JP2019205239A - Power conversion system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally generate power when operating with a reduced power factor. SOLUTION: A power converter connected to an AC power system, a power factor control means for controlling a power factor of the power converter, and an active power control means for controlling active power output by the power converter. In the power conversion system having, the active power controlled by the active power control means is equal to or more than the power obtained by multiplying the active power outputable at the power factor 1 by the power factor controlled by the power factor control means. Provided is a power conversion system having an active power adjusting function of increasing or decreasing. [Selection diagram] Figure 2

Description

  The present invention relates to a power conversion system.

  In recent years, the installation of photovoltaic power generation has increased nationwide, and the problem of voltage rise has become serious in distributed small power generation systems. For this reason, measures have been taken to mitigate this by injecting phase reactive power from the distributed small power generation system to the system (Patent Document 1).

JP 2014-166009

  As in Patent Document 1, injecting phase advance reactive power deteriorates the power factor, and the current effective value level necessary to output the same active power increases. As the current increases, it is necessary to improve the component ratings of the distributed compact power generation system and to take measures to suppress the rise in internal temperature. For this reason, it is necessary to reduce the active power output by the distributed compact power generation system by the amount of the dropped power factor. However, this measure has a risk that the distributed compact power generation system cannot sufficiently output the effective power that can be generated.

  An object of the present invention is to provide a system that maintains as much as possible the effective power that can be generated by a distributed compact power generation system when generating power by reducing the power factor of the power generation system.

  The present invention has been made to solve the above-described problems, and includes a power converter connected to an AC power system, power factor control means for controlling the power factor of the power converter, and the power converter. An active power control means for controlling the effective power output by the power conversion system, wherein the effective power that can be output at a power factor of 1 multiplied by the power multiplied by the power factor controlled by the power factor control means As described above, the present invention is characterized by having an active power adjustment function for increasing or decreasing the active power controlled by the active power control means.

  ADVANTAGE OF THE INVENTION According to this invention, even when it is at the time of generating electric power by reducing the power factor of a power generation system, the distributed small power generation system can maintain active power which can be generated originally as much as possible.

Schematic which shows the system configuration regarding this invention. Schematic which shows the active power adjustment function and active power control function before this invention application. Schematic showing active power adjustment function and active power control function to which the present invention is applied

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  An embodiment of the present invention will be described with reference to FIGS. First, FIG. 1 shows a system configuration diagram in an embodiment of the present invention.

  This system includes a solar cell 1, a power converter 2 that converts DC power generated in the solar cell 1 into AC power, and a commercial system 3 that is an AC power system.

  The power converter 2 includes a power conversion circuit 20 that converts DC power generated in the solar cell 1 into AC power and outputs the AC power, a control unit 21 that controls the power conversion circuit 20, and a voltage Vout of the commercial system 3. Voltage detection means 22 for detecting the current, and current detection means 23 for detecting the current Iout output from the power conversion circuit 20 to the commercial system 3. The control means 21 has a power calculation function 210 for calculating the power factor λ from the information of the voltage detection means 22 and the current detection means 23, and the active power Pout output from the power converter 2 to the commercial system 3 is the power factor target value λref. Active power control function 211 for determining the current command value Iref so as to substantially match the effective power target value Pref, and control the phase difference θ between the voltage Vout and the current Iout so that the power factor λ substantially matches the power factor target value λref. Power factor control function 212 for controlling current Iout to have a phase difference θ with respect to Vout so that it substantially matches the current command value Iref, effective according to voltage Vout and power factor target value λref An active power adjustment function 214 that increases or decreases the power Pref, and a maximum generated power calculation means 215 that calculates the maximum power Pm that can be generated.

  Here, when the voltage Vout is 202 Vrms, the maximum active power Pout that can be output from the power converter 2 when the power factor λ is 1 is the maximum power Pmax, and the current Iout is the maximum current Imax. Normally, Pout should not drive Pmax and Iout should not exceed Imax.

  In this embodiment, a solar cell is used as an input power source. However, the input power source may be gas cogeneration, a wind power generator, a fuel cell, a storage battery, or the like. . Alternatively, an AC electric power converter may be used such as an AC / AC inverter.

  The maximum generated power calculation means 215 calculates the maximum power that can be generated that varies with time series, such as MPPT (Maximum Power Point Tracking) if the power input source is a solar cell. However, when a storage battery, wind power generation or the like is an input source, the calculation may be performed by another method.

