CN105226683B - The compensation method of micro-capacitance sensor three unbalanced power compensator inverter device - Google Patents

Abstract

The invention relates to a compensation method for a three-phase unbalanced power inverter compensation device for a micro-grid. The device includes a new energy power generation device, a power conversion circuit, a filter circuit, an interphase relay, a grid-connected relay and a controller. The controller controls the power conversion The opening and closing of the eight IBGTs in the circuit inverts the direct current generated by the new energy power generation device into alternating current, which is connected to the power grid through the filter circuit and the grid-connected relay. The compensation method is: the controller collects the effective value, frequency and phase of the three-phase grid voltage in real time, finds out the phase with the lowest grid voltage, and calculates the voltage difference between other phases and this phase, and adjusts the three-phase grid-connected power accordingly. When the grid-connected current of the lowest phase of the grid voltage reaches the rated value of the power conversion circuit, and the voltage of this phase is still low, disconnect the grid-connected relays of other phases, set the output current of other phases to the same phase, and turn on other phases. With the interphase relay of this phase, two phases or three phases are merged into this phase to jointly compensate the power and voltage of this phase.

Description

Compensation method for three-phase unbalanced power inverter compensation device in microgrid

technical field

The invention belongs to a compensation method for a micro-grid power inverter compensation device, in particular to a new energy generation micro-grid three-phase unbalanced power inverter with three-phase grid-connected inverter, inter-phase unbalanced power and voltage compensation, and power factor compensation. The compensation method of the compensation device.

Background technique

Energy issues have always been an important factor restricting the development of a human society. Every major progress in society is inseparable from the improvement and replacement of energy. In June 2012, the famous American economist Jeremy Rifkin proposed that the world is about to enter the "post-carbon" era, and the third industrial revolution characterized by the combination of Internet technology and renewable energy will be the The hope for sustainable development and avoiding catastrophic climate change. my country is strategically adjusting the current energy structure, vigorously researching and developing clean and renewable energy technologies, including the development and application of wind energy, solar energy, hydrogen energy and other energy sources. Under the vigorous guidance of national policies, the development and utilization of wind energy and solar energy have developed rapidly. In February 2013, the State Grid Corporation of China issued the "Opinions on Doing a Good Job of Distributed Power Grid-connected Services", which clearly pointed out that household users can not only use wind energy, solar energy and other new energy power generation devices to provide power for themselves, but also use inexhaustible Electricity is sold to the grid.

The rapid development of new energy power generation technology has promoted the rapid development of distributed power generation technology. The establishment of distributed power generation system has promoted the construction of new power grids and improved the stability and reliability of traditional power grids. The three-phase grid-connected inverter is the core component of the distributed generation system, and its research is of great significance.

The AC three-phase voltage and power output by traditional inverters are balanced, but in distributed power generation systems such as sea islands, many power loads are single-phase, and are distributed unbalanced in the three phases A, B, and C, making The unbalanced three-phase power of the microgrid will lead to unbalanced three-phase voltage and low voltage of a certain phase, which will reduce the quality of power supply and even affect the normal power supply. In order to solve this problem, it is necessary to distribute A, B, and C three-phase power for the electricity generated by the power generation system according to the three-phase voltage value of the power grid, and perform power compensation for the low-voltage phase to achieve three-phase voltage balance.

Therefore, it is necessary to provide a compensation method with a simple structure, strong realizability, and a three-phase unbalanced power compensation device for a microgrid.

Contents of the invention

The purpose of the present invention is to provide a compensation method for a micro-grid three-phase unbalanced power compensation device with a simple structure, which can realize grid-connected inverter, power compensation and power factor compensation.

In order to achieve the above object, the technical solution adopted in the present invention is:

A compensation method for a micro-grid three-phase unbalanced power inverter compensation device, the compensation device includes a new energy power generation device, a power conversion circuit, a filter circuit, an interphase relay, a grid-connected relay, and a controller, and the controller controls the The eight IBGTs in the power conversion circuit are turned on and off to invert the direct current generated by the new energy power generation device into alternating current, which is merged into the power grid through the filter circuit and the grid-connected relay. The compensation method of the compensation device is: the controller Collect the effective value, frequency and phase of the three-phase grid voltage in real time, find out the phase with the lowest grid voltage, and calculate the voltage difference between other phases and this phase, adjust the three-phase grid-connected power according to the voltage difference, so that the grid-connected phase with the lowest grid voltage Maximum power to compensate grid voltage and power imbalance. When the grid-connected current of the lowest phase of the grid voltage reaches the rated value of the power conversion circuit, and the voltage of this phase is still low, disconnect the grid-connected relays of other phases, set the output current of other phases to the same phase, and turn on other phases. With the phase-to-phase relay of this phase, two phases or three phases are merged into this phase to jointly compensate the power and voltage of this phase; the current of each phase can also compensate the power factor of the grid according to the setting of a certain angle ahead or behind the voltage.

