JP2008219989A - Power interchange device - Google Patents

Abstract

[PROBLEMS] The conventional technique uses a half-cycle moving average for calculating the average active power, so that a calculation delay of half cycle (180 ° in fundamental wave phase) occurs, and the fluctuation of active power is large. There is a problem that an error occurs in the power accommodation amount due to a calculation delay.
In a power interchange device that performs power interchange between single-phase alternating currents, the instantaneous power is calculated by multiplying the instantaneous load voltage and the instantaneous load current of each phase, and the fundamental phase is 30 degrees before the instantaneous power. The average active power is calculated by subtracting the instantaneous power, and adding the instantaneous power of 60 ° before the fundamental wave phase, and power interchange is performed from the difference of the active power of each phase.
[Selection] Figure 3

Description

  The present invention relates to a control method for a power accommodation apparatus that performs power accommodation between single-phase alternating currents using an inverter.

In order to perform power interchange between single-phase alternating currents, it is necessary to calculate each single-phase power to be interchanged. here,
Instantaneous voltage: e = Esin (wt) (1)
Instantaneous current: i = Isin (wt + θ) (2)
Then, the instantaneous power p is as follows.
Instantaneous power p = e * i = Esin (wt) * Isin (wt + θ) = P / 2 * (cosθ-cos (2wt + θ)) ... (3)
(However, P = E * I, w is angular frequency, θ is phase angle)
From equation (3), the single-phase instantaneous power is a DC component (cosθ component) and a sinusoidal ripple component (cos (2wt + θ) component) that is twice the fundamental frequency. Therefore, in order to obtain the average active power, it is necessary to remove the double frequency sine wave ripple.
FIG. 5 shows a conventional embodiment of a method of removing a double frequency sine wave ripple. As a conventional example, there is Patent Document 1 “Three-phase electric quantity normal / reverse phase detection circuit”. In the prior art, the negative phase component included in the outputs IdP and IqP of the positive phase vector converter is removed (the output of the positive phase vector converter is DC for the positive phase and the double frequency of the fundamental wave for the negative phase component). Sine wave ripple) and removal of the positive phase included in the outputs IdN and IqN of the negative phase vector converter (the negative phase converter output is DC for the negative phase and the fundamental wave for the positive phase) Half-cycle moving average (moving average of double frequency of fundamental wave) is used for sine wave ripple of double frequency). That is, by calculating the moving average over the 180 ° period of the fundamental wave, the harmonic component having a frequency 2 m (m is an integer) times can be completely removed.
JP-A-6-245383

  As described above, the conventional technique uses a half-cycle moving average for calculating the average active power, so that a calculation delay of a half cycle (180 ° in the fundamental wave phase) occurs and the fluctuation of the active power is large. However, there is a problem that an error occurs in the power accommodation amount due to a calculation delay.

  In order to solve the above-described problem, in the first invention, in the power accommodation device that performs power accommodation between single-phase alternating current, the instantaneous power is calculated by multiplying the instantaneous load voltage and the instantaneous load current of each phase, The average active power is calculated by subtracting the instantaneous power of 30 ° before the fundamental phase from the instantaneous power, and adding the instantaneous power of 60 ° before the fundamental phase, and from the difference of the active power of each phase Perform power interchange.

  In the present invention, in a power accommodation device that performs power accommodation between single-phase alternating currents, the instantaneous power is calculated by multiplying the instantaneous load voltage and the instantaneous load current of each phase, and the fundamental phase is 30 ° before the instantaneous power. Since the average active power is calculated by subtracting the instantaneous power and then adding the instantaneous power of 60 ° before the fundamental phase, and power is interchanged from the difference of the active power of each phase, there is little Single-phase active power can be computed with computation delay. As a result, even when applied to a device in which the effective power of the load changes suddenly, such as a power interchange device for railways, a power interchange error due to a calculation delay can be reduced, and the performance of the device can be improved.

  The main point of the present invention is that, in a power interchange apparatus that performs power interchange between single-phase alternating currents, as an average active power calculation method, an instantaneous power is calculated by multiplying an instantaneous load voltage and an instantaneous load current of each phase, and the instantaneous power is calculated. The point is that the instantaneous power 30 degrees before the fundamental wave phase is subtracted from the power, and further the instantaneous power 60 degrees before the fundamental wave phase is added.

FIG. 1 is a diagram illustrating the relationship between instantaneous voltage, instantaneous current, and instantaneous power. As shown in the equation (3), the instantaneous power is a sine wave ripple of the DC component and twice the fundamental frequency.
FIG. 2 is a diagram for explaining the first invention. Substituting wt-30 in the equation (3) for wt-30 °, which corresponds to the instantaneous power 30 ° before the fundamental phase, and wt-60 °, which corresponds to the instantaneous power 60 ° before the fundamental phase, respectively. The instantaneous voltage p (-30) before 30 ° is given by equation (4), and the instantaneous voltage p (-60) before 60 ° is given by equation (5).
p (-30) = P / 2 * (cosθ-cos (2 (wt-30 °) + θ)) = P / 2 * (cosθ-cos (2wt + θ-60 °))
= P / 2 * (cosθ + cos (2wt + θ-240 °)) ... (4)
p (-60) = P / 2 * (cosθ-cos (2 (wt-60 °) + θ)) = P / 2 * (cosθ-cos (2wt + θ-120 °)) ... (5)
Therefore, subtracting (4) from (3) and adding (5),
p- p (-30) + p (-60) = P / 2 * (cosθ-cos (2wt + θ))-P / 2 * (cosθ + cos (2wt + θ-240 °))
+ P / 2 * (cosθ-cos (2wt + θ-120 °))
= P / 2 * cosθ-P / 2 * (cos (2wt + θ) + cos (2wt + θ-120 °) + cos (2wt + θ-240 °))
= P / 2 * cosθ ・ ・ ・ (6)
It becomes like (6) types. That is, a sinusoidal ripple having a frequency twice that of the fundamental wave can be removed, and an average active power is obtained. In the present invention, the calculation delay of the active power uses a current value and values of 30 ° before and 60 ° before the fundamental wave phase, so that a delay equivalent to about 30 ° is sufficient.

