JP7078332B2 - Voltage control type virtual synchronous machine control device and voltage control type virtual synchronous machine - Google Patents

Description

Patent Law Article 30 Paragraph 2 Applicable General Incorporated Association Institute of Electrical Engineers of Japan Electricity and Energy Division, 2018 Institute of Electrical Engineers of Japan Electricity and Energy Division Conference Proceedings, pp. 170-page 171, August 31, 2018

The present invention relates to a voltage control type virtual synchronous machine control device and a voltage control type virtual synchronous machine.

In recent years, from the viewpoint of environmental problems, the introduction of distributed power sources using natural energy such as solar power generation systems has been progressing, and it is expected that the number will increase in the future. When renewable energy is systematized, it is often connected via transducers. Therefore, as the renewable energy increases, the number of synchronizers connected to the grid decreases, and the number of converters increases as an alternative.

FIG. 11 shows a block diagram of current control based on vector control, which is common as such a converter. The power control shown in the figure is a method in which a three-phase AC state quantity is converted into a two-phase conversion (αβ conversion) and further converted into a rotating coordinate system (DQ conversion). Since the D-axis (effective component) and the Q-axis (invalid component) are controlled separately and independently, both can be made non-interfering. Regarding power control, different controls are used depending on the application of the device, but the one shown in the figure shows a block of constant power control that outputs a constant power of the _pod .

FIG. 12 is a block diagram of a PLL (phase locked loop). In this way, the difference Δθ between the PLL phase θ _PLL and the phase θ _S between the system voltage (transformer transformer primary side voltage) is calculated, and control is performed so that this difference is set to 0.

The converter controlled in this way has a current control system, and can suppress overcurrent even when the system is disturbed.

However, when a large number of converters controlled in this way are connected to the system, problems such as an increase in system voltage fluctuation, a decrease in the amount of inertial energy in the system, a frequency change width during system disturbance, and an increase in speed occur. It can occur. Therefore, a virtual synchronous machine control has been proposed in which the converter is made to behave in the same manner as the conventional synchronous machine to stabilize the system (see, for example, Non-Patent Document 1).

As a converter provided with such virtual synchronous machine control (hereinafter, may be referred to as a virtual synchronous machine), there is one provided with voltage control type virtual synchronous machine control. FIG. 13 shows a schematic diagram in which a virtual synchronous machine equipped with this voltage-controlled virtual synchronous machine control is connected to the system. As shown in the figure, the virtual synchronous machine (VSG) 01 is controlled so as to simulate the behavior when the synchronous generator to be simulated is connected to the grid. The inductance 02 in FIG. 13 is obtained by substituting the reactor component of the generator to be simulated with the interconnection reactor of the converter.

Here, the behavior of the synchronous generator to be simulated is realized by solving the following equation.

Here, _Porder is the power command value, P _mes is the converter output power, J is the inertial moment of the simulated generator, ω _m is the rotor angle speed of the simulated generator, δ is the slip of the simulated generator, and D is the simulated power generation. Represents the braking coefficient of the machine.

FIG. 14 shows an example of control based on the solution of the above equation.

Since such a voltage-controlled virtual synchronizer operates as a voltage source by controlling the voltage, the current cannot be controlled. Therefore, when the system is disturbed, an overcurrent may occur and the converter may stop. For example, when a system failure occurs at the nearest end of the virtual synchronous machine 01 having an inductance 02 of 0.2 pu in FIG. 13, it is expected that an overcurrent of 5.0 pu or more will occur. The virtual synchronous machine 01, which is a converter in the concept itself, cannot withstand such a large current.

Kenichi Sakimoto et al., "Stabilization Control of Systems Inverter-Connected Distributed Power Sources by Virtual Synchronizer Generator", IEEJ Transactions on Electrical Engineers of Japan B, Vol. 132, No. 4 pp. 341-349 (2012)

In a converter equipped with conventional virtual synchronous machine control, when there is a risk of overcurrent occurring such as when the system is disturbed, it is necessary to stop the voltage control type virtual synchronous machine control and perform current control. Since the virtual synchronous machine control is stopped, the stability of the system is adversely affected.