Compared with the prior art, the micro-grid three-phase unbalanced power inverter compensation device and compensation method of the present invention have simple structure and strong power and voltage unbalanced compensation ability. It can not only achieve inverter, but also realize grid connection, and even three-phase output can be connected to the phase with the lowest voltage to jointly compensate the power and voltage of the phase.

The present invention will become clearer through the following description in conjunction with the accompanying drawings, which are used to explain the embodiments of the present invention.

Description of drawings

Fig. 1 is a functional block diagram of a micro-grid three-phase unbalanced power inverter compensation device of the present invention.

Fig. 2 is a control flow chart of the microgrid three-phase unbalanced power inverter compensation method of the present invention.

detailed description

Embodiments of the present invention will now be described with reference to the drawings, in which like reference numerals represent like elements.

In one embodiment of the present invention, the inverter power of the phase with high voltage is reduced, and the power of the phase with low voltage is increased, so as to realize the power compensation of the phase with low voltage. The specific feature is that the controller distributes the three-phase grid-connected power evenly according to the output power of the new energy power generation device in the initial state; For the phase with the lowest grid voltage, calculate the voltage difference between other phases and the lowest phase. If the voltage difference is greater than the set threshold, subtract a constant from the output current of the phase with the highest voltage, and increase the current of the lowest phase with an equivalent constant. Until the grid-connected current of the phase with high voltage is zero, or the grid-connected current of the phase with low voltage reaches the rated value.

In another embodiment of the present invention, the inverter output of the phase with high voltage is transformed into the same phase as the phase with low voltage, and the phase with low voltage is merged to jointly supply power for the phase with low voltage. The specific feature is that the grid-connected current of the phase with high voltage is zero, or the grid-connected current of the phase with low voltage reaches the rated value, and the voltage difference between the phase with low voltage and the phase with high voltage is still greater than the set threshold, then the corresponding phase with high voltage is turned off. The grid-connected relay, set the inverter current of this phase and the current of the low-voltage phase to be in the same phase, open the phase-to-phase relay of this phase and the low-voltage phase, two or three phases are merged into the low-voltage phase, and jointly compensate the low-voltage phase power and voltage.

As shown in FIG. 1 , the present invention includes a new energy power generation device 300 , a power conversion circuit 200 , a filter circuit 400 , an interphase relay 500 , a grid-connected relay 600 and a controller 100 .

The controller 100 controls the on and off of the eight IBGTs in the power conversion circuit 200 to invert the DC power generated by the new energy power generation device 300 into AC power, which is connected to the power grid through the filter circuit 400 and the grid-connected relay 600 . The controller 100 collects the effective value, frequency and phase of the three-phase grid voltage in real time, finds out the phase with the lowest grid voltage, calculates the voltage difference between other phases and this phase, and adjusts the three-phase grid-connected power according to the voltage difference so that the phase with the lowest grid voltage The grid-connected power is the largest to compensate for grid voltage and power imbalance. When the grid-connected current of the lowest phase of the grid voltage reaches the rated value of the power conversion circuit, and the voltage of this phase is still low, disconnect the grid-connected relays of other phases, set the output current of other phases to the same phase, and turn on other phases. With the interphase relay of this phase, two phases or three phases are merged into this phase to jointly compensate the power and voltage of this phase. The current of each phase can also compensate the power factor of the power grid according to a certain angle of setting the leading or following voltage.

In the initial state, the controller 100 distributes the three-phase grid-connected power on average according to the output power of the new energy generating device 300; For the lowest phase, calculate the voltage difference between other phases and the lowest phase. If the voltage difference is greater than the set threshold, subtract a constant from the output current of the phase with the highest voltage, and increase the current of the lowest phase with an equivalent constant until the voltage The grid-connected current of the high phase is zero, or the grid-connected current of the phase with low voltage reaches the rated value.

The grid-connected current of the phase with high voltage is zero, or the grid-connected current of the phase with low voltage reaches the rated value, and the voltage difference between the phase with low voltage and the phase with high voltage is still greater than the set threshold, then close the corresponding grid-connected relay with high voltage , set the inverter current of this phase and the current of the low voltage phase to be in the same phase, open the interphase relay between this phase and the low voltage phase, two or three phases are merged into the low voltage phase, and jointly compensate the power and voltage of the low voltage phase. If it is detected that the phase C voltage of the power grid is the lowest and the phase A voltage is the highest, the power adjustment strategy is shown in Figure 2. The working process of this example is as follows:

The controller 100 first distributes the three-phase grid-connected power on average, finds out that the phase with the lowest voltage is phase C, and calculates the voltage difference between other phases and phase C:

ΔU _a ＝U _a -U _c (1)

ΔU _b ＝U _b -U _c (2)

Among them, U _a , U _b , and U _c are the voltage effective values of the three phases A, B, and C of the grid, respectively.