FIG. 3 is a circuit diagram showing an embodiment when the present invention is applied to a power interchange device for electric railways. A three-phase AC power source 11 is converted into a voltage VM, vT of M- and T-seats, which are single-phase ACs that are 90 ° out of phase, with a feeding transformer 12, and a current detector 13 is connected to the M-seat line. The M seat load 17 and the voltage detector 15 are connected to the T seat line via the current detector 14, and the T seat load 18 and the voltage detector 16 are connected to the M seat line. An inverter (INVM) 21 having an AC input via a transformer (TrM) 19 is connected to the T seat line, and an inverter (INVT) 22 having an AC input via a transformer (TrT) 20 is connected to the T seat line as an inverter. 21 and the DC part of the inverter 22 are connected in common.
The power command PM * to the power interchange inverter 21 and the power command PT * to the inverter 22 are generated as follows.
The average active power PM of the M seat is input to the average active power calculator 25 by the instantaneous power pM obtained by multiplying the AC load current iM detected by the current detector 13 and the AC voltage vM of the M seat by the multiplier 23. Then, the calculator 25 subtracts the instantaneous power 30 ° before the fundamental wave phase, and further adds the instantaneous power 60 ° before the fundamental wave phase. The average active power PT in the T seat is obtained by multiplying the average power pT obtained by multiplying the AC load current iT detected by the current detector 14 and the AC voltage vT in the T seat by the multiplier 24 into the average active power calculator 26. Then, the calculator 26 subtracts the instantaneous power 30 ° before the fundamental wave phase and further adds the instantaneous power 60 ° before the fundamental wave phase.
Further, the difference between the average active power PM at the M position and the average active power PT at the T position is obtained by the adder 27, and half of this difference is obtained by the divider 28, and this is obtained as a power command PM to the inverter 21. * Further, the power command PT * to the inverter 22 is obtained by inverting the sign of the power command PM * to the inverter 21 by the sign inverter 29.
Here, a configuration example of the average active power calculators 25 and 26 is shown in FIG. This is an example of the T seat, but the same applies to the M seat. The average active power calculator (PA) 25 subtracts the instantaneous power pM (T) (-30 °) 30 ° before stored in the memory (MEM) 31 from the instantaneous power pM (T) and further stores the memory ( The instantaneous power pM (T) (-60 °) 60 ° before stored in the (MEM) 31 is added. The memory (MEM) 31 is composed of a ring buffer corresponding to a period of 60 °. For example, assuming that the number of ring buffers corresponding to a period of 60 ° is 60 (d1 to d60) and instantaneous power before 60 ° is stored in the 10th buffer (d10), the 10th buffer ( The instantaneous power pM (T) (-60 °) 60 ° before d10) is read out, and the instantaneous power pM 30 ° before the 40th buffer (d40) advanced by 30 ° phase from the 10th buffer (d10). (T) (-30 °) is read and addition / subtraction is performed. Then, after reading the instantaneous power pM (T) (−60 °) 60 ° before the tenth buffer, the current instantaneous power pM (T) is stored. Next, when calculating the average active power, the eleventh buffer becomes the instantaneous power pM (T) (-60 °) before 60 °, and the 41st buffer (d40) has the instantaneous power pM (T) (30 ° before). -30 °). In this way, by sequentially reading and storing the memory MEM,
Average active power PM (T) is calculated.
As described above, calculate the average active power PM of the M seat and the average active power PT of the T seat, and use half of the difference as the power commands PM * and PT * of the inverters INVM and INVT for power interchange. Thus, the M seat power PM ′ and the T seat power PT ′ of the feeder transformer (FT) 12 are expressed by the equations (7) and (8) and can be balanced.

M power: PM '= PM-PM * = PM-1 / 2 * (PM-PT) = 1/2 * (PM + PT) (7)
T-seat power: PT '= PT-PT * = PT + 1/2 * (PM-PT) = 1/2 * (PM + PT) (8)

  The present invention can be applied to the elimination of power imbalance between feeding transformer outputs (M seat, T seat) of an AC feeding railway.

Diagram explaining instantaneous voltage, instantaneous current, and instantaneous power The figure for demonstrating the principle of this invention Circuit block diagram showing an embodiment of the present invention Configuration example of average active power calculator Example of conventional average active power calculation

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Three-phase AC power supply 12 ... Feeding transformer 13, 14 ... Current detector 15, 16 ... Voltage detector 17 ... M seat load 18 ... T seat load 19, 20 ... Transformers 21,22 ... Inverters 23,24 ... Multipliers 25,26 ... Average active power calculator 27 ... Adder 28 ... Divisor 29 ... Signal inverter 30 ... adder 31 ... memory

Claims (1)

In a power interchange device that performs power interchange between single-phase alternating currents,
Multiply the instantaneous load voltage and instantaneous load current of each phase to calculate the instantaneous power, subtract the instantaneous power 30 degrees before the fundamental phase from the instantaneous power, and then the instantaneous power 60 degrees before the fundamental phase A power interchange apparatus characterized in that the average active power is calculated by adding and the power interchange is performed from the difference between the active powers of the respective phases.

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