JPH0923657A - Controlling of inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the overload of an inverter device (SVG) when active power and reactive power are simultaneously input. SOLUTION: In controlling an inverter device wherein reactive power is compensated, with active power being interchanged between two systems by means of two inverters to which a serial circuit is connected, limiters 7', 8 which limit compensation amounts from an active power compensation detector 5 and a reactive power compensation detector 6 to a rated value of the device are installed. The control is conducted with top priority being put on a reactive power compensation amount Q from the limiter 8. Then, in a device excessive power calculating circuit 10, the square of the reactive power compensation amount Q(%) is found and the obtained value is subtracted from the device rated value (100%) and then the square root of the result (√(1<2> -Q<2> )=P) is found, and based on the obtained excessive power signal (active power), a limit value of the limiter 7' is changed to P(%) and a compensation amount of the active power is limited accordingly. By this method, the inverter device can be so controlled that the vector sum of the compensation amounts of active power and reactive power may not exceed the rating of the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device in which two AC power supply systems are connected to two inverters in which a DC circuit is commonly connected, and active power is exchanged between the two systems while also compensating reactive power. Regarding control method.

[0002]

2. Description of the Related Art FIG. 1 shows a secondary side T of a Scott transformer 1.
Seat, showing a single-phase two systems 2 _T, 2 _M inverter which performs reactive power compensation and active power interchange (SVG) 3 from M locus.
This inverter device 3 is composed of inverters 3 _T and 3 _M in which the AC side is connected to the first system (T seat) 2 _T and the second system (M seat) 2 _M , and the direct current side is commonly connected.

If reactive powers Q _T and Q _M and active powers P _T and P _M of the AC systems 2 _T and 2 _M are detected and the inverter device 3 is controlled as follows, as shown in FIG. Reactive power on the grid side is reduced and active power is balanced.

1) Compensation of reactive power is performed by controlling the voltage of the inverter for each locus.

2) Active power interchange detects the difference in active power between two seats and halves the amount by the phase control of each inverter.

Conventionally, flexible and reactive power compensation of active power by the inverter device 3, as shown in FIG. 8, the load voltage V _T (V _M) of each line, effective power interchange amount from the load current I _T (I _M) And the reactive power compensation amount are detected by the active power compensation amount detection circuit 5 and the reactive power compensation amount detection circuit 6, and the active power compensation amount and the reactive power compensation amount are detected by the limiters 7 and 8 which set 100%. Command P * and reactive power command Q
* Is output and the inverter 3 _T (3 _M ) is phase (or frequency) controlled and voltage controlled. Limiter circuit 7
And 8 limit the output of active power and reactive power so that the device will not be overloaded even if the load exceeds the rated output capacity of the device.

[0007]

Since the above-mentioned conventional inverter device is provided with a limiter for each of active power and reactive power, the device will not be overloaded with a single excessive load. However, as shown in FIG. 4 (b), when active / reactive power loads are input at the same time,
Even if the respective power amounts are within the device rating (100%), the combined device output power may exceed the device rating, and it is not possible to prevent overload.

Further, in such a device, the maximum imbalance when the load is normal is as shown in FIG.
In the case where one seat has no load and the other seat has a rated load, the unbalance amount is 100% of the load rating, and the compensation amount of the SVC device is ± 50% of the load rating.

However, as shown in FIG. 9B, when the load is a vehicle or the like, the load may not only take in active power but may also expel active power due to regenerative operation or the like. In this case, one side may be + 100% of the load rating (normal load) and the other side may be -100% (regenerative mode). In this case, the unbalance amount is 200% and the load rating is 2%.
This doubles the amount of compensation of the inverter device to 2 times the load of the related art, and the load on the inverter device also increases.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide an active power accommodation amount or a reactive power in an inverter device for accommodating active power and compensating for reactive power. It is an object of the present invention to provide a control method for an inverter device that applies an optimal limiter to the power compensation amount so that the output capacity does not exceed the rating.

[0011]

In order to achieve the above object, the present invention uses two inverters in which two alternating-current power supply systems are commonly connected to a direct-current circuit so that active power is exchanged between the two systems. However, in the inverter device that compensates the reactive power, (1) two limiters are provided to limit the compensation amount of the active power and the reactive power, respectively, by the device rating (100%), and the compensation amount of the active power and the reactive power from the limiter. One of the two is prioritized and controlled, and the square of the reactive power or active power compensation amount (%) to be prioritized is calculated, and this is calculated as the device rating (100
%), And then calculate the square root of the result. If the calculated signal is larger than the other compensation amount that does not allow priority control, compensate it as it is, and if it is smaller, change the limiter limit value that limits the other compensation amount. The vector sum of the compensation amounts of electric power and reactive power does not exceed the device rating.