Because the highest voltage phase is A, first judge whether ΔU _a exceeds the allowable range, if not, no power compensation is required; if it exceeds, then gradually reduce the A-phase inverter output current, and the reduced part Add to phase C. When the inverter output current of phase A drops to close to 0, or the output current of phase C reaches the rated value and cannot be increased any more, and the voltage difference between phase A and phase C still exceeds the allowable value, set the inverter output current of phase A is 0, disconnect the A-phase grid-connected relay 610, turn on the A-phase and C-phase interphase relay 530, then set the A-phase current and C-phase current to be in the same phase, and gradually increase the A-phase current so that the A-phase and C-phase The inverter outputs are connected in parallel to supply power for phase C of the grid. If the voltage difference between phase B and phase C also exceeds the allowable value at this time, turn off the grid-connected relay 620 of phase B, turn on the phase-to-phase relay 520 between phase B and phase C, and then set the current of phase B and phase C to be in the same phase, and Gradually increase the B-phase current, so that the A-phase, B-phase, and C-phase inverter outputs are connected in parallel, and jointly supply power to the C-phase of the grid to realize compensation for the power and voltage of the C-phase of the grid. At this time, the three-phase current output by the inverter is:

Among them, i _a , i _b , _ic are the instantaneous values of the inverter output A, B, and C three-phase currents respectively, I _a , I _b , and I _c are the effective values of the inverter output A, B, and C three-phase currents respectively, is the phase angle of phase C.

The controller is characterized in that it can set the grid-connected current of each phase inverter to lead or lag the grid voltage by a certain angle, so as to realize the compensation of the power factor of the grid:

in, are the three-phase voltage phase angles of power grids A, B, and C, respectively, and θ is the expected leading or lagging angle.

The micro-grid three-phase unbalanced power inverter compensation device and method of the present invention has simple structure and strong power and voltage unbalanced compensation ability. It can not only achieve inverter, but also realize grid connection, and even three-phase output can be connected to the phase with the lowest voltage to jointly compensate the power and voltage of the phase.

The present invention has been described above in conjunction with the best embodiments, but the present invention is not limited to the above disclosed embodiments, but should cover various modifications and equivalent combinations made according to the essence of the present invention.

Claims (3)

1. A compensation method of a microgrid three-phase unbalanced power inversion compensation device comprises a new energy power generation device, a power conversion circuit, a filter circuit, an interphase relay, a grid-connected relay and a controller, wherein the controller inverts direct current generated by the new energy power generation device into alternating current by controlling the on and off of eight IGBTs in the power conversion circuit, and the alternating current is merged into a power grid through the filter circuit and the grid-connected relay; when the grid-connected current of the lowest phase of the grid voltage reaches the rated value of the power conversion circuit and the phase voltage is lower, the grid-connected relays of other phases are disconnected, the output current of other phases is set to be the same as the phase, the phase-to-phase relays of other phases and the phase are switched on, two phases or three phases of the compensation device are merged into the phase of the grid, and the phase power and the voltage are compensated together.

2. The compensation method for the micro-grid three-phase unbalance power inversion compensation device according to claim 1, wherein the controller distributes three-phase grid-connected power evenly according to the output power of the new energy power generation device in an initial state; and then, acquiring the effective value, the frequency and the phase of the voltage of the three-phase power grid in real time in each control period, finding out the phase with the lowest voltage of the power grid, calculating the voltage difference between other phases and the lowest phase, subtracting a constant from the output current of the phase with high voltage if the voltage difference is greater than a set threshold value, and increasing the current of the phase with the lowest voltage by an equivalent constant until the grid-connected current of the phase with high voltage is zero or the grid-connected current of the phase with low voltage reaches a rated value.

3. The compensation method of the microgrid three-phase unbalanced power inversion compensation device as claimed in claim 2, characterized in that the phase grid-connected current with high voltage is zero, or the phase grid-connected current with low voltage reaches a rated value, and the phase difference between the phase with low voltage and the phase with high voltage is still greater than a set threshold, then the corresponding grid-connected relay with high voltage is closed, the inversion current of the phase is set to be in the same phase with the current of the low voltage phase, the phase-to-phase relay with the phase with low voltage phase is opened, and the two phases or the three phases of the compensation device are merged into the low voltage phase to compensate the power and the.