JPH01278241A - Power source system switching system - Google Patents

Abstract

PURPOSE:To switch both a commercial power source and a generator power source without momentary power interruption by providing a FF circuit for turning ON one of first and second semiconductor switching elements provided between a load and a power source and turning OFF the other. CONSTITUTION:The power of a generator 1 is monitored, detected by a generator power detector 16 by a generator power detector 16 on the basis of a voltage, a current from a generator power detecting transformer CT, and transmitted to a switching load selecting calculator 21. The calculator 21 selects an optimum switching load L1 on the basis of various information, a selected signal is fed to a zero-cross switching instruction unit 29 through an AND circuit 23 and an OR circuit 27, and a command for switching the load L1 from a bus A to a bus B is fed to a FF circuit 32. A driver 42 switches a FF circuit 41 to a reset state to input a low gate signal to a switching element SSR1 and a high gate signal to a switching element SSR2. When the element SSR1 is turned OFF, the element SSR2 is simultaneously turned OFF to switch the load L1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power system switching system, and particularly to a power system switching system for switching between a commercial power system and a generator power system.

[Conventional technology]

When introducing a generator into a factory, building, etc., there are two ways to operate it: one is to operate the generator independently for a dedicated load, and the other is to operate the generator by connecting it to the commercial grid. There is a parallel operation method.

[Invention tries to solve! 1! Problem] The generator independent operation method has the advantage that the load dedicated to the generator is fixed, so it can be realized with a simple system in terms of protection and security. It is not possible to utilize 100% of the generator capacity, resulting in a low generator utilization rate.Also, when the load is switched to the commercial grid, the power supply is temporarily stopped, making it impossible to connect important loads.

On the other hand, in parallel operation with the commercial grid, in response to a sudden increase in load, the power is supplied from the commercial grid, so 10% of the generator output
0% can be used effectively, and even if the generator is disconnected from the grid due to generator trouble, it has the advantage of being able to supply power to the load, but on the other hand, backflow from the generator to the commercial grid
In order to prevent back pressure, it is necessary to construct various protection systems for security reasons, and there are also drawbacks such as the need to consult with and obtain permission from the electric power company.

An object of the present invention is to provide a power system switching system that eliminates the drawbacks of the conventional operating methods described above and allows more efficient and safe generator operation.

[Means to solve the problem]

The present invention provides a power system switching system that switches power supply to a plurality of loads between a commercial power system and a generator power system, in which a first semiconductor is provided between each load and the commercial power system. a switching element, a second semiconductor switching element provided between each load and the generator power supply system, and a flip-flop circuit that turns on one of the first and second semiconductor switching elements and turns off the other at the same time. It is characterized by having a control device having a power supply system, and switching between a commercial power supply system and a generator power supply system without momentary interruption.

According to the present invention, the control device includes: a zero-cross switching command section that drives a flip-flop circuit so as to switch the power system at the zero-crossing timing of the power waveform; and an arbitrary phase priority switching command unit that drives the flip-flop circuit at arbitrary phase timing.

Further, according to the present invention, the control device includes a first calculation unit that selects the most appropriate switching load and instructs the zero-cross switching command unit; and a power generation unit that predicts and detects a generator failure and instructs the zero-cross switching command unit. A machine accident prediction detection unit, a second calculation unit that detects a sudden increase in load power, selects which load it is, and instructs the arbitrary phase priority switching command unit, and detects a serious generator accident. and a generator serious accident detection section that instructs the arbitrary phase priority switching command section.