(2) Alternatively, the detected amount is set as a + signal in the case of a normal active power load, and as a − signal in the case of a regenerative load, the effective power of the load is detected independently at each position, and the upper limit of each detected amount is detected. Is the device rating (100%) and the lower limit is limited to 0% of the rating. Apply each limiter to calculate the unbalanced amount from the active power detection amount of each seat with the limiter, and use the result as the active power compensation amount, and regenerate. The amount of compensation does not increase even if a load occurs.

(3) Alternatively, the reactive power of each system is used as the reactive power compensation command amount, and half of the active power difference between the two systems is used as the active power interchange command amount, and the vector sum of these command amounts is the rating of the device. The command value is limited so that it does not exceed the limit, and the allocation of the limiter for each command value is a fixed allocation that reduces the active power interchange amount by weighting the reactive power compensation amount according to the poor power factor of the load. It is the amount that can be operated within the equipment rating under any load.

[0014]

Embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 (FIG. 3) FIG. 3 shows a reactive power priority control circuit for controlling the inverter device 3 of FIG. 1 explained in the prior art by prioritizing reactive power.
3, 5 and 6, the load voltage V _T of 1 system 2 _T (2 system 2 _M) (V _M), the compensation amount of the load current I _T (I _M) from the inverter 3 _T (3 _M) Active power compensation amount detection circuit and reactive power compensation amount detection circuit for detection, 7'and 8
Is a variable limiter with an upper limit of 100%, which limits the active power compensation amount and the reactive power compensation amount output from the compensation amount detection circuits 5 and 6, respectively, and outputs the active power command value P * and the reactive power command value Q *. And a limiter with an upper limit of 100%.

[0016]

[Equation 1]

Numeral 10 is a device remaining power calculation circuit for changing the limit value of the variable limiter 7'by calculating the active power (device remaining power) by performing the calculation of the equation (1) and giving priority to the reactive power. A square calculator 11 for squaring the command value Q * (X%) and a subtracter 12 and a value from the subtracter 12 for subtracting the square calculation value X ² from the square (100%) ^{2 of the} device rating [(1
00%) ² −X ² ].

As described above, the device surplus calculation circuit 10 gives priority to the reactive power command value Q * from the 100% limit circuit 8 and maximizes the vector composite value of the reactive power command value Q * and the active power command value P *. Since the device surplus power of 100% is calculated and the limit value of the variable limiter 7 ′ is changed according to the calculation result to output the active power command value P *, the active power controlled by the inverter device 3 is controlled. And the vector sum of the reactive power does not exceed the device capacity as shown in FIG.

Therefore, even if an active power load and a reactive power load enter the 1-system or 2-system at the same time, the inverter device will not be overloaded.

If the active power compensation amount from the active power compensation detection circuit 5 is smaller than the active power calculated by the device surplus power calculation circuit 10, it is compensated as it is without being limited by the limiter 7 '.

Although the first embodiment is an example of the reactive power priority control, it goes without saying that the active power priority control can be similarly performed.

Embodiment 2 (FIG. 5) FIG. 5 shows an active power compensation amount detection circuit for controlling the inverter device 3 shown in FIG. 1 so as not to be overloaded during regenerative load. In FIG. 5, 5 ₁ and 5 ₂ are the voltages of the 1-system 2 _T ,
1 from current V _T , I _T and voltage of system 2 _M , current V _M , I _M
An active power detection circuit that detects active powers P _T and P _M of the system and the two systems.

7 ₁ and 7 ₂ are active power detection circuits 5 ₁ and 5 _2.
If the active power signal from is positive normal active power, it is limited to 100% of the rating of the inverter device 3, and if it is negative regenerative active power, it is limited to 0% of the upper limit 100.
%, Lower limit 0% limiter.

Reference numeral 15 is a subtracter for detecting the difference between the active power values from the limiters 7 ₁ and 7 ₂ , and 16 is the output of the 1-system active power compensation amount by halving the difference signal from the subtractor. Reference numeral 2 is a polarity inverter that inverts the output of the arithmetic unit 16 and outputs a 2-system active power compensation amount.

Since the active power command circuit is constructed as described above, the output signals P _T and P _M of the active power detection circuits 5 ₁ and 5 ₂ are output when the 1-system and 2-system loads are normal loads. Since it is a plus, if the active power P _T , P _M is within 100% of the rating, if it exceeds 100% as it is, the limiters 7 ₁ , 7 ₂
Is limited to 100% by the
_T- P _M is detected, and is divided into ½ by the computing unit 16 and the 1-system compensation amount (active power command of the inverter 3 _T ) ( _PT- P _M )
/ 2. Further, the output from the calculator 16 is 2-based compensation amount is inverted by polarity inverter 17 (power command of the inverter 3 _M) - a _{(P T -P M) / 2} . Therefore,
By controlling the inverters 3 _T and 3 _M with this active power command, the active power shown in FIG. 2 can be balanced.

