via the power storage device and the PCS. In a power converter configured to supply power,
A power calculation unit configured to input a detected voltage and a detected load current of the power system to calculate an active power P;
The calculated active power P is input through a low-pass filter, the active power P is compared with a preset power set value Pref, and when Pref> P, it is determined that the power system is abnormal and the high-speed switch is determined. A comparison determination unit that outputs a cutoff signal SW-off,
It is provided with.

Further, according to the present invention, a synchronous motor is connected as a load, and the power calculator calculates the active power P by the following equation.
P = ((receiving voltage RS phase × load current R phase) − (receiving voltage ST phase × load current T phase))
× 2 / √3
Where R, S and T are the phases of the three-phase power system,

  As described above, according to the present invention, a synchronous motor is connected as a load of a power system, and even if a back electromotive force is generated by the synchronous motor, a power failure can be detected instantaneously, and stable power supply to the load can be achieved. It becomes possible. In addition, since instantaneous sag compensation can be performed instantaneously, there is no possibility that the synchronous motor will lose synchronism.

FIG. 1 is a configuration diagram illustrating an embodiment of the present invention. FIG. 2 is a configuration diagram of a parallel type sag compensator. FIG. 4 is an explanatory diagram of the operation of the parallel type sag compensator when the power system is normal. FIG. 5 is an explanatory diagram of the operation of the parallel type sag compensator when the power system is abnormal. FIG. 3 is a control block diagram of a parallel type sag compensator.

FIG. 1 shows a configuration diagram of a system abnormality detection unit 20 according to the present invention, and other devices such as a PCS are the same as those in FIG. A synchronous motor SM is connected as a load 7 to a power system 6 having three phases of R, S, and T via a high-order circuit breaker and a high-speed switch 1. Reference numeral 21 denotes a power calculation unit which inputs the system voltage Vs (or the output voltage Vout of the PCS) and the detected value of the load current Iload, and calculates the active power P at predetermined intervals based on the following equation.
P = ((receiving voltage RS phase × load current R phase) − (receiving voltage ST phase × load current T phase))
× 2 / √3
Where R, S and T are the phases of the three-phase power system,
The calculated active power P is subjected to LPF processing by the low-pass filter 22 and then output to the comparison determination unit 23. The comparison / determination unit 23 compares the input active power P with a preset power set value Pref, and when Pref> P, determines that there is a system abnormality and sends a cutoff signal SW-off to the high-speed switch 1. And the switching means 11 shown in FIG. 5 is switched from the interconnected operation control unit 12 to the operation by the independent operation control unit 16 (from current control to voltage control), so that stable power is supplied to the load 7. Becomes possible.

  Even if the circuit breaker installed on the upper side of the high-speed switch 1 is opened, the system voltage decreases slowly due to the back electromotive force of the synchronous motor as the load. For this reason, a power failure cannot be detected by the instantaneous sag detection by the ordinary parallel type sag compensator, but as in the present invention, a change in active power P based on different phase voltages and phase currents (Pref> P) In the power failure determination according to the above, the load current does not flow because there is no path through which the load current flows, and the power failure can be detected.

  As described above, according to the present invention, a synchronous motor is connected as a load of a system, and even if a back electromotive force is generated by the synchronous motor, a power failure can be detected instantaneously, and stable power supply to the load becomes possible. . In addition, since instantaneous sag compensation can be performed instantaneously, there is no possibility that the synchronous motor will lose synchronism.

1. Grid connection switch (high-speed switch)
2. PCS
DESCRIPTION OF SYMBOLS 3 ... LC filter 4 ... AC / DC converter 5 ... Power storage device 6 ... Power system 7 ... Load 20 ... System abnormality detection part 21 ... Power calculation part 22 ... Low pass filter 23 ... Comparison judgment part

Claims (2)

A load is connected to the power system via a high-speed switch, an abnormality in the power system is detected by a system abnormality detection unit, the high-speed switch is turned off by the detected abnormality signal, and power is supplied to the load via the power storage device and the PCS. In the power converter configured as described above,
A power calculation unit configured to input a detected voltage and a detected load current of the power system to calculate an active power P;
The calculated active power P is input through a low-pass filter, the active power P is compared with a preset power set value Pref, and when Pref> P, it is determined that the power system is abnormal and the high-speed switch is determined. A comparison determination unit that outputs a cutoff signal SW-off,
Equipped with a,
The power converter, wherein the power set value Pref is set by previously calculating an active power P calculated by the power calculator when an abnormality occurs in a power system. The power converter according to claim 1, wherein a synchronous motor is connected as the load, and the power calculation unit calculates the active power P by the following equation.
P = ((receiving voltage RS phase × load current R phase) − (receiving voltage ST phase × load current T phase))
× 2 / √3
Where R, S and T are the phases of the three-phase power system.

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