  FIG. 2 shows an active power adjustment function 214 ′ and an active power control function 211 before application of the present invention. In S2141, the first active power limit value Plim1 is calculated by multiplying λref by Pmax. In S2142, the smaller of the output power and Plim1 is selected and set to Pref. In S2111, the apparent power command value Sref is calculated by dividing Pref and λref. In step S2112, Iref is calculated by dividing Sref by Vout.

  The active power adjustment function 214 ′ determines Pref from the power factor target value λref, the maximum power Pmax, and the output power Pm obtained by the maximum generated power calculation means 215, and the active power control function 211 abbreviates Pout as Pref. Iref, which is a current command value necessary for matching, is calculated as Iref = Pref ÷ λref ÷ Vout.

  Here, assuming that Pref = Pmax and Vout = 202V so that the active power adjustment function 214 ′ outputs the maximum possible power without considering the power factor, the active power control function can be achieved by lowering the power factor. The current command value calculated by 211 is Iref = Pmax ÷ λref ÷ 202> Imax, and Iref exceeds Imax. Specifically, considering Pmax = 5500W, λ = 0.85, Vout = 202V, Imax = 5500 ÷ 202 = 27.2A, Iref = 5500 ÷ 0.85 ÷ 202 = 32.3A, which exceeds the maximum current of 27.2A. End up.

  Therefore, the active power adjustment function 214 'has a function of limiting the Pref by calculating the active power limit value Plim1 so that Iref does not exceed Imax. By S2141, Plim1 = Pmax × λref is provided as a limit of the active power target value Pref, and Pref ≦ Plim1. As a result, Pout ≦ Pmax × λref, and Iout ≦ Imax can be maintained. Specifically, considering the case of maximum power generation with Pmax = 5500W, λref = 0.85, Plim1 = 5500 × 0.85 = 4675, Iout = 4675 ÷ 0.85 ÷ 202 = 27.2. 27.2A.

  However, this means that, when it is desired to reduce the power factor target value λref to 0.85, power can be generated only up to 85% of Pmax.

  Next, operations of the active power adjustment function 214 and the active power control function 211 to which the present invention is applied will be described with reference to FIG.

  In the present invention, the active power adjustment function 214 adjusts Pref more appropriately by using the voltage Vout. For realization, S2143 and S2144 are added to the active power adjustment function 214 '. In S2143, Vout is divided by 202V, and this value is multiplied by Plim1 output in S2141 in S2144, and this is used as an input to S2142. Plim1 is a value based on the premise that Iref does not exceed Imax when voltage Vout is 202Vrms. However, when voltage Vout becomes high, Iref <Imax when Pref = Pmax, so Pref is increased accordingly. Is possible.

  As a result, when the voltage is higher than 202 Vrms, it is possible to obtain the maximum active power command value Pref ≦ Pmax that satisfies Iref ≦ Imax.

  As an example, first consider the case of Vout = 202V, Pmax = 5500W, λref = 0.85, Plim2 = 5500 × 0.85 ÷ 202 × 202 = 4675, Iref = 4675 ÷ 0.85 ÷ 202 = 27.2, and the maximum current is 27.2A. On the other hand, the output current is 27.2A.

  On the other hand, when Vout = 220V, Pmax = 5500W, λref = 0.85, Plim2 = 5500 × 0.85 ÷ 202 × 220 = 5092, Iref = 5092 ÷ 0.85 ÷ 220 = 27.2, and the output current against the maximum current of 27.2A Becomes 27.2A. At this time, power generation is possible up to Plim2 = 5092W, which corresponds to 93% of the maximum power generation amount Pmax.

  As described above, when the voltage rises, it is possible to generate larger active power and to prevent the current command value Iref from exceeding the maximum current Imax.

DESCRIPTION OF SYMBOLS 1 Solar cell 2 Power converter 3 Commercial system 20 Power conversion circuit 21 Control means 22 Voltage detection means 23 Current detection means 210 Power calculation function 211 Effective power control function 212 Power factor control function 213 Current control function 214 Effective power adjustment function 214 ' Active power adjustment function 215 before application of the present invention Maximum generated power calculation means

Claims (2)

A power converter connected to the AC power system;
Power factor control means for controlling the power factor of the power converter;
Active power control means for controlling the active power output by the power converter;
A power conversion system comprising:
It has an active power adjustment function to increase or decrease the active power controlled by the active power control means so that the effective power that can be output at a power factor of 1 is equal to or higher than the power multiplied by the power factor controlled by the power factor control means. Power conversion system characterized by   The active power adjustment function increases the effective power output from the power converter while increasing the voltage detected by the voltage detecting means, and decreases the voltage detected by the voltage detecting means while reducing the voltage detected by the voltage detecting means. 2. The power conversion system according to claim 1, wherein the effective power output from the power source is reduced.

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