JPH053632A - Parallel operation system for generator - Google Patents

Abstract

PURPOSE:To make it possible to share burden of stable effective and reactive power during parallel operation, to reduce fluctuations in system voltage and frequency and to restrict cross current immediately after synchronizing of generator. CONSTITUTION:At the same time with the start of synchronizing, the voltage and frequency of each generator 1a, 1b are adjusted to reference values, breakers are closed at the phase matching point of each generator and, after synchronizing, terminal controllers 15a and 15b are provided, which share the effective and reactive power of the generator during parallel operation. In order to control the voltage and frequency of bus to constant values after synchronizing by the terminal controller, the voltage, frequency and effective and reactive power of generator at opposite sides are sent to and received by serial transmitting units 14a and 14b between the terminal controllers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention suppresses a circulating current (cross current) flowing between generators during parallel operation and controls each generator to operate stably in parallel. It is about.

[0002]

2. Description of the Related Art FIG. 4 shows, for example, No. 1 of the Japan Society for Marine Engine Science.
Volume 0, No. 6, "Actual machine test of multi-machine parallel operation system by differential cross current compensator" Sakamoto, Negishi, Takeda shown conventional conventional cross current compensation circuit, in the figure, 1 is a generator, 1e Is an excitation winding of the generator 1, 3 is an automatic voltage regulator, (hereinafter, A
4) AVR3 voltage detection transformer, 5 cross current compensation resistor, 6 load current detection current transformer, 7 power supply breaker (hereinafter referred to as ACB), 7g ACB7
It is an auxiliary contact of and opens when ACB7 is closed. Reference numeral 16 is a synchronous closing device that closes the ACB 7 at a phase matching point of both generators when operating in parallel with another generator (not shown). In addition, FIG. 5 shows the voltage of each part of the cross current compensation circuit shown in FIG.
It is a vector diagram of an electric current.

Next, the operation will be described. In order to perform stable parallel operation of the generator 1 and other generators, it is necessary to suppress the invalid cross current that flows between the generators that are in parallel operation. Therefore, when the ACB7 is synchronously closed by the synchronous closing device 16, the auxiliary contact 7a is closed before the ACB7 is closed, so that the resistor 5 is short-circuited and the voltage of the generator 1 does not depend on the load current and is equal to that of the AVR3. It is maintained at the set voltage (constant voltage). Next, when the ACB 7 completes the synchronous closing, the resistor 5 is connected in series to the input circuit of the AVR 3 on both the generator 1 side and the bus bar side, and a current proportional to the load current of the generator 1 flows through the resistor 5.

When the generator current is delayed, a vector voltage drop Vr is generated across the resistor 5, and the vector input voltage Vc of the AVR 3 is the vector input voltage Vc = vector according to the vector diagram shown in FIG. Voltage Ve
+ Vector voltage drop Vr. That is, in the generator 1 in which the voltage is high and the reactive delay current has flowed, a signal that the input voltage of AVR3 is high is given to the AVR3, and the field winding 1e is supplied.
On the other hand, when the voltage is low, the opposite action takes place and the reactive cross current disappears. At the time of load balancing, the vector voltage drop Vr of the resistor 5 is also equal,
The input voltage of VR3 also becomes equal, the voltages of both generators also match, and no cross current flows.

In the lateral current compensator connected to the differential current transformer, which is the method of the above-mentioned document, at the time of load balancing, the current proportional to the load current is generated only in the ring circuit of the differential current transformer and the lateral current compensator. And the vector voltage drop Vr across the resistor 5 becomes zero. Therefore, the input voltage of the ACR 3 is only the detection voltage of the bus voltage, and the voltage fluctuation rate has a small value as in the single operation.

[0006]

Since the conventional cross current compensation circuit is constructed as described above, even if the load is balanced during parallel operation of the generator 1, the voltage droops in proportion to the reactive current of the load. In addition, in a cross current compensator with a differential current transformer connected, the voltage fluctuation is small when the load is in parallel, but if the control device is divided and arranged for each generator, it may go through the differential current transformer or the ring circuit may be disconnected or At the time of a short circuit or the like, there were problems such as damage to the generator 1 and system sway due to the difference in drooping characteristics of the generator 1 during parallel operation.

The present invention has been made in order to solve the above problems, and in order to reduce the signal between both generators and to detect disconnection and short circuit, a signal is transmitted and received using a serial transmission device, and this serial signal is transmitted and received. Even if the signal is delayed due to the transmission device, it is possible to perform stable synchronous closing, that is, to suppress the cross current immediately after the closing and reduce the fluctuations of the voltage and frequency of the system, and to enable and disable the stable operation during parallel operation. The purpose is to obtain a parallel operation system of generators that enables sharing of electric power.