When one of the loads of the 1st and 2nd systems is a normal load and the other is a regenerative load, for example, when the 1st system is a normal load and the 2nd system is a regenerative load, the output signal of the active power detection circuit 5 ₁ Since P _T is positive, active power P _T is 100% of the rating
If it is less than 100%, if it exceeds 100%, it is limited to 100% by the limiter 7 ₁ and input to the subtractor 15. On the other hand, the output signal P _M of active power detecting circuit 5 ₂ Since the negative, because it is limited to the lower limit value of 0% of the limiter 7 _2, input from the limiter 7 ₂ to the subtractor 15 becomes zero. Therefore, the output of the subtractor 15 becomes P _T , and the 1-system compensation amount from the calculator 16 becomes P _T / 2. Further, the two-system compensation amount from the polarity reversing device 17 becomes -P _M / 2.

Therefore, it is possible to perform balancing control of active power by ignoring the regenerative load component and detecting only the unbalanced component of a general load law. Therefore, the inverter device will not be overloaded by the regenerative load.

Embodiment 3 (FIGS. 6 and 7) FIG. 6 shows the inverter device 3 shown in FIG. 1 whose output capacity is rated by applying an optimal limiter to the reactive power compensation amount and active power accommodation amount from the load condition. The active / reactive power command circuit is controlled so that the power is not exceeded.

[0029] In FIG. 6, 21 _T 1 system 2 _T of the load voltage V _T, the reactive power Qd _T 1 system from the current I _T, active power Pd _T
Reactive-active power detection circuit for detecting, 21 _T 2 system of 2 _M load voltage V _M, the current reactive power Qd _M 2 system from I _M, disabled-active power detection circuit for detecting an active power Pd _M, 22 _T and 22 _M are limiters that limit the detected reactive powers Qd _T and Qd _M , 23 is a subtractor that finds the difference between the detected active powers Pd _T and Pd _M , and 24 is the average of the active power from the subtractor 1 / 2 arithmetic unit, 25 is a limiter for limiting the active power average value from the arithmetic unit 24, 27 _T is the limiters 22 _T and 2
Reactive power Qd _T from 5 and active power (Pd _T −Pd _M ).
1/2 system control circuit that controls the inverter 3 _T with / 2 as the reactive power compensation command and active power interchange command, 27 _M
Is a two-system inverter control circuit that controls the inverter 3 _M with the reactive power Qd _M and active power (Pd _T −Pd _M ) / 2 from the limiters 22 _M and 25 as the reactive power compensation command and active power interchange command.

However, as shown in FIG. 7, the reactive power is compensated and the active power is exchanged between the two systems 2 _T and 2 _M.

Here, the limiters 22 _T , 22 _M and 25 are provided with optimum limiters for the reactive power compensation amount and the active power interchange amount so that the output capacity of the inverter device 3 does not exceed the rating.
Set to the optimum limit value.

Regarding the optimum limit value, the electric railway load is often a vehicle with a power factor of about 0.7 to 0.85. A major factor that causes the voltage drop of the grid and feeder bus is the reactance drop due to the current of the delay component. Further, the current of the effective component does not cause a voltage drop as much as the current of the delay component, but has a great influence on the current imbalance on the three-phase side of the system. For this reason, making the reactive power compensation amount larger than the active power accommodation amount is more effective as a voltage effect countermeasure and not so much as an imbalance countermeasure.

Therefore, when a vehicle having a low power factor travels, the power system and feeder bus are most adversely affected. Therefore, if an optimum limiter is applied to the control command so that the output of the inverter device 3 will be within the rated value under this bad condition, no problem will occur with respect to a load with a high power factor.

Assuming that the load is 100% and the vehicle with the worst power factor (power factor 07) runs in one seat, the active power is 70% and the reactive power is 71.4%.

At this time, the capacity handled by the inverter device 3 is as follows.

Amount of active power exchange = 35% (70% / 2)
→ P ₀ = (100 × 0.7 / 2) ・ Amount of reactive power compensation = 71.4% → Q ₀ = 100 × √ (1
-0.7 ²⁾ and equipment capacity ^{= √ (35 2 +71.4 2)} = 79.5% → √
(P ₀ ² + Q ₀ ² ). Ratio of active power interchange amount to device capacity K ₁ ≈0.4
4 → P ₀ / √ (P ₀ ² + Q ₀ ² ) Therefore, the optimum limiter value of each output component with respect to the device capacity is as follows when the device capacity is 100%.

