GB2552303A

GB2552303A - Hybrid frequency response

Info

Publication number: GB2552303A
Application number: GB1611998.4A
Authority: GB
Inventors: Robert Linton Howe Andrew
Original assignee: LEVEL ENERGY Ltd
Current assignee: LEVEL ENERGY Ltd
Priority date: 2016-07-11
Filing date: 2016-07-11
Publication date: 2018-01-24
Also published as: GB201611998D0

Abstract

A system for providing instantaneous frequency response from batteries with a hybrid power source. A diesel generation plant 100 is equipped with batteries 5 and an invertor 4 with means for controlling power taken from diesel generators of the diesel generation plant that provides frequency response services to a grid, wherein a state of charge (SOC) of the batteries 5 is corrected using a power and energy means that is separate to electrical power provided to the grid. The state of charge trigger on the batteries may be 75% when the batteries are charging, and 25% when the batteries are discharging.

Description

(71) Applicant(s):

Level Energy Ltd

Delta Place, 27 Bath Road, Cheltenham, Gloucestershire, GL53 7TH, United Kingdom (72) Inventor(s):

Andrew Robert Linton Howe

(51) INT CL: H02J 3/32 (2006.01)
(56) Documents Cited:
GB 2540251 A	WO 2011/120435	A1
US 6487096 B1	US 5929538 A1
US 20130181519 A1 US 20040041404 A1 (58) Field of Search: INT CL H02J Other: WPI, EPODOC	US 20050006958	A1

(74) Agent and/or Address for Service:

Basck Ltd

Saxon Road, CAMBRIDGE, Cambridgeshire, CB5 8HS, United Kingdom (54) Title ofthe Invention: Hybrid frequency response

Abstract Title: Generator and battery storage for frequency response (57) A system for providing instantaneous frequency response from batteries with a hybrid power source. A diesel generation plant 100 is equipped with batteries 5 and an invertor 4 with means for controlling power taken from diesel generators ofthe diesel generation plant that provides frequency response services to a grid, wherein a state of charge (SOC) of the batteries 5 is corrected using a power and energy means that is separate to electrical power provided to the grid. The state of charge trigger on the batteries may be 75% when the batteries are charging, and 25% when the batteries are discharging.

Current meter

FIG. 1

1/1

10 17

Current meter

Diesel Augmented with Battery for Frequency Response

Adding battery storage to diesel plants to provide frequency response.

GB application GB1507982.5 (dl) describes the original concept.

This document describes features incorporated to the invention prior to submitting a tender proposal to National Grid.

Object of invention

Modification to an existing standby diesel plant to allow provision of frequency response.

Description of Invention

This description is written assuming the content of GB1507982.5 is not published. This application is to protect a commercial position and an update is to be expected.

Dl shows the generator providing DC with rectifier. In this embodiment the generator is connected to transformer 9. Additionally a load resistor is connected to battery,5. Optionally the load resistor can be provided on the ac side. The function of the load resistor is to balance the battery state of charge.

In this embodiment modelled the battery provides the fast power in both directions of response, load and generation, responding in sub 1 second to changes in frequency. Algorithms that define the response power are defined in WO2014/177264 by the same inventor.

In service, the frequency excursions can cause the battery to reach the ends of its state of charge limits SoC. In that instance hybrid power is provided by a load resistor means or generation means to correct the state of charge.

In one embodiment the state of charge trigger on threshold is set at 75% when the battery is charging or 25% discharging. The hybrid power is then removed on a second SOC threshold, for example 55% when battery had reached 75% and complimentary case, 45%. This provides hysterysis. Other algorithms with softer and differing limits/thresholds and in fact the techniques described in WO2014/177264 could be applied.

In one embodiment the hybrid power provided is an average of the response power over a period. This period is linked to the energy storage time and in one embodiment an HR filter with around 1 minute time constant was used where the hybrid power was computed from y_n = 0.9y_n_i+0.1x_n. where X.n is the response power provided by the system. Other averaging / filtering / historical techniques can be imagined. The SoC itself is an average of power.

This operation results in hybrid power being provided occasionally. By way of example the table below illustrates the hybrid power.