[0008]

A parallel operation system for a generator according to the present invention is arranged such that the voltage and frequency of each generator are adjusted to a reference value by an operation set of a cross current compensating circuit at the same time as the start of synchronous operation. At the phase matching point of the generator, the circuit breaker for synchronous closing is turned on, and after the synchronous turning on, the terminal control device that shares the active / reactive power of the generator in parallel operation is provided, and after the terminal control device turns on the synchronous In order to constantly control the voltage and frequency of the busbar, the serial transmission device transmits and receives the voltage, frequency and active / reactive power of the counterpart generator between the terminal control devices.

[0009]

In the terminal control device according to the present invention, at the same time when the synchronization is started, the cross current compensation circuit is set to the characteristic that the voltage droops due to the reactive power amplification of the generator, and the fluctuation of the voltage and frequency at the time of the synchronization is prevented. Therefore, after adjusting the voltage and frequency of both generators to the reference value before turning on, the circuit breaker is turned on at the phase matching point of these two generators, and after the turning on, sharing of active / reactive power is performed. Let

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1a and 1b are generators, 2a and 2b
Is a prime mover driving the generators 1a and 1b, 2c and 2d are governor motors for frequency control, and 3a and 3b are excitation windings 1.
AVR that supplies a voltage-controlled excitation current to c and 1d,
4a and 4b are voltage detection transformers, 5a and 5b are resistors for cross current compensation, 6a and 6b are current transformers for load current detection, and 7a.
a and 7b are ACBs, 7c and 7d are auxiliary contacts of ACBs 7a and 7b, 8a and 8b are voltage detection circuits that detect the output system voltage of the generators 1a and 1b, and 9a and 9b are frequencies that also detect the output system frequency. Similarly, the detection circuits 10a and 10b are active / reactive power circuits that detect active power and reactive power of each output system frequency.

Further, 11a and 11b are detection circuits 8a and
An analog input circuit for converting the analog data detected by 8b, 9a, 9b, 10a and 10b into a digital signal, 12
a and 12b are arithmetic circuits for performing various arithmetic operations, and 13a and 13b.
Receives the results of the arithmetic circuits 12a and 12b, and outputs ACB7
a, 7b, AVR 3a, 3b, governor motor 2a, 2b
A digital output circuit for outputting each control signal of
14b is a serial transmission device for exchanging signals between the other arithmetic circuits 12a and 12b, and 15a and 15b are voltage detection circuits 8a and 8b, frequency detection circuits 9a and 9b, active / reactive power detection circuits 10a and 10b, and analog input circuit. 11a,
1b, arithmetic circuits 12a and 12b, digital output circuit 13
It is a terminal control device including a and 13b. Where 20
a and 20b are field windings 1c and 1d, AVRs 3a and 3b,
It is a cross current compensation circuit including resistors 5a and 5b, voltage detection transformers 4a and 4b, and current transformers 6a and 6b. In addition, FIG.
3 is a characteristic diagram of reactive power vs. voltage in each system under the configuration of FIG. 1, and FIG. 3 is a flowchart of control operation according to one embodiment of the present invention.

Next, the operation will be described. First, the voltage, frequency, active / reactive power of the output system of each generator 1a, 1b is detected by each detection circuit 8a, 8b, 9a, 9b, 10a, 10
It is detected by b and is input to the arithmetic circuits 12a and 12b via the analog input circuits 11a and 11b. The data of the other generators 1a and 1b are input to the arithmetic circuits 12a and 12b via the serial transmission devices 14a and 14b, respectively (step ST1). Further, the arithmetic circuits 12a and 12b determine whether each of the generators 1a and 1b is independent or parallel, based on the signals corresponding to the states of the auxiliary contacts 7c and 7d of the ACBs 7a and 7b (step ST2). When the arithmetic circuits 12a and 12b determine that they are independent, the relays 13c and 13d of the digital output circuits 13a and 13b are used.
Then, the resistors 5a and 5b are short-circuited so that the voltage droop becomes almost zero (step ST3).

Further, in this state, the arithmetic circuits 12a, 1
2b compares the voltage and frequency detected by each detection circuit 8a, 8b, 9a, 9b with an internal reference value, and the digital output circuit 13a, so that the comparison result is the internal reference value.
AVRs 3a, 3b and governor motors 2c, 2d are controlled via 13b (step ST4). For this reason,
The voltage characteristic is almost constant like V ₁ in FIG.