In view of such circumstances, the present invention is a voltage control type virtual synchronizer capable of suppressing overcurrent while maintaining voltage control type virtual synchronizer control in a converter provided with voltage control type virtual synchronizer control. It is an object of the present invention to provide a control device and a voltage control type virtual synchronous machine.

The first aspect of the present invention that achieves the above object is a voltage control type virtual synchronous machine control device that controls a voltage control type virtual synchronous machine with respect to a converter, and controls that perform voltage control type virtual synchronous machine control. The control unit includes a compensating means for compensating for an output voltage command value input to the control unit, and the compensating means has a D of the output voltage command value and the measured system voltage value. Converted to a rotational coordinate system consisting of an axis and a Q axis, a control circle having a radius r centered on the system voltage value is used as a limiter, and the condition is that the output voltage command value goes out of the control circle. The voltage-controlled virtual synchronous machine control device is characterized in that the compensation output voltage command value existing on or inside the control circle is set as the output voltage command value.

The second aspect of the present invention is the voltage control type virtual synchronous machine control according to the first aspect, wherein the compensating output voltage command value is a point on the control circle and close to the system voltage. It is in the device.

A third aspect of the present invention is characterized in that the radius r is a value obtained from the reactor component value of the simulated generator simulated by the voltage control type virtual synchronous machine control. The voltage control type virtual synchronous machine control device according to the second aspect.

A fourth aspect of the present invention is that the compensating means measures the output voltage command value when the voltage difference V _diff between the vector vV _order of the output voltage command value and the vector _vV system of the system voltage value is larger than r. A compensating output voltage vector vV _conv-rev which is a voltage value V _conv between the V _order and the system voltage value V _sys and which is on or inside the control circle is determined, and this compensating output voltage vector vV _conv- The voltage control type virtual synchronous machine control device according to any one of the first to third aspects, wherein _rev is set to the compensating output voltage command value.

In a fifth aspect of the present invention, the compensating output voltage vector vV _conv-rev has a straight line connecting the vector vV _order of the output voltage command value _Vorder and the vector vV _sys of the system voltage value V _sys , and the control thereof. The voltage-controlled virtual synchronous machine control device according to the fourth aspect, characterized in that it is a vector to an intersection with a circle.

A sixth aspect of the present invention is that the compensation output voltage vector _{vV conv-rev} is the output of the vector _vV system of the system voltage value V system or the intersection of the straight line extending the vector and the control circle. The voltage control type virtual synchronous machine control device according to a fourth aspect is characterized in that it is a vector indicating a voltage value close to a voltage command value _Vorder .

A seventh aspect of the present invention is the voltage control type virtual synchronous machine, which is a converter provided with the voltage control type virtual synchronous machine control device according to any one of the first to sixth aspects. ..

According to the present invention, in a converter provided with voltage-controlled virtual synchronous machine control, a voltage-controlled virtual synchronous machine control device and voltage control capable of suppressing overcurrent while maintaining voltage-controlled virtual synchronous machine control and voltage control. A type virtual synchronous machine can be realized.

The block diagram of the voltage control type virtual synchronous machine control apparatus of the voltage control type virtual synchronous machine which concerns on Embodiment 1. FIG. An explanatory diagram conceptually showing the control of the compensation control unit according to the first embodiment. The control block diagram of the voltage control type virtual synchronous machine control apparatus which concerns on Embodiment 1. FIG. An explanatory diagram conceptually showing the control of the compensation control unit according to the second embodiment. Schematic diagram of the analysis target system used for the simulation of the test example. For the sake of simplification used in the simulation, the transducer is an explanatory diagram explaining the averaging model. The figure which shows the waveform display part of the instantaneous value simulation result. The figure which shows the 3LG sequence and 1LG sequence used in the simulation. The figure which shows the simulation result of a 3LG sequence. The figure which shows the simulation result of 1LG sequence. Block diagram of current control based on general vector control. Block diagram of PLL. The schematic diagram which connected the virtual synchronous machine equipped with the voltage control type virtual synchronous machine control to the system. A block diagram showing an example of virtual synchronous machine control based on the solution of an equation.

Hereinafter, the present invention will be described in detail based on the embodiments.