[Effect]

To construct the power system switching system of the present invention, (1)
In order to ensure the safety of electric power company distribution systems and eliminate the need to construct security protection systems, it is necessary to prevent generators from running in parallel with the commercial grid; (2) to increase the efficiency of generator utilization; , Start-up of peak loads such as induction motors is performed on the commercial power system side, and switch to the generator power system side after steady operation; (3) There is no momentary interruption when switching between the commercial power system and the generator power system for the load. Conditions such as ensuring that

In order to ensure these conditions, a semiconductor switching element is used to connect the load to a commercial system bus (hereinafter referred to as A bus) through the semiconductor switching element, and a generator bus (hereinafter referred to as A bus) through another semiconductor switching element. , B
(called busbar). By turning on and off these semiconductor switching elements, the connection of the load to the A bus or the B bus is switched. At this time, it is necessary to turn on one switching element and simultaneously turn off the other switching element so that the power supply to the load is uninterrupted. For this purpose, it is preferable to use a flip-flop circuit as a gate signal supply circuit to the semiconductor switching element.

Of course, when switching the bus to the load, it is assumed that the voltage values and phases of the A bus and B bus are synchronized.

It is stable and safe to set the bus bar switching timing to the zero cross of the power supply waveform. However, in the event of an instantaneous power increase or generator failure, it is necessary to instantaneously switch at any phase other than the zero cross.

Therefore, the control device according to the present invention has the following functions.

(1) Make the voltage values of the A bus and B bus the same and phase synchronize! and issues a confirmation command.

(2) Detect the generator capacity/generator output/power consumption of each load/predicted power demand, etc., and select the load to be switched to the A bus and B bus. That is, the optimum load to be switched is selected and a switching command is issued.

(3) By detecting instantaneous voltage drops, instantaneous phase changes, instantaneous power changes, etc., a peak load current caused by, for example, an induction motor is detected, and a switching command from the B bus to the A bus is issued.

(4) An abnormality in the generator is detected while the generator still has the ability to supply power until it breaks down, and a command to switch from the B bus to the A bus is issued.

(5) Control the supply of gate signals from the flip-flop circuit to the semiconductor switching element.

According to the power supply system switching system of the present invention that includes such a control device, an appropriate load can be detected from among the loads set in advance so as to enable coarse and fine adjustment, and the connection to the A bus or the B bus can be switched. The load is set to generator capacity 1 by
It is possible to set the burden value to 00% or around an arbitrarily set burden value.

〔Example〕

Next, examples of the present invention will be described.

FIG. 1 shows the basic configuration of an embodiment of the present invention.

Note that this embodiment shows an example of a single-phase case, where the bus of the commercial power system is the A bus, and the bus of the generator power system connected to the generator 1 is the B bus.

The load L0 is connected to the A bus, and the loads Lr, Lt, Ls.

L4 is, for example, gate turn-off scissor (GTo)
A semiconductor switching element 5SRI that can be
It is connected to bus A via SR3, 5SR5, and 5SR7.

These loads L1. Lt, Ls, and La are also switching elements 5SR2, 5SR4, 5SR6,
It is connected to the B bus via SS8.

The gates of these switching elements 5SRI to 5SRI to 8 are controlled by the control device 2 to turn on and turn off.

At the power receiving point of the commercial grid, a demand monitoring device (DM) 5 is connected via a potential transformer (PCT) 3 and a wattmeter (kWH) 4.
is installed. This demand monitoring device monitors the power demand and predicted power demand at the power receiving point, and sends the monitoring results to the control device 2.

The generator (SG) 1 is rotated by an engine (Eng) 6, and the rotation of the engine is controlled by a speed governor (Gov) 7. The generator 1 and the engine 6 are provided with various sensors at various parts in order to predict generator failure as described later, and detection signals from these sensors are sent to the control device 2.

A synchronous regulator (SY) 8 is installed between the A bus and the B bus, and this synchronous regulator controls the speed governor 7.

A generated power detection transformer CT is installed on the output side of the generator 1, and load power detection transformers CT+, CTt, CTC, and C are installed on the input sides of the loads L+, Lz, Ls, and La.
T4 are installed and these transformers are connected to the control device 2.

Further, the voltages of the A bus and the B bus are input to the control device 2, and the voltage value and phase are detected by the control device.

FIG. 2 is a functional block diagram of the control device 20.

Note that the loads Lz, Ls, and L4 are not illustrated.