Active power limiter = 44%, reactive power limiter = 90% Therefore, the limit values of the limiters 22 _T and 22 _M are 90% of the inverter device rating, and the limit value of the limiter 25 is 44% of the inverter device rating. By setting to, it is possible to optimally control the reactive power compensation amount and the active power interchange amount.

[0038]

Since the present invention is configured as described above, the following effects can be obtained.

(1) No matter what kind of load is connected to the two systems, it is possible to operate within the device rating.

(2) According to the first aspect of the present invention, either active power or reactive power can be preferentially compensated while remaining within the device rating, so that the device can be effectively used.

(3) In the second aspect, when the load of one system becomes a regenerative load, only the unbalanced portion of the normal load is detected and the regenerative load portion is ignored to compensate the active power. Therefore, the overload of the device due to the regenerative load does not occur.

(4) According to the third aspect of the present invention, since the reactive power weighting compensation control secures the active power compensation capacity, the voltage drop and the current imbalance can be effectively dealt with at the same time. In addition, since the active power interchange amount and the reactive power compensation amount are limiters that are vector-calculated, an effective output can be output.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an inverter device (SVG).

FIG. 2 is an explanatory diagram of power balancing by accommodating active power.

FIG. 3 is a configuration diagram of an active / reactive power command circuit according to the first embodiment, which gives priority to reactive power.

4A and 4B are combined vector diagrams of a priority control sequence and active / reactive power of a conventional example.

FIG. 5 is a configuration diagram of an active power compensation amount detection circuit according to a second embodiment.

FIG. 6 is a configuration diagram of an active / reactive power command circuit according to a third embodiment.

FIG. 7 is an explanatory diagram of active / reactive power control.

FIG. 8 is a configuration diagram of an active / reactive power command circuit according to a conventional example.

9A and 9B are explanatory views of unbalance in the case of a general load and the case of a regenerative load.

[Explanation of symbols]

1 ... Scott transformer 2 _T ... 1 system (T seat side system) 2 _M ... 2 system (M seat side system) 3 ... Inverter device (SVG) 3 _T , 3 _M ... Inverter 5, 5 ₁ , 5 ₂ ... Effective Power compensation amount detection circuit 6 ... Reactive power compensation amount detection circuit 7, 7 ₁ , 7 ₂ , 8 ... Limiter 7 '... Variable limiter 10 ... Device remaining capacity calculation circuit (vector calculation circuit) 11 ... Square calculation unit 12, 15 ... Subtractor 13 ... Square root calculator 16 ... 1/2 calculator 17 ... Polarity inverter 21 _T , 21 _M ... Reactive power / active power detection circuit 22 _T , 22 _M , 25 ... Limiter 24 ... 1/2 calculator 27 _T , 27 _M ... Inverter control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaaki Ono 2-1-1-17 Osaki, Shinagawa-ku, Tokyo Stock Company Shameidensha

Claims (3)

[Claims] 1. In the control of an inverter device for compensating reactive power while accommodating active power between the two systems by two inverters in which two alternating-current power supply systems are commonly connected to a direct-current circuit, active power and reactive power are controlled. The compensation amount of each device rating (1
00%), two limiters are provided, and either the active power or reactive power compensation amount from the limiter is prioritized and controlled, and the reactive power or active power compensation amount (%) that is prioritized is squared. And calculate the device rating (1
00%), and further calculate the square root of the result. If the calculated signal is larger than the other compensation amount that does not control priority, compensate as it is, and if it is smaller, change the limiter limit value that limits the other compensation amount. A method for controlling an inverter, characterized in that the vector sum of the compensation amounts of active power and reactive power does not exceed the device rating. 2. An inverter device for compensating for reactive power while accommodating active power between two systems by using two inverters in which two alternating-current power supply systems are commonly connected to a direct-current circuit, As a + signal for load and a-signal for regenerative load, the active power of the load is detected independently at each seat, and the upper limit of each detected amount is set to the device rating (100%) and the lower limit is set to 0% of the rating. Apply to each limiter to be limited, calculate the unbalance amount from the active power detection amount of each limiter, and use the result as the active power compensation amount so that the compensation amount does not increase even if a regenerative load occurs. A method of controlling an inverter device characterized by the above. 3. Each inverter of an inverter device composed of two inverters connected in common on the DC side has two inverters.
In the control of the inverter device that is connected to one AC power supply system and compensates the reactive power while exchanging the active power between the two systems, the reactive power of each system is set as the reactive power compensation command amount, and
Half of the active power difference between the two systems is the active power interchange command amount,
Limit values are applied to the command values so that the vector sum of these command values does not exceed the rating of the equipment, and the distribution of the limit values for each command value should be weighted to the reactive power compensation amount according to the poor power factor of the load. The control method of the inverter device is characterized by a fixed distribution amount that reduces the active power interchange amount so that any load can be operated within the device rating.