(Embodiment 1)
FIG. 1 shows a block diagram of a voltage control type virtual synchronous machine control device of the voltage control type virtual synchronous machine according to the first embodiment of the present invention. The voltage control type virtual synchronous machine control device is incorporated into a general converter to function as a converter provided with voltage control type virtual synchronous machine control for suppressing overcurrent. Since the converter itself is the same as the conventional one, the description here will be omitted.

As shown in FIG. 1, the voltage control type virtual synchronous machine control device 1 includes a voltage control type virtual synchronous machine control unit 10 and a compensation control unit 20.

The voltage control type virtual synchronous machine control unit 10 has the same configuration as the control unit that performs general voltage control type virtual synchronous machine control, and has the virtual synchronous machine voltage command value vector vV _order and the rotor phase of the virtual synchronous machine. It has a coordinate conversion unit 11 that receives an angle and converts the coordinates, and a PWM control unit 12 that determines a duty ratio for pulse width control based on the coordinate-converted data. In the present embodiment, the adder 13 is provided in front of the coordinate conversion unit 11.

The compensation control unit 20 receives the measured system voltage vector vV _sys and the virtual synchronous machine voltage command value vector vV _order , obtains the voltage difference V _diff between them, and obtains the system voltage vector vV _sys and the virtual synchronous machine voltage command value. The intersection of the straight line connecting the vector vV _order and the control circle S with the radius r centered on the system voltage vector vV _sys is the compensation output voltage vector vV _conv-rev , and the virtual synchronous machine voltage command value vector vV _order is the starting point. A compensating voltage vector vV occ having a compensating output voltage vector vV _conv-rev as an end point is obtained, and a compensating voltage calculation unit 21 for outputting the compensating voltage vector vV _occ and a switch element 22 are provided. The switch element 22 is turned off when the voltage difference V _diff obtained by the compensating voltage calculation unit 21 is the same as or smaller than the radius r of the control circle, nothing is output to the adder 13, and the voltage difference V _diff becomes. When it is larger than the radius r of the control circle, it is turned on and controlled to output the compensating voltage vector vV _occ , which is the output from the compensating voltage calculation unit 21, to the adder 13.

As a result, when the voltage difference V _diff is the same as or smaller than the radius r of the control circle, nothing is output from the compensation control unit 20 to the adder 13, so that the virtual synchronous machine voltage command value vector vV _order is the coordinate as it is. It is input to the conversion unit 11, and the voltage command value vector vV _order of the virtual synchronous machine becomes the output voltage V _conv of the voltage control type virtual synchronous machine as it is, while the voltage difference V _dim is compensated when it is larger than the radius r of the control circle. Since the compensating voltage vector vV _occ , which is the output from the voltage calculation unit 21, is output to the adder 13, the compensating output voltage vector vV _conv- in which the compensating voltage vector vV _occ is added to the virtual synchronous machine voltage command value vector vV _order . The _rev is output to the coordinate conversion unit 11 as the compensation output voltage command value, and as a result, the compensation output voltage vector vV _conv-rev becomes the output voltage V _conv of the voltage control type virtual synchronous machine.

The above control is schematically shown in FIG.

FIG. 2 shows the system voltage vector _vV system obtained by converting the output voltage command value and the measured system voltage value into a rotation coordinate system consisting of the D axis and the Q axis, and the virtual synchronous machine voltage command value vector vV _order on the rotation coordinate axis. It shows the control circle S having a radius r centered on the system voltage value which is the end point of the system voltage vector vV _sys . The radius r is a preset value. The DQ conversion is performed based on the rotor phase of the virtual synchronous machine, and the virtual synchronous machine voltage command value vector vV _order always exists on the D axis.

In FIG. 2A, the system is relatively normal, the voltage difference V _diff between the system voltage vector _vV system and the virtual synchronous machine voltage command value vector vV _order is small, and the virtual synchronous machine voltage command value vector vV _order is output as it is. The state where the voltage is V _conv is shown.