The demand monitoring unit 11 monitors the power demand and predicted power demand at the power receiving point based on information from the demand monitoring bag W5 of the commercial power supply system.

The instantaneous voltage drop detection unit 12 detects the instantaneous voltage drop (Δ
V/Δt) is detected.

The synchronization confirmation unit 13 checks the synchronization (voltage value and phase) between the A83: line and the B bus.

The generator failure ovary detection unit 14 detects, for example, an increase in cooling water temperature, a decrease in lubricating oil pressure, an increase in stator winding temperature, an increase in bearing temperature, and exhaust gas, using various sensors provided in each part of the generator l and engine 6. Temperature abnormalities, low fuel tank levels, etc. are detected, and failures of the generator 1 and engine 6 are predicted and detected in advance before the generator is shut down due to an accident.

The generator serious accident detection unit 15 captures the opening/closing information of the operating contacts of the protective relay necessary for disconnecting the generator 1 due to an accident.
A serious generator accident is detected before the circuit breaker shuts off the accident.

The generated power detection unit 16 monitors the current generated power using the voltage and current from the generated power detection transformer CT.

The load power detection unit 17 includes a load power detection transformer CT +
, CT z, CT I CT a due to the voltage and current from each load L In L z, L ! , L
Monitor the current consumption mills of a.

The load sudden increase detection section 18 detects a sudden increase (Δp/Δt) in the load connected to the B bus.The device failure detection section 19 detects an abnormality in the equipment, an electrical abnormality in the load system, and the like.

The generator capacity setting section 20 is for setting the capacity of the generator 1 in advance.

The switching load selection calculation unit 21 calculates the generator capacity set by the generator capacity setting unit 20, the past hourly power consumption (can be set for the previous day, week, or month) sent from the demand monitoring unit 11, From the current generator generated power detected by the generated power detection unit 16 and the current power consumption of each load L I, L z, L x, L 4 detected by the load power detection unit 17, the optimal replacement load is determined. to sort out.

The load sudden increase detection calculation selection unit 22 includes the instantaneous voltage drop detection unit 1
The instantaneous voltage drop (ΔV/Δt) detected in step 2 and the sudden increase in load (Δp/Δt) detected by the load sudden increase detection unit 18
), a request to switch to the B bus or the A bus is issued in order to prevent the generator from losing synchronization due to a sudden increase in the power consumption of the load (large starting current of an induction motor, etc.).

The AND circuit 23 ANDs the synchronization confirmation information from the synchronization confirmation section 13 and the optimal switching load information from the switching negative selectable calculation section 21 .

The AND circuit 24 ANDs the synchronization confirmation information from the synchronization confirmation section 13 and the failure prediction information from the generator failure prediction detection section 14 .

The AND circuit 25 ANDs the synchronization confirmation information from the synchronization confirmation section 13 and the bus bar switching request information from the load sudden increase detection calculation selection section 22 .

The AND circuit 26 ANDs the synchronization confirmation information from the synchronization confirmation section 13 and the serious accident detection information from the generator serious failure detection section 15.

The OR circuit 27 performs an OR operation on the outputs of the AND circuits 23 and 24.

The OR circuit 28 performs an OR operation on the outputs of the AND circuits 25 and 26.

The zero cross switching command unit 29 is a switching load selection calculation unit 21
Alternatively, a switching command is issued in accordance with a command from the generator failure prediction detection unit 14. This switching command unit uses zero-cross switching as standard.

The arbitrary phase priority switching command 30 receives a command from the load surge detection calculation selection unit 22 or the generator serious accident detection unit 15, and gives priority to instantaneous (not waiting for the zero-crossing position but the instantaneous) rather than normal zero-crossing switching. A priority switching command is issued to switch the bus bar.

When the device failure detection section 19 detects a device abnormality, load system electrical abnormality, etc., the switching locking section 31 instructs the switching command sections 29 and 30 to disable switching, so that the switching command sections do not operate. to be locked.

The flip-flop circuit section 32 has respective loads Ll and Lm.