		MWh MWh	hours hours		Max Power
Jan-14 Feb-14	24.10% 23.80%	77.90%	lllllll ^-4.89¹		4	¹⁰	S·· 2.59	-3.38
Mar-14	23.80%	78.30%	0.408	-5.99	0.7	7.32	1	11	1.561	-3.706
Apr-14	23.80%	78.40%	1.82	-8.83	1.91	10.26	2	13	2.9	-3.328
May-14	23.30%	76.30%	0.94	-0.66	1.28	1.58	2	3	1.84	-1.19
J un-14 Jul-14	26.30% 26.20%	76% 76.50%	0 0	-1.8 -0.61	0 0	2.46 1.12	0 0	3 2	0 0	-2.09 -1.95
Aug-14	27.90%	76.20%	0	-1.49	0	2.52	0	4	0	-2.45
Sep-14	34.20%	77.20%	0	-1.81	0	2.49	0	4	0	-3.2
Oct-14	23.30%	77.20%	0.4	-2.24	0.68	2.55	1	3	1.29	-2.72
Nov-14	23.20%	76.70%	3.45	-3.44	4.46	5.23	6	7	2.6	-1.99
Dec-14	^1 77.70%	2.91	-3.57	3.9	5.48	5	9	2.39	-3.19

The following points are of note:

1. The state of charge can be kept within well-defined boundaries, good for battery life

2. The peak hybrid power is 40% lower than peak plant capacity, although this plant design will retain 75% generation capacity for TRIAD service reasons

3. Hybrid energy fuel opex costs are low, lower than the energy losses in/out the battery

4. Hybrid operating hours and number of starts are low

5. Hybrid running is linked to temporary grid time clock errors increasing consistently over hours

6. Even in narrow service, 15 minutes of full power post fault energy is available, unlike a 30 minute battery storage solution. In wide service simulation, no hybrid power was required.

7. System can provide secondary and tertiary low services beyond capacity market running times.

8. Load resistors could be replaced by aggregated load increases, but free energy is small

9. Low annual CO2 emissions from diesel generation in this operational mode. Per MW of response service, 1.6MWh or 2.5 tonnes CO2 in 21 operating hours. These are less than the CO2 arising from in/out losses of operating the battery

Other Features

Main feature is the provision of hybrid power to correct state of charge. Calculation of an appropriate power. State of charge limits that make the hybrid run intermittently. Grid synchronous clock time could also be used as a control signal, but that's an integration of frequency and is directly similar to state of charge. State of charge accounts for losses.

Actual provision of DC and AC powers has differing possibilities. Battery always DC - hybrid power can be ac, dc or even mixture of both.

Claims

Claims

1. Diesel generation plant equipped with batteries and invertor with means to control power taken from diesels that provides frequency response services, wherein state of charge is corrected with separate power and energy means to the grid electrical power.

Amendments to the Claims have been filed as follows:CLAIMS

1. A generation plant (100) equipped with batteries (5) and an invertor (4) with means for controlling power taken from generators of the generation plant that provides frequency response services to a grid,

5 wherein a state of charge (SOC) of the batteries (5) is corrected using a power and energy means that is separate to electrical power provided to the grid.
2. A generation plant (100) of claim 1, wherein the generation plant (100) is a diesel generation plant including diesel generators.

io
3. A generation plant (100) of claim 1 and 2, wherein the generation plant (100) is operable to provide a sub-1 second frequency response to the grid.

h-
4. A generation plant (100) of claim 1, 2 or 3, wherein the generation plant (100) provides a peak hybrid power that is 40% lower than a peak ^^15 plant power capacity of the generation plant (100).

i— 5. A diesel generation plant (100) of claim 1, 2, 3 or 4, wherein the ¹ generation plant (100) is operable to provide hybrid power that is an average of the response power over a period of time, wherein the period is linked to an energy storage time.

20 6. A generation plant (100) of claim 5, wherein an HR. filter with 1 minute time constant is used where the hybrid power is computed from:

y_n = 0.9y_n-i+0.1x_n Eq. 1 where

X_n is the response power provided by the generation plant (100).

25 7. A generation plant (100) of any one of claims 1 to 6, wherein a state of charge (SOC) trigger on threshold is set at 75% (of SOC) when the batteries (5) are charging, or 25% (of SOC) when the batteries (5) are discharging, wherein hybrid power is then removed on a second SOC threshold of 55% (of SOC), when the batteries (5) have reached 75% (of SOC), and a
5 complimentary case when the batteries (5) have reached 45% (of SOC), for providing hysteresis.
8. A generation plant (100) of any one of the preceding claims, wherein controlling state-of-charge (SOC) of the batteries (5) includes hysteresis.

Intellectual

Property

Office

GB1611998.4

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