In FIG. 2B, the system is disturbed, the voltage difference V _diff between the system voltage vector _vV system and the virtual synchronous machine voltage command value vector vV _order becomes large, and the virtual synchronous machine voltage command value vector vV _order is a control circle. In the case of going out of S, the compensating output voltage vector vV _conv-rev obtained by adding the compensating voltage vector vV _occ to the virtual synchronous machine voltage command value vector vV _order is output to the coordinate conversion unit 11, and as a result, the compensating voltage vector vV conv-rev is output. It shows a state in which the output voltage vector vV _conv-rev is controlled so as to be the output voltage V _conv of the voltage control type virtual synchronous machine.

Here, the control by the compensation control unit 20 will be described more specifically.
First, the difference V _diff between the virtual synchronous machine voltage command value _Volder and the absolute value of the system voltage V _sys is calculated.

V _diff = | V _order -V _systems |

Next, when the difference V _diff of the absolute value exceeds r, the compensating voltage V _{coder and V qcor are} added to the virtual synchronous machine voltage command value V _order . The compensating voltage V _docor and V _qcor correspond to the compensating voltage vector vV _occ-rev .

The compensating voltages V coder and V _qcor added at this time are system voltage values V as _viewed from the virtual synchronous machine voltage command value _volter so that the output voltage V _conv of the final voltage control type virtual synchronous machine is within the control circle S. Compensation is added in the _sys direction. As specific values, the following compensating voltages V _dockor and V _qcor are applied to the D-axis and Q-axis voltages, respectively.

The equation (1) for obtaining the compensating voltage V _dockor and V _qcor (D-axis voltage and Q-axis voltage of the virtual synchronous machine voltage command value _Volder , respectively) is as follows.

V _diff = (V _diff -V _order ) x (V _diff -r) / V _diff
V _qcor = V _qsys × (V _diff -r) / V _diff ... (1)

FIG. 3 shows an example of a control block diagram of the voltage control type virtual synchronous machine control device including the compensation control unit 20 of the first embodiment.

FIG. 3 shows that the control via the compensation control unit 20 is added instead of the virtual synchronous machine voltage command value _Volder in the control block diagram of FIG. As shown in the figure, the compensating voltage calculation unit 21 inputs the system voltage values V _dsys and V _qsys , the radius r of the control circle S, and the virtual synchronous machine voltage command value _Volder , and the compensating voltage is input from the above equation (1). V _docc and V _qoc are obtained and output. The switch element 22 is controlled by the voltage compensation flag F _diff , and outputs the compensation voltages V _docc and V _qoc in the on state, and outputs 0 in the off state. Here, if V _diff > r, it is turned on by 1, and if V _diff ≤ r, it is turned off by 0. When the switch element 22 is on, the adder 13 adds the virtual synchronous machine voltage command value _{Volder and the compensating voltage V docc and} V _qoc to output V _doconv and V _qconv , and when the switch element 22 is off, the adder 13 outputs V doconv and V qconv. , The virtual synchronous machine voltage command value _Volder is output as it is as V _dconv and V _qconv .

In the example of FIG. 3, the radius r of the control circle S is variable, and is changed to r ₁ when the converter current is equal to or less than the threshold value and r ₂ when the converter current exceeds the threshold value by the overcurrent flag F _oc .

In the compensating control unit 20 described above, the compensating voltage calculation unit 21 always obtains the compensating voltage vector vV _occ and outputs it, and the voltage control type virtual synchronous machine is used only when the voltage difference V _diff is larger than the radius r. The compensating voltage vector vV _occ is output to the adder 13 of the control unit 10, but the compensating control is not limited to this, and the compensating voltage vector vV _occ is obtained only when the voltage difference V _diff is larger than the radius r. This may be output.

Further, when the virtual synchronous machine voltage command value vector vV _order is compensated by the voltage control type virtual synchronous machine control unit 10, the compensation voltage vector vV _occ is added to the virtual synchronous machine voltage command value vector vV _order by the adder 13. However, it is not limited to this, and when compensation is required, the compensation output voltage vector vV _conv-rev is output from the compensation control unit 20 and replaced with the virtual synchronous machine voltage command value vector vV _order . The compensating output voltage vector vV _conv-rev may be input to the coordinate conversion unit 11.

Further, the configuration of the voltage control type virtual synchronous machine control unit 10 is not particularly limited, and any conventionally known voltage control type virtual synchronous machine control may be used.