A pair of switching elements 5SR connected to L, ,L,
One flip-flop circuit is provided for each of 1, 2, 5 SR 3, 4, 5 SR 5, 6, and SS 7.8, and a drive circuit that drives these flip-flop circuits based on a switching command is provided.

FIG. 3 shows l pairs of switching elements 5SRI with loads.
, 2 and one flip-flop circuit, for example, RSS, which supplies gate signals to the gates of these switching elements.
The connection between the flip-flora circuit 41 and the drive circuit 42 is shown.

Next, the operation of this embodiment will be explained.

Now, the semiconductor switching elements 5SRI, 3,5°7 are turned on, and the loads are +, L, L3.
It is assumed that all L4s are connected to the A bus and are supplied with power from the commercial power supply system.

When the demand monitoring device 5 that monitors the power demand and the predicted power demand at the power receiving point determines that it is necessary to start the generator 1, it starts the generator 1.

When the generator 1 starts generating electricity, the synchronous regulator 8
is controlled to synchronize the voltage values and phases of the A bus and B bus. The voltages of the A bus and the B bus are monitored by a synchronization confirmation section 13, and when synchronization of voltage values and phases is confirmed, a synchronization confirmation signal is output. This synchronization confirmation signal is input to AND circuits 23.24.25.26. Therefore, the control device will only operate after synchronization has been established.

FIG. 4(a) shows a state in which the power waveform of the A bus (solid line) and the power waveform of the B bus (broken line) are synchronized.

The generated power of the generator 10 is monitored and detected by the generated power detection section 16 based on the voltage and current from the generated power detection transformer CT. The detected generated power is sent to the switching load selection calculation section 21.

On the other hand, the load power detection unit 17 detects each load L I, L !
, L 3゜Load power detection transformer C installed at L4
Tt, CT! , CT s, and CT a to monitor and detect the load power value of each load. The detected load power of each load is sent to the switching load selection calculation section 21.

In addition, the demand monitoring unit 11 monitors and detects the power demand and predicted power at the power receiving point based on the information from the demand monitoring device 5, and sends the detected power demand and predicted power at the power receiving point to the switching load sorting calculation unit 21. send.

The capacity of the generator 1 is input in advance to the switching load selection calculation unit 21 by the generator capacity setting unit 20 .

Now, the switching load sorting calculation unit 21 calculates, based on the various information sources mentioned above, the current power generated by the generator and its surplus power, as well as each load Ll, L! , L3° and L4 at the current time and past hourly power consumption (can be set for the previous day, week, or month), and select the most suitable load to replace. It is assumed that the load L1 is selected as a result of the selection.

The selection signal is sent to the zero-cross switching command unit 29 via the AND circuit 23 and the OR circuit 27.

The zero cross switching command unit 29 changes the load from bus A to bus B.
A switching command to switch to the bus bar is sent to the flip-flop circuit section 3.
Send to 2.

The drive circuit 42 of the flip-flop circuit section 32 switches the flip-flop circuit 41 that generates gate signals to the semiconductor switching elements 5SRI and 5SR2 from the set state to the reset state, that is, sets the R input to high and the S input to low. From Tosukoto, the σ output becomes high, the Q output becomes low, and the switching element SSR1
A low gate signal is input to the gate of the switching fi element 5SR2, and a high gate signal is input to the gate of the switching fi element 5SR2. As a result, the switching element SSR1 is turned off and the switching element 5SR2 is turned off at the same time. The timing is performed at the zero cross of the power waveform of the A bus or the B bus. It is assumed that the drive circuit 42 has a function of detecting zero crossings of the power supply waveform.

As a result of the above, the connection of the load is switched from the A bus to the B bus, and as a result, power is supplied to the load by the generator 1. Figure 4(b) shows the load.

shows the load end power supply waveform. At time t1, the A bus is switched to the B bus without any interruption.

In the above example, only the load is switched from the A bus to the B bus, but other loads may also be switched at the same time depending on the result of the comparison calculation by the switching load selection calculation unit 21. Also, due to a change in the situation, the load applied to the B bus may be changed to A.
A return to the busbar is also performed.