Next, regarding the parallel operation, the ACB 7a
The case of synchronizing input will be described. First, a parallel operation start signal (not shown) is output, and when it is determined that parallel operation has started (step ST5), each cross current compensation circuit is set. That is, the auxiliary contacts 7c and 7d are opened and the AVR3
Resistors 5a and 5b are connected in series to the input circuits of a and 3b, and voltage drooping characteristics are given to the generators 1a and 1b as shown by V ₂ in FIG. 2 (step ST6). At this time, if the generators 1a and 1b have a reactive power load, the voltage droops. Therefore, the voltages and frequencies of the generators 1a and 1b are independently set to the reference values as shown by V ₃ in FIG. 2 before the synchronization is input so that the system voltage and the frequency do not change after the parallel operation (synchronization). Control (step ST7, ST
8). In this case, the frequency of the generator 1a on the ABC input side (low load side) is set slightly higher than the reference value to facilitate phase matching of both units and prevention of reverse power generation after input.

Next, in this state, it is judged whether or not the phases of the two generators 1a and 1b match (step ST9), and if they match, the ACB 7a closing signal is output (step ST9).
10) The parallel operation is started (step ST11). A
At the moment after CB7a is closed, the voltage and frequency of both units are almost the same, and the cross current compensation circuit is also set. Therefore, according to the principle shown in the prior art, cross current compensation is started at the same time, and stable reactive power sharing is performed. Be seen.

In this case, the ACB 7a shown in the prior art is used.
In the cross current compensation circuit set after closing, the two generators 1a, 1b
Due to a delay in serial transmission between the two generators 1a and 1b, a difference occurs in the cross current compensation circuit set. For example, in FIG. 2, the generator 1a is immediately set when the ACB 7a is closed, so that the characteristic becomes V _2. However, there is a case where the generator 1b is delayed by serial transmission and the ACB 7a is closed while keeping the characteristic of V ₁ , and excessive reactive power flows to the generator 1b. The present invention can prevent these.

After the ACB 7a is closed and a time period during which stable control by serial transmission is possible, the voltage, frequency, and active / reactive power of another generator 1b in parallel operation are input by the serial transmission devices 14a and 14b. The voltage and frequency are controlled by the arithmetic circuits 12a and 12b so that the average value of the voltage and frequency of both generators 1a and 1b becomes equal to the internal set value (reference value). In addition, regarding the active / reactive power, in the arithmetic circuits 12a and 12b, the active / reactive power of the generators 1a and 1b is set by calculation (reference value), that is, the active power of the generators 1a and 1b is set. Active power = total active power load x (total rated active power of the machine / sum of rated active power of generators operating in parallel), while the reactive power of the generators 1a, 1b is Each of the AVR 3a is set to the digital output circuit 1 so that the set reactive power = total reactive power load × (total rated reactive power of the machine / total rated reactive power of the generators in parallel operation).
Control is performed via 3a (step ST12). In addition,
Although the serial transmission devices 14a and 14b are used for exchanging information between the two generators 1a and 1b in the above embodiment, other devices may be used as long as the information can be exchanged.

[0018]

As described above, according to the present invention, the voltage and frequency of each generator are adjusted to the reference values by the operation set of the cross current compensation circuit at the same time when the synchronous closing is started, and then the phase matching point of each generator is adjusted. Then, a circuit breaker for synchronous closing is turned on, and after the synchronous turning on, a terminal control device for sharing the active / reactive power of the generator in parallel operation is provided, and the terminal control device causes the voltage of the bus bar after the synchronous turning on, In order to control the frequency at a constant level, the serial transmission device is configured to send and receive the voltage, frequency, and active / reactive power of the other generator between each terminal control device. It is possible to obtain a stable parallel operation by decentralized control between operating devices that can prevent cross current increase due to delays such as delays, fluctuations in the system voltage and frequency, and do not require complete synchronization between both generators. Effect There is.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a parallel operation system of a generator according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between reactive power and output voltage of each generator under the configuration of FIG.

FIG. 3 is a flowchart showing an operation procedure of parallel operation control of the generator according to the embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional cross current compensation circuit.

FIG. 5 is a vector diagram showing voltages and currents in respective parts of a conventional cross current compensation circuit.

[Explanation of symbols]

 1a Generator 1b Generator 7a Circuit breaker 7b Circuit breaker 14a Serial transmission device 14b Serial transmission device 15a Terminal control device 15b Terminal control device 20a Cross current compensation circuit 20b Cross current compensation circuit

Claims (1)

Claim: What is claimed is: 1. A cross-current compensating circuit for supplying a cross-current compensation voltage proportional to load currents of two generators that are operated in parallel by synchronous closing, to a field winding of the generator. Simultaneously with the start of synchronous closing, after adjusting the voltage and frequency of each generator to the reference value by the operation set of the cross current compensation circuit, at the phase matching point of each generator, close the circuit breaker for synchronous closing and synchronize. After the power is turned on, the terminal control device that shares the active / reactive power of the generators that are operating in parallel with each other and the voltage and frequency of the busbar after the synchronous power is turned on are controlled to be constant by the terminal control device. A parallel generator system with a serial generator that transmits and receives the voltage, frequency and active / reactive power of the side generator.