Further, the radius r of the control circle S is determined by how much the overcurrent is to be suppressed, and is obtained by referring to the reactor component value of the simulated generator simulated by the voltage control type virtual synchronous machine control. Is preferable.

For example, when the reactor value is R (pu), it is preferable that r = R ± 20%.

Further, the radius r does not have to be a fixed value, and may be changed according to the state of the system.

(Embodiment 2)
In the above-described embodiment, the compensating output voltage vector vV _conv-rev is defined as the intersection of the straight line connecting the system voltage vector vV _sys and the virtual synchronous machine voltage command value vector vV _order and the control circle S, but is limited to this. It is not something that will be done. This embodiment shows another example of the compensating output voltage vector vV _conv-rev .

The compensated output voltage vector vV _conv-rev of this embodiment is shown in FIG. As shown in the figure, the compensating output voltage vector _{vV conv-rev} of the present embodiment is the vector _vV system of the system voltage value V system or the output voltage command value among the two intersections of the straight line extending the vector and the control circle S. It is a vector showing a voltage value close to _Vorder .

This embodiment is basically the same as that of the first embodiment except that the compensating output voltage vector vV _conv-rev is changed, and the virtual synchronous machine voltage command value vector vV _order goes out of the control circle S. In this case, the compensation output voltage vector vV _conv-rev is output, and duplicate description will be omitted.

The specific determination of the compensating output voltage vector vV _conv-rev of the present embodiment is as follows.

In the case of FIG. 4, the virtual synchronous machine voltage command value _Vorder is extended from the zero point in the system voltage value _Vsys direction so as to be within the control circle S. As specific values, the following compensating voltages V _dockor and V _qcor are applied to the D-axis and Q-axis voltages, respectively.

V _dconv = V _dsys × (| V _system | + | r |) / | V _system |
V _qconv = V _qsys × (| V _system | + | r |) / | V _system |

The method of determining the compensating output voltage vector vV _conv-rev is not limited to this, and the compensating output voltage vector vV _conv-rev that fits within the control circle S may be used, but voltage-controlled virtual synchronous machine control is performed. However, for the purpose of compensating, it is preferable that the voltage value in the control circle S is as close as possible to the virtual synchronous machine voltage command value _Volder , and from this viewpoint, it is preferable on the control circle S. Further, for the purpose of compensation, it is preferable that the voltage value within the control circle S between the virtual synchronous machine voltage command value _Volder and the system voltage value V _sys is close to the virtual synchronous machine voltage command value _Volder .

(Test example)
In order to verify the effect of the present invention, operation verification was performed by instantaneous value simulation. The simulation was carried out using XTAP (eXpandable Transient Analysis Program), which is an instantaneous value analysis program.

FIG. 5 shows a schematic diagram of the analysis target system used in the simulation. As a converter equipment equipped with virtual synchronous machine control, an ideal voltage source is connected to the DC side of the converter. Originally, various facilities such as batteries, distributed power supplies, and other AC systems via the DC transmission network are assumed on the DC side of the converter, but in this test, the overcurrent controlled by the voltage-type virtual synchronizer is assumed. These facilities were idealized for the purpose of verifying only suppression, and replaced with an ideal voltage source.

The AC system consists of a voltage source simulating an infinite bus, a resistance simulating a short circuit capacity, and a reactor. Here, the short-circuit capacity ratio was set to 6.93 for two lines. The accident point on the AC side was set to the nearest end of the converter, and the AC accident was eliminated by opening the accident line with a circuit breaker.

The converter uses an averaging model to simplify the calculation. The averaging model is a model that does not simulate switching as in the detailed converter model shown in FIG. 6A, but averages ripples with the switching period as the averaging interval as shown in FIG. 6B. Is. In addition to reducing the circuit scale, it is possible to extend the calculation time increments, and the effect of reducing the amount of calculation is high.

Table 1 shows various conditions used in the calculation. Further, FIG. 7 shows the waveform display location of the instantaneous value simulation result. In this simulation, each system disturbance is controlled by three patterns. It should be noted that the presence of overcurrent control mimics the first embodiment, and the control circle S is that of the first embodiment.