The operation of this embodiment in the case where the generator breaks down when the load is connected to the B bus and power is supplied from the generator 1 will be described.

After generator 1 has completely broken down, load B
Switching from the bus to the A bus causes a momentary interruption in the power supply to the load. In order to avoid this, it is necessary to detect an abnormality in the generator while generator 1 still has the ability to supply power before it breaks down, and to switch from the B bus to the A bus without momentary interruption. According to this embodiment, this is performed as follows.

That is, the generator failure prediction detection unit 15 detects an increase in cooling water temperature, a decrease in lubricant oil pressure, an increase in stator winding temperature, an increase in bearing temperature, an abnormality in exhaust gas temperature, a decrease in fuel tank level, etc. - Predictively detects engine failure before the generator is shut off due to an accident, sends the detected f8 signal to the zero-cross switching command section 29 via the AND circuit 24 and the OR circuit 27, and drives the flip-flop circuit section 32. By turning on the switching element SSR1 and turning off the switching element 5SR2, B
Performs uninterrupted switching from bus to A bus.

Next, the operation of this embodiment will be described when the load is a peak load such as an induction motor that flows a peak load current.

It is assumed that the peak load LIA (connected to the B bus bar and the peak load Ll starts up).The instantaneous voltage drop detection unit 12
By detecting the instantaneous voltage drop (ΔV/Δt) on the B bus, a sudden increase in generator load (startup of peak load) is predicted. Further, the load sudden increase detection unit 18 detects a sudden increase (Δp/Δt) in the load connected to the B bus, and detects the start-up of a peak load such as an induction motor.

The load sudden increase detection arithmetic selection circuit 22 detects the load 7. A sudden increase in power (large starting current of an induction motor, etc.) is detected, and a detection signal is sent to the arbitrary phase priority switching command section 30 via an AND circuit 25 and an OR circuit 28. In this case, bus switching is urgent, so the flip-flop circuit 31 is driven to instantaneously switch the load from the B bus to the A bus without waiting until the zero cross.

FIG. 4(c) shows the load end power supply waveform of the load Ll, in which the uninterrupted switching is performed at time 1t.

In the above example, the peak load was switched from the B bus to the A bus, but if the peak load was initially connected to the A bus, the B bus would be switched to the B bus after steady operation. You can also switch to .

From the above, it will be understood that the capacity of the generator 1 can be fully utilized.

Next, the operation of switching the load connected to the B bus to the A bus when the generator 1 suffers a serious failure will be described.

The generator serious fault detection unit 15 detects the occurrence of a serious fault in the generator 1 in advance by taking in information on opening and closing of operating contacts of a protective relay that operates a circuit breaker that shuts off the generator 1 in an accident. The detection signal is inputted to the arbitrary phase priority switching command section 30 via the AND circuit 26 and the OR circuit 28, and the load connected to the B bus is switched without interruption to the A bus in the same manner as described above.

Finally, the operation when the device failure detection section 19 detects a device abnormality, an electrical abnormality in the load system, etc. will be described.

When the device failure detection section 19 detects a device abnormality, load system electrical abnormality, etc., it sends a detection signal to the switching lock circuit section 31.

When receiving this signal, the switching lock circuit section 31 instructs the zero-cross switching command section 29 and the arbitrary phase priority switching command section 30 to be disabled, and locks these switching I command sections so that they do not operate. As a result, the control device 2 becomes inactive, making it possible to prevent a serious accident from occurring.

As explained above, in the present invention, it is a requirement that busbar switching be performed without momentary interruption, but if the load includes an induction motor, for example, as shown in FIG. 4(d), The inventors of the present application have confirmed that even if there is a half-cycle switching delay, the induction motor is burdened with power generation during this period (the portion shown by the dashed line), which is essentially the same as no interruption. If switching is to be performed at a zero-crossing timing that is delayed by a half period, a delay circuit that delays one output of the flip-flop circuit by a half period may be provided.

The above description has been made for a single-phase case, but in the case of a three-phase case, a semiconductor switching element and a flip-flop circuit are provided for each phase, and the zero-cross switching command section 29 and arbitrary phase priority switching command section 30 are configured for each phase. A switching command will be generated. In this case, the zero cross switching of each phase is 1
The phases are shifted by 20e, and the arbitrary phase switching is performed at an instant when the three phases are in the same phase.

〔Effect of the invention〕

According to the present invention, the remarkable effects listed below can be obtained.

(11) Since the commercial grid and the generator are not operated in parallel, there is no backflow or back pressure phenomenon that is a problem inherent in parallel operation. In addition, there is no need to have a meeting with the power company or obtain permission from the power company when installing a generator.

(2) By detecting an appropriate load among the loads that have been set in advance so that coarse and fine adjustment is possible, and switching the connection between the commercial power supply system and the generator power supply system, the load can be adjusted to 10% of the generator capacity.
It is possible to set it to 0% or around an arbitrarily set burden value.

(3) For peak loads such as induction motors, power is supplied from the commercial power system during startup, which requires a large current, and after steady operation, the power is switched to the generator power system, increasing the efficiency of generator usage. be able to.

(4) Since a flip-flop circuit is used, load switching between the commercial power supply system and the generator power supply system can be performed without momentary interruption. Therefore, important loads can be connected.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing an embodiment of the present invention.
FIG. 3 is a functional block diagram showing details of the control device in the illustrated embodiment; FIG. 3 is a diagram showing connections between semiconductor switching elements and flip-flop circuits; FIG. 4 is a power waveform diagram. 1... Generator 2... Control device 5... Demand monitoring device 6... Engine 7... Governor 8... Synchronous regulator 11. ... Demand monitoring section 12 ... Instantaneous voltage drop detection section 13 ... Synchronization confirmation section 14 ... Generator failure prediction detection section 15 ...
Generator serious failure detection unit 16...Generated power detection unit 17...Load power detection unit 18...Load sudden increase detection unit 19...Device failure detection unit 20... ... Generator capacity setting section 21 ... Switching load selection calculation section 22 ... Load sudden increase detection calculation selection section 23 - 26 ...
・AND circuits 27, 28...02 circuit 29...Zero cross switching command section 30...Arbitrary phase priority switching command section '31.
... Switching lock section 32 ... Flip-flop circuit section 41 ...
Flip-flop circuit 42...Drive circuit L...Load SSR...Semiconductor switching element Agent Patent attorney Yoshiyuki Iwasa Figure 4

Claims (3)

[Claims] (1) In a power system switching system that switches power supply to multiple loads between a commercial power system and a generator power system, a first semiconductor switching device is provided between each load and the commercial power system. a second semiconductor switching element provided between each load and the generator power supply system, and a flip-flop circuit that turns on one of the first and second semiconductor switching elements and simultaneously turns off the other. A power system switching system characterized by comprising a control device and switching between a commercial power system and a generator power system without momentary interruption. (2) The control device includes a zero-cross switching command section that drives the flip-flop circuit so that power system switching is performed at the zero-crossing timing of the power waveform, and an arbitrary phase timing that prioritizes power system switching over the zero-crossing timing of the power waveform. 2. The power supply system switching system according to claim 1, further comprising an arbitrary phase priority switching command unit that drives the flip-flop circuit in the manner as described above. (3) The control device includes a first calculation unit that selects the most appropriate switching load and instructs the zero-cross switching command unit, and a generator failure prediction and detection unit that predicts and detects generator failure and instructs the zero-cross switching command unit. , a second calculation unit that detects a sudden increase in the load power of the load, selects which load it is, and instructs the arbitrary phase priority switching command unit; and a second calculation unit that detects a serious generator accident and switches the arbitrary phase priority to the selected load. 3. The power system switching system according to claim 2, further comprising a generator serious accident detection section that instructs the switching command section.