Case a: No overcurrent suppression control
Case b: With overcurrent suppression control (radius r of control circle S is fixed at 0.2pu)
Case c: With overcurrent suppression control (radius r of steady-state control circle S is 0.2pu, radius r when overcurrent exceeds 1.2pu is 0.1pu)

FIG. 8A shows a sequence of a three-phase ground fault (3LG). The time from the generation of 3LG to the opening of the AC circuit breaker is set to 0.1 seconds (5 cycles). AC accidents are eliminated by opening the accident line.

FIG. 8B shows a one-phase ground fault (1LG) sequence. The time from the generation of 1LG to the opening of the AC circuit breaker is set to 0.1 seconds (5 cycles). The AC accident is eliminated by opening the accident line, and at this time, the accident line shall be opened for all three phases.

The results of the simulation under the above conditions are shown in FIGS. 9 and 10.

FIG. 9 is an enlarged view of V systems and I _conv when _3LG occurs, and (a) to (c) correspond to the above-mentioned Cases a to c. In the absence of the overcurrent suppression control of (a), a maximum of 9.19 pu of overcurrent flowed through the converter (converter current rating of 1458 Apeak), whereas in contrast to the case b of (b) and (c), When the overcurrent suppression control of c was performed, the values were 1.58pu and 1.37pu, respectively, and the overcurrent suppression effect could be confirmed.

FIG. 10 _{is an enlarged view of V systems and I conv when} 1 LG is generated, and (a) to (c) correspond to the above-mentioned Cases a to c. In the case of (a) without the overcurrent suppression control, a maximum of 2.94pu of overcurrent flowed through the converter, whereas in the case of case b and c with the overcurrent suppression control, 1.64pu and 1.64pu, respectively. It was 1.45 pu, and the overcurrent suppression effect was confirmed.

1 Voltage control type virtual synchronous machine control device 10 Voltage control type virtual synchronous machine control unit 11 Coordinate conversion unit 12 PWM control unit 13 Adder 20 Compensation control unit 21 Compensation voltage calculation unit 22 Switch element

Claims (7)

It is a voltage control type virtual synchronous machine control device that controls the voltage control type virtual synchronous machine for the converter.
Equipped with a control unit that controls a voltage-controlled virtual synchronous machine,
The control unit includes a compensation means for compensating for an output voltage command value input to the control unit.
The compensating means converts the output voltage command value and the measured system voltage value into a rotational coordinate system consisting of the D axis and the Q axis, and uses a control circle having a radius r centered on the system voltage value as a limiter. , The voltage control is characterized in that the compensated output voltage command value existing on or inside the control circle is set as the output voltage command value, provided that the output voltage command value is outside the control circle. Type virtual synchronous machine control device. The voltage control type virtual synchronous machine control device according to claim 1, wherein the compensation output voltage command value is on the control circle and close to the system voltage value. The voltage control type virtual synchronizer according to claim 1 or 2, wherein the radius r is a value obtained from the reactor component value of the simulated generator simulated by the voltage control type virtual synchronizer control. Control device. When the voltage difference V _diff between the vector vV _order of the output voltage command value and the vector vV _sys of the system voltage value is larger than r, the compensating means has the output voltage command value V _order and the system voltage value V _sys . A compensating output voltage vector vV _conv-rev which is a voltage value V _conv between and is on or inside the control circle is determined, and this compensating output voltage vector vV _conv-rev is used as the compensating output voltage command value. The voltage control type virtual synchronous machine control device according to any one of claims 1 to 3, wherein the voltage control type virtual synchronous machine control device is characterized. The compensating output voltage vector vV _conv-rev is a vector to the intersection of the straight line connecting the vector vV _order of the output voltage command value V _order and the vector vV _sys of the system voltage value V _sys and the control circle. The voltage control type virtual synchronous machine control device according to claim 4, wherein the voltage control type virtual synchronous machine control device is characterized. The compensating output voltage vector _{vV conv-rev} is a voltage value close to the output voltage command value _Volder at the intersection of the vector _vV system of the system voltage value V system or the straight line extending the vector and the control circle. The voltage control type virtual synchronous machine control device according to claim 4, wherein the vector indicates the above. A voltage control type virtual synchronizer comprising the voltage control type virtual synchronizer control device according to any one of claims 1 to